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This dissertation combines field and geochemical observations and analyses with numerical modeling to understand the formation of vein-hosted Sn-W ore in the Panasqueira deposit of Portugal, which is among the ten largest worldwide. The deposit is located above a granite body that is altered by magmatic-hydrothermal fluids in its upper part (greisen). These fluids are thought to be the source of metals, but that was still under debate. The goal of this study is to determine the composition and temperature of hydrothermal fluids at Panasqueira, and with that information to construct a numerical model of the hydrothermal system. The focus is on analysis of the minerals tourmaline and white mica, which formed during mineralization and are widespread throughout the deposit. Tourmaline occurs mainly in alteration zones around mineralized veins and is less abundant in the vein margins. White mica is more widespread. It is abundant in vein margins as well as alteration zones, and also occurs in the granite greisen. The laboratory work involved in-situ microanalysis of major- and trace elements in tourmaline and white mica, and boron-isotope analysis in both minerals by secondary ion mass spectrometry (SIMS).
The boron-isotope composition of tourmaline and white mica suggests a magmatic source. Comparison of hydrothermally-altered and unaltered rocks from drill cores shows that the ore metals (W, Sn, Cu, and Zn) and As, F, Li, Rb, and Cs were introduced during the alteration. Most of these elements are also enriched in tourmaline and mica, which confirms their potential value as exploration guides to Sn-W ores elsewhere.
The thermal evolution of the hydrothermal system was estimated by B-isotope exchange thermometry and the Ti-in-quartz method. Both methods yielded similar temperatures for the early hydrothermal phase: 430° to 460°C for B-isotopes and 503° ± 24°C for Ti-in-quartz. Mineral pairs from a late fault zone yield significantly lower median temperatures of 250°C. The combined results of thermometry with variations in chemical and B-isotope composition of tourmaline and mica suggest that a similar magmatic-hydrothermal fluid was active at all stages of mineralization. Mineralization in the late stage shows the same B-isotope composition as in the main stage despite a ca. 250°C cooling, which supports a multiple injection model of magmatic-hydrothermal fluids.
Two-dimensional numerical simulations of convection in a multiphase NaCl hydrothermal system were conducted: (a) in order to test a new approach (lower dimensional elements) for flow through fractures and faults and (b) in order to identify conditions for horizontal fluid flow as observed in the flat-lying veins at Panasqueira. The results show that fluid flow over an intrusion (heat and fluid source) develops a horizontal component if there is sufficient fracture connectivity. Late, steep fault zones have been identified in the deposit area, which locally contain low-temperature Zn-Pb mineralization. The model results confirm that the presence of subvertical faults with enhanced permeability play a crucial role in the ascent of magmatic fluids to the surface and the recharge of meteoric waters. Finally, our model results suggest that recharge of meteoric fluids and mixing processes may be important at later stages, while flow of magmatic fluids dominate the early stages of the hydrothermal fluid circulation.
ATP-binding cassette (ABC) transporters are present in all kingdoms of life and enable active transport of various different molecules across biological membranes. They all share an overall architecture of two lipophilic transmembrane spanning domains (TMDs) traversing the membrane and two hydrophilic nucleotide binding domains (NBDs) usually lacking sequence identity. The multiplicity in transported molecules is accompanied by extreme diversity in TMDs. Human mitochondria harbor four ABC transporters, namely ABCB6, ABCB7, ABCB8 and ABCB10 with functional homologues in yeast and plants. Except the ones found in Rickettsiae and related bacteria mitochondrial ABC transporters are absent in bacteria. In addition to converting energy mitochondria are important platforms for biosynthesizing various cofactors as iron sulfur clusters, molybdenum cofactor (Moco) or heme. ABCB7 (Atm1 in yeast) has been shown to connect mitochondrial with cytosolic iron sulfur cluster assembly by exporting a yet unknown sulfur containing molecule. In addition, TMDs of Atm1 display a glutathione binding pocket accessible from the matrix which has been identified in all ABCB7-like transporters and also exists in a bacterial ABC transporter homologue of Atm1 in Novosphingobium aromaticivorans. In addition, ATM3, a plant mitochondrial homologous ABC transporter to human ABCB7, has been associated with biosynthesizing Moco.
In this study we used the α-proteobacterium Rhodobacter capsulatus as a model organism to characterize mitochondrial ABC transporter homologues. R. capsulatus contains two homologues to mitochondrial ABC transporters with the corresponding gene loci rcc03139 and rcc02305. They share 38 to 47 % sequence identities to human mitochondrial ABC transporters ABCB8/ABCB10 and ABCB7/ABCB6, respectively. We created interposon mutants lacking either rcc03139 or rcc02305, analyzed the physiological effects on R. capsulatus and compared the findings especially to eukaryotic deletion studies. A viable bacterial double mutant strain lacking both mitochondrial ABC transporters was constructed to investigate possible overlapping functions. Both R. capsulatus single mutants showed a severe accumulation of intracellular reactive oxygen species (ROS) in comparison to ∆nifDK which revealed to be additive in the double mutant. In the proteome of ∆rcc03139I abundancies of tetrapyrrole related proteins were significantly increased in comparison to the proteome of parental strain, which was further validated by reduced amounts of tetrapyrrole intermediates in ∆rcc03139. In contrast, in ∆rcc02305I total glutathione (GSH) was elevated when endogenous GSH biosynthesis was inhibited. In conjunction with proteomic studies we uncovered misbalanced sulfur distribution in ∆rcc02305I. Furthermore, strains lacking Rcc02305 accumulated cyclic pyranopterin monophosphate (cPMP), an intermediate of Moco biosynthesis, as it was already shown for the deletion strain of the eukaryotic counterpart ATM3 in plants. In contrast single mutant strain Δrcc03139I neither accumulated cPMP nor glutathione.
Bioinformatic analysis of the amino acid sequence of Rcc02305 revealed a pyridoxal 5´phosphate (PLP) binding site which overlaps with Walker A within the NBDs of Rcc02305 and other ABCB7-like transporters. The PLP cofactor is well studied in C-DES (L-cysteine/cystine lyase from Synechocystis) for persulfide production and in L-cysteine desulfurases such as IscS and NFS1 for its role in formation of protein-bound persulfides. Based on our findings we are able to propose a new modality for the transport of the sulfur containing molecule: first of all, the transporter produces a highly reactive persulfide which is then subsequently trapped by glutathione polysulfide, already bound within the binding pocket in TMDs. Walker A becomes accessible for ATP and after hydrolysis the mixed polysulfide is released.
Based on our studies we are convinced that both mitochondrial ABC transporter homologues fulfil distinct roles in R. capsulatus: Rcc02305 is a representative of Atm1/ABCB7-like transporters and important for proper sulfur distribution by exporting persulfides. In contrast Rcc03139 is a representative of ABCB6/ABCB10 related transporters and involved in biosynthesizing tetrapyrroles.
The natural abundance of Coiled Coil (CC) motifs in cytoskeleton and extracellular matrix proteins suggests that CCs play an important role as passive (structural) and active (regulatory) mechanical building blocks. CCs are self-assembled superhelical structures consisting of 2-7 α-helices. Self-assembly is driven by hydrophobic and ionic interactions, while the helix propensity of the individual helices contributes additional stability to the structure. As a direct result of this simple sequence-structure relationship, CCs serve as templates for protein design and sequences with a pre-defined thermodynamic stability have been synthesized de novo. Despite this quickly increasing knowledge and the vast number of possible CC applications, the mechanical function of CCs has been largely overlooked and little is known about how different CC design parameters determine the mechanical stability of CCs. Once available, this knowledge will open up new applications for CCs as nanomechanical building blocks, e.g. in biomaterials and nanobiotechnology.
With the goal of shedding light on the sequence-structure-mechanics relationship of CCs, a well-characterized heterodimeric CC was utilized as a model system. The sequence of this model system was systematically modified to investigate how different design parameters affect the CC response when the force is applied to opposing termini in a shear geometry or separated in a zipper-like fashion from the same termini (unzip geometry). The force was applied using an atomic force microscope set-up and dynamic single-molecule force spectroscopy was performed to determine the rupture forces and energy landscape properties of the CC heterodimers under study. Using force as a denaturant, CC chain separation is initiated by helix uncoiling from the force application points. In the shear geometry, this allows uncoiling-assisted sliding parallel to the force vector or dissociation perpendicular to the force vector. Both competing processes involve the opening of stabilizing hydrophobic (and ionic) interactions. Also in the unzip geometry, helix uncoiling precedes the rupture of hydrophobic contacts.
In a first series of experiments, the focus was placed on canonical modifications in the hydrophobic core and the helix propensity. Using the shear geometry, it was shown that both a reduced core packing and helix propensity lower the thermodynamic and mechanical stability of the CC; however, with different effects on the energy landscape of the system. A less tightly packed hydrophobic core increases the distance to the transition state, with only a small effect on the barrier height. This originates from a more dynamic and less tightly packed core, which provides more degrees of freedom to respond to the applied force in the direction of the force vector. In contrast, a reduced helix propensity decreases both the distance to the transition state and the barrier height. The helices are ‘easier’ to unfold and the remaining structure is less thermodynamically stable so that dissociation perpendicular to the force axis can occur at smaller deformations.
Having elucidated how canonical sequence modifications influence CC mechanics, the pulling geometry was investigated in the next step. Using one and the same sequence, the force application points were exchanged and two different shear and one unzipping geometry were compared. It was shown that the pulling geometry determines the mechanical stability of the CC. Different rupture forces were observed in the different shear as well as in the unzipping geometries, suggesting that chain separation follows different pathways on the energy landscape. Whereas the difference between CC shearing and unzipping was anticipated and has also been observed for other biological structures, the observed difference for the two shear geometries was less expected. It can be explained with the structural asymmetry of the CC heterodimer. It is proposed that the direction of the α-helices, the different local helix propensities and the position of a polar asparagine in the hydrophobic core are responsible for the observed difference in the chain separation pathways. In combination, these factors are considered to influence the interplay between processes parallel and perpendicular to the force axis.
To obtain more detailed insights into the role of helix stability, helical turns were reinforced locally using artificial constraints in the form of covalent and dynamic ‘staples’. A covalent staple bridges to adjacent helical turns, thus protecting them against uncoiling. The staple was inserted directly at the point of force application in one helix or in the same terminus of the other helix, which did not experience the force directly. It was shown that preventing helix uncoiling at the point of force application reduces the distance to the transition state while slightly increasing the barrier height. This confirms that helix uncoiling is critically important for CC chain separation. When inserted into the second helix, this stabilizing effect is transferred across the hydrophobic core and protects the force-loaded turns against uncoiling. If both helices were stapled, no additional increase in mechanical stability was observed. When replacing the covalent staple with a dynamic metal-coordination bond, a smaller decrease in the distance to the transition was observed, suggesting that the staple opens up while the CC is under load.
Using fluorinated amino acids as another type of non-natural modification, it was investigated how the enhanced hydrophobicity and the altered packing at the interface influences CC mechanics. The fluorinated amino acid was inserted into one central heptad of one or both α-helices. It was shown that this substitution destabilized the CC thermodynamically and mechanically. Specifically, the barrier height was decreased and the distance to the transition state increased. This suggests that a possible stabilizing effect of the increased hydrophobicity is overruled by a disturbed packing, which originates from a bad fit of the fluorinated amino acid into the local environment. This in turn increases the flexibility at the interface, as also observed for the hydrophobic core substitution described above. In combination, this confirms that the arrangement of the hydrophobic side chains is an additional crucial factor determining the mechanical stability of CCs.
In conclusion, this work shows that knowledge of the thermodynamic stability alone is not sufficient to predict the mechanical stability of CCs. It is the interplay between helix propensity and hydrophobic core packing that defines the sequence-structure-mechanics relationship. In combination, both parameters determine the relative contribution of processes parallel and perpendicular to the force axis, i.e. helix uncoiling and uncoiling-assisted sliding as well as dissociation. This new mechanistic knowledge provides insight into the mechanical function of CCs in tissues and opens up the road for designing CCs with pre-defined mechanical properties. The library of mechanically characterized CCs developed in this work is a powerful starting point for a wide spectrum of applications, ranging from molecular force sensors to mechanosensitive crosslinks in protein nanostructures and synthetic extracellular matrix mimics.
A new micro/mesoporous hybrid clay nanocomposite prepared from kaolinite clay, Carica papaya seeds, and ZnCl2 via calcination in an inert atmosphere is presented. Regardless of the synthesis temperature, the specific surface area of the nanocomposite material is between ≈150 and 300 m2/g. The material contains both micro- and mesopores in roughly equal amounts. X-ray diffraction, infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy suggest the formation of several new bonds in the materials upon reaction of the precursors, thus confirming the formation of a new hybrid material. Thermogravimetric analysis/differential thermal analysis and elemental analysis confirm the presence of carbonaceous matter. The new composite is stable up to 900 °C and is an efficient adsorbent for the removal of a water micropollutant, 4-nitrophenol, and a pathogen, E. coli, from an aqueous medium, suggesting applications in water remediation are feasible.
Synchronization – the adjustment of rhythms among coupled self-oscillatory systems – is a fascinating dynamical phenomenon found in many biological, social, and technical systems.
The present thesis deals with synchronization in finite ensembles of weakly coupled self-sustained oscillators with distributed frequencies.
The standard model for the description of this collective phenomenon is the Kuramoto model – partly due to its analytical tractability in the thermodynamic limit of infinitely many oscillators. Similar to a phase transition in the thermodynamic limit, an order parameter indicates the transition from incoherence to a partially synchronized state. In the latter, a part of the oscillators rotates at a common frequency. In the finite case, fluctuations occur, originating from the quenched noise of the finite natural frequency sample.
We study intermediate ensembles of a few hundred oscillators in which fluctuations are comparably strong but which also allow for a comparison to frequency distributions in the infinite limit.
First, we define an alternative order parameter for the indication of a collective mode in the finite case. Then we test the dependence of the degree of synchronization and the mean rotation frequency of the collective mode on different characteristics for different coupling strengths.
We find, first numerically, that the degree of synchronization depends strongly on the form (quantified by kurtosis) of the natural frequency sample and the rotation frequency of the collective mode depends on the asymmetry (quantified by skewness) of the sample. Both findings are verified in the infinite limit.
With these findings, we better understand and generalize observations of other authors. A bit aside of the general line of thoughts, we find an analytical expression for the volume contraction in phase space.
The second part of this thesis concentrates on an ordering effect of the finite-size fluctuations. In the infinite limit, the oscillators are separated into coherent and incoherent thus ordered and disordered oscillators. In finite ensembles, finite-size fluctuations can generate additional order among the asynchronous oscillators. The basic principle – noise-induced synchronization – is known from several recent papers. Among coupled oscillators, phases are pushed together by the order parameter fluctuations, as we on the one hand show directly and on the other hand quantify with a synchronization measure from directed statistics between pairs of passive oscillators.
We determine the dependence of this synchronization measure from the ratio of pairwise natural frequency difference and variance of the order parameter fluctuations. We find a good agreement with a simple analytical model, in which we replace the deterministic fluctuations of the order parameter by white noise.
Organic semiconductors are a promising class of materials. Their special properties are the particularly good absorption, low weight and easy processing into thin films. Therefore, intense research has been devoted to the realization of thin film organic solar cells (OPVs). Because of the low dielectric constant of organic semiconductors, primary excitations (excitons) are strongly bound and a type II heterojunction needs to be introduced to split these excitations into free charges. Therefore, most organic solar cells consist of at least an electron donor and electron acceptor material. For such donor acceptor systems mainly three states are relevant; the photoexcited exciton on the donor or acceptor material, the charge transfer state at the donor-acceptor interface and the charge separated state of a free electron and hole. The interplay between these states significantly determines the efficiency of organic solar cells. Due to the high absorption and the low charge carrier mobilities, the active layers are usually thin but also, exciton dissociation and free charge formation proceeds rapidely, which makes the study of carrier dynamics highly challenging.
Therefore, the focus of this work was first to install new experimental setups for the investigation of the charge carrier dynamics in complete devices with superior sensitivity and time resolution and, second, to apply these methods to prototypical photovoltaic materials to address specific questions in the field of organic and hybrid photovoltaics.
Regarding the first goal, a new setup combining transient absorption spectroscopy (TAS) and time delayed collection field (TDCF) was designed and installed in Potsdam. An important part of this work concerned the improvement of the electronic components with respect to time resolution and sensitivity. To this end, a highly sensitive amplifier for driving and detecting the device response in TDCF was developed. This system was then applied to selected organic and hybrid model systems with a particular focus on the understanding of the loss mechanisms that limit the fill factor and short circuit current of organic solar cells.
The first model system was a hybrid photovoltaic material comprising inorganic quantum dots decorated with organic ligands. Measurements with TDCF revealed fast free carrier recombination, in part assisted by traps, while bias-assisted charge extraction measurements showed high mobility. The measured parameters then served as input for a successful description of the device performance with an analytical model.
With a further improvement of the instrumentation, a second topic was the detailed analysis of non-geminate recombination in a disordered polymer:fullerene blend where an important question was the effect of disorder on the carrier dynamics. The measurements revealed that early time highly mobile charges undergo fast non-geminate recombination at the contacts, causing an apparent field dependence of free charge generation in TDCF experiments if not conducted properly. On the other hand, recombination the later time scale was determined by dispersive recombination in the bulk of the active layer, showing the characteristics of carrier dynamics in an exponential density of state distribution. Importantly, the comparison with steady state recombination data suggested a very weak impact of non-thermalized carriers on the recombination properties of the solar cells under application relevant illumination conditions.
Finally, temperature and field dependent studies of free charge generation were performed on three donor-acceptor combinations, with two donor polymers of the same material family blended with two different fullerene acceptor molecules. These particular material combinations were chosen to analyze the influence of the energetic and morphology of the blend on the efficiency of charge generation. To this end, activation energies for photocurrent generation were accurately determined for a wide range of excitation energies. The results prove that the formation of free charge is via thermalized charge transfer states and does not involve hot exciton splitting. Surprisingly, activation energies were of the order of thermal energy at room temperature. This led to the important conclusion that organic solar cells perform well not because of predominate high energy pathways but because the thermalized CT states are weakly bound. In addition, a model is introduced to interconnect the dissociation efficiency of the charge transfer state with its recombination observable with photoluminescence, which rules out a previously proposed two-pool model for free charge formation and recombination. Finally, based on the results, proposals for the further development of organic solar cells are formulated.
On a planetary scale human populations need to adapt to both socio-economic and environmental problems amidst rapid global change. This holds true for coupled human-environment (socio-ecological) systems in rural and urban settings alike. Two examples are drylands and urban coasts. Such socio-ecological systems have a global distribution. Therefore, advancing the knowledge base for identifying socio-ecological adaptation needs with local vulnerability assessments alone is infeasible: The systems cover vast areas, while funding, time, and human resources for local assessments are limited. They are lacking in low an middle-income countries (LICs and MICs) in particular.
But places in a specific socio-ecological system are not only unique and complex – they also exhibit similarities. A global patchwork of local rural drylands vulnerability assessments of human populations to socio-ecological and environmental problems has already been reduced to a limited number of problem structures, which typically cause vulnerability. However, the question arises whether this is also possible in urban socio-ecological systems. The question also arises whether these typologies provide added value in research beyond global change. Finally, the methodology employed for drylands needs refining and standardizing to increase its uptake in the scientific community. In this dissertation, I set out to fill these three gaps in research.
The geographical focus in my dissertation is on LICs and MICs, which generally have lower capacities to adapt, and greater adaptation needs, regarding rapid global change. Using a spatially explicit indicator-based methodology, I combine geospatial and clustering methods to identify typical configurations of key factors in case studies causing vulnerability to human populations in two specific socio-ecological systems. Then I use statistical and analytical methods to interpret and appraise both the typical configurations and the global typologies they constitute.
First, I improve the indicator-based methodology and then reanalyze typical global problem structures of socio-ecological drylands vulnerability with seven indicator datasets. The reanalysis confirms the key tenets and produces a more realistic and nuanced typology of eight spatially explicit problem structures, or vulnerability profiles: Two new profiles with typically high natural resource endowment emerge, in which overpopulation has led to medium or high soil erosion. Second, I determine whether the new drylands typology and its socio-ecological vulnerability concept advance a thematically linked scientific debate in human security studies: what drives violent conflict in drylands? The typology is a much better predictor for conflict distribution and incidence in drylands than regression models typically used in peace research. Third, I analyze global problem structures typically causing vulnerability in an urban socio-ecological system - the rapidly urbanizing coastal fringe (RUCF) – with eleven indicator datasets. The RUCF also shows a robust typology, and its seven profiles show huge asymmetries in vulnerability and adaptive capacity. The fastest population increase, lowest income, most ineffective governments, most prevalent poverty, and lowest adaptive capacity are all typically stacked in two profiles in LICs. This shows that beyond local case studies tropical cyclones and/or coastal flooding are neither stalling rapid population growth, nor urban expansion, in the RUCF. I propose entry points for scaling up successful vulnerability reduction strategies in coastal cities within the same vulnerability profile.
This dissertation shows that patchworks of local vulnerability assessments can be generalized to structure global socio-ecological vulnerabilities in both rural and urban socio-ecological systems according to typical problems. In terms of climate-related extreme events in the RUCF, conflicting problem structures and means to deal with them are threatening to widen the development gap between LICs and high-income countries unless successful vulnerability reduction measures are comprehensively scaled up. The explanatory power for human security in drylands warrants further applications of the methodology beyond global environmental change research in the future. Thus, analyzing spatially explicit global typologies of socio-ecological vulnerability is a useful complement to local assessments: The typologies provide entry points for where to consider which generic measures to reduce typical problem structures – including the countless places without local assessments. This can save limited time and financial resources for adaptation under rapid global change.
The unprecedented increase in atmospheric concentrations of carbon dioxide (CO2) and other greenhouse gases (GHG) by anthropogenic activities since the Industrial Revolution impacts on various earth system processes, commonly referred to as `climate change´ (CC). CC faces aquatic ecosystems with extreme abiotic perturbations that potentially alter the interrelations between functional autotrophic and heterotrophic plankton groups. These relations, however, modulate biogeochemical cycling and mediate the functioning of aquatic ecosystems as C sources or sinks to the atmosphere. The aim of this thesis was therefore to investigate how different aspects of CC influence community composition and functioning of pelagic heterotrophic bacteria. These organisms constitute a major component of biogeochemical cycling and largely determine the balance between autotrophic and heterotrophic processes.
Due to the vast amount of potential CC impacts, this thesis focuses on the following two aspects: (1) Increased exchange of CO2 across the atmosphere-water interface and reaction of CO2 with seawater leads to profound shifts in seawater carbonate chemistry, commonly termed as `ocean acidification´ (OA), with consequences for organism physiology and the availability of dissolved inorganic carbon (DIC) in seawater. (2) The increase in atmospheric GHG concentration impacts on the efficiency with which the Earth cools to space, affecting global surface temperature and climate. With ongoing CC, shifts in frequency and severity of episodic weather events, such as storms, are expected that in particular might affect lake ecosystems by disrupting thermal summer stratification. Both aspects of CC were studied at the ecosystem-level in large-volume mesocosm experiments by using the Kiel Off-shore Mesocosms for Future Ocean Simulations (KOSMOS) deployed at different coastal marine locations, and the LakeLab facility in Lake Stechlin.
We evaluated the impact of OA on heterotrophic bacterial metabolism in a brackish coastal ecosystem during low-nutrient summer months in the Baltic Sea. There are several in situ experiments that already assessed potential OA-induced changes in natural plankton communities at diverse spatial and seasonal conditions. However, most studies were performed at high phytoplankton biomass conditions, partly provoked by nutrient amendments. Our study highlights potential OA effects at low-nutrient conditions that are representative for most parts of the ocean and of particular interest in current OA research. The results suggest that during extended periods at low-nutrient concentrations, increasing pCO2 levels indirectly impact the growth balance of heterotrophic bacteria via trophic bacteria-phytoplankton interactions and shift the ecosystem to a more autotrophic system.
Further work investigated how OA affects heterotrophic bacterial dissolved organic matter (DOM) transformation in two mesocsom studies, performed at different nutrient conditions. We observed similar succession patterns for individual compound pools during a phytoplankton bloom and subsequent accumulation of these compounds irrespective of the pCO2 treatment. Our results indicate that OA-induced changes in the dynamics of bacterial DOM transformation and potential impacts on DOM quality are unlikely. In addition, there have been no indications that in dependence of nutrient conditions, different amounts of photosynthetic organic matter are channelled into the more recalcitrant DOM pool. This provides novel insights into the general dynamics of the marine DOM pool.
A fourth enclosure experiment in oligo-mesotrophic Lake Stechlin assessed the impact of a severe summer storm on lake bacterial communities during thermal stratification by artificially mixing. Mixing disrupted and lowered the thermocline, increasing the upper mixed layer and substantially changed water physical-chemical variables. Deep water entrainment and associated changes in water physical-chemical variables significantly affected relative bacterial abundances for about one week. Afterwards a pronounced cyanobacterial bloom developed in response to mixing which affected community assembly of heterotrophic bacteria. Colonization and mineralization of senescent phytoplankton cells by heterotrophic bacteria largely determined C-sequestration to the sediment. About six weeks after mixing, bacterial communities and measured activity parameters converged to control conditions. As such, summer storms have the potential to affect bacterial communities for a prolonged period during summer stratification. The results highlight effects on community assembly and heterotrophic bacterial metabolism that are associated to entrainment of deep water into the mixed water layer and assess consequences of an episodic disturbance event for the coupling between bacterial metabolism and autochthonous DOM production in large volume clear-water lakes.
Altogether, this doctoral thesis reveales substantial sensitivities of heterotrophic bacterial metabolism and community structure in response to OA and a simulated summer storm event, which should be considered when assessing the impact of climate change on marine and lake ecosystems.
Optical flow models as an open benchmark for radar-based precipitation nowcasting (rainymotion v0.1)
(2019)
Quantitative precipitation nowcasting (QPN) has become an essential technique in various application contexts, such as early warning or urban sewage control. A common heuristic prediction approach is to track the motion of precipitation features from a sequence of weather radar images and then to displace the precipitation field to the imminent future (minutes to hours) based on that motion, assuming that the intensity of the features remains constant (“Lagrangian persistence”). In that context, “optical flow” has become one of the most popular tracking techniques. Yet the present landscape of computational QPN models still struggles with producing open software implementations. Focusing on this gap, we have developed and extensively benchmarked a stack of models based on different optical flow algorithms for the tracking step and a set of parsimonious extrapolation procedures based on image warping and advection. We demonstrate that these models provide skillful predictions comparable with or even superior to state-of-the-art operational software. Our software library (“rainymotion”) for precipitation nowcasting is written in the Python programming language and openly available at GitHub (https://github.com/hydrogo/rainymotion, Ayzel et al., 2019). That way, the library may serve as a tool for providing fast, free, and transparent solutions that could serve as a benchmark for further model development and hypothesis testing – a benchmark that is far more advanced than the conventional benchmark of Eulerian persistence commonly used in QPN verification experiments.
Optical flow models as an open benchmark for radar-based precipitation nowcasting (rainymotion v0.1)
(2019)
Quantitative precipitation nowcasting (QPN) has become an essential technique in various application contexts, such as early warning or urban sewage control. A common heuristic prediction approach is to track the motion of precipitation features from a sequence of weather radar images and then to displace the precipitation field to the imminent future (minutes to hours) based on that motion, assuming that the intensity of the features remains constant (“Lagrangian persistence”). In that context, “optical flow” has become one of the most popular tracking techniques. Yet the present landscape of computational QPN models still struggles with producing open software implementations. Focusing on this gap, we have developed and extensively benchmarked a stack of models based on different optical flow algorithms for the tracking step and a set of parsimonious extrapolation procedures based on image warping and advection. We demonstrate that these models provide skillful predictions comparable with or even superior to state-of-the-art operational software. Our software library (“rainymotion”) for precipitation nowcasting is written in the Python programming language and openly available at GitHub (https://github.com/hydrogo/rainymotion, Ayzel et al., 2019). That way, the library may serve as a tool for providing fast, free, and transparent solutions that could serve as a benchmark for further model development and hypothesis testing – a benchmark that is far more advanced than the conventional benchmark of Eulerian persistence commonly used in QPN verification experiments.
Simulating the impact of herbicide drift exposure on non-target terrestrial plant communities
(2019)
In Europe, almost half of the terrestrial landscape is used for agriculture. Thus, semi-natural habitats such as field margins are substantial for maintaining diversity in intensively managed farmlands. However, plants located at field margins are threatened by agricultural practices such as the application of pesticides within the fields. Pesticides are chemicals developed to control for undesired species within agricultural fields to enhance yields. The use of pesticides implies, however, effects on non-target organisms within and outside of the agricultural fields. Non-target organisms are organisms not intended to be sprayed or controlled for. For example, plants occurring in field margins are not intended to be sprayed, however, can be impaired due to herbicide drift exposure. The authorization of plant protection products such as herbicides requires risk assessments to ensure that the application of the product has no unacceptable effects on the environment. For non-target terrestrial plants (NTTPs), the risk assessment is based on standardized greenhouse studies on plant individual level. To account for the protection of plant populations and communities under realistic field conditions, i.e. extrapolating from greenhouse studies to field conditions and from individual-level to community-level, assessment factors are applied. However, recent studies question the current risk assessment scheme to meet the specific protection goals for non-target terrestrial plants as suggested by the European Food Safety Authority (EFSA). There is a need to clarify the gaps of the current risk assessment and to include suitable higher tier options in the upcoming guidance document for non-target terrestrial plants.
In my thesis, I studied the impact of herbicide drift exposure on NTTP communities using a mechanistic modelling approach. I addressed main gaps and uncertainties of the current risk assessment and finally suggested this modelling approach as a novel higher tier option in future risk assessments. Specifically, I extended the plant community model IBC-grass (Individual-based community model for grasslands) to reflect herbicide impacts on plant individuals. In the first study, I compared model predictions of short-term herbicide impacts on artificial plant communities with empirical data. I demonstrated the capability of the model to realistically reflect herbicide impacts. In the second study, I addressed the research question whether or not reproductive endpoints need to be included in future risk assessments to protect plant populations and communities. I compared the consequences of theoretical herbicide impacts on different plant attributes for long-term plant population dynamics in the community context. I concluded that reproductive endpoints only need to be considered if the herbicide effect is assumed to be very high. The endpoints measured in the current vegetative vigour and seedling emergence studies had high impacts for the dynamic of plant populations and communities already at lower effect intensities. Finally, the third study analysed long-term impacts of herbicide application for three different plant communities. This study highlighted the suitability of the modelling approach to simulate different communities and thus detecting sensitive environmental conditions.
Overall, my thesis demonstrates the suitability of mechanistic modelling approaches to be used as higher tier options for risk assessments. Specifically, IBC-grass can incorporate available individual-level effect data of standardized greenhouse experiments to extrapolate to community-level under various environmental conditions. Thus, future risk assessments can be improved by detecting sensitive scenarios and including worst-case impacts on non-target plant communities.
Understanding and quantifying total economic impacts of flood events is essential for flood risk management and adaptation planning. Yet, detailed estimations of joint direct and indirect flood-induced economic impacts are rare. In this study an innovative modeling procedure for the joint assessment of short-term direct and indirect economic flood impacts is introduced. The procedure is applied to 19 economic sectors in eight federal states of Germany after the flood events in 2013. The assessment of the direct economic impacts is object-based and considers uncertainties associated with the hazard, the exposed objects and their vulnerability. The direct economic impacts are then coupled to a supply-side Input-Output-Model to estimate the indirect economic impacts. The procedure provides distributions of direct and indirect economic impacts which capture the associated uncertainties. The distributions of the direct economic impacts in the federal states are plausible when compared to reported values. The ratio between indirect and direct economic impacts shows that the sectors Manufacturing, Financial and Insurance activities suffered the most from indirect economic impacts. These ratios also indicate that indirect economic impacts can be almost as high as direct economic impacts. They differ strongly between the economic sectors indicating that the application of a single factor as a proxy for the indirect impacts of all economic sectors is not appropriate.
Understanding and quantifying total economic impacts of flood events is essential for flood risk management and adaptation planning. Yet, detailed estimations of joint direct and indirect flood-induced economic impacts are rare. In this study an innovative modeling procedure for the joint assessment of short-term direct and indirect economic flood impacts is introduced. The procedure is applied to 19 economic sectors in eight federal states of Germany after the flood events in 2013. The assessment of the direct economic impacts is object-based and considers uncertainties associated with the hazard, the exposed objects and their vulnerability. The direct economic impacts are then coupled to a supply-side Input-Output-Model to estimate the indirect economic impacts. The procedure provides distributions of direct and indirect economic impacts which capture the associated uncertainties. The distributions of the direct economic impacts in the federal states are plausible when compared to reported values. The ratio between indirect and direct economic impacts shows that the sectors Manufacturing, Financial and Insurance activities suffered the most from indirect economic impacts. These ratios also indicate that indirect economic impacts can be almost as high as direct economic impacts. They differ strongly between the economic sectors indicating that the application of a single factor as a proxy for the indirect impacts of all economic sectors is not appropriate.
How does the international Rule of Law apply to constrain the conduct of the Executive within a constitutional State that adopts a dualist approach to the reception of international law? This paper argues that, so far from being inconsistent with the concept of the Rule of Law, the Executive within a dualist constitution has a self-enforcing obligation to abide by the obligations of the State under international law. This is not dependent on Parliament’s incorporation of treaty obligations into domestic law. It is the correlative consequence of the allocation to the Executive of the power to conduct foreign relations. The paper develops this argument in response to recent debate in the United Kingdom on whether Ministers have an obligation to comply with international law–a reference that the Government removed from the Ministerial Code. It shows that such an obligation is consistent with both four centuries of the practice of the British State and with principle.
Membrane adhesion is a fundamental biological process in which membranes are attached to neighboring membranes or surfaces. Membrane adhesion emerges from a complex interplay between the binding of membrane-anchored receptors/ligands and the membrane properties. In this work, we study membrane adhesion mediated by lipid-anchored saccharides using microsecond-long full-atomistic molecular dynamics simulations. Motivated by neutron scattering experiments on membrane adhesion via lipid-anchored saccharides, we investigate the role of LeX, Lac1, and Lac2 saccharides and membrane fluctuations in membrane adhesion.
We study the binding of saccharides in three different systems: for saccharides in water, for saccharides anchored to essentially planar membranes at fixed separations, and for saccharides anchored to apposing fluctuating membranes. Our simulations of two saccharides in water indicate that the saccharides engage in weak interactions to form dimers. We find that the binding occurs in a continuum of bound states instead of a certain number of well-defined bound structures, which we term as "diffuse binding".
The binding of saccharides anchored to essentially planar membranes strongly depends on separation of the membranes, which is fixed in our simulation system. We show that the binding constants for trans-interactions of two lipid-anchored saccharides monotonically decrease with increasing separation. Saccharides anchored to the same membrane leaflet engage in cis-interactions with binding constants comparable to the trans-binding constants at the smallest membrane separations. The interplay of cis- and trans-binding can be investigated in simulation systems with many lipid-anchored saccharides. For Lac2, our simulation results indicate a positive cooperativity of trans- and cis-binding. In this cooperative binding the trans-binding constant is enhanced by the cis-interactions. For LeX, in contrast, we observe no cooperativity between trans- and cis-binding. In addition, we determine the forces generated by trans-binding of lipid-anchored saccharides in planar membranes from the binding-induced deviations of the lipid-anchors. We find that the forces acting on trans-bound saccharides increase with increasing membrane separation to values of the order of 10 pN.
The binding of saccharides anchored to the fluctuating membranes results from an interplay between the binding properties of the lipid-anchored saccharides and membrane fluctuations. Our simulations, which have the same average separation of the membranes as obtained from the neutron scattering experiments, yield a binding constant larger than in planar membranes with the same separation. This result demonstrates that membrane fluctuations play an important role at average membrane separations which are seemingly too large for effective binding. We further show that the probability distribution of the local separation can be well approximated by a Gaussian distribution. We calculate the relative membrane roughness and show that our results are in good agreement with the roughness values reported from the neutron scattering experiments.
The habilitation thesis presented here includes results from several studies dealing with fluid-rock interactions and rock deformation processes in active fault zones. The focus in all of these studies is on the influence of clay minerals on the geochemical and the hydro-mechanical behavior of the fault rocks. The research was conducted on rock cores and cuttings from four scientific drilling projects at the San Andreas Fault (USA), the Nankai Trough subduction zone and the Japan Trench subduction zone (Japan), as well as the Alpine Fault in New Zealand. These ICDP (International Continental Scientific Drilling Program) and IODP (International Ocean Discovery Program) funded projects were all conducted with the aim to monitor and better understand earthquakes.
Chapter 1 contains a short introduction to the topic with basic principles and objectives regarding the research approach. Chapter 2 describes the state of the art in clay mineral and fault zone science, gives a short description of the individual drilling projects and their locations on which the research was based, and summarizes the most important analytical methods used. Chapter 3 comprises ten peer-reviewed publications that are connected thematically and methodologically. The papers were published in the years 2006-2015, and additional related publications including myself as co-author are given in the literature list. The ten publications address different questions concerning the formation of clay minerals and processes of fluid-rock interaction in active fault zones. Six papers contain results from the SAFOD drilling project, USA (San Andreas Fault Observatory at Depth), with the main focus on fluid-rock interaction processes in fault rocks and the formation and location of clay minerals. Three publications report on research from the NanTroSEIZE drilling project (Nankai Trough Seismogenic Zone Experiment) and the JFAST drilling project (Japan Trench Fast Drilling Project). Both projects are situated in Japan. Here, the swelling behavior of smectite clay minerals in relation to changing environmental conditions (e.g. temperature and/or humidity) was investigated. The last publication included here concerns a study from the DFDP project (Deep Fault Drilling Project) in New Zealand, where I investigated the deformation of clay minerals on the context of the hydro-mechanical behavior of the fault zone rocks. I was first author in nine of the publications and in charge of the project preparation, measurements and data analyses, and the completion of the manuscript. As co-author on the other publication I was responsible for electronmicroscopy analyses (SEM and TEM) and their interpretation.
The key results from the publications in Chapter 3 are discussed in Chapter 4 with additional considerations from more recent papers. Following the major theses in Chapter 5, Chapter 6 highlights a future research project in clay mineralogy research at the GFZ. An appendix includes more detailed descriptions of the laboratory equipment and lists of all publications, conference contributions and teaching courses and modules.
On being and belonging
(2019)
Expanding public or publicly subsidized childcare has been a top social policy priority in many industrialized countries. It is supposed to increase fertility, promote children’s development and enhance mothers’ labor market attachment. In this paper, we analyze the causal effect of one of the largest expansions of subsidized childcare for children up to three years among industrialized countries on the employment of mothers in Germany. Identification is based on spatial and temporal variation in the expansion of publicly subsidized childcare triggered by two comprehensive childcare policy reforms. The empirical analysis is based on the German Microcensus that is matched to county level data on childcare availability. Based on our preferred specification which includes time and county fixed effects we find that an increase in childcare slots by one percentage point increases mothers’ labor market participation rate by 0.2 percentage points. The overall increase in employment is explained by the rise in part-time employment with relatively long hours (20-35 hours per week). We do not find a change in full-time employment or lower part-time employment that is causally related to the childcare expansion. The effect is almost entirely driven by mothers with medium-level qualifications. Mothers with low education levels do not profit from this reform calling for a stronger policy focus on particularly disadvantaged groups in coming years.
The present dissertation about teachers’ cultural diversity beliefs and culturally responsive practices includes a general introduction (Chapter 1), a systematic literature review (Chapter 2), three empirical studies (Chapter 3, 4, and 5) and it ends with a general discussion and conclusion (Chapter 6). The major focus of investigation laid in creating a deeper understanding of teachers’ beliefs about cultural diversity and how those beliefs are related to teaching practices, which could or could not be considered to be culturally responsive. In this dissertation, I relied on insights from theoretical perspectives that derived from the field of psychology such as social cognitive theory and intergroup ideologies, as well as from the field of multicultural education such as culturally responsive teaching.
In Chapter 1, I provide the background of this dissertation, with contextual information regarding the German educational system, the theoretical framework used and the main research objectives of each study.
In Chapter 2, I conducted a systematic review of the existing international studies on trainings addressing cultural diversity beliefs with pre-service teachers. More specifically, the aims of the systematic literature review were (1) to provide a description of main components and contextual characteristics of teacher trainings targeting cultural diversity beliefs, (2) report the training effects, and (3) detail the methodological strengths and weaknesses of these studies. By examining the main components and contextual characteristics of teacher trainings, the effects on beliefs about cultural diversity as well as the methodological strengths and weaknesses of these studies in a single review, I took an integrated approach to these three processes. To review the final pool of studies (N = 36) I used a descriptive and narrative approach, relying primarily on the use of words and text to summarise and explain findings of the synthesis.
The three empirical studies that follow, all highlight aspects of how far and how teacher beliefs about cultural diversity translate into real-world practices in schools. In Chapter 3, to expand the validity of culturally responsive teaching to the German context, I aimed at verifying the dimensional structure of German version of the Culturally Responsive Classroom Management Self-Efficacy Scale (CRCMSES; Siwatu, Putman, Starker-Glass, & Lewis, 2015). I conducted Exploratory and Confirmatory Factor Analysis, and run correlations between the subscales of the CRCMSES and a measure of cultural diversity- related stress. Data (n = 504) used for the first empirical study (Chapter 3) were collected in the InTePP-project (Inclusive Teaching Professionalization Panel) in which pre-service teachers’ competencies and beliefs were assessed longitudinally at two universities: the University of Potsdam and the University of Cologne.
In the second empirical study, which forms Chapter 4, the focus is on teachers’ practices resembling school approaches to cultural diversity. In this study, I investigated two research questions: (1a) What types of descriptive norms regarding cultural diversity are perceived by teachers and students with and without an immigrant background and (1b) what is their degree of congruence? Additionally, I was also interested in how are teachers’ and students’ perceptions of descriptive norms about cultural diversity related to practices and artefacts in the physical and virtual school environment? Data for the second empirical study (Chapter 4) were previously collected in a dissertation project of doctor Maja Schachner funded by the federal program “ProExzellenz” of the Free State of Thuringia. Adopting a mixed-methods research design I conducted a secondary analysis of data from teachers’ (n = 207) and students’ (n = 1,644) gathered in 22 secondary schools in south-west Germany. Additional sources of data in this study were based on pictures of school interiors (hall and corridors) and sixth-grade classrooms’ walls (n = 2,995), and screenshots from each school website (n = 6,499).
Chapter 5 addresses the question of how culturally responsive teaching, teacher cultural diversity beliefs, and self-reflection on own teaching are related. More specifically, in this study I addressed two research questions: (1) How does CRT relate to teachers’ beliefs about incorporating cultural diversity content into daily teaching and learning activities? And (2) how does the level of teachers’ self-reflection on their own teaching relate to CRT?
For this last empirical chapter, I conducted a multiple case study with four ethnic German teachers who work in one culturally and ethnically diverse high school in Berlin, using classroom video observations and post-observation interviews.
In the final chapter (Chapter 6), I summarised the main findings of the systematic literature review and three empirical studies, and discuss their scientific and practical implications.
This dissertation makes a significant contribution to the field of educational science to understanding culturally responsive teaching in terms of its measurement, focus on both beliefs and practices and the link between the two, and theoretical, practical, and future study implications.
We use panel data from Germany to analyze the effect of population density on urban air pollution (nitrogen oxides, particulate matter and ozone). To address unobserved heterogeneity and omitted variables, we present long difference/fixed effects estimates and instrumental variables estimates, using historical population and soil quality as instruments. Our preferred estimates imply that a one-standard deviation increase in population density increases air pollution by 3-12%.
”Thanks in Advance”
(2019)
This paper studies the effect of the commonly used phrase “thanks in advance” on compliance with a small request. In a controlled laboratory experiment we ask participants to give a detailed answer to an open question. The treatment variable is whether or not they see the phrase “thanks in advance.” Our participants react to the treatment by exerting less effort in answering the request even though they perceive the phrase as polite.
The German start-up subsidy (SUS) program for the unemployed has recently undergone a major make-over, altering its institutional setup, adding an additional layer of selection and leading to ambiguous predictions of the program’s effectiveness. Using propensity score matching (PSM) as our main empirical approach, we provide estimates of long-term effects of the post-reform subsidy on individual employment prospects and labor market earnings up to 40 months after entering the program. Our results suggest large and persistent long-term effects of the subsidy on employment probabilities and net earned income. These effects are larger than what was estimated for the pre-reform program. Extensive sensitivity analyses within the standard PSM framework reveal that the results are robust to different choices regarding the implementation of the weighting procedure and also with respect to deviations from the conditional independence assumption. As a further assessment of the results’ sensitivity, we go beyond the standard selection-on-observables approach and employ an instrumental variable setup using regional variation in the likelihood of receiving treatment. Here, we exploit the fact that the reform increased the discretionary power of local employment agencies in allocating active labor market policy funds, allowing us to obtain a measure of local preferences for SUS as the program of choice. The results based on this approach give rise to similar estimates. Thus, our results indicating that SUS are still an effective active labor market program after the reform do not appear to be driven by “hidden bias”.
We combine ultrafast X-ray diffraction (UXRD) and time-resolved Magneto-Optical Kerr Effect (MOKE) measurements to monitor the strain pulses in laser-excited TbFe2/Nb heterostructures. Spatial separation of the Nb detection layer from the laser excitation region allows for a background-free characterization of the laser-generated strain pulses. We clearly observe symmetric bipolar strain pulses if the excited TbFe2 surface terminates the sample and a decomposition of the strain wavepacket into an asymmetric bipolar and a unipolar pulse, if a SiO2 glass capping layer covers the excited TbFe2 layer. The inverse magnetostriction of the temporally separated unipolar strain pulses in this sample leads to a MOKE signal that linearly depends on the strain pulse amplitude measured through UXRD. Linear chain model simulations accurately predict the timing and shape of UXRD and MOKE signals that are caused by the strain reflections from multiple interfaces in the heterostructure.
We combine ultrafast X-ray diffraction (UXRD) and time-resolved Magneto-Optical Kerr Effect (MOKE) measurements to monitor the strain pulses in laser-excited TbFe2/Nb heterostructures. Spatial separation of the Nb detection layer from the laser excitation region allows for a background-free characterization of the laser-generated strain pulses. We clearly observe symmetric bipolar strain pulses if the excited TbFe2 surface terminates the sample and a decomposition of the strain wavepacket into an asymmetric bipolar and a unipolar pulse, if a SiO2 glass capping layer covers the excited TbFe2 layer. The inverse magnetostriction of the temporally separated unipolar strain pulses in this sample leads to a MOKE signal that linearly depends on the strain pulse amplitude measured through UXRD. Linear chain model simulations accurately predict the timing and shape of UXRD and MOKE signals that are caused by the strain reflections from multiple interfaces in the heterostructure.
This paper presents an experiment on the effect of retroactive price-reduction schemes on buyers’ repeated purchase decisions. Such schemes promise buyers a reduced price for all units that are bought in a certain time frame if the total quantity that is purchased passes a given threshold. This study finds a loyalty-enhancing effect of retroactive price-reduction schemes only if the buyers ex-ante expected that entering into the scheme would maximize their monetary gain, but later learn that they should leave the scheme. Furthermore, the effect crucially hinges on the framing of the price reduction.
A rich literature links knowledge inputs with innovative outputs. However, most of what is known is restricted to manufacturing. This paper analyzes whether the three aspects involving innovative activity - R&D; innovative output; and productivity - hold for knowledge intensive services. Combining the models of Crepon et al. (1998) and of Ackerberg et al. (2015), allows for causal interpretation of the relationship between innovation output and labor productivity. We find that knowledge intensive services benefit from innovation activities in the sense that these activities causally increase their labor productivity. Moreover, the firm size advantage found for manufacturing in previous studies nearly disappears for knowledge intensive services.
The paper extends a static discrete-choice labor supply model by adding participation and hours constraints. We identify restrictions by survey information on the eligibility and search activities of individuals as well as actual and desired hours. This provides for a more robust identification of preferences and constraints. Both, preferences and restrictions are allowed to vary by and are related through observed and unobserved characteristics. We distinguish various restrictions mechanisms: labor demand rationing, working hours norms varying across occupations, and insufficient public childcare on the supply side of the market. The effect of these mechanisms is simulated by relaxing different constraints at a time. We apply the empirical frame- work to evaluate an in-work benefit for low-paid parents in the German institutional context. The benefit is supposed to increase work incentives for secondary earners. Based on the structural model we are able to disentangle behavioral reactions into the pure incentive effect and the limiting impact of constraints at the intensive and extensive margin. We find that the in-work benefit for parents substantially increases working hours of mothers of young children, especially when they have a low education. Simulating the effects of restrictions shows their substantial impact on employment of mothers with young children.
In this work we investigated ultrafast demagnetization in a Heusler-alloy. This material belongs to the halfmetal and exists in a ferromagnetic phase. A special feature of investigated alloy is a structure of electronic bands. The last leads to the specific density of the states. Majority electrons form a metallic like structure while minority electrons form a gap near the Fermi-level, like in semiconductor. This particularity offers a good possibility to use this material as model-like structure and to make some proof of principles concerning demagnetization. Using pump-probe experiments we carried out time-resolved measurements to figure out the times of demagnetization. For the pumping we used ultrashort laser pulses with duration around 100 fs. Simultaneously we used two excitation regimes with two different wavelengths namely 400 nm and 1240 nm. Decreasing the energy of photons to the gap size of the minority electrons we explored the effect of the gap on the demagnetization dynamics. During this work we used for the first time OPA (Optical Parametrical Amplifier) for the generation of the laser irradiation in a long-wave regime. We tested it on the FETOSPEX-beamline in BASSYII electron storage ring. With this new technique we measured wavelength dependent demagnetization dynamics. We estimated that the demagnetization time is in a correlation with photon energy of the excitation pulse. Higher photon energy leads to the faster demagnetization in our material. We associate this result with the existence of the energy-gap for minority electrons and explained it with Elliot-Yaffet-scattering events. Additionally we applied new probe-method for magnetization state in this work and verified their effectivity. It is about the well-known XMCD (X-ray magnetic circular dichroism) which we adopted for the measurements in reflection geometry. Static experiments confirmed that the pure electronic dynamics can be separated from the magnetic one. We used photon energy fixed on the L3 of the corresponding elements with circular polarization. Appropriate incidence angel was estimated from static measurements. Using this probe method in dynamic measurements we explored electronic and magnetic dynamics in this alloy.
The DNA origami technique has great potential for the development of brighter and more sensitive reporters for fluorescence based detection schemes such as a microbead-based assay in diagnostic applications. The nanostructures can be programmed to include multiple dye molecules to enhance the measured signal as well as multiple probe strands to increase the binding strength of the target oligonucleotide to these nanostructures. Here we present a proof-of-concept study to quantify short oligonucleotides by developing a novel DNA origami based reporter system, combined with planar microbead assays. Analysis of the assays using the VideoScan digital imaging platform showed DNA origami to be a more suitable reporter candidate for quantification of the target oligonucleotides at lower concentrations than a conventional reporter that consists of one dye molecule attached to a single stranded DNA. Efforts have been made to conduct multiplexed analysis of different targets as well as to enhance fluorescence signals obtained from the reporters. We therefore believe that the quantification of short oligonucleotides that exist in low copy numbers is achieved in a better way with the DNA origami nanostructures as reporters.
The DNA origami technique has great potential for the development of brighter and more sensitive reporters for fluorescence based detection schemes such as a microbead-based assay in diagnostic applications. The nanostructures can be programmed to include multiple dye molecules to enhance the measured signal as well as multiple probe strands to increase the binding strength of the target oligonucleotide to these nanostructures. Here we present a proof-of-concept study to quantify short oligonucleotides by developing a novel DNA origami based reporter system, combined with planar microbead assays. Analysis of the assays using the VideoScan digital imaging platform showed DNA origami to be a more suitable reporter candidate for quantification of the target oligonucleotides at lower concentrations than a conventional reporter that consists of one dye molecule attached to a single stranded DNA. Efforts have been made to conduct multiplexed analysis of different targets as well as to enhance fluorescence signals obtained from the reporters. We therefore believe that the quantification of short oligonucleotides that exist in low copy numbers is achieved in a better way with the DNA origami nanostructures as reporters.
According to recent literature sodium bicarbonate (NaHCO3) has been proposed as a performance enhancing aid by reducing acidosis during exercise. The aim of the current review is to investigate if the duration of exercise is an essential factor for the effect
of NaHCO3. To collect the latest studies from electronic database
of PubMed, study publication time was restricted from December 2006 to December 2016. The search was updated in July 2018. The studies were divided into exercise durations of > 4 or ≤ 4 minutes for easier comparability of their effects in different exercises. Only randomized controlled trials were included in this review. Of the 775 studies, 35 met the inclusion criteria. Study design, subjects, effects as well as outcome criteria were inconsistent throughout the studies. Seventeen of these studies reported
performance enhancing effects after supplementing NaHCO3. Eleven of twenty studies with exercise duration of ≤ 4 minutes showed positive and four diverse results after supplementing NaHCO3. On the other hand six of fifteen studies with an exercise duration of >4 minutes showed performance enhancing and two studies showed diverse results. Consequently, the duration of exercise might be influential for inducing a performance enhancing effect when supplementing NaHCO3, but to which extent, remains unclear due to the inconsistencies in the study results.
According to recent literature sodium bicarbonate (NaHCO3) has been proposed as a performance enhancing aid by reducing acidosis during exercise. The aim of the current review is to investigate if the duration of exercise is an essential factor for the effect
of NaHCO3. To collect the latest studies from electronic database
of PubMed, study publication time was restricted from December 2006 to December 2016. The search was updated in July 2018. The studies were divided into exercise durations of > 4 or ≤ 4 minutes for easier comparability of their effects in different exercises. Only randomized controlled trials were included in this review. Of the 775 studies, 35 met the inclusion criteria. Study design, subjects, effects as well as outcome criteria were inconsistent throughout the studies. Seventeen of these studies reported
performance enhancing effects after supplementing NaHCO3. Eleven of twenty studies with exercise duration of ≤ 4 minutes showed positive and four diverse results after supplementing NaHCO3. On the other hand six of fifteen studies with an exercise duration of >4 minutes showed performance enhancing and two studies showed diverse results. Consequently, the duration of exercise might be influential for inducing a performance enhancing effect when supplementing NaHCO3, but to which extent, remains unclear due to the inconsistencies in the study results.
Getting a Yes
(2019)
This paper studies how the request for a favor has to be devised in order to maximize its chance of success. We present results from a mini-dictator game, in which the recipient can send a free-form text message to the dictator before the latter decides. We find that putting effort into the message, writing in a humorous way and mentioning reasons why the money is needed pays off. Additionally, we find differences in the behavior of male and female dictators. Only men react positively to efficiency arguments, while only women react to messages that emphasize the dictator’s power and responsibility.
Presupposition triggers differ with respect to whether their presupposition is easily accommodatable. The presupposition of focus-sensitive additive particles like also or too is often classified as hard to accommodate, i.e., these triggers are infelicitous if their presupposition is not entailed by the immediate linguistic or non-linguistic context. We tested two competing accounts for the German additive particle auch concerning this requirement: First, that it requires a focus alternative to the whole proposition to be salient, and second, that it merely requires an alternative to the focused constituent (e.g., an individual) to be salient. We conducted two experiments involving felicity judgments as well as questions asking for the truth of the presupposition to be accommodated. Our results suggest that the latter account is too weak: mere previous mention of a potential alternative to the focused constituent is not enough to license the use of auch. However, our results also suggest that the former account is too strong: when an alternative of the focused constituent is prementioned and certain other accommodation-enhancing factors are present, the context does not have to entail the presupposed proposition. We tested the following two potentially accommodation-enhancing factors: First, whether the discourse can be construed to be from the perspective of the individual that the presupposition is about, and second, whether the presupposition is needed to establish coherence between the host sentence of the additive particle and the preceding context. The factor coherence was found to play a significant role. Our results thus corroborate the results of other researchers showing that discourse participants go to great lengths in order to identify a potential presupposition to accommodate, and we contribute to these results by showing that coherence is one of the factors that enhance accommodation.
Presupposition triggers differ with respect to whether their presupposition is easily accommodatable. The presupposition of focus-sensitive additive particles like also or too is often classified as hard to accommodate, i.e., these triggers are infelicitous if their presupposition is not entailed by the immediate linguistic or non-linguistic context. We tested two competing accounts for the German additive particle auch concerning this requirement: First, that it requires a focus alternative to the whole proposition to be salient, and second, that it merely requires an alternative to the focused constituent (e.g., an individual) to be salient. We conducted two experiments involving felicity judgments as well as questions asking for the truth of the presupposition to be accommodated. Our results suggest that the latter account is too weak: mere previous mention of a potential alternative to the focused constituent is not enough to license the use of auch. However, our results also suggest that the former account is too strong: when an alternative of the focused constituent is prementioned and certain other accommodation-enhancing factors are present, the context does not have to entail the presupposed proposition. We tested the following two potentially accommodation-enhancing factors: First, whether the discourse can be construed to be from the perspective of the individual that the presupposition is about, and second, whether the presupposition is needed to establish coherence between the host sentence of the additive particle and the preceding context. The factor coherence was found to play a significant role. Our results thus corroborate the results of other researchers showing that discourse participants go to great lengths in order to identify a potential presupposition to accommodate, and we contribute to these results by showing that coherence is one of the factors that enhance accommodation.
The semiarid northeast of Brazil is one of the most densely populated dryland regions in the world and recurrently affected by severe droughts. Thus, reliable seasonal forecasts of streamflow and reservoir storage are of high value for water managers. Such forecasts can be generated by applying either hydrological models representing underlying processes or statistical relationships exploiting correlations among meteorological and hydrological variables. This work evaluates and compares the performances of seasonal reservoir storage forecasts derived by a process-based hydrological model and a statistical approach.
Driven by observations, both models achieve similar simulation accuracies. In a hindcast experiment, however, the accuracy of estimating regional reservoir storages was considerably lower using the process-based hydrological model, whereas the resolution and reliability of drought event predictions were similar by both approaches. Further investigations regarding the deficiencies of the process-based model revealed a significant influence of antecedent wetness conditions and a higher sensitivity of model prediction performance to rainfall forecast quality.
Within the scope of this study, the statistical model proved to be the more straightforward approach for predictions of reservoir level and drought events at regionally and monthly aggregated scales. However, for forecasts at finer scales of space and time or for the investigation of underlying processes, the costly initialisation and application of a process-based model can be worthwhile. Furthermore, the application of innovative data products, such as remote sensing data, and operational model correction methods, like data assimilation, may allow for an enhanced exploitation of the advanced capabilities of process-based hydrological models.
The semiarid northeast of Brazil is one of the most densely populated dryland regions in the world and recurrently affected by severe droughts. Thus, reliable seasonal forecasts of streamflow and reservoir storage are of high value for water managers. Such forecasts can be generated by applying either hydrological models representing underlying processes or statistical relationships exploiting correlations among meteorological and hydrological variables. This work evaluates and compares the performances of seasonal reservoir storage forecasts derived by a process-based hydrological model and a statistical approach.
Driven by observations, both models achieve similar simulation accuracies. In a hindcast experiment, however, the accuracy of estimating regional reservoir storages was considerably lower using the process-based hydrological model, whereas the resolution and reliability of drought event predictions were similar by both approaches. Further investigations regarding the deficiencies of the process-based model revealed a significant influence of antecedent wetness conditions and a higher sensitivity of model prediction performance to rainfall forecast quality.
Within the scope of this study, the statistical model proved to be the more straightforward approach for predictions of reservoir level and drought events at regionally and monthly aggregated scales. However, for forecasts at finer scales of space and time or for the investigation of underlying processes, the costly initialisation and application of a process-based model can be worthwhile. Furthermore, the application of innovative data products, such as remote sensing data, and operational model correction methods, like data assimilation, may allow for an enhanced exploitation of the advanced capabilities of process-based hydrological models.
The present dissertation investigates profit-maximizing behavior in different phases of the negotiation process. Over the last decades, research dealt in detail with behavior of negotiation actors with the aim of identifying performance enhancing factors. The majority of those studies focused on behavior within the main negotiation phase. This work, however, considers phases which are, so far, underrepresented in research but show an impact on the negotiation process and outcome. Those phases are the pre-negotiation, the first offer, and the main negotiation phase which is further divided by breaks into several rounds. Within these phases, traits of behavior are analyzed that can be used strategically in order to impact the negotiation outcome. The dissertation contains three papers, each one dealing with a specific strategy within one phase. The first paper investigates communication behavior in the pre-negotiation phase. Content analysis of a negotiation experiment shows that the employment of positive communication elements such as the generation of enthusiasm for an upcoming project results in an increase of agreements on entering a negotiation and also leads to a higher willingness to make concessions. The second paper explores the impact of a semantic first anchor, which does not contain a specific number but only gives a numerical direction, on the opponent’s concession behavior and the final outcome. By means of two scenario-based questionnaires and a negotiation experiment it is demonstrated that semantic offers reveal an anchoring effect and lead to better negotiation outcomes. The third paper deals with the introduction of breaks and their effect on the following negotiation process. Therefore, content and outcome of another negotiation experiment are investigated. The analysis shows that breaks evoke a dominant impression but can negatively impact the atmosphere and thereby also the outcome. Finally, the gathered insights are brought together and discussed. The dissertation closes with implications for practice, limitations of the work, and ideas for future research.
Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.
We measure valence-to-core x-ray emission spectra of compressed crystalline GeO₂ up to 56 GPa and of amorphous GeO₂ up to 100 GPa. In a novel approach, we extract the Ge coordination number and mean Ge-O distances from the emission energy and the intensity of the Kβ'' emission line. The spectra of high-pressure polymorphs are calculated using the Bethe-Salpeter equation. Trends observed in the experimental and calculated spectra are found to match only when utilizing an octahedral model. The results reveal persistent octahedral Ge coordination with increasing distortion, similar to the compaction mechanism in the sequence of octahedrally coordinated crystalline GeO₂ high-pressure polymorphs.
We measure valence-to-core x-ray emission spectra of compressed crystalline GeO₂ up to 56 GPa and of amorphous GeO₂ up to 100 GPa. In a novel approach, we extract the Ge coordination number and mean Ge-O distances from the emission energy and the intensity of the Kβ'' emission line. The spectra of high-pressure polymorphs are calculated using the Bethe-Salpeter equation. Trends observed in the experimental and calculated spectra are found to match only when utilizing an octahedral model. The results reveal persistent octahedral Ge coordination with increasing distortion, similar to the compaction mechanism in the sequence of octahedrally coordinated crystalline GeO₂ high-pressure polymorphs.
Multifunctional reprogrammable actuators based on polymer networks with crystallizable segments
(2019)
Soft polymeric materials, which can change their shape reversibly in response to external stimuli, can serve as actuating components in robotic systems. Besides electroactive polymers (EAP), hydrogels and liquid crystalline elastomers (LCE), crosslinked crystallizable shape-memory polymers networks have been introduced recently as reprogrammable thermo-reversible actuators. The integration of additional functions in such materials will lead to multifunctional polymeric actuators, which meet the complex requirements of modern robotic applications.
The primary aim of this thesis was to achieve multifunctional reprogrammable thermo-reversible actuators based on thermoplastic polymers. Here, three different actuators providing additional functionalities such as surface modification capability (i), self-healing capability (ii) or a tailorable non-response function enabling noncontinuous multi-step motions (iii) were realized. At first, it was hypothesized that surface modifiable polymeric actuators (i) can be achieved by crosslinking of crystallizable thermoplastic terpolymers having reactive moieties, where subsequent thermomechanical programming enables reversible actuations while the sustained reactive groups allow post surface modification. For the second actuator type (ii) it was hypothesized that self-healing during reprogramming of polymeric actuators prepared by crosslinking of crystallizable linear homopolymers, can be achieved by adjusting the amount of freely interpenetrating extractable polymer moieties. Finally, it was hypothesized that thermo-reversible actuators providing a non-response function (iii) and thus enable multistep motions upon continuous normal stimulation, can be achieved by a crosslinked blend of two thermoplastic polymers with co-continuous morphology having a well-separated melting and crystallization transitions. In addition, these actuators can be physically reprogrammed by heating above all melting transitions to provide a different actuating shape.
In this study, surface functionalizable actuators were realized from crosslinked poly[(ethylene)-co-(ethyl acrylate)-co-(maleic anhydride)] (cPEEAMA) based networks. Here crystallizable polyethylene (PE) segments should serve as actuation segments, ethyl acrylate (EA) provides elasticity to the system required for deformation, while reactive maleic anhydride (MA) will be used as chemically modifiable entities for post surface modification. Networks with varied crosslink density were prepared and its effect on thermomechanical properties as well as actuation performance was analyzed. Cyclic thermomechanical experiments were employed to investigate the actuation capability, which revealed a reversible actuation (ε׳rev) between 5 and 15%. Fourier-transform infrared spectroscopy (FTIR) measurements confirmed that MA groups were sustained at the sample surface after processing and programming, which could be modified by reaction with ethylene diamine. Such amine functionalization allows the attachment of bioactive molecules to the actuator surface, which might provide a route to actuating substrates for biotechnology.
Self-healable actuating materials were realized by poly(ε-caprolactone) (PCL) polymer networks with extractable linear PCL fractions of 5 to 60 wt%. A detailed evaluation of the actuation capabilities by cyclic experiments revealed the highest reversible change in strain of Δε = 24% for the cPCL network with 30 wt% of linear polymer. The thermal treatment of damaged samples resulted in the healing of the network when heated to 80 °C. Here a linear polymer fraction ≥ 30 wt% was necessary to achieve a self-healing efficiency of ≥ 50%. The application of such high temperatures erases the programmed actuator shape and at the same time allows to reprogram a new actuating shape. Such sustainable actuators with self-healing function are of great interest for future robotic devices.
Afore mentioned actuators operate continuously between two shapes and their movements can only be interrupted when the temperature is stopped. To overcome this limitation, noncontinuously responding actuators enabling multi-step actuation were realized from crosslinked blend networks prepared from PCL and poly[(ethylene)-co-(vinyl acetate)] (PEVA). These polymers (PCL and PEVA) were selected due to their immiscible character, where crystallizable PE and PCL segments provide two different actuation units, while vinyl acetate (VA) segment enabled sufficient elasticity of the system. A gap of 20 K in the melting and crystallization temperature of PE and PCL was achieved by selecting PEVA with 5 wt% VA content (cPCL-PEVA5) providing a co-continuous phase morphology. Cyclic thermomechanical investigations were employed to investigate noncontinuous actuation, which revealed a high Δε = 25% with a similar contribution from PCL and PE actuation units with a non-response region in the temperature range from 50 to 71 °C in heating step and 30 to 60 °C in cooling step. The actuation related to PCL part changed from 13 to 2% by altering the heating and cooling rates from 3 to 10 K·min-1. Free-standing reversible noncontinuous actuation was realized by rotating demonstrator which exhibits reversible angle change in a custom-made setup. For this purpose, cPCL-PEVA5 stripe was programmed by twisting and reversible rotational actuation was realized from 0 to 180° while pausing in the 90° position during non-response. These blends can be physically programmed to perform reversible noncontinuous actuations, while the programmed geometry can be erased by heating it to temperature above all melting transitions. By physically reprogramming of the material various different actuation modes can be obtained. Such a noncontinuous actuator would be relevant for designing interruptive actuating soft robots at continuous trigger signals.
Skarn deposits are found on every continents and were formed at different times from Precambrian to Tertiary. Typically, the formation of a skarn is induced by a granitic intrusion in carbonates-rich sedimentary rocks. During contact metamorphism, fluids derived from the granite interact with the sedimentary host rocks, which results in the formation of calc-silicate minerals at the expense of carbonates. Those newly formed minerals generally develop in a metamorphic zoned aureole with garnet in the proximal and pyroxene in the distal zone. Ore elements contained in magmatic fluids are precipitated due to the change in fluid composition. The temperature decrease of the entire system, due to the cooling of magmatic fluids and the entering of meteoric water, allows retrogression of some prograde minerals.
The Hämmerlein skarn deposit has a multi-stage history with a skarn formation during regional metamorphism and a retrogression of primary skarn minerals during the granitic intrusion. Tin was mobilized during both events. The 340 Ma old tin-bearing skarn minerals show that tin was present in sediments before the granite intrusion, and that the first Sn enrichment occurred during the skarn formation by regional metamorphism fluids. In a second step at ca. 320 Ma, tin-bearing fluids were produced with the intrusion of the Eibenstock granite. Tin, which has been added by the granite and remobilized from skarn calc-silicates, precipitated as cassiterite.
Compared to clay or marl, the skarn is enriched in Sn, W, In, Zn, and Cu. These metals have been supplied during both regional metamorphism and granite emplacement. In addition, the several isotopic and chemical data of skarn samples show that the granite selectively added elements such as Sn, and that there was no visible granitic contribution to the sedimentary signature of the skarn
The example of Hämmerlein shows that it is possible to form a tin-rich skarn without associated granite when tin has already been transported from tin-bearing sediments during regional metamorphism by aqueous metamorphic fluids. These skarns are economically not interesting if tin is only contained in the skarn minerals. Later alteration of the skarn (the heat and fluid source is not necessarily a granite), however, can lead to the formation of secondary cassiterite (SnO2), with which the skarn can become economically highly interesting.
Force plays a fundamental role in the regulation of biological processes. Cells can sense the mechanical properties of the extracellular matrix (ECM) by applying forces and transmitting mechanical signals. They further use mechanical information for regulating a wide range of cellular functions, including adhesion, migration, proliferation, as well as differentiation and apoptosis. Even though it is well understood that mechanical signals play a crucial role in directing cell fate, surprisingly little is known about the range of forces that define cell-ECM interactions at the molecular level.
Recently, synthetic molecular force sensor (MFS) designs have been established for measuring the molecular forces acting at the cell-ECM interface. MFSs detect the traction forces generated by cells and convert this mechanical input into an optical readout. They are composed of calibrated mechanoresponsive building blocks and are usually equipped with a fluorescence reporter system. Up to date, many different MFS designs have been introduced and successfully used for measuring forces involved in the adhesion of mammalian cells. These MFSs utilize different molecular building blocks, such as double-stranded deoxyribonucleic acid (dsDNA) molecules, DNA hairpins and synthetic polymers like polyethylene glycol (PEG). These currently available MFS designs lack ECM mimicking properties.
In this work, I introduce a new MFS building block for cell biology applications, derived from the natural ECM. It combines mechanical tunability with the ability to mimic the native cellular microenvironment. Inspired by structural ECM proteins with load bearing function, this new MFS design utilizes coiled coil (CC)-forming peptides. CCs are involved in structural and mechanical tasks in the cellular microenvironment and many of the key protein components of the cytoskeleton and the ECM contain CC structures. The well-known folding motif of CC structures, an easy synthesis via solid phase methods and the many roles CCs play in biological processes have inspired studies to use CCs as tunable model systems for protein design and assembly. All these properties make CCs ideal candidates as building blocks for MFSs. In this work, a series of heterodimeric CCs were designed, characterized and further used as molecular building blocks for establishing a novel, next-generation MFS prototype.
A mechanistic molecular understanding of their structural response to mechanical load is essential for revealing the sequence-structure-mechanics relationships of CCs. Here, synthetic heterodimeric CCs of different length were loaded in shear geometry and their mechanical response was investigated using a combination of atomic force microscope (AFM)-based single-molecule force spectroscopy (SMFS) and steered molecular dynamics (SMD) simulations. SMFS showed that the rupture forces of short heterodimeric CCs (3-5 heptads) lie in the range of 20-50 pN, depending on CC length, pulling geometry and the applied loading rate (dF/dt). Upon shearing, an initial rise in the force, followed by a force plateau and ultimately strand separation was observed in SMD simulations. A detailed structural analysis revealed that CC response to shear load depends on the loading rate and involves helix uncoiling, uncoiling-assisted sliding in the direction of the applied force and uncoiling-assisted dissociation perpendicular to the force axis.
The application potential of these mechanically characterized CCs as building blocks for MFSs has been tested in 2D cell culture applications with the goal of determining the threshold force for cell adhesion. Fully calibrated, 4- to 5-heptad long, CC motifs (CC-A4B4 and CC-A5B5) were used for functionalizing glass surfaces with MFSs. 3T3 fibroblasts and endothelial cells carrying mutations in a signaling pathway linked to cell adhesion and mechanotransduction processes were used as model systems for time-dependent adhesion experiments. A5B5-MFS efficiently supported cell attachment to the functionalized surfaces for both cell types, while A4B4-MFS failed to maintain attachment of 3T3 fibroblasts after the first 2 hours of initial cell adhesion. This difference in cell adhesion behavior demonstrates that the magnitude of cell-ECM forces varies depending on the cell type and further supports the application potential of CCs as mechanoresponsive and tunable molecular building blocks for the development of next-generation protein-based MFSs.This novel CC-based MFS design is expected to provide a powerful new tool for observing cellular mechanosensing processes at the molecular level and to deliver new insights into the mechanisms and forces involved. This MFS design, utilizing mechanically tunable CC building blocks, will not only allow for measuring the molecular forces acting at the cell-ECM interface, but also yield a new platform for the development of mechanically controlled materials for a large number of biological and medical applications.
In 2015, Germany introduced a statutory hourly minimum wage that was not only universally binding but also set at a relatively high level. We discuss the short-run effects of this new minimum wage on a wide set of socio-economic outcomes, such as employment and working hours, earnings and wage inequality, dependent and self-employment, as well as reservation wages and satisfaction. We also discuss difficulties in the implementation of the minimum wage and the measurement of its effects related to non-compliance and suitability of data sources. Two years after the minimum wage introduction, the following conclusions can be drawn: while hourly wages increased for low-wage earners, some small negative employment effects are also identifiable. The effects on aspired goals, such as poverty and inequality reduction, have not materialized in the short run. Instead, a tendency to reduce working hours is found, which alleviates the desired positive impact on monthly income. Additionally, the level of non-compliance was substantial in the short run, thus drawing attention to problems when implementing such a wide-reaching policy.
Human beings are supposed to possess an approximate number system (ANS) dedicated to extracting and representing approximate numerical magnitude information as well as an object tracking system (OTS) for the rapid and accurate enumeration of small sets. It is assumed that the OTS and the ANS independently contribute to the acquisition of more elaborate numerical concepts. Chinese children have been shown to exhibit more elaborate numerical concepts than their non-Chinese peers, but it is still an open question whether similar cross-national differences exist with regard to the underlying systems, namely the ANS and the OTS. In the present study, we investigated this question by comparing Chinese and German preschool children with regard to their performance in a non-symbolic numerical magnitude comparison task (assessing the ANS) and in an enumeration task (assessing the OTS). In addition, we compared children’s counting skills. To ensure that possible between-group differences could not be explained by differences in more general performance factors, we also assessed children’s reasoning ability and processing speed. Chinese children showed a better counting performance and a more accurate performance in the non-symbolic numerical magnitude comparison task. These differences in performance could not be ascribed to differences in reasoning abilities and processing speed. In contrast, Chinese and German children did not differ significantly in the enumeration of small sets. The superior counting performance of Chinese children was thus found to be reflected in the ANS but not in the OTS.
Regulatory focus is a motivational construct that describes humans’ motivational orientation during goal pursuit. It is conceptualized as a chronic, trait-like, as well as a momentary, state-like orientation. Whereas there is a large number of measures to capture chronic regulatory focus, measures for its momentary assessment are only just emerging. This paper presents the development and validation of a measure of Momentary–Chronic Regulatory Focus. Our development incorporates the distinction between self-guide and reference-point definitions of regulatory focus. Ideals and ought striving are the promotion and prevention dimension in the self-guide system; gain and non-loss regulatory focus are the respective dimensions within the reference-point system. Three-survey-based studies test the structure, psychometric properties, and validity of the measure in its version to assess chronic regulatory focus (two samples of working participants, N = 389, N = 672; one student sample [time 1, N = 105; time 2, n = 91]). In two further studies, an experience sampling study with students (N = 84, k = 1649) and a daily-diary study with working individuals (N = 129, k = 1766), the measure was applied to assess momentary regulatory focus. Multilevel analyses test the momentary measure’s factorial structure, provide support for its sensitivity to capture within-person fluctuations, and provide evidence for concurrent construct validity.
Regulatory focus is a motivational construct that describes humans’ motivational orientation during goal pursuit. It is conceptualized as a chronic, trait-like, as well as a momentary, state-like orientation. Whereas there is a large number of measures to capture chronic regulatory focus, measures for its momentary assessment are only just emerging. This paper presents the development and validation of a measure of Momentary–Chronic Regulatory Focus. Our development incorporates the distinction between self-guide and reference-point definitions of regulatory focus. Ideals and ought striving are the promotion and prevention dimension in the self-guide system; gain and non-loss regulatory focus are the respective dimensions within the reference-point system. Three-survey-based studies test the structure, psychometric properties, and validity of the measure in its version to assess chronic regulatory focus (two samples of working participants, N = 389, N = 672; one student sample [time 1, N = 105; time 2, n = 91]). In two further studies, an experience sampling study with students (N = 84, k = 1649) and a daily-diary study with working individuals (N = 129, k = 1766), the measure was applied to assess momentary regulatory focus. Multilevel analyses test the momentary measure’s factorial structure, provide support for its sensitivity to capture within-person fluctuations, and provide evidence for concurrent construct validity.