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In this combined theoretical and experimental study we report a full analysis of the resonant inelastic X-ray scattering (RIXS) spectra of H2O, D2O and HDO. We demonstrate that electronically-elastic RIXS has an inherent capability to map the potential energy surface and to perform vibrational analysis of the electronic ground state in multimode systems. We show that the control and selection of vibrational excitation can be performed by tuning the X-ray frequency across core-excited molecular bands and that this is clearly reflected in the RIXS spectra. Using high level ab initio electronic structure and quantum nuclear wave packet calculations together with high resolution RIXS measurements, we discuss in detail the mode coupling, mode localization and anharmonicity in the studied systems.
For various experimental applications, microbial cultures at defined, constant densities are highly advantageous over simple batch cultures. Due to high costs, however, devices for continuous culture at freely defined densities still experience limited use. We have developed a small-scale turbidostat for research purposes, which is manufactured from inexpensive components and 3D printed parts. A high degree of spatial system integration and a graphical user interface provide user-friendly operability. The used optical density feedback control allows for constant continuous culture at a wide range of densities and offers to vary culture volume and dilution rates without additional parametrization. Further, a recursive algorithm for on-line growth rate estimation has been implemented. The employed Kalman filtering approach based on a very general state model retains the flexibility of the used control type and can be easily adapted to other bioreactor designs. Within several minutes it can converge to robust, accurate growth rate estimates. This is particularly useful for directed evolution experiments or studies on metabolic challenges, as it allows direct monitoring of the population fitness.
One of the most striking features of recent public sector reform in Europe is privatization. This development raises questions of accountability: By whom and for what are managers of private for-profit organizations delivering public goods held accountable? Analyzing accountability mechanisms through the lens of an institutional organizational approach and on the empirical basis of hospital privatization in Germany, the article contributes to the empirical and theoretical understanding of public accountability of private actors. The analysis suggests that accountability is not declining but rather multiplying. The shifts in the locus and content of accountability cause organizational stress for private hospitals.
Accountability can be conceptualized as institutionalized mechanisms obliging actors to explain their conduct to different forums, which can pose questions and impose sanctions. This article analyses different crises' in immigration policies in Norway, Denmark and Germany along a descriptive framework of five different accountability types: political, administrative, legal, professional and social accountability. The exchanges of information, debate and their consequences between an actor and a forum are crucial to understanding how political-administrative action is carried out in critical situations. First, accountability dynamics emphasize conventional norms and values regarding policy change and, second, formal political responsibility does not necessarily lead to political consequences such as minister resignations in cases of misbehaviour. Consequences strongly depend on how accountability dynamics take place.
School adjustment determines long-term adjustment in society. Yet, immigrant youth do better in some countries than in others. Drawing on acculturation research (Berry, 1997; Ward, 2001) and self-determination theory (Ryan and Deci, 2000), we investigated indirect effects of adolescent immigrants’ acculturation orientations on school adjustment (school-related attitudes, truancy, and mathematics achievement) through school belonging. Analyses were based on data from the Programme for International Student Assessment from six European countries, which were combined into three clusters based on their migrant integration and multicultural policies: Those with the most supportive policies (Belgium and Finland), those with moderately supportive policies (Italy and Portugal), and those with the most unsupportive policies (Denmark and Slovenia). In a multigroup path model, we confirmed most associations. As expected, mainstream orientation predicted higher belonging and better outcomes in all clusters, whereas the added value of students’ ethnic orientation was only observed in some clusters. Results are discussed in terms of differences in acculturative climate and policies between countries of settlement.
Continuous exercise (CON) and high-intensity interval exercise (HIIE) can be safely performed with type 1 diabetes mellitus (T1DM). Additionally, continuous glucose monitoring (CGM) systems may serve as a tool to reduce the risk of exercise-induced hypoglycemia. It is unclear if CGM is accurate during CON and HIIE at different mean workloads. Seven T1DM patients performed CON and HIIE at 5% below (L) and above (M) the first lactate turn point (LTP1), and 5% below the second lactate turn point (LTP2) (H) on a cycle ergometer. Glucose was measured via CGM and in capillary blood (BG). Differences were found in comparison of CGM vs. BG in three out of the six tests (p < 0.05). In CON, bias and levels of agreement for L, M, and H were found at: 0.85 (−3.44, 5.15) mmol·L−1, −0.45 (−3.95, 3.05) mmol·L−1, −0.31 (−8.83, 8.20) mmol·L−1 and at 1.17 (−2.06, 4.40) mmol·L−1, 0.11 (−5.79, 6.01) mmol·L−1, 1.48 (−2.60, 5.57) mmol·L−1 in HIIE for the same intensities. Clinically-acceptable results (except for CON H) were found. CGM estimated BG to be clinically acceptable, except for CON H. Additionally, using CGM may increase avoidance of exercise-induced hypoglycemia, but usual BG control should be performed during intense exercise.
Landscape evolution models (LEMs) allow the study of earth surface responses to changing climatic and tectonic forcings. While much effort has been devoted to the development of LEMs that simulate a wide range of processes, the numerical accuracy of these models has received less attention. Most LEMs use first-order accurate numerical methods that suffer from substantial numerical diffusion. Numerical diffusion particularly affects the solution of the advection equation and thus the simulation of retreating landforms such as cliffs and river knickpoints. This has potential consequences for the integrated response of the simulated landscape. Here we test a higher-order flux-limiting finite volume method that is total variation diminishing (TVD-FVM) to solve the partial differential equations of river incision and tectonic displacement. We show that using the TVD-FVM to simulate river incision significantly influences the evolution of simulated landscapes and the spatial and temporal variability of catchment-wide erosion rates. Furthermore, a two-dimensional TVD-FVM accurately simulates the evolution of landscapes affected by lateral tectonic displacement, a process whose simulation was hitherto largely limited to LEMs with flexible spatial discretization. We implement the scheme in TTLEM (TopoToolbox Landscape Evolution Model), a spatially explicit, raster-based LEM for the study of fluvially eroding landscapes in TopoToolbox 2.
Across currents
(2017)
This cumulative dissertation consists of five chapters. In terms of research content, my thesis can be divided into two parts. Part one examines local interactions and spillover effects between small regional governments using spatial econometric methods. The second part focuses on patterns within municipalities and inspects which institutions of citizen participation, elections and local petitions, influence local housing policies.
Age-related decline in executive functions and postural control due to degenerative processes in the central nervous system have been related to increased fall-risk in old age. Many studies have shown cognitive-postural dual-task interference in old adults, but research on the role of specific executive functions in this context has just begun. In this study, we addressed the question whether postural control is impaired depending on the coordination of concurrent response-selection processes related to the compatibility of input and output modality mappings as compared to impairments related to working-memory load in the comparison of cognitive dual and single tasks. Specifically, we measured total center of pressure (CoP) displacements in healthy female participants aged 19–30 and 66–84 years while they performed different versions of a spatial one-back working memory task during semi-tandem stance on an unstable surface (i.e., balance pad) while standing on a force plate. The specific working-memory tasks comprised: (i) modality compatible single tasks (i.e., visual-manual or auditory-vocal tasks), (ii) modality compatible dual tasks (i.e., visual-manual and auditory-vocal tasks), (iii) modality incompatible single tasks (i.e., visual-vocal or auditory-manual tasks), and (iv) modality incompatible dual tasks (i.e., visual-vocal and auditory-manual tasks). In addition, participants performed the same tasks while sitting. As expected from previous research, old adults showed generally impaired performance under high working-memory load (i.e., dual vs. single one-back task). In addition, modality compatibility affected one-back performance in dual-task but not in single-task conditions with strikingly pronounced impairments in old adults. Notably, the modality incompatible dual task also resulted in a selective increase in total CoP displacements compared to the modality compatible dual task in the old but not in the young participants. These results suggest that in addition to effects of working-memory load, processes related to simultaneously overcoming special linkages between input- and output modalities interfere with postural control in old but not in young female adults. Our preliminary data provide further evidence for the involvement of cognitive control processes in postural tasks.
Das von Alexander von Humboldt ab 1804 oder später verfasste Manuskript „Isle de Cube. Antilles en général“ wurde erst kürzlich zum ersten Mal veröffentlicht. Es stellt die Grundlage für den Essai politique sur l‘île de Cuba (1826) dar, der als das „wichtigste liberale Manifest des 19. Jahrhunderts gegen die Sklaverei“ gilt. Ziel der Untersuchung ist, die textgenetische inhaltliche und stilistische Entwicklung vom Manuskript zur Publikation ansatzweise nachverfolgen zu können, um Rückschlüsse auf Humboldts Arbeitsweise und Strategien als Autor mit einem politischen Anliegen zu ziehen.
The all-female Amazon molly (Poecilia formosa) is the result of a hybridization of the Atlantic molly (P. mexicana) and the sailfin molly (P. latipinna) approximately 120,000 years ago. As a gynogenetic species, P. formosa needs to copulate with heterospecific males including males from one of its bisexual ancestral species. However, the sperm only triggers embryogenesis of the diploid eggs. The genetic information of the sperm donor typically will not contribute to the next generation of P. formosa. Hence, P. formosa possesses generally one allele from each of its ancestral species at any genetic locus. This raises the question whether both ancestral alleles are equally expressed in P. formosa. Allele-specific expression (ASE) has been previously assessed in various organisms, e.g., human and fish, and ASE was found to be important in the context of phenotypic variability and disease. In this study, we utilized Real-Time PCR techniques to estimate ASE of the androgen receptor alpha (arα) gene in several distinct tissues of Amazon mollies. We found an allelic bias favoring the maternal ancestor (P. mexicana) allele in ovarian tissue. This allelic bias was not observed in the gill or the brain tissue. Sequencing of the promoter regions of both alleles revealed an association between an Indel in a known CpG island and differential expression. Future studies may reveal whether our observed cis-regulatory divergence is caused by an ovary-specific trans-regulatory element, preferentially activating the allele of the maternal ancestor.
Alles auf (Studien)anfang!
(2017)
This study combines spaceborne multitemporal and hyperspectral data to analyze the spatial distribution of surface evaporite minerals and changes in a semi-arid depositional environment associated with episodic flooding events, the Omongwa salt pan (Kalahari, Namibia). The dynamic of the surface crust is evaluated by a change-detection approach using the Iterative-reweighted Multivariate Alteration Detection (IR-MAD) based on the Landsat archive imagery from 1984 to 2015. The results show that the salt pan is a highly dynamic and heterogeneous landform. A change gradient is observed from very stable pan border to a highly dynamic central pan. On the basis of hyperspectral EO-1 Hyperion images, the current distribution of surface evaporite minerals is characterized using Spectral Mixture Analysis (SMA). Assessment of field and image endmembers revealed that the pan surface can be categorized into three major crust types based on diagnostic absorption features and mineralogical ground truth data. The mineralogical crust types are related to different zones of surface change as well as pan morphology that influences brine flow during the pan inundation and desiccation cycles. These combined information are used to spatially map depositional environments where the more dynamic halite crust concentrates in lower areas although stable gypsum and calcite/sepiolite crusts appear in higher elevated areas.
The central aim of this thesis is to demonstrate the benefits of innovative frequency-based methods to better explain the variability observed in lake ecosystems. Freshwater ecosystems may be the most threatened part of the hydrosphere. Lake ecosystems are particularly sensitive to changes in climate and land use because they integrate disturbances across their entire catchment. This makes understanding the dynamics of lake ecosystems an intriguing and important research priority. This thesis adds new findings to the baseline knowledge regarding variability in lake ecosystems. It provides a literature-based, data-driven and methodological framework for the investigation of variability and patterns in environmental parameters in the time frequency domain.
Observational data often show considerable variability in the environmental parameters of lake ecosystems. This variability is mostly driven by a plethora of periodic and stochastic processes inside and outside the ecosystems. These run in parallel and may operate at vastly different time scales, ranging from seconds to decades. In measured data, all of these signals are superimposed, and dominant processes may obscure the signals of other processes, particularly when analyzing mean values over long time scales. Dominant signals are often caused by phenomena at long time scales like seasonal cycles, and most of these are well understood in the limnological literature. The variability injected by biological, chemical and physical processes operating at smaller time scales is less well understood. However, variability affects the state and health of lake ecosystems at all time scales. Besides measuring time series at sufficiently high temporal resolution, the investigation of the full spectrum of variability requires innovative methods of analysis.
Analyzing observational data in the time frequency domain allows to identify variability at different time scales and facilitates their attribution to specific processes. The merit of this approach is subsequently demonstrated in three case studies. The first study uses a conceptual analysis to demonstrate the importance of time scales for the detection of ecosystem responses to climate change. These responses often occur during critical time windows in the year, may exhibit a time lag and can be driven by the exceedance of thresholds in their drivers. This can only be detected if the temporal resolution of the data is high enough. The second study applies Fast Fourier Transform spectral analysis to two decades of daily water temperature measurements to show how temporal and spatial scales of water temperature variability can serve as an indicator for mixing in a shallow, polymictic lake. The final study uses wavelet coherence as a diagnostic tool for limnology on a multivariate high-frequency data set recorded between the onset of ice cover and a cyanobacteria summer bloom in the year 2009 in a polymictic lake. Synchronicities among limnological and meteorological time series in narrow frequency bands were used to identify and disentangle prevailing limnological processes.
Beyond the novel empirical findings reported in the three case studies, this thesis aims to more generally be of interest to researchers dealing with now increasingly available time series data at high temporal resolution. A set of innovative methods to attribute patterns to processes, their drivers and constraints is provided to help make more efficient use of this kind of data.
This dissertation explores whether the processing of ellipsis is affected by changes in the complexity of the antecedent, either due to added linguistic material or to the presence of a temporary ambiguity. Murphy (1985) hypothesized that ellipsis is resolved via a string copying procedure when the antecedent is within the same sentence, and that copying longer strings takes more time. Such an account also implies that the antecedent is copied without its structure, which in turn implies that recomputing its syntax and semantics may be necessary at the ellipsis gap. Alternatively, several accounts predict null effects of antecedent complexity, as well as no reparsing. These either involve a structure copying mechanism that is cost-free and whose finishing time is thus independent of the form of the antecedent (Frazier & Clifton, 2001), treat ellipsis as a pointer into content-addressable memory with direct access (Martin & McElree, 2008, 2009), or assume that one structure is ‘shared’ between antecedent and gap (Frazier & Clifton, 2005).
In a self-paced reading study on German sluicing, temporarily ambiguous garden-path clauses were used as antecedents, but no evidence of reparsing in the form of a slowdown at the ellipsis site was found. Instead, results suggest that antecedents which had been reanalyzed from an initially incorrect structure were easier to retrieve at the gap. This finding that can be explained within the framework of cue-based retrieval parsing (Lewis & Vasishth, 2005), where additional syntactic operations on a structure yield memory reactivation effects.
Two further self-paced reading studies on German bare argument ellipsis and English verb phrase ellipsis investigated if adding linguistic content to the antecedent would increase processing times for the ellipsis, and whether insufficiently demanding comprehension tasks may have been responsible for earlier null results (Frazier & Clifton, 2000; Martin & McElree, 2008). It has also been suggested that increased antecedent complexity should shorten rather than lengthen retrieval times by providing more unique memory features (Hofmeister, 2011). Both experiments failed to yield reliable evidence that antecedent complexity affects ellipsis processing times in either direction, irrespectively of task demands.
Finally, two eye-tracking studies probed more deeply into the proposed reactivation-induced speedup found in the first experiment. The first study used three different kinds of French garden-path sentences as antecedents, with two of them failing to yield evidence for reactivation. Moreover, the third sentence type showed evidence suggesting that having failed to assign a structure to the antecedent leads to a slowdown at the ellipsis site, as well as regressions towards the ambiguous part of the sentence. The second eye-tracking study used the same materials as the initial self-paced reading study on German, with results showing a pattern similar to the one originally observed, with some notable differences.
Overall, the experimental results are compatible with the view that adding linguistic material to the antecedent has no or very little effect on the ease with which ellipsis is resolved, which is consistent with the predictions of cost-free copying, pointer-based approaches and structure sharing. Additionally, effects of the antecedent’s parsing history on ellipsis processing may be due to reactivation, the availability of multiple representations in memory, or complete failure to retrieve a matching target.
Background: Malaria is an old life-threatening parasitic disease that is still affecting many people, mainly children living in sub-Saharan Africa. Availability of effective antimalarial drugs played a significant role in the treatment and control of malaria. However, recent information on the emergence of P. falciparum parasites resistant to one of the artemisinin-based combination therapies suggests the need for discovery of new drug molecules. Therefore, this study aimed to evaluate the antiplasmodial activity of extracts, fractions and isolated compound from medicinal plants traditionally used in the treatment of malaria in Tanzania.
Methods: Dry powdered plant materials were extracted by cold macerations using different solvents. Norcaesalpin D was isolated by column chromatography from dichloromethane root extract of Caesalpinia bonducella and its structure was assigned based on the spectral data. Crude extracts, fractions and isolated compound were evaluated for antiplasmodial activity against chloroquine-sensitive P. falciparum (3D7), chloroquine-resistant P. falciparum (Dd2, K1) and artemisinin-resistant P. falciparum (IPC 5202 Battambang, IPC 4912 Mondolkiri) strains using the parasite lactate dehydrogenase assay.
Results: The results indicated that extracts of Erythrina schliebenii, Holarrhena pubescens, Dissotis melleri and C. bonducella exhibited antiplasmodial activity against Dd2 parasites. Ethanolic root extract of E. schliebenii had an IC50 of 1.87 mu g/mL while methanolic and ethanolic root extracts of H. pubescens exhibited an IC50 = 2.05 mu g/mL and IC50 = 2.43 mu g/mL, respectively. Fractions from H. pubescens and C. bonducella roots were found to be highly active against K1, Dd2 and artemisinin-resistant parasites. Norcaesalpin D from C. bonducella root extract was active with IC50 of 0.98, 1.85 and 2.13 mu g/mL against 3D7, Dd2 and IPC 4912-Mondolkiri parasites, respectively.
Conclusions: Antiplasmodial activity of norcaesalpin D and extracts of E. schliebenii, H. pubescens, D. melleri and C. bonducella reported in this study requires further attention for the discovery of antimalarial lead compounds for future drug development.
Researchers have made many approaches to study the complexities of the mammalian taste system; however molecular mechanisms of taste processing in the early structures of the central taste pathway remain unclear. More recently the Arc catFISH (cellular compartment analysis of temporal activity by fluorescent in situ hybridisation) method has been used in our lab to study neural activation following taste stimulation in the first central structure in the taste pathway, the nucleus of the solitary tract. This method uses the immediate early gene Arc as a neural activity marker to identify taste-responsive neurons. Arc plays a critical role in memory formation and is necessary for conditioned taste aversion memory formation. In the nucleus of the solitary tract only bitter taste stimulation resulted in increased Arc expression, however this did not occur following stimulation with tastants of any other taste quality. The primary target for gustatory NTS neurons is the parabrachial nucleus (PbN) and, like Arc, the PbN plays an important role in conditioned taste aversion learning.
The aim of this thesis is to investigate Arc expression in the PbN following taste stimulation to elucidate the molecular identity and function of Arc expressing, taste- responsive neurons. Naïve and taste-conditioned mice were stimulated with tastants from each of the five basic taste qualities (sweet, salty, sour, umami, and bitter), with additional bitter compounds included for comparison. The expression patterns of Arc and marker genes were analysed using in situ hybridisation (ISH). The Arc catFISH method was used to observe taste-responsive neurons following each taste stimulation. A double fluorescent in situ hybridisation protocol was then established to investigate possible neuropeptide genes involved in neural responses to taste stimulation.
The results showed that bitter taste stimulation induces increased Arc expression in the PbN in naïve mice. This was not true for other taste qualities. In mice conditioned to find an umami tastant aversive, subsequent umami taste stimulation resulted in an increase in Arc expression similar to that seen in bitter-stimulated mice. Taste-responsive Arc expression was denser in the lateral PbN than the medial PbN. In mice that received two temporally separated taste stimulations, each stimulation time-point showed a distinct population of Arc-expressing neurons, with only a small population (10 – 18 %) of neurons responding to both stimulations. This suggests that either each stimulation event activates a different population of neurons, or that Arc is marking something other than simple cellular activation, such as long-term cellular changes that do not occur twice within a 25 minute time frame. Investigation using the newly established double-FISH protocol revealed that, of the bitter-responsive Arc expressing neuron population: 16 % co-expressed calcitonin RNA; 17 % co-expressed glucagon-like peptide 1 receptor RNA; 17 % co-expressed hypocretin receptor 1 RNA; 9 % co-expressed gastrin-releasing peptide RNA; and 20 % co-expressed neurotensin RNA. This co-expression with multiple different neuropeptides suggests that bitter-activated Arc expression mediates multiple neural responses to the taste event, such as taste aversion learning, suppression of food intake, increased heart rate, and involves multiple brain structures such as the lateral hypothalamus, amygdala, bed nucleus of the stria terminalis, and the thalamus.
The increase in Arc-expression suggests that bitter taste stimulation, and umami taste stimulation in umami-averse animals, may result in an enhanced state of Arc- dependent synaptic plasticity in the PbN, allowing animals to form taste-relevant memories to these aversive compounds more readily. The results investigating neuropeptide RNA co- expression suggest the amygdala, bed nucleus of the stria terminalis, and thalamus as possible targets for bitter-responsive Arc-expressing PbN neurons.
Bobrowski hatte nach dem Abitur die Absicht geäußert, Kunstgeschichte zu studieren, doch Krieg und Kriegsgefangenschaft vereitelten seinen Plan: Der Wehrmachtsangehörige wurde einzig im Winter 1941/1942 für ein Studiensemester an der Universität Berlin vom Kriegsdienst freigestellt. Nachhaltig beeindruckt war Bobrowski insbesondere von der Vorlesung „Deutsche Kunst der Goethezeit“ des Lehrstuhlinhabers Wilhelm Pinder. Trotz eines grundlegenden Einflusses ist indessen zu keinem Zeitpunkt Pinders ideologischer Hintergrund in Bobrowskis Gedichten manifest geworden. Nach der Rückkehr aus sowjetischer Gefangenschaft an Weihnachten 1949 war für den mittlerweile Zweiunddreißigjährigen an ein Studium nicht mehr zu denken. Die lebenslange intermediale Auseinandersetzung mit Werken der bildenden Kunst in seinem Œuvre kann indessen als Ausdruck seiner vielfältigen kulturgeschichtlichen Interessen und Neigungen interpretiert werden. Die Lebensphasen des Dichters korrelieren mit einer motivischen Entwicklung seiner Bildgedichte: Insbesondere half ihm die unantastbare Ästhetik bedeutender Kunstwerke, das Grauen der letzten Kriegsjahre und die Entbehrungen in sowjetischer Kriegsgefangenschaft zu überwinden. Didaktisch-moralische Zielsetzungen prägten zunächst die in den Jahren nach seiner Heimkehr entstandenen Gedichte, bevor sich Bobrowski inhaltlich und formal von diesem Gedichttypus zu lösen vermochte und vermehrt Gedichte zu schreiben begann, die kulturgeschichtliche Dimensionen annahmen und historische, mythologische, biblische und religionsphilosophische Themen in epochenübergreifende Zusammenhänge stellten. Die Gedichte über die Künstler Jawlensky und Calder berühren gleichzeitig kulturlandschaftliche Aspekte. Im letzten Lebensjahrzehnt interessierte sich Bobrowski zunehmend für die Kunst des 20. Jahrhunderts, während die moderne Architektur aus seinem Werk ausgeklammert blieb.
Architektur bildet eine Leitmotivik in Bobrowskis lyrischem Werk. Die übertragene Bedeutungsebene der in den Gedichten benannten sakralen und profanen Einzelbauten, aber auch der städtischen und dörflichen Ensembles sowie einzelner Gebäudeteile, verändert sich mehrfach im Laufe der Jahre. Ausgehend von traditionellen, paargereimten Jugendgedichten in jambischem Versmaß, in denen architektonische Elemente Teil einer Wahrnehmung bilden, die alles Außerästhetische ausblendet, wandelt sich der Sinngehalt der Sakral- und Profanbauten in Bobrowskis lyrischem Werk ein erstes Mal während den Kriegsjahren in Russland, die der Wehrmachtsangehörige am Ilmensee verbracht hat. In den damals entstandenen Oden zeugen die architektonischen Relikte von Leid, Tod und Zerstörung. Noch fehlt indessen der später so zentrale Gedanke der Schuld, der erst im Rückblick auf jene Zeit in den Gedichten, die nach der Rückkehr aus der Kriegsgefangenschaft bis zu Bobrowskis frühem Tod entstanden sind, thematisiert worden ist.
Gegen Ende des Kriegs und in den Jahren der Kriegsgefangenschaft besinnt sich Bobrowski erneut auf Heimatthemen, und die Architektur in seinen Gedichten wird zu einem ästhetisch überhöhten Fluchtpunkt seiner Sehnsucht nach Ostpreußen und dem Memelgebiet. In Kriegsgefangenschaft tritt erstmals der Aspekt des Sublimen in seinen Gedichten auf, und zwar sowohl bezogen auf die Malerei als auch auf die Architektur. Dieser Gedanke wird einerseits nach der Rückkehr nach Berlin in den Gedichten über die Architektur gotischer Kathedralen und das bauliche Erbe des Klassizismus weitergesponnen, doch steht in den damals entstandenen Gedichten das Kulturerbe Europas auch für historisches Unrecht und eine schwere, weit zurückreichende Schuld.
Von dieser auf den ganzen Kontinent bezogenen Kritik wendet sich Bobrowski in den nachfolgenden Jahren ab und konzentriert sich auf die Schuld der Deutschen gegenüber den Völkern Osteuropas. Damit erhält auch die Architektur in seinen Gedichten eine neue Bedeutung. Die Relikte der Ritterburgen des deutschen Ordens zeugen von der Herrschaft der mittelalterlichen Eroberer und verschmelzen dabei mit der Natur: Das Zeichenhafte der Architektur wird Teil der Landschaft. Im letzten Lebensjahrzehnt entstehen vermehrt Gedichte, die sich auf Parkanlagen und städtische Grünräume beziehen.
Der Dichter hat sich nicht nur auf persönliche Erfahrungen, sondern mitunter auch auf Bildquellen abstützt, ohne dass er das Original je gesehen hätte. Nur schwer zugänglich sind die Gedichte über Chagall und Gauguin ohne die Erkenntnis, dass sie sich auf Bildvorlagen in schmalen, populärwissenschaftlichen Büchern beziehen, die Bobrowski jeweils kurz vor der Niederschrift der entsprechenden Gedichte erworben hat. Anders verhält es sich mit jenen russischen Kirchen, die Eingang in sein lyrisches Werk gefunden haben. Bobrowski hat sie alle selbst im Krieg gesehen, und die meisten scheinen noch heute zu bestehen und können mit einiger Sicherheit identifiziert werden, wozu auch die Briefe des Dichters aus jener Zeit beitragen.
Background
In isometric muscle function, there are subjectively two different modes of performance: one can either hold isometrically – thus resist an impacting force – or push isometrically – therefore work against a stable resistance. The purpose of this study is to investigate whether or not two different isometric muscle actions – the holding vs. pushing one (HIMA vs PIMA) – can be distinguished by objective parameters.
Methods
Ten subjects performed two different measuring modes at 80% of MVC realized by a special pneumatic system. During HIMA the subject had to resist the defined impacting force of the pneumatic system in an isometric position, whereby the force of the cylinder works in direction of elbow flexion against the subject. During PIMA the subject worked isometrically in direction of elbow extension against a stable position of the system. The signals of pressure, force, acceleration and mechanomyography/-tendography (MMG/MTG) of the elbow extensor (MMGtri/MTGtri) and the abdominal muscle (MMGobl) were recorded and evaluated concerning the duration of maintaining the force level (force endurance) and the characteristics of MMG-/MTG-signals. Statistical group differences comparing HIMA vs. PIMA were estimated using SPSS.
Results
Significant differences between HIMA and PIMA were especially apparent regarding the force endurance: During HIMA the subjects showed a decisively shorter time of stable isometric position (19 ± 8 s) in comparison with PIMA (41 ± 24 s; p = .005). In addition, during PIMA the longest isometric plateau amounted to 59.4% of the overall duration time of isometric measuring, during HIMA it lasted 31.6% (p = .000). The frequency of MMG/MTG did not show significant differences. The power in the frequency ranges of 8–15 Hz and 10–29 Hz was significantly higher in the MTGtri performing HIMA compared to PIMA (but not for the MMGs). The amplitude of MMG/MTG did not show any significant difference considering the whole measurement. However, looking only at the last 10% of duration time (exhaustion), the MMGtri showed significantly higher amplitudes during PIMA.
Conclusion
The results suggest that under holding isometric conditions muscles exhaust earlier. That means that there are probably two forms of isometric muscle action. We hypothesize two potential reasons for faster yielding during HIMA: (1) earlier metabolic fatigue of the muscle fibers and (2) the complexity of neural control strategies.