TY - JOUR
A1 - Binder, Julia
A1 - Mettenberger, Tobias
T1 - Schlüsselfiguren in ländlichen Netzwerken
JF - KWI-Schriften
KW - Schlüsselfiguren
KW - ländliche Räume
KW - Netzwerk
KW - Akteure
KW - Pioniere
KW - leader
KW - rural areas
KW - network
KW - actor
KW - pioneer
Y1 - 2023
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-631133
SN - 978-3-86956-571-2
SN - 1867-951X
SN - 1867-9528
IS - 14
SP - 39
EP - 50
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - JOUR
A1 - Bembnista, Kamil
A1 - Mettenberger, Tobias
A1 - Zscherneck, Julia
T1 - Soziale Netzwerke als Ressourcenzugänge für Digitale Pioniere
JF - KWI-Schriften
KW - Netzwerk
KW - soziales Netzwerk
KW - Ressource
KW - Digitalisierung
KW - Pioniere
KW - Akteure
KW - network
KW - social network
KW - resource
KW - digitalization
KW - pioneer
KW - actor
Y1 - 2023
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-631156
SN - 978-3-86956-571-2
SN - 1867-951X
SN - 1867-9528
IS - 14
SP - 51
EP - 72
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - JOUR
A1 - Rosenblum, Michael
A1 - Pikovsky, Arkady
T1 - Inferring connectivity of an oscillatory network via the phase dynamics reconstruction
JF - Frontiers in network physiology
N2 - We review an approach for reconstructing oscillatory networks’ undirected and directed connectivity from data. The technique relies on inferring the phase dynamics model. The central assumption is that we observe the outputs of all network nodes. We distinguish between two cases. In the first one, the observed signals represent smooth oscillations, while in the second one, the data are pulse-like and can be viewed as point processes. For the first case, we discuss estimating the true phase from a scalar signal, exploiting the protophase-to-phase transformation. With the phases at hand, pairwise and triplet synchronization indices can characterize the undirected connectivity. Next, we demonstrate how to infer the general form of the coupling functions for two or three oscillators and how to use these functions to quantify the directional links. We proceed with a different treatment of networks with more than three nodes. We discuss the difference between the structural and effective phase connectivity that emerges due to high-order terms in the coupling functions. For the second case of point-process data, we use the instants of spikes to infer the phase dynamics model in the Winfree form directly. This way, we obtain the network’s coupling matrix in the first approximation in the coupling strength.
KW - oscillations
KW - network
KW - connectivity
KW - data analysis
KW - phase reduction
Y1 - 2023
U6 - https://doi.org/10.3389/fnetp.2023.1298228
SN - 2674-0109
VL - 3
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Lehr, Christian
A1 - Lischeid, Gunnar
T1 - Efficient screening of groundwater head monitoring data for anthropogenic effects and measurement errors
JF - Hydrology and Earth System Sciences
N2 - Groundwater levels are monitored by environmental agencies to support the sustainable use of groundwater resources. For this purpose continuous and spatially comprehensive monitoring in high spatial and temporal resolution is desired. This leads to large datasets that have to be checked for quality and analysed to distinguish local anthropogenic influences from natural variability of the groundwater level dynamics at each well. Both technical problems with the measurements as well as local anthropogenic influences can lead to local anomalies in the hydrographs. We suggest a fast and efficient screening method for the identification of well-specific peculiarities in hydrographs of groundwater head monitoring networks. The only information required is a set of time series of groundwater heads all measured at the same instants of time. For each well of the monitoring network a reference hydrograph is calculated, describing expected "normal" behaviour at the respective well as is typical for the monitored region. The reference hydrograph is calculated by multiple linear regression of the observed hydrograph with the "stable" principal components (PCs) of a principal component analysis of all groundwater head series of the network as predictor variables. The stable PCs are those PCs which were found in a random subsampling procedure to be rather insensitive to the specific selection of the analysed observation wells, i.e. complete series, and to the specific selection of measurement dates. Hence they can be considered to be representative for the monitored region in the respective period. The residuals of the reference hydrograph describe local deviations from the normal behaviour. Peculiarities in the residuals allow the data to be checked for measurement errors and the wells with a possible anthropogenic influence to be identified. The approach was tested with 141 groundwater head time series from the state authority groundwater monitoring network in northeastern Germany covering the period from 1993 to 2013 at an approximately weekly frequency of measurement.
KW - streamflow variability
KW - principal components
KW - united states
KW - time-seriesa
KW - water
KW - network
KW - nonstationarity
KW - fluctuations
KW - rotation
Y1 - 2020
U6 - https://doi.org/10.5194/hess-24-501-2020
SN - 1027-5606
SN - 1607-7938
VL - 24
IS - 2
SP - 501
EP - 513
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Crawford, Tim
A1 - Karamat, Fazeelat
A1 - Lehotai, Nóra
A1 - Rentoft, Matilda
A1 - Blomberg, Jeanette
A1 - Strand, Åsa
A1 - Björklund, Stefan
T1 - Specific functions for mediator complex subunits from different modules in the transcriptional response of arabidopsis thaliana to abiotic stress
JF - Scientific reports
N2 - Adverse environmental conditions are detrimental to plant growth and development. Acclimation to abiotic stress conditions involves activation of signaling pathways which often results in changes in gene expression via networks of transcription factors (TFs). Mediator is a highly conserved co-regulator complex and an essential component of the transcriptional machinery in eukaryotes. Some Mediator subunits have been implicated in stress-responsive signaling pathways; however, much remains unknown regarding the role of plant Mediator in abiotic stress responses. Here, we use RNA-seq to analyze the transcriptional response of Arabidopsis thaliana to heat, cold and salt stress conditions. We identify a set of common abiotic stress regulons and describe the sequential and combinatorial nature of TFs involved in their transcriptional regulation. Furthermore, we identify stress-specific roles for the Mediator subunits MED9, MED16, MED18 and CDK8, and putative TFs connecting them to different stress signaling pathways. Our data also indicate different modes of action for subunits or modules of Mediator at the same gene loci, including a co-repressor function for MED16 prior to stress. These results illuminate a poorly understood but important player in the transcriptional response of plants to abiotic stress and identify target genes and mechanisms as a prelude to further biochemical characterization.
KW - regulate gene expression
KW - signal transduction
KW - circadian clock
KW - plant Mediator
KW - salicylic-acid
KW - activation
KW - jasmonate
KW - network
KW - defense
KW - MED16
Y1 - 2020
U6 - https://doi.org/10.1038/s41598-020-61758-w
SN - 2045-2322
VL - 10
IS - 1
SP - 1
EP - 18
PB - Macmillan Publishers Limited, part of Springer Nature
CY - London
ER -
TY - JOUR
A1 - Wilhelmi, Ilka
A1 - Grunwald, Stephan
A1 - Gimber, Niclas
A1 - Popp, Oliver
A1 - Dittmar, Gunnar
A1 - Arumughan, Anup
A1 - Wanker, Erich E.
A1 - Laeger, Thomas
A1 - Schmoranzer, Jan
A1 - Daumke, Oliver
A1 - Schürmann, Annette
T1 - The ARFRP1-dependent Golgi scaffolding protein GOPC is required for insulin secretion from pancreatic 13-cells
JF - Molecular metabolism
N2 - Objective: Hormone secretion from metabolically active tissues, such as pancreatic islets, is governed by specific and highly regulated signaling pathways. Defects in insulin secretion are among the major causes of diabetes. The molecular mechanisms underlying regulated insulin secretion are, however, not yet completely understood. In this work, we studied the role of the GTPase ARFRP1 on insulin secretion from pancreatic 13-cells.
Methods: A 13-cell-specific Arfrp1 knockout mouse was phenotypically characterized. Pulldown experiments and mass spectrometry analysis were employed to screen for new ARFRP1-interacting proteins. Co-immunoprecipitation assays as well as super-resolution microscopy were applied for validation.
Results: The GTPase ARFRP1 interacts with the Golgi-associated PDZ and coiled-coil motif-containing protein (GOPC). Both proteins are co localized at the trans-Golgi network and regulate the first and second phase of insulin secretion by controlling the plasma membrane localization of the SNARE protein SNAP25. Downregulation of both GOPC and ARFRP1 in Min6 cells interferes with the plasma membrane localization of SNAP25 and enhances its degradation, thereby impairing glucose-stimulated insulin release from 13-cells. In turn, overexpression of SNAP25 as well as GOPC restores insulin secretion in islets from 13-cell-specific Arfrp1 knockout mice.
Conclusion: Our results identify a hitherto unrecognized pathway required for insulin secretion at the level of trans-Golgi sorting. (c) 2020 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
KW - Insulin secretion
KW - Endosomal sorting
KW - SNARE proteins
KW - trans-Golgi
KW - network
Y1 - 2020
U6 - https://doi.org/10.1016/j.molmet.2020.101151
SN - 2212-8778
VL - 45
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Fritz, Amelie
A1 - Makeyeva, Angelina
A1 - Staub, Kaspar
A1 - Groth, Detlef
T1 - Influence of network properties on a migration induced secular height trend by Monte Carlo simulation
JF - Journal of biological and clinical anthropology : Anthropologischer Anzeiger ; Mitteilungsorgan der Gesellschaft für Anthropologie
N2 - Background: Recent research reported height biased migration of taller individuals and a Monte Carlo simulation showed that such preferential migration of taller individuals into network hubs can induce a secular trend of height. In the simulation model taller agents in the hubs raise the overall height of all individuals in the network by a community effect. However, it could be seen that the actual network structure influences the strength of this effect. In this paper the background and the influence of the network structure on the strength of the secular trend by migration is investigated. Material and methods: Three principal network types are analyzed: networks derived from street connections in Switzerland, more regular fishing net like networks and randomly generated ones. Our networks have between 10 and 152 nodes and between 20 and 307 edges connecting the nodes. Depending on the network size between 5.000 and 90.000 agents with an average height of 170 cm (SD 6.5 cm) are initially released into the network. In each iteration new agents are regenerated based on the actual average body height of the previous iteration and, to a certain proportion, corrected by body heights in the neighboring nodes. After generating new agents, a certain number of them migrated into neighbor nodes, the model let preferentially taller agents migrate into network hubs. Migration is balanced by back migration of the same number of agents from nodes with high centrality measures to less connected nodes. The latter is random as well, but not biased by the agents height. Furthermore the distribution of agents per node and their correlation to the centrality of the nodes is varied in a systematic manner. After 100 iterations, the secular trend, i.e. the gain in body height for the different networks, is investigated in relation to the network properties. Results: We observe an increase of average agent body height after 100 iterations if height biased migration is enabled. The increase rate depends on the height of the neighboring factor, the population distribution, the relationship between population in the nodes and their centrality as well as on the network topology. Networks with uniform like distributions of the agents in the nodes, uncorrelated associations between node centrality and agent number per node, as well as very heterogeneous networks with very different node centralities lead to biggest gains in average body height. Conclusion: Our simulations show, that height biased migration into network hubs can possibly contribute to the secular trend of height increase in the human population. The strength of this "tall by migration" event depends on the actual properties of the underlying network. There is a possible significance of this mechanism for social networks, when hubs are represented by individuals and edges as their personal relationships. However, the required high number of iterations to achieve significant effects in more natural network structures in our models requires further studies to test the relevance and real effect sizes in real world scenarios.
KW - secular trend
KW - body height
KW - simulation
KW - community effect
KW - Monte Carlo method
KW - network
KW - centrality measures
Y1 - 2019
U6 - https://doi.org/10.1127/anthranz/2019/1032
SN - 0003-5548
VL - 76
IS - 5
SP - 433
EP - 443
PB - Schweizerbart
CY - Stuttgart
ER -
TY - JOUR
A1 - Distelmeyer, Jan
T1 - From object to process
BT - Interface politics of networked computerization
JF - Artnodes
N2 - One of the most difficult tasks today is trying to grasp the presence of computing. The almost ubiquitous and diverse forms of networked computers (in all their stationary, mobile, embedded, and autonomous modes) create a nearly overwhelming complexity. To speak of what is here evading and present at the same time, the paper proposes to reconsider the concept of interface, its historical roots, and its heuristic advantages for an analysis and critique of the current and especially everyday spread of computerization. The question of interfaces leads to isolable conditions and processes of conduction, as well as to the complexity of the cooperation formed by them. It opens both an investigative horizon and a mode of analysis, which always asks for further interface levels involved in the phenomenon I am currently investigating. As an example, the paper turns to the displacement of the file with the launch of the iPhone in 2007 and its comeback in 2017 with the "Files" apps. Both developments are profoundly related to the establishment of computers as permanently networked machines, whereby their functionality, depresentations, and ideology come into focus.
KW - interface
KW - conduction
KW - network
KW - ideology
KW - depresentation
KW - digital objects
Y1 - 2019
U6 - https://doi.org/10.7238/a.v0i24.3300
SN - 1695-5951
IS - 24
SP - 83
EP - 90
PB - Universitat Oberta de Catalunya
CY - Barcelona
ER -
TY - JOUR
A1 - Jelken, Joachim
A1 - Santer, Svetlana
T1 - Light induced reversible structuring of photosensitive polymer films
JF - RSC Advances
N2 - In this paper we report on photoswitchable polymer surfaces with dynamically and reversibly fluctuating topographies. It is well known that when azobenzene containing polymer films are irradiated with optical interference patterns the film topography changes to form a surface relief grating. In the simplest case, the film shape mimics the intensity distribution and deforms into a wave like, sinusoidal manner with amplitude that may be as large as the film thickness. This process takes place in the glassy state without photo-induced softening. Here we report on an intriguing discovery regarding the formation of reliefs under special illumination conditions. We have developed a novel setup combining the optical part for creating interference patterns, an AFM for in situ acquisition of topography changes and diffraction efficiency signal measurements. In this way we demonstrate that these gratings can be “set in motion” like water waves or dunes in the desert. We achieve this by applying repetitive polarization changes to the incoming interference pattern. Such light responsive surfaces represent the prerequisite for providing practical applications ranging from conveyer or transport systems for adsorbed liquid objects and colloidal particles to generation of adaptive and dynamic optical devices.
KW - surface-relief gratings
KW - induced deformation
KW - mass-transport
KW - azobenzene elastomers
KW - thin-films
KW - birefringence
KW - roughness
KW - network
KW - erasure
Y1 - 2019
U6 - https://doi.org/10.1039/C9RA02571E
SN - 2046-2069
VL - 9
IS - 35
SP - 20295
EP - 20305
PB - RSC Publishing
CY - London
ER -
TY - JOUR
A1 - Groth, Detlef
T1 - Modeling a secular trend by Monte Carlo simulation of height biased migration in a spatial network
JF - Anthropologischer Anzeiger : journal of biological and clinical anthropology ; Mitteilungsorgan der Gesellschaft für Anthropologie
N2 - Background: In a recent Monte Carlo simulation, the clustering of body height of Swiss military conscripts within a spatial network with characteristic features of the natural Swiss geography was investigated. In this study I examined the effect of migration of tall individuals into network hubs on the dynamics of body height within the whole spatial network. The aim of this study was to simulate height trends. Material and methods: Three networks were used for modeling, a regular rectangular fishing net like network, a real world example based on the geographic map of Switzerland, and a random network. All networks contained between 144 and 148 districts and between 265-307 road connections. Around 100,000 agents were initially released with average height of 170 cm, and height standard deviation of 6.5 cm. The simulation was started with the a priori assumption that height variation within a district is limited and also depends on height of neighboring districts (community effect on height). In addition to a neighborhood influence factor, which simulates a community effect, body height dependent migration of conscripts between adjacent districts in each Monte Carlo simulation was used to re-calculate next generation body heights. In order to determine the direction of migration for taller individuals, various centrality measures for the evaluation of district importance within the spatial network were applied. Taller individuals were favored to migrate more into network hubs, backward migration using the same number of individuals was random, not biased towards body height. Network hubs were defined by the importance of a district within the spatial network. The importance of a district was evaluated by various centrality measures. In the null model there were no road connections, height information could not be delivered between the districts. Results: Due to the favored migration of tall individuals into network hubs, average body height of the hubs, and later, of the whole network increased by up to 0.1 cm per iteration depending on the network model. The general increase in height within the network depended on connectedness and on the amount of height information that was exchanged between neighboring districts. If higher amounts of neighborhood height information were exchanged, the general increase in height within the network was large (strong secular trend). The trend in the homogeneous fishnet like network was lowest, the trend in the random network was highest. Yet, some network properties, such as the heteroscedasticity and autocorrelations of the migration simulation models differed greatly from the natural features observed in Swiss military conscript networks. Autocorrelations of district heights for instance, were much higher in the migration models. Conclusion: This study confirmed that secular height trends can be modeled by preferred migration of tall individuals into network hubs. However, basic network properties of the migration simulation models differed greatly from the natural features observed in Swiss military conscripts. Similar network-based data from other countries should be explored to better investigate height trends with Monte Carlo migration approach.
KW - secular trend
KW - body height
KW - simulation
KW - community effect
KW - Monte Carlo method
KW - network
Y1 - 2017
U6 - https://doi.org/10.1127/anthranz/2017/0703
SN - 0003-5548
SN - 2363-7099
VL - 74
IS - 1
SP - 81
EP - 88
PB - Schweizerbart
CY - Stuttgart
ER -