Showing papers by "University of Potsdam published in 2005"

Determinants of woody cover in African savannas

Abstract: Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties1–3. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover1,2,4,5, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than ,650mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered ‘stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of ,650mm, savannas are ‘unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation6 may considerably affect their distribution and dynamics.

SWIFT: a dynamical model of saccade generation during reading.

Abstract: Mathematical models have become an important tool for understanding the control of eye movements during reading. Main goals of the development of the SWIFT model (R. Engbert, A. Longtin, & R. Kliegl, 2002) were to investigate the possibility of spatially distributed processing and to implement a general mechanism for all types of eye movements observed in reading experiments. The authors present an advanced version of SWIFT that integrates properties of the oculomotor system and effects of word recognition to explain many of the experimental phenomena faced in reading research. They propose new procedures for the estimation of model parameters and for the test of the model's performance. They also present a mathematical analysis of the dynamics of the SWIFT model. Finally, within this framework, they present an analysis of the transition from parallel to serial processing.

Constraints on the evolution of adaptive phenotypic plasticity in plants

Abstract: The high potential fitness benefit of phenotypic plasticity tempts us to expect phenotypic plasticity as a frequent adaptation to environmental heterogeneity. Examples of proven adaptive plasticity in plants, however, are scarce and most plastic responses actually may be 'passive' rather than adaptive. This suggests that frequently requirements for the evolution of adaptive plasticity are not met or that such evolution is impeded by constraints. Here we outline requirements and potential constraints for the evolution of adaptive phenotypic plasticity, identify open questions, and propose new research approaches. Important open questions concern the genetic background of plasticity, genetic variation in plasticity, selection for plasticity in natural habitats, and the nature and occurrence of costs and limits of plasticity. Especially promising tools to address these questions are selection gradient analysis, meta-analysis of studies on genotype-by-environment interactions, QTL analysis, cDNA-microarray scanning and quantitative PCR to quantify gene expression, and two-dimensional gel electrophoresis to quantify protein expression. Studying plasticity along the pathway from gene expression to the phenotype and its relationship with fitness will help us to better understand why adaptive plasticity is not more universal, and to more realistically predict the evolution of plastic responses to environmental change.

Spatio-spectral filters for improving the classification of single trial EEG

Abstract: Data recorded in electroencephalogram (EEG)-based brain-computer interface experiments is generally very noisy, nonstationary, and contaminated with artifacts that can deteriorate discrimination/classification methods. In this paper, we extend the common spatial pattern (CSP) algorithm with the aim to alleviate these adverse effects. In particular, we suggest an extension of CSP to the state space, which utilizes the method of time delay embedding. As we will show, this allows for individually tuned frequency filters at each electrode position and, thus, yields an improved and more robust machine learning procedure. The advantages of the proposed method over the original CSP method are verified in terms of an improved information transfer rate (bits per trial) on a set of EEG-recordings from experiments of imagined limb movements.

Scenarios of freshwater fish extinctions from climate change and water withdrawal

Abstract: Reductions in river discharge (water availability) like those from climate change or increased water withdrawal, reduce freshwater biodiversity. We combined two scenarios from the Intergovernmental Panel for Climate Change with a global hydrological model to build global scenarios of future losses in river discharge from climate change and increased water withdrawal. Applying these results to known relationships between fish species and discharge, we build scenarios of losses (at equilibrium) of riverine fish richness. In rivers with reduced discharge, up to 75% (quartile range 4–22%) of local fish biodiversity would be headed toward extinction by 2070 because of combined changes in climate and water consumption. Fish loss in the scenarios fell disproportionately on poor countries. Reductions in water consumption could prevent many of the extinctions in these scenarios.

Network synchronization, diffusion, and the paradox of heterogeneity.

Abstract: Many complex networks display strong heterogeneity in the degree (connectivity) distribution. Heterogeneity in the degree distribution often reduces the average distance between nodes but, paradoxically, may suppress synchronization in networks of oscillators coupled symmetrically with uniform coupling strength. Here we offer a solution to this apparent paradox. Our analysis is partially based on the identification of a diffusive process underlying the communication between oscillators and reveals a striking relation between this process and the condition for the linear stability of the synchronized states. We show that, for a given degree distribution, the maximum synchronizability is achieved when the network of couplings is weighted and directed and the overall cost involved in the couplings is minimum. This enhanced synchronizability is solely determined by the mean degree and does not depend on the degree distribution and system size. Numerical verification of the main results is provided for representative classes of small-world and scale-free networks.

Tracking the mind during reading: The influence of past, present, and future words on fixation durations

Abstract: Reading requires the orchestration of visual, attentional, language-related, and oculomotor processing constraints. This study replicates previous effects of frequency, predictability, and length of fixated words on fixation durations in natural reading and demonstrates new effects of these variables related to previous and next words. Results are based on fixation durations recorded from 222 persons, each reading 144 sentences. Such evidence for distributed processing of words across fixation durations challenges psycholinguistic immediacy-of-processing and eye-mind assumptions. Most of the time the mind processes several words in parallel at different perceptual and cognitive levels. Eye movements can help to unravel these processes. Reading is a fairly recent cultural invention. The perceptual, attentional, and oculomotor processes enabling this remarkable and complex human skill had been in place for a long time before the first sentence was read. Of course, reading also fundamentally presupposes language, reasoning, and memory processes. If we want to understand how internal processes of the mind and exter- nal stimuli play together in the generation of complex action, reading may serve as an ideal sample case, because, despite its complexity, it occurs in settings that are very amenable to exper- imental control. In addition, the measurement of eye movements yields high-resolution time series that have proven to be very sensitive to factors at all levels of the behavioral and cognitive hierarchy. Most important, we already know or can determine basic perceptual, attentional, and oculomotor constraints that any theory of reading and any computational model implementing such a theory at a behavioral microlevel must respect. Looking at the eyes, reading proceeds as an alternating sequence of fixations (lasting 150 to 300 ms) and saccades (30 ms). Infor- mation uptake is largely restricted to fixations. For example, fixation durations reliably decrease with the printed frequency of words and with their predictability from prior words of the sen- tence. Beyond these uncontroversial facts, however, much still needs to be learned about perceptual and attentional processes and properties of words that guide the eyes through a sentence. Starr and Rayner (2001, p. 156) highlighted the following three issues as particularly controversial: 1. The extent to which eye-movement behavior is affected by low-level oculomotor factors versus higher-level cog- nitive processes. 2. How much information is extracted from the right of fixations. 3. Whether readers process information from more than one word at a time. In this article, we report new empirical results relating to each of these issues. We also present a data-analytic framework within which these issues can be addressed simultaneously and propose a set of theoretical principles that account for a complex set of experimental observations. Basically, in our analysis of reading fixations we show that most of the time the mind processes several words in parallel at different perceptual and cognitive levels. Similar dynamical and parallel effects of perceptual and attentional modulation guide human gaze control during real-word scene perception and interpretation (e.g., Henderson, 2005). A future challenge is to use the potential of eye movements as prime indicators of these general cognitive and behavioral dynamics.

Entropy, entanglement, and area: analytical results for harmonic lattice systems

Abstract: We revisit the question of the relation between entanglement, entropy, and area for harmonic lattice Hamiltonians corresponding to discrete versions of real free Klein-Gordon fields. For the ground state of the d-dimensional cubic harmonic lattice we establish a strict relationship between the surface area of a distinguished hypercube and the degree of entanglement between the hypercube and the rest of the lattice analytically, without resorting to numerical means. We outline extensions of these results to longer ranged interactions, finite temperatures, and for classical correlations in classical harmonic lattice systems. These findings further suggest that the tools of quantum information science may help in establishing results in quantum field theory that were previously less accessible.

Working Memory and Intelligence—Their Correlation and Their Relation: Comment on Ackerman, Beier, and Boyle (2005)

Abstract: Onthebasisofameta-analysisofpairwisecorrelationsbetweenwork- ing memory tasks and cognitive ability measures, P. L. Ackerman, M. E. Beier, and M. O. Boyle (2005) claimed that working memory capacity (WMC) shares less than 25% of its variance with general intelligence (g) and with reasoning ability. In this comment, the authors argue that this is an underestimation because of several methodological shortcomings and biases. A reanalysis of the data reported in Ack- erman et al. using the correct statistical procedures demonstrates that g and WMC are very highly correlated. On a conceptual level, the authors point out that WMC should be regarded as an explanatory construct for intellectual abilities. Theories of working memory do not claim that WMC is isomorphic with intelligence factors but that it is a very strong predictor of reasoning ability and also predicts general fluid intelligence and g.

Binding and inhibition in working memory: individual and age differences in short-term recognition.

Abstract: Two studies investigated the relationship between working memory capacity (WMC), adult age, and the resolution of conflict between familiarity and recollection in short-term recognition tasks. Experiment 1 showed a specific deficit of young adults with low WMC in rejecting intrusion probes (i.e., highly familiar probes) in a modified Sternberg task, which was similar to the deficit found in old adults in a parallel experiment (K. Oberauer, 2001). Experiment 2 generalized these results to 3 recognition paradigms (modified Sternberg, local recognition, and n back tasks). Old adults showed disproportional performance deficits on intrusion probes only in terms of reaction times, whereas young adults with low WMC showed them only in terms of errors. The generality of the effect across paradigms is more compatible with a deficit in content-context bindings subserving recollection than with a deficit in inhibition of irrelevant information in working memory. Structural equation models showed that WMC is related to the efficiency of recollection but not of familiarity.

Large magnetoresistance in nonmagnetic π -conjugated semiconductor thin film devices

Abstract: Following the recent observation of large magnetoresistance at room temperature in polyfluorene sandwich devices, we have performed a comprehensive magnetoresistance study on a set of organic semiconductor sandwich devices made from different $\ensuremath{\pi}$-conjugated polymers and small molecules The study includes a range of materials that show greatly different chemical structure, mobility, and spin-orbit coupling strength We study both hole and electron transporters at temperatures ranging from 10 K to 300 K We observe large negative or positive magnetoresistance (up to 10% at 300 K and 10 mT) depending on material and device operating conditions We discuss our results in the framework of known magnetoresistance mechanisms and find that none of the existing models can explain our results

Late Quaternary intensified monsoon phases control landscape evolution in the northwest Himalaya

Abstract: The intensity of the Asian summer-monsoon circulation varies over decadal to millennial time scales and is reflected in changes in surface processes, terrestrial environments, and marine sedi- ment records. However, the mechanisms of long-lived (2-5 k.y.) intensified monsoon phases, the related changes in precipitation distribution, and their effect on landscape evolution and sedimen- tation rates are not yet well understood. The arid high-elevation sectors of the orogen correspond to a climatically sensitive zone that currently receives rain only during abnormal (i.e., strength- ened) monsoon seasons. Analogous to present-day rainfall anom- alies, enhanced precipitation during an intensified monsoon phase is expected to have penetrated far into these geomorphic threshold regions where hillslopes are close to the angle of failure. We as- sociate landslide triggering during intensified monsoon phases with enhanced precipitation, discharge, and sediment flux leading to an increase in pore-water pressure, lateral scouring of rivers, and ov- ersteepening of hillslopes, eventually resulting in failure of slopes and exceptionally large mass movements. Here we use lacustrine deposits related to spatially and temporally clustered large land- slides (.0.5 km 3 ) in the Sutlej Valley region of the northwest Him- alaya to calculate sedimentation rates and to infer rainfall patterns during late Pleistocene (29-24 ka) and Holocene (10-4 ka) inten- sified monsoon phases. Compared to present-day sediment-flux measurements, a fivefold increase in sediment-transport rates re- corded by sediments in landslide-dammed lakes characterized these episodes of high climatic variability. These changes thus em- phasize the pronounced imprint of millennial-scale climate change on surface processes and landscape evolution.

Enhancing complex-network synchronization

Abstract: Heterogeneity in the degree (connectivity) distribution has been shown to suppress synchronization in networks of symmetrically coupled oscillators with uniform coupling strength (unweighted coupling). Here we uncover a condition for enhanced synchronization in weighted networks with asymmetric coupling. We show that, in the optimum regime, synchronizability is solely determined by the average degree and does not depend on the system size and the details of the degree distribution. In scale-free networks, where the average degree may increase with heterogeneity, synchronizability is drastically enhanced and may become positively correlated with heterogeneity, while the overall cost involved in the network coupling is significantly reduced as compared to the case of unweighted coupling.

Quantum information processing and communication: strategic report on current status, visions and goals for research in Europe

Abstract: We present an excerpt of the document "Quantum Information Processing and Communication: Strategic report on current status, visions and goals for research in Europe", which has been recently published in electronic form at the website of FET (the Future and Emerging Technologies Unit of the Directorate General Information Society of the European Commission, http://www.cordis.lu/ist/fet/qipc-sr.htm). This document has been elaborated, following a former suggestion by FET, by a committee of QIPC scientists to provide input towards the European Commission for the preparation of the Seventh Framework Program. Besides being a document addressed to policy makers and funding agencies (both at the European and national level), the document contains a detailed scientific assessment of the state-of-the-art, main research goals, challenges, strengths, weaknesses, visions and perspectives of all the most relevant QIPC sub-fields, that we report here.

On the Use of Logic Trees for Ground-Motion Prediction Equations in Seismic-Hazard Analysis

Abstract: Logic trees are widely used in probabilistic seismic hazard analysis as a tool to capture the epistemic uncertainty associated with the seismogenic sources and the ground-motion prediction models used in estimating the hazard. Combining two or more ground-motion relations within a logic tree will generally require several conversions to be made, because there are several definitions available for both the predicted ground-motion parameters and the explanatory parameters within the predictive ground-motion relations. Procedures for making conversions for each of these factors are presented, using a suite of predictive equations in current use for illustration. The sensitivity of the resulting ground-motion models to these conversions is shown to be pronounced for some of the parameters, especially the measure of source-to-site distance, highlighting the need to take into account any incompatibilities among the selected equations. Procedures are also presented for assigning weights to the branches in the ground-motion section of the logic tree in a transparent fashion, considering both intrinsic merits of the individual equations and their degree of applicability to the particular application.

Late Cenozoic Moisture History of East Africa

Abstract: Lake sediments in 10 Ethiopian, Kenyan, and Tanzanian rift basins suggest that there were three humid periods at 2.7 to 2.5 million years ago (Ma), 1.9 to 1.7 Ma, and 1.1 to 0.9 Ma, superimposed on the longer-term aridification of East Africa. These humid periods correlate with increased aridity in northwest and northeast Africa and with substantial global climate transitions. These episodes could have had important impacts on the speciation and dispersal of mammals and hominins, because a number of key events, such as the origin of the genus Homo and the evolution of the species Homo erectus, took place in this region during that time.

An experimental study of dissolution–reprecipitation in fluorapatite: fluid infiltration and the formation of monazite

Abstract: In a series of timed experiments, monazite inclusions are induced to form in the Durango fluorapatite using 1 and 2 N HCl and H2SO4 solutions at temperatures of 300, 600, and 900°C and pressures of 500 and 1,000 MPa. The monazite inclusions form only in reacted areas, i.e. depleted in (Y+REE)+Si+Na+S+Cl. In the HCl experiments, the reaction front between the reacted and unreacted regions is sharp, whereas in the H2SO4 experiments it ranges from sharp to diffuse. In the 1 N HCl experiments, Ostwald ripening of the monazite inclusions took place both as a function of increased reaction time as well as increased temperature and pressure. Monazite growth was more sluggish in the H2SO4 experiments. Transmission electron microscopic (TEM) investigation of foils cut across the reaction boundary in a fluorapatite from the 1 N HCl experiment (600°C and 500 MPa) indicate that the reacted region along the reaction front is characterized by numerous, sub-parallel, 10–20 nm diameter nano-channels. TEM investigation of foils cut from a reacted region in a fluorapatite from the 1 N H2SO4 experiment at 900°C and 1,000 MPa indicates a pervasive nano-porosity, with the monazite inclusions being in direct contact with the surrounding fluorapatite. For either set of experiments, reacted areas in the fluorapatite are interpreted as replacement reactions, which proceed via a moving interface or reaction front associated with what is essentially a simultaneous dissolution–reprecipitation process. The formation of a micro- and nano-porosity in the metasomatised regions of the fluorapatite allows fluids to permeate the reacted areas. This permits rapid mass transfer in the form of fluid-aided diffusion of cations to and from the growing monazite inclusions. Nano-channels and nano-pores also serve as sites for nucleation and the subsequent growth of the monazite inclusions.

The GI-GPx Gene Is a Target for Nrf2

Abstract: The gastrointestinal glutathione peroxidase (GI-GPx, GPx2) is a selenoprotein that was suggested to act as barrier against hydroperoxide absorption but has also been implicated in the control of inflammation and malignant growth. In CaCo-2 cells, GI-GPx was induced by t-butyl hydroquinone (tBHQ) and sulforaphane (SFN), i.e., “antioxidants” known to activate the “antioxidant response element” (ARE) via electrophilic thiol modification of Keap1 in the Nrf2/Keap1 system. The functional significance of a putative ARE in the GI-GPx promoter was validated by transcriptional activation of reporter gene constructs upon exposure to electrophiles (tBHQ, SFN, and curcumin) or overexpression of Nrf2 and by reversal of these effects by mutation of the ARE in the promoter and by overexpressed Keap1. Binding of Nrf2 to the ARE sequence in authentic gpx2 was corroborated by chromatin immunoprecipitation. Thus, the presumed natural antioxidants sulforaphane and curcumin may exert their anti-inflammatory and anticarcinogenic effects not only by induction of phase 2 enzymes but also by the up-regulation of the selenoprotein GI-GPx.

Advantages and Disadvantages of Scenario Approaches for Strategic Foresight

Abstract: Scenarios, as a prime technique of future studies, have long been used by government planners, corporate managers and military analysts as powerful tools to aid in decision making in the face of uncertainty. The idea behind them is to establish thinking about possible futures which can minimise surprises and broaden the span of managers’ thinking about different possibilities. Today the question of what scenarios are is unclear except with regard to one point - they have become extremely popular. This paper attempts to shed light on differences in scenario approaches. It will describe the origin of scenarios and the development of different understandings and purposes for managers. Categories are developed to compare the different ways scenarios are performed. Finally, the advantages and disadvantages of scenario approaches are analysed.

A Mutation in the Dimerization Domain of Filamin C Causes a Novel Type of Autosomal Dominant Myofibrillar Myopathy

Abstract: Myofibrillar myopathy (MFM) is a human disease that is characterized by focal myofibrillar destruction and pathological cytoplasmic protein aggregations. In an extended German pedigree with a novel form of MFM characterized by clinical features of a limb-girdle myopathy and morphological features of MFM, we identified a cosegregating, heterozygous nonsense mutation (8130G→A; W2710X) in the filamin c gene (FLNC) on chromosome 7q32.1. The mutation is the first found in FLNC and is localized in the dimerization domain of filamin c. Functional studies showed that, in the truncated mutant protein, this domain has a disturbed secondary structure that leads to the inability to dimerize properly. As a consequence of this malfunction, the muscle fibers of our patients display massive cytoplasmic aggregates containing filamin c and several Z-disk–associated and sarcolemmal proteins.

Dietary Glycemic Index and Glycemic Load, Carbohydrate and Fiber Intake, and Measures of Insulin Sensitivity, Secretion, and Adiposity in the Insulin Resistance Atherosclerosis Study

Abstract: OBJECTIVE —We studied the association of digestible carbohydrates, fiber intake, glycemic index, and glycemic load with insulin sensitivity ( S I ), fasting insulin, acute insulin response (AIR), disposition index, BMI, and waist circumference. RESEARCH DESIGN AND METHODS —Data on 979 adults with normal (67%) and impaired (33%) glucose tolerance from the Insulin Resistance Atherosclerosis Study (1992–1994) were analyzed. Usual dietary intake was assessed via a 114-item interviewer-administered food frequency questionnaire from which nutrient intakes were estimated. Published glycemic index values were assigned to food items and average dietary glycemic index and glycemic load calculated per subject. S I and AIR were determined by frequently sampled intravenous glucose tolerance test. Disposition index was calculated by multiplying S I with AIR. Multiple linear regression modeling was employed. RESULTS —No association was observed between glycemic index and S I , fasting insulin, AIR, disposition index, BMI, or waist circumference after adjustment for demographic characteristics or family history of diabetes, energy expenditure, and smoking. Associations observed for digestible carbohydrates and glycemic load, respectively, with S I , insulin secretion, and adiposity (adjusted for demographics and main confounders) were entirely explained by energy intake. In contrast, fiber was associated positively with S I and disposition index and inversely with fasting insulin, BMI, and waist circumference but not with AIR. CONCLUSION —Carbohydrates as reflected in glycemic index and glycemic load may not be related to measures of insulin sensitivity, insulin secretion, and adiposity. Fiber intake may not only have beneficial effects on insulin sensitivity and adiposity, but also on pancreatic functionality.

A Jovian-Mass Planet in Microlensing Event OGLE-2005-BLG-071

Abstract: We report the discovery of a several-Jupiter mass planetary companion to the primary lens star in microlensing event OGLE-2005-BLG-071. Precise (<1%) photometry at the peak of the event yields an extremely high signal-to-noise ratio detection of a deviation from the light curve expected from an isolated lens. The planetary character of this deviation is easily and unambiguously discernible from the gross features of the light curve. Detailed modeling yields a tightly-constrained planet-star mass ratio of q=m_p/M=0.0071+/-0.0003. This is the second robust detection of a planet with microlensing, demonstrating that the technique itself is viable and that planets are not rare in the systems probed by microlensing, which typically lie several kpc toward the Galactic center.

GEMS: The Surface Brightness and Surface Mass Density Evolution of Disk Galaxies

Abstract: We combine HST imaging from the GEMS (Galaxy Evolution from Morphologies and SEDs) survey with photometric redshifts from COMBO-17 to explore the evolution of disk-dominated galaxies since z 1.1. The sample is composed of all GEMS galaxies with Sersic indices n < 2.5, derived from fits to the galaxy images. We account fully for selection effects through careful analysis of image simulations; we are limited by the depth of the redshift and HST data to the study of galaxies with MV -20, or equivalently, log 10. We find strong evolution in the magnitude-size scaling relation for galaxies with MV -20, corresponding to a brightening of ~1 mag arcsec-2 in rest-frame V band by z ~ 1. Yet disks at a given absolute magnitude are bluer and have lower stellar mass-to-light ratios at z ~ 1 than at the present day. As a result, our findings indicate weak or no evolution in the relation between stellar mass and effective disk size for galaxies with log 10 over the same time interval. This is strongly inconsistent with the most naive theoretical expectation, in which disk size scales in proportion to the halo virial radius, which would predict that disks are a factor of 2 denser at fixed mass at z ~ 1. The lack of evolution in the stellar mass-size relation is consistent with an inside-out growth of galaxy disks on average (galaxies increasing in size as they grow more massive), although we cannot rule out more complex evolutionary scenarios.

Binding of selected phenolic compounds to proteins.

Abstract: In the context of this study, the noncovalent binding of selected phenolic compounds (chlorogenic, ferulic, and gallic acids, quercetin, rutin, and isoquercetin) to different proteins (human serum albumin, bovine serum albumin, soy glycinin, and lysozyme) was studied with direct (Hummel-Dreyer/size exclusion chromatography) and/or indirect methods (fluorescence absorbance properties of the binding components) In the latter case, the measurement of the phenol binding was achieved by exploiting the intrinsic fluorescence emission properties of quercetin as a probe From the data obtained, the binding constants and the number of binding sites were calculated The binding parameters were influenced by different factors, where, eg, increasing temperature and ionic strength as well as decreasing pH cause a diminished binding The structures of the proteins as determined by circular dichroism indicate changes in the tertiary structure with the secondary structure remaining intact

Detecting fluid signals in seismicity data through statistical earthquake modeling

Abstract: [1] According to the well-known Coulomb failure criterion the variation of either stress or pore pressure can result in earthquake rupture. Aftershock sequences characterized by the Omori law are often assumed to be the consequence of varying stress, whereas earthquake swarms are thought to be triggered by fluid intrusions. The role of stress triggering can be analyzed by modeling solely three-dimensional (3-D) elastic stress changes in the crust, but fluid flows which initiate seismicity cannot be investigated without considering complex seismicity patterns resulting from both pore pressure variations and earthquake-connected stress field changes. We show that the epidemic-type aftershock sequence (ETAS) model is an appropriate tool to extract the primary fluid signal from such complex seismicity patterns. We analyze a large earthquake swarm that occurred in 2000 in Vogtland/NW Bohemia, central Europe. By fitting the stochastic ETAS model, we find that stress triggering is dominant in creating the observed seismicity patterns and explains the observed fractal interevent time distribution. External forcing, identified with pore pressure changes due to fluid intrusion, is found to directly trigger only a few percent of the total activity. However, temporal deconvolution indicates that a pronounced fluid signal initiated the swarm. These results are confirmed by our analogous investigation of model simulations in which earthquakes are triggered by fluid intrusion as well as stress transfers on a fault plane embedded in a 3-D elastic half-space. The deconvolution procedure based on the ETAS model is able to reveal the underlying pore pressure variations.