Showing papers by "University of Konstanz published in 2007"

The Recovery Experience Questionnaire: Development and validation of a measure for assessing recuperation and unwinding from work.

Abstract: Drawing on the mood regulation and job-stress recovery literature, four self-report measures for assessing how individuals unwind and recuperate from work during leisure time were developed (Study 1). Confirmatory factor analyses with a calibration and a cross-validation sample (total N 930) showed that four recovery experiences can be differentiated: psychological detachment from work, relaxation, mastery, and control (Study 2). Examination of the nomological net in a subsample of Study 2 (N 271) revealed moderate relations of the recovery experiences with measures of job stressors and psychological well-being; relations with coping and personality variables were generally low (Study 3). Potential applications for the future use of these short 4-item measures in longitudinal and diary research are discussed.

Joint bilateral upsampling

Abstract: Image analysis and enhancement tasks such as tone mapping, colorization, stereo depth, and photomontage, often require computing a solution (e.g., for exposure, chromaticity, disparity, labels) over the pixel grid. Computational and memory costs often require that a smaller solution be run over a downsampled image. Although general purpose upsampling methods can be used to interpolate the low resolution solution to the full resolution, these methods generally assume a smoothness prior for the interpolation. We demonstrate that in cases, such as those above, the available high resolution input image may be leveraged as a prior in the context of a joint bilateral upsampling procedure to produce a better high resolution solution. We show results for each of the applications above and compare them to traditional upsampling methods.

KNIME: The Konstanz Information Miner.

Abstract: The Konstanz Information Miner is a modular environment, which enables easy visual assembly and interactive execution of a data pipeline. It is designed as a teaching, research and collaboration platform, which enables simple integration of new algorithms and tools as well as data manipulation or visualization methods in the form of new modules or nodes. In this paper we describe some of the design aspects of the underlying architecture and briefly sketch how new nodes can be incorporated.

Functional Aptamers and Aptazymes in Biotechnology, Diagnostics, and Therapy

Abstract: Aptamers are single-stranded nucleic acid molecules that possess properties comparable to those of protein monoclonal antibodies, and thus are clear alternatives to long established antibody-based diagnostic or biotechnological products for research, diagnostics, and therapy. 1-4 This class of functional nucleic acids can fold into complex three-dimensional shapes, 5-7 forming binding pockets and clefts for the specific recognition and tight binding of any given molecular target, 8-10 from metal ions and small chemicals to large proteins and higher order protein complexes, whole cells, viruses, or parasites. Aptamers can be isolated in Vitro from vast combinatorial libraries that comprise trillions of different sequences, by a process called “ in Vitro selection”, or “SELEX”, an acronym for “systematic evolution of ligands by exponential enrichment”. An in Vitro selection experiment comprises a number of sequential steps, the first of which is the generation of a nucleic acid library of random sequences. This starting pool of mainly nonfunctional RNA or DNA sequences is generated using a standard DNA-oligonucleotide synthesizer. 11 The design of such libraries involves the synthesis of a short defined sequence, followed by a random region of variable length and another defined sequence at the 5 ′-end. This pool of synthetic single-stranded DNA (ssDNA) is amplified in the polymerase chain reaction (PCR), generating several copies of each DNA in its double-stranded form. By in Vitro transcription, a corresponding library of RNA molecules can be generated which can then be used for the in Vitro selection. If the transcription reaction contains nucleoside triphosphate derivatives that are chemically modified but still are substrates for RNA polymerases, libraries of modified RNAs can be generated in which sequences are equipped with a broad variety of additional chemical functionalities, normally not present in natural nucleic acids. 12-14 Aptamers selected from chemically modified libraries can, in some cases, be completely resistant toward degradation by nucleases. The additional functional groups can lead to ligands with novel * To whom correspondence should be addressed: telephone, +49-228735661; fax,+49-228-735388; e-mail, m.famulok@uni-bonn.de. † LIMES Institute. ‡ University of Konstanz. Volume 107, Number 9

Distance measurements on spin-labelled biomacromolecules by pulsed electron paramagnetic resonance

Abstract: The biological function of protein, DNA, and RNA molecules often depends on relative movements of domains with dimensions of a few nanometers. This length scale can be accessed by distance measurements between spin labels if pulsed electron paramagnetic resonance (EPR) techniques such as electron-electron double resonance (ELDOR) and double-quantum EPR are used. The approach does not require crystalline samples and is well suited to biomacromolecules with an intrinsic flexibility as distributions of distances can be measured. Furthermore, oligomerization or complexation of biomacromolecules can also be studied, even if it is incomplete. The sensitivity of the technique and the reliability of the measured distance distribution depend on careful optimization of the experimental conditions and procedures for data analysis. Interpretation of spin-to-spin distance distributions in terms of the structure of the biomacromolecules furthermore requires a model for the conformational distribution of the spin labels.

Selective visual attention to emotion.

Abstract: Visual attention can be voluntarily directed toward stimuli and is attracted by stimuli that are emotionally significant. The present study explored the case when both processes coincide and attention is directed to emotional stimuli. Participants viewed a rapid and continuous stream of high-arousing erotica and mutilation stimuli as well as low-arousing control images. Each of the three stimulus categories served in separate runs as target or nontarget category. Event-related brain potential measures revealed that the interaction of attention and emotion varied for specific processing stages. The effects of attention and emotional significance operated additively during perceptual encoding indexed by negative-going potentials over posterior regions (approximately 200-350 ms after stimulus onset). In contrast, thought to reflect the process of stimulus evaluation, P3 target effects (approximately 400-600 ms after stimulus onset) were markedly augmented when erotica and mutilation compared with control stimuli were the focus of attention. Thus, emotion potentiated attention effects specifically during later stages of processing. These findings suggest to specify the interaction of attention and emotion in distinct processing stages.

Geovisual analytics for spatial decision support: Setting the research agenda

Abstract: This article summarizes the results of the workshop on Visualization, Analytics & Spatial Decision Support, which took place at the GIScience conference in September 2006. The discussions at the workshop and analysis of the state of the art have revealed a need in concerted cross-disciplinary efforts to achieve substantial progress in supporting space-related decision making. The size and complexity of real-life problems together with their ill-defined nature call for a true synergy between the power of computational techniques and the human capabilities to analyze, envision, reason, and deliberate. Existing methods and tools are yet far from enabling this synergy. Appropriate methods can only appear as a result of a focused research based on the achievements in the fields of geovisualization and information visualization, human-computer interaction, geographic information science, operations research, data mining and machine learning, decision science, cognitive science, and other disciplines. The name 'Geovisual Analytics for Spatial Decision Support' suggested for this new research direction emphasizes the importance of visualization and interactive visual interfaces and the link with the emerging research discipline of Visual Analytics. This article, as well as the whole special issue, is meant to attract the attention of scientists with relevant expertise and interests to the major challenges requiring multidisciplinary efforts and to promote the establishment of a dedicated research community where an appropriate range of competences is combined with an appropriate breadth of thinking.

Ultrafast time-domain spectroscopy based on high-speed asynchronous optical sampling.

Abstract: High-speed asynchronous optical sampling (ASOPS) is a novel technique for ultrafast time-domain spectroscopy (TDS). It employs two mode-locked femtosecond oscillators operating at a fixed repetition frequency difference as sources of pump and probe pulses. We present a system where the 1 GHz pulse repetition frequencies of two Ti:sapphire oscillators are linked at an offset of ΔfR=10 kHz. As a result, their relative time delay is repetitively ramped from zero to 1 ns within a scan time of 100 μs. Mechanical delay scanners common to conventional TDS systems are eliminated, thus systematic errors due to beam pointing instabilities and spot size variations are avoided when long time delays are scanned. Owing to the multikilohertz scan-rate, high-speed ASOPS permits data acquisition speeds impossible with conventional schemes. Within only 1 s of data acquisition time, a signal resolution of 6×10−7 is achieved for optical pump-probe spectroscopy over a time-delay window of 1 ns. When applied to terahertz TDS, ...

Girls and mathematics —A “hopeless” issue? A control-value approach to gender differences in emotions towards mathematics

Abstract: This study analyzed gender differences in achievement emotions in the domain of mathematics. Based on Pekrun’s (2000, 2006) controlvalue theory of achievement emotions, we hypothesized that there are gender differences in mathematics emotions due to the students’ different levels of control and value beliefs in mathematics, even when controlling for prior achievement. The structural relationships between prior achievement, control and value beliefs, and emotions were assumed to be invariant across girls and boys in spite of hypothesized mean level differences of beliefs and emotions across genders. The emotions and beliefs of 1,036 male and 1,017 female 5th grade students were assessed by self-report measures, and their prior mathematics achievement was assessed by academic grades. Even though girls and boys had received similar grades in mathematics, girls reported significantly less enjoyment and pride than boys, but more anxiety, hopelessness and shame. Findings suggested that the female emotional pattern was due to the girls’ low competence beliefs and domain value of mathematics, combined with their high subjective values of achievement in mathematics. Multiple-group comparisons confirmed that the structural relationships between variables were largely invariant across the genders.

Buzzwords Early Cortical Responses to Emotional Words During Reading

Abstract: Electroencephalographic event-related brain potentials were recorded as subjects read, without further instruction, consecutively presented sequences of words. We varied the speed at which the sequences were presented (3 Hz and 1 Hz) and the words' emotional significance. Early event-related cortical responses during reading differentiated pleasant and unpleasant words from neutral words. Emotional words were associated with enhanced brain responses arising in predominantly left occipito-temporal areas 200 to 300 ms after presentation. Emotional words were also spontaneously better remembered than neutral words. The early cortical amplification was stable across 10 repetitions, providing evidence for robust enhancement of early visual processing of stimuli with learned emotional significance and underscoring the salience of emotional connotations during reading. During early processing stages, emotion-related enhancement of cortical activity along the dominant processing pathway is due to arousal, rather than valence of the stimuli. This enhancement may be driven by cortico-amygdaloid connections.

Coherent structural dynamics and electronic correlations during an ultrafast insulator-to-metal phase transition in VO2.

Abstract: We directly trace the multi-THz conductivity of VO2 during an insulator-metal transition triggered by a 12-fs light pulse. The femtosecond dynamics of lattice and electronic degrees of freedom are spectrally discriminated. A coherent wave packet motion of V-V dimers at 6 THz modulates the lattice polarizability for approximately 1 ps. In contrast, the electronic conductivity settles to a constant value already after one V-V oscillation cycle. Based on our findings, we propose a qualitative model for the nonthermal phase transition.

Centrality Estimation in Large Networks

Abstract: Centrality indices are an essential concept in network analysis. For those based on shortest-path distances the computation is at least quadratic in the number of nodes, since it usually involves solving the single-source shortest-paths (SSSP) problem from every node. Therefore, exact computation is infeasible for many large networks of interest today. Centrality scores can be estimated, however, from a limited number of SSSP computations. We present results from an experimental study of the quality of such estimates under various selection strategies for the source vertices.

The Neural Code of Auditory Phantom Perception

Abstract: Tinnitus is defined by an auditory perception in the absence of an external source of sound. This condition provides the distinctive possibility of extracting neural coding of perceptual representation. Previously, we had established that tinnitus is characterized by enhanced magnetic slow-wave activity (approximately 4 Hz) in perisylvian or putatively auditory regions. Because of works linking high-frequency oscillations to conscious sensory perception and positive symptoms in a variety of disorders, we examined gamma band activity during brief periods of marked enhancement of slow-wave activity. These periods were extracted from 5 min of resting spontaneous magnetoencephalography activity in 26 tinnitus and 21 control subjects. Results revealed the following, particularly within a frequency range of 50-60 Hz: (1) Both groups showed significant increases in gamma band activity after onset of slow waves. (2) Gamma is more prominent in tinnitus subjects than in controls. (3) Activity at approximately 55 Hz determines the laterality of the tinnitus perception. Based on present and previous results, we have concluded that cochlear damage, or similar types of deafferentation from peripheral input, triggers reorganization in the central auditory system. This produces permanent alterations in the ongoing oscillatory dynamics at the higher layers of the auditory hierarchical stream. The change results in enhanced slow-wave activity reflecting altered corticothalamic and corticolimbic interplay. Such enhancement facilitates and sustains gamma activity as a neural code of phantom perception, in this case auditory.

Follower Behavior and Organizational Performance : the Impact of Transformational Leaders

Abstract: This study sheds light on the mediating processes by which transformational leadership influences follower performance and innovation, respectively. We hypothesize that transformational leaders boost follower performance by stimulating organizational citizenship behavior, whereas they enhance follower innovation by triggering controversial discussion of task related issues (debate). On the contrary, we do not expect these mediating effects to hold for the relationship between transactional leadership and follower performance and innovation, respectively. Our hypotheses were confirmed in an empirical study of N = 91 leaders from 91 German companies. Conclusions for leadership research are drawn. Key words: debate, innovation, organizational citizenship behavior, transactional leadership, transformational leadership

Running on Empty Neural Signals for Self-Control Failure

Abstract: Past research shows that self-control is limited and becomes depleted after initial exertions. This study examined the neural processes underlying self-control failure by testing whether controlled, effortful behavior impairs subsequent attempts at control by depleting the neural system associated with conflict monitoring. Subjects either watched an emotional movie normally or tried to suppress their emotions while watching the movie; they then completed an ostensibly unrelated Stroop task while electroencephalographic activity was recorded. The error-related negativity (ERN)--a waveform associated with activity in the anterior cingulate--was measured to determine whether prior regulatory exertion constrained the conflict-monitoring system. Compared with subjects in the control condition, those who suppressed their emotions performed worse on the Stroop task, and this deficit was mediated by weaker ERN signals. These results offer a neural account for the self-regulatory-strength model and demonstrate the utility of the social neuroscience approach.

Activation of TLR2 and TLR4 by Glycosylphosphatidylinositols Derived from Toxoplasma gondii

Abstract: GPIs isolated from Toxoplasma gondii , as well as a chemically synthesized GPI lacking the lipid moiety, activated a reporter gene in Chinese hamster ovary cells expressing TLR4, while the core glycan and lipid moieties cleaved from the GPIs activated both TLR4- and TLR2-expressing cells. MyD88, but not TLR2, TLR4, or CD14, is absolutely needed to trigger TNF-α production by macrophages exposed to T. gondii GPIs. Importantly, TNF-α response to GPIs was completely abrogated in macrophages from TLR2/4-double-deficient mice. MyD88 −/− mice were more susceptible to death than wild-type (WT), TLR2 −/− , TLR4 −/− , TLR2/4 −/− , and CD14 −/− mice infected with the ME-49 strain of T. gondii . The cyst number was higher in the brain of TLR2/4 −/− , but not TLR2 −/− , TLR4 −/− , and CD14 −/− , mice, as compared with WT mice. Upon infection with the ME-49 strain of T. gondii , we observed no decrease of IL-12 and IFN-γ production in TLR2-, TLR4-, or CD14-deficient mice. Indeed, splenocytes from T. gondii -infected TLR2 −/− and TLR2/4 −/− mice produced more IFN-γ than cells from WT mice in response to in vitro stimulation with parasite extracts enriched in GPI-linked surface proteins. Together, our results suggest that both TLR2 and TLR4 receptors may participate in the host defense against T. gondii infection through their activation by the GPIs and could work together with other MyD88-dependent receptors, like other TLRs or even IL-18R or IL-1R, to obtain an effective host response against T. gondii infection.

Cadmium‐induced inhibition of photosynthesis and long‐term acclimation to cadmium stress in the hyperaccumulator Thlaspi caerulescens

Abstract: Summary • Acclimation of hyperaccumulators to heavy metal-induced stress is crucial for phytoremediation and was investigated using the hyperaccumulator Thlaspi caerulescens and the nonaccumulators T. fendleri and T. ochroleucum. • Spatially and spectrally resolved kinetics of in vivo absorbance and fluorescence were measured with a novel fluorescence kinetic microscope. • At the beginning of growth on cadmium (Cd), all species suffered from toxicity, but T. caerulescens subsequently recovered completely. During stress, a few mesophyll cells in T. caerulescens became more inhibited and accumulated more Cd than the majority; this heterogeneity disappeared during acclimation. Chlorophyll fluorescence parameters related to photochemistry were more strongly affected by Cd stress than nonphotochemical parameters, and only photochemistry showed acclimation. • Cd acclimation in T. caerulescens shows that part of its Cd tolerance is inducible and involves transient physiological heterogeneity as an emergency defence mechanism. Differential effects of Cd stress on photochemical vs nonphotochemical parameters indicate that Cd inhibits the photosynthetic light reactions more than the Calvin–Benson cycle. Differential spectral distribution of Cd effects on photochemical vs nonphotochemical quenching shows that Cd inhibits at least two different targets in/around photosystem II (PSII). Spectrally homogeneous maximal PSII efficiency (Fv/Fm) suggests that in healthy T. caerulescens all chlorophylls fluorescing at room temperature are PSII-associated.

Optimal L p - L q -estimates for parabolic boundary value problems with inhomogeneous data

Abstract: In this paper we investigate vector-valued parabolic initial boundary value problems \({(\mathcal A(t,x,D)}\) , \({\mathcal B_j(t,x,D))}\) subject to general boundary conditions in domains G in \({\mathbb R^n}\) with compact C 2m -boundary. The top-order coefficients of \({\mathcal A}\) are assumed to be continuous. We characterize optimal L p -L q -regularity for the solution of such problems in terms of the data. We also prove that the normal ellipticity condition on \({\mathcal A}\) and the Lopatinskii–Shapiro condition on \({(\mathcal A, \mathcal B_1,\dots, \mathcal B_m)}\) are necessary for these L p -L q -estimates. As a byproduct of the techniques being introduced we obtain new trace and extension results for Sobolev spaces of mixed order and a characterization of Triebel-Lizorkin spaces by boundary data.

Coherent anti-Stokes Raman Scattering Microscopy

Abstract: Coherent anti-Stokes Raman scattering (CARS) microscopy is presented as a new nonlinear optical technique. The combination of vibrational spectroscopy and microscopy allows highly sensitive investigations of unlabelled samples. CARS is an ideal tool for studying a broad variety of samples. The main drawback of the technique is its non-zero-background nature, which implies that the signal has to be detected against a nonresonant background. The need to solve this problem is reflected in the rapid technological developments that have been observed during the last decade. Recent results show that CARS microscopy has the potential to become an important complementary technique that can be used with other well-established microscopic methods. Although it has some limitations, it offers unique access to many problems that cannot be tackled with conventional techniques. For this reason, it can be expected that the impressive growth of the field will continue.

Consensus for tinnitus patient assessment and treatment outcome measurement: Tinnitus Research Initiative meeting, Regensburg, July 2006.

Abstract: There is widespread recognition that consistency between research centres in the ways that patients with tinnitus are assessed and outcomes following interventions are measured would facilitate more effective co-operation and more meaningful evaluations and comparisons of outcomes. At the first Tinnitus Research Initiative meeting held in Regensburg in July 2006 an attempt was made through workshops to gain a consensus both for patient assessments and for outcome measurements. It is hoped that this will contribute towards better cooperation between research centres in finding and evaluating treatments for tinnitus by allowing better comparability between studies.

Thermodynamics of the BCS-BEC crossover

Abstract: We present a self-consistent theory for the thermodynamics of the BCS-BEC crossover in the normal and superfluid phase which is both conserving and gapless. It is based on the variational many-body formalism developed by Luttinger and Ward and by DeDominicis and Martin. Truncating the exact functional for the entropy to that obtained within a ladder approximation, the resulting self-consistent integral equations for the normal and anomalous Green functions are solved numerically for arbitrary coupling. The critical temperature, the equation of state, and the entropy are determined as a function of the dimensionless parameter $1∕{k}_{F}a$, which controls the crossover from the BCS regime of extended pairs to the BEC regime of tightly bound molecules. The tightly bound pairs turn out to be described by a Popov-type approximation for a dilute, repulsive Bose gas. Even though our approximation does not capture the critical behavior near the continuous superfluid transition, our results provide a consistent picture for the complete crossover thermodynamics which compares well with recent numerical and field-theoretic approaches at the unitarity point.

Growth Yields in Bacterial Denitrification and Nitrate Ammonification

Abstract: Denitrification and nitrate ammonification are considered the highest-energy-yielding respiration systems in anoxic environments after oxygen has been consumed. The corresponding free energy changes are 7 and 35% lower than that of aerobic respiration, respectively. Growth yield determinations with pure cultures of Paracoccus denitrificans and Pseudomonas stutzeri revealed that far less energy is converted via ATP into cell mass than expected from the above calculations. Denitrification with formate or hydrogen as electron donor yielded about 2.4 to 3.0 g dry matter per mol formate or hydrogen and 15 to 18 g dry matter per mol acetate. Similar yields with acetate were obtained with Pseudomonas stutzeri. Wolinella succinogenes and Sulfurospirillum deleyianum, which reduce nitrate to ammonia, both exhibited similar yield values with formate or H2 plus nitrate. The results indicate that ATP synthesis in denitrification is far lower than expected from the free energy changes and even lower than in nitrate ammonification. The results are discussed against the background of our present understanding of electron flow in denitrification and with respect to the importance of denitrification and nitrate ammonification in the environment.

Using musical instruments to improve motor skill recovery following a stroke

Abstract: In previous studies, it was shown that there is a need for efficient motor rehabilitation approaches. For this purpose, we evaluated a music-supported training program designed to induce an auditory-sensorimotor co-representation of movements in 20 stroke patients (10 affected in the left and 10 in the right upper extremity). Patients without any previous musical experience participated in an intensive step by step training, first of the paretic extremity, followed by training of both extremities. Training was applied 15 times over 3 weeks in addition to conventional treatment. Fine as well as gross motor skills were addressed by using either a MIDI-piano or electronic drum pads. As a control, 20 stroke patients (10 affected left and 10 right) undergoing exclusively conventional therapies were recruited. Assignment to the training and control groups was done pseudo-randomly to achieve an equal number of left- and right-affected patients in each group. Pre- and post-treatment motor functions were monitored using a computerized movement analysis system (Zebris) and an established array of motor tests (e. g., Action Research Arm Test, Box & Block Test). Patients showed significant improvement after treatment with respect to speed, precision and smoothness of movements as shown by 3D movement analysis and clinical motor tests. Furthermore, compared to the control subjects, motor control in everyday activities improved significantly. In conclusion, this innovative therapeutic strategy is an effective approach for the motor skill neurorehabilitation of stroke patients.

ProteomeBinders: planning a European resource of affinity reagents for analysis of the human proteome

Abstract: ProteomeBinders is a new European consortium aiming to establish a comprehensive resource of well-characterized affinity reagents, including but not limited to antibodies, for analysis of the human proteome. Given the huge diversity of the proteome, the scale of the project is potentially immense but nevertheless feasible in the context of a pan-European or even worldwide coordination.

Solid texture synthesis from 2D exemplars

Abstract: We present a novel method for synthesizing solid textures from 2D texture exemplars. First, we extend 2D texture optimization techniques to synthesize 3D texture solids. Next, the non-parametric texture optimization approach is integrated with histogram matching, which forces the global statistics of the synthesized solid to match those of the exemplar. This improves the convergence of the synthesis process and enables using smaller neighborhoods. In addition to producing compelling texture mapped surfaces, our method also effectively models the material in the interior of solid objects. We also demonstrate that our method is well-suited for synthesizing textures with a large number of channels per texel.

Structural and functional insights into RAGE activation by multimeric S100B

Abstract: Nervous system development and plasticity require regulation of cell proliferation, survival, neurite outgrowth and synapse formation by specific extracellular factors. The EF-hand protein S100B is highly expressed in human brain. In the extracellular space, it promotes neurite extension and neuron survival via the receptor RAGE (receptor for advanced glycation end products). The X-ray structure of human Ca2+-loaded S100B was determined at 1.9 A resolution. The structure revealed an octameric architecture of four homodimeric units arranged as two tetramers in a tight array. The presence of multimeric forms in human brain extracts was confirmed by size-exclusion experiments. Recombinant tetrameric, hexameric and octameric S100B were purified from Escherichia coli and characterised. Binding studies show that tetrameric S100B binds RAGE with higher affinity than dimeric S100B. Analytical ultracentrifugation studies imply that S100B tetramer binds two RAGE molecules via the V-domain. In line with these experiments, S100B tetramer caused stronger activation of cell growth than S100B dimer and promoted cell survival. The structural and the binding data suggest that tetrameric S100B triggers RAGE activation by receptor dimerisation.