julilili42/papers huggingface dataset:
Tight focusing of laser beams in a λ/2-microcavity
2008-06-20

We evaluate the field distribution in the focal spot of the fundamental Gaussian beam as well as radially and azimuthally polarized doughnut beams focused inside a planar metallic sub-wavelength microcavity using a high numerical aperture objective lens. We show that focusing in the cavity results in a much tighter focal spot in longitudinal direction compared to free space and in spatial discrimination between longitudinal and in-plane field components. In order to verify the modeling results we experimentally monitor excitation patterns of fluorescence beads inside the lambda/2-cavity and find them in full agreement to the modeling predictions. We discuss the implications of the results for cavity assisted single molecular spectroscopy and intra-cavity single molecular imaging.
Analysis of a Novel Insect Cell Culture Medium-Based Growth Medium for Bartonella Species
2008-06-21

ABSTRACT Human- and animal-pathogenic Bartonella species are fastidious and slow-growing bacteria difficult to isolate and cultivate. We describe a novel, easy-to-prepare liquid medium for the fast and reliable growth of several Bartonella spp. that does not affect bacterial protein expression patterns or interactions with host cells.
Uncertainty of the claims development result in the chain ladder method
2008-06-21

Abstract Using the distribution-free chain ladder method, we estimate the total ultimate claim amounts at time I, and after updating the information, at time I+1. The observable claims development result at time I+1 for accounting year (I, I+1] is then defined to be the difference between these two successive best estimate predictions for the ultimate claim. We analyze the uncertainty of this observable claims development result. Keywords: Non-life insuranceClaims reservingChain ladder methodMean square error of predictionClaims development resultSolvency II
SNAREing the Basis of Multicellularity: Consequences of Protein Family Expansion during Evolution
2008-06-23

Vesicle trafficking between intracellular compartments of eukaryotic cells is mediated by conserved protein machineries. In each trafficking step, fusion of the vesicle with the acceptor membrane is driven by a set of distinctive soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) proteins that assemble into tight 4-helix bundle complexes between the fusing membranes. During evolution, about 20 primordial SNARE types were modified independently in different eukaryotic lineages by episodes of duplication and diversification. Here we show that 2 major changes in the SNARE repertoire occurred in the evolution of animals, each reflecting a main overhaul of the endomembrane system. In addition, we found several lineage-specific losses of distinct SNAREs, particularly in nematodes and platyhelminthes. The first major transformation took place during the transition to multicellularity. The primary event that occurred during this transformation was an increase in the numbers of endosomal SNAREs, but the SNARE-related factor lethal giant larvae also emerged. Apparently, enhanced endosomal sorting capabilities were an advantage for early multicellular animals. The second major transformation during the rise of vertebrates resulted in a robust expansion of the secretory set of SNAREs, which may have helped develop a more versatile secretory apparatus.
Pion dominance inR-parity violating supersymmetry induced neutrinoless double beta decay
2008-06-23

At the quark level there are basically two types of contributions of R-parity violating SUSY (RPV SUSY) to neutrinoless double beta decay: the short-range contribution involving only heavy virtual superpartners and the long-range one with the virtual squark and neutrino. Hadronization of the effective operators, corresponding to these two types of contributions, may in general involve virtual pions in addition to the close on-mass-shell nucleons. It is known that the short-range contribution is dominated by the pion exchange. In the present paper we show that this is also true for the long-range RPV SUSY contribution and, therefore, the RPV SUSY contributes to the neutrinoless double beta decay dominantly via charged pion exchange between the decaying nucleons.
Simulations of eccentric disks in close binary systems
2008-06-24

We study the development of finite eccentricity in accretion disks in close\\nbinary systems using a two-dimensional grid-based numerical scheme. We perform\\ndetailed parameter studies to explore the dependence on viscosity, disk aspect\\nratio, the inclusion of a mass-transfer stream and the role of the boundary\\nconditions. We consider mass ratios 0.05&lt;q&lt;0.3 appropriate to superoutbursting\\ncataclysmic binary systems.\\n Instability to the formation of a precessing eccentric disk that attains a\\nquasi-steady state with mean eccentricity in the range 0.3-0.5 occurs readily.\\nThe shortest growth times are ~15 binary orbits for the largest viscosities and\\nthe instability mechanism is for the most part consistent with the\\nmode-coupling mechanism associated with the 3:1 resonance proposed by Lubow.\\nHowever, the results are sensitive to the treatment of the inner boundary and\\nto the incorporation of the mass-transfer stream. In the presence of a stream\\nwe found a critical viscosity below which the disk remains circular.\\n Incorporation of a mass-transfer stream tends to impart stability for small\\nenough viscosity (or, equivalently, mass-transfer rate through the disk) and\\ndoes assist in obtaining a prograde precession rate that is in agreement with\\nobservations. For the larger q the location of the 3:1 resonance is pushed\\noutwards towards the Roche lobe where higher-order mode couplings and\\nnonlinearity occur. It is likely that three-dimensional simulations that\\nproperly resolve the disk's vertical structure are required to make significant\\nprogress in this case.\\n
Simulations of eccentric disks in close binary systems
2008-06-24

Context. Eccentric accretion disks in superoutbursting cataclysmic and other binary systems. Aims. We study the development of finite eccentricity in accretion disks in close binary systems using a grid-based numerical scheme. We perform detailed parameter studies to explore the dependence on viscosity, disk aspect ratio, the inclusion of a mass-transfer stream and the role of the boundary conditions. Methods. Using a two-dimensional grid-based scheme we study the instability of accretion disks in close binary systems that causes them to attain a quasi-steady state with finite eccentricity. Mass ratios appropriate to superoutbursting cataclysmic binary systems are considered. Results. Our grid-based scheme enables us to study the development of eccentric disks for disk aspect ratio h in the range and dimensionless kinematic viscosity ν in the range . Previous studies using particle-based methods were limited to the largest values for these parameters on account of their diffusive nature. Instability to the formation of a precessing eccentric disk that attains a quasi-steady state with mean eccentricity in the range occurs readily. The shortest growth times are ~15 binary orbits for the largest viscosities and the instability mechanism is for the most part consistent with the mode-coupling mechanism associated with the 3:1 resonance proposed by Lubow. However, the results are sensitive to the treatment of the inner boundary and to the incorporation of the mass-transfer stream. In the presence of a stream we found a critical viscosity below which the disk remains circular. Conclusions. Eccentric disks readily develop in close binary systems with Incorporation of a mass-transfer stream tends to impart stability for small enough viscosity (or, equivalently, mass-transfer rate through the disk) and to assist in obtaining a prograde precession rate that is in agreement with observations. For the larger q the location of the 3:1 resonance is pushed outwards towards the Roche lobe where higher-order mode couplings and nonlinearity occur. It is likely that three-dimensional simulations that properly resolve the disk's vertical structure are required to make significant progress in this case.
HESS upper limits for Kepler's supernova remnant
2008-06-24

Observations of Kepler's supernova remnant (G4.5+6.8) with the H.E.S.S.\\ntelescope array in 2004 and 2005 with a total live time of 13 h are presented.\\nStereoscopic imaging of Cherenkov radiation from extensive air showers is used\\nto reconstruct the energy and direction of the incident gamma rays. No evidence\\nfor a very high energy (VHE: &gt;100 GeV) gamma-ray signal from the direction of\\nthe remnant is found. An upper limit (99% confidence level) on the energy flux\\nin the range 230 GeV - 12.8 TeV of 8.6 x 10^{-13} erg cm^{-2} s^{-1} is\\nobtained. In the context of an existing theoretical model for the remnant, the\\nlack of a detectable gamma-ray flux implies a distance of at least 6.4 kpc. A\\ncorresponding upper limit for the density of the ambient matter of 0.7 cm^{-3}\\nis derived. With this distance limit, and assuming a spectral index Gamma = 2,\\nthe total energy in accelerated protons is limited to E_p &lt; 8.6 x 10^{49} erg.\\nIn the synchrotron/inverse Compton framework, extrapolating the power law\\nmeasured by RXTE between 10 and 20 keV down in energy, the predicted gamma-ray\\nflux from inverse Compton scattering is below the measured upper limit for\\nmagnetic field values greater than 52 muG.\\n
Learning and knowledge building with wikis: the impact of incongruity between people's knowledge and a wiki's information
2008-06-24

The study reported in this article aims at empirically testing a theoretical model of collaborative knowledge building with wikis which was recently introduced by Cress and Kimmerle (2007; in press). This model assumes that individual learning and collaborative knowledge building are based on the interplay between people's knowledge and the information available in the wiki. This interplay takes place in the form of externalization and internalization respectively. Individual learning is considered as happening through internal processes of assimilation and accommodation. Collaborative knowledge building happens through activities of external assimilation and accommodation. This study demonstrates these four processes in an experimental setting. As postulated by Cress and Kimmerle, the results show that a medium level of incongruity between people's knowledge and a wiki's information supports individual learning. A medium level of incongruity also leads to more external accommodation processes, despite the fact that high and medium levels of incongruity result in the same amount of text complements.
The modality effect in multimedia learning: theoretical and empirical limitations
2008-06-24

Abstract: Numerous studies in the field of multimedia learning have confirmed the modality principle, which claims that the presentation of pictures with auditory texts leads to better learning outcomes than the presentation of pictures with visual text. However, there are still some doubts concerning the theoretical explanation and the boundary conditions of the modality principle. An overview is given with regard to these two points. Furthermore, two experiments are reported, which aimed at clarifying the theoretical explanation (Experiment 1) and the boundary conditions of the modality effect (Experiment 2). Experiment 1 was conducted to test whether the modality effect occurs irrespective of the temporal contiguity of text and pictures. In Experiment 2, it was investigated, if the modality principle also holds for longer, complex texts and if the time available for information processing acts as a moderating variable.
Enhancing students' knowledge of biodiversity in a situated mobile learning scenario: using static and dynamic visualizations in field trips
2008-06-24

The effectiveness of static versus dynamic learning material was tested using fish biodiversity as learning domain. Eighteen fish species were presented either as videos or selected freeze-frames to students. Thereafter, students exercised identifying these species in their natural habitats during snorkeling. Students' knowledge of biodiversity was measured from test videos before (posttest 1) and after (posttest 2) snorkeling as the number of recognized species. Results showed significant knowledge gains between posttest 1 and 2. For the presentation format (static vs. dynamic) there was no significant main effect. However, a significant interaction showed that the students' knowledge improved from posttest 1 to 2 to a larger extent in the dynamic group. The study was conducted within a university curriculum for which a mobile learning scenario using portable DVD-players was applied for the first time. Overall results indicate a high potential for using mobile devices in informal settings during field trips.
In the eyes of experts: teaching dynamic features in biology by modeling experts' eye movement strategies to novices
2008-06-24

In biology education, it is crucial to be able to classify objects based on complex visual information (e.g., shapes and locomotion patterns of fish). Usually, this ability is trained with books displaying static features and only explaining dynamic features. However, for many classification tasks the dynamic features are very important. Therefore, the overall aim of the two studies described in this paper was to develop an innovative instructional technique for teaching classification skills to students using dynamic visualizations. In order to develop this technique, the first study was conducted to analyze classification processes of experts and novices in detail. This was done by investigating process-oriented differences between experts and novices using eye movements and verbal data obtained during classifying the locomotion pattern of different types of fish. In a second study the process data of experts are replayed to novices in order to support novices in adapting experts' classification strategies.
Knowledge convergence in CMC: the impact of convergence-related external representations
2008-06-24

Knowledge convergence is at the heart of even very different approaches to collaborative learning. Recent empirical work revealed that knowledge convergence falls behind the expectations because only modest amount of shared knowledge could be found. We investigate knowledge awareness as a method to foster the emergence of knowledge convergence in an experimental study. Knowledge awareness provides collaborators with convergence-related external representations. This was found to support learners in tapping their convergence potential.
A fast event preprocessor for the Simbol-X Low-Energy Detector
2008-06-24

The Simbol-X<sup>1</sup> Low Energy Detector (LED), a 128 &times; 128 pixel DEPFET array, will be read out very fast (8000 frames/second). This requires a very fast onboard data preprocessing of the raw data. We present an FPGA based Event Preprocessor (EPP) which can fulfill this requirements. The design is developed in the hardware description language VHDL and can be later ported on an ASIC technology. The EPP performs a pixel related offset correction and can apply different energy thresholds to each pixel of the frame. It also provides a line related common-mode correction to reduce noise that is unavoidably caused by the analog readout chip of the DEPFET. An integrated pattern detector can block all invalid pixel patterns. The EPP has an internal pipeline structure and can perform all operation in realtime (< 2 &mu;s per line of 64 pixel) with a base clock frequency of 100 MHz. It is utilizing a fast median-value detection algorithm for common-mode correction and a new pattern scanning algorithm to select only valid events. Both new algorithms were developed during the last year at our institute.
Supporting the use of multiple representations in multimedia learning environments
2008-06-24

Many learning environments contain multiple representations. Using them can lead to a deeper level of cognitive processing when learners make mental transformations between representations. However, research has revealed two problems. First, it has been shown that learners often do not make spontaneous use of such multiple options. Second, the translation process is often difficult. The papers presented in this symposium aim at supporting learners' use of multiple representations as well as their translation process. The first study provided learners with different types of representations and asked them to translate those into other representations. The second study examined the effectiveness of contextual scaffolds in computer simulations. The third study aimed at supporting hypermedia learning with multiple representations by means of metacognitive modelling and prompting of representational awareness. The fourth study investigated if sequencing dynamic representations combined with explicit instruction to relate and translate between representations has a positive effect on learning outcomes.
The potential of computer-supported collaboration and knowledge awareness for supporting analogical problem solving
2008-06-24

Abstract: The present experimental study investigates the impact of computer-supported collaboration and knowledge awareness regarding the source problems the collaboration partner has remembered on analogical problem solving. Collaborating dyads with an external representation for supporting knowledge awareness were compared to collaborating dyads without such an external representation and to a baseline of nominal dyads. Collaborating dyads were less efficient in analogical problem solving than nominal dyads. Theoretical Background and Research Questions Analogical problem solving as a central learning mechanism can be defined as transferring the entire solution process or parts of it from a previous source problem to a new target problem from a more or less disparate domain (Hesse &amp;amp; Klecha, 1990). Individuals, especially novices, often have difficulties in identifying structural correspondences between source problems and target problems, as they mainly focus on surface similarities. Therefore, in the present project, it is assumed that mutual explanation during collaboration on an external representation may stimulate a deeper level of processing, and thus may foster identification of structural correspondences between source problem and target problem (Schwartz, 1995). Furthermore, it is assumed that the postulated positive impact of computer-supported collaboration on analogical problem solving
Interferon‐γ limits the availability of iron for intramacrophage Salmonella typhimurium
2008-06-25

Abstract In stimulating effector functions of mononuclear phagocytes, IFN‐γ is of pivotal importance in host defense against intramacrophage pathogens including salmonellae. As the activity of IFN‐γ is modulated by iron and since a sufficient availability of iron is essential for the growth of pathogens, we investigated the regulatory effects of IFN‐γ on iron homeostasis and immune function in murine macrophages infected with Salmonella typhimurium . In Salmonella ‐infected phagocytes, IFN‐γ caused a significant reduction of iron uptake via transferrin receptor 1 and resulted in an increased iron efflux caused by an enhanced expression of the iron exporter ferroportin 1. Moreover, the expression of haem oxygenase 1 and of the siderophore‐capturing antimicrobial peptide lipocalin 2 was markedly elevated following bacterial invasion, with IFN‐γ exerting a super‐inducing effect. This observed regulatory impact of IFN‐γ reduced the intracellular iron pools within infected phagocytes, thus restricting the acquisition of iron by engulfed Salmonella typhimurium while concomitantly promoting NO and TNF‐α production. Our data suggest that the modulation of crucial pathways of macrophage iron metabolism in response to IFN‐γ concordantly aims at withdrawing iron from intracellular Salmonella and at strengthening macrophage immune response functions. These regulations are thus consistent with the principles of nutritional immunity. See accompanying commentary http://dx.doi.org/10.1002/eji.200838505
Neuromagnetic Response to Body Motion and Brain Connectivity
2008-06-25

Abstract Visual detection of body motion is of immense importance for daily-life activities and social nonverbal interaction. Although neurobiological mechanisms underlying visual processing of human locomotion are being explored extensively by brain imaging, the role of structural brain connectivity is not well understood. Here we investigate cortical evoked neuromagnetic response to point-light body motion in healthy adolescents and in patients with early periventricular lesions, periventricular leukomalacia (PVL), that disrupt brain connectivity. In a simultaneous masking paradigm, participants detected the presence of a point-light walker embedded in a few sets of spatially scrambled dots on the joints of a walker. The visual sensitivity to camouflaged human locomotion was lower in PVL patients. In accord with behavioral data, root-mean-square (RMS) amplitude of neuromagnetic trace in response to human locomotion was lower in PVL patients at latencies of 180–244 msec over the right temporal cortex. In this time window, the visual sensitivity to body motion in controls, but not in PVL patients, was inversely linked to the right temporal activation. At later latencies of 276–340 msec, we found reduction in RMS amplitude in PVL patients for body motion stimuli over the right frontal cortex. The findings indicate that disturbances in brain connectivity with the right temporal cortex, a key node of the social brain, and with the right frontal cortex lead to disintegration of the neural network engaged in visual processing of body motion. We suspect that reduced cortical response to body motion over the right temporal and frontal cortices might underlie deficits in visual social cognition.
Design, Synthesis, and Biological Evaluation of Novel Tri- and Tetrasubstituted Imidazoles as Highly Potent and Specific ATP-Mimetic Inhibitors of p38 MAP Kinase: Focus on Optimized Interactions with the Enzyme’s Surface-Exposed Front Region
2008-06-26

The synthesis, biological testing, and SAR of novel 2,4,5- and 1,2,4,5-substituted 2-thioimidazoles are described. Amino, oxy, or thioxy substituents at the 2-position of the pyridinyl moiety were evaluated for their contributions to inhibitor potency and selectivity against p38 mitogen activated protein kinase (p38 MAPK) as well as for the ability to minimize cytochrome P450 (CYP450) inhibition. Incorporation of polar substituted (cyclo)aliphatic amino substituents (e.g., tetrahydropyranylamino), which positively interacted with the surface-exposed front region (hydrophobic region II) of the enzyme led to the identification of extremely potent p38 MAPK inhibitors with p38 IC 50 values in the low nanomolar range. Approximately 90 pyridinylimidazole-based compounds with a range of potencies against p38alpha MAP kinase were further investigated for their ability to inhibit the release of tumor necrosis factor-alpha (TNFalpha) and/or interleukin-1beta (IL-1beta) from human whole blood. Some of the most promising drug candidates underwent selectivity profiling against a panel of 17 different kinases besides p38alpha and/or were tested for their interaction potential toward a number of metabolically relevant CYP450 isozymes.
Using reagent-supported thromboelastometry (ROTEM®) to monitor haemostatic changes in congenital heart surgery employing deep hypothermic circulatory arrest
2008-06-26

A major benefit of ROTEM is the quick detection of a developing coagulopathy already during CPB. ROTEM guides quick and specific blood product treatment after CPB, which may decrease bleeding complications in cardiac surgery. The finding of maximal platelet activation directly after DHCA suggests that not only CPB but also hypothermia activates platelets in vivo, thereby contributing to platelet dysfunction.