bluuebunny/crossref_metadata_2025 huggingface dataset:
Photocurrent characteristics of individual GeSe2 nanobelt with Schottky effects
Authors: Mukherjee Bablu , Tok Eng Soon , Sow Chorng Haur
Published: October 2013

Single crystal GeSe2 nanobelts (NBs) were successfully grown using chemical vapor deposition techniques. The morphology and structure of the nanostructures were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, and Raman spectroscopy. Electronic transport properties, photoconductive characteristics, and temperature-dependent electronic characteristics were examined on devices made of individual GeSe2 nanobelt. The current increased by three orders of magnitude upon laser irradiation (wavelength 532 nm and intensity ∼6.8 mW/cm2) with responsivity of ∼2764 A/W at fixed 4 V bias. Localized photoconductivity study shows that the large photoresponse of the device primarily occurs at the metal-NB contact regions. In addition, the electrically Schottky nature of nanobelt/Au contact and p-type conductivity nature of GeSe2 nanobelt are extracted from the current-voltage characteristics and spatially resolved photocurrent measurements. The high sensitivity and quick photoresponse in the visible wavelength range indicate potential applications of individual GeSe2 nanobelt devices in realizing optoelectronic switches.
Electro-migration of impurities in TlBr
Authors: Kim Ki Hyun , Kim Eunlim , Kim H. , Tappero R. , Bolotnikov A. E. , Camarda G. S. , Hossain A. , Cirignano L. , James R. B.
Published: October 2013

We observed the electro-migration of Cu, Ag, and Au impurities that exist in positive-ion states in TlBr detectors under electric field strengths typically used for device operation. The migration occurred predominantly through bulk- and specific-channels, which are presumed to be a network of grain and sub-grain boundaries. The electro-migration velocity of Cu, Ag, and Au in TlBr is about 4–8 × 10−8 cm/s at room temperature under an electric field of 500–800 V/mm. The instability and polarization effects of TlBr detectors might well be correlated with the electro-migration of residual impurities in TlBr, which alters the internal electric field over time. The effect may also have been due to migration of the electrode material itself, which would allow for the possibility of a better choice for contact material and for depositing an effective diffusion barrier. From our findings, we suggest that applying our electro-migration technique for purifying material is a promising new way to remove electrically active metallic impurities in TlBr crystals, as well as other materials.
A complex network based model for detecting isolated communities in water distribution networks
Authors: Sheng Nan , Jia Youwei , Xu Zhao , Ho Siu-Lau , Wai Kan Chi
Published: October 2013

Water distribution network (WDN) is a typical real-world complex network of major infrastructure that plays an important role in human's daily life. In this paper, we explore the formation of isolated communities in WDN based on complex network theory. A graph-algebraic model is proposed to effectively detect the potential communities due to pipeline failures. This model can properly illustrate the connectivity and evolution of WDN during different stages of contingency events, and identify the emerging isolated communities through spectral analysis on Laplacian matrix. A case study on a practical urban WDN in China is conducted, and the consistency between the simulation results and the historical data are reported to showcase the feasibility and effectiveness of the proposed model.
High-performance resistive switching characteristics of programmable metallization cell with oxidized Cu-Ti electrodes
Authors: Huang Yu-Chih , Chou Chia-Hsin , Liao Chan-Yu , Tsai Wan-Lin , Cheng Huang-Chung
Published: October 2013

Programmable metallization cell (PMC) memory devices with oxidized Cu-Ti alloy films as the bottom electrodes have been shown to exhibit a superior on/off state current ratio (memory window) of as high as 103 and endurance of 3000 cycles as compared to conventional pure copper and unoxidized Cu-Ti alloy electrodes. It was conjectured that the Cu-Ti alloy electrodes could obtain the appropriate amount of copper atoms to format and rupture the conductive filaments in the resistive switching layer. Furthermore, the oxidized Cu-Ti alloys could control the Cu cations from the Cu and Cu2O to the appropriate amountto achieve the most favorable PMC characteristics.
A proposal for an alternative class of spin filter materials: Hybridization-induced high-TC ferromagnetic semiconductors CoVXAl (X = Ti, Zr, Hf)
Authors: Galanakis I. , Özdoğan K. , Şaşıoğlu E.
Published: October 2013

Using ab-initio electronic structure calculations, we propose an alternative class of spin filter materials (SFMs) based on the quaternary Heusler compounds CoVXAl (X = Ti, Zr, Hf). We show that the p-d hybridization leads to the formation of the ferromagnetic band gap with a moderate exchange splitting ΔEex and a Curie temperature TC well above the room temperature. We find that all three compounds are thermodynamically and magnetically stable. Combination of high TC value together with moderate exchange splitting, as well as crystal structures compatible to the existing semiconductors and metals, makes these compounds promising candidates to find applications as SFMs in spintronics devices.
Excitonic emission dynamics in homoepitaxial AlN films studied using polarized and spatio-time-resolved cathodoluminescence measurements
Authors: Chichibu S. F. , Hazu K. , Ishikawa Y. , Tashiro M. , Ohtomo T. , Furusawa K. , Uedono A. , Mita S. , Xie J. , Collazo R. , Sitar Z.
Published: October 2013

Excitonic emission dynamics in homoepitaxial AlN films grown on a freestanding substrate prepared by the physical-vapor-transport method were examined. Reflecting the low threading dislocation density (<104 cm−2), room-temperature cathodoluminescence intensity images mapped at the free A-exciton energy exhibited homogeneous contrasts. Low-temperature cathodoluminescence peaks at 6.0415 and 6.0287 eV, which were polarized parallel and perpendicular, respectively, to the c-axis, exhibited identical risetimes and short lifetimes; the latter coincided with the temporal delay of neutral donor-bound exciton emissions. These results support the assumption that the two peaks originate from the recombination of free A-excitons of irreducible representations Γ1 and Γ5, respectively.
N-polar GaN etching and approaches to quasi-perfect micro-scale pyramid vertical light-emitting diodes array
Authors: Wang Liancheng , Ma Jun , Liu Zhiqiang , Yi Xiaoyan , Yuan Guodong , Wang Guohong
Published: October 2013

N-polar GaN etching process and mechanism has been investigated in detail by varying the etching parameter (etchant temperature, etchant concentration, and etching duration) in KOH and H3PO4. Quasi-perfect micro-scale hexagonal pyramids vertical light emitting diodes (μ-HP VLEDs) array with least active area loss (<12%) has been fabricated by N-polar etching. The μ-HP VLEDs shows massively improved crystal quality with X-ray diffraction full width at half maxima decreased from 442 s to 273 s, and the room temperature minority carriers decay time increased from 252 ps to 747 ps. Temperature dependence of photoluminescence result reveals a ∼30% improved internal quantum efficiency, and transmission electron microscope further reveals its quasi-perfect crystalline quality clearly.
Theoretical study of different attenuation measurement by acoustic microscopy
Authors: Hamdi F. , Bouhedja S. , Amrani H.
Published: October 2013

Many works are devoted to study the attenuation of surface waves in media, particularly, leaky surface acoustic waves (LSAW). In this work, a big part of the study is based on the intensity of the output signal, i.e., acoustic signature, V(z). The latter is obtained by the use of quantitative mode of acoustic microscopy in order to measure the velocity and the attenuation of those excited waves at the limit between the specimen and the coupling liquid. Our aim is to compare the attenuation values of the LSAW propagation in porous silicon obtained with three different methods. The first is obtained by resolving Viktorov equation. The second method is the spectral analysis acoustical signature V(z) curves. The third method uses the dark field. The obtained results are in a good agreement with those experiments.
A simplified, numerically verified model for the global plasma reaction on a local cooling
Authors: Tokar M. Z. , Koltunov M.
Published: October 2013

An analytical model for heat losses along a magnetic surface to its small region cooled down abruptly to a very low temperature is deduced by applying a principle of minimum entropy production and verified by comparing with the results obtained by solving non-stationary two-dimensional heat conduction equation numerically. The model is elaborated further by taking into account heat flux limit and the plasma density modification due to the particle convection along the magnetic surface, triggered by the plasma pressure imbalance arising by the local cooling.
Scaling law of electron confinement in a zero beta polywell device
Authors: Gummersall David V. , Carr Matthew , Cornish Scott , Kachan Joe
Published: October 2013

Orbital theory simulation was applied to an electron trap that uses a cube shaped magnetic cusp known as a Polywell device. The purpose of this device is to create a virtual cathode in order to achieve nuclear fusion using inertial electrostatic confinement. Analytical expressions of the electron confinement time and average position within the device were obtained in terms of the current in the field coils, the dimensions of the device, and the kinetic energy of the electrons. Comparisons with numerical simulations showed good agreement over a parameter range that spanned several orders of magnitude for the current. In addition, power loss from electrons exiting the trap was estimated in order to obtain minimum power requirement to maintain a virtual cathode within the device.
InGaAs/GaP quantum dot light-emitting diodes on Si
Authors: Song Yuncheng , Larry Lee Minjoo
Published: October 2013

We report on the growth, structure, and luminescence of In0.5Ga0.5As/GaP self-assembled quantum dots (SAQDs) on exact Si (001) by means of an epitaxial GaP/Si template. In situ reflection high-energy electron diffraction showed indistinguishable transitions during SAQD growth, indicating similar growth kinetics on GaP/Si and bulk GaP. In0.5Ga0.5As SAQD stacks on both substrates yielded nearly identical photoluminescence spectra, with peak position, peak-width, and integrated intensity varying by <5%. We then describe the characteristics of In0.5Ga0.5As/GaP SAQD light-emitting diodes on Si. These results demonstrate that combining In0.5Ga0.5As/GaP SAQDs with GaP/Si templates provides a novel path for monolithic integration of optoelectronics with Si.
Fast magnetization precession for perpendicularly magnetized MnAlGe epitaxial films with atomic layered structures
Authors: Mizukami S. , Sakuma A. , Kubota T. , Kondo Y. , Sugihara A. , Miyazaki T.
Published: October 2013

Epitaxial growth and magnetization precessional dynamics for tetragonal MnAlGe films are investigated. The films are grown on MgO (100) with c axis parallel to the film normal and well-ordered layered structures. The film exhibits rectangular hysteresis loop with perpendicular magnetic anisotropy constant of 4.7 Merg/cm3 and saturation magnetization of 250 emu/cm3. Magnetization precession with precession frequency of ∼100 GHz is observed by time-resolved magneto-optical Kerr effect. Further, the Gilbert damping constant is found to be less than ∼0.05, which is much larger than that obtained using the first principles calculations.
Alignment of cholesteric liquid crystals using the macroscopic flexoelectric polarization contribution to dielectric properties
Authors: Outram B. I. , Elston S. J.
Published: October 2013

By considering the contribution of flexoelectricity to a cholesteric liquid crystal's dielectric permittivity, we show that both flexoelectric and dielectric effects allow the alignment of the Uniform Lying Helix (ULH) in devices with in-plane-switching (IPS) electrodes. The non-uniformity of fields produced by IPS electrodes is found to be crucial to allow ULH formation. The ULH is stabilised using homeotropic alignment conditions without polymer networks. Thus, a framework has been developed and tested for aligning and making stable cholesteric liquid crystals that incorporates both flexoelectric and dielectric field effects. Applications include bistable and ultra-fast display technology.
Inertial coalescence of droplets on a partially wetting substrate
Authors: Sui Yi , Maglio Marco , Spelt Peter D. M. , Legendre Dominique , Ding Hang
Published: October 2013

We consider the growth rate of the height of the connecting bridge in rapid surface-tension-driven coalescence of two identical droplets attached on a partially wetting substrate. For a wide range of contact angle values, the height of the bridge grows with time following a power law with a universal exponent of 2/3, up to a threshold time, beyond which a 1/2 exponent results, that is known for coalescence of freely-suspended droplets. In a narrow range of contact angle values close to 90°, this threshold time rapidly vanishes and a 1/2 exponent results for a 90° contact angle. The argument is confirmed by three-dimensional numerical simulations based on a diffuse interface method with adaptive mesh refinement and a volume-of-fluid method.
Use of an open-ended coaxial cavity method to characterize powdery substances exposed to humidity
Authors: Tuhkala M. , Juuti J. , Jantunen H.
Published: October 2013

The effect of moisture adsorption in the characterization of dielectric powders by an indirectly coupled open-ended coaxial cavity method operating at 4.5 GHz was analyzed. SiO2, Al2O3, and ZrO2 powders were exposed to 5% and 100% relative humidity levels and Bruggeman symmetric, Looyenga, and General Mixing Model equations were used to determine changes in permittivity and loss tangent of the inclusions. Low moisture adsorption (0.1–2.5 vol. %) induced only a small change in inclusion permittivity but had a pronounced impact on dielectric losses. Calculated moisture percentages based on responses of the resonator and the General Mixing Model correlated well with traditional mass based determination. The presented characterization method exhibited high sensitivity for the determination of dielectric properties of powders and their moisture content to be further utilized in, e.g., process and quality monitoring.
Environmentally stable/self-powered ultraviolet photodetectors with high sensitivity
Authors: Yang Shengxue , Tongay Sefaattin , Li Shu-Shen , Xia Jian-Bai , Wu Junqiao , Li Jingbo
Published: October 2013

Here, we demonstrate self-powered ultraviolet photodetectors that are capable of generating opposite current flow when illuminated at different wavelengths. The photodetectors are composed of n-ZnO/Polyaniline (PANI) p-n and PANI/ZnGa2O4 type-II heterojunctions and operate without any need for external power source. Devices display superior stability in ambient conditions within months. Results provide opportunities for developing devices for optical recognition.
Intrinsic features of the magnetoeletric coupling mechanism in displacive multiferroics
Authors: Freitas V. F. , Montanher D. Z. , Bonadio T. G. M. , Mazzocchi V. L. , Mestnik-Filho J. , Parente C. B. R. , Garcia D. , Eiras J. A. , Cótica L. F. , Santos I. A.
Published: October 2013

Structural, ferroelectric, and magnetic arrangements, and electron density in the vicinity of cations, were modeled from high-resolution X-ray and neutron powder diffraction data in La modified BiFeO3-PbTiO3 compounds. Important features for controlling the intrinsic mechanism for the magnetoelectric coupling in these materials, as prototypes for perovskite structured magnetoelectric multiferroics, are pointed out and discussed. It is shown that the magnetoelectric coupling angle is governed by covalent-like forces, which also affect the structural and ferroelectric distortions in the unit cell.
Separation of semiconducting and ferromagnetic FeSi2-nanoparticles by magnetic filtering
Authors: Aigner Willi , Niesar Sabrina , Mehmedovic Ervin , Opel Matthias , Wagner Friedrich E. , Wiggers Hartmut , Stutzmann Martin
Published: October 2013

We have investigated the potential of solution-processed β-phase iron disilicide (FeSi2) nanoparticles as a novel semiconducting material for photovoltaic applications. Combined ultraviolet-visible absorption and photothermal deflection spectroscopy measurements have revealed a direct band gap of 0.85 eV and, therefore, a particularly high absorption in the near infrared. With the help of Fourier-transform infrared and X-ray photoelectron spectroscopy, we have observed that exposure to air primarily leads to the formation of a silicon oxide rather than iron oxide. Mössbauer measurements have confirmed that the nanoparticles possess a phase purity of more than 99%. To diminish the small fraction of metallic iron impurities, which were detected by superconducting quantum interference device magnetometry and which would act as unwanted Auger recombination centers, we present a novel concept to magnetically separate the FeSi2 nanoparticles (NPs). This process leads to a reduction of more than 95% of the iron impurities.
Deep-level transient spectroscopy of interfacial states in “buffer-free” p-i-n GaSb/GaAs devices
Authors: Aziz Mohsin , Ferrandis Philippe , Mesli Abdelmadjid , Hussain Mari Riaz , Francisco Felix Jorlandio , Sellai Azzouz , Jameel Dler , Al Saqri Noor , Khatab Almontaser , Taylor David , Henini Mohamed
Published: October 2013

A systematic study was carried out on defect states in Interfacial Misfit (IMF) unpassivated and Te-passivated IMF in p-i-n GaSb/GaAs devices using Deep Level Transient Spectroscopy (DLTS) and Laplace DLTS. Additionally, Current-Voltage (I–V) measurements were performed, which showed that the turn-on voltage (Von) of passivated samples is lower than that for unpassivated samples; an effect which can be explained by the introduction of new defects states near to the interface of GaSb/GaAs, where Te was incorporated to passivate the IMF. The Capacitance-Voltage (C-V) analysis demonstrates that these new states are the consequence of adding Te at the misfit of GaSb/GaAs. Furthermore, DLTS measurements reveal a distribution of states including a main midgap energy level, namely the well documented EL2 trap, with some peculiar behaviour. Most of these levels are related to interface states that are generated by the mismatch between GaAs and GaSb. Originally, the addition of Te atoms was thought to passivate these interface states. On the contrary, this paper, which attempts at correlating the current-voltage and capacitance-voltage characteristics to the DLTS results, shows clearly that Te atoms increase the density of interface states.
Preparation of Cu2ZnSnS4 thin film by a simple and cost effective route using metallic precursors and effect of selenization on these films
Authors: Pani Bhagyashre , Singh Udai P.
Published: October 2013

Kesterite-type CZTS (Cu2ZnSnS4) is an emerging absorber material to be used in thin film solar cells. Here, we report a simple and convenient route to synthesize CZTS thin film by using ball milled metallic precursors; paste preparation by using propylene glycol as binder despite of using too many chemicals which may lead to make it difficult to remove and reduce the chance formation of undesired organic carbon layer. This is a fast and uncomplicated synthesis route for preparing kesterite type CZTS film with promising properties. Samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, EDAX (Energy Dispersive X-ray Analysis) and UV-VIS-NIR spectrometer at different stages of work. Ball milling the metallic precursors, formed nano particles with little amount of crystallinity which was revealed from SAED (selected area electron diffraction) pattern of TEM of powder sample. We have fabricated CZTS thin film by Doctor's Blade method and film with kesterite structure with good crystallinity has been obtained by a two step annealing process in N2 gas atmosphere. From optical study, band gap of the prepared film was found to be 1.5 eV. The effect of selenization on annealed CZTS film has also been studied and reported. Results obtained from XRD spectrum after selenization have shown CZTS is converting into CZTSSe partially not completely upon selenization. All the analysis results confirmed the formation of compact CZTS thin film with increase of grain size and crystallinity percentage after annealing of films.
Nanoscale capacitance: A classical charge-dipole approximation
Authors: Lu Jun-Qiang , Gonzalez Jonathan , Sierra Carlos , Li Yang
Published: October 2013

Modeling nanoscale capacitance presents particular challenge because of dynamic contribution from electrodes, which can usually be neglected in modeling macroscopic capacitance and nanoscale conductance. We present a model to calculate capacitances of nano-gap configurations and define effective capacitances of nanoscale structures. The model is implemented by using a classical atomic charge-dipole approximation and applied to calculate capacitance of a carbon nanotube nano-gap and effective capacitance of a buckyball inside the nano-gap. Our results show that capacitance of the carbon nanotube nano-gap increases with length of electrodes which demonstrates the important roles played by the electrodes in dynamic properties of nanoscale circuits.
Calpain-dependent cytoskeletal rearrangement exploited for anthrax toxin endocytosis
Authors: Jeong Sun-Young , Martchenko Mikhail , Cohen Stanley N.
Published: October 2013

Significance

Bacillus anthracis
produces protein toxins that present a major biodefense challenge. Host genes exploited for toxin entry by pathogens are potential targets for therapies that circumvent resistance-inducing pathogen mutations. We report that (
i
) anthrax lethal toxin enters macrophages by associating with higher-order actin filaments that provide the dynamic force for membrane invagination during endocytic trafficking of integrin-containing focal adhesion complexes (FACs) and (
ii
) calpain-mediated cleavage of talin-1, which anchors FACs at the cell surface, facilitates such exploitation. Our findings elucidate steps of anthrax toxin endocytosis and identify a potential target for mitigation of toxicity.
Strategic maneuvering in the political rhetoric of Barack Obama
Authors: Kienpointner Manfred
Published: September 2013

U.S. President Barack Obama’s rhetoric lends itself well as a highly interesting case study for exploring the possibilities of contemporary political rhetoric of being both successful on the one hand and rational, according to normative standards of argumentative discourse, on the other. Taking up the concept of “strategic maneuvering” as developed within Pragma-Dialectics (cf. van Eemeren 2010), a corpus of Obama’s speeches and books is analyzed in order to assess both its rationality and efficiency. The analysis shows that Obama not only knows extremely well how to use the classical inventory of (political) rhetoric, but also tries to overcome the standard strategic maneuvering of political rhetoric which is often polarizing and destructive. Obama tries to change this traditional style of political rhetoric by his orientation towards consensus and universal values and by his willingness to practice self-criticism. The evaluation of Obama’s political rhetoric has also shown, however, that Obama is sometimes forced to abandon his high ethical and rhetorical standards in order not to lose a substantial section of the U.S. voters. In some of these cases, it might be argued that his strategic maneuvering “derails”. All in all, however, Obama has shown us that a leading contemporary politician can overcome traditional party rhetoric by following new types of strategic maneuvering which, at least sometimes, successfully reconcile normative standards of rational discussion with rhetorical principles of efficient persuasion. Keywords: Barack Obama; political rhetoric; democracy; Pragma-Dialectics; strategic maneuvering; fallacy; pragmatic argument; irony; self-criticism
Unruly actors: Latvian women of the Red Army in post-war historical memory
Authors: Eglitis Daina , Zelče Vita
Published: October 2013

This work highlights the case of Latvian women volunteers of the Red Army who worked and fought on the eastern fronts of World War II. An estimated 70,000–85,000 Latvians served in the Red Army, some as conscripts, others as volunteers. At least several hundred of those who volunteered were women. How are Latvian women volunteers of the Red Army represented and remembered in Soviet and post-Soviet historical accounts of World War II? Why have they not been remembered in most historical accounts of this period? How are ethnicity, gender, and associated social roles implicated in their historical marginality? These questions are situated in the context of literature on collective memory and microsociological literature on social roles, and used to develop the analytical concept of the unruly actor – historical actors who are challenges to dominant memory narratives because they fail to conform to normative social roles ascribed on the basis of, among others, gender and ethnicity. We use the case of Latvian women volunteers to articulate the argument that the marginality of some groups in dominant historical narratives can be understood in terms of their disruption of the historical “scene”, which is configured to reflect a desired social order.
Functional module identification in protein interaction networks by interaction patterns
Authors: Wang Yijie , Qian Xiaoning
Published: October 2013

Motivation: Identifying functional modules in protein–protein interaction (PPI) networks may shed light on cellular functional organization and thereafter underlying cellular mechanisms. Many existing module identification algorithms aim to detect densely connected groups of proteins as potential modules. However, based on this simple topological criterion of ‘higher than expected connectivity’, those algorithms may miss biologically meaningful modules of functional significance, in which proteins have similar interaction patterns to other proteins in networks but may not be densely connected to each other. A few blockmodel module identification algorithms have been proposed to address the problem but the lack of global optimum guarantee and the prohibitive computational complexity have been the bottleneck of their applications in real-world large-scale PPI networks.

Results: In this article, we propose a novel optimization formulation LCP2 (low two-hop conductance sets) using the concept of Markov random walk on graphs, which enables simultaneous identification of both dense and sparse modules based on protein interaction patterns in given networks through searching for LCP2 by random walk. A spectral approximate algorithm SLCP2 is derived to identify non-overlapping functional modules. Based on a bottom-up greedy strategy, we further extend LCP2 to a new algorithm (greedy algorithm for LCP2) GLCP2 to identify overlapping functional modules. We compare SLCP2 and GLCP2 with a range of state-of-the-art algorithms on synthetic networks and real-world PPI networks. The performance evaluation based on several criteria with respect to protein complex prediction, high level Gene Ontology term prediction and especially sparse module detection, has demonstrated that our algorithms based on searching for LCP2 outperform all other compared algorithms.

Availability and implementation: All data and code are available at http://www.cse.usf.edu/∼xqian/fmi/slcp2hop/.

Contact:  yijie@mail.usf.edu or xqian@ece.tamu.edu

Supplementary information:  Supplementary data are available at Bioinformatics online.
The intrinsic shapes of dwarf irregular galaxies
Authors: Roychowdhury Sambit , Chengalur Jayaram N. , Karachentsev Igor D. , Kaisina Elena I.
Published: October 2013

We use the measured B-band axial ratios of galaxies from an updated catalogue of Local Volume galaxies to determine the intrinsic shape of dwarf irregular galaxies (de Vaucouleurs’ morphological types 8–10). We find that the shapes change systematically with luminosity, with fainter galaxies being thicker. In particular, we divide our sample into sub-samples and find that the most luminous dwarfs (−19.6 < MB < −14.8) have thin discs (thickness ∼0.2), with the disc being slightly elliptical (axial ratio ∼0.8). At intermediate luminosity, viz. −14.8 < MB < −12.6, the galaxies are still characterized by elliptical discs (axial ratio ∼0.7), but the discs are somewhat thicker (thickness ∼0.4). The faintest dwarfs, viz. those with −12.6 < MB < −6.7 are well described as being oblate spheroids with an axial ratio ∼0.5. The increasing thickness of the stellar discs of dwarf irregulars with decreasing luminosity is compatible with the increasing ratio of velocity dispersion to rotational velocity with decreasing galaxy size.
Why ageing stops: heterogeneity explains late-life mortality deceleration in nematodes
Authors: Chen Hwei-yen , Zajitschek Felix , Maklakov Alexei A.
Published: October 2013

While ageing is commonly associated with exponential increase in mortality with age, mortality rates paradoxically decelerate late in life resulting in distinct mortality plateaus. Late-life mortality plateaus have been discovered in a broad variety of taxa, including humans, but their origin is hotly debated. One hypothesis argues that deceleration occurs because the individual probability of death stops increasing at very old ages, predicting the evolution of earlier onset of mortality plateaus under increased rate of extrinsic mortality. By contrast, heterogeneity theory suggests that mortality deceleration arises from individual differences in intrinsic lifelong robustness and predicts that variation in robustness between populations will result in differences in mortality deceleration. We used experimental evolution to directly test these predictions by independently manipulating extrinsic mortality rate (high or low) and mortality source (random death or condition-dependent) to create replicate populations of nematodes,
Caenorhabditis remanei
that differ in the strength of selection in late-life and in the level of lifelong robustness. Late-life mortality deceleration evolved in response to differences in mortality source when mortality rate was held constant, while there was no consistent response to differences in mortality rate. These results provide direct experimental support for the heterogeneity theory of late-life mortality deceleration.
Longevity suppresses conflict in animal societies
Authors: Port Markus , Cant Michael A.
Published: October 2013

Models of social conflict in animal societies generally assume that within-group conflict reduces the value of a communal resource. For many animals, however, the primary cost of conflict is increased mortality. We develop a simple inclusive fitness model of social conflict that takes this cost into account. We show that longevity substantially reduces the level of within-group conflict, which can lead to the evolution of peaceful animal societies if relatedness among group members is high. By contrast, peaceful outcomes are never possible in models where the primary cost of social conflict is resource depletion. Incorporating mortality costs into models of social conflict can explain why many animal societies are so remarkably peaceful despite great potential for conflict.
Economic investment by ant colonies in searches for better homes
Authors: Doran Carolina , Pearce Tom , Connor Aaron , Schlegel Thomas , Franklin Elizabeth , Sendova-Franks Ana B. , Franks Nigel R.
Published: October 2013

Organisms should invest more in gathering information when the pay-off from finding a profitable resource is likely to be greater. Here, we ask whether animal societies put more effort in scouting for a new nest when their current one is of low quality. We measured the scouting behaviour of
Temnothorax albipennis
ant colonies when they inhabit nest-sites with different combinations of desirable attributes. We show that the average probability of an ant scouting decreases significantly with an increase in the quality of the nest in which the colony currently resides. This means that the greater the potential gain from finding a new nest, the more effort a colony puts into gathering information regarding new nest-sites. Our results show, for the first time to our knowledge, the ability of animal societies to respond collectively to the quality of a resource they currently have at their disposal (e.g. current nest-site) and regulate appropriately their information gathering efforts for finding an alternative (e.g. a potentially better nest-site).
Multiple pathways mediate the sex-peptide-regulated switch in female
Drosophila
reproductive behaviours
Authors: Haussmann Irmgard U. , Hemani Yash , Wijesekera Thilini , Dauwalder Brigitte , Soller Matthias
Published: October 2013

Male-derived sex-peptide (SP) induces profound changes in the behaviour of
Drosophila
females, resulting in decreased receptivity to further mating and increased egg laying. SP can mediate the switch in female reproductive behaviours via a G protein-coupled receptor, SPR, in neurons expressing
fruitless
,
doublesex
and
pickpocket
. Whether SPR is the sole receptor and whether SP induces the postmating switch in a single pathway has not, to our knowledge been tested. Here we report that the SP response can be induced in the absence of SPR when SP is ectopically expressed in neurons or when SP, transferred by mating, can access neurons through a leaky blood brain barrier. Membrane-tethered SP can induce oviposition via
doublesex
, but not
fruitless
and
pickpocket
neurons in
SPR
mutant females. Although
pickpocket
and
doublesex
neurons rely on G(o) signalling to reduce receptivity and induce oviposition, G(o) signalling in
fruitless
neurons is required only to induce oviposition, but not to reduce receptivity. Our results show that SP's action in reducing receptivity and inducing oviposition can be separated in
fruitless
and
doublesex
neurons. Hence, the SP-induced postmating switch incorporates shared, but also distinct circuitry of
fruitless
,
doublesex
and
pickpocket
neurons and additional receptors.
Innate immune responses in raccoons after raccoon rabies virus infection
Authors: Srithayakumar Vythegi , Sribalachandran Hariharan , Rosatte Rick , Nadin-Davis Susan A. , Kyle Christopher J.
Published: October 2013

Zoonotic wildlife diseases pose significant health risks not only to their primary vectors but also to humans and domestic animals. Rabies is a lethal encephalitis caused by rabies virus (RV). This RNA virus can infect a range of terrestrial mammals but each viral variant persists in a particular reservoir host. Active management of these host vectors is needed to minimize the negative impacts of this disease, and an understanding of the immune response to RV infection aids strategies for host vaccination. Current knowledge of immune responses to RV infection comes primarily from rodent models in which an innate immune response triggers activation of several genes and signalling pathways. It is unclear, however, how well rodent models represent the immune response of natural hosts. This study investigates the innate immune response of a primary host, the raccoon, to a peripheral challenge using the raccoon rabies virus (RRV). The extent and temporal course of this response during RRV infection was analysed using genes predicted to be upregulated during infection (IFNs; IFN regulatory factors; IL-6; Toll like receptor-3; TNF receptor). We found that RRV activated components of the innate immune system, with changes in levels of transcripts correlated with presence of viral RNA. Our results suggest that natural reservoirs of rabies may not mimic the immune response triggered in rodent models, highlighting the need for further studies of infection in primary hosts.
Ultralow concentrations of bupivacaine exert anti‐inflammatory effects on inflammation‐reactive astrocytes
Authors: Block Linda , Jörneberg Per , Björklund Ulrika , Westerlund Anna , Biber Björn , Hansson Elisabeth
Published: October 2013

Bupivacaine is a widely used, local anesthetic agent that blocks voltage‐gated Na+ channels when used for neuro‐axial blockades. Much lower concentrations of bupivacaine than in normal clinical use, < 10−8 m, evoked Ca2+ transients in astrocytes from rat cerebral cortex, that were inositol trisphosphate receptor‐dependent. We investigated whether bupivacaine exerts an influence on the Ca2+ signaling and interleukin‐1β (IL‐1β) secretion in inflammation‐reactive astrocytes when used at ultralow concentrations, < 10−8 m. Furthermore, we wanted to determine if bupivacaine interacts with the opioid‐, 5‐hydroxytryptamine‐ (5‐HT) and glutamate‐receptor systems. With respect to the μ‐opioid‐ and 5‐HT‐receptor systems, bupivacaine restored the inflammation‐reactive astrocytes to their normal non‐inflammatory levels. With respect to the glutamate‐receptor system, bupivacaine, in combination with an ultralow concentration of the μ‐opioid receptor antagonist naloxone and μ‐opioid receptor agonists, restored the inflammation‐reactive astrocytes to their normal non‐inflammatory levels. Ultralow concentrations of bupivacaine attenuated the inflammation‐induced upregulation of IL‐1β secretion. The results indicate that bupivacaine interacts with the opioid‐, 5‐HT‐ and glutamate‐receptor systems by affecting Ca2+ signaling and IL‐1β release in inflammation‐reactive astrocytes. These results suggest that bupivacaine may be used at ultralow concentrations as an anti‐inflammatory drug, either alone or in combination with opioid agonists and ultralow concentrations of an opioid antagonist.
Minimax‐Optimal Strength of Statistical Evidence for a Composite Alternative Hypothesis
Authors: Bickel David R.
Published: October 2013

Le rapport de vraisemblance mesure l'évidence statistique, par rapport ô une hypothèse nulle, d'une contre‐hypothèse simple. Il n'existe pas d'équivalent direct dans le contexte d'hypothèses composées. Nous montrons comment, en traitant le paramètre d'intérêt comme une grandeur aléatoire, il est cependant possible d'évaluer l'évidence statistique d'une hypothèse composée sans passer par la spécification ni l'estimation d'une loi ni d'un a priori particuliers. Le fait de traiter le paramètre comme un quantité aléatoire traduit ici sa variabilité plutôt qu'une incertitude le concernant, et la mesure idéale de l'évidence en faveur de la contre‐hypothèse est la différence entre les logarithmes desoddsa posteriori et a priori. Cette mesure idéale peur être remplacée par toute mesure estimée, pourvu qu'elle soit asymptotiquement sans biais. Une telle méthode s'interprète aisément et, le cas échéant, peut être utilisée en combinaison avec un a priori, spécifié ou estimé, sur l'hypothèse nulle. Nous décrivons deux de ces mesures estimées présentant des propriétés d'optimalité de type minimax. Une application ô des données protéomiques indique que la modification d'une de ces mesures optimales portant sur les données relatives ô une protéine unique fournit une bonne approximation de la différence entre les logarithmes desoddsa posteriori et a priori en provenance de 20 protéines différentes.
Fingerprint‐Based Recognition
Authors: Dass Sarat C.
Published: October 2013

La reconnaissance biométrique, ou la biométrie, se rapporte à l'authentification d'une personne basée sur le son des traits biométriques. Parmi les divers traits biométriques (par exemple, visage, iris, empreinte digitale, voix), l'authentification basée sur empreinte a la plus longue histoire, et a été avec succès adoptée dans des applications légales et civiles. Les avances en technologie de capture d'empreinte digitale ont eu comme conséquence des applications civiles de nouvelle large échelle (par exemple, programme d'US‐VISIT). Cependant, ces systèmes rencontrent toujours des difficultés dues ànfacteurs de divers bruit actuels dans des environnements de fonctionnement. Il y a également un manque général de développement scientifique dans des méthodes légales, y compris des méthodes basées par empreinte digitale, en termes de sources d'identification, d'incorporation et de mesure de variabilité dans le processus décisionnel. Le but de cet article est de donner un aperçu de pratique en vigueur dans la reconnaissance basée sur empreinte, ses défis et les domaines de la future recherche.
Gumbel’s Identity, Binomial Moments, and Bonferroni Sums
Authors: Hoppe Fred M. , Seneta Eugene
Published: October 2013

L'identité de Gumbel établit l'égalité de la somme de Bonferroni Sk,n, k = 0, 1, 2, … , n et du moment binomial d'ordre k de la variable qui compte, dans un ensemble arbitraire de névénements, le nombre Mn d'événements se réalisant. Nous présentons un traitement unifié de bornes bien connues obtenues dans ce contexte par Bonferroni, Galambos‐Rényi, Dawson‐Sankoff et Chung‐Erdös, ainsi que de quelques bornes moins connues établies par Fréchet et Gumbel. Toutes font intervenir des sommes de Bonferroni. Notre démarche consiste à montrer que ces bornes apparaissent dans un cadre plus général comme les moments binomiaux d'une variable aléatoire à valeurs entières particulière. L'application de l'identité de Gumbel fournit alors la forme usuelle en termes de sommes de Bonferroni. Notre approche simplifie les preuves existantes, et permet d'étendre les résultats de Fréchet et Gumbel au cas de la probabilité pour qu'au moins t, 1 ≤t≤n des névénements considérés se réalisent. Une dernière conséquence de notre approche est l'amélioration d'une borne de Petrov qui elle‐même est la généralisation de la borne de Chung et Erdös.
Evaluating, Comparing, Monitoring, and Improving Representativeness of Survey Response Through R‐Indicators and Partial R‐Indicators
Authors: Schouten Barry , Bethlehem Jelke , Beullens Koen , Kleven Øyvin , Loosveldt Geert , Luiten Annemieke , Rutar Katja , Shlomo Natalie , Skinner Chris
Published: October 2013

Non‐response is a common source of error in many surveys. Because surveys often are costly instruments, quality‐cost trade‐offs play a continuing role in the design and analysis of surveys. The advances of telephone, computers, and Internet all had and still have considerable impact on the design of surveys. Recently, a strong focus on methods for survey data collection monitoring and tailoring has emerged as a new paradigm to efficiently reduce non‐response error. Paradata and adaptive survey designs are key words in these new developments. Prerequisites to evaluating, comparing, monitoring, and improving quality of survey response are a conceptual framework for representative survey response, indicators to measure deviations thereof, and indicators to identify subpopulations that need increased effort. In this paper, we present an overview of representativeness indicators or R‐indicators that are fit for these purposes. We give several examples and provide guidelines for their use in practice.
Mechanisms for hyperthermal polyatomic hydrocarbon modification of PMMA surfaces from molecular dynamics simulations
Authors: Choudhary Kamal , Hill Leah B. , Kemper Travis W. , Sinnott Susan B.
Published: October 2013

Classical molecular dynamics simulations are performed to determine the mechanisms by which hyperthermal hydrocarbon polyatomics, which are present in low-energy plasmas, chemically modify polymer surfaces. In particular, C2H, CH3, and C3H5 are deposited on an amorphous poly (methyl methacrylate) (PMMA) substrate with kinetic energies of 4, 10, 25, and 50 eV and compared to the deposition of H at the same energies. The short-range forces on the atoms are determined using the second generation reactive empirical many-body potential, while the long-range forces are determined using a Lennard-Jones potential. The simulations predict that at all these incident energies, the chemical modification of the PMMA is limited to within a nanometer of the surface. Atoms, fragments, and incident polyatomics are further predicted to chemically attach to specific sites on the PMMA monomers at low energies and to attach to a wider range of sites at higher energies. However, no appreciable cross-linking between polymer chains is predicted to occur. Variation in the penetration depth of the deposited polyatomics or H is correlated to differences in their size and bond saturation. The greatest extent of chemical modification of the PMMA surface slab is achieved for C2H deposition with 50 eV of kinetic energy.
Design and performance of a compact and stationary microSPECT system
Authors: Van Holen Roel , Vandeghinste Bert , Deprez Karel , Vandenberghe Stefaan
Published: October 2013

Purpose:

Over the last ten years, there has been an extensive growth in the development of microSPECT imagers. Most of the systems are based on the combination of conventional, relatively large gamma cameras with poor intrinsic spatial resolution and multipinhole collimators working in large magnification mode. Spatial resolutions range from 0.58 to 0.76 mm while peak sensitivities vary from 0.06% to 0.4%. While pushing the limits of performance is of major importance, the authors believe that there is a need for smaller and less complex systems that bring along a reduced cost. While low footprint and low‐cost systems can make microSPECT available to more researchers, the ease of operation and calibration and low maintenance cost are additional factors that can facilitate the use of microSPECT in molecular imaging. In this paper, the authors simulate the performance of a microSPECT imager that combines high space‐bandwidth detectors and pinholes with truncated projection, resulting in a small and stationary system.

Methods:

A system optimization algorithm is used to determine the optimal SPECT systems, given our high resolutions detectors and a fixed field‐of‐view. These optimal system geometries are then used to simulate a Defrise disk phantom and a hot rod phantom. Finally, a MOBY mouse phantom, with realistic concentrations of Tc99m‐tetrofosmin is simulated.

Results:

Results show that the authors can successfully reconstruct a Defrise disk phantom of 24 mm in diameter without any rotating system components or translation of the object. Reconstructed spatial resolution is approximately 800 μm while the peak sensitivity is 0.23%. Finally, the simulation of the MOBY mouse phantom shows that the authors can accurately reconstruct mouse images.

Conclusions:

These results show that pinholes with truncated projections can be used in small magnification or minification mode to obtain a compact and stationary microSPECT system. The authors showed that they can reach state‐of‐the‐art system performance and can successfully reconstruct images with realistic noise levels in a preclinical context. Such a system can be useful for dynamic SPECT imaging.
Sticking with the Pattern for a Safer Glue
Authors: Artzi Natalie
Published: October 2013

Surface micropatterning and reactive chemistry are used to develop adhesive materials with adequate adhesion and reduced toxicity.
B Lymphocytes: Adding Insult to Injury After Myocardial Infarction
Authors: Zidar David A.
Published: October 2013

Pathologic remodeling of the heart after myocardial infarction is mediated by B2 lymphocyte secretion of CCL-7, leading to recruitment of a harmful type of monocyte.