bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation network coding
Authors: Ngangue Ndih Eugène David , Cherkaoui Soumaya
Published: October 2013

In this study, we propose a four‐dimensional modulation, referred to as modulation network coding (MNC), to address the problem of decoding a signal from multiple source node transmissions in mobile fast fading channels. The MNC scheme judiciously mixes a two‐dimensional (2D) pilot symbol with a 2D information symbol, and makes use of a π/4 rotated M‐pulse‐amplitude modulation (PAM) constellation to guaranty an effective decoding of all the interfering symbols even in the case of a smaller channel Doppler spread compared with the period of the MNC symbol. In addition, because the MNC scheme makes use of an additional dimension introduced through orthogonal pulse waveform, the use of the pilot symbols does not reduce the effective information rate. The analytical and simulation results show that it is possible to achieve a low symbol error probability with a good signal‐to‐noise ratio when controlling a few parameters impacting the performance of the system such as the synchronisation in time and in frequency of the source nodes.
Stabilisation for one‐sided Lipschitz non‐linear differential inclusions
Authors: Cai Xiushan , Lin Yuhang , Hong Shuyue
Published: October 2013

Stabilisation design methods for one‐sided Lipschitz non‐linear differential inclusions are considered in this study. Sufficient conditions of exponential stabilisation for the closed‐loop system are given by solving linear matrix inequalities. Two kinds of continuous control laws are designed such that the closed‐loop systems are exponentially stable at the origin, respectively. Finally, two numerical examples are given to illustrate the effectiveness of the proposed design technique.
Primary control level of parallel distributed energy resources converters in system of multiple interconnected autonomous microgrids within self‐healing networks
Authors: Shahnia Farhad , Chandrasena Ruwan P.S. , Rajakaruna Sumedha , Ghosh Arindam
Published: October 2013

To minimise the number of load sheddings in a microgrid (MG) during autonomous operation, islanded neighbour MGs can be interconnected if they are on a self‐healing network and an extra generation capacity is available in the distributed energy resources (DER) of one of the MGs. In this way, the total load in the system of interconnected MGs can be shared by all the DERs within those MGs. However, for this purpose, carefully designed self‐healing and supply restoration control algorithm, protection systems and communication infrastructure are required at the network and MG levels. In this study, first, a hierarchical control structure is discussed for interconnecting the neighbour autonomous MGs where the introduced primary control level is the main focus of this study. Through the developed primary control level, this study demonstrates how the parallel DERs in the system of multiple interconnected autonomous MGs can properly share the load of the system. This controller is designed such that the converter‐interfaced DERs operate in a voltage‐controlled mode following a decentralised power sharing algorithm based on droop control. DER converters are controlled based on a per‐phase technique instead of a conventional direct‐quadratic transformation technique. In addition, linear quadratic regulator‐based state feedback controllers, which are more stable than conventional proportional integrator controllers, are utilised to prevent instability and weak dynamic performances of the DERs when autonomous MGs are interconnected. The efficacy of the primary control level of the DERs in the system of multiple interconnected autonomous MGs is validated through the PSCAD/EMTDC simulations considering detailed dynamic models of DERs and converters.
Radiation characteristics improvement of aperture coupled antennas using double reflector structure
Authors: Oraizi Homayoon , Reza Pazoki
Published: October 2013

The radiation characteristics of aperture stacked patch antenna, namely, front‐to‐back (F/B) ratio, gain, and gain bandwidth are improved. The results show that the gain bandwidth of the proposed antenna is up to 72% (6.09–12.87 GHz) with F/B ratio better than 8 dB across the band of operation which is a considerable improvement compared to the available microstrip antennas.
Improved multilevel physical optics algorithm for fast computation of monostatic radar cross section
Authors: An Yuyuan , Wang Daoxiang , Chen Rushan
Published: October 2013

This paper proposes an acceleration technique to fast evaluate the monostatic radar cross section (RCS) with the multilevel physical optics (MLPO) algorithm. The proposed method combines the adaptive cross approximation (ACA) algorithm with the MLPO to fast evaluate two‐dimensional monostatic RCS (two‐dimensional monostatic RCS over a range of elevation angles θ and azimuths angles φ at a fixed frequency f, or a range of frequencies f and azimuths angles φ at a fixed elevation angle θ) responses. Owing to the phase compensation in the MLPO, the matrix corresponding to the compensated back‐scattered field of each group is highly rank‐deficient, which is compressed with ACA in a multilevel fashion therefore a lot of central processing unit time will be saved. The rank‐deficiency, accuracy and computational complexity of the proposed method have been studied through a couple of numerical examples, which illustrate the effectiveness of the proposed approach.
Electrostatically driven and capacitively detected differential lateral resonant pressure microsensor
Authors: Jiao Hailong , Xie Bo , Wang Junbo , Chen Deyong , Chen Jian
Published: October 2013

Presented is the design, fabrication and characterisation of an electrostatic‐driving and capacitive‐detection differential resonant pressure microsensor. The differential structure consists of two resonators immobilised on the diaphragm. In response to the pressure under measurement, the diaphragm deflection increases the intrinsic resonant frequency of one resonant beam and decreases the resonant frequency of the other. A differential frequency output reduces the common frequency drift caused by stresses and interferences, and thus improves the sensor's stability. The device geometries were optimised using numerical simulations and the fabrication process was based on a silicon‐on‐insulator wafer requiring only two masks with simplified microfabrication steps (e.g. sputter, wet etching and deep reactive ion etching). The sensor was quantified in an open‐loop characterisation platform, producing a quality factor higher than 10 430 in vacuum (< 0.5 Pa). Closed‐loop test results recorded a linear resonant frequency shift (a linear correlation of 0.9999) in response to applied pressure, with a sensitivity of 227 Hz/kPa. This resonant pressure microsensor has a simple fabrication process and reliable performance, and can be used for pressure monitoring in various locations including weather stations and aerospace.
Stability of fluctuating and transient aggregates of amphiphilic solutes in aqueous binary mixtures: Studies of dimethylsulfoxide, ethanol, and tert-butyl alcohol
Authors: Banerjee Saikat , Bagchi Biman
Published: October 2013

In aqueous binary mixtures, amphiphilic solutes such as dimethylsulfoxide (DMSO), ethanol, tert-butyl alcohol (TBA), etc., are known to form aggregates (or large clusters) at small to intermediate solute concentrations. These aggregates are transient in nature. Although the system remains homogeneous on macroscopic length and time scales, the microheterogeneous aggregation may profoundly affect the properties of the mixture in several distinct ways, particularly if the survival times of the aggregates are longer than density relaxation times of the binary liquid. Here we propose a theoretical scheme to quantify the lifetime and thus the stability of these microheterogeneous clusters, and apply the scheme to calculate the same for water–ethanol, water–DMSO, and water–TBA mixtures. We show that the lifetime of these clusters can range from less than a picosecond (ps) for ethanol clusters to few tens of ps for DMSO and TBA clusters. This helps explaining the absence of a strong composition dependent anomaly in water–ethanol mixtures but the presence of the same in water–DMSO and water–TBA mixtures.
Numerical simulations of spatially developing, accelerating boundary layers
Authors: Piomelli Ugo , Yuan Junlin
Published: October 2013

We present the results of direct and large-eddy simulations of spatially developing boundary layers subjected to favorable pressure gradient, strong enough to cause reversion of the flow towards a quasi-laminar state. The numerical results compare well with experimental data. Visualization of the flow structures shows the well-known stabilization of the streaks, the re-orientation of outer layer vortices in the streamwise direction, and the appearance of turbulent spots in the re-transition region. Both instantaneous visualizations and turbulent statistics highlight the significant damping of wall-normal and spanwise fluctuations. The fast component of the pressure fluctuations appears to be the main driver of this process, contributing to reduce pressure fluctuations and, as a consequence, the energy redistribution term in the Reynolds stress budgets. The streamwise stresses, in whose budget a separate production term plays a role, do not decay but remain frozen at their upstream value. The decrease of wall-normal and spanwise fluctuations appears to be the main cause of the inner-layer stabilization, by disrupting the generation and subsequent growth of streaks, consistent with various models of the turbulence-generation cycle proposed in the literature. The outer layer seems to play a passive role in this process. The stretching and reorientation of the outer-layer vortices results in a more orderly and organized structure; since fewer ejections occur, the inner layer does not break this re-organization, which is maintained until re-transition begins.
Correlations and Werner states in finite spin linear arrays
Authors: Wells P. R. , Chaves C. M. , d'Albuquerque e Castro J. , Koiller Belita
Published: October 2013

Pairwise quantum correlations in the ground state of an N-spins antiferromagnetic Heisenberg chain are investigated. By varying the exchange coupling between two neighboring sites, it is possible to reversibly drive spins from entangled to disentangled states. For even N, the two-spin density matrix is written in the form of a Werner state, allowing identification of its single parameter with the usual spin-spin correlation function. The N = 4 chain is identified as a promising system for practical demonstrations of non-classical correlations and the realization of Werner states in familiar condensed matter systems. Fabrication and measurement ingredients are within current capabilities.
Three-dimensional closed-loop control of self-propelled microjets
Authors: Khalil Islam S. M. , Magdanz Veronika , Sanchez Samuel , Schmidt Oliver G. , Misra Sarthak
Published: October 2013

We demonstrate precise closed-loop control of microjets under the influence of the magnetic fields in three-dimensional (3D) space. For this purpose, we design a magnetic-based control system that directs the field lines towards reference positions. Microjets align along the controlled field lines using the magnetic torque exerted on their magnetic dipole, and move towards the reference positions using their self-propulsion force. We demonstrate the controlled motion of microjets in 3D space, and show that their propulsion force allows them to overcome vertical forces, such as buoyancy forces, interaction forces with oxygen bubbles, and vertical flow. The closed-loop control localizes the microjets within a spherical region of convergence with an average diameter of 406±220 μm, whereas the self-propulsion force allows them to swim at an average speed of 222±74 μm/s within the horizontal plane. Furthermore, we observe that the controlled microjets dive downward and swim upward towards reference positions at average speeds of 232±40 μm/s and 316±81 μm/s, respectively.
Germanium oxynitride gate interlayer dielectric formed on Ge(100) using decoupled plasma nitridation
Authors: Bhatt Piyush , Chaudhuri Krishnakali , Kothari Shraddha , Nainani Aneesh , Lodha Saurabh
Published: October 2013

Germanium Oxynitride (GeON) gate interlayer (IL) dielectric formed using decoupled plasma nitridation (DPN) technique is compared with GeO2 and thermally nitrided GeON ILs for Ge gate stack applications using n-channel capacitors and transistors. Lower nitrogen concentration and roughness at the GeON/Ge interface lead to lower midgap interface trap density (Dit) and 1.5× higher electron mobility for the DPN versus thermally nitrided GeON IL. DPN GeON IL also exhibits enhanced thermal stability till 575 °C at the expense of a small degradation in Dit versus GeO2 IL, making it a more viable gate IL dielectric on Ge channels.
Variationally localized search direction method for constrained optimization of non-orthogonal, localized orbitals in electronic structure calculations
Authors: Ruiz-Serrano Álvaro , Skylaris Chris-Kriton
Published: October 2013

A new method for the constrained optimization of non-orthogonal, spatially localized orbitals using direct energy minimization techniques, in the context of electronic structure calculations, is presented. The variationally localized search direction (VLSD) method, as it was named, ensures that strict localization constraints are imposed upon the search direction vectors exactly, analytically and in a fully variational fashion. In contrast, the truncated search direction (TSD) method, of standard use in many electronic structure approaches with localization constraints, relies on the approximation that the truncated search direction vectors of the unconstrained problem resemble the exact search direction vectors of the constrained problem. With the TSD method, in order to maintain the localization constraints, a part of the pre-calculated information that is stored in the search direction vectors has to be deleted via an ad hoc, non-variational truncation step. The results on an extensive set of test molecules show that, in general, calculations with the VLSD method require less iterations to converge than with the TSD method for any size of the localization region. It was found that in calculations on certain systems where the TSD method is forced to delete a very large amount of information, the VLSD method is capable of achieving convergence in up to three times less iterations. Validation tests show that structural and electronic properties calculated with either method are accurate and in agreement with other electronic structure approaches.
Modelling of hysteretic behavior of piezoceramic materials under electrical loading
Authors: Domenjoud Mathieu , Bustillo Julien , Lethiecq Marc , Tran-Huu-Hue Louis-Pascal
Published: October 2013

The purpose of this study is to model the hysteretic behavior of piezoceramic materials under electrical loading. Remanent strain and remanent polarization are chosen as internal variables. A domain orientation distribution is used to describe the evolution of these variables by bridging the characteristics of microscopic domain distribution into macroscopic behaviors. This model is able to calculate electric displacement, longitudinal, and transversal strains as a function of uniaxial electrical field. Good quality of the formulation is demonstrated through comparison with experimental data of the literature. In addition, results confirm our hypothesis of isochoric deformation of piezoceramics under electrical loading.
Tension moderation and fluctuation spectrum in simulated lipid membranes under an applied electric potential
Authors: Loubet Bastien , Lomholt Michael Andersen , Khandelia Himanshu
Published: October 2013

We investigate the effect of an applied electric potential on the mechanics of a coarse grained POPC bilayer under tension. The size and duration of our simulations allow for a detailed and accurate study of the fluctuations. Effects on the fluctuation spectrum, tension, bending rigidity, and bilayer thickness are investigated in detail. In particular, the least square fitting technique is used to calculate the fluctuation spectra. The simulations confirm a recently proposed theory that the effect of an applied electric potential on the membrane will be moderated by the elastic properties of the membrane. In agreement with the theory, we find that the larger the initial tension the larger the effect of the electric potential. Application of the electric potential increases the amplitude of the long wavelength part of the spectrum and the bending rigidity is deduced from the short wavelength fluctuations. The effect of the applied electric potential on the bending rigidity is non-existent within error bars. However, when the membrane is stretched there is a point where the bending rigidity is lowered due to a decrease of the thickness of the membrane. All these effects should prove important for mechanosensitive channels and biomembrane mechanics in general.
The impact of mechanical stress on the degradation of AlGaN/GaN high electron mobility transistors
Authors: Choi Sukwon , Heller Eric , Dorsey Donald , Vetury Ramakrishna , Graham Samuel
Published: October 2013

Coupled electro-thermo-mechanical simulation and Raman thermometry were utilized to analyze the evolution of mechanical stress in AlGaN/GaN high electron mobility transistors (HEMTs). This combined analysis was correlated with electrical step stress tests to determine the influence of mechanical stress on the degradation of actual devices under diverse bias conditions. It was found that the total stress as opposed to one dominant stress component correlated the best with the degradation of the HEMT devices. These results suggest that minimizing the total stress as opposed to the inverse piezoelectric stress in the device is necessary in order to avoid device degradation which can be accomplished through various growth methods.
Evidence for critical scaling of plasmonic modes at the percolation threshold in metallic nanostructures
Authors: Metin Akinoglu Eser , Sun Tianyi , Gao Jinwei , Giersig Michael , Ren Zhifeng , Kempa Krzysztof
Published: October 2013

In this work we provide the experimental demonstration of critical scaling of plasmonic resonances in a percolation series of periodic structures which evolve from arrays of holes to arrays of quasi-triangles. Our observations are in agreement with the general percolation theory and could lead to sensor and detector applications.
Influence of grain boundary on electrical properties of organic crystalline grains investigated by dual-probe atomic force microscopy
Authors: Hirose Masaharu , Tsunemi Eika , Kobayashi Kei , Yamada Hirofumi
Published: October 2013

We performed electrical transport measurements on α-sexithiophene crystalline grains using a dual-probe atomic force microscopy system having two independently controlled cantilever probes. The field-effect transistor characteristics were measured by varying the distances between the two probes brought in contact with the surface of the grains. It was clearly shown by the transfer line method that the grain boundary is the dominant factor limiting the electrical properties of organic thin films. Moreover, the hole transport across the grain boundary was found to be more affected by the oxygen hole doping than that within the crystalline grain.
Periodicity of resonant tunneling current induced by the Stark resonances in semiconductor nanowire
Authors: Wołoszyn M. , Adamowski J. , Wójcik P. , Spisak B. J.
Published: October 2013

The modification of the electronic current resulting from Stark resonances has been studied for the semiconductor nanowire with the double-barrier structure. Based on the calculated current-voltage characteristics, we have shown that the resonant tunneling current is a periodic function of the width of the spacer layer. We have also demonstrated that the simultaneous change of the source-drain voltage and the voltage applied to the gate located near the nanowire leads to almost periodic changes of the resonant tunneling current as a function of the source-drain and gate voltages. The periodic properties of the resonant tunneling current result from the formation of the Stark resonance states. If we change the electric field acting in the nanowire, the Stark states periodically acquire the energies from the transport window and enhance the tunneling current in a periodic manner. We have found that the separations between the resonant current peaks on the source-drain voltage scale can be described by a slowly increasing linear function of the Stark state quantum number. This allows us to identify the quantum states that are responsible for the enhancement of the resonant tunneling. We have proposed a method of the experimental observation of the Stark resonances in semiconductor double-barrier heterostructures.
Effective medium approximations for anisotropic composites with arbitrary component orientation
Authors: Levy Ohad , Cherkaev Elena
Published: October 2013

A Maxwell Garnett approximation (MGA) and a symmetric effective medium approximation (SEMA) are derived for anisotropic composites of host-inclusion and symmetric-grains morphologies, respectively, with ellipsoidal grains of arbitrary intrinsic, shape and orientation anisotropies. The effect of anisotropy on the effective dielectric tensor is illustrated in both cases. The MGA shows negative and non-monotonic off-diagonal elements for geometries where the host and inclusions are not mutually aligned. The SEMA leads to an anisotropy-dependent nonlinear behaviour of the conductivity as a function of volume fraction above a percolation threshold of conductor-insulator composites, in contrast to the well-known linear behaviour of the isotropic effective medium model. The percolation threshold obtained for composites of aligned ellipsoids is isotropic and independent of the ellipsoids aspect ratio. Thus, the common identification of the percolation threshold with the depolarization factors of the grains is unjustified and a description of anisotropic percolation requires explicit anisotropic geometric characteristics.
Strong exciton confinement in site-controlled GaN quantum dots embedded in nanowires
Authors: Choi Kihyun , Kako Satoshi , Holmes Mark J. , Arita Munetaka , Arakawa Yasuhiko
Published: October 2013

The optical properties of site-controlled single GaN quantum dots (QDs) embedded in nanowires are presented. These properties are largely determined by a strong carrier confinement due to the small size of the dots (0.5 ∼ 1 nm in height). The QDs emit in the deep-ultraviolet region of the electromagnetic spectrum and exhibit the biexciton binding energy of 52 meV, which is the largest value ever reported in III-V semiconductor QDs. Furthermore, the dots luminesce at room-temperature and have short exciton decay times of ∼300 ps due to an increased oscillator strength. These findings indicate that these site-controlled QDs are promising for various applications in quantum information devices.
Existence and non-existence of breather solutions in damped and driven nonlinear lattices
Authors: Hennig D.
Published: October 2013

We investigate the existence of spatially localised solutions, in the form of discrete breathers, in general damped and driven nonlinear lattice systems of coupled oscillators. Conditions for the exponential decay of the difference between the maximal and minimal amplitudes of the oscillators are provided which proves that initial non-uniform spatial patterns representing breathers attain exponentially fast a spatially uniform state preventing the formation and/or preservation of any breather solution at all. Strikingly our results are generic in the sense that they hold for arbitrarydimension of the system, any attractive interaction, coupling strength and on-site potential and general driving fields. Furthermore, our rigorous quantitative results establish conditions under which discrete breathers in general damped and driven nonlinear lattices can exist at all and open the way for further research on the emergent dynamical scenarios, in particular features of pattern formation, localisation and synchronisation, in coupled cell networks.
Bidirectional coupling between integrin-mediated signaling and actomyosin mechanics explains matrix-dependent intermittency of leading-edge motility
Authors: Welf Erik S. , Johnson Heath E. , Haugh Jason M.
Published: October 2013

Animal cell migration is a complex process characterized by the coupling of adhesion, cytoskeletal, and signaling dynamics. Here we model local protrusion of the cell edge as a function of the load-bearing properties of integrin-based adhesions, actin polymerization fostered by adhesion-mediated signaling, and mechanosensitive activation of RhoA that promotes myosin II–generated stress on the lamellipodial F-actin network. Analysis of stochastic model simulations illustrates how these pleiotropic functions of nascent adhesions may be integrated to govern temporal persistence and frequency of protrusions. The simulations give mechanistic insight into the documented effects of extracellular matrix density and myosin abundance, and they show characteristic, nonnormal distributions of protrusion duration times that are similar to those extracted from live-cell imaging experiments. Analysis of the model further predicts relationships between measurable quantities that reflect the partitioning of stress between tension on F-actin–bound adhesions, which act as a molecular clutch, and dissipation by retrograde F-actin flow.
ER-associated SNAREs and Sey1p mediate nuclear fusion at two distinct steps during yeast mating
Authors: Rogers Jason V. , Arlow Tim , Inkellis Elizabeth R. , Koo Timothy S. , Rose Mark D.
Published: October 2013

During yeast mating, two haploid nuclei fuse membranes to form a single diploid nucleus. However, the known proteins required for nuclear fusion are unlikely to function as direct fusogens (i.e., they are unlikely to directly catalyze lipid bilayer fusion) based on their predicted structure and localization. Therefore we screened known fusogens from vesicle trafficking (soluble N-ethylmaleimide–sensitive factor attachment protein receptors [SNAREs]) and homotypic endoplasmic reticulum (ER) fusion (Sey1p) for additional roles in nuclear fusion. Here we demonstrate that the ER-localized SNAREs Sec20p, Ufe1p, Use1p, and Bos1p are required for efficient nuclear fusion. In contrast, Sey1p is required indirectly for nuclear fusion; sey1Δ zygotes accumulate ER at the zone of cell fusion, causing a block in nuclear congression. However, double mutants of Sey1p and Sec20p, Ufe1p, or Use1p, but not Bos1p, display extreme ER morphology defects, worse than either single mutant, suggesting that retrograde SNAREs fuse ER in the absence of Sey1p. Together these data demonstrate that SNAREs mediate nuclear fusion, ER fusion after cell fusion is necessary to complete nuclear congression, and there exists a SNARE-mediated, Sey1p-independent ER fusion pathway.
Selection methods regulate evolution of cooperation in digital evolution
Authors: Lichocki Paweł , Floreano Dario , Keller Laurent
Published: October 2013

A key, yet often neglected, component of digital evolution and evolutionary models is the ‘selection method’ which assigns fitness (number of offspring) to individuals based on their performance scores (efficiency in performing tasks). Here, we study with formal analysis and numerical experiments the evolution of cooperation under the five most common selection methods (proportionate, rank, truncation-proportionate, truncation-uniform and tournament). We consider related individuals engaging in a Prisoner's Dilemma game where individuals can either cooperate or defect. A cooperator pays a cost, whereas its partner receives a benefit, which affect their performance scores. These performance scores are translated into fitness by one of the five selection methods. We show that cooperation is positively associated with the relatedness between individuals under all selection methods. By contrast, the change in the performance benefit of cooperation affects the populations’ average level of cooperation only under the proportionate methods. We also demonstrate that the truncation and tournament methods may introduce negative frequency-dependence and lead to the evolution of polymorphic populations. Using the example of the evolution of cooperation, we show that the choice of selection method, though it is often marginalized, can considerably affect the evolutionary dynamics.
Reorientation patterns in central-place foraging: internal clocks and klinokinesis
Authors: Campos Daniel , Bartumeus Frederic , Méndez Vicenç , Espadaler Xavier
Published: October 2013

We study central-place foraging patterns of
Aphaenogaster senilis
ants at a population level by video framing individual ant trajectories in a circular arena with a nest connected to its centre. The ants naturally leave and enter the nest and forage generating non-trivial movement patterns around the nest. Our data analysis indicated that the trajectories observed can be classified into two strategies: the
risk-averse
strategy, which involves wandering around the nest without departing far from it and the
risk-prone
strategy, which involves long exploration paths with periodic returns to the central region, nearby the nest. We found that both
risk-prone
and
risk-averse
strategies exhibit qualitatively the same reorientation patterns, with the time between consecutive reorientations covering a wide range of scales, and fitting a stretched exponential function. Nevertheless, differences in the temporal scales and the time variability of such reorientation events differ, together with other aspects of motion, such as average speed and turns. Our results give experimental evidence that the internal mechanisms driving reorientations in ants tend to favour frequently long relocations, as theory predicts for efficient exploration in patchy landscapes, but ants engaged in central-place foraging can modulate such behaviour to control distances from the nest. Previous works on the species support the idea that
risk-prone
and
risk-averse
strategies may reflect actual differences between individuals age and experience; these factors (age and experience) should be then relevant in modulating the internal reorientation clocks. To support the validity of our findings, we develop a random-walk model combining stretched exponential reorientation clocks with klinokinesis that fits the time length and the travelled distance distributions of the observed trajectories.
When to approach novel prey cues? Social learning strategies in frog-eating bats
Authors: Jones Patricia L. , Ryan Michael J. , Flores Victoria , Page Rachel A.
Published: October 2013

Animals can use different sources of information when making decisions. Foraging animals often have access to both self-acquired and socially acquired information about prey. The fringe-lipped bat,
Trachops cirrhosus
, hunts frogs by approaching the calls that frogs produce to attract mates. We examined how the reliability of self-acquired prey cues affects social learning of novel prey cues. We trained bats to associate an artificial acoustic cue (mobile phone ringtone) with food rewards. Bats were assigned to treatments in which the trained cue was either an unreliable indicator of reward (rewarded 50% of the presentations) or a reliable indicator (rewarded 100% of the presentations), and they were exposed to a conspecific tutor foraging on a reliable (rewarded 100%) novel cue or to the novel cue with no tutor. Bats whose trained cue was unreliable and who had a tutor were significantly more likely to preferentially approach the novel cue when compared with bats whose trained cue was reliable, and to bats that had no tutor. Reliability of self-acquired prey cues therefore affects social learning of novel prey cues by frog-eating bats. Examining when animals use social information to learn about novel prey is key to understanding the social transmission of foraging innovations.
Role of carbonic anhydrases in pathogenic micro-organisms: a focus on Aspergillus fumigatus
Authors: Tobal Jaqueline Moisés , Balieiro Márcia Eliana da Silva Ferreira
Published: October 2013

Aspergillus fumigatusis a ubiquitous saprophytic fungus responsible for organic material decomposition, and plays an important role in recycling environmental carbon and nitrogen. Besides its important role in the environment, this fungus has been reported as one of the most important fungal pathogens in immunocompromised patients. Due to changes in CO2concentration that some pathogens face during the infection process, studies have been undertaken to understand the pathogenic roles of carbonic anhydrases (CAs), well-known CO2hydration catalytic enzymes. As a basis for a discussion of the possible roles of CAs inA. fumigatuspathogenicity, this review describes the main characteristics of theA. fumigatusinfection and the challenges for its treatment. In addition, it gathers findings from studies with CA inhibitor drugs as anti-infective agents in different pathogens.
Biological and genetic factors regulating natural competence in a bacterial plant pathogen
Authors: Kung Stephanie H. , Almeida Rodrigo P. P.
Published: October 2013

For naturally competent bacteria, spatially structured growth can provide an environment for enhanced horizontal gene transfer through transformation and recombination. DNA is often present in the extracellular environment, such as in the extracellular matrix of biofilms, and the lysis of a single cell can result in high local DNA concentrations. Xylella fastidiosa is a naturally competent plant pathogen that typically lives in a surface-attached state, yet previous work characterizing the competence of this organism was conducted with planktonic cells in liquid environments. Here, we show that transformation and recombination efficiencies are two to three orders of magnitude higher for cells grown on solid compared with liquid media, with maximum recombination efficiencies of about 10−3. Cells were highly competent throughout their exponential growth phase, with no significant change in recombination efficiencies until population growth rates began to slow. Mutations in type IV pili, competency-related, and cell–cell signalling genes significantly impacted the ability of X. fastidiosa to acquire and incorporate DNA. Because X. fastidiosa is highly competent when growing in a surface-attached state, as it does within its insect vectors and host plants, recombination of naturally transformed DNA could be a significant route by which horizontal gene transfer occurs in natural environments.
Cell Growth Defect Factor1/CHAPERONE-LIKE PROTEIN OF POR1 Plays a Role in Stabilization of Light-Dependent Protochlorophyllide Oxidoreductase in Nicotiana benthamiana and Arabidopsis
Authors: Lee Jae-Yong , Lee Ho-Seok , Song Ji-Young , Jung Young Jun , Reinbothe Steffen , Park Youn-Il , Lee Sang Yeol , Pai Hyun-Sook
Published: October 2013

Angiosperms require light for chlorophyll biosynthesis because one reaction in the pathway, the reduction of protochlorophyllide (Pchlide) to chlorophyllide, is catalyzed by the light-dependent protochlorophyllide oxidoreductase (POR). Here, we report that Cell growth defect factor1 (Cdf1), renamed here as CHAPERONE-LIKE PROTEIN OF POR1 (CPP1), an essential protein for chloroplast development, plays a role in the regulation of POR stability and function. Cdf1/CPP1 contains a J-like domain and three transmembrane domains, is localized in the thylakoid and envelope membranes, and interacts with POR isoforms in chloroplasts. CPP1 can stabilize POR proteins with its holdase chaperone activity. CPP1 deficiency results in diminished POR protein accumulation and defective chlorophyll synthesis, leading to photobleaching and growth inhibition of plants under light conditions. CPP1 depletion also causes reduced POR accumulation in etioplasts of dark-grown plants and as a result impairs the formation of prolamellar bodies, which subsequently affects chloroplast biogenesis upon illumination. Furthermore, in cyanobacteria, the CPP1 homolog critically regulates POR accumulation and chlorophyll synthesis under high-light conditions, in which the dark-operative Pchlide oxidoreductase is repressed by its oxygen sensitivity. These findings and the ubiquitous presence of CPP1 in oxygenic photosynthetic organisms suggest the conserved nature of CPP1 function in the regulation of POR.
Present and future perspectives of virtual chromoendoscopy with i‐scan and optical enhancement technology
Authors: Neumann Helmut , Fujishiro Mitsuhiro , Wilcox C. Mel , Mönkemüller Klaus
Published: October 2013

Despite being the current gold standard, white‐light endoscopy may miss a significant proportion of lesions within the colorectum, thus leading to a misinterpretation of various disease findings. Traditionally, dye‐based chromoendoscopy is used to improve both detection and characterization of lesions during luminal gastrointestinal (GI) endoscopy. Recently introduced dye‐less chromoendoscopy (DLC) techniques have overcome many of the limitations of dye‐based chromoendoscopy, thereby potentially improving lesion recognition and characterization. In detail, DLC techniques allow for better detection of esophageal lesions, gastric cancer and colorectal pathologies including colorectalpolyps and inflammatory bowel diseases. Moreover, DLC techniques enable a more precise characterization of lesions throughout the whole luminal GI tract, thereby potentially enabling more accurate endoscopic therapies. In the present review we focus on the newly introduced dye‐less chromoendoscopy technique i‐scan and give an additional outlook on the recent development of optical enhancement technology.
Edaravone Improves Functional and Structural Outcomes in Animal Models of Focal Cerebral Ischemia: A Systematic Review
Authors: Wu Simiao , Sena Emily , Egan Kieren , Macleod Malcolm , Mead Gillian
Published: October 2013

Edaravone has been used in patients with acute ischemic stroke in Japan for over 10 years but does not have marketing authorization in Europe or America. Either patients in Europe and America are not receiving an effective treatment, or those in Asia are being given a treatment which is not effective. Finding out which of these is true will require further clinical trials, and a better understanding of its efficacy in animal models may help inform the design of those trials so that it might be tested under conditions where there is the greatest prospect of success. We systematically reviewed the efficacy of edaravone in animal models of focal ischemia and summarized data using weighted mean difference DerSimonian and Laird random-effects modeling. We used stratified meta-analysis and metaregression to assess the influence of study design and methodological quality. We identified 49 experiments describing outcome in 814 animals; 30 experiments (519 animals) reported functional and 35 experiments (503 animals) reported structural outcome. Edaravone improved functional and structural outcome by 30.3% (95% confidence interval 23.4–37.2%) and 25.5% (95% confidence interval, 21.1–29.9%), respectively. For functional outcome, there was an inverse relationship between study quality and effect size ( P < 0.0017). Effect sizes were larger in studies where randomization or blinded assessment was not reported. There was no evidence of publication bias. Edaravone is a promising treatment for stroke. However, because of the methodological weakness in current animal studies, no sufficient preclinical evidence is available to optimize the study design of clinical trials. Higher quality animal studies are expected to inform further clinical study.
A Comparative Analysis of Risk Factors and Stroke Risk for Asian and Non-Asian Men: The Asia Pacific Cohort Studies Collaboration
Authors: Hyun Karice K. , Huxley Rachel R. , Arima Hisatomi , Woo Jean , Lam Tai Hing , Ueshima Hirotsugu , Fang Xianghua , Peters Sanne A. E. , Jee Sun Ha , Giles Graham G. , Barzi Federica , Woodward Mark
Published: October 2013

Background

The risk of stroke is high in men among both Asian and non-Asian populations, despite differences in risk factor profiles; whether risk factors act similarly in these populations is unknown.

Aim

To study the associations between five major risk factors and stroke risk, comparing Asian with non-Asian men.

Methods

We obtained data from the Asia Pacific Cohort Studies Collaboration, a pooled analysis of individual participant data from 44 studies involving 386 411 men with 9·4 years follow-up. Using cohorts from Asia and Australia/New Zealand Cox models were fitted to estimate risk factor associations for ischemic and haemorrhagic stroke.

Results

We identified significant, positive associations between all five risk factors and risk of ischemic stroke. The associations between body mass index, smoking, and diabetes with ischemic stroke were comparable for men from Asia and Australia/New Zealand. The association between systolic blood pressure and ischemic stroke was stronger for Asian than Australia/New Zealand cohorts, whereas the reverse was true for total cholesterol. For haemorrhagic stroke, only systolic blood pressure and smoking were associated with increased risk, although the relationship with systolic blood pressure was significantly stronger for men from Asia than Australia/New Zealand ( Pinteraction = 0·03), whereas the reverse was true for smoking ( Pinteraction = 0·001). There was an inverse trend of total cholesterol with haemorrhagic stroke, significant only for Asian men.

Conclusions

Men from the Asia-Pacific region share common risk factors for stroke. Strategies aimed at lowering population levels of systolic blood pressure, total cholesterol, body mass index, smoking, and diabetes are likely to be beneficial in reducing stroke risk, particularly for ischemic stroke, across the region.
A spatiotemporal pattern analysis of historical mountain pine beetle outbreaks in British Columbia, Canada
Authors: Chen Huapeng
Published: October 2013

This study documents the spatiotemporal patterns of mountain pine beetle infestations by applying a novel approach based on a landscape infestation dynamics conceptual model in combination with morphological spatial pattern analysis using the mountain pine beetle infested pine mortality data (1960–2010) collected by the annual British Columbia aerial overview survey. The pattern analysis at the provincial level reveals that the 1980s outbreak did not crash as originally thought. The current outbreak is most likely a result of the progressive buildup of the epidemic infestations during the transition period (1985–1995) under favourable weather conditions and substantially improved host resources. This is also true for the Northeast and Cariboo areas of the province specifically, even though the infestations in the Cariboo area remained at incipient‐epidemic levels during the transition period after the 1980s outbreak crashed in 1985. In the Southeast area, the current outbreak apparently continued from the outbreak that initiated in the late 1970s and early 1980s. The 1980s outbreak originated from multiple spatially separate locations whereas the current outbreak initiated from a single location in Tweedsmuir Provincial Park. The centralized and self‐amplifying buildup of the current outbreak implicates at least three substantial expansions that occurred in 2002, 2006, and 2008. This study suggests that at the provincial level, as well as for the Northeast and Southeast areas of the province, the current outbreak is declining but most likely will continue for many years given the ongoing and future warming climate and a large proportion of pines that remain in the habitats of mountain pine beetles. This study also suggests that dispersals, particularly long‐distance dispersal, may play a key role in driving the spread and expansion of the current outbreak although uncertainty remains due to the local dynamics of the beetle populations.
A national cross‐sectional study measuring predictors for improved service user outcomes across clinical nurse or midwife specialist, advanced nurse practitioner and control sites
Authors: Comiskey Catherine , Coyne Imelda , Lalor Joan , Begley Cecily
Published: October 2013

Aim

The aim was to identify key patient outcomes and to compare these outcomes across services that employed clinical specialists (either nurse or midwife) or advanced nurse practitioners with matched, non post‐holding services.

Background

In nursing and evaluation research, it is recognized that, further patient outcome studies, which measure and evaluate the impact of the new advanced roles, are urgently needed.

Design

A cross‐sectional study design with a comparison group was implemented across Ireland.

Method

A total of 279 surveys were completed by service users in 41 services in 2009/10. Key outcomes were identified, then chosen as primary outcomes and assessed for differences across post‐holding and the matched comparison sites. To identify the priority of importance of the key outcomes, a logistic regression model was computed with difference in overall care observed (yes or no) as the dependent variable, and gender, age grouping and the key outcomes as the independent predictors.

Results

Analysis revealed that the key outcomes were, on anxieties, dignity and respect, time waited, confidence in the clinician and the clinician making a positive difference. Results of the logistic modelling of the key outcome on noticing any difference in the care given by the clinical specialists or advanced nurse practitioners compared with the care from others revealed that the single most important predictor was being treated with respect.

Conclusion

Further studies evaluating advanced health professions roles measuring these six key outcomes, at a minimum, will ensure that service users' main concerns are being accounted for.
Money, Margins and the Motors of Politics: The EU and the Development of Party Politics in Central and Eastern Europe
Authors: Haughton Tim
Published: October 2013

In line with expectations EU membership has only a limited impact on party politics in the new Member States of central and eastern Europe (CEE); even the economic crisis has not altered this level of impact. An examination of party positioning, party appeals and party competition indicates the EU plays the role of a boundary keeper, a reference point and a weapon to be invoked in domestic competition, particularly to lambast opponents for their incompetence, especially when it comes to the ability to access and manage EU funds. Underlying parties' stances on European integration are the deep‐rooted vulnerabilities which help explain why the CEE states recognize the necessity of co‐operation and a pooling of sovereignty at the European level.