bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron bunching from a dc-biased, single-surface multipactor with realistically broad energy spectrum and emission angle of secondary electrons
Authors: Shin Dongwon , Jeon Seok-Gy , Kim Jung-Il , Kim Geun-Ju , Hur Min Sup
Published: February 2012

We studied the influences of wide energy spectrum and emission angle of secondary electrons on electron bunching from a dc-biased single surface multipactor. In our previous study of the same system, an ideally narrow energy spread of secondary electrons without emission angle was used in the analysis of the electron trajectory [M. S. Hur, J.-I. Kim, G.-J. Kim, and S.-G. Jeon, Phys. Plasmas 18, 033103 (2011) and S.-G. Jeon, J.-I. Kim, S.-T. Han, S.-S. Jung, and J. U. Kim, Phys. Plasmas 16, 073101 (2009)]. In this paper, we investigated the cases with realistic energy spectrum, which is featured by a wide energy spread and significant emission angle. To theoretically approach the matter of emission angle, we employed a concept of effective longitudinal velocity distribution. The theoretical results are verified by particle-in-cell (PIC) simulations. We also studied the electron bunching from a copper by PIC simulations, where we observed stable electron bunches with bunch width of approximately 80 μm.
Pure optical and reversible optically driven nanowriting of azobenzene block copolymers
Authors: Tantussi F. , Menghetti S. , Caldi E. , Fuso F. , Allegrini M. , Galli G.
Published: February 2012

We report on pure optical nanowriting in the near-field of spin-coated films of a specifically synthesized azobenzene-containing block copolymer. Writing is accomplished by linear polarized blue laser radiation, which is efficiently absorbed by the material, and readout is based on polarization-modulation of red laser radiation, which is practically unabsorbed. Purely optical, stable, and reversible modifications are observed at the ∼100 nm scale. Remarkably, they are not accompanied by any observable topographical change. We attribute the result to the use of a small azobenzene content (3% mol) and to the block architecture of the material.
Environmental chamber for in situ dynamic control of temperature and relative humidity during x-ray scattering
Authors: Salas-de la Cruz David , Denis Jeffrey G. , Griffith Matthew D. , King Daniel R. , Heiney Paul A. , Winey Karen I.
Published: February 2012

We have designed, constructed, and evaluated an environmental chamber that has in situ dynamic control of temperature (25 to 90 °C) and relative humidity (0% to 95%). The compact specimen chamber is designed for x-ray scattering in transmission with an escape angle of 2θ = ±30°. The specimen chamber is compatible with a completely evacuated system such as the Rigaku PSAXS system, in which the specimen chamber is placed inside a larger evacuated chamber (flight path). It is also compatible with x-ray systems consisting of evacuated flight tubes separated by small air gaps for sample placement. When attached to a linear motor (vertical displacement), the environmental chamber can access multiple sample positions. The temperature and relative humidity inside the specimen chamber are controlled by passing a mixture of dry and saturated gas through the chamber and by heating the chamber walls. Alternatively, the chamber can be used to control the gaseous environment without humidity. To illustrate the value of this apparatus, we have probed morphology transformations in Nafion® membranes and a polymerized ionic liquid as a function of relative humidity in nitrogen.
Evolution of SiHx hydrides during the phase transition from amorphous to nanocrystalline silicon films
Authors: Garozzo C. , Puglisi R. A. , Bongiorno C. , Spinella C. , Mirabella S. , Reitano R. , Marco S. Di , Foti M. , Lombardo S.
Published: February 2012

This paper investigates the morphological evolution of hydrogenated amorphous silicon layers obtained by plasma enhanced chemical vapor deposition at different H dilutions in the regime close to the formation of the nanocrystalline phase. The role of hydrogen in the transition from the amorphous to the crystalline phase is investigated by accurate structural and chemical characterization, from the early stages of nucleation, where the nuclei present size slightly larger than the critical nucleus, i.e., about 0.8 nm in radius, up to the formation of crystalline grains larger than 30 nm in radius. A correlation between the structural characteristics of such crystalline phase and the bonding mechanism of Si with H through multiple hydrides, such as Si-H2 and Si-H3 is found, particularly the tri-hydrides are found to be directly correlated to the shape and the size of the nanocrystallites present in the films. The multiple hydrides are found to play a role also in the electrical characteristics of p-i-n a-Si:H solar cells whose intrinsic layer is realized in the above H dilution conditions. An explanation of the experimental data in terms of the different bonding mechanism of H in the Si matrix is provided.
Symmetric and asymmetric equilibria with non-parallel flows
Authors: Kuiroukidis Ap , Throumoulopoulos G. N.
Published: February 2012

Several classes of analytic solutions to a generalized Grad-Shafranov equation with incompressible plasma flow non-parallel to the magnetic field are constructed. The solutions include higher transcendental functions such as the Meijer G-function and describe D-shaped and diverted configurations with either a single or double X-points. Their characteristics are examined in particular with respect to the flow parameters associated with the electric field. It turns out that the electric field makes the safety factor flatter and increases the magnitude and shear of the toroidal velocity in qualitative agreement with experimental evidence on the formation of internal transport barriers in tokamaks, thus indicating a potential stabilizing effect of the electric field.
Modeling metastabilities in chalcopyrite-based thin film solar cells
Authors: Decock Koen , Zabierowski Paweł , Burgelman Marc
Published: February 2012

Cu(In,Ga)Se2-based thin film solar cell devices exhibit metastable electrical behavior. This behavior is often ascribed to intrinsic defects that can change configuration accompanied by large lattice relaxations. We extended the thin film solar cell simulation software scaps to enable the simulation of the metastable behavior of this kind of defects. The statistics that are needed to describe metastable defects are discussed. The procedure that has been implemented is introduced, and special attention is paid to the convergence of the method for high defect densities. The model is demonstrated by simulating the effect of voltage induced metastabilities on the capacitance-voltage characteristics. Some of the features present in the measured apparent doping density profiles can be directly related to presence of metastable defects.
Characterizing the charge collection efficiency in bulk heterojunction organic photovoltaic cells
Authors: Pandey Richa , Holmes Russell J.
Published: February 2012

We demonstrate a technique for determining the charge collection efficiency (ηCC) in bulk heterojunction organic photovoltaic cells (OPVs). To extract ηCC, we describe an approach to measure the optical absorption efficiency by examining the external quantum efficiency under reverse bias. Using estimates of the exciton diffusion efficiency obtained from photoluminescence quenching measurements, ηCC is calculated without any input from optical field simulations. For bulk heterojunction OPVs based on the donor-acceptor pairing of boron subphthalocyanine chloride and C60, a peak ηCC of (79 ± 2)% is realized for films containing 80 wt. % C60 under short-circuit conditions. This optimum composition also coincides with a peak in the fill factor and the short-circuit current density.
Approaching the bulk limit with finite cluster calculations using local increments: The case of LiH
Authors: Stoll Hermann , Doll Klaus
Published: February 2012

Finite-cluster calculations employing high-level wavefunction-based ab initio methods and extended atomic-orbital basis sets are used to determine local energy increments for bulk LiH. It is shown that these increments can be converged with respect to cluster size and point-charge embedding so as to yield bulk cohesive energies with an accuracy of better than 1 mEh, both at the Hartree-Fock and at correlated levels. Instrumental for the efficiency of the scheme is the introduction of non-orthogonal orbitals, at an intermediate stage.
High efficiency organic solar cells with spray coated active layers comprised of a low band gap conjugated polymer
Authors: Nie Wanyi , Coffin Robert C. , Liu Jiwen , Li Yuan , Peterson Eric D. , MacNeill Christopher M. , Noftle Ronald E. , Carroll David L.
Published: February 2012

Airbrush is a promising tool for large scale organic thin film deposition in photovoltaic devices fabrication. This paper reports a detailed study on solar cell performance using airbrush spray deposition for active layer composed with recently developed low band gap donor material poly[4,8-bis(1-pentylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-2,1,3-benzoxadiazole-4,7-diyl and [6,6]-phenyl-C61-butyric acid methyl ester. The effect of carrier solvent and substrate temperature on film morphology are studied; a formula in 1,2-dichlorobenzene sprayed at a substrate temperature of 80 °C is found to be the optimum condition that produces a peak power conversion efficiency of 5.8%.
Kinetic modeling for biodiesel production by heterogeneous catalysis
Authors: Agarwal Madhu , Singh Kailash , Chaurasia S. P.
Published: February 2012

Kinetic mechanism of heterogeneously catalyzed transesterification process for production of biodiesel from vegetable oils has been proposed and validated by experimental data generated and the data available in literature. An Eley–Rideal type of mechanism was proposed, and unknown kinetic parameters were determined using non linear regression. A good fit of experimental data and proposed mechanism was found with adsorption equilibrium constant value of 0.01 (m3/mol)3 and surface reaction equilibrium constant value of 0.001 (mol/m3)2. However, the value of desorption equilibrium constant for glycerol is in the range of 105–106 m3/mol. The adsorption kinetic constant varies from 0.001 to 0.024 (m3/mol)3(mol/kg.cat.s).
Guided filament formation in NiO-resistive random access memory by embedding gold nanoparticles
Authors: Uenuma Mutsunori , Zheng Bin , Kawano Kentaro , Horita Masahiro , Ishikawa Yasuaki , Yamashita Ichiro , Uraoka Yukiharu
Published: February 2012

Controllable positioning of conductive filament in resistive memory is demonstrated using gold nanoparticles (GNPs). A GNP of 15 nm diameter is encapsulated by the porter protein and delivered to the designated positions. The restricted nanoscale filament formation by the GNP was observed by conductive atomic force microscopy, and writing and erasing were achieved in a defined area on the nanometer scale. The GNPs act as defect creators and assist the formation of nanoscale filaments with a low voltage.
Negative-bias-temperature-instability and hot carrier effects in nanowire junctionless p-channel multigate transistors
Authors: Tae Park Jong , Young Kim Jin , Pierre Colinge Jean
Published: February 2012

Negative-bias-temperature-instability (NBTI) and hot-carrier induced device degradation have been experimentally compared between accumulation mode (AM) p-channel multigate transistors (pMuGFETs) and junctionless (JL) pMuGFET. NBTI degradation is less significant in junctionless pMuGFETs than AM pMuGFETs. The threshold voltage shift is less significant in junctionless transistors than AM transistors. The device simulation shows that the peak of lateral electric field and the impact ionization rate of AM device are larger than those of junctionless devices.
Multimodal strong coupling of photonic crystal cavities of dissimilar size
Authors: Dündar Mehmet A. , Voorbraak Joost A. M. , Nötzel Richard , Fiore Andrea , van der Heijden Rob W.
Published: February 2012

A photonic crystal three missing holes nanocavity, having only a few modes, is coupled to a 60 missing holes long multimode cavity, both fabricated in the same InGaAsP membrane. The coupling was studied in detail by the photothermal tuning of the small cavity over about three free spectral ranges of the large cavity. Strong coupling effects, involving at least three large cavity modes simultaneously, were observed from level anticrossing data. The observations are excellently reproduced by a model of coupled Fabry Perot resonators.
Acacia tortilis (Forssk.) subsp. raddiana (Savi) Brenan as a foundation species: a test from the arid zone of Tunisia
Authors: Noumi Zouhaier , Abdallah Lotfi , Touzard Blaise , Chaieb Mohamed
Published: February 2012

The geographic distribution of Acacia tortilis (Forssk.) Hayne subsp. raddiana (Savi) Brenan in Tunisia, is limited to the Bou-Hedma region (Bled Talah) where the National Park of Bou-Hedma, a UNESCO (1986) biosphere reserve, is located. We have tested the hypothesis that A. tortilis acts as a foundation species as a result of the improvement of soil conditions under its canopy (soil water availability and nutrient enrichment). The herbaceous community (floristic composition, species density, species richness) and soil characteristics (soil nutrients and soil water) were sampled using the quadrat method beneath and between 16 adult trees of A. tortilis with both northwards and southwards (south and north sides) and eight open areas among the trees. Results showed that A. tortilis trees improve soil water availability, the nutrient status of soil (organic matter, total carbon, total nitrogen, extractable phosphorus), and has a positive effect on the understorey vegetation under arid conditions. No significant differences in species richness were observed between the north subhabitats and the south subhabitats.
Chromosome segregation in Archaea mediated by a hybrid DNA partition machine
Authors: Kalliomaa-Sanford Anne K. , Rodriguez-Castañeda Fernando A. , McLeod Brett N. , Latorre-Roselló Victor , Smith Jasmine H. , Reimann Julia , Albers Sonja V. , Barillà Daniela
Published: February 2012

Eukarya and, more recently, some bacteria have been shown to rely on a cytoskeleton-based apparatus to drive chromosome segregation. In contrast, the factors and mechanisms underpinning this fundamental process are underexplored in archaea, the third domain of life. Here we establish that the archaeon
Sulfolobus solfataricus
harbors a hybrid segrosome consisting of two interacting proteins, SegA and SegB, that play a key role in genome segregation in this organism. SegA is an ortholog of bacterial, Walker-type ParA proteins, whereas SegB is an archaea-specific factor lacking sequence identity to either eukaryotic or bacterial proteins, but sharing homology with a cluster of uncharacterized factors conserved in both crenarchaea and euryarchaea, the two major archaeal sub-phyla. We show that SegA is an ATPase that polymerizes in vitro and that SegB is a site-specific DNA-binding protein contacting palindromic sequences located upstream of the
segAB
cassette. SegB interacts with SegA in the presence of nucleotides and dramatically affects its polymerization dynamics. Our data demonstrate that SegB strongly stimulates SegA polymerization, possibly by promoting SegA nucleation and accelerating polymer growth. Increased expression levels of
segAB
resulted in severe growth and chromosome segregation defects, including formation of anucleate cells, compact nucleoids confined to one half of the cell compartment and fragmented nucleoids. The overall picture emerging from our findings indicates that the SegAB complex fulfills a crucial function in chromosome segregation and is the prototype of a DNA partition machine widespread across archaea.
Permian vegetational Pompeii from Inner Mongolia and its implications for landscape paleoecology and paleobiogeography of Cathaysia
Authors: Wang Jun , Pfefferkorn Hermann W. , Zhang Yi , Feng Zhuo
Published: February 2012

Plant communities of the geologic past can be reconstructed with high fidelity only if they were preserved in place in an instant in time. Here we report such a flora from an early Permian (ca. 298 Ma) ash-fall tuff in Inner Mongolia, a time interval and area where such information is filling a large gap of knowledge. About 1,000 m
2
of forest growing on peat could be reconstructed based on the actual location of individual plants. Tree ferns formed a lower canopy and either
Cordaites
, a coniferophyte, or
Sigillaria
, a lycopsid, were present as taller trees. Noeggerathiales, an enigmatic and extinct spore-bearing plant group of small trees, is represented by three species that have been found as nearly complete specimens and are presented in reconstructions in their plant community. Landscape heterogenity is apparent, including one site where Noeggerathiales are dominant. This peat-forming flora is also taxonomically distinct from those growing on clastic soils in the same area and during the same time interval. This Permian flora demonstrates both similarities and differences to floras of the same age in Europe and North America and confirms the distinct character of the Cathaysian floral realm. Therefore, this flora will serve as a baseline for the study of other fossil floras in East Asia and the early Permian globally that will be needed for a better understanding of paleoclimate evolution through time.
Early millet use in northern China
Authors: Yang Xiaoyan , Wan Zhiwei , Perry Linda , Lu Houyuan , Wang Qiang , Zhao Chaohong , Li Jun , Xie Fei , Yu Jincheng , Cui Tianxing , Wang Tao , Li Mingqi , Ge Quansheng
Published: February 2012

It is generally understood that foxtail millet and broomcorn millet were initially domesticated in Northern China where they eventually became the dominant plant food crops. The rarity of older archaeological sites and archaeobotanical work in the region, however, renders both the origins of these plants and their processes of domestication poorly understood. Here we present ancient starch grain assemblages recovered from cultural deposits, including carbonized residues adhering to an early pottery sherd as well as grinding stone tools excavated from the sites of Nanzhuangtou (11.5–11.0 cal kyBP) and Donghulin (11.0–9.5 cal kyBP) in the North China Plain. Our data extend the record of millet use in China by nearly 1,000 y, and the record of foxtail millet in the region by at least two millennia. The patterning of starch residues within the samples allow for the formulation of the hypothesis that foxtail millets were cultivated for an extended period of two millennia, during which this crop plant appears to have been undergoing domestication. Future research in the region will help clarify the processes in place.
Negative feedback confers mutational robustness in yeast transcription factor regulation
Authors: Denby Charles M. , Im Joo Hyun , Yu Richard C. , Pesce C. Gustavo , Brem Rachel B.
Published: February 2012

Organismal fitness depends on the ability of gene networks to function robustly in the face of environmental and genetic perturbations. Understanding the mechanisms of this stability is one of the key aims of modern systems biology. Dissecting the basis of robustness to mutation has proven a particular challenge, with most experimental models relying on artificial DNA sequence variants engineered in the laboratory. In this work, we hypothesized that negative regulatory feedback could stabilize gene expression against the disruptions that arise from natural genetic variation. We screened yeast transcription factors for feedback and used the results to establish ROX1 (
R
epressor of hyp
OX
ia) as a model system for the study of feedback in circuit behaviors and its impact across genetically heterogeneous populations. Mutagenesis experiments revealed the mechanism of Rox1 as a direct transcriptional repressor at its own gene, enabling a regulatory program of rapid induction during environmental change that reached a plateau of moderate steady-state expression. Additionally, in a given environmental condition, Rox1 levels varied widely across genetically distinct strains; the ROX1 feedback loop regulated this variation, in that the range of expression levels across genetic backgrounds showed greater spread in ROX1 feedback mutants than among strains with the ROX1 feedback loop intact. Our findings indicate that the ROX1 feedback circuit is tuned to respond to perturbations arising from natural genetic variation in addition to its role in induction behavior. We suggest that regulatory feedback may be an important element of the network architectures that confer mutational robustness across biology.
Extreme sarcoplasmic reticulum volume loss and compensatory T-tubule remodeling after
Serca2
knockout
Authors: Swift Fredrik , Franzini-Armstrong Clara , Øyehaug Leiv , Enger Ulla Helene , Andersson Kristin Brevik , Christensen Geir , Sejersted Ole M. , Louch William E.
Published: February 2012

Cardiomyocyte contraction and relaxation are controlled by Ca
2+
handling, which can be regulated to meet demand. Indeed, major reduction in sarcoplasmic reticulum (SR) function in mice with
Serca2
knockout (KO) is compensated by enhanced plasmalemmal Ca
2+
fluxes. Here we investigate whether altered Ca
2+
fluxes are facilitated by reorganization of cardiomyocyte ultrastructure. Hearts were fixed for electron microscopy and enzymatically dissociated for confocal microscopy and electrophysiology. SR relative surface area and volume densities were reduced by 63% and 76%, indicating marked loss and collapse of the free SR in KO. Although overall cardiomyocyte dimensions were unaltered, total surface area was increased. This resulted from increased T-tubule density, as revealed by confocal images. Fourier analysis indicated a maintained organization of transverse T-tubules but an increased presence of longitudinal T-tubules. This demonstrates a remarkable plasticity of the tubular system in the adult myocardium. Immunocytochemical data showed that the newly grown longitudinal T-tubules contained Na
+
/Ca
2+
-exchanger proximal to ryanodine receptors in the SR but did not contain Ca
2+
-channels. Ca
2+
measurements demonstrated a switch from SR-driven to Ca
2+
influx-driven Ca
2+
transients in KO. Still, SR Ca
2+
release constituted 20% of the Ca
2+
transient in KO. Mathematical modeling suggested that Ca
2+
influx via Na
+
/Ca
2+
-exchange in longitudinal T-tubules triggers release from apposing ryanodine receptors in KO, partially compensating for reduced SERCA by allowing for local Ca
2+
release near the myofilaments. T-tubule proliferation occurs without loss of the original ordered transverse orientation and thus constitutes the basis for compensation of the declining SR function without structural disarrangement.
Extensive morphological divergence and rapid evolution of the larval neuromuscular junction in
Drosophila
Authors: Campbell Megan , Ganetzky Barry
Published: February 2012

Although the complexity and circuitry of nervous systems undergo evolutionary change, we lack understanding of the general principles and specific mechanisms through which it occurs. The
Drosophila
larval neuromuscular junction (NMJ), which has been widely used for studies of synaptic development and function, is also an excellent system for studies of synaptic evolution because the genus spans >40 Myr of evolution and the same identified synapse can be examined across the entire phylogeny. We have now characterized morphology of the NMJ on muscle 4 (NMJ4) in >20 species of
Drosophila
. Although there is little variation within a species, NMJ morphology and complexity vary extensively between species. We find no significant correlation between NMJ phenotypes and phylogeny for the species examined, suggesting that drift alone cannot explain the phenotypic variation and that selection likely plays an important role. However, the nature of the selective pressure is still unclear because basic parameters of synaptic function remain uniform. Whatever the mechanism, NMJ morphology is evolving rapidly in comparison with other morphological features because NMJ phenotypes differ even between several sibling species pairs. The discovery of this unexpectedly extensive divergence in NMJ morphology among
Drosophila
species provides unique opportunities to investigate mechanisms that regulate synaptic growth; the interrelationships between synaptic morphology, neural function, and behavior; and the evolution of nervous systems and behavior in natural populations.
Theoretical triangulation as an approach for revealing the complexity of a classroom discussion
Authors: van Drie Jannet , Dekker Rijkje
Published: February 2012

In this paper we explore the value of theoretical triangulation as a methodological approach for the analysis of classroom interaction. We analyze an excerpt of a whole‐class discussion in history from three theoretical perspectives: interactivity of the discourse, conceptual level raising and historical reasoning. We conclude that using theoretical triangulation enables us to relate the perspectives of the teacher, the students and the domain to each other, which provides us with deeper insight into the complex phenomenon of classroom interaction. The analyses reveal the complexities the teacher faces when trying to elicit and promote collaborative knowledge construction and the dilemma of promoting student participation, on the one hand, and deepening the quality of reasoning, on the other.
Langevin dynamics with constraints and computation of free energy differences
Authors: Lelièvre Tony , Rousset Mathias , Stoltz Gabriel
Published: February 2012

In this paper, we consider Langevin processes with mechanical constraints. The latter are a fundamental tool in molecular dynamics simulation for sampling purposes and for the computation of free energy differences. The results of this paper can be divided into three parts. (i) We propose a simple discretization of the constrained Langevin process based on a splitting strategy. We show how to correct the scheme so that it samplesexactlythe canonical measure restricted on a submanifold, using a Metropolis-Hastings correction in the spirit of the Generalized Hybrid Monte Carlo (GHMC) algorithm. Moreover, we obtain, in some limiting regime, a consistent discretization of the overdamped Langevin (Brownian) dynamics on a submanifold, also sampling exactly the correct canonical measure with constraints. (ii) For free energy computation using thermodynamic integration, we rigorously prove that the longtime average of the Lagrange multipliers of the constrained Langevin dynamics yields the gradient of a rigid version of the free energy associated with the constraints. A second order time discretization using the Lagrange multipliers is proposed. (iii) The Jarzynski-Crooks fluctuation relation is proved for Langevin processes with mechanical constraints evolving in time. An original numerical discretization without time discretization error is proposed, and its overdamped limit is studied. Numerical illustrations are provided for (ii) and (iii).
An integrated strategy for prediction uncertainty analysis
Authors: Vanlier J. , Tiemann C.A. , Hilbers P.A.J. , van Riel N.A.W.
Published: February 2012

Motivation: To further our understanding of the mechanisms underlying biochemical pathways mathematical modelling is used. Since many parameter values are unknown they need to be estimated using experimental observations. The complexity of models necessary to describe biological pathways in combination with the limited amount of quantitative data results in large parameter uncertainty which propagates into model predictions. Therefore prediction uncertainty analysis is an important topic that needs to be addressed in Systems Biology modelling.

Results: We propose a strategy for model prediction uncertainty analysis by integrating profile likelihood analysis with Bayesian estimation. Our method is illustrated with an application to a model of the JAK-STAT signalling pathway. The analysis identified predictions on unobserved variables that could be made with a high level of confidence, despite that some parameters were non-identifiable.

Availability and implementation: Source code is available at: http://bmi.bmt.tue.nl/sysbio/software/pua.html.

Contact:  j.vanlier@tue.nl

Supplementary information:  Supplementary data are available at Bioinformatics online.
Clinical course and predictive value of liver function tests in patients hospitalized for worsening heart failure with reduced ejection fraction: an analysis of the EVEREST trial
Authors: Ambrosy Andrew P. , Vaduganathan Muthiah , Huffman Mark D. , Khan Sadiya , Kwasny Mary J. , Fought Angela J. , Maggioni Aldo P. , Swedberg Karl , Konstam Marvin A. , Zannad Faiez , Gheorghiade Mihai ,   on behalf of the EVEREST trial investigators
Published: February 2012

Aims

Abnormal liver function tests (LFTs) are common in ambulatory heart failure (HF). The aim of this study was to characterize abnormal LFTs during index hospitalization.

Methods and results

A post‐hoc analysis was carried out of the placebo group of the EVEREST (Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study with Tolvaptan) trial, which enrolled patients hospitalized for HF with an ejection fraction (EF) ≤40% and no history of primary significant liver disease or acute hepatic failure. LFTs (abbreviation, cut‐offs for abnormal values) including serum albumin (ALB, <3.3 g/dL), aspartate transaminase (AST, >34 IU/L), alanine transaminase (ALT, >34 IU/L), alkaline phosphatase (AP, >123 IU/L),γ‐glutamyl transferase (GGT, >50 IU/L), and total bilirubin (T Bili, >1.2 mg/dL) were measured at baseline, discharge/day 7, and post‐discharge. Co‐primary endpoints were all‐cause mortality (ACM) and cardiovascular mortality or first HF hospitalization (CVM + HFH). Study participants had a mean age of 65.6 ±12.0 years, were mostly male, reported high prevalences of medical co‐morbidities, and were well treated with evidence‐based therapies. Baseline LFT abnormalities were common (ALB 17%, AST 21%, ALT 21%, AP 23%, GGT 62%, and T Bili 26%). Abnormal T Bili was the only marker to decrease substantially from baseline (26%) to discharge/day 7 (19%). All LFTs, except AP, improved post‐discharge. Lower baseline ALB and elevated T Bili were associated with higher rates of ACM, and in‐hospital decreases in ALB and increases in T Bili were associated with higher rates of both ACM and CVM + HFH.

Conclusion

LFT abnormalities are common during hospitalization for HF in patients with reduced EF and were persistent at discharge. Baseline and in‐hospital changes in ALB and T Bili provide additional prognostic value.
Wing vein patterns of the Hemiptera insectOrosanga japonicusdiffer among individuals
Authors: Yoshimoto Eiichi , Kondo Shigeru
Published: February 2012

Although Turing's reaction–diffusion model (RD model) has been gradually accepted among biologists, application of the model is still limited. Accumulated experimental studies have shown that the morphogen gradient model can explain most patterning phenomena in embryogenesis. These experiments have been performed only in a few model animals. Therefore, it is not clear whether the discovered principle of the mechanism is generally applicable. The wing venation pattern ofDrosophila melanogasteris largely determined by the morphogen gradient mechanism. We found that the gradient model cannot be applied to some other species. In the Hemiptera insectOrosanga japonicus, each individual has a unique pattern. Veins ofO. japonicusextend radially from the proximal region and bifurcate to add the veins in the distal region. Interestingly, the bifurcation points are almost random and the vein number at the wing edge differs with wing size. However, the spacing between the veins is maintained evenly. Computer simulation of the RD model showed these properties do not fit the morphogen gradient model, but perfectly fit the RD model. This result suggests that the RD model may explain phenomena to which the morphogen gradient mechanism is currently believed to apply.
A homogenization method for thermomechanical continua using extensive physical quantities
Authors: Mandadapu Kranthi K. , Sengupta Arkaprabha , Papadopoulos Panayiotis
Published: February 2012

This article proposes a continuum thermomechanical homogenization method inspired by the Irving–Kirkwood procedure relating the atomistic equations of motion to the balance laws of continuum mechanics. This method yields expressions for the macroscopic stress and heat flux in terms of microscopic kinematic and kinetic quantities. The resulting equation for macroscopic stress affords a rational comparison with the widely used Hill–Mandel stress-deformation condition, while the one for heat flux reduces, under certain assumptions, to a Hill–Mandel-like condition involving heat flux and the gradient of temperature.
PKA increases in the olfactory bulb act as unconditioned stimuli and provide evidence for parallel memory systems: Pairing odor with increased PKA creates intermediate- and long-term, but not short-term, memories
Authors: Grimes Matthew T. , Harley Carolyn W. , Darby-King Andrea , McLean John H.
Published: February 2012

Neonatal odor-preference memory in rat pups is a well-defined associative mammalian memory model dependent on cAMP. Previous work from this laboratory demonstrates three phases of neonatal odor-preference memory: short-term (translation-independent), intermediate-term (translation-dependent), and long-term (transcription- and translation-dependent). Here, we use neonatal odor-preference learning to explore the role of olfactory bulb PKA in these three phases of mammalian memory. PKA activity increased normally in learning animals 10 min after a single training trial. Inhibition of PKA by Rp-cAMPs blocked intermediate-term and long-term memory, with no effect on short-term memory. PKA inhibition also prevented learning-associated CREB phosphorylation, a transcription factor implicated in long-term memory. When long-term memory was rescued through increased β-adrenoceptor activation, CREB phosphorylation was restored. Intermediate-term and long-term, but not short-term odor-preference memories were generated by pairing odor with direct PKA activation using intrabulbar Sp-cAMPs, which bypasses β-adrenoceptor activation. Higher levels of Sp-cAMPs enhanced memory by extending normal 24-h retention to 48–72 h. These results suggest that increased bulbar PKA is necessary and sufficient for the induction of intermediate-term and long-term odor-preference memory, and suggest that PKA activation levels also modulate memory duration. However, short-term memory appears to use molecular mechanisms other than the PKA/CREB pathway. These mechanisms, which are also recruited by β-adrenoceptor activation, must operate in parallel with PKA activation.
Brassinosteroids Antagonize Gibberellin- and Salicylate-Mediated Root Immunity in Rice
Authors: De Vleesschauwer David , Van Buyten Evelien , Satoh Kouji , Balidion Johny , Mauleon Ramil , Choi Il-Ryong , Vera-Cruz Casiana , Kikuchi Shoshi , Höfte Monica
Published: February 2012

Brassinosteroids (BRs) are a unique class of plant steroid hormones that orchestrate myriad growth and developmental processes. Although BRs have long been known to protect plants from a suite of biotic and abiotic stresses, our understanding of the underlying molecular mechanisms is still rudimentary. Aiming to further decipher the molecular logic of BR-modulated immunity, we have examined the dynamics and impact of BRs during infection of rice (Oryza sativa) with the root oomycete Pythium graminicola. Challenging the prevailing view that BRs positively regulate plant innate immunity, we show that P. graminicola exploits BRs as virulence factors and hijacks the rice BR machinery to inflict disease. Moreover, we demonstrate that this immune-suppressive effect of BRs is due, at least in part, to negative cross talk with salicylic acid (SA) and gibberellic acid (GA) pathways. BR-mediated suppression of SA defenses occurred downstream of SA biosynthesis, but upstream of the master defense regulators NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 and OsWRKY45. In contrast, BR alleviated GA-directed immune responses by interfering at multiple levels with GA metabolism, resulting in indirect stabilization of the DELLA protein and central GA repressor SLENDER RICE1 (SLR1). Collectively, these data favor a model whereby P. graminicola coopts the plant BR pathway as a decoy to antagonize effectual SA- and GA-mediated defenses. Our results highlight the importance of BRs in modulating plant immunity and uncover pathogen-mediated manipulation of plant steroid homeostasis as a core virulence strategy.
Combination of low free testosterone and low vitamin D predicts mortality in older men referred for coronary angiography
Authors: Lerchbaum Elisabeth , Pilz Stefan , Boehm Bernhard O. , Grammer Tanja B. , Obermayer‐Pietsch Barbara , März Winfried
Published: February 2012

Context

Low levels of 25‐hydroxyvitamin D [25(OH)D] and free testosterone (FT) are both associated with increased mortality. Experimental studies show a complex interplay of vitamin D and androgen metabolism suggesting that a deficiency of both hormones may be associated with a particularly adverse clinical outcome.

Objective

To evaluate the impact of parallel FT and 25(OH)D deficiency in a large cohort of older men.

Design

We measured total testosterone (TT), sex hormone‐binding globulin and 25(OH)D levels in 2069 men who were routinely referred for coronary angiography (1997–2000).

Main outcome measures

Cox proportional hazard ratios (HRs) (with 95% confidence intervals) for mortality from all causes, cardiovascular and noncardiovascular causes according to combined deficiency of FT and 25(OH)D.

Results

In multivariate‐adjusted analyses, we found an increased risk for all‐cause mortality, cardiovascular and noncardiovascular mortality for men in the lowest FT [HR 1·26 (1·03–1·54), 1·24 (0·96–1·60) and 1·39 (1·00–1·93), respectively] and 25(OH)D quartile [HR 1·77 (1·47–2·13), 1·65 (1·29–2·10) and 1·89 (1·38–2·60) respectively] compared with men in higher FT and 25(OH)D quartiles. There was no independent association of TT levels with mortality. Multivariate‐adjusted HRs progressively increased with the number of hormones (FT and 25(OH)D) in the lowest quartile [0 vs 2 hormone deficiencies: 2·11 (1·60–2·79) for all cause, 1·77 (1·23–2·55) for cardiovascular and 2·33 (1·45–3·47) for noncardiovascular mortality, respectively].

Conclusion

A combined deficiency of FT and 25(OH)D is significantly associated with fatal events in a large cohort of men referred for coronary angiography.
The 312N variant of the luteinizing hormone/choriogonadotropin receptor gene (LHCGR) confers up to 2·7‐fold increased risk of polycystic ovary syndrome in a Sardinian population
Authors: Capalbo A. , Sagnella F. , Apa R. , Fulghesu A. M. , Lanzone A. , Morciano A. , Farcomeni A. , Gangale M. F. , Moro F. , Martinez D. , Ciardulli A. , Palla C. , Uras M. L. , Spettu F. , Cappai A. , Carcassi C. , Neri G. , Tiziano F. D.
Published: February 2012

Objective

Polycystic ovary syndrome (PCOS) is a frequent condition, affecting about 15% of women of reproductive age. Because of its familial occurrence, a multifactorial model of susceptibility, including both genetic and environmental factors, has been proposed. However, the identification of genetic factors has been elusive.

Design

Case–control study aimed at evaluating possible associations between functionally relevant variants of the luteinizing hormone/choriogonadotrophin receptor gene (LHCGR) and PCOS phenotype.

Patients

A total of 198 PCOS and 187 non‐PCOS women, aged 14–35 years, of Sardinian origin, were referred to the outpatient clinic of the Department of Obstetrics and Gynaecology of the University of Cagliari (Sardinia). PCOS diagnosis was based on the Rotterdam criteria.

Measurements

We determined the genotype of ins18LQ, S291N and S312N variants at the LHCGR locus. Genotype was related to the presence or absence of PCOS and to several clinical and biochemical characteristics.

Results

The presence of at least one 312N allele was strongly associated with PCOS risk (OR, 2·04; 95% CI, 1·32–3·14; χ2, 10·47; P = 0·001). 312N homozygosity was associated with a further risk increase (OR, 2·73; 95% CI, 1·25–5·95; χ2, 6·65; P = 0·01). The number of ins18LQ alleles was associated with LH serum levels in controls (χ2, 8·04, P = 0·017).

Conclusions

For the first time, we have identified a genetic variant that is strongly associated with PCOS in an isolated population. These results, if confirmed in other cohorts, may provide the opportunity to test the S312N genotype at the LHCGR locus in fertile women to assess the risk of PCOS. The avoidance of triggering factors like weight increase may improve the reproductive outcome of potentially at‐risk subjects.
Haemostatic management of extreme challenges to haemostasis in acquired von Willebrand syndrome
Authors: COLELLA M. P. , DUARTE G. C. , MARQUES J. F. C. , DE PAULA E. V.
Published: February 2012

Summary.  Acquired von Willebrand syndrome (AVWS) is a rare hemorrhagic condition for which very little information is available regarding the management of extreme challenges to Haemostasis. The AVWS is more common in the elderly, who are frequently exposed to invasive procedures and/or chemotherapy. Haematopoietic stem cell transplantation (HSCT) is a situation in which the haemostatic capacity is challenged by severe thrombocytopaenia, chemotherapy‐associated mucosal barrier breakdown and the need for invasive procedures. In our report, we present and discuss the haemostatic management of a patient with AVWS who was refractory to Von Willebrand factor concentrate replacement during the course of an autologous HSCT to treat multiple myeloma. Patients with AVWS are frequently exposed to high‐risk haemostatic challenges, and additional information about the haemostatic management of these situations is necessary.
Can online course‐based assessment methods be fair and equitable? Relationships between students' preferences and performance within online and offline assessments
Authors: Hewson C.
Published: February 2012

To address concerns raised regarding the use of online course‐based summative assessment methods, a quasi‐experimental design was implemented in which students who completed a summative assessment either online or offline were compared on performance scores when using their self‐reported preferred or non‐preferred modes. Performance scores were found not to differ depending on whether the assessment was completed in the preferred or non‐preferred mode. These findings provide preliminary support for the validity of online assessment methods. Future studies could help determine the extent to which this finding generalizes beyond the assessment procedures and type of sample used here. Suggestions for follow‐up studies are offered, including exploring the validity of more complex computer‐related online assessment tasks and investigating the impact of using preferred and non‐preferred modes upon the quality of the student experience.
Detecting breakdowns in local coherence in the writing of Chinese English learners
Authors: Wang Y. , Harrington M. , White P.
Published: February 2012

This paper introduces CTutor, an automated writing evaluation (AWE) tool for detecting breakdowns in local coherence and reports on a study that applies it to the writing of Chinese L2 English learners. The program is based on Centering theory (CT), a theory of local coherence and salience. The principles of CT are first introduced and then the design and function of CTutor are described. The effectiveness and reliability of the program was evaluated in a study that compared performance by CTutor and two human raters on the analysis of local incoherence and provision of revision on learner essays. Intermediate Chinese English as a foreign language learners (n = 52) were divided into two groups: one receiving CTutor feedback and the other receiving feedback from human raters. Learners in both groups completed three essays; each of which involved the submission of a first draft, revision with feedback on local coherence quality and re‐submission. Our results from the comparison between CTutor and human experts showed that this software tool is able to detect local coherence breakdowns with moderate accuracy (F1‐measure is around 0.4). There was also little difference between participants' responses to CTutor feedback and human feedback in terms of revision behaviour, with both feedback modes resulting in similar revision pattern. Potential use of the program in instructional settings is discussed.
Familial Breast Cancer
Authors: Lalloo F , Evans D G
Published: February 2012

Since the localization and discovery of the first high‐risk breast cancer (BC) genes in 1990, there has been a substantial progress in unravelling its familial component. Increasing numbers of women at risk of BC are coming forward requesting advice on their risk and what they can do about it. Three groups of genetic predisposition alleles have so far been identified with high‐risk genes conferring 40–85% lifetime risk including BRCA1, BRCA2 and TP53. Moderate risk genes (20–40% risk) including PALB1, BRIP, ATM and CHEK2, and a host of low‐risk common alleles identified largely through genome‐wide association studies. Currently, only BRCA1, BRCA2 and TP53 are used in clinical practice on a wide scale, although testing of up to 50–100 gene loci may be possible in the future utilizing next‐generation technology.
Reproduction‐longevity trade‐offs reflect diet, not adaptation
Authors: ATTISANO A. , MOORE A. J. , MOORE P. J.
Published: February 2012

A tenet of life history evolution is that allocation of limited resources results in trade‐offs, such as that between reproduction and lifespan. Reproduction and lifespan are also influenced proximately by differences in the availability of specific nutrients. What is unknown is how the evolution of the ability to use a nutritionally novel diet is reflected in this fundamental trade‐off. Does the evolution of the ability to use a nutritionally novel food maintain the trade‐off in reproduction and longevity, or do the proximate effects of nutrition alter the adapted trade‐off? We tested this by measuring trade‐offs in male milkweed bugs, Oncopeltus fasciatus, fed either an adapted diet of sunflower or the ancestral diet of milkweed. Sunflower‐fed males lived longer but invested less in reproduction, both in mating and fertility. Milkweed‐fed males invested in both mating and fertility at the expense of survival. The evolution of an expanded diet was not constrained by the existing trade‐off, but instead was accompanied by a different trade‐off between reproduction and longevity. We suggest that this occurs because diets differ in promoting germ line development or longevity.
Gene silencing in adult Aedes aegypti mosquitoes through oral delivery of double‐stranded RNA
Authors: Coy M. R. , Sanscrainte N. D. , Chalaire K. C. , Inberg A. , Maayan I. , Glick E. , Paldi N. , Becnel J. J.
Published: February 2012

The induction of the naturally occurring phenomenon of RNA interference (RNAi) to study gene function in insects is now common practice. With appropriately chosen targets, the RNAi pathway has also been exploited for insect control, typically through oral delivery of dsRNA. Adapting current methods to deliver foreign compounds, such as amino acids and pesticides, to mosquitoes through sucrose solutions, we tested whether such an approach could be used in the yellow fever mosquito, Aedes aegypti. Using a non‐specific dsRNA construct, we found that adult Ae. aegypti ingested dsRNA through this method and that the ingested dsRNA can be recovered from the mosquitoes post‐feeding. Through the feeding of a species‐specific dsRNA construct against vacuolar ATPase, subunit A, we found that significant gene knockdown could be achieved at 12, 24 and 48 h post‐feeding.