bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact inductorless CMOS low‐noise amplifier for reconfigurable radio
Authors: Slimane Abdelhalim , Haddad Fayrouz , Bourdel Sylvain , Tedjini‐Baïliche Sid Ahmed , Belaroussi Mohand Tahar , Mohamed Trabelsi , Barthélemy Hervé
Published: May 2014

A compact reconfigurable CMOS low‐noise amplifier (LNA) is presented for applications in DCS1800, UMTS, WLAN‐b/g and Bluetooth standards. The proposed LNA features first a current reuse shunt‐feedback amplifier for wideband input matching, low‐noise figure and small area. Secondly, a cascode amplifier with a tunable active LC resonator is added for high gain and continuous tuning of bands. Fabricated in a 0.13 μm CMOS process, the measured results show >20 dB power gain, <3.5 dB noise figure in the frequency range of 1.8–2.4 GHz, return losses S11 and S22 lower than −12 and −14 dB, respectively, with a moderate IIP3 of −11.8 dBm at 2.4 GHz. It consumes 9.6 mW from a 1.2 V supply voltage, while occupying an active silicon area of only 0.052 mm2.
Simply decoded efficient full‐rate space–time block codes over correlated Rician fading channels
Authors: Kuhestani Ali , PilAram Hossein , Mohammadi Abbas
Published: May 2014

A novel technique is presented to design efficient full‐rate space–time block codes (STBCs) over correlated Rician fading channels. The authors first derive a formula for the achievable information rate of a linear dispersion coded multi‐input single‐output system as a function of correlation at the transmitter in a Rician fading channel. In addition, the authors obtain the bit‐error‐rate (BER) equations for this system, when multiple phase shift keying and multiple quadrature amplitude modulation schemes are used at the transmitter. Therefore with regard to derived formulae and using a genetic algorithm, a method is presented to construct STBCs over correlated Rician fading channels. The efficient designed STBCs for two and four transmit antennas enjoy full‐rate, simple structure, simple processing at the receiver, better BER performance than associated orthogonal STBCs at practical signal‐to‐noise ratios (SNRs) and higher achievable information rate than them at all SNRs.
Linear parameter‐varying‐based fault‐tolerant controller design for a class of over‐actuated non‐linear systems with applications to electric vehicles
Authors: Wang Rongrong , Zhang Hui , Wang Junmin
Published: May 2014

This study presents a passive fault‐tolerant (FT) controller to preserve stability of a class of over‐actuated non‐linear systems in spite of actuator faults. In order to deal with different types of actuator faults, a generalised fault model is adopted such that the FT controller may have the advantage of being able to deal with different types of actuator faults. By grouping the control efforts which have similar effects on the system together, the original over‐actuated system can be transferred into a square system, which makes the proposed FT controller has no requirement of the control effort distribution ratios for the actual control effects. The disturbances and uncertainties caused by the actuator faults are attenuated by an FT controller which is designed based on the linear‐parameter varying method. The eigenvalue positions of the closed‐loop system are constrained into a disk to obtain better transient responses. The proposed FT control method is applied to control a four wheel independently‐actuated electric ground vehicle. Experimental results show the effectiveness of the proposed FT control approach.
L2 – L∞ containment control of multi‐agent systems with Markovian switching topologies and non‐uniform time‐varying delays
Authors: Mu Xiaowu , Zheng Baojie , Liu Kai
Published: May 2014

In this study, the authors investigate L2  − L∞ containment control problem of multi‐agent systems with multiple stationary leaders and external disturbances. Furthermore, the interaction topology is Markovian switching and non‐uniform time‐varying delays are considered. By using a model transformation, the containment control problem of the multi‐agent systems is turned into a normal L2  − L∞ control problem. Based on the theory in stochastic stability for time‐delays systems, sufficient conditions in terms of a set of linear matrix inequalities are given to ensure that all the followers will move into the convex hull formed by the leaders in mean square sense with a prescribed L2  − L∞ performance. Two numerical simulations are provided to show the effectiveness of theoretical results.
Non‐destructive automatic leaf area measurements by combining stereo and time‐of‐flight images
Authors: Song Yu , Glasbey Chris A. , Polder Gerrit , van der Heijden Gerie W.A.M.
Published: May 2014

Leaf area measurements are commonly obtained by destructive and laborious practice. This study shows how stereo and time‐of‐flight (ToF) images can be combined for non‐destructive automatic leaf area measurements. The authors focus on some challenging plant images captured in a greenhouse environment, and show that even the state‐of‐the‐art stereo methods produce unsatisfactory results. By transforming depth information in a ToF image to a localised search range for dense stereo, a global optimisation strategy is adopted for producing smooth results that preserve discontinuity. They also use edges of colour and disparity images for automatic leaf detection and develop a smoothing method necessary for accurately estimating surface area. In addition to show that combining stereo and ToF images gives superior qualitative and quantitative results, 149 automatic measurements on leaf area using the authors system in a validation trial have a correlation of 0.97 with true values and the root‐mean‐square error is 10.97 cm2, which is 9.3% of the average leaf area. Their approach could potentially be applied for combining other modalities of images with large difference in image resolutions and camera positions.
Bhattacharyya distance‐based irregular pyramid method for image segmentation
Authors: Yu Yuanlong , Gu Jason , Wang Junzheng
Published: May 2014

This paper proposes a new unsupervised image segmentation method by using Bhattacharyya distance‐based irregular pyramid, termed as ‘BDIP’ algorithm. The proposed BDIP algorithm obtains a suboptimal labelling solution under the condition that the number of segments is not manually given. It hierarchically builds each level of the irregular pyramid, with the result that the final segments emerge as they are represented by single nodes at certain levels. The BDIP algorithm employs Bhattacharyya distance to estimate the intra‐level similarity at higher pyramidal levels so as to improve the accuracy and robustness to noise. Furthermore, an adaptive neighbour search method is proposed such that the BDIP algorithm can self‐determine the number of segments. This method considers not only the graphic constraint, but also the similarity constraint in the sense that a candidate node is selected as a neighbour of the centre node if there is no boundary evidence between these two nodes. With the pyramidal accumulation, this evaluation is aggregated into the approximately global evidence, based on which the number of segments can be self‐determined. Experimental results have shown that this proposed BDIP algorithm outperforms other benchmark segmentation algorithms in terms of segmentation accuracy, labelling cost and robustness to noise.
Coil-bridge transition in a single polymer chain as an unconventional phase transition: Theory and simulation
Authors: Klushin Leonid I. , Skvortsov Alexander M. , Polotsky Alexey A. , Hsu Hsiao-Ping , Binder Kurt
Published: May 2014

The coil-bridge transition in a self-avoiding lattice chain with one end fixed at height H above the attractive planar surface is investigated by theory and Monte Carlo simulation. We focus on the details of the first-order phase transition between the coil state at large height H ⩾ Htr and a bridge state at H ⩽ Htr, where Htr corresponds to the coil-bridge transition point. The equilibrium properties of the chain were calculated using the Monte Carlo pruned-enriched Rosenbluth method in the moderate adsorption regime at (H/Na)tr ⩽ 0.27 where N is the number of monomer units of linear size a. An analytical theory of the coil-bridge transition for lattice chains with excluded volume interactions is presented in this regime. The theory provides an excellent quantitative description of numerical results at all heights, 10 ⩽ H/a ⩽ 320 and all chain lengths 40 < N < 2560 without free fitting parameters. A simple theory taking into account the effect of finite extensibility of the lattice chain in the strong adsorption regime at (H/Na)tr ⩾ 0.5 is presented. We discuss some unconventional properties of the coil-bridge transition: the absence of phase coexistence, two micro-phases involved in the bridge state, and abnormal behavior in the microcanonical ensemble.
Equivalent perfect magnetic conductor based on epsilon-near-zero media
Authors: Wang Tingting , Luo Jie , Gao Lei , Xu Ping , Lai Yun
Published: May 2014

We propose a kind of equivalent perfect magnetic conductor (EPMC) based on epsilon-near-zero media containing the dielectric defects. It is found that such an EPMC can be arbitrarily shaped and works for all incident angles for transverse magnetic waves. When resonances occur inside the dielectric defects with nodes of magnetic fields located at the boundaries of defects, the epsilon-near-zero media can enforce such near zero magnetic fields to the outer boundaries, making the whole system work as an EPMC. Through inspecting the scatterings, blocking effects and applications of perfect absorption, we verify the good performance of the EPMC even when large losses are taken into account. Our study provides flexible ways to mitigate the realizations of EPMC from the microwave regime to the infrared/visible one.
On the collective network of ionic liquid/water mixtures. IV. Kinetic and rotational depolarization
Authors: Schröder Christian , Sega Marcello , Schmollngruber Michael , Gailberger Elias , Braun Daniel , Steinhauser Othmar
Published: May 2014

Dielectric spectroscopy is a measure of the collective Coulomb interaction in liquid systems. Adding ionic liquids to an aqueous solution results in a decrease of the static value of the generalized dielectric constant which cannot be attributed to kinetic depolarization models characterized by the static conductivity and rotational relaxation constant. However, a dipolar Poisson-Boltzmann model computing the water depolarization in the proximity of ions is not only successful for simple electrolytes but also in case of molecular ionic liquids. Moreover, our simple geometric hydration model is also capable to explain the dielectric depolarization. Both models compute the dielectric constant of water and obtain the overall dielectric constant by averaging the values of its components, water and the ionic liquid, weighted by their volume occupancies. In this sense, aqueous ionic liquid mixtures seem to behave like polar mixtures.
Model free isoconversional procedure for evaluating the effective activation energy values of thermally stimulated processes in dinitroimidazoles
Authors: Ravi P.
Published: May 2014

The decomposition kinetics of 1,4-dinitroimidazole, 2,4-dinitroimidazole, and N-methyl-2,4-dinitroimidazole have been investigated using thermogravimetry–differential thermal analysis technique under N2 atmosphere at the flow rate 100 cm3/min. The Flynn-Wall-Ozawa method and the Friedman method were used for the estimation of the effective activation energy values. These model free isoconversional kinetic methods showed variation in the calculated values due to the approximation of temperature integral used in the derivations of the kinetic equations. The model compounds were decomposed by multi-step kinetics evident from the nonlinear relationship of the effective activation energy values with the conversion rate. Three different reaction pathways namely NO2 elimination, NO elimination, and HONO elimination are expected to play crucial role in the decomposition of nitroimidazoles. The model dinitroimidazoles represent different decomposition kinetics, and the reaction pathways the NO2 elimination, and NO elimination compete with each other for the decomposition mechanism. The present study is certainly helpful in understanding the decomposition kinetics, and dynamics of substituted nitroimidazoles to be used for fuel, and explosive applications.
The effect of a magnetic field on the spin-selective transport in double-stranded DNA
Authors: Simchi Hamidreza , Esmaeilzadeh Mahdi , Mazidabadi Hossein
Published: May 2014

Spin-polarization in double-stranded DNA is studied in the presence of a magnetic field applied along its helix axis using the non-equilibrium Green's function method. The spin-polarization could be tuned by changing the magnetic field. In some special cases, the double-stranded DNA behaved as a perfect spin-filter. Furthermore, the dependency of the spin-polarization on the spin-orbit strength and dephasing strength is studied.
Residual stress and interface effect on dielectric mechanisms in poled ultrathin relaxor ferroelectric single crystals
Authors: Li Long , Zhao Xiangyong , Li Xiaobing , Xu Qing , Yang Linrong , Wang Sheng , Luo Haosu
Published: May 2014

We have investigated the dielectric performances and mechanism of super-thin Mn-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals, exhibiting significantly different dielectric behaviors compared with thick wafer. Dramatic decrease by 5 times and large frequency dispersion of permittivity, changed diffuse degree of phase transition, dielectric loss anomaly with frequency and dielectric performances with direct-current electric field for thin wafers are observed, proving the existence of large surface residual stress and interface effects. Additionally, a theoretical model of low-permittivity and low-ferroelectric surface damage layers is concurrently proposed. These observations have important implications for actual performances of thin wafers applied in practical devices.
Energy deficit of pulsed-laser field-ionized and field-emitted ions from non-metallic nano-tips
Authors: Arnoldi L. , Silaeva E. P. , Gaillard A. , Vurpillot F. , Blum I. , Rigutti L. , Deconihout B. , Vella A.
Published: May 2014

The energy deficit of pulsed-laser field-evaporated ions and field-ionized atoms of an inert gas from the surface of a non-metallic nano-metric tip is reported as a function of the laser intensity, ion current, and temperature. A new model is proposed to explain these results, taking into account the resistive properties of non-metallic nano-tips. A good agreement between the theoretical predictions and the experimental results is obtained for all parameters investigated experimentally. This model is also used to discuss the evaporation behavior of oxides analyzed in laser-assisted atom probe tomography. New insight into the contribution of the electrostatic field and the laser illumination on the evaporation process of non-metallic materials is given.
Current induced abnormal electroresistance effect observed in epitaxial La0.9Hf0.1MnO3 thin films
Authors: Xing Jie , Gao Ju , Wang Le
Published: May 2014

La0.9Hf0.1MnO3 thin films with thickness 100 nm were prepared by using a pulsed laser deposition technique. Transport behaviors were investigated under various applied currents without an applied magnetic field. When the applied current is not too large, the peak value of the resistance gradually decreases with increasing current, demonstrating a normal electroresistance (ER) effect. However, when the current reaches a critical value, a high-resistance state appears at a lower temperature below the Curie temperature. And the appeared resistance peak at low temperature turns out to be extremely sensitive to a weak current. Even a very small current could greatly depress the height of the peak, an abnormal ER effect appears. Maximum resistance ratio ER, defined as [R(1 μA)-R(100 μA)]/R(100 μA), is about 1257% at 50 K. Physics related to the appearance of the novel state and the abnormal ER effect is discussed.
Phase control of light propagation via Fano interference in asymmetric double quantum wells
Authors: Yang Wen-Xing , Lu Jia-Wei , Zhou Zhi-Kang , Yang Long , Lee Ray-Kuang
Published: May 2014

We investigate the light propagation and dynamical control of a weak pulsed probe field in asymmetric double quantum wells via Fano interference, which is caused by tunneling from the excited subbands to the same continuum. Our results show that the system can produce anomalous and normal dispersion regions with negligible absorption by choosing appropriate coupling strength of the tunneling and the Fano interference. Interesting enough, the dispersion can be switched between normal and anomalous by adjusting the relative phase between the pulsed probe and coherent control fields owing to the existence of the perfectly Fano interference. Thus, the relative phase can be regarded as a switch to manipulate light propagation with subluminal or superluminal. The temporal and spatial dynamics of the pulsed probe field with hyperbolic secant envelope are analyzed.
Communication: Oscillating charge migration between lone pairs persists without significant interaction with nuclear motion in the glycine and Gly-Gly-NH-CH3 radical cations
Authors: Vacher Morgane , Bearpark Michael J. , Robb Michael A.
Published: May 2014

Coupled electron-nuclear dynamics has been studied, using the Ehrenfest method, for four conformations of the glycine molecule and a single conformation of Gly-Gly-NH-CH3. The initial electronic wavepacket was a superposition of eigenstates corresponding to ionization from the σ lone pairs associated with the carbonyl oxygens and the amine nitrogen. For glycine, oscillating charge migration (when the nuclei were frozen) was observed for the 4 conformers studied with periods ranging from 2 to 5 fs, depending on the energy gap between the lone pair cationic states. When coupled nuclear motion was allowed (which was mainly NH2 partial inversion), the oscillations hardly changed. For Gly-Gly-NH-CH3, charge migration between the carbonyl oxygens and the NH2 lone pair can be observed with a period similar to glycine itself, also without interaction with nuclear motion. These simulations suggest that charge migration between lone pairs can occur independently of the nuclear motion.
Direct detection of spontaneous polarization in wurtzite GaAs nanowires
Authors: Bauer Benedikt , Hubmann Joachim , Lohr Matthias , Reiger Elisabeth , Bougeard Dominique , Zweck Josef
Published: May 2014

We demonstrate the direct detection of spontaneous polarization in the wurtzite crystal phase of gallium-arsenide (GaAs) nanowires. Using differential phase contrast microscopy (DPC) in a scanning transmission electron microscope, we map the differences in charge distribution between the zinc-blende and wurtzite crystal phases and use twin defects in the zinc-blende phase to quantify the polarization strength. The value of 2.7 × 10−3 C/m2 found for the polarization strength matches well with theoretical predictions.
Resistive memory of single SnO2 nanowire based switchable diodes
Authors: Nieh C. H. , Lu M. L. , Weng T. M. , Chen Y. F.
Published: May 2014

Resistive switching is observed in a single SnO2 nanowire device with two back-to-back Schottky diodes. The underlying mechanism can be well interpreted by the switchable diode effect, which is caused by tunable Schottky barrier heights due to the drift of charged defects induced by external electrical field. A resistance window of more than 3 orders of magnitude has been achieved. The device also shows excellent performance in endurance and retention time. Additionally, a very small current under negative bias is observed, which can avoid the sneaking current induced in the nearby devices. Due to the greatly reduced device size, power consumption, and inherent nature of Schottky diode, the work presented here should be useful for the development of high density circuitries.
Photoacoustic phasoscopy super-contrast imaging
Authors: Gao Fei , Feng Xiaohua , Zheng Yuanjin
Published: May 2014

Phasoscopy is a recently proposed concept correlating electromagnetic (EM) absorption and scattering properties based on energy conservation. Phase information can be extracted from EM absorption induced acoustic wave and scattered EM wave for biological tissue characterization. In this paper, an imaging modality, termed photoacoustic phasoscopy imaging (PAPS), is proposed and verified experimentally based on phasoscopy concept with laser illumination. Both endogenous photoacoustic wave and scattered photons are collected simultaneously to extract the phase information. The PAPS images are then reconstructed on vessel-mimicking phantom and ex vivo porcine tissues to show significantly improved contrast than conventional photoacoustic imaging.
Genetic monitoring reveals significant population structure in eastern quolls: implications for the conservation of a threatened carnivorous marsupial
Authors: Cardoso Maria J. , Mooney Nick , Eldridge Mark D. B. , Firestone Karen B. , Sherwin William B.
Published: May 2014

The eastern quoll (Dasyurus viverrinus), while still relatively abundant in Tasmania, is now threatened by the recently introduced European red fox (Vulpes vulpes). Due to a lack of demographic information on eastern quolls, molecular data become a crucial surrogate to inform the management of the species. The aim of this study was to acquire baseline genetic data for use in current and future conservation strategies. Genetic variation, at seven microsatellite loci, was lower in Tasmanian eastern quolls than in quoll species from the Australian mainland. Within Tasmania, genetic variation was greater in central than peripheral populations, with the lowest levels detected on Bruny Island. Significant genetic population structure, consistent with regional differentiation, appears related to geographic distance among populations. Levels of gene flow appeared moderate, with genetic admixture greatest among central populations. Therefore, eastern quolls from genetically diverse central Tasmanian populations will become an important source for conservation initiatives if widespread declines begin to occur. Ongoing genetic monitoring of existing populations will allow conservation strategies to be adaptive. However, in order for translocations to be successful, managers must not only consider the genetic composition of founding individuals, but also habitat-specific adaptations, disease and threatening processes at translocation sites.
Use of Flash Vacuum Thermolysis in a Stereocontrolled Synthesis of Optically Active Alkyl-substituted Cyclopentenones with Fragrant Properties
Authors: Zwanenburg Binne , Volkers Andries A. , Klunder Antonius J. H.
Published: May 2014

The synthesis of four pairs of enantiopure antipodal substituted cyclopentenones is described. The synthetic sequences first comprise the preparation of a tricyclo[5.2.1.02,6]deca-4,8-dienone system, a subsequent kinetic enzymatic resolution of the appropriately functionalized tricyclic system, followed by a series of chemical transformations to install the desired substituents, and finally a retro Diels–Alder reaction using flash vacuum thermolysis to give the target products in high chemical and optical yields. The strategy makes effective use of the concept of transient chirality involving complete stereochemical control over reactions with the chiral tricyclic systems before thermal removal of the cyclopentadiene.
Monthly variations in the profile of sex steroids and gonadal development of brook trout (Salvelinus fontinalis Mitchill) during puberty in Tasmania
Authors: Fatima Shafaq , Adams Mark , Wilkinson Ryan
Published: May 2014

Puberty is an important reproductive event that has not been studied in brook trout in the Southern Hemisphere. The present study describes the histological development of gonads and variations in the levels of oestradiol-17β (E2), testosterone (T) and 11-ketotestosterone (11-KT) during the first year of male and female brook trout. The study started when the trout were at an age of 8 months (n = 10) and continued until they were 15 months. Of the males, 60% attained puberty at an age of 14 months. The peak of the gonadosomatic index in males was observed at 15 months of age (3.0 ± 0.9%). Female fish did not achieve maturation during their first year and ovarian development did not progress beyond the vesicular oocyte stage within the study period.
Global evaluation of biofuel potential from microalgae
Authors: Moody Jeffrey W. , McGinty Christopher M. , Quinn Jason C.
Published: May 2014

Significance

Research into microalgae as a feedstock for biofuels continues to increase because of the inherent potential advantages it holds over traditional terrestrial feedstocks. However, the true near-term large-scale productivity of microalgae remains uncertain. This study integrates a large-scale, outdoor growth model with historical meteorological data from 4,388 global locations to estimate the current near-term lipid and biomass productivity potential from microalgae cultivated in a photobioreactor architecture. Results show that previous life cycle, technoeconomic, and resource assessments dramatically overestimated lipid yields. A scalability assessment that leverages geographic information systems data to evaluate the current productivity potential from microalgae with global fuel consumption and land availability shows that microalgae can have a positive impact on the transportation energy portfolios of various countries.
Up-regulation of glycolytic metabolism is required for HIF1α-driven bone formation
Authors: Regan Jenna N. , Lim Joohyun , Shi Yu , Joeng Kyu Sang , Arbeit Jeffrey M. , Shohet Ralph V. , Long Fanxin
Published: May 2014

Significance

Osteoblast precursors residing in the bone marrow experience hypoxia, which leads to stabilization and increased activity of hypoxia-inducible factor 1α (HIF1α). However, whether an increase in HIF1α activity directly impacts bone formation is not known. Two well-known functions of HIF1α are to promote angiogenesis and to stimulate glycolysis in the cell. Here, we demonstrate that HIF1α stabilization in osteoblast precursors of postnatal mice markedly increases osteoblast number and bone mass. Furthermore, the greater bone mass was not secondary to increased angiogenesis but rather dependent on the up-regulation of glycolysis in osteoblast precursors. These results provide strong evidence that alterations in cellular metabolism directly influence cell differentiation.
Yolk-sac–derived macrophages regulate fetal testis vascularization and morphogenesis
Authors: DeFalco Tony , Bhattacharya Indrashis , Williams Alyna V. , Sams Dustin M. , Capel Blanche
Published: May 2014

Significance

A main requisite for organogenesis is the integration of vascular networks, which not only deliver oxygen and nutrients but also serve instructive roles in organ patterning that determine how organs develop into their final structure and function in the adult. Our previous work showed that vascularization is essential to induce formation of the primitive cord structures that give rise to the seminiferous tubules of the adult testis. Here we show that fetal macrophages are required to remodel the vasculature and refine organ compartments during differentiation of the gonad. This study reveals an underappreciated and likely vital role for macrophages in fetal organogenesis that may be relevant to the development of many organs.
Impact of puberty on the evolution of cerebral perfusion during adolescence
Authors: Satterthwaite Theodore D. , Shinohara Russell T. , Wolf Daniel H. , Hopson Ryan D. , Elliott Mark A. , Vandekar Simon N. , Ruparel Kosha , Calkins Monica E. , Roalf David R. , Gennatas Efstathios D. , Jackson Chad , Erus Guray , Prabhakaran Karthik , Davatzikos Christos , Detre John A. , Hakonarson Hakon , Gur Ruben C. , Gur Raquel E.
Published: May 2014

Significance

Blood perfusion is a fundamental property of brain physiology and is known to be higher in adult females than in males. However, it is unknown when such a sex difference emerges during the lifespan, or what biological processes may cause it. In the largest study of brain perfusion yet reported, we establish for the first time to our knowledge that patterns of development of cerebral perfusion during adolescence are markedly different in males and females, and such differences are attributable in part to the effects of puberty. These results may have important implications for neuropsychiatric disorders with adolescent onset and strong gender disparities, such as mood disorders, anxiety disorders, and schizophrenia.
Highly enantioselective synthesis of γ-, δ-, and ε-chiral 1-alkanols via Zr-catalyzed asymmetric carboalumination of alkenes (ZACA)–Cu- or Pd-catalyzed cross-coupling
Authors: Xu Shiqing , Oda Akimichi , Kamada Hirofumi , Negishi Ei-ichi
Published: May 2014

Significance

Chirality plays a vital role in chemical, biological, pharmaceutical, and material sciences. The preparation of enantiomerically pure compounds is a very important and challenging area. In this paper, we developed a highly enantioselective (≥99%
ee
) and widely applicable method for the synthesis of various γ- and more-remotely chiral alcohols, many of which cannot be satisfactorily prepared by other existing methods, via the ZACA/oxidation–lipase-catalyzed acetylation–Cu- or Pd-catalyzed cross-coupling from terminal alkenes. We also demonstrated MαNP ester analysis is a convenient and powerful method for determining the enantiomeric purities of δ- and ε-chiral primary alkanols. This finding is anticipated to shed light on the relatively undeveloped field of determination of enantiomeric purity and/or absolute configuration of remotely chiral primary alcohols.
Identification of genes preventing transgenerational transmission of stress-induced epigenetic states
Authors: Iwasaki Mayumi , Paszkowski Jerzy
Published: May 2014

Significance

Much attention has been drawn to research, which suggests that environmental factors, including stress and maternal care, alter the way the genetic code is executed. These epigenetic changes in gene regulation are thought to be stable enough to be heritable and thus may influence subsequent generations. Such prospects are as intriguing as they are troubling, since it is possible to imagine that accumulation of stress memories over several generations could make life decisions difficult. Therefore, we have questioned whether mechanisms exist that could prevent the inheritance of stress-induced epigenetic changes and have discovered such mechanisms using forward genetics in
Arabidopsis
. Interestingly, one of the critical activities erasing stress memories is conserved between plants and mammals.
Reassessing the biogenicity of Earth’s oldest trace fossil with implications for biosignatures in the search for early life
Authors: Grosch Eugene G. , McLoughlin Nicola
Published: May 2014

Significance

It has been argued that Archean subseafloor pillow lava sequences provide an environment in which to seek evidence for the earliest traces of life. Candidate titanite biosignatures of microbial activity have been reported in ∼3.45-Ga metavolcanic glass from the Barberton greenstone belt of South Africa. In this paper we present new in situ U–Pb age data, metamorphic constraints, and morphological observations on these titanite microtextures. Our data challenges a biological origin for these oldest purported trace fossils, with implications for the ecological niches where life may have first emerged. We therefore suggest alternative biosignatures and approaches should be considered in the search for subsurface life on early Earth and in extraterrestrial mafic–ultramafic rocks, for example, in martian basalts.
Membrane raft association is a determinant of plasma membrane localization
Authors: Diaz-Rohrer Blanca B. , Levental Kandice R. , Simons Kai , Levental Ilya
Published: May 2014

Significance

The organization of metazoan membranes into functional domains is a key feature of their physiology. A subset of these domains, known as “membrane rafts,” has been implicated in a large variety of cellular processes; however, the molecular mechanisms by which raft domains regulate cell function remain elusive. Here, we demonstrate that membrane raft association is a necessary and sufficient sorting signal for cell-surface localization of a specific single-pass membrane protein, linker for activation of T-cells, and that this raft association is governed by the properties of the protein transmembrane domain. These results begin to define the physical bases for protein raft affinity and establish lateral membrane domains as mediators of protein sorting in mammalian cells.
Cognitive flexibility and long-term depression (LTD) are impaired following β-catenin stabilization in vivo
Authors: Mills Fergil , Bartlett Thomas E. , Dissing-Olesen Lasse , Wisniewska Marta B. , Kuznicki Jacek , Macvicar Brian A. , Wang Yu Tian , Bamji Shernaz X.
Published: May 2014

Significance

Complex learning and memory are believed to require the weakening or elimination of synapses in the brain, a process mediated by adhesion molecules, which maintain synapse strength and stability. In the present study, we examine in vivo the effects of stabilization of β-catenin, an intracellular protein that is a component of the cadherin adhesion complex. We find that stabilization of β-catenin in the brain prevents normal activity-dependent downscaling of synapse strength, resulting in a striking impairment in cognitive flexibility. These results demonstrate that β-catenin plays an important role in learning and memory and that aberrant increases in synaptic adhesion can have detrimental effects on cognitive function.
GABA
A
receptor target of tetramethylenedisulfotetramine
Authors: Zhao Chunqing , Hwang Sung Hee , Buchholz Bruce A. , Carpenter Timothy S. , Lightstone Felice C. , Yang Jun , Hammock Bruce D. , Casida John E.
Published: May 2014

Significance

Tetramethylenedisulfotetramine (TETS) is a feared chemical threat agent because of its high convulsant toxicity, ease of synthesis, and availability even though it is banned as a rodenticide. Earlier physiological evidence indicating action as a GABA receptor antagonist and inhibitor of [
35
S]TBPS and [
3
H]EBOB binding is confirmed here by radiosynthesis of [
14
C]TETS and defining its binding site in rat brain membranes by accelerator mass spectrometry and toxicant specificity studies on inhibition of [
14
C]TETS and [
3
H]EBOB binding. TETS undergoes specific and unique polar interactions inside the 1′2′ ring pore region instead of the 2′,6′, and 9′ site for insecticides. This study helps define GABA
A
R sites for potential antidotes acting to prevent TETS binding or displace it from its binding site.
Probability and certainty markers in French and in Spanish (sans doute / sin duda)
Authors: Miche Elisabeth , Lorda Clara Ubaldina
Published: May 2014

In this article, we analyse the modal forms sans doute and sin duda. (lit. without doubts or undoubtedly). Despite their formal similarity, they do not always represent the same degree of certainty in French and Spanish. After a detailed analysis of their use in both languages, our conclusions show that sans doute is a probability marker, whereas sin duda is an (almost) certainty marker. After examining the relationship of these modal markers with evidentiality, we underscore the epistemic character of both markers; they are related to belief and subjectivity, thus the nature of certainty that they express is indirect and subjective. Sin duda manifests a higher degree of conviction than sans doute.
Supplementation of Vitis thunbergii root extract alleviated high-fat diet-induced obesity in C57BL/6J mice
Authors: Hsu Hong-Ming , Chen Wen-Ying , Hu Tzer-Kuan , Mao Frank Chiahung
Published: May 2014

Vitis thunbergii root, widely used as folk medicine in Taiwan, has been found to contain polyphenolic compounds and resveratrol derivatives, which have been implicated in the prevention and treatment of obesity. Thus, we hypothesized it might show beneficial effects against obesity. C57BL/6JNarl mice fed with a high fat diet for 14 weeks increased body weight and epididymal fat pad weight, and accompanied by fatty liver, hyperglycemia, hyperinsulinemia, insulin resistance, hyperleptinemia, hypercholesterolemia, hyper-LDL-cholesterol, and high level of serum GPT, GOT, creatinine, and BUN. Supplementation of VTE in the last 7 weeks remarkably decreased body weight and epididymal fat pad weight, implying a potential anti-obesity effect. Mechanistic study showed that VTE supplementation increased energy expenditure-related CPT1 mRNA expression and AMPK phosphorylation, and decreased lipogenesis-related SREBP-1 expression in liver. In conclusion, Vitis thunbergii roots could alleviate high fat diet-induced obesity and its related complications by enhancing hepatic fatty acid oxidation and inhibitng lipogenesis.
Biochemical analyses of ppGpp effect on adenylosuccinate synthetases, key enzymes in purine biosynthesis in rice
Authors: Nomura Yuhta , Nozawa Akira , Tozawa Yuzuru
Published: May 2014

The ppGpp-signaling system functions in plant chloroplasts. In bacteria, a negative effect of ppGpp on adenylosuccinate synthetase (AdSS) has been suggested. Our biochemical analysis also revealed rice AdSS homologs are apparently sensitive to ppGpp. However, further investigation clarified that this phenomenon is cancelled by the high substrate affinity to the enzymes, leading to a limited effect of ppGpp on adenylosuccinate synthesis.
A protocol for in vitro production of microtubers in Chinese yam (Dioscorea opposita)
Authors: Li Mingjun , Li Junhua , Liu Wen , Liu Luying , Lu Jie , Niu Jia , Liu Xinying , Yang Qingxiang
Published: May 2014

Chinese yam (Dioscorea opposita) is an important tuberous crop owing to its dual use as a food as well as a medicine. Tissue culture techniques allow the rapid multiplication of virus-free plant materials. The use of microtubers offers an attractive alternative to in vitro-grown plantlets for the micropropagation and exchange of healthy Chinese yam materials. A protocol for the in vitro production of Chinese yam microtubers was developed in this study. Though we tested both one-step and two-step procedures, only the two-step procedure showed favorable results for tuberization. Media with 60 g L−1 sucrose yielded the highest microtuber index. We demonstrate that table sugar was an efficient and economical alternative to analytical grade sucrose for microtuber production. Using an orthogonal experimental design, we determined the optimal growth regulator combination for microtuber induction and development. The microtubers obtained from our protocol sprouted readily both in vitro and in soil.
Chromophores in photoproteins of a glowing squid and mollusk
Authors: Kuse Masaki
Published: May 2014

Bioluminescence is a chemical reaction process for light emission in vivo. An organic substance is normally oxidized in the protein to obtain the energy required for the light emission. Determination of the structure of the substance is one of the most important parts of bioluminescent research. Photoproteins of a flying squid and a mollusk contain chromophores that are formed by connecting an apo-protein and dehydrocoelenterazine. The chromophore has a chemical structure that can emit light in a photoprotein. The structural analysis of the chromophores in the photoproteins is described.
Signal transmission within the P2X2 trimeric receptor
Authors: Keceli Batu , Kubo Yoshihiro
Published: May 2014

P2X2 receptor channel, a homotrimer activated by the binding of extracellular adenosine triphosphate (ATP) to three intersubunit ATP-binding sites (each located ∼50 Å from the ion permeation pore), also shows voltage-dependent activation upon hyperpolarization. Here, we used tandem trimeric constructs (TTCs) harboring critical mutations at the ATP-binding, linker, and pore regions to investigate how the ATP activation signal is transmitted within the trimer and how signals generated by ATP and hyperpolarization converge. Analysis of voltage- and [ATP]-dependent gating in these TTCs showed that: (a) Voltage- and [ATP]-dependent gating of P2X2 requires binding of at least two ATP molecules. (b) D315A mutation in the β-14 strand of the linker region connecting the ATP-binding domains to the pore-forming helices induces two different gating modes; this requires the presence of the D315A mutation in at least two subunits. (c) The T339S mutation in the pore domains of all three subunits abolishes the voltage dependence of P2X2 gating in saturating [ATP], making P2X2 equally active at all membrane potentials. Increasing the number of T339S mutations in the TTC results in gradual changes in the voltage dependence of gating from that of the wild-type channel, suggesting equal and independent contributions of the subunits at the pore level. (d) Voltage- and [ATP]-dependent gating in TTCs differs depending on the location of one D315A relative to one K308A that blocks the ATP binding and downstream signal transmission. (e) Voltage- and [ATP]-dependent gating does not depend on where one T339S is located relative to K308A (or D315A). Our results suggest that each intersubunit ATP-binding signal is directly transmitted on the same subunit to the level of D315 via the domain that contributes K308 to the β-14 strand. The signal subsequently spreads equally to all three subunits at the level of the pore, resulting in symmetric and independent contributions of the three subunits to pore opening.
Fujiwara’s theorem for equivariant correspondences
Authors: Olsson Martin
Published: May 2014

In this paper we study a generalization to stacks of Fujiwara’s theorem on the traces of correspondences acting on the cohomology of varieties over finite fields. We explain how to define naive local terms in the stack-theoretic context and state a conjectural generalization of Fujiwara’s theorem in this setting. We prove the conjecture for correspondences arising from group actions.
Control of self-motion in dynamic fluids: fish do it differently from bees
Authors: Scholtyssek Christine , Dacke Marie , Kröger Ronald , Baird Emily
Published: May 2014

To detect and avoid collisions, animals need to perceive and control the distance and the speed with which they are moving relative to obstacles. This is especially challenging for swimming and flying animals that must control movement in a dynamic fluid without reference from physical contact to the ground. Flying animals primarily rely on optic flow to control flight speed and distance to obstacles. Here, we investigate whether swimming animals use similar strategies for self-motion control to flying animals by directly comparing the trajectories of zebrafish (Danio rerio) and bumblebees (Bombus terrestris) moving through the same experimental tunnel. While moving through the tunnel, black and white patterns produced (i) strong horizontal optic flow cues on both walls, (ii) weak horizontal optic flow cues on both walls and (iii) strong optic flow cues on one wall and weak optic flow cues on the other. We find that the mean speed of zebrafish does not depend on the amount of optic flow perceived from the walls. We further show that zebrafish, unlike bumblebees, move closer to the wall that provides the strongest visual feedback. This unexpected preference for strong optic flow cues may reflect an adaptation for self-motion control in water or in environments where visibility is limited.
USNCTAM perspectives on mechanics in medicine
Authors: Bao Gang , Bazilevs Yuri , Chung Jae-Hyun , Decuzzi Paolo , Espinosa Horacio D. , Ferrari Mauro , Gao Huajian , Hossain Shaolie S. , Hughes Thomas J. R. , Kamm Roger D. , Liu Wing Kam , Marsden Alison , Schrefler Bernhard
Published: May 2014

Over decades, the theoretical and applied mechanics community has developed sophisticated approaches for analysing the behaviour of complex engineering systems. Most of these approaches have targeted systems in the transportation, materials, defence and energy industries. Applying and further developing engineering approaches for understanding, predicting and modulating the response of complicated biomedical processes not only holds great promise in meeting societal needs, but also poses serious challenges. This report, prepared for the US National Committee on Theoretical and Applied Mechanics, aims to identify the most pressing challenges in biological sciences and medicine that can be tackled within the broad field of mechanics. This echoes and complements a number of national and international initiatives aiming at fostering interdisciplinary biomedical research. This report also comments on cultural/educational challenges. Specifically, this report focuses on three major thrusts in which we believe mechanics has and will continue to have a substantial impact. (i) Rationally engineering injectable nano/microdevices for imaging and therapy of disease. Within this context, we discuss nanoparticle carrier design, vascular transport and adhesion, endocytosis and tumour growth in response to therapy, as well as uncertainty quantification techniques to better connect models and experiments. (ii) Design of biomedical devices, including point-of-care diagnostic systems, model organ and multi-organ microdevices, and pulsatile ventricular assistant devices. (iii) Mechanics of cellular processes, including mechanosensing and mechanotransduction, improved characterization of cellular constitutive behaviour, and microfluidic systems for single-cell studies.
Modelling and analysis of bacterial tracks suggest an active reorientation mechanism in
Rhodobacter sphaeroides
Authors: Rosser Gabriel , Baker Ruth E. , Armitage Judith P. , Fletcher Alexander G.
Published: May 2014

Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species
Rhodobacter sphaeroides
. The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in
R. sphaeroides
. This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation.