bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutritional and Metabolic Support in Adults With Amyotrophic Lateral Sclerosis
Authors: McDonagh Michelle
Published: March 2013

Amyotrophic lateral sclerosis (ALS) is an incurable, degenerative, neuromuscular condition. Nutritional and metabolic support is an integral component of care for patients with ALS because those capable of maintaining a normal nutrition status exhibit a slower rate of disease progression. Although there are multiple barriers to maintaining a normal nutrition status, the multidisciplinary team approach can facilitate early identification of symptoms, early intervention, and better outcomes for these patients. Barriers that patients often encounter include dysphagia, hypermetabolism, hypometabolism, upper extremity weakness, early satiety, constipation, depression, and loss of appetite. The role of the registered dietitian in the multidisciplinary ALS clinic is to intervene by providing a high standard of nutrition support. Further research into other facets of nutrition for ALS could lead to new interventions to slow weight loss and provide evidence-based guidelines for nutrition professionals. Areas for further research include the use of appetite stimulants, dietary supplements, delayed gastric motility, diet composition, metabolic rate, and the development of a standard equation for estimation of caloric needs in ALS.
Reactive conformations and non-Markovian cyclization kinetics of a Rouse polymer
Authors: Guérin T. , Bénichou O. , Voituriez R.
Published: March 2013

We investigate theoretically the physics of diffusion-limited intramolecular polymer reactions. The present work completes and goes beyond a previous study [T. Guérin, O. Bénichou, and R. Voituriez, Nat. Chem. 4, 568 (2012)10.1038/nchem.1378] that showed that the distribution of the polymer conformations at the very instant of reaction plays a key role in the cyclization kinetics, and takes explicitly into account the non-Markovian nature of the reactant motion. Here, we present in detail this non-Markovian theory, and compare it explicitly with existing Markovian theories and with numerical stochastic simulations. A large focus is made on the description of the non-equilibrium reactive conformations, with both numerical and analytical tools. We show that the reactive conformations are elongated and are characterized by a spectrum with a slowly decreasing tail, implying that the monomers that neighbor the reactive monomers are significantly shifted at the instant of reaction. We complete the study by deriving explicit formulas for the reaction rates in the Markovian Wilemski-Fixman theory when the reactants are located in arbitrary positions in the chain. We also give a simple scaling argument to understand the existence of two regimes in the reaction time, that come from two possible behaviors of monomer motion, which can be either diffusive or subdiffusive.
An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading
Authors: Oswald Benjamin B. , Schuren Jay C. , Pagan Darren C. , Miller Matthew P.
Published: March 2013

An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 °C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic processing and operating conditions of engineering components. The loaded specimen is reoriented with respect to the incident beam of x-rays using two rotational axes to increase the number of crystal orientations interrogated. The system was used at the Cornell High Energy Synchrotron Source to conduct experiments on single crystal silicon and polycrystalline Low Solvus High Refractory nickel-based superalloy. The data from these experiments provide new insights into how stresses evolve at the crystal scale during thermomechanical loading and complement the development of high-fidelity material models.
Self-assembly of cyclic rod-coil diblock copolymers
Authors: He Linli , Chen Zenglei , Zhang Ruifen , Zhang Linxi , Jiang Zhouting
Published: March 2013

The phase behavior of cyclic rod-coil diblock copolymer melts is investigated by the dissipative particle dynamics simulation. In order to understand the effect of chain topological architecture better, we also study the linear rod-coil system. The comparison of the calculated phase diagrams between the two rod-coil copolymers reveals that the order-disorder transition point (χN)ODT for cyclic rod-coil diblock copolymers is always higher than that of equivalent linear rod-coil diblocks. In addition, the phase diagram for cyclic system is more “symmetrical,” due to the topological constraint. Moreover, there are significant differences in the self-assembled overall morphologies and the local molecular arrangements. For example, frod = 0.5, both lamellar structures are formed while rod packing is different greatly in cyclic and linear cases. The lamellae with rods arranged coplanarly into bilayers occurs in cyclic rod-coil diblocks, while the lamellar structure with rods arranged end by end into interdigitated bilayers appears in linear counterpart. In both the lamellar phases, the domain size ratio of cyclic to linear diblocks is ranged from 0.63 to 0.70. This is attributed to that the cyclic architecture with the additional junction increases the contacts between incompatible blocks and prevents the coil chains from expanding as much as the linear cases. As frod = 0.7, the hexagonally packed cylinder is observed for cyclic rod-coil diblocks, while liquid-crystalline smectic A lamellar phase is formed in linear system. As a result, the cyclization of a linear rod-coil block copolymer can induce remarkable differences in the self-assembly behavior and also diversify its physical properties and applications greatly.
Diffusive hydrogen inter-cage migration in hydrogen and hydrogen-tetrahydrofuran clathrate hydrates
Authors: Cao Huayu , English Niall J. , MacElroy J. M. D.
Published: March 2013

Classical equilibrium molecular dynamics simulations have been performed to investigate the diffusive properties of inter-cage hydrogen migration in both pure hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 0.05 kbar from 200 K and up to 250–260 K. For mixed H2-THF systems in which there is single H2 occupation of the small cage (labelled “1S1L”), we found that no H2 migration occurs. However, for more densely filled H2-THF and pure-H2 systems, in which there is more than single H2 occupation in the small cage, there is an onset of inter-cage H2 migration events from the small cages to neighbouring cavities at around 200 K. The mean square displacements of the hydrogen molecules were fitted to a mathematical model consisting of an anomalous term and a Fickian component, and nonlinear regression fitting was conducted to estimate long-time (inter-cage) diffusivities. An approximate Arrhenius temperature relationship for the diffusion coefficient was examined and an estimation of the hydrogen hopping energy barrier was calculated for each system.
An electric stimulation system for electrokinetic particle manipulation in microfluidic devices
Authors: Lopez-de la Fuente M. S. , Moncada-Hernandez H. , Perez-Gonzalez V. H. , Lapizco-Encinas B. H. , Martinez-Chapa S. O.
Published: March 2013

Microfluidic devices have grown significantly in the number of applications. Microfabrication techniques have evolved considerably; however, electric stimulation systems for microdevices have not advanced at the same pace. Electric stimulation of micro-fluidic devices is an important element in particle manipulation research. A flexible stimulation instrument is desired to perform configurable, repeatable, automated, and reliable experiments by allowing users to select the stimulation parameters. The instrument presented here is a configurable and programmable stimulation system for electrokinetic-driven microfluidic devices; it consists of a processor, a memory system, and a user interface to deliver several types of waveforms and stimulation patterns. It has been designed to be a flexible, highly configurable, low power instrument capable of delivering sine, triangle, and sawtooth waveforms with one single frequency or two superimposed frequencies ranging from 0.01 Hz to 40 kHz, and an output voltage of up to 30 Vpp. A specific stimulation pattern can be delivered over a single time period or as a sequence of different signals for different time periods. This stimulation system can be applied as a research tool where manipulation of particles suspended in liquid media is involved, such as biology, medicine, environment, embryology, and genetics. This system has the potential to lead to new schemes for laboratory procedures by allowing application specific and user defined electric stimulation. The development of this device is a step towards portable and programmable instrumentation for electric stimulation on electrokinetic-based microfluidic devices, which are meant to be integrated with lab-on-a-chip devices.
Electron energy-loss spectroscopy of boron-doped layers in amorphous thin film silicon solar cells
Authors: Duchamp M. , Boothroyd C. B. , Moreno M. S. , van Aken B. B. , Soppe W. J. , Dunin-Borkowski R. E.
Published: March 2013

Electron energy-loss spectroscopy (EELS) is used to study p-doped layers in n-i-p amorphous thin film Si solar cells grown on steel foil substrates. For a solar cell in which an intrinsic amorphous hydrogenated Si (a-Si-H) layer is sandwiched between 10-nm-thick n-doped and p-doped a-Si:H layers, we assess whether core-loss EELS can be used to quantify the B concentration. We compare the shape of the measured B K edge with real space ab initio multiple scattering calculations and show that it is possible to separate the weak B K edge peak from the much stronger Si L edge fine structure by using log-normal fitting functions. The measured B concentration is compared with values obtained from secondary ion mass spectrometry, as well as with EELS results obtained from test samples that contain ∼200-nm-thick a-Si:H layers co-doped with B and C. We also assess whether changes in volume plasmon energy can be related to the B concentration and/or to the density of the material and whether variations of the volume plasmon line-width can be correlated with differences in the scattering of valence electrons in differently doped a-Si:H layers.
Two- and three-dimensional modeling and optimization applied to the design of a fast hydrodynamic focusing microfluidic mixer for protein folding
Authors: Ivorra Benjamin , Redondo Juana L. , Santiago Juan G. , Ortigosa Pilar M. , Ramos Angel M.
Published: March 2013

We present a design of a microfluidic mixer based on hydrodynamic focusing which is used to initiate the folding process (i.e., changes of the molecular structure) of a protein. The folding process is initiated by diluting (from 90% to 30%) the local denaturant concentration (initially 6 M GdCl solution) in a short time interval we refer to as mixing time. Our objective is to optimize this mixer by choosing suitable shape and flow conditions in order to minimize this mixing time. To this end, we first introduce a numerical model that enables computation of the mixing time of a mixer. This model is based on a finite element method approximation of the incompressible Navier-Stokes equations coupled with the convective diffusion equation. To reduce the computational time, this model is implemented in both full three-dimensional (3D) and simplified two-dimensional (2D) versions; and we analyze the ability of the 2D model to approximate the mixing time predicted by the 3D model. We found that the 2D model approximates the mixing time predicted by the 3D model with a mean error of about 15%, which is considered reasonable. Then, we define a mixer optimization problem considering the 2D model and solve it using a hybrid global optimization algorithm. In particular, we consider geometrical variables and injection velocities as optimization parameters. We achieve a design with a predicted mixing time of 0.10 μs, approximately one order of magnitude faster than previous mixer designs. This improvement can be in part explained by the new mixer geometry including an angle of π/5 radians at the channel intersection and injections velocities of 5.2 m s−1 and 0.038 m s−1 for the side and central inlet channels, respectively. Finally, we verify the robustness of the optimized result by performing a sensitivity analysis of its parameters considering the 3D model. During this study, the optimized mixer was demonstrated to be robust by exhibiting mixing time variations of the same order than the parameter ones. Thus, the obtained 2D design can be considered optimal also for the 3D model.
Bond energy decomposition analysis for subsystem density functional theory
Authors: Beyhan S. Maya , Götz Andreas W. , Visscher Lucas
Published: March 2013

We employed an explicit expression for the dispersion (D) energy in conjunction with Kohn-Sham (KS) density functional theory and frozen-density embedding (FDE) to calculate interaction energies between DNA base pairs and a selected set of amino acid pairs in the hydrophobic core of a small protein Rubredoxin. We use this data to assess the accuracy of an FDE-D approach for the calculation of intermolecular interactions. To better analyze the calculated interaction energies we furthermore propose a new energy decomposition scheme that is similar to the well-known KS bond formation analysis [F. M. Bickelhaupt and E. J. Baerends, Rev. Comput. Chem. 15, 1 (2000)10.1002/9780470125922.ch1], but differs in the electron densities used to define the bond energy. The individual subsystem electron densities of the FDE approach sum to the total electron density which makes it possible to define bond energies in terms of promotion energies and an explicit interaction energy. We show that for the systems considered only a few freeze-and-thaw cycles suffice to reach convergence in these individual bond energy components, illustrating the potential of FDE-D as an efficient method to calculate intermolecular interactions.
Pressure-induced phase transition and polymerization of tetracyanoethylene (TCNE)
Authors: Tomasino Dane , Chen Jing-Yin , Kim Minesob , Yoo Choong-Shik
Published: March 2013

We have studied the pressure-induced physical and chemical transformations of tetracyanoethylene (TCNE or C6N4) in diamond anvil cells using micro-Raman spectroscopy, laser-heating, emission spectroscopy, and synchrotron x-ray diffraction. The results indicate that TCNE in a quasi-hydrostatic condition undergoes a shear-induced phase transition at 10 GPa and then a chemical change to two-dimensional (2D) C=N polymers above 14 GPa. These phase and chemical transformations depend strongly on the state of stress in the sample and occur sluggishly in non-hydrostatic conditions over a large pressure range between 7 and 14 GPa. The x-ray diffraction data indicate that the phase transition occurs isostructurally within the monoclinic structure (P21/c) without any apparent volume discontinuity and the C=N polymer is highly disordered but remains stable to 60 GPa—the maximum pressure studied. On the other hand, laser-heating of the C=N polymer above 25 GPa further converts to a theoretically predicted 3D C–N network structure, evident from an emergence of new Raman νs(C–N) at 1404 cm−1 at 25 GPa and the visual appearance of translucent solid. The C–N product is, however, unstable upon pressure unloading below 10 GPa, resulting in a grayish powder that can be considered as nano-diamonds with high-nitrogen content at ambient pressure. The C–N product shows a strong emission line centered at 640 nm at 30 GPa, which linearly shifts toward shorter wavelength at the rate of −1.38 nm/GPa. We conjecture that the observed red shift upon unloading pressure is due to increase of defects in the C–N product and thereby weakening of C–N bonds.
Oscillator strengths of electronic excitations with response theory using phase including natural orbital functionals
Authors: van Meer R. , Gritsenko O. V. , Giesbertz K. J. H. , Baerends E. J.
Published: March 2013

The key characteristics of electronic excitations of many-electron systems, the excitation energies ωα and the oscillator strengths fα, can be obtained from linear response theory. In one-electron models and within the adiabatic approximation, the zeros of the inverse response matrix, which occur at the excitation energies, can be obtained from a simple diagonalization. Particular cases are the eigenvalue equations of time-dependent density functional theory (TDDFT), time-dependent density matrix functional theory, and the recently developed phase-including natural orbital (PINO) functional theory. In this paper, an expression for the oscillator strengths fα of the electronic excitations is derived within adiabatic response PINO theory. The fα are expressed through the eigenvectors of the PINO inverse response matrix and the dipole integrals. They are calculated with the phase-including natural orbital functional for two-electron systems adapted from the work of L\documentclass[12pt]{minimal}\begin{document}$\mathrm{\ddot{o}}$\end{document}öwdin and Shull on two-electron systems (the phase-including Löwdin-Shull functional). The PINO calculations reproduce the reference fα values for all considered excitations and bond distances R of the prototype molecules H2 and HeH+ very well (perfectly, if the correct choice of the phases in the functional is made). Remarkably, the quality is still very good when the response matrices are severely restricted to almost TDDFT size, i.e., involving in addition to the occupied-virtual orbital pairs just (HOMO+1)-virtual pairs (R1) and possibly (HOMO+2)-virtual pairs (R2). The shape of the curves fα(R) is rationalized with a decomposition analysis of the transition dipole moments.
Representing the vacuum polarization on de Sitter
Authors: Leonard Katie E. , Prokopec Tomislav , Woodard Richard P.
Published: March 2013

Previous studies of the vacuum polarization on de Sitter have demonstrated that there is a simple, noncovariant representation of it in which the physics is transparent. There is also a cumbersome, covariant representation in which the physics is obscure. Despite being unwieldy, the latter form has a powerful appeal for those who are concerned about de Sitter invariance. We show that nothing is lost by employing the simple, noncovariant representation because there is a closed form procedure for converting its structure functions to those of the covariant representation. We also present a vastly improved technique for reading off the noncovariant structure functions from the primitive diagrams. And we discuss the issue of representing the vacuum polarization for a general metric background.
Ground state solutions for nonlinear fractional Schrödinger equations in $\mathbb {R}^N$RN
Authors: Secchi Simone
Published: March 2013

We construct solutions to a class of Schrödinger equations involving the fractional Laplacian. Our approach is variational in nature, and based on minimization on the Nehari manifold.
Electron transport at interface of LaAlO3 and SrTiO3 band insulators
Authors: Su Shanshan , Ho You Jeong , Lee Chibum
Published: March 2013

Electron transport properties at n-type LaAlO3/SrTiO3 interfaces have been investigated numerically. Carrier distributions, band structures, and sheet density have been calculated by solving Schrödinger equations with Poisson equation in a self-consistent manner for various LaAlO3/SrTiO3 interfaces with and without atomic interdiffusions. It was found that the interface with A-site atom interdiffusion has the critical thickness of 4 unit cells below which it remains insulating. Most electrons are localized within 10 nm from the interface forming two-dimensional electron gas and multi-subbands are occupied indicating the multi-channel conduction. Electron mobility along the A-site atom interdiffused interface has been calculated using the linearized Boltzmann transport equation including scattering mechanisms of acoustic phonon, polar optical phonon, interface roughness, and net charged layers. At low temperature, the mobility is limited by the interface roughness and net charged layers. At room temperature, the polar optical phonon is the dominant electron scattering mechanism and the mobility is almost independent from the thickness of LaAlO3 film.
Reduced losses in rolled Fe73.5Si15.5Nb3B7Cu1 nanocrystalline ribbon
Authors: Kernion S. J. , Lucas M. S. , Horwath J. , Turgut Z. , Michel E. , Keylin V. , Huth J. F. , Leary A. M. , Shen S. , McHenry M. E.
Published: March 2013

Eddy currents in magnetic components undergoing high frequency switching can be mitigated by reducing the thickness of the component. Planar flow cast Fe73.5Si15.5Nb3B7Cu1 ribbon was plastically deformed by cold rolling, resulting in a thickness reduction of 38%. Shear band formation was seen and the coercivity was dramatically higher in the rolled ribbon. After crystallization, the hysteresis loop of the rolled ribbon was nearly identical to a non-rolled ribbon and losses were lower in the rolled ribbon above 25 kHz. Reductions in thickness by this method can lead to increases in operating frequency for power conversion applications.
High-charge energetic electron bunch generated by intersecting laser pulses
Authors: Yang Lei , Deng Zhigang , Zhou C. T. , Yu M. Y. , Wang Xingang
Published: March 2013

The interaction of two energetic electron bunches generated in the wakefields of two intense intersecting laser pulses in rarefied plasmas is investigated using particle-in-cell simulations. It is found that, with suitable intersection angle between the two laser pulses, the initially independent wakefield accelerated electron bunches can merged into a single one with high charge, energy, and narrow energy spread. The dynamics of the laser-pulse intersection and wake-bubble merging process is also investigated, and the crucial roles of the intersection angle are pointed out and analyzed.
Note: Size effects on the tensile response of top-down fabricated Si nanobeams
Authors: Houri S. , Bhaskar U. , Pardoen T. , Raskin J.-P.
Published: March 2013

The tensile response of top-down fabricated sc-Si nanobeams is inferred from the fitting of stress-strain data obtained under tensile loading conditions over a large range of deformation. The testing is performed using MEMS structures consisting of two connected beams; a highly stressed silicon-nitride (SiN) beam connected to a sc-Si specimen beam. The high tensile stress component present upon the deposition of the SiN loads the sc-Si beam once the entire structure is released. The strain and stress values are extracted independently, respectively, by scanning electron microscopy inspection and vibration frequency measurement of the released tensile MEMS structures. The tensile tests are undertaken for six thicknesses to determine the dependence of the elastic response on dimensions. The Young's modulus shows a variation of 40% for thicknesses ranging from 200 to 30 nm.
Modeling of the infrared photodetector based on multi layer armchair graphene nanoribbons
Authors: Ahmadi E. , Asgari A.
Published: March 2013

Armchair graphene nanoribbons (A-GNRs), an alternative material for Infrared (IR) photodetectors, attract more attention because of those tunable energy gaps by changing the width of nanoribbons and the height of interband transition. In this paper, we calculate the dark current limited detectivity, D*, of the multi layer A-GNR based IR photodetector. For this purpose, we find the band structure of A-GNRs by tight-binding model and by considering the edge deformation, the absorption coefficient using the single electron approximation, the quantum efficiency, and the optical responsivity of photodetector. Then, the dark current of photodetector has been calculated by considering two contributions: (i) The interband tunneling generation and (ii) the thermogeneration due to the optical and acoustic phonon and line edge roughness (LER) scattering in the A-GNRs. Finally, we optimize the dark current limited detectivity of the photodetector for different structural parameters. The obtained results show that for the single layer A-GNR based photodetector with W = 5 nm, L = 20 μm, Vb = 2 V, Vg = 2 V, maximum value of dark current limited detectivity, D*, at T = 300 K is ∼2.2 × 108 (cm Hz1/2/W) and at T = 77 K is ∼2.1 × 1011 (cm Hz1/2/W). Also, for narrow A-GNRs, D* increases with increasing the gate voltage, while for wider A-GNRs decreases with increasing the gate voltage. Moreover, the dark current limited detectivity increases with increasing the number of the A-GNR layers.
Microwave guiding in air along single femtosecond laser filament
Authors: Ren Yu , Alshershby Mostafa , Qin Jiang , Hao Zuoqiang , Lin Jingquan
Published: March 2013

Microwave guiding along single plasma filament generated through the propagation of femtosecond (fs) laser pulses in air has been demonstrated over a distance of about 6.5 cm, corresponding to a microwave signal intensity enhancement of more than 3-fold over free space propagation. The current propagation distance along the fs laser filament is in agreement with the calculations and limited by the relatively high resistance of the single plasma filament. Using a single fs laser filament to channel microwave radiation considerably alleviate requirements to the power of fs laser pulses compared to the case of the circular filaments waveguide. In addition, it can be used as a simple and non-intrusive method to obtain the basic parameters of laser-generated plasma filament.
Effect of tin on point defects and oxygen precipitation in Czochralski silicon: Experimental and theoretical studies
Authors: Gao Chao , Ma Xiangyang , Zhao Jianjiang , Yang Deren
Published: March 2013

The effect of tin (Sn)-doping on point defects and oxygen precipitation (OP) in Czochralski (CZ) silicon has been investigated by experiment and theoretical calculations based on density functional theory (DFT). It is found that Sn plays different roles in affecting OP according to the amount of introduced vacancies. That is, Sn suppresses OP in vacancy-lean CZ silicon but promotes OP in vacancy-rich CZ silicon. The effects of Sn-doping on the formation and annihilation of point defects as well as on the evolution of vacancy- and oxygen-related complexes have been systematically studied using DFT calculations. Based on the experimental and theoretical results, it is postulated that Sn atoms in silicon act as vacancy reservoirs which modify the formation and annihilation of vacancies as well as the evolution of vacancy-related complexes. The mechanism for the different roles of Sn in affecting OP is discussed based on the DFT calculations.
Magnetization reversal in sub-100 nm magnetic tunnel junctions with ultrathin MgO barrier biased along the hard axis
Authors: Cascales J. P. , Herranz D. , Sambricio J. L. , Ebels U. , Katine J. A. , Aliev F. G.
Published: March 2013

We report on room temperature magnetoresistance and low frequency noise in sub-100 nm elliptic CoFeB/MgO/CoFeB magnetic tunnel junctions with ultrathin (0.9 nm) barriers. For magnetic fields applied along the hard axis, we observe current induced magnetization switching between the antiparallel and parallel alignments at dc current densities as low as 4 × 106 A/cm2. We attribute the low value of the critical current to the influence of localized reductions in the tunnel barrier, which affects the current distribution. The analysis of random telegraph noise, which appears in the field interval near a magnetization switch, provides an estimate to the dimension of the pseudo pinholes that trigger the magnetization switching via local spin torque. Micromagnetic simulations qualitatively and quantitatively reproduce the main experimental observations.
Realizing a high magnetic moment in Gd/Cr/FeCo: The role of the rare earth
Authors: Ward C. , Scheunert G. , Hendren W. R. , Hardeman R. , Gubbins M. A. , Bowman R. M.
Published: March 2013

The search for materials or systems exhibiting a high magnetic saturation has been of longstanding importance. It has been suggested that increased saturation could be achieved by coupling a transition metal via a spacer to a rare earth. We report Gd/Cr/Fe70Co30 multilayer stacks and find reduced yet modulating magnetic moment as a function of Cr thickness. Through a micro structural analysis, the lowered moment is indicated by the nucleation of the ultrathin Gd films into a face-centered cubic (fcc) phase. We discuss the possible solution in terms of quasi-perfect lattice match seed material to promote growth of hcp Gd.
Structural analysis of Au/TiO2 thin films deposited on the glass substrate
Authors: Kawasaki Masahiro , Chen Miin-Jang , Yang Jer-Ren , Chiou Wen-An , Shiojiri Makoto
Published: March 2013

Analytical electron microscopy has revealed the structure of thin films of thermally evaporated Au on atomic layer deposition (ALD) TiO2 deposited on glass substrates. An 11 nm thick TiO2 film was deposited at 200 °C with 417 ALD cycles using tetrakisdimethylamido titanium and H2O precursors. The Au film comprised small particles with diameters of ∼15 nm or less grown by Volmer-Weber growth mechanism on the TiO2 layer. Transmission electron microscopy analysis of the ALD TiO2 layer showed that it was amorphous and had Ca atoms incorporated into the film probably from the lime glass substrate. The effect of Ca atoms included in the TiO2 layer on the growth of Au particles is discussed.
Colossal piezoresistance effect in Sm0.55(Sr0.5Ca0.5)0.45MnO3 single crystal
Authors: Mohan Radheep D. , Sarkar P. , Arumugam S. , Mandal P.
Published: March 2013

We have investigated the effect of uniaxial pressure (P) on electrical resistivity along the ab plane and c axis in a single crystal of Sm0.55(Sr0.5Ca0.5)0.45MnO3. A huge piezoresistance (PR ∼107% at P = 90 MPa) and a remarkable increase (at the rate of ∼79 K/GPa) of metal-insulator transition temperature (TMI) have been observed for P applied along the c axis, while TMI decreases at the rate of ∼77 K/GPa for P perpendicular to the c axis. These values of PR and dTMI/dP are much larger than those observed in other perovskite and bilayer manganites. Such colossal PR and large value of dTMI/dP may be utilized for various technological applications.
Morphology-controlled synthesis of silver nanoparticles on the silicon substrate by a facile silver mirror reaction
Authors: Jiang Bing , Li Meicheng , Bai Fan , Yu Hang , Mwenya Trevor , Li Yingfeng , Song Dandan
Published: March 2013

The Ag nanoparticles (Ag-NPs) with different morphology were quickly deposited on p-type Si substrate by a facile silver mirror reaction without capping agents and morphology driving seeds at room temperature. By controlling the concentrations of [Ag(NH3)2]+ and reducing agent (glucose), short rod and quasi-round Ag-NPs were produced on Si substrate. The results show that the shape of the Ag-NPs was defined by [Ag(NH3)2]+ concentration. The concentration of glucose affected the coverage fraction instead of shape of Ag-NPs. Under the high concentrations of [Ag(NH3)2]+, anisotropic crystal structure of short rod Ag-NPs were ascribed to total energy minimization. The high glucose concentration led to agglomeration of particles. Different nanoporous structures on Si substrate etched by using Ag-NPs enable control over its properties and are useful for the solar cells applications.
A negative-pressure-driven microfluidic chip for the rapid detection of a bladder cancer biomarker in urine using bead-based enzyme-linked immunosorbent assay
Authors: Lin Yen-Heng , Chen Ying-Ju , Lai Chao-Sung , Chen Yi-Ting , Chen Chien-Lun , Yu Jau-Song , Chang Yu-Sun
Published: March 2013

This paper describes an integrated microfluidic chip that is capable of rapidly and quantitatively measuring the concentration of a bladder cancer biomarker, apolipoprotein A1, in urine samples. All of the microfluidic components, including the fluid transport system, the micro-valve, and the micro-mixer, were driven by negative pressure, which simplifies the use of the chip and facilitates commercialization. Magnetic beads were used as a solid support for the primary antibody, which captured apolipoprotein A1 in patients' urine. Because of the three-dimensional structure of the magnetic beads, the concentration range of the target that could be detected was as high as 2000 ng ml−1. Because this concentration is 100 times higher than that quantifiable using a 96-well plate with the same enzyme-linked immunosorbent assay (ELISA) kit, the dilution of the patient's urine can be avoided or greatly reduced. The limit of detection was determined to be approximately 10 ng ml−1, which is lower than the cutoff value for diagnosing bladder cancer (11.16 ng ml−1). When the values measured using the microfluidic chip were compared with those measured using conventional ELISA using a 96-well plate for five patients, the deviations were 0.9%, 6.8%, 9.4%, 1.8%, and 5.8%. The entire measurement time is 6-fold faster than that of conventional ELISA. This microfluidic device shows significant potential for point-of-care applications.
Magnetoresistance in graphene under quantum limit regime
Authors: Zhou Yang-Bo , Wu Han-Chun , Yu Da-Peng , Liao Zhi-Min
Published: March 2013

We report the magnetoresistance (MR) in single-layer graphene field-effect transistors at different gate voltages. At low temperatures, the MR exhibits fluctuations at Dirac point, which is attributed to quantum interference effect. Apart from the Dirac point, the MR shows a linear behavior under the extreme quantum limit that is identified by Shubnikov-de Haas oscillations and quantum Hall effect. Our experimental results give a clear manifestation of the quantum linear MR.
Analysis of the expression of terpene synthase genes in relation to aroma content in two aromatic Vitis vinifera varieties
Authors: Matarese Fabiola , Scalabrelli Giancarlo , D'Onofrio Claudio
Published: March 2013

Grape (Vitis vinifera L.) flavour management in the vineyard requires knowledge of the derivation of individual flavour and aroma characteristics. Some of the most prevalent wine grape aroma constituents are terpenoids and this study represents a wide report about grape terpene synthase (TPS) gene transcript profiling in different tissues of two aromatic grapevine varieties, particularly flowers and developing berries, correlated with the accumulation patterns of free aroma compounds. All investigated genes belonging to the TPS-a and TPS-b subfamilies reached the highest expression in accordance with the peak of accumulation of the respective compounds. In the TPS-g subfamily, only one of the genes characterised for linalool synthases showed major transcript abundance in ripening berries, whereas the only geraniol synthase had a peak of expression in green berries and at the beginning of ripening, when geraniol concentration started to increase and overcome the linalool concentration. The genes identified in this study as being mainly responsible for linalool and geraniol synthesis during berry development, and the phenological phases in which they are mostly expressed, should be of interest to viticulturists and wine makers to improve decision making along the chain of production.
How integrated are services for patients with chronic obstructive pulmonary disease? Perceptions of patients and health care providers
Authors: Kirby S. E. , Mutimbe M. , Vagholkar S. , Bunker J. , Dennis S. M. , Liaw S.-T.
Published: March 2013

Chronic obstructive pulmonary disease (COPD) is a common cause of hospital readmissions worldwide. Outcomes for COPD patients improve if care is more integrated. COPD patients and their health care providers at a district hospital and community health service were interviewed about their perceptions of integration of care. Patients were confused about provider roles, had little understanding of their disease, had difficulty accessing services and did not have COPD action plans. Health care providers espoused integration of COPD care. Care was reasonably well integrated in the hospital. Integration of care was compromised in the community because COPD patients went to the emergency department when symptoms became unmanageable, while only attending their GPs for routine booked appointments. Integration could be improved if health care providers spent more time with patients, promoting understanding of the disease, supporting self-management and liaising with other providers. Patients would benefit from an action plan and additional support. Potentially preventable COPD admissions will continue without action to improve integration of community services and patients’ understanding of their condition.
Impacts of level of utilisation by grazing on an Astrebla (Mitchell grass) grassland in north-western Queensland between 1984 and 2010. 1. Herbage mass and population dynamics of Astrebla spp.
Authors: Orr D. M. , Phelps D. G.
Published: March 2013

Managing large variations in herbage production, resulting from highly variable seasonal rainfall, provides a major challenge for the sustainable management of Astrebla (Mitchell grass) grasslands in Australia. A grazing study with sheep was conducted between 1984 and 2010 on an Astrebla grassland in northern Queensland to describe the effects of a range of levels of utilisation of the herbage at the end of the summer growing season (April–May in northern Australia) on the sustainability of these grasslands. In unreplicated paddocks, sheep numbers were adjusted annually to achieve 0, 10, 20, 30, 50 and 80% utilisation of the herbage mass at the end of the summer over the ensuing 12 months. Higher levels of utilisation reduced both total and Astrebla spp. herbage mass because of the effects of higher utilisation on Astrebla spp. and this effect was accentuated by drought. The tussock density of Astrebla spp. varied widely among years but with few treatment differences until 2005 when density was reduced at the 50% level of utilisation. A major change in density resulted from a large recruitment of Astrebla spp. in 1989 that influenced its density for the remainder of the study. Basal area of the tussocks fluctuated among years, with increases due to rainfall and decreases during droughts. Seasonal rainfall was more influential than level of utilisation in changes to the basal area of perennial grasses. Drought resulted in the death of Astrebla spp. tussocks and this effect was accentuated at higher levels of utilisation. A series of three grazing exclosures were used to examine the recovery of the density and basal area of Astrebla spp. after it had been reduced by 80% utilisation over the preceding 9 years. This recovery study indicated that, although grazing exclusion was useful in the recovery of Astrebla spp., above-average rainfall was the major factor driving increases in the basal area of perennial grasses. Spring values of the Southern Oscillation Index and associated rainfall probabilities were considered to have potential for understanding the dynamics of Astrebla spp. It was concluded that Astrebla grassland remained sustainable after 26 years when grazed at up to 30% utilisation, while, at 50% utilisation, they became unsustainable after 20 years. Results from this study emphasised the need to maintain the population of Astrebla spp. tussocks.
Two modes of integrin activation form a binary molecular switch in adhesion maturation
Authors: Lee Ho-Sup , Anekal Praju , Lim Chinten James , Liu Chi-Chao , Ginsberg Mark H.
Published: March 2013

Talin-mediated integrin activation drives integrin-based adhesions. Here we examine the roles of two proteins that induce talin–integrin interactions—vinculin and Rap1-GTP-interacting adaptor molecule (RIAM)—in the formation and maturation of integrin-based adhesions. RIAM-containing adhesions are primarily in the lamellipodium; RIAM is subsequently reduced in mature focal adhesions due to direct competition with vinculin for talin-binding sites. We show that vinculin binding to talin induces Rap1-independent association of talin with integrins and resulting integrin activation, in sharp contrast to Rap1-dependent RIAM-induced activation. Vinculin stabilizes adhesions, increasing their ability to transmit force, whereas RIAM played a critical role in lamellipodial protrusion. Thus displacement of RIAM by vinculin acts as a molecular switch that mediates the transition of integrin-based adhesions from drivers of lamellipodial protrusion to stable, force-bearing adhesions. Consequently changes in the abundance of two multiprotein modules within maturing adhesions, one regulated by Rap1 and one by tension, result in the temporal evolution of adhesion functions.
Targeting and functional mechanisms of the cytokinesis‑related F‑BAR protein Hof1 during the cell cycle
Authors: Oh Younghoon , Schreiter Jennifer , Nishihama Ryuichi , Wloka Carsten , Bi Erfei
Published: March 2013

F-BAR proteins are membrane‑associated proteins believed to link the plasma membrane to the actin cytoskeleton in cellular processes such as cytokinesis and endocytosis. In the budding yeast Saccharomyces cerevisiae, the F‑BAR protein Hof1 localizes to the division site in a complex pattern during the cell cycle and plays an important role in cytokinesis. However, the mechanisms underlying its localization and function are poorly understood. Here we show that Hof1 contains three distinct targeting domains that contribute to cytokinesis differentially. The N‑terminal half of Hof1 localizes to the bud neck and the sites of polarized growth during the cell cycle. The neck localization is mediated mainly by an interaction between the second coiled‑coil region in the N‑terminus and the septin Cdc10, whereas the localization to the sites of polarized growth is mediated entirely by the F‑BAR domain. In contrast, the C‑terminal half of Hof1 interacts with Myo1, the sole myosin‑II heavy chain in budding yeast, and localizes to the bud neck in a Myo1‑dependent manner from the onset to the completion of cytokinesis. We also show that the SH3 domain in the C‑terminus plays an important role in maintaining the symmetry of Myo1 ring constriction during cytokinesis and that Hof1 interacts with Chs2, a chitin synthase that is required for primary septum formation. Together these data define a mechanism that accounts for the localization of Hof1 during the cell cycle and suggest that Hof1 may function in cytokinesis by coupling actomyosin ring constriction to primary septum formation through interactions with Myo1 and Chs2.
Mth1 regulates the interaction between the Rgt1 repressor and the Ssn6-Tup1 corepressor complex by modulating PKA-dependent phosphorylation of Rgt1
Authors: Roy Adhiraj , Shin Yong Jae , Cho Kyu Hong , Kim Jeong-Ho
Published: March 2013

Glucose uptake, the first, rate-limiting step of its utilization, is facilitated by glucose transporters. Expression of several glucose transporter (HXT) genes in yeast is repressed by the Rgt1 repressor, which recruits the glucose-responsive transcription factor Mth1 and the general corepressor complex Ssn6-Tup1 in the absence of glucose; however, it is derepressed when Mth1 is inactivated by glucose. Here we show that Ssn6-Tup1 interferes with the DNA-binding ability of Rgt1 in the absence of Mth1 and that the Rgt1 function abrogated by Ssn6 overexpression is restored by co-overexpression of Mth1. Thus Mth1 likely regulates Rgt1 function not by modulating its DNA-binding activity directly but by functionally antagonizing Ssn6-Tup1. Mth1 does so by acting as a scaffold-like protein to recruit Ssn6-Tup1 to Rgt1. Supporting evidence shows that Mth1 blocks the protein kinase A–dependent phosphorylation of Rgt1 that impairs the ability of Rgt1 to interact with Ssn6-Tup1. Of note, Rgt1 can bind DNA in the absence of Ssn6-Tup1 but does not inhibit transcription, suggesting that dissociation of Rgt1 from Ssn6-Tup1, but not from DNA, is necessary and sufficient for the expression of its target genes. Taken together, these findings show that Mth1 is a transcriptional corepressor that facilitates the recruitment of Ssn6-Tup1 by Rgt1.
Ca2+influx and the store-operated Ca2+entry pathway undergo regulation during mouse oocyte maturation
Authors: Cheon Banyoon , Lee Hoi-Chang , Wakai Takuya , Fissore Rafael A.
Published: March 2013

In preparation for fertilization, mammalian oocytes undergo optimization of the mechanisms that regulate calcium homeostasis. Among these changes is the increase in the content of the Ca2+stores ([Ca2+]ER), a process that requires Ca2+influx. Nevertheless, the mechanism(s) that mediates this influx remains obscure, although is known that [Ca2+]ERcan regulate Ca2+influx via store-operated Ca2+entry (SOCE). We find that during maturation, as [Ca2+]ERincreases, Ca2+influx decreases. We demonstrate that mouse oocytes/eggs express the two molecular components of SOCE—stromal interaction molecule 1 (Stim1) and Orai1—and expression of human (h) Stim1 increases Ca2+influx in a manner that recapitulates endogenous SOCE. We observe that the cellular distribution of hStim1 and hOrai1 during maturation undergoes sweeping changes that curtail their colocalization during the later stages of maturation. Coexpression of hStim1 and hOrai1 enhances influx throughout maturation but increases basal Ca2+levels only in GV oocytes. Further, expression of a constitutive active form of hStim1 plus Orai1, which increases basal Ca2+throughout maturation, disturbs resumption of meiosis. Taken together, our results demonstrate that Ca2+influx and SOCE are regulated during maturation and that alteration of Ca2+homeostasis undermines maturation in mouse oocytes.
The BEN domain is a novel sequence-specific DNA-binding domain conserved in neural transcriptional repressors
Authors: Dai Qi , Ren Aiming , Westholm Jakub O. , Serganov Artem A. , Patel Dinshaw J. , Lai Eric C.
Published: March 2013

We recently reported that Drosophila Insensitive (Insv) promotes sensory organ development and has activity as a nuclear corepressor for the Notch transcription factor Suppressor of Hairless [Su(H)]. Insv lacks domains of known biochemical function but contains a single BEN domain (i.e., a “BEN-solo” protein). Our chromatin immunoprecipitation (ChIP) sequencing (ChIP-seq) analysis confirmed binding of Insensitive to Su(H) target genes in the Enhancer of split gene complex [E(spl)-C]; however, de novo motif analysis revealed a novel site strongly enriched in Insv peaks (TCYAATHRGAA). We validate binding of endogenous Insv to genomic regions bearing such sites, whose associated genes are enriched for neural functions and are functionally repressed by Insv. Unexpectedly, we found that the Insv BEN domain binds specifically to this sequence motif and that Insv directly regulates transcription via this motif. We determined the crystal structure of the BEN–DNA target complex, revealing homodimeric binding of the BEN domain and extensive nucleotide contacts via α helices and a C-terminal loop. Point mutations in key DNA-contacting residues severely impair DNA binding in vitro and capacity for transcriptional regulation in vivo. We further demonstrate DNA-binding and repression activities by the mammalian neural BEN-solo protein BEND5. Altogether, we define novel DNA-binding activity in a conserved family of transcriptional repressors, opening a molecular window on this extensive gene family.