bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma treatment of ITO cathode to fabricate free electron selective layer in inverted polymer solar cells
Authors: Zhang Chunmei , Qi Lei , Chen Qiang , Lv Longfeng , Ning Yu , Hu Yufeng , Hou Yanbing , Teng Feng
Published: September 2014

With Ar plasma treatment of the indium tin oxide (ITO) cathode, we achieve efficient inverted bulk heterojunction solar cells based on poly(3-hexylthiophene):[6,6]-phenyl C61butyric acid methyl ester, which do not require electron selective layer.
Histone variants and lipid metabolism
Authors: Borghesan Michela , Mazzoccoli Gianluigi , Sheedfar Fareeba , Oben Jude , Pazienza Valerio , Vinciguerra Manlio
Published: September 2014

Within nucleosomes, canonical histones package the genome, but they can be opportunely replaced with histone variants. The incorporation of histone variants into the nucleosome is a chief cellular strategy to regulate transcription and cellular metabolism. In pathological terms, cellular steatosis is an abnormal accumulation of lipids, which reflects impairment in the turnover of triacylglycerols, affecting any organ but mainly the liver. The present review aims to summarize the experimental evidence for histone variant functions in lipid metabolism.
Plasticity of the actin cytoskeleton in response to extracellular matrix nanostructure and dimensionality
Authors: Starke Josefine , Wehrle-Haller Bernhard , Friedl Peter
Published: September 2014

Mobile cells discriminate and adapt to mechanosensory input from extracellular matrix (ECM) topographies to undergo actin-based polarization, shape change and migration. We tested ‘cell-intrinsic’ and adaptive components of actin-based cell migration in response to widely used in vitro collagen-based substrates, including a continuous 2D surface, discontinuous fibril-based surfaces (2.5D) and fibril-based 3D geometries. Migrating B16F1 mouse melanoma cells expressing GFP–actin developed striking diversity and adaptation of cytoskeletal organization and migration efficacy in response to collagen organization. 2D geometry enabled keratinocyte-like cell spreading and lamellipod-driven motility, with barrier-free movement averaging the directional vectors from one or several leading edges. 3D fibrillar collagen imposed spindle-shaped polarity with a single cylindrical actin-rich leading edge and terminal filopod-like protrusions generating a single force vector. As a mixed phenotype, 2.5D environments prompted a broad but fractalized leading lamella, with multiple terminal filopod-like protrusions engaged with collagen fibrils to generate an average directional vector from multiple, often divergent, interactions. The migratory population reached >90% of the cells with high speeds for 2D, but only 10–30% of the cells and a 3-fold lower speed range for 2.5D and 3D substrates, suggesting substrate continuity as a major determinant of efficient induction and maintenance of migration. These findings implicate substrate geometry as an important input for plasticity and adaptation of the actin cytoskeleton to cope with varying ECM topography and highlight striking preference of moving cells for 2D continuous-shaped over more complex-shaped discontinuous 2.5 and 3D substrate geometries.
Astrocytes and neuroinflammation in Alzheimer's disease
Authors: Phillips Emma C. , Croft Cara L. , Kurbatskaya Ksenia , O’Neill Michael J. , Hutton Michael L. , Hanger Diane P. , Garwood Claire J. , Noble Wendy
Published: September 2014

Increased production of amyloid β-peptide (Aβ) and altered processing of tau in Alzheimer's disease (AD) are associated with synaptic dysfunction, neuronal death and cognitive and behavioural deficits. Neuroinflammation is also a prominent feature of AD brain and considerable evidence indicates that inflammatory events play a significant role in modulating the progression of AD. The role of microglia in AD inflammation has long been acknowledged. Substantial evidence now demonstrates that astrocyte-mediated inflammatory responses also influence pathology development, synapse health and neurodegeneration in AD. Several anti-inflammatory therapies targeting astrocytes show significant benefit in models of disease, particularly with respect to tau-associated neurodegeneration. However, the effectiveness of these approaches is complex, since modulating inflammatory pathways often has opposing effects on the development of tau and amyloid pathology, and is dependent on the precise phenotype and activities of astrocytes in different cellular environments. An increased understanding of interactions between astrocytes and neurons under different conditions is required for the development of safe and effective astrocyte-based therapies for AD and related neurodegenerative diseases.
Sec14-like phosphatidylinositol-transfer proteins and diversification of phosphoinositide signalling outcomes
Authors: Tripathi Ashutosh , Nile Aaron H. , Bankaitis Vytas A.
Published: September 2014

The physiological functions of phosphatidylinositol (PtdIns)-transfer proteins (PITPs)/phosphatidylcholine (PtdCho)-transfer proteins are poorly characterized, even though these proteins are conserved throughout the eukaryotic kingdom. Much of the progress in elucidating PITP functions has come from exploitation of genetically tractable model organisms, but the mechanisms for how PITPs execute their biological activities remain unclear. Structural and molecular dynamics approaches are filling in the details for how these proteins actually work as molecules. In the present paper, we discuss our recent work with Sec14-like PITPs and describe how PITPs integrate diverse territories of the lipid metabolome with phosphoinositide signalling.
Mitochondrial dynamics in astrocytes
Authors: Stephen Terri-Leigh , Gupta-Agarwal Swati , Kittler Josef T.
Published: September 2014

Astrocytes exhibit cellular excitability through variations in their intracellular calcium (Ca2+) levels in response to synaptic activity. Astrocyte Ca2+ elevations can trigger the release of neuroactive substances that can modulate synaptic transmission and plasticity, hence promoting bidirectional communication with neurons. Intracellular Ca2+ dynamics can be regulated by several proteins located in the plasma membrane, within the cytosol and by intracellular organelles such as mitochondria. Spatial dynamics and strategic positioning of mitochondria are important for matching local energy provision and Ca2+ buffering requirements to the demands of neuronal signalling. Although relatively unresolved in astrocytes, further understanding the role of mitochondria in astrocytes may reveal more about the complex bidirectional relationship between astrocytes and neurons in health and disease. In the present review, we discuss some recent insights regarding mitochondrial function, transport and turnover in astrocytes and highlight some important questions that remain to be answered.
Principle of duality in phospholipids: regulators of membrane morphology and dynamics
Authors: Larijani Banafshé , Hamati Fadi , Kundu Aupola , Chung Gary C. , Domart Marie-Charlotte , Collinson Lucy , Poccia Dominic L.
Published: September 2014

To suggest and develop intelligent strategies to comprehend the regulation of organelle formation, a deeper mechanistic interpretation requires more than just the involvement of proteins. Our approaches link the formation of endomembranes with both signalling and membrane physical properties. Hitherto, membrane morphology, local physical structure and signalling have not been well integrated. Our studies derive from a cross-disciplinary approach undertaken to determine the molecular mechanisms of nuclear envelope assembly in echinoderm and mammalian cells. Our findings have led to the demonstration of a direct role for phosphoinositides and their derivatives in nuclear membrane formation. We have shown that phosphoinositides and their derivatives, as well as acting as second messengers, are modulators of membrane morphology, and their modifying enzymes regulate nuclear envelope formation. In addition, we have shown that echinoderm eggs can be exploited as a milieu to directly study the roles of phospholipids in maintaining organelle shape. The use of the echinoderm egg is a significant step forward in obtaining direct information about membrane physical properties in situ rather than using simpler models which do not provide a complete mechanistic insight into the role of phospholipids in membrane dynamics.
Discovering latent attributes for human action recognition in depth sequence
Authors: Su Yuting , Jia Pingping , Liu An‐An , Yang Zhaoxuan
Published: September 2014

A method for human action recognition in depth sequence by discovering latent attributes is proposed. Specifically, a latent attribute model to take advantage of the partwise and bodywise action attributes and their concurrence for action modelling is presented. This model can avoid the explicit definition of a completed action attribute set by designing a hidden layer as latent attributes. Moreover, the relationship between pairwise attributes can be adaptively learned in terms of the specific graphical structure without human intervention. Extensive experiments on two popular datasets and a new dataset TJU show the superiority of the proposed method over the state‐of‐the‐arts.
Content‐based image quality assessment using semantic information and luminance differences
Authors: Qi Huan , Jiao Shuhong , Lin Weisi , Tang Lin , Shen Weihe
Published: September 2014

A full‐reference image quality assessment (FR‐IQA) metric, with emphasis on semantic information changes in different image content areas, is presented. The changes on edge information, that can represent semantic information changes, are calculated based on the characteristics of different image content areas. Considering that edge changes cannot account for luminance changes while luminance changes does affect visual quality of images, the luminance changes are also incorporated into the design of the perceptual quality metric. Experimental results confirm that the proposed metric is consistent with human judgments of quality, and outperforms relevant state‐of‐the‐art metrics across various distortion types.
Improved orthogonal projection approach utilising interference covariance matrix reconstruction for adaptive beamforming
Authors: Yang Xiaopeng , Yan Lu , Sun Yuze , Zeng Tao
Published: September 2014

When the training snapshots are contaminated by the desired signal, the performance of the orthogonal projection (OP) approach degrades significantly. Therefore, an improved OP adaptive beamforming is proposed by reconstructing interference covariance matrix to eliminate the desired signal cancellation effect. In the proposed method, by integrating the Capon spatial spectrum over a region separated from the desired signal direction, the interference‐plus‐noise covariance matrix is reconstructed first to remove the desired signal component from the sample covariance matrix. Subsequently, the interference subspace is estimated by eigenvalue decomposition, and then the adaptive weight vector is calculated using the OP algorithm to eliminate the noise perturbation. Simulation results show that the performance of the proposed algorithm is almost the same as the optimum beamforming.
Digital foreground calibration of capacitor mismatch for SAR ADCs
Authors: Yeo In‐june , Kim Byoungho , Chu Myonglae , Lee Byung‐geun
Published: September 2014

A foreground digital self‐calibration technique that improves capacitor matching of a digital‐to‐analogue converter (DAC) employed in successive approximation register (SAR) analogue‐to‐digital converters (ADCs) is presented. By exploiting an antisymmetric behaviour of capacitor mismatch errors in SAR ADCs and the proposed DAC switching scheme, the calibration technique significantly reduces capacitor mismatch errors without resorting to extensive computation or dedicated circuits.
Cross‐sensitivity reduction of QCM humidity sensor using graphene oxide membrane as filter layer
Authors: Liu Bin , Chen Xiang‐dong , Li Ning , Li Xiao‐yu , Yao Yao
Published: September 2014

A new approach to greatly reduce the cross‐sensitivity of a quartz crystal microbalance (QCM) humidity sensor is proposed. A graphene oxide (GO) membrane, which acts as a filter layer, is added to the sensor structure. Since the GO membrane enables selective permeation of water molecules, the introduction of the GO filter membrane into the sensor structure greatly reduces the cross‐sensitivity of the humidity sensor to other gases.
Experimental circular phased array for generating OAM radio beams
Authors: Bai Q. , Tennant A. , Allen B.
Published: September 2014

A circular phased array antenna that can generate orbital angular momentum (OAM) radio beams in the 10 GHz band is described. The antenna consists of eight inset‐fed patch elements and a microstrip corporate feeding network. A full‐wave electromagnetic simulator is used to aid the antenna design and theoretical simulations are confirmed by measurements.
Continuous non‐contact vital sign monitoring in neonatal intensive care unit
Authors: Villarroel Mauricio , Guazzi Alessandro , Jorge João , Davis Sara , Watkinson Peter , Green Gabrielle , Shenvi Asha , McCormick Kenny , Tarassenko Lionel
Published: September 2014

Current technologies to allow continuous monitoring of vital signs in pre‐term infants in the hospital require adhesive electrodes or sensors to be in direct contact with the patient. These can cause stress, pain, and also damage the fragile skin of the infants. It has been established previously that the colour and volume changes in superficial blood vessels during the cardiac cycle can be measured using a digital video camera and ambient light, making it possible to obtain estimates of heart rate or breathing rate. Most of the papers in the literature on non‐contact vital sign monitoring report results on adult healthy human volunteers in controlled environments for short periods of time. The authors' current clinical study involves the continuous monitoring of pre‐term infants, for at least four consecutive days each, in the high‐dependency care area of the Neonatal Intensive Care Unit (NICU) at the John Radcliffe Hospital in Oxford. The authors have further developed their video‐based, non‐contact monitoring methods to obtain continuous estimates of heart rate, respiratory rate and oxygen saturation for infants nursed in incubators. In this Letter, it is shown that continuous estimates of these three parameters can be computed with an accuracy which is clinically useful. During stable sections with minimal infant motion, the mean absolute error between the camera‐derived estimates of heart rate and the reference value derived from the ECG is similar to the mean absolute error between the ECG‐derived value and the heart rate value from a pulse oximeter. Continuous non‐contact vital sign monitoring in the NICU using ambient light is feasible, and the authors have shown that clinically important events such as a bradycardia accompanied by a major desaturation can be identified with their algorithms for processing the video signal.
Design of a real-time two-color interferometer for MAST Upgrade
Authors: O’Gorman T. , Naylor G. , Scannell R. , Cunningham G. , Brunner K. J. , Martin R. , Croft D.
Published: September 2014

A single chord two-color CO2/HeNe (10.6/0.633 μm) heterodyne laser interferometer has been designed to measure the line integral electron density along the mid-plane of the MAST Upgrade tokamak, with a typical error of 1 × 1018 m−3 (∼2° phase error) at 4 MHz temporal resolution. To ensure this diagnostic system can be restored from any failures without stopping MAST Upgrade operations, it has been located outside of the machine area. The final design and initial testing of this system, including details of the optics, vibration isolation, and a novel phase detection scheme are discussed in this paper.
Invited Article: Characterization of background sources in space-based time-of-flight mass spectrometers
Authors: Gilbert J. A. , Gershman D. J. , Gloeckler G. , Lundgren R. A. , Zurbuchen T. H. , Orlando T. M. , McLain J. , von Steiger R.
Published: September 2014

For instruments that use time-of-flight techniques to measure space plasma, there are common sources of background signals that evidence themselves in the data. The background from these sources may increase the complexity of data analysis and reduce the signal-to-noise response of the instrument, thereby diminishing the science value or usefulness of the data. This paper reviews several sources of background commonly found in time-of-flight mass spectrometers and illustrates their effect in actual data using examples from ACE-SWICS and MESSENGER-FIPS. Sources include penetrating particles and radiation, UV photons, energy straggling and angular scattering, electron stimulated desorption of ions, ion-induced electron emission, accidental coincidence events, and noise signatures from instrument electronics. Data signatures of these sources are shown, as well as mitigation strategies and design considerations for future instruments.
Rotational relaxation in molecular hydrogen and deuterium: Theory versus acoustic experiments
Authors: Montero S. , Pérez-Ríos J.
Published: September 2014

An explicit formulation of the rotational relaxation time in terms of state-to-state rate coefficients associated to inelastic collisions is reported. The state-to-state rates needed for the detailed interpretation of relaxation in H2 and D2, including isotopic variant mixtures, have been calculated by solving the close-coupling Schrödinger equations using the H2–H2 potential energy surface by Diep and Johnson [J. Chem. Phys. 112, 4465 (2000)]. Relaxation related quantities (rotational effective cross section, bulk viscosity, relaxation time, and collision number) calculated from first principles agree reasonably well with acoustic absorption experimental data on H2 and D2 between 30 and 293 K. This result confirms at once the proposed formulation, and the validation of the H2–H2 potential energy surface employed, since no approximations have been introduced in the dynamics. Accordingly, the state-to-state rates derived from Diep and Johnson potential energy surface appear to be overestimated by up to 10% for H2, and up to 30% for D2 at T = 300 K, showing a better agreement at lower temperatures.
Relation between energetic and standard geodesic acoustic modes
Authors: Girardo Jean-Baptiste , Zarzoso David , Dumont Rémi , Garbet Xavier , Sarazin Yanick , Sharapov Sergei
Published: September 2014

Geodesic Acoustic Modes (GAMs) are electrostatic, axisymmetric modes which are non-linearly excited by turbulence. They can also be excited linearly by fast-particles; they are then called Energetic-particle-driven GAMs (EGAMs). Do GAMs and EGAMs belong to the same mode branch? Through a linear, analytical model, in which the fast particles are represented by a Maxwellian bump-on-tail distribution function, we find that the answer depends on several parameters. For low values of the safety factor q and for high values of the fast ion energy, the EGAM originates from the GAM. On the contrary, for high values of q and for low values of the fast ion energy, the GAM is not the mode which becomes unstable when fast particles are added: the EGAM then originates from a distinct mode, which is strongly damped in the absence of fast particles. The impact of other parameters is further explored: ratio of the ion temperature to the electron temperature, width of the fast particle distribution, mass and charge of the fast ions. The ratio between the EGAM and the GAM frequencies was found in experiments (DIII-D) and in non-linear numerical simulations (code GYSELA) to be close to 1/2: the present analytical study allows one to recover this ratio.
Ionic strength independence of charge distributions in solvation of biomolecules
Authors: Virtanen J. J. , Sosnick T. R. , Freed K. F.
Published: September 2014

Electrostatic forces enormously impact the structure, interactions, and function of biomolecules. We perform all-atom molecular dynamics simulations for 5 proteins and 5 RNAs to determine the dependence on ionic strength of the ion and water charge distributions surrounding the biomolecules, as well as the contributions of ions to the electrostatic free energy of interaction between the biomolecule and the surrounding salt solution (for a total of 40 different biomolecule/solvent combinations). Although water provides the dominant contribution to the charge density distribution and to the electrostatic potential even in 1M NaCl solutions, the contributions of water molecules and of ions to the total electrostatic interaction free energy with the solvated biomolecule are comparable. The electrostatic biomolecule/solvent interaction energies and the total charge distribution exhibit a remarkable insensitivity to salt concentrations over a huge range of salt concentrations (20 mM to 1M NaCl). The electrostatic potentials near the biomolecule's surface obtained from the MD simulations differ markedly, as expected, from the potentials predicted by continuum dielectric models, even though the total electrostatic interaction free energies are within 11% of each other.
Effect of cosolvent on protein stability: A theoretical investigation
Authors: Chalikian Tigran V.
Published: September 2014

We developed a statistical thermodynamic algorithm for analyzing solvent-induced folding/unfolding transitions of proteins. The energetics of protein transitions is governed by the interplay between the cavity formation contribution and the term reflecting direct solute-cosolvent interactions. The latter is viewed as an exchange reaction in which the binding of a cosolvent to a solute is accompanied by release of waters of hydration to the bulk. Our model clearly differentiates between the stoichiometric and non-stoichiometric interactions of solvent or co-solvent molecules with a solute. We analyzed the urea- and glycine betaine (GB)-induced conformational transitions of model proteins of varying size which are geometrically approximated by a sphere in their native state and a spherocylinder in their unfolded state. The free energy of cavity formation and its changes accompanying protein transitions were computed based on the concepts of scaled particle theory. The free energy of direct solute-cosolvent interactions were analyzed using empirical parameters previously determined for urea and GB interactions with low molecular weight model compounds. Our computations correctly capture the mode of action of urea and GB and yield realistic numbers for (∂ΔG°/∂a3)T,P which are related to the m-values of protein denaturation. Urea is characterized by negative values of (∂ΔG°/∂a3)T,P within the entire range of urea concentrations analyzed. At concentrations below ∼1 M, GB exhibits positive values of (∂ΔG°/∂a3)T,P which turn positive at higher GB concentrations. The balance between the thermodynamic contributions of cavity formation and direct solute-cosolvent interactions that, ultimately, defines the mode of cosolvent action is extremely subtle. A 20% increase or decrease in the equilibrium constant for solute-cosolvent binding may change the sign of (∂ΔG°/∂a3)T,P thereby altering the mode of cosolvent action (stabilizing to destabilizing or vice versa).
A general time-dependent route to Resonance-Raman spectroscopy including Franck-Condon, Herzberg-Teller and Duschinsky effects
Authors: Baiardi Alberto , Bloino Julien , Barone Vincenzo
Published: September 2014

We present a new formulation of the time-dependent theory of Resonance-Raman spectroscopy (TD-RR). Particular attention has been devoted to the generality of the framework and to the possibility of including different effects (Duschinsky mixing, Herzberg-Teller contributions). Furthermore, the effects of different harmonic models for the intermediate electronic state are also investigated. Thanks to the implementation of the TD-RR procedure within a general-purpose quantum-chemistry program, both solvation and leading anharmonicity effects have been included in an effective way. The reliability and stability of our TD-RR implementation are validated against our previously proposed and well-tested time-independent procedure. Practical applications are illustrated with some closed- and open-shell medium-size molecules (anthracene, phenoxyl radical, benzyl radical) and the simulated spectra are compared to the experimental results. More complex and larger systems, not limited to organic compounds, can be also studied, as shown for the case of Tris(bipyridine)ruthenium(II) chloride.
Reorientation of the “free OH” group in the top-most layer of air/water interface of sodium fluoride aqueous solution probed with sum-frequency generation vibrational spectroscopy
Authors: Feng Ran-Ran , Guo Yuan , Wang Hong-Fei
Published: September 2014

Many experimental and theoretical studies have established the specific anion, as well as cation, effects on the hydrogen-bond structures at the air/water interface of electrolyte solutions. However, the ion effects on the top-most layer of the air/water interface, which is signified by the non-hydrogen-bonded so-called “free OH” group, have not been explicitly discussed or studied. In this report, we present the measurement of changes of the orientational angle of the “free OH” group at the air/water interface of the sodium fluoride (NaF) solutions at different concentrations using the interface selective sum-frequency generation vibrational spectroscopy (SFG-VS) in the ssp and ppp polarizations. The polarization dependent SFG-VS results show that the average tilt angle of the “free OH” changes from about 36.6° ± 0.5° to 44.1° ± 0.6° as the NaF concentration increases from 0 to 0.94 M (nearly saturated). Such tilt angle change is around the axis of the other O-H group of the same water molecule at the top-most layer at the air/water interface that is hydrogen-bonded to the water molecules below the top-most layer. These results provide quantitative molecular details of the ion effects of the NaF salt on the structure of the water molecules at the top-most layer of the air/water interface, even though both the Na+ cation and the F− anion are believed to be among the most excluded ions from the air/water interface.
Wave packet and statistical quantum calculations for the He + NeH+ → HeH+ + Ne reaction on the ground electronic state
Authors: Koner Debasish , Barrios Lizandra , González-Lezana Tomás , Panda Aditya N.
Published: September 2014

A real wave packet based time-dependent method and a statistical quantum method have been used to study the He + NeH+ (v, j) reaction with the reactant in various ro-vibrational states, on a recently calculated ab initioground state potential energy surface. Both the wave packet and statistical quantum calculations were carried out within the centrifugal sudden approximation as well as using the exact Hamiltonian. Quantum reaction probabilities exhibit dense oscillatory pattern for smaller total angular momentum values, which is a signature of resonances in a complex forming mechanism for the title reaction. Significant differences, found between exact and approximate quantum reaction cross sections, highlight the importance of inclusion of Coriolis coupling in the calculations. Statistical results are in fairly good agreement with the exact quantum results, for ground ro-vibrational states of the reactant. Vibrational excitation greatly enhances the reaction cross sections, whereas rotational excitation has relatively small effect on the reaction. The nature of the reaction cross section curves is dependent on the initial vibrational state of the reactant and is typical of a late barrier type potential energy profile.
Constrained large-eddy simulation of laminar-turbulent transition in channel flow
Authors: Zhao Yaomin , Xia Zhenhua , Shi Yipeng , Xiao Zuoli , Chen Shiyi
Published: September 2014

A constrained large-eddy simulation (CLES) of a laminar-turbulent transition in a temporally developing channel flow is performed. First, we confirm the capability of CLES to simulate this transition problem using the a priori Reynolds stress estimated from a direct numerical simulation. Based on the analysis of the Reynolds stress during the transition process, an intermittency factor is introduced in the Reynolds-averaged Navier–Stokes equation (RANS) model to account for the transition property. Two simple approaches are used to construct the intermittency factor. One is based on the shape factor, and the other is based on the coefficients of Smagorinsky models. The CLES results using the intermittency modified RANS model can accurately predict the onset of the transition and the basic transition process, in a manner similar to a large eddy simulation with dynamics Smagorinsky model (LES-DSM). Meanwhile, CLES preserves its advantage over LES-DSM in the turbulent state. The present work illustrates that CLES can be used to simulate transitional flows.
Fabrication and integration of microprism mirrors for high-speed three-dimensional measurement in inertial microfluidic system
Authors: Koh Joonyoung , Kim Jihye , Shin Jung H. , Lee Wonhee
Published: September 2014

Inertial microfluidics utilizes fluid inertia from high flow velocity to manipulate particles and fluids in 3D. Acquiring a 3D information of particle positions and complex flow patterns within microfluidic devices requires 3D imaging techniques such as confocal microscopy, which are often expensive and slow. Here, we report on a prism-mirror-embedded microfluidic device that allows simultaneous imaging of the top and side view of the microchannel for a high-speed, low-cost 3D imaging. The microprism mirrors are fabricated and integrated into a microfluidic system using conventional microfabrication techniques including wet etch and soft lithography. This inexpensive high quality prism mirror provides a highly reflective, smooth mirror surface with precise 45° reflection angle, enabling 3D measurement of inertial migration of microparticles in a rectangular channel at speeds in excess of 10 000 frame/s.
Mechanism of phase control in a klystron-like relativistic backward wave oscillator by an input signal
Authors: Xiao Renzhen , Song Zhimin , Deng Yuqun , Chen Changhua
Published: September 2014

Theoretical analyses and particle-in-cell (PIC) simulations are carried out to understand the mechanism of microwave phase control realized by the external RF signal in a klystron-like relativistic backward wave oscillator (RBWO). Theoretical calculations show that a modulated electron beam can lead the microwave field with an arbitrary initial phase to the same equilibrium phase, which is determined by the phase factor of the modulated current, and the difference between them is fixed. Furthermore, PIC simulations demonstrate that the phase of input signal has a close relation to that of modulated current, which initiates the phase of the irregularly microwave during the build-up of oscillation. Since the microwave field is weak during the early time of starting oscillation, it is easy to be induced, and a small input signal is sufficient to control the phase of output microwave. For the klystron-like RBWO with two pre-modulation cavities and a reentrant input cavity, an input signal with 100 kW power and 4.21 GHz frequency can control the phase of 5 GW output microwave with relative phase difference less than 6% when the diode voltage is 760 kV, and beam current is 9.8 kA, corresponding to a power ratio of output microwave to input signal of 47 dB.
Dielectric-dependent screened Hartree–Fock exchange potential and Slater-formula with Coulomb-hole interaction for energy band structure calculations
Authors: Shimazaki Tomomi , Nakajima Takahito
Published: September 2014

We previously reported a screened Hartree–Fock (HF) exchange potential for energy band structure calculations [T. Shimazaki and Y. Asai, J. Chem. Phys. 130, 164702 (2009); T. Shimazaki and Y. Asai, J. Chem. Phys. 132, 224105 (2010)]. In this paper, we discuss the Coulomb-hole (COH) interaction and screened Slater-formula and determine the energy band diagrams of several semiconductors, such as diamond, silicon, AlAs, AlP, GaAs, GaP, and InP, based on the screened HF exchange potential and Slater-formula with COH interaction, to demonstrate the adequacy of those theoretical concepts. The screened HF exchange potential and Slater-formula are derived from a simplified dielectric function and, therefore, include the dielectric constant in their expressions. We also present a self-consistent calculation technique to automatically determine the dielectric constant, which is incorporated into each self-consistent field step.
Internal wave energy radiated from a turbulent mixed layer
Authors: Munroe James R. , Sutherland Bruce R.
Published: September 2014

We examine mixed-layer deepening and the generation of internal waves in stratified fluid resulting from turbulence that develops in response to an applied surface stress. In laboratory experiments the stress is applied over the breadth of a finite-length tank by a moving roughened conveyor belt. The turbulence in the shear layer is characterized using particle image velocimetry to measure the kinetic energy density. The internal waves are measured using synthetic schlieren to determine their amplitudes, frequencies, and energy density. We also perform fully nonlinear numerical simulations restricted to two dimensions but in a horizontally periodic domain. These clearly demonstrate that internal waves are generated by transient eddies at the integral length scale of turbulence and which translate with the background shear along the base of the mixed layer. In both experiments and simulations we find that the energy density of the generated waves is 1%–3% of the turbulent kinetic energy density of the turbulent layer.
Biomechanical properties of red blood cells in health and disease towards microfluidics
Authors: Tomaiuolo Giovanna
Published: September 2014

Red blood cells (RBCs) possess a unique capacity for undergoing cellular deformation to navigate across various human microcirculation vessels, enabling them to pass through capillaries that are smaller than their diameter and to carry out their role as gas carriers between blood and tissues. Since there is growing evidence that red blood cell deformability is impaired in some pathological conditions, measurement of RBC deformability has been the focus of numerous studies over the past decades. Nevertheless, reports on healthy and pathological RBCs are currently limited and, in many cases, are not expressed in terms of well-defined cell membrane parameters such as elasticity and viscosity. Hence, it is often difficult to integrate these results into the basic understanding of RBC behaviour, as well as into clinical applications. The aim of this review is to summarize currently available reports on RBC deformability and to highlight its association with various human diseases such as hereditary disorders (e.g., spherocytosis, elliptocytosis, ovalocytosis, and stomatocytosis), metabolic disorders (e.g., diabetes, hypercholesterolemia, obesity), adenosine triphosphate-induced membrane changes, oxidative stress, and paroxysmal nocturnal hemoglobinuria. Microfluidic techniques have been identified as the key to develop state-of-the-art dynamic experimental models for elucidating the significance of RBC membrane alterations in pathological conditions and the role that such alterations play in the microvasculature flow dynamics.
Solute embrittlement of SiC
Authors: Enrique Raúl A. , Van der Ven Anton
Published: September 2014

The energies and stresses associated with the decohesion of β-SiC in the presence of mobile Pd and Ag impurities are studied from first principles. Density functional theory calculations are parameterized with a generalized cohesive zone model and are analyzed within a thermodynamic framework that accounts for realistic boundary conditions in the presence of mobile impurities. We find that Pd impurities will embrittle SiC when Pd is in equilibrium with metallic Pd precipitates. Our thermodynamic analysis predicts that Pd embrittles SiC by substantially reducing the maximum stress of decohesion as a result of a phase transition between decohering planes involving an influx of Pd atoms. The methods presented in this work can be applied to study the thermodynamics of decohesion of SiC in other aggressive environments containing oxygen and water, for example, and yield environment dependent cohesive zone models for use in continuum approaches to study crack propagation and fracture.
Characterization of the nitrogen split interstitial defect in wurtzite aluminum nitride using density functional theory
Authors: Szállás A. , Szász K. , Trinh X. T. , Son N. T. , Janzén E. , Gali A.
Published: September 2014

We carried out Heyd-Scuseria-Ernzerhof hybrid density functional theory plane wave supercell calculations in wurtzite aluminum nitride in order to characterize the geometry, formation energies, transition levels, and hyperfine tensors of the nitrogen split interstitial defect. The calculated hyperfine tensors may provide useful fingerprint of this defect for electron paramagnetic resonance measurement.
(111) Orientation preferred L1 FePtB patterned by block copolymer templating
Authors: Su Hao , Schwarm Samuel C. , Douglas Robert L. , Montgomery Angelique , Owen Allen G. , Gupta Subhadra
Published: September 2014

The (111) orientation preferred L10 FePtB has been obtained by post-deposition annealing sputtered FeB/Pt multilayers on thermally oxidized silicon substrates. Block copolymer templating was employed to pattern FeBPt film. A matrix study of etch time and etch angle showed that ion-milling at 75° for 3 min yielded the highest coercivity. Reannealing after patterning process was found to improve the crystalline structure and coercivity significantly. These results suggested (111) orientation preferred L10 FePt patterned by block copolymer templating may be promising for tilted media and bit patterned media.
Substrate effect on phonon confinement in TiO2 nanoparticles for thermal sensing application
Authors: Mishra Ashish Kumar , Huang Liping
Published: September 2014

The great potential of anatase TiO2 nanoparticles (NPs) for high temperature applications is limited by the agglomeration, grain growth, and phase transformation into rutile. In this regard, we have decorated TiO2 NPs over the surface of Santa Barbara Amorphous-15 (SBA15) and studied the substrate effect on the thermal stability of anatase TiO2 NPs in terms of the grain growth and the phase transformation. Here, we reported the ultrafast grain growth of anatase TiO2 NPs in TiO2-SBA15 nanocomposite in response to short time thermal exposure and the resulting phonon confinement effect for high temperature thermal sensing application.
Generating mobile fluidic traps for selective three-dimensional transport of microobjects
Authors: Huang Tian-Yun , Qiu Famin , Tung Hsi-Wen , Chen Xue-Bo , Nelson Bradley J. , Sakar Mahmut Selman
Published: September 2014

We demonstrate noncontact transport of microscale objects in liquid environments using untethered, magnetic microrobots. The flow and vortices generated by the rotating microrobot are efficient for selective and gentle trapping, stable transport, and targeted delivery of microscale cargo. The motion of the microrobots can be precisely controlled even at very low frequencies using an advanced magnetic control signal. The design and control methodology presented here can be followed to develop microrobots utilizing the generated fluid flows and performing a variety of biomedical manipulation tasks.
Atmospheric air diffuse array-needles dielectric barrier discharge excited by positive, negative, and bipolar nanosecond pulses in large electrode gap
Authors: Zhang Li , Yang De-zheng , Wang Wen-chun , Liu Zhi-jie , Wang Sen , Jiang Peng-chao , Zhang Shuai
Published: September 2014

In this paper, positive, negative, and bipolar nanosecond pulses are employed to generate stable and diffuse discharge plasma using array needles-plate electrode configuration at atmospheric pressure. A comparison study of discharge images, electrical characteristics, optical emission spectra, and plasma vibrational temperature and rotational temperatures in three pulsed polarity discharges is carried on under different discharge conditions. It is found that bipolar pulse is beneficial to the excitation of diffuse dielectric barrier discharge, which can generate a room temperature plasma with more homogeneous and higher discharge intensity compared with unipolar discharges. Under the condition of 6 mm electrode gap distance, 26 kV pulse peak voltage, and 150 Hz pulse repetition rate, the emission intensity of N2 (C3Πu → B3Πg) of the bipolar pulsed discharge is 4 times higher than the unipolar discharge (both positive and negative), while the plasma gas temperature is kept at 300 K, which is about 10–20 K lower than the unipolar discharge plasma.
Semianalytical quantum model for graphene field-effect transistors
Authors: Pugnaghi Claudio , Grassi Roberto , Gnudi Antonio , Di Lecce Valerio , Gnani Elena , Reggiani Susanna , Baccarani Giorgio
Published: September 2014

We develop a semianalytical model for monolayer graphene field-effect transistors in the ballistic limit. Two types of devices are considered: in the first device, the source and drain regions are doped by charge transfer with Schottky contacts, while, in the second device, the source and drain regions are doped electrostatically by a back gate. The model captures two important effects that influence the operation of both devices: (i) the finite density of states in the source and drain regions, which limits the number of states available for transport and can be responsible for negative output differential resistance effects, and (ii) quantum tunneling across the potential steps at the source-channel and drain-channel interfaces. By comparison with a self-consistent non-equilibrium Green's function solver, we show that our model provides very accurate results for both types of devices, in the bias region of quasi-saturation as well as in that of negative differential resistance.
Anisotropic magnetocaloric effect in antiferromagnetic systems: Application to EuTiO3
Authors: Alho B. P. , Carvalho A. Magnus G. , von Ranke P. J.
Published: September 2014

In this work, we theoretically predicted an anisotropic magnetocaloric effect of the same order of magnitude of the usual magnetocaloric effect for antiferromagnetic systems. The anisotropic magnetic properties come from the anti-parallel alignment of the magnetic sites and can be optimized depending on the magnetic field change. This result highlights the applicability of antiferromagnetic compounds as refrigerants based on the anisotropic magnetocaloric effect. For this purpose, we considered a Hamiltonian model, including the exchange and Zeeman interactions in a two sublattices framework. It is worth noting that no anisotropy is explicitly included on the Hamiltonian model, although the system presents an anisotropic behavior. The calculations were applied to the G-type antiferromagnetic compound EuTiO3.
Theoretical study on electronic properties of MoS2 antidot lattices
Authors: Shao Li , Chen Guangde , Ye Honggang , Wu Yelong , Niu Haibo , Zhu Youzhang
Published: September 2014

Motivated by the state of the art method for etching hexagonal array holes in molybdenum disulfide (MoS2), the electronic properties of MoS2 antidot lattices (MoS2ALs) with zigzag edge were studied with first-principles calculations. Monolayer MoS2ALs are semiconducting and the band gaps converge to constant values as the supercell area increases, which can be attributed to the edge effect. Multilayer MoS2ALs and chemical adsorbed MoS2ALs by F atoms show metallic behavior, while the structure adsorbed with H atoms remains to be semiconducting with a tiny bandgap. Our results show that forming periodically repeating structures in MoS2 can develop a promising technique for engineering nano materials and offer new opportunities for designing MoS2-based nanoscale electronic devices and chemical sensors.
High strain in polycrystalline Ni48.8Mn31.4Ga19.8 Heusler alloys under overlapped static and oscillating magnetic fields
Authors: Montanher D. Z. , Pereira J. R. D. , Cótica L. F. , Gotardo R. A. M. , Viana D. S. F. , Garcia D. , Eiras J. A. , Santos I. A.
Published: September 2014

Martensitic polycrystalline Ni48.8Mn31.4Ga19.8 Heusler alloys, with a stacking period of 14 atomic planes at room temperature, were innovatively processed by combining high-energy ball milling and powder metallurgy. Bulk samples were mechanically coupled to a piezoelectric material in a parallel configuration, and the mechanical deformation of the studied system due to the twin's variant motion was investigated under overlapped static and oscillating magnetic fields. A reversible and high mechanical deformation is observed when the frequency of the oscillating magnetic field is tuned with the natural vibration frequency of this system. In this condition, a linear deformation as a function of the static magnetic field amplitude occurs in the ±4 kOe range, and a mechanical deformation of 2% at 10 kOe is observed.
Tailoring room temperature photoluminescence of antireflective silicon nanofacets
Authors: Basu Tanmoy , Kumar M. , Kanjilal A. , Ghatak J. , Sahoo P. K. , Som T.
Published: September 2014

In this paper, a fluence-dependent antireflection performance is presented from ion-beam fabricated nanofaceted-Si surfaces. It is also demonstrated that these nanofacets are capable of producing room temperature ultra-violet and blue photoluminescence which can be attributed to inter-band transitions of the localized excitonic states of different Si-O bonds at the Si/SiOx interface. Time-resolved photoluminescence measurements further confirm defect-induced radiative emission from the surface of silicon nanofacets. It is observed that the spectral characteristics remain unchanged, except an enhancement in the photoluminescence intensity with increasing ion-fluence. The increase in photoluminescence intensity by orders of magnitude stronger than that of a planar Si substrate is due to higher absorption of incident photons by nanofaceted structures.
Nanoantennas for nanowire photovoltaics
Authors: Alisafaee Hossein , Fiddy Michael A.
Published: September 2014

We consider the use of plasmonic nanoantenna elements, hemispherical and cylindrical, for application in semiconductor nanowire (NW) vertical arrays. Using Mie theory and a finite element method, scattering and absorption efficiencies are obtained for the desired enhancement of interaction with light in the NWs. We find an optimal mixture of nanoantennae for efficient scattering of solar spectrum in the NW array. Spectral radiation patterns of scattered light are computed, and, for representing the total response of the nanoantenna-equipped NWs to the solar AM1.5G spectrum, the weighted average of scattering patterns for unpolarized normal incidence is obtained showing an advantageous overall directivity toward the NWs.