bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of surface charges and traps in gallium nitride/aluminium gallium nitride/gallium nitride high‐voltage transistors via measurements and technology computer‐aided design simulations of transfer characteristics of metal–insulator–semiconductor field‐effect transistors and high‐electron‐mobility transistors
Authors: Longobardi Giorgia , Udrea Florin , Sque Stephen , Croon Jeroen , Hurkx Fred , Šonský Jan
Published: December 2015

This study presents a detailed analysis of the Plasma‐enhanced chemical vapour deposition (PECVD) silicon‐nitride/semiconductor interface of gallium nitride (GaN) transistors through the study of the transfer characteristics of a large‐gate‐area metal‐insulator‐semiconductor field‐effect transistor (MISFET). Id–Vg measurements were performed on several MISFETs across the wafer and for all of them the authors observed strong hysteresis between forward and reverse sweeps and a double kink. These features indicate the presence of traps beneath the gate electrode. Neither the hysteresis nor the kinks were seen in the measured high‐electron‐mobility transistor (HEMT) characteristics suggesting that the passivation/semiconductor interface is electrically responsible for them. The transfer characteristics of the MISFET have been reproduced using a technology computer‐aided design (TCAD) deck that includes fixed charges and donor traps at the passivation/semiconductor interface. The impact of these charges on the Id–Vg and their influence on the formation of a surface‐inversion layer is here explained through extensive TCAD simulations. This study has also been extended to different temperatures between 35 and 75°C to investigate the change in the transfer characteristics at elevated temperatures. It is shown that the hysteresis observed between forward and reverse sweeps and the transconductance decrease significantly with increasing temperature.
Thermodynamic and kinetic anisotropies in octane thin films
Authors: Haji-Akbari Amir , Debenedetti Pablo G.
Published: December 2015

Confinement breaks the translational symmetry of materials, making all thermodynamic and kinetic quantities functions of position. Such symmetry breaking can be used to obtain configurations that are not otherwise accessible in the bulk. Here, we use computer simulations to explore the effect of substrate-liquid interactions on thermodynamic and kinetic anisotropies induced by a solid substrate. We consider n-octane nano-films that are in contact with substrates with varying degrees of attraction, parameterized by an interaction parameter ϵS. Complete freezing of octane nano-films is observed at low temperatures, irrespective of ϵS, while at intermediate temperatures, a frozen monolayer emerges at solid-liquid and vapor-liquid interfaces. By carefully inspecting the profiles of translational and orientational relaxation times, we confirm that the translational and orientational degrees of freedom are decoupled at these frozen monolayers. At sufficiently high temperatures, however, free interfaces and solid-liquid interfaces close to loose (low-ϵS) substrates undergo “pre-freezing,” characterized by mild peaks in several thermodynamic quantities. Two distinct dynamic regimes are observed at solid-liquid interfaces. The dynamics is accelerated in the vicinity of loose substrates, while sticky (high-ϵS) substrates decelerate dynamics, sometimes by as much as two orders of magnitude. These two distinct dynamical regimes have been previously reported by Haji-Akbari and Debenedetti [J. Chem. Phys. 141, 024506 (2014)] for a model atomic glass-forming liquid. We also confirm the existence of two correlations—proposed in the above-mentioned work—in solid-liquid subsurface regions of octane thin films, i.e., a correlation between atomic density and normal stress, and between atomic translational relaxation time and lateral stress. Finally, we inspect the ability of different regions of an octane film to explore the potential energy landscape by performing inherent structure calculations, and observe no noticeable difference between the free surface and the bulk in efficiently exploring the potential energy landscape. This is unlike the films of model atomic glass formers that tend to sample their respective landscape more efficiently at free surfaces. We discuss the implications of this finding to the ability of octane—and other n-alkanes—to form ultrastable glasses.
Three distinct modes in a surface micro-discharge in atmospheric pressure He + N2 mixtures
Authors: Li Dong , Liu Dingxin , He Tongtong , Li Qiaosong , Wang Xiaohua , Kong Michael G.
Published: December 2015

A surface micro-discharge in atmospheric pressure He + N2 mixtures is studied in this paper with an emphasis on the discharge modes. With the N2 admixture increasing from 0.1% to 20%, the discharge evolves from a spatially diffuse mode to a filamentary mode during positive half-cycles of the applied voltage. However during the negative half-cycles, an additional patterned mode emerges between the diffuse and the filamentary modes, which has not been reported before to exist in surface micro-discharges. In the diffuse and patterned modes, the plasmas cover almost the entirety of the mesh area during one cycle after plasma ignition in all mesh elements, and the discharge power increases linearly with the applied voltage. In contrast, plasma coverage of the mesh area is only partial in the filamentary mode and the plasma is more unstable with the discharge power increasing exponentially with the applied voltage. As the surface micro-discharge evolves through the three modes, the density of excited species changes significantly, for instance, the density of N2+(B) drops by ∼20-fold from [N2] = 0.2% to 20%. The N2+(B) is predicted to be generated mainly through successive processes of Penning ionization by helium metastables and electron-impact excitation of N2+(X), the latter is most responsible for the density decrease of N2+(B) because much more N2+(X) is converted to N4+(X) as the increase of N2 fraction. Also, the electron density and electron temperature decrease with the discharge mode transition.
Path statistics, memory, and coarse-graining of continuous-time random walks on networks
Authors: Manhart Michael , Kion-Crosby Willow , Morozov Alexandre V.
Published: December 2015

Continuous-time random walks (CTRWs) on discrete state spaces, ranging from regular lattices to complex networks, are ubiquitous across physics, chemistry, and biology. Models with coarse-grained states (for example, those employed in studies of molecular kinetics) or spatial disorder can give rise to memory and non-exponential distributions of waiting times and first-passage statistics. However, existing methods for analyzing CTRWs on complex energy landscapes do not address these effects. Here we use statistical mechanics of the nonequilibrium path ensemble to characterize first-passage CTRWs on networks with arbitrary connectivity, energy landscape, and waiting time distributions. Our approach can be applied to calculating higher moments (beyond the mean) of path length, time, and action, as well as statistics of any conservative or non-conservative force along a path. For homogeneous networks, we derive exact relations between length and time moments, quantifying the validity of approximating a continuous-time process with its discrete-time projection. For more general models, we obtain recursion relations, reminiscent of transfer matrix and exact enumeration techniques, to efficiently calculate path statistics numerically. We have implemented our algorithm in PathMAN (Path Matrix Algorithm for Networks), a Python script that users can apply to their model of choice. We demonstrate the algorithm on a few representative examples which underscore the importance of non-exponential distributions, memory, and coarse-graining in CTRWs.
The Burghelea-Friedlander-Kappeler–gluing formula for zeta-determinants on a warped product manifold and a product manifold
Authors: Kirsten Klaus , Lee Yoonweon
Published: December 2015

The Burghelea-Friedlander-Kappeler (BFK)-gluing formula for the regularized zeta-determinants of Laplacians contains a constant which is expressed by the constant term in the asymptotic expansion of the regularized zeta-determinants of a one-parameter family of the Dirichlet-to-Neumann operators. When the dimension of a cutting hypersurface is odd or the metric is a product one near a cutting hypersurface, this constant is well known. In this paper, we discuss this constant in two cases: one is when a warped product metric is given near a cutting hypersurface, and the other is when a manifold is a product manifold. Especially in the first case, we use the result of Fucci and Kirsten [Commun. Math. Phys. 317, 635-665 (2013)] in which the regularized zeta-determinant of the Laplacian defined on a warped product manifold is computed.
Scanning tunneling potentiometry implemented into a multi-tip setup by software
Authors: Lüpke F. , Korte S. , Cherepanov V. , Voigtländer B.
Published: December 2015

We present a multi-tip scanning tunneling potentiometry technique that can be implemented into existing multi-tip scanning tunneling microscopes without installation of additional hardware. The resulting setup allows flexible in situ contacting of samples under UHV conditions and subsequent measurement of the sample topography and local electric potential with resolution down to Å and μV, respectively. The performance of the potentiometry feedback is demonstrated by thermovoltage measurements on the Ag/Si(111)−(3×3)R30∘ surface by resolving a standing wave pattern. Subsequently, the ability to map the local transport field as a result of a lateral current through the sample surface is shown on Ag/Si(111)−(3×3)R30∘ and Si(111) − (7 × 7) surfaces.
Effective reaction rates for diffusion-limited reaction cycles
Authors: Nałęcz-Jawecki Paweł , Szymańska Paulina , Kochańczyk Marek , Miękisz Jacek , Lipniacki Tomasz
Published: December 2015

Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme–substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%.
Combining molecular dynamics with mesoscopic Green’s function reaction dynamics simulations
Authors: Vijaykumar Adithya , Bolhuis Peter G. , ten Wolde Pieter Rein
Published: December 2015

In many reaction-diffusion processes, ranging from biochemical networks, catalysis, to complex self-assembly, the spatial distribution of the reactants and the stochastic character of their interactions are crucial for the macroscopic behavior. The recently developed mesoscopic Green’s Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. We propose a novel approach that combines GFRD for simulating the system at the mesoscopic scale where particles are far apart, with a microscopic technique such as Langevin dynamics or Molecular Dynamics (MD), for simulating the system at the microscopic scale where reactants are in close proximity. This scheme defines the regions where the particles are close together and simulated with high microscopic resolution and those where they are far apart and simulated with lower mesoscopic resolution, adaptively on the fly. The new multi-scale scheme, called MD-GFRD, is generic and can be used to efficiently simulate reaction-diffusion systems at the particle level.
Analysis of turbulent bending moments in tidal current boundary layers
Authors: Alexander Spencer R. , Hamlington Peter E.
Published: December 2015

As ocean current turbines move from the design stage into production and installation, a better understanding of localized loading is required in order to more accurately predict turbine performance and durability. In this study, large eddy simulations (LES) of tidal boundary layers without turbines are used to measure the turbulent bending moments that would be experienced by an ocean current turbine placed in a tidal channel. The LES model captures turbulence due to winds, waves, thermal convection, and tides, thereby providing a high degree of physical realism, and bending moments are calculated for an idealized infinitely thin circular rotor disc. Probability density functions of bending moments are calculated and detailed statistical measures of the turbulent environment are also examined, including vertical profiles of Reynolds stresses, two-point velocity correlations, and velocity structure functions. The simulations show that waves and tidal velocity have the largest impacts on the strength of bending moments, while boundary layer stability and wind speeds have only minimal impacts. It is shown that either transverse velocity structure functions or two-point transverse velocity spatial correlations can be used to predict and understand turbulent bending moments in tidal channels.
Techno-economic analysis and performance assessment of standalone photovoltaic/wind/hybrid power system in Lakshadweep islands of India
Authors: Bhakta S. , Mukherjee V. , Shaw Binod
Published: December 2015

The aim of this paper is to present the techno-economic analysis and performance assessment of standalone photovoltaic (PV)/wind/hybrid energy system based on the simulation model for Lakshadweep islands of India where the islands' inhabitant depends on the use of power generation from diesel generator. In the present work, four Lakshadweep islands (namely, Andrott, Kavaratti, Kiltan, and Minicoy) are considered. The optimized system parameters are obtained from the monthly average solar radiation data, temperature data, and wind speed data for the three proposed renewable energy systems based on the assumed typical summer and winter load profiles. Based on an electrical performance of these three systems, the monthly average electrical power production, monthly average excess electrical production, monthly average unmet electrical load, monthly average converter output, and battery state of charge along with available battery input power over the year are detailed, analyzed, and compared. The techno-economic analysis is also performed among the systems to obtain the cost of energy (COE). The minimum COE for standalone PV-wind hybrid system in comparison with standalone PV or wind system is found to be $0.413 for Andrott island with 1 kW PV array, 1 kW wind turbine, eight numbers of battery, and 1 kW converter, while the COE is found to be $0.426 with 1.2 kW PV array, 1 kW wind turbine, eight numbers of battery, and 1 kW converter for Kavaratti, Kiltan, and Minicoy islands. Also, based on net present cost, it is shown that standalone PV-wind hybrid system is more economical as compared to either standalone PV or wind system.
Reduction by symmetries in singular quantum-mechanical problems: General scheme and application to Aharonov-Bohm model
Authors: Smirnov A. G.
Published: December 2015

We develop a general technique for finding self-adjoint extensions of a symmetric operator that respects a given set of its symmetries. Problems of this type naturally arise when considering two- and three-dimensional Schrödinger operators with singular potentials. The approach is based on constructing a unitary transformation diagonalizing the symmetries and reducing the initial operator to the direct integral of a suitable family of partial operators. We prove that symmetry preserving self-adjoint extensions of the initial operator are in a one-to-one correspondence with measurable families of self-adjoint extensions of partial operators obtained by reduction. The general scheme is applied to the three-dimensional Aharonov-Bohm Hamiltonian describing the electron in the magnetic field of an infinitely thin solenoid. We construct all self-adjoint extensions of this Hamiltonian, invariant under translations along the solenoid and rotations around it, and explicitly find their eigenfunction expansions.
Exact solution to the Schrödinger’s equation with pseudo-Gaussian potential
Authors: Iacob Felix , Lute Marina
Published: December 2015

We consider the radial Schrödinger equation with the pseudo-Gaussian potential. By making an ansatz to the solution of the eigenvalue equation for the associate Hamiltonian, we arrive at the general exact eigenfunction. The values of energy levels for the bound states are calculated along with their corresponding normalized wave-functions. The case of positive energy levels, known as meta-stable states, is also discussed and the magnitude of transmission coefficient through the potential barrier is evaluated.
Thermodynamic limit of bifacial double-junction tandem solar cells
Authors: Ryyan Khan M. , Alam Muhammad A.
Published: December 2015

A traditional single-junction solar panel cannot harness ground-scattered light (albedo reflectance, RA), and also suffers from the fundamental sub-band-gap and the thermalization losses. In this paper, we explain how a “bifacial tandem” panel would dramatically reduce these losses, with corresponding improvement in thermodynamic performance. Our study predicts (i) the optimum combination of the band-gaps, empirically given by Eg(t)opt≈Eg(b)opt(2+RA)/3+(1−RA) and the (ii) corresponding optimum normalized output power given by ηT(opt)*≈RA (2ηSJ(opt))+(1−RA)ηDJ(opt). Empirically, ηT(opt)* interpolates between the thermodynamic efficiency limit of classical double-junction tandem cell (ηDJ) and twice that of a single-junction cell (ηSJ). We conclude by explaining how the fundamental loss mechanisms evolve with RA in a bifacial tandem cell.
Acoustic particle palpation for measuring tissue elasticity
Authors: Koruk Hasan , El Ghamrawy Ahmed , Pouliopoulos Antonios N. , Choi James J.
Published: December 2015

We propose acoustic particle palpation—the use of sound to press a population of acoustic particles against an interface—as a method for measuring the qualitative and quantitative mechanical properties of materials. We tested the feasibility of this method by emitting ultrasound pulses across a tunnel of an elastic material filled with microbubbles. Ultrasound stimulated the microbubble cloud to move in the direction of wave propagation, press against the distal surface, and cause deformations relevant for elasticity measurements. Shear waves propagated away from the palpation site with a velocity that was used to estimate the material's Young's modulus.
The smooth entropy formalism for von Neumann algebras
Authors: Berta Mario , Furrer Fabian , Scholz Volkher B.
Published: December 2015

We discuss information-theoretic concepts on infinite-dimensional quantum systems. In particular, we lift the smooth entropy formalism as introduced by Renner and collaborators for finite-dimensional systems to von Neumann algebras. For the smooth conditional min- and max-entropy, we recover similar characterizing properties and information-theoretic operational interpretations as in the finite-dimensional case. We generalize the entropic uncertainty relation with quantum side information of Tomamichel and Renner and discuss applications to quantum cryptography. In particular, we prove the possibility to perform privacy amplification and classical data compression with quantum side information modeled by a von Neumann algebra.
Electron transport in molecular junctions with graphene as protecting layer
Authors: Hüser Falco , Solomon Gemma C.
Published: December 2015

We present ab initio transport calculations for molecular junctions that include graphene as a protecting layer between a single molecule and gold electrodes. This vertical setup has recently gained significant interest in experiment for the design of particularly stable and reproducible devices. We observe that the signals from the molecule in the electronic transmission are overlayed by the signatures of the graphene sheet, thus raising the need for a reinterpretation of the transmission. On the other hand, we see that our results are stable with respect to various defects in the graphene. For weakly physiosorbed molecules, no signs of interaction with the graphene are evident, so the transport properties are determined by offresonant tunnelling between the gold leads across an extended structure that includes the molecule itself and the additional graphene layer. Compared with pure gold electrodes, calculated conductances are about one order of magnitude lower due to the increased tunnelling distance. Relative differences upon changing the end group and the length of the molecule on the other hand, are similar.
Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)
Authors: Francés-Monerris Antonio , Segarra-Martí Javier , Merchán Manuela , Roca-Sanjuán Daniel
Published: December 2015

Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N–H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N–H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π1− and π2− states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.
Robust validation of approximate 1-matrix functionals with few-electron harmonium atoms
Authors: Cioslowski Jerzy , Piris Mario , Matito Eduard
Published: December 2015

A simple comparison between the exact and approximate correlation components U of the electron-electron repulsion energy of several states of few-electron harmonium atoms with varying confinement strengths provides a stringent validation tool for 1-matrix functionals. The robustness of this tool is clearly demonstrated in a survey of 14 known functionals, which reveals their substandard performance within different electron correlation regimes. Unlike spot-testing that employs dissociation curves of diatomic molecules or more extensive benchmarking against experimental atomization energies of molecules comprising some standard set, the present approach not only uncovers the flaws and patent failures of the functionals but, even more importantly, also allows for pinpointing their root causes. Since the approximate values of U are computed at exact 1-densities, the testing requires minimal programming and thus is particularly suitable for rapid screening of new functionals.
Ion-Stockmayer clusters: Minima, classical thermodynamics, and variational ground state estimates of Li+(CH3NO2)n (n = 1–20)
Authors: Curotto E.
Published: December 2015

Structural optimizations, classical NVT ensemble, and variational Monte Carlo simulations of ion Stockmayer clusters parameterized to approximate the Li+(CH3NO2)n (n = 1–20) systems are performed. The Metropolis algorithm enhanced by the parallel tempering strategy is used to measure internal energies and heat capacities, and a parallel version of the genetic algorithm is employed to obtain the most important minima. The first solvation sheath is octahedral and this feature remains the dominant theme in the structure of clusters with n ≥ 6. The first “magic number” is identified using the adiabatic solvent dissociation energy, and it marks the completion of the second solvation layer for the lithium ion-nitromethane clusters. It corresponds to the n = 18 system, a solvated ion with the first sheath having octahedral symmetry, weakly bound to an eight-membered and a four-membered ring crowning a vertex of the octahedron. Variational Monte Carlo estimates of the adiabatic solvent dissociation energy reveal that quantum effects further enhance the stability of the n = 18 system relative to its neighbors.
Note: A cryogenic, ultra-high-vacuum, microwave filter which passes a narrow beam
Authors: Evetts N. , Dosanjh P. , Zvyagintsev V. , Hardy W. N.
Published: December 2015

We report on a device which filters microwave radiation prone to heating cryogenic experiments while at the same time allowing large apertures which will not disturb a propagating beam. A method for evaporating thin films onto the inner face of a narrow tube is also described.
Dielectric inspired scaling of polarization conversion subwavelength resonances in open ultrathin chiral structures
Authors: Serebryannikov Andriy E. , Mutlu Mehmet , Ozbay E.
Published: December 2015

It is shown that the scaling of subwavelength resonances in open ultrathin chiral structures can be obtained by varying only the permittivity of dielectric spacers, while multiband one-way polarization conversion and related asymmetric transmission remain possible. These features are quite general and obtainable in a wide range of parameter variation. Surprisingly, the difference in the power of ε for the classical ε−1/2 scaling rule and the empirical rules obtained in the present letter does not exceed 22%, giving an important entry point for future theoretical studies and design strategies. Both spectral scaling and conservation of the polarization characteristics can be achieved by using either tunneling or real-index impedance matching. The scaled structures with strong polarization and directional selectivity may have thickness of λ/100 and smaller.
Band gap tuning of epitaxial SrTiO3-δ/Si(001) thin films through strain engineering
Authors: Cottier Ryan J. , Steinle Nathan A. , Currie Daniel A. , Theodoropoulou Nikoleta
Published: December 2015

We investigate the effect of strain and oxygen vacancies (VO) on the crystal and optical properties of oxygen deficient, ultra-thin (4–30 nm) films of SrTiO3-δ (STO) grown heteroepitaxially on p-Si(001) substrates by molecular beam epitaxy. We demonstrate that STO band gap tuning can be achieved through strain engineering and show that the energy shift of the direct energy gap transition of SrTiO3-δ/Si films has a quantifiable dimensional and doping dependence that correlates well with the changes in crystal structure.
Magnetometry of micro-magnets with electrostatically defined Hall bars
Authors: Lachance-Quirion Dany , Camirand Lemyre Julien , Bergeron Laurent , Sarra-Bournet Christian , Pioro-Ladrière Michel
Published: December 2015

Micro-magnets are key components for quantum information processing with individual spins, enabling arbitrary rotations and addressability. In this work, characterization of sub-micrometer sized CoFe ferromagnets is performed with Hall bars electrostatically defined in a two-dimensional electron gas. Due to the ballistic nature of electron transport in the cross junction of the Hall bar, anomalies such as the quenched Hall effect appear near zero external magnetic field, thus hindering the sensitivity of the magnetometer to small magnetic fields. However, it is shown that the sensitivity of the diffusive limit can be almost completely restored at low temperatures using a large current density in the Hall bar of about 10 A/m. Overcoming the size limitation of conventional etched Hall bars with electrostatic gating enables the measurement of magnetization curves of 440 nm wide micro-magnets with a signal-to-noise ratio above 103. Furthermore, the inhomogeneity of the stray magnetic field created by the micro-magnets is directly measured using the gate-voltage-dependent width of the sensitive area of the Hall bar.
Assessing the accuracy of some popular DFT methods for computing harmonic vibrational frequencies of water clusters
Authors: Howard J. Coleman , Enyard Jordan D. , Tschumper Gregory S.
Published: December 2015

A wide range of density functional theory (DFT) methods (37 altogether), including pure, hybrid, range-separated hybrid, double-hybrid, and dispersion-corrected functionals, have been employed to compute the harmonic vibrational frequencies of eight small water clusters ranging in size from the dimer to four different isomers of the hexamer. These computed harmonic frequencies have been carefully compared to recently published benchmark values that are expected to be very close to the CCSD(T) complete basis set limit. Of the DFT methods examined here, ωB97 and ωB97X are the most consistently accurate, deviating from the reference values by less than 20 cm−1 on average and never more than 60 cm−1. The performance of double-hybrid methods including B2PLYP and mPW2-PLYP is only slightly better than more economical approaches, such as the M06-L pure functional and the M06-2X hybrid functional. Additionally, dispersion corrections offer very little improvement in computed frequencies.
Al4SiC4 wurtzite crystal: Structural, optoelectronic, elastic, and piezoelectric properties
Authors: Pedesseau L. , Even J. , Modreanu M. , Chaussende D. , Sarigiannidou E. , Chaix-Pluchery O. , Durand O.
Published: December 2015

New experimental results supported by theoretical analyses are proposed for aluminum silicon carbide (Al4SiC4). A state of the art implementation of the density functional theory is used to analyze the experimental crystal structure, the Born charges, the elastic properties, and the piezoelectric properties. The Born charge tensor is correlated to the local bonding environment for each atom. The electronic band structure is computed including self-consistent many-body corrections. Al4SiC4 material properties are compared to other wide band gap wurtzite materials. From a comparison between an ellipsometry study of the optical properties and theoretical results, we conclude that the Al4SiC4 material has indirect and direct band gap energies of about 2.5 eV and 3.2 eV, respectively.
Modeling and de-embedding the interferometric scanning microwave microscopy by means of dopant profile calibration
Authors: Michalas L. , Wang F. , Brillard C. , Chevalier N. , Hartmann J. M. , Marcelli R. , Theron D.
Published: December 2015

This paper presents the full modeling and a methodology for de-embedding the interferometric scanning microwave microscopy measurements by means of dopant profile calibration. A Si calibration sample with different boron-doping level areas is used to that end. The analysis of the experimentally obtained S11 amplitudes based on the proposed model confirms the validity of the methodology. As a specific finding, changes in the tip radius between new and used tips have been clearly identified, leading to values for the effective tip radius in the range of 45 nm to 85 nm, respectively. Experimental results are also discussed in terms of the effective area concept, taking into consideration details related to the nature of tip-to-sample interaction.
Imaging interfacial electrical transport in graphene–MoS2 heterostructures with electron-beam-induced-currents
Authors: White E. R. , Kerelsky Alexander , Hubbard William A. , Dhall Rohan , Cronin Stephen B. , Mecklenburg Matthew , Regan B. C.
Published: December 2015

Heterostructure devices with specific and extraordinary properties can be fabricated by stacking two-dimensional crystals. Cleanliness at the inter-crystal interfaces within a heterostructure is crucial for maximizing device performance. However, because these interfaces are buried, characterizing their impact on device function is challenging. Here, we show that electron-beam induced current (EBIC) mapping can be used to image interfacial contamination and to characterize the quality of buried heterostructure interfaces with nanometer-scale spatial resolution. We applied EBIC and photocurrent imaging to map photo-sensitive graphene-MoS2 heterostructures. The EBIC maps, together with concurrently acquired scanning transmission electron microscopy images, reveal how a device's photocurrent collection efficiency is adversely affected by nanoscale debris invisible to optical-resolution photocurrent mapping.
Grains and grain boundaries contribution to dielectric relaxations and conduction of Bi5Ti3FeO15 ceramics
Authors: Rehman Fida , Li Jing-Bo , Zhang Jia-Song , Rizwan Muhammad , Niu Changlei , Jin Hai-Bo
Published: December 2015

Dielectric relaxation behaviors of Aurivillius Bi5Ti3FeO15 ceramics were investigated in a wide range of frequency and temperature via dielectric and impedance spectroscopies. We distinguished two dielectric relaxations using the combination of impedance and modulus analysis. Resistance of the grain boundary was found to be much larger than grains, whereas capacitance was at the same level. The kinetic analysis of dielectric data was carried out to evaluate the contributions of microstructure and defects to the relaxation and conduction. The possible relaxation-conduction mechanism in the ceramics was discussed. The results enable deep understanding of microstructure-defect-relaxation behaviors in Bi5Ti3FeO15 ceramics.
Digital holography takes to the skies
Authors: Chang Sung
Published: December 2015

The technique allows researchers to image the small-scale structure of clouds.
Increasing abundance of pups of the long-nosed fur seal (Arctocephalus forsteri) on Kangaroo Island, South Australia, over 26 breeding seasons to 2013–14
Authors: Shaughnessy Peter D. , Goldsworthy Simon D.
Published: December 2015

Context
Long-nosed (or New Zealand) fur seals breed on the southern coast of Australia, in New Zealand and on its subantarctic islands. They are recovering from over-harvesting that occurred in the early nineteenth century.

Aims
We estimated the rate of increase of the population at two colonies on Kangaroo Island, South Australia: Cape Gantheaume and Cape du Couedic.

Methods
From 1988–89 to 2013–14, pup abundance was estimated using a mark–resight procedure with multiple resights in large aggregations of pups and by direct counting in small aggregations.

Key results
At Cape Gantheaume, pup numbers increased by a factor of 10.7 from 457 to 5333 over 26 breeding seasons and the exponential rate of increase averaged 10.0% per annum (p.a.). Between 1988–89 and 1997–98, the population increased at 17.3% p.a., after which the increase was 7.2% p.a. At Cape du Couedic, pup numbers increased by a factor of 12.8 from 295 to 4070 over 21 breeding seasons at 11.4% p.a. Between 1988–89 and 1997–98, the increase averaged 14.2% p.a., after which it was 9.6% p.a. These increases have been accompanied by expansion in sub-colonies that existed in January 1989 and establishment of several new sub-colonies. Increases are likely to continue on Kangaroo Island.

Conclusions
There are few examples of increasing population levels for Australian native mammals and this is one of the best documented. It demonstrates that fur seal populations can recover from uncontrolled harvesting provided breeding habitat ashore is protected.

Implications
Fur seals interfere with fishers, disturb farmed tuna in aquaculture pens, and prey on little penguins.
Hydrogel-laden paper scaffold system for origami-based tissue engineering
Authors: Kim Su-Hwan , Lee Hak Rae , Yu Seung Jung , Han Min-Eui , Lee Doh Young , Kim Soo Yeon , Ahn Hee-Jin , Han Mi-Jung , Lee Tae-Ik , Kim Taek-Soo , Kwon Seong Keun , Im Sung Gap , Hwang Nathaniel S.
Published: December 2015

Significance

This work describes an intriguing strategy for the formation of hydrogel-laden multiform structures utilizing paper sheets and suggests a route for trachea tissue engineering. It combines concepts extracted from paper origami, functional thin polymer coating, and thin hydrogel layering on top of the paper scaffolds. A computer-aided design-based lock-and-key arrangement was used for folding the sheets into multiform structures with spatial arrangements. With encapsulating cells in hydrogel-laden paper, the scaffold system was able to deliver biological cues in vivo. In this work, we have successfully applied an origami-based tissue engineering approach to the trachea regeneration model.
Networks of energetic and metabolic interactions define dynamics in microbial communities
Authors: Embree Mallory , Liu Joanne K. , Al-Bassam Mahmoud M. , Zengler Karsten
Published: December 2015

Significance

Microbial communities are critical to global carbon cycling and particularly important in oxygen-limited environments, such as sediments and parts of the human microbiome. However, the uncultured members of these communities often hinder the study of community composition and interspecies interactions at a deeper level. Here, we integrate metagenomic binning, metatranscriptomic analysis, and metabolic modeling to obtain quantitative information about interspecies interactions between individual species present in methanogenic communities. We found that these communities are defined by not only metabolic interactions but also additional interdependencies, such as amino acid auxotrophies. Strategic usage of antimicrobials by specific community members further reinforces this intricate interspecies network, thereby enforcing strong collaboration among community members.
Origin of information-limiting noise correlations
Authors: Kanitscheider Ingmar , Coen-Cagli Ruben , Pouget Alexandre
Published: December 2015

Significance

Populations of neurons encode information in activity patterns that vary across repeated presentation of the same input and are correlated across neurons (noise correlations). Such noise correlations can limit information about sensory stimuli and therefore limit behavioral performance in tasks such as discrimination between two similar stimuli. Therefore it is important to understand where and how noise correlations are generated. Most previous accounts focused on sources of variability inside the brain. Here we focus instead on noise that is injected at the sensory periphery and propagated to the cortex: We show that this simple framework accounts for many known properties of noise correlations and explains behavioral performance in discrimination tasks, without the need to assume further sources of information loss.
Universal brain signature of proficient reading: Evidence from four contrasting languages
Authors: Rueckl Jay G. , Paz-Alonso Pedro M. , Molfese Peter J. , Kuo Wen-Jui , Bick Atira , Frost Stephen J. , Hancock Roeland , Wu Denise H. , Mencl William Einar , Duñabeitia Jon Andoni , Lee Jun-Ren , Oliver Myriam , Zevin Jason D. , Hoeft Fumiko , Carreiras Manuel , Tzeng Ovid J. L. , Pugh Kenneth R. , Frost Ram
Published: December 2015

Significance

Using functional MRI, we examined reading and speech perception in four highly contrasting languages: Spanish, English, Hebrew, and Chinese. With three complementary analytic approaches, we demonstrate that in spite of striking dissimilarities among writing systems, successful literacy acquisition results in a convergence of the speech and orthographic processing systems onto a common network of neural structures. These findings have the major theoretical implication that the reading network has evolved to be universally constrained by the organization of the brain network underlying speech.
Neofunction of ACVR1 in fibrodysplasia ossificans progressiva
Authors: Hino Kyosuke , Ikeya Makoto , Horigome Kazuhiko , Matsumoto Yoshihisa , Ebise Hayao , Nishio Megumi , Sekiguchi Kazuya , Shibata Mitsuaki , Nagata Sanae , Matsuda Shuichi , Toguchida Junya
Published: December 2015

Significance

By utilizing patient-specific induced pluripotent stem cells (iPSCs) of fibrodysplasia ossificans progressiva (FOP) and gene-corrected (rescued) FOP-iPSCs, we discovered a novel mechanism in ectopic bone formation: The disease-causing mutation endows ACVR1 with the ability to transmit the signal of an unexpected ligand, Activin-A. We believe this is a milestone study for FOP research and provides a novel platform for searching therapeutic targets of this intractable disease.
Augmented Binary Substitution: Single-pass CDR germ-lining and stabilization of therapeutic antibodies
Authors: Townsend Sue , Fennell Brian J. , Apgar James R. , Lambert Matthew , McDonnell Barry , Grant Joanne , Wade Jason , Franklin Edward , Foy Niall , Ní Shúilleabháin Deirdre , Fields Conor , Darmanin-Sheehan Alfredo , King Amy , Paulsen Janet E. , Hickling Timothy P. , Tchistiakova Lioudmila , Cunningham Orla , Finlay William J. J.
Published: December 2015

Significance

Immunized animals are a key source of monoclonal antibodies used to treat human diseases. Before clinical use, animal antibodies are typically “humanized” by laborious and suboptimal methods that transfer their full target binding loops (a.k.a. CDRs) into human frameworks. We report an optimal method, where the CDRs from species such as rodents and chickens can be adapted to fit human frameworks in which we have clinical and manufacturing confidence. The Augmented Binary Substitution (ABS) process exploits the fundamental plasticity of antibody CDRs to ultrahumanize antibodies from key species in a single pass. ABS results in a final antibody that is much closer to human germ line in the frameworks and CDRs, minimizing immunogenicity risks in man and maximizing the therapeutic potential of the antibody.
Mitochondrial function in the brain links anxiety with social subordination
Authors: Hollis Fiona , van der Kooij Michael A. , Zanoletti Olivia , Lozano Laura , Cantó Carles , Sandi Carmen
Published: December 2015

Significance

Within a dominance hierarchy, low social status strongly reduces individual well-being. In socially living species, rank in a hierarchy is determined through competitive encounters. Despite the numerous health consequences, the ability of personality traits to predispose individuals to a particular social rank remains largely unclear. Our work identifies trait anxiety as a predisposing factor to a subordinate rank. We demonstrate that mitochondrial function in the nucleus accumbens, a brain region relevant for motivation and depression, is a critical mediating factor in the subordinate status displayed by high-anxious rats. These findings highlight a role for cerebral energy metabolism in social behavior and point to mitochondrial function in the nucleus accumbens as a potential marker and avenue of treatment for mood disorders.
Synaptic P-Rex1 signaling regulates hippocampal long-term depression and autism-like social behavior
Authors: Li Jun , Chai Anping , Wang Lifang , Ma Yuanlin , Wu Zhiliu , Yu Hao , Mei Liwei , Lu Lin , Zhang Chen , Yue Weihua , Xu Lin , Rao Yi , Zhang Dai
Published: December 2015

Significance

Impairments in social behavior and behavioral flexibility have been found in autistic people. However, the genetic mechanism that may contribute to these symptoms is unknown. Here we identified a previously unreported autism-associated gene that regulates synaptic plasticity. The mice lacking this gene exhibit deficits in AMPA receptor endocytosis and synaptic depression because of the blockade of a postsynaptic signaling pathway, leading to autism-like social recognition deficit and behavioral inflexibility. These findings provide new insights into the mechanisms underlying social recognition behavior and suggest that the synaptic depression-related signaling pathway might represent a new therapeutic target for treatment of social recognition deficit disorders such as autism spectrum disorders.
HSV targeting of the host phosphatase PP1α is required for disseminated disease in the neonate and contributes to pathogenesis in the brain
Authors: Wilcox Douglas R. , Muller William J. , Longnecker Richard
Published: December 2015

Significance

The increased severity of herpes simplex virus (HSV) disease in the newborn compared with the adult is a result of complex interactions between the virus and the host response. We studied viral targeting of host-mediated shutoff of protein synthesis during HSV disease in a murine model and found that HSV-1 targeting of the host phosphatase PP1α was required for disseminated disease in the newborn and contributed to HSV encephalitis. Additionally, this report demonstrates that the host response resulting in translational arrest is tissue-specific and also reveals a tissue-specific reliance on the type I IFN response for control of HSV-1. These results provide important insight into the mechanisms of severe HSV disease in the newborn compared with the adult.
Rotational diffusion affects the dynamical self-assembly pathways of patchy particles
Authors: Newton Arthur C. , Groenewold Jan , Kegel Willem K. , Bolhuis Peter G.
Published: December 2015

Significance

Recent experiments show that the rotational diffusion of proteins and patchy colloids does not always follow the Stokes–Einstein relation, especially in crowded environments or with the use of external fields. Because cellular cytoplasm is very crowded, this finding can have consequences for protein complex formation such as viruses. We study the kinetic network of simple models for proteins and patchy colloids and find that their dynamical self-assembly pathways change with varying the rotational diffusion constant. In particular, lowering the rotational diffusion avoids frustrated intermediate states. Such control of kinetic networks would also benefit the design of new self-assembled functional materials.
Production of functional small interfering RNAs by an amino-terminal deletion mutant of human Dicer
Authors: Kennedy Edward M. , Whisnant Adam W. , Kornepati Anand V. R. , Marshall Joy B. , Bogerd Hal P. , Cullen Bryan R.
Published: December 2015

Significance

Although RNA interference (RNAi) is an important antiviral innate-immune response in plants and invertebrates, whether mammals mount effective RNAi responses remains controversial. Using human cells lacking functional Dicer and protein kinase RNA-activated genes, we examined whether wild-type or a deletion mutant of Dicer, lacking the helicase domain, could induce RNAi when presented with double-stranded RNAs derived from plasmids or generated during viral infections. Overexpression of the truncated Dicer mutant resulted in the production of siRNAs in both cases, and these were sufficient to inhibit the expression of cognate mRNAs. Whether the latent ability of human Dicer to induce RNAi will ever be unmasked in vivo remains unclear.