bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-adiabatic dynamics of molecules in optical cavities
Authors: Kowalewski Markus , Bennett Kochise , Mukamel Shaul
Published: February 2016

Strong coupling of molecules to the vacuum field of micro cavities can modify the potential energy surfaces thereby opening new photophysical and photochemical reaction pathways. While the influence of laser fields is usually described in terms of classical field, coupling to the vacuum state of a cavity has to be described in terms of dressed photon-matter states (polaritons) which require quantized fields. We present a derivation of the non-adiabatic couplings for single molecules in the strong coupling regime suitable for the calculation of the dressed state dynamics. The formalism allows to use quantities readily accessible from quantum chemistry codes like the adiabatic potential energy surfaces and dipole moments to carry out wave packet simulations in the dressed basis. The implications for photochemistry are demonstrated for a set of model systems representing typical situations found in molecules.
The interplay of intrinsic disorder and macromolecular crowding on α-synuclein fibril formation
Authors: Shirai Nobu C. , Kikuchi Macoto
Published: February 2016

α-synuclein (α-syn) is an intrinsically disordered protein which is considered to be one of the causes of Parkinson’s disease. This protein forms amyloid fibrils when in a highly concentrated solution. The fibril formation of α-syn is induced not only by increases in α-syn concentration but also by macromolecular crowding. In order to investigate the coupled effect of the intrinsic disorder of α-syn and macromolecular crowding, we construct a lattice gas model of α-syn in contact with a crowding agent reservoir based on statistical mechanics. The main assumption is that α-syn can be expressed as coarse-grained particles with internal states coupled with effective volume; and disordered states are modeled by larger particles with larger internal entropy than other states. Thanks to the simplicity of the model, we can exactly calculate the number of conformations of crowding agents, and this enables us to prove that the original grand canonical ensemble with a crowding agent reservoir is mathematically equivalent to a canonical ensemble without crowding agents. In this expression, the effect of macromolecular crowding is absorbed in the internal entropy of disordered states; it is clearly shown that the crowding effect reduces the internal entropy. Based on Monte Carlo simulation, we provide scenarios of crowding-induced fibril formation. We also discuss the recent controversy over the existence of helically folded tetramers of α-syn, and suggest that macromolecular crowding is the key to resolving the controversy.
Accurate molecular dynamics and nuclear quantum effects at low cost by multiple steps in real and imaginary time: Using density functional theory to accelerate wavefunction methods
Authors: Kapil V. , VandeVondele J. , Ceriotti M.
Published: February 2016

The development and implementation of increasingly accurate methods for electronic structure calculations mean that, for many atomistic simulation problems, treating light nuclei as classical particles is now one of the most serious approximations. Even though recent developments have significantly reduced the overhead for modeling the quantum nature of the nuclei, the cost is still prohibitive when combined with advanced electronic structure methods. Here we present how multiple time step integrators can be combined with ring-polymer contraction techniques (effectively, multiple time stepping in imaginary time) to reduce virtually to zero the overhead of modelling nuclear quantum effects, while describing inter-atomic forces at high levels of electronic structure theory. This is demonstrated for a combination of MP2 and semi-local DFT applied to the Zundel cation. The approach can be seamlessly combined with other methods to reduce the computational cost of path integral calculations, such as high-order factorizations of the Boltzmann operator or generalized Langevin equation thermostats.
Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory
Authors: Marsalek Ondrej , Markland Thomas E.
Published: February 2016

Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost.
Quantum mechanical grad-B drift velocity operator in a weakly non-uniform magnetic field
Authors: Chan Poh Kam , Oikawa Shun-ichi , Kosaka Wataru
Published: February 2016

This paper presents the analytical solution for quantum mechanical grad-B drift velocity operator by solving the Heisenberg equation of motion. Using the time dependent operators, it is shown the analytical solution of the position operators in x̂(t) and ŷ(t) of the particle in the presence of a weakly non-uniform magnetic field. It is also shown numerically that the grad-B drift velocity operator agrees with the classical counterpart.
Overmoded subterahertz surface wave oscillator with pure TM01 mode output
Authors: Wang Guangqiang , Wang Jianguo , Zeng Peng , Li Shuang , Wang Dongyang
Published: February 2016

Overmoded O-type Cerenkov generators using annular electron beams are facing the problem of multi-modes output due to the inevitable structural discontinuities. A simple but effective method to achieve the pure TM01 mode output is applied on the 0.14 THz overmoded surface wave oscillator (SWO) in this paper. In spite of still using an overmoded slow wave structure to ensure the easy fabrication, the followed smooth circular waveguide is shrinkingly tapered to the output waveguide with appropriate radius that it cuts off other higher modes except TM01 mode. Moreover, the modified device here has the same power capacity as the previous one according to the numerical analysis. By optimized lengths of the transition waveguide and tapered waveguide, particle-in-cell simulation results indicate that the subterahertz wave with output power increased 14.2% at the same frequency is obtained from the proposed SWO under the previous input conditions, and importantly, the output power is all carried by TM01 mode as expected. Further simulation results in the pulse regime confirm the feasibility of the optimized structure in the actual experiments. This simple and viable design is also applicable to overmoded devices in the lower frequency band of subterahertz wave.
On the existence of bound states in asymmetric leaky wires
Authors: Exner Pavel , Vugalter Semjon
Published: February 2016

We analyze spectral properties of a leaky wire model with a potential bias. It describes a two-dimensional quantum particle exposed to a potential consisting of two parts. One is an attractive δ-interaction supported by a non-straight, piecewise smooth curve L dividing the plane into two regions of which one, the “interior,” is convex. The other interaction component is a constant positive potential V0 in one of the regions. We show that in the critical case, V0 = α2, the discrete spectrum is non-void if and only if the bias is supported in the interior. We also analyze the non-critical situations, in particular, we show that in the subcritical case, V0 < α2, the system may have any finite number of bound states provided the angle between the asymptotes of L is small enough.
Infrared study of α–SiO2 single crystal under high pressure
Authors: Pellicer-Porres J. , Segura A. , Santamaría-Pérez D.
Published: February 2016

We have measured high pressure α-quartz reflectance spectra in the mid infrared. We used single crystals, taking full profit of polarization. The quality of the spectra allows fitting the reflectance spectra. We have characterized the pressure evolution of E and A2 modes with increased precision, even in the spectral regions where they overlap. In addition, we have determined the TO-LO splitting of each mode. Some of the A2 modes show dramatic pressure variations of the LO-TO splitting, which cannot be explained only by changes in length and ionicity of individual bonds, requiring a new mechanism. We suggest that rotation of the SiO4 tetrahedra plays a fundamental role. We have also determined the evolution of the electronic dielectric constant under high pressure. We find that its pressure increment is mainly a volume effect, although the small increase in birefringence points to secondary changes associated to the electronic resonances.
Nonlinear vortex structures with perpendicular shear flow, hot ions, and nonthermal distribution of electrons
Authors: Gul-e-Ali  , Masood W. , Mirza Arshad M.
Published: February 2016

Coupling of drift vortex and the ion acoustic modes in the linear and nonlinear regimes are investigated with sheared ion flow perpendicular to the ambient magnetic field in a plasma comprising of hot ions and nonthermal population of electrons. In this regard, generation of nonlinear vortex structures in the presence of kappa, Cairns, and q-nonextensive electron distributions are investigated in detail, and comparison with the Maxwellian distribution is also made. The appositeness of the present investigation in the matter of auroral F-region is also pointed out.
Complementary resistive switching behaviors evolved from bipolar TiN/HfO2/Pt device
Authors: Chen Xinman , Hu Wei , Li Yan , Wu Shuxiang , Bao Dinghua
Published: February 2016

In this letter, the dynamic evolution of TiN/HfO2/Pt device from bipolar resistive switching (BRS) to complementary resistive switching (CRS) was reported. The device exhibits the uniform BRS with long retention, good endurance, and self-compliance characteristics after the asymmetric two-step electroforming. However, BRS of the device eventually transforms to CRS after the transitional processes through controlling the compliance current. Meanwhile, the effective barrier height rises up accordingly as the device evolves from BRS to CRS. These superior resistive switching performances of TiN/HfO2/Pt device here can be elucidated in views of evolution of asymmetric filament. This work confirms the intimate correlation and discrepancy between BRS and CRS, and also indicates the potential application of TiN/HfO2/Pt device for future ultra-dense resistive random access memory.
A theoretical investigation of the structural and electronic properties of 55-atom nanoclusters: The examples of Y–Tc and Pt
Authors: Batista Krys E. A. , Piotrowski Maurício J. , Chaves Anderson S. , Da Silva Juarez L. F.
Published: February 2016

Several studies have found that the Pt55 nanocluster adopts a distorted reduced core structure, DRC55, in which there are 8–11 atoms in the core and 47–44 atoms in the surface, instead of the compact and high-symmetry icosahedron structure, ICO55, with 13 and 42 atoms in the core and surface, respectively. The DRC structure has also been obtained as the putative global minimum configuration (GMC) for the Zn55 (3d), Cd55 (4d), and Au55 (5d) systems. Thus, the DRC55 structure has been reported only for systems with a large occupation of the d-states, where the effects of the occupation of the valence anti-bonding d-states might play an important role. Can we observe the DRC structure for 55-atom transition-metal systems with non-occupation of the anti-bonding d-states? To address this question, we performed a theoretical investigation of the Y 55, Zr55, Nb55, Mo55, Tc55, and Pt55 nanoclusters, employing density functional theory calculations. For the putative GMCs, we found that the Y 55 adopts the ICO55 structure, while Nb55 and Mo55 adopt a bulk-like fragment based on the hexagonal close-packed structure and Tc55 adopts a face-centered cubic fragment; however, Zr55 adopts a DRC55 structure, like Zn55, Cd55, Pt55, and Au55. Thus we can conclude that the preference for DRC55 structure is not related to the occupation of the anti-bonding d-states, but to a different effect, in fact, a combination of structural and electronic effects. Furthermore, we obtained that the binding energy per atom follows the occupation of the bonding and anti-bonding model, i.e., the stability of the studied systems increases from Y to Tc with a small oscillation for Mo, which also explains the equilibrium bond lengths. We obtained a larger magnetic moment for Y 55 (31 μB) which can be explained by the localization of the d-states in Y at nanoscale, which is not observed for the remaining systems (0–1 μB).
Subquantum conductive-bridge memory
Authors: Jameson John R. , Kamalanathan Deepak
Published: February 2016

Resistive memory devices suffer from a tradeoff between operating current and data retention. The key parameter governing this tradeoff is shown to be the 1-atom conductance of the filament material. High 1-atom conductances, comparable to the quantum G0=2e2/h, are shown to make metal filaments unsuitable for low-power applications. Instead by using filaments containing Te, a semiconductor whose 1-atom conductance is deduced to be just 0.03G0, it is shown that operating currents can be reduced by an order of magnitude compared to metals. Such “subquantum” conductive-bridge memory cells are broadly applicable to low-power applications.
A comparison of the optical properties of InGaN/GaN multiple quantum well structures grown with and without Si-doped InGaN prelayers
Authors: Davies M. J. , Hammersley S. , Massabuau F. C.-P. , Dawson P. , Oliver R. A. , Kappers M. J. , Humphreys C. J.
Published: February 2016

In this paper, we report on a detailed spectroscopic study of the optical properties of InGaN/GaN multiple quantum well structures, both with and without a Si-doped InGaN prelayer. In photoluminescence and photoluminescence excitation spectroscopy, a 2nd emission band, occurring at a higher energy, was identified in the spectrum of the multiple quantum well structure containing the InGaN prelayer, originating from the first quantum well in the stack. Band structure calculations revealed that a reduction in the resultant electric field occurred in the quantum well immediately adjacent to the InGaN prelayer, therefore leading to a reduction in the strength of the quantum confined Stark effect in this quantum well. The partial suppression of the quantum confined Stark effect in this quantum well led to a modified (higher) emission energy and increased radiative recombination rate. Therefore, we ascribed the origin of the high energy emission band to recombination from the 1st quantum well in the structure. Study of the temperature dependent recombination dynamics of both samples showed that the decay time measured across the spectrum was strongly influenced by the 1st quantum well in the stack (in the sample containing the prelayer) leading to a shorter average room temperature lifetime in this sample. The room temperature internal quantum efficiency of the prelayer containing sample was found to be higher than the reference sample (36% compared to 25%) which was thus attributed to the faster radiative recombination rate of the 1st quantum well providing a recombination pathway that is more competitive with non-radiative recombination processes.
Isotype InGaN/GaN heterobarrier diodes by ammonia molecular beam epitaxy
Authors: Fireman Micha N. , Browne David A. , Mishra Umesh K. , Speck James S.
Published: February 2016

The design of isotype InGaN/GaN heterobarrier diode structures grown by ammonia molecular beam epitaxy is presented. On the (0001) Ga-polar plane, a structure consisting of a surface n+ GaN contact layer, followed by a thin InGaN layer, followed by a thick unintentionally doped (UID) GaN layer, and atop a buried n+ GaN contact layer induces a large conduction band barrier via a depleted UID GaN layer. Suppression of reverse and subthreshold current in such isotype barrier devices under applied bias depends on the quality of this composite layer polarization. Sample series were grown under fixed InGaN growth conditions that varied either the UID GaN NH3 flow rate or the UID GaN thickness, and under fixed UID GaN growth conditions that varied InGaN growth conditions. Decreases in subthreshold current and reverse bias current were measured for thicker UID GaN layers and increasing InGaN growth rates. Temperature-dependent analysis indicated that although extracted barrier heights were lower than those predicted by 1D Schrödinger Poisson simulations (0.9 eV–1.4 eV for In compositions from 10% to 15%), optimized growth conditions increased the extracted barrier height from ∼11% to nearly 85% of the simulated values. Potential subthreshold mechanisms are discussed, along with those growth factors which might affect their prevalence.
Generalized spectral method for near-field optical microscopy
Authors: Jiang B.-Y. , Zhang L. M. , Castro Neto A. H. , Basov D. N. , Fogler M. M.
Published: February 2016

Electromagnetic interaction between a sub-wavelength particle (the “probe”) and a material surface (the “sample”) is studied theoretically. The interaction is shown to be governed by a series of resonances corresponding to surface polariton modes localized near the probe. The resonance parameters depend on the dielectric function and geometry of the probe as well as on the surface reflectivity of the material. Calculation of such resonances is carried out for several types of axisymmetric probes: spherical, spheroidal, and pear-shaped. For spheroids, an efficient numerical method is developed, capable of handling cases of large or strongly momentum-dependent surface reflectivity. Application of the method to highly resonant materials, such as aluminum oxide (by itself or covered with graphene), reveals a rich structure of multi-peak spectra and nonmonotonic approach curves, i.e., the probe-sample distance dependence. These features also strongly depend on the probe shape and optical constants of the model. For less resonant materials such as silicon oxide, the dependence is weak, so that the spheroidal model is reliable. The calculations are done within the quasistatic approximation with radiative damping included perturbatively.
Large modification in insulator-metal transition of VO2 films grown on Al2O3 (001) by high energy ion irradiation in biased reactive sputtering
Authors: Azhan Nurul Hanis , Okimura Kunio , Ohtsubo Yoshiyuki , Kimura Shin-ichi , Zaghrioui Mustapha , Sakai Joe
Published: February 2016

High energy ion irradiation in biased reactive sputtering enabled significant modification of insulator-metal transition (IMT) properties of VO2 films grown on Al2O3 (001). Even at a high biasing voltage with mean ion energy of around 325 eV induced by the rf substrate biasing power of 40 W, VO2 film revealed low IMT temperature (TIMT) at 309 K (36 °C) together with nearly two orders magnitude of resistance change. Raman measurements from −193 °C evidenced that the monoclinic VO2 lattice begins to transform to rutile-tetragonal lattice near room temperature. Raman spectra showed the in-plane compressive stress in biased VO2 films, which results in shortening of V–V distance along a-axis of monoclinic structure, aM-axis (cR-axis) and thus lowering the TIMT. In respect to that matter, significant effects in shortening the in-plane axis were observed through transmission electron microscopy observations. V2p3/2 spectra from XPS measurements suggested that high energy ion irradiation also induced oxygen vacancies and resulted for an early transition onset and rather broader transition properties. Earlier band gap closing against the temperature in VO2 film with higher biasing power was also probed by ultraviolet photoelectron spectroscopy. Present results with significant modification of IMT behavior of films deposited at high-energy ion irradiation with TIMT near the room temperature could be a newly and effective approach to both exploring mechanisms of IMT and further applications of this material, due to the fixed deposition conditions and rather thicker VO2 films.
Spectral optimization simulation of white light based on the photopic eye-sensitivity curve
Authors: Dai Qi , Hao Luoxi , Lin Yi , Cui Zhe
Published: February 2016

Spectral optimization simulation of white light is studied to boost maximum attainable luminous efficacy of radiation at high color-rendering index (CRI) and various color temperatures. The photopic eye-sensitivity curve V(λ) is utilized as the dominant portion of white light spectra. Emission spectra of a blue InGaN light-emitting diode (LED) and a red AlInGaP LED are added to the spectrum of V(λ) to match white color coordinates. It is demonstrated that at the condition of color temperature from 2500 K to 6500 K and CRI above 90, such white sources can achieve spectral efficacy of 330–390 lm/W, which is higher than the previously reported theoretical maximum values. We show that this eye-sensitivity-based approach also has advantages on component energy conversion efficiency compared with previously reported optimization solutions.
Van der Waals epitaxy of ultrathin α-MoO3 sheets on mica substrate with single-unit-cell thickness
Authors: Wang Di , Li Jing-Ning , Zhou Yu , Xu Di-Hu , Xiong Xiang , Peng Ru-Wen , Wang Mu
Published: February 2016

We report on van der Waals epitaxy of single-crystalline α-MoO3 sheets with single-unit-cell thickness on the mica substrate. The crystalline lattice structure, growth habits, and Raman spectra of the grown α-MoO3 sheets are analyzed. The anisotropic growth of α-MoO3 sheets can be understood by period bond chains theory. Unlike monolayer MoS2 or graphene, Raman spectra of α-MoO3 do not possess frequency shift from bulk crystal to single-unit-cell layer. The relative intensities of two Raman modes (Ag) at 159 and 818 cm−1 are sensitive to the polarization of incident light. This scenario provides a quick approach to determine the lattice orientation of α-MoO3 crystals. Our studies indicate that van der Waals epitaxial growth is a simple and effective way to fabricate high-quality ultrathin α-MoO3 sheets for physical property investigations and potential applications.
Production yield of rare-earth ions implanted into an optical crystal
Authors: Kornher Thomas , Xia Kangwei , Kolesov Roman , Kukharchyk Nadezhda , Reuter Rolf , Siyushev Petr , Stöhr Rainer , Schreck Matthias , Becker Hans-Werner , Villa Bruno , Wieck Andreas D. , Wrachtrup Jörg
Published: February 2016

Rare-earth (RE) ions doped into desired locations of optical crystals might enable a range of novel integrated photonic devices for quantum applications. With this aim, we have investigated the production yield of cerium and praseodymium by means of ion implantation. As a measure, the collected fluorescence intensity from both implanted samples and single centers was used. With a tailored annealing procedure for cerium, a yield up to 53% was estimated. Praseodymium yield amounts up to 91%. Such high implantation yield indicates a feasibility of creation of nanopatterned rare-earth doping and suggests strong potential of RE species for on-chip photonic devices.
Characterizing macroscopic lateral distortion in nanoimprint lithography using moiré interferometry
Authors: Dai X. , Xie H. , Dai F. , Kishimoto S.
Published: February 2016

Distortion in nanoimprint lithography (NIL) can be well checked using various microscopes in a microscale region, but it is difficult to complete wafer-level/macroscopic distortion testing. As an alternative solution to the above issue, we apply moiré interferometry to characterize the macroscopic lateral distortion in NIL by detecting the strain between the stamp and its duplication. With a self-developed moiré interferometry system, distortion can be directly visualized by the fringe pattern with a field of view on the centimeter scale, which is not possible employing other methods. The proposed method is verified in two typical experiments and is shown to be a powerful tool for the characterization of distortion induced in NIL. The method is able to locate the position and affected zone of a defect in a grating structure rapidly and simultaneously.
Multilevel radiative thermal memory realized by the hysteretic metal-insulator transition of vanadium dioxide
Authors: Ito Kota , Nishikawa Kazutaka , Iizuka Hideo
Published: February 2016

Thermal information processing is attracting much interest as an analog of electronic computing. We experimentally demonstrated a radiative thermal memory utilizing a phase change material. The hysteretic metal-insulator transition of vanadium dioxide (VO2) allows us to obtain a multilevel memory. We developed a Preisach model to explain the hysteretic radiative heat transfer between a VO2 film and a fused quartz substrate. The transient response of our memory predicted by the Preisach model agrees well with the measured response. Our multilevel thermal memory paves the way for thermal information processing as well as contactless thermal management.
Fully CMOS-compatible titanium nitride nanoantennas
Authors: Briggs Justin A. , Naik Gururaj V. , Petach Trevor A. , Baum Brian K. , Goldhaber-Gordon David , Dionne Jennifer A.
Published: February 2016

CMOS-compatible fabrication of plasmonic materials and devices will accelerate the development of integrated nanophotonics for information processing applications. Using low-temperature plasma-enhanced atomic layer deposition (PEALD), we develop a recipe for fully CMOS-compatible titanium nitride (TiN) that is plasmonic in the visible and near infrared. Films are grown on silicon, silicon dioxide, and epitaxially on magnesium oxide substrates. By optimizing the plasma exposure per growth cycle during PEALD, carbon and oxygen contamination are reduced, lowering undesirable loss. We use electron beam lithography to pattern TiN nanopillars with varying diameters on silicon in large-area arrays. In the first reported single-particle measurements on plasmonic TiN, we demonstrate size-tunable darkfield scattering spectroscopy in the visible and near infrared regimes. The optical properties of this CMOS-compatible material, combined with its high melting temperature and mechanical durability, comprise a step towards fully CMOS-integrated nanophotonic information processing.
A candidate Zr-doped Sb2Te alloy for phase change memory application
Authors: Zheng Yonghui , Cheng Yan , Zhu Min , Ji Xinglong , Wang Qing , Song Sannian , Song Zhitang , Liu Weili , Feng Songlin
Published: February 2016

Here, Zr-doped Sb2Te alloy is proposed for phase change memory (PCM). Zr-doping enhances the crystallization temperature and thermal stability of Sb2Te alloy effectively. Crystalline Zr2(Sb2Te)98 film is manifested as a single phase without phase separation and the growth of crystal grain is dramatically suppressed. The density change of Zr2(Sb2Te)98 material between amorphous and crystalline is ∼2.65 ± 0.03%, which is much smaller than that of Ge2Sb2Te5 (6.5%). Phase change memory cells based on Zr2(Sb2Te)98 material can be reversibly switched by applying 40–400 ns width voltage pulses, and the reset current is relatively small when comparing with the prototypical Ge2Sb2Sb5 material. The resistance ON-OFF ratio of about 1.3 orders of magnitude is enough for figuring “0” and “1” out. Besides, endurance up to 4.1 × 104 cycles makes Zr-doped Sb2Te alloy a potential candidate for PCM.
Green electroluminescence from Tb4O7 films on silicon: Impact excitation of Tb3+ ions by hot carriers
Authors: Zhu Chen , Lv Chunyan , Jiang Miaomiao , Zhou Junwei , Li Dongsheng , Ma Xiangyang , Yang Deren
Published: February 2016

We report on green electroluminescence (EL) due to the intra-4f transitions of the trivalent terbium (Tb3+) ions inherent in a Tb4O7 film that is sandwiched between the ITO film and heavily phosphorous- or boron-doped silicon (n+-Si or p+-Si) substrate, thus forming the so-called metal-oxide-semiconductor (MOS) device. The onset voltage of such EL is below 10 V. From the current-voltage characteristic and voltage-dependent EL spectra of the aforementioned MOS device, it is derived that the Tb-related green EL results from the impact excitation of Tb3+ ions by the hot electrons (holes), which stem from the electric-field acceleration of the electrons (holes) injected from the n+-Si (p+-Si) substrate via the trap-assisted tunneling mechanism.
A naturally grown three-dimensional nonlinear photonic crystal
Authors: Xu Tianxiang , Lu Dazhi , Yu Haohai , Zhang Huaijin , Zhang Yong , Wang Jiyang
Published: February 2016

Nonlinear frequency conversion via three-dimensional (3D) quasi-phase matching (QPM) process is experimentally realized based on a Ba0.77Ca0.23TiO3 (BCT) crystal. The ferroelectric domains in BCT crystal are observed, and the results reveal that the antiparallel domains distribute in three dimensions and can provide 3D reciprocal lattice vectors for QPM processes. Broadband petal-like second-harmonic patterns are achieved, which are well consistent with the theoretical quasi-cubic model of 3D nonlinear photonic crystals. Our work not only promotes the development of QPM technique but also builds a platform for 3D nonlinear optics and quantum optics.
Low temperature formation of higher-k cubic phase HfO2 by atomic layer deposition on GeOx/Ge structures fabricated by in-situ thermal oxidation
Authors: Zhang R. , Huang P.-C. , Taoka N. , Yokoyama M. , Takenaka M. , Takagi S.
Published: February 2016

We have demonstrated a low temperature formation (300 °C) of higher-k HfO2 using atomic layer deposition (ALD) on an in-situ thermal oxidation GeOx interfacial layer. It is found that the cubic phase is dominant in the HfO2 film with an epitaxial-like growth behavior. The maximum permittivity of 42 is obtained for an ALD HfO2 film on a 1-nm-thick GeOx form by the in-situ thermal oxidation. It is suggested from physical analyses that the crystallization of cubic phase HfO2 can be induced by the formation of six-fold crystalline GeOx structures in the underlying GeOx interfacial layer.
Efficient thermal energy harvesting using nanoscale magnetoelectric heterostructures
Authors: Etesami S. R. , Berakdar J.
Published: February 2016

Thermomechanical cycles with a ferroelectric working substance convert heat to electrical energy. As shown here, magnetoelectrically coupled ferroelectric/ferromagnetic composites (also called multiferroics) allow for an efficient thermal energy harvesting at room temperature by exploiting the pyroelectric effect. By virtue of the magnetoelectric coupling, external electric and magnetic fields can steer the operation of these heat engines. Our theoretical predictions are based on a combination of Landau-Khalatnikov-Tani approach (with a Ginzburg-Landau-Devonshire potential) to simulate the ferroelectric dynamics coupled to the magnetic dynamics. The latter is treated via the electric-polarization-dependent Landau-Lifshitz-Gilbert equation. By performing an adapted Olsen cycle we show that a multiferroic working substance is potentially much more superior to the sole ferroelectrics, as far as the thermal energy harvesting using pyroelectric effect is concerned. Our proposal holds promise not only for low-energy consuming devices but also for cooling technology.
Experimental validation of ultra-thin metalenses for N-beam emissions based on transformation optics
Authors: Zhang Kuang , Ding Xumin , Wo Deliang , Meng Fanrong , Wu Qun
Published: February 2016

A general design of metalenses for N-beam emissions is proposed based on transformation optics. A linear mapping function is adopted to achieve the homogeneous characterization of the transforming medium, which is therefore easy to be achieved compared with previous designs limited by inhomogeneity based on transformation optics. To verify the theoretical design, a four-beam antenna constructed with ultrathin, homogenous, and uniaxial anisotropic metalens is designed, fabricated, and measured. It is shown that the realized gain of the four-beam antenna is increased by 6 dB compared with the single dipole source, while working frequency and relative bandwidth are kept unchanged. The measured far-field pattern verifies theoretical design procedure.
Memcapacitive characteristics in reactive-metal (Mo, Al)/HfOX/n-Si structures through migration of oxygen by applied voltage
Authors: Yang Paul , Noh Young Jun , Baek Yoon-Jae , Zheng Hong , Kang Chi Jung , Lee Hyun Ho , Yoon Tae-Sik
Published: February 2016

Memcapacitive characteristics were investigated in metal-oxide-semiconductor (MOS) structure of reactive electrode (Mo, Al) and hafnium oxide (HfOX) on n-type Si substrate. The capacitance-voltage curves exhibited sequentially changing capacitance with memory function as repeating voltage sweeps, featured the memcapacitive behaviors. The saturation capacitance was decreased by repeating +V sweeps, while barely changed by −V sweeps. Also, the capacitance-time curves disclosed the same tendency. However, the MOS structure with inert Pt electrode did not show the capacitance change. The memcapacitive behaviors were induced by the migration of oxygen ions from HfOX to reactive electrodes by applied voltage, which altered the permittivity of HfOX.
Terahertz spectroscopy across liquid crystalline phase transitions
Authors: Reuter M. , Vieweg N. , Koch M. , Dierking I.
Published: February 2016

Using terahertz time-domain spectroscopy we investigate the far-infrared properties of liquid crystal CE8 which exhibits a plethora of phases upon variation of the temperature. Phase transitions that are correlated with structural ordering at different dimensions clearly reflect in the terahertz refractive index. On the contrary, phase transitions related to ordering phenomena within a certain group of phases do not lead to significant steps in the n(T) relation. Nevertheless, we additionally demonstrate that also 2nd order phase transitions, like the SmA*-SmC* phase change, can be resolved by THz spectroscopy.
Radiative heat transfer between nanoparticles enhanced by intermediate particle
Authors: Wang Yanhong , Wu Jingzhi
Published: February 2016

Radiative heat transfer between two polar nanostructures at different temperatures can be enhanced by resonant tunneling of surface polaritons. Here we show that the heat transfer between two nanoparticles is strongly varied by the interactions with a third nanoparticle. By controlling the size of the third particle, the time scale of thermalization toward the thermal bath temperature can be modified over 5 orders of magnitude. This effect provides control of temperature distribution in nanoparticle aggregation and facilitates thermal management at nanoscale.
The crest-tailed mulgara (Dasycercus cristicauda) in the south-eastern Strzelecki Desert
Authors: Letnic Mike , Feit Anna , Mills Charlotte , Feit Benjamin
Published: February 2016

We report observations of the crest-tailed mulgara (Dasycercus cristicauda) in the south-eastern Strzelecki Desert. Our observations, made during spotlight surveys and using infrared cameras, extend the contemporary range of D. cristicauda to the east by 180 km but subfossil records show that these observations are within the pre-European-settlement range of the species. Whether our observations represent a range expansion or localised population irruption of a previously unknown refuge population is not known. Future studies are recommended to establish the distribution of D. cristicauda in the region and the factors determining its distribution and abundance.
Infrared PINEM developed by diffraction in 4D UEM
Authors: Liu Haihua , Baskin John Spencer , Zewail Ahmed H.
Published: February 2016

Significance

One of the most significant advances made is the ability to visualize nanoscale objects and to determine their shapes (through imaging) and their atomic-scale structure (through diffraction). Furthermore, for optical excitation of the nanostructure the photon-induced near-field EM (PINEM) imaging results in the mapping of nanostructure plasmonics with high spatial–temporal resolution. Here, we show that PINEM can be exploited in the infrared region with greater sensitivity, and that diffraction can be implemented for structural dynamics. Just as importantly, the time resolution of ultrafast EM (UEM), which already far exceeds, by 10 orders of magnitude, that of conventional EM, may be further enhanced by IR PINEM and photon gating with the unprecedented energy resolution (0.63 eV) reported here for UEM.
Project ECHO (Extension for Community Healthcare Outcomes): A New Model for Educating Primary Care Providers about Treatment of Substance Use Disorders
Authors: Komaromy Miriam , Duhigg Dan , Metcalf Adam , Carlson Cristina , Kalishman Summers , Hayes Leslie , Burke Tom , Thornton Karla , Arora Sanjeev
Published: February 2016

Background

Project ECHO (Extension for Community Healthcare Outcomes) trains and mentors primary care providers (PCPs) in the care of patients with complex conditions. ECHO is a distance education model that connects specialists with numerous PCPs via simultaneous video link for the purpose of facilitating case-based learning. This article describes a teleECHO clinic based at the University of New Mexico Health Sciences Center that is focused on treatment of substance use disorders (SUDs) and behavioral health disorders.

Methods

Since 2005, specialists in treatment of SUDs and behavioral health disorders at Project ECHO have offered a weekly 2-hour Integrated Addictions and Psychiatry (IAP) TeleECHO Clinic focused on supporting PCP evaluation and treatment of SUDs and behavioral health disorders. We tabulate the number of teleECHO clinic sessions, participants, and CME/CEU (continuing medical education/continuing education unit) credits provided annually. This teleECHO clinic has also been used to recruit physicians to participate in DATA-2000 buprenorphine waiver trainings. Using a database of the practice location of physicians who received the buprenorphine waiver since 2002, the number of waivered physicians per capita in US states was calculated. The increase in waivered physicians practicing in underserved areas in New Mexico was evaluated and compared with the rest of the United States.

Results

Since 2008, approximately 950 patient cases have been presented during the teleECHO clinic, and more than 9000 hours of CME/CEU have been awarded. Opioids are the substances discussed most commonly (31%), followed by alcohol (21%) and cannabis (12%). New Mexico is near the top among US states in DATA-2000 buprenorphine-waivered physicians per capita, and it has had much more rapid growth in waivered physicians practicing in traditionally underserved areas compared with the rest of the United States since the initiation of the teleECHO clinic focused on SUDs in 2005. Conclusion: The ECHO model provides an opportunity to promote expansion of access to treatment for opioid use disorder and other SUDs, particularly in underserved areas.
Effects of a multifactorial injury prevention intervention in physical education teachers: A randomized controlled trial
Authors: Vercruysse Sien , Haerens Leen , Verhagen Evert , Goossens Lennert , De Clercq Dirk
Published: February 2016

Physical education (PE) teachers are at a high risk of musculoskeletal sports or work‐related injuries because of the physical activity as inherent part of their profession. Such injuries have a negative impact on work and leisure time activities, and effective injury prevention interventions are needed. The present study aimed at testing the effectiveness of an injury prevention intervention that was developed and optimized according to PE teachers' wishes and values. Fifty‐five PE teachers were randomly assigned to intervention or control group. Intervention group teachers engaged in two days of training during which they familiarized with eight injury prevention strategies (seven intrinsic and one extrinsic). A special feature of the intervention was that the way of delivery was based on the self‐determination theory in order to stimulate participants' motivation to adhere to the proposed strategies. Prospective registrations during one school year were conducted concerning injuries and preventive behaviours. Results showed that the intervention group teachers had a lower number of injuries per 1000 h time of exposure (TOE) than the controls (INT: 0.49, CON: 1.14 injuries/1000 h TOE, OR: 2.32, 95% CI: 1.06–5.07), and applied a broader variety of strategies including dynamic and static stretching, core stability, balance and strength training, when compared to the controls who mainly engaged in warming‐up. In conclusion, with the same amount of time, an injury reduction was found in PE teachers through a more balanced use of provided preventive strategies.
The other-race effect in face learning: Using naturalistic images to investigate face ethnicity effects in a learning paradigm
Authors: Hayward William G. , Favelle Simone K. , Oxner Matt , Chu Ming Hon , Lam Sze Man
Published: February 2016

The other-race effect in face identification has been reported in many situations and by many different ethnicities, yet it remains poorly understood. One reason for this lack of clarity may be a limitation in the methodologies that have been used to test it. Experiments typically use an old–new recognition task to demonstrate the existence of the other-race effect, but such tasks are susceptible to different social and perceptual influences, particularly in terms of the extent to which all faces are equally individuated at study. In this paper we report an experiment in which we used a face learning methodology to measure the other-race effect. We obtained naturalistic photographs of Chinese and Caucasian individuals, which allowed us to test the ability of participants to generalize their learning to new ecologically valid exemplars of a face identity. We show a strong own-race advantage in face learning, such that participants required many fewer trials to learn names of own-race individuals than those of other-race individuals and were better able to identify learned own-race individuals in novel naturalistic stimuli. Since our methodology requires individuation of all faces, and generalization over large image changes, our finding of an other-race effect can be attributed to a specific deficit in the sensitivity of perceptual and memory processes to other-race faces.
Vorticity is a Marker of Diastolic Ventricular Interdependency in Pulmonary Hypertension
Authors: Schäfer Michal , Browning James , Schroeder Joyce D. , Shandas Robin , Kheyfets Vitaly O. , Buckner J. Kern , Hunter Kendall S. , Hertzberg Jean R. , Fenster Brett E.
Published: February 2016

Our objective was to determine whether left ventricular (LV) vorticity (ω), the local spinning motion of a fluid element, correlated with markers of ventricular interdependency in pulmonary hypertension (PH). Maladaptive ventricular interdependency is associated with interventricular septal shift, impaired LV performance, and poor outcomes in PH patients, yet the pathophysiologic mechanisms underlying fluid‐structure interactions in ventricular interdependency are incompletely understood. Because conformational changes in chamber geometry affect blood flow formations and dynamics, LV ω may be a marker of LV‐RV (right ventricular) interactions in PH. Echocardiography was performed for 13 PH patients and 10 controls for assessment of interdependency markers, including eccentricity index (EI), and biventricular diastolic dysfunction, including mitral valve (MV) and tricuspid valve (TV) early and late velocities (E and A, respectively) as well as MV septal and lateral early tissue Doppler velocities (e′). Same‐day 4‐dimensional cardiac magnetic resonance was performed for LV E (early)‐wave ω measurement. LV E‐wave ω was significantly decreased in PH patients (P = 0.008) and correlated with diastolic EI (Rho = −0.53, P = 0.009) as well as with markers of LV diastolic dysfunction, including MV E(Rho = 0.53, P = 0.011), E/A (Rho = 0.56, P = 0.007), septal e′ (Rho = 0.63, P = 0.001), and lateral e′ (Rho = 0.57, P = 0.007). Furthermore, LV E‐wave ω was associated with indices of RV diastolic dysfunction, including TV e′ (Rho = 0.52, P = 0.012) and TV E/A (Rho = 0.53, P = 0.009). LV E‐wave ω is decreased in PH and correlated with multiple echocardiographic markers of ventricular interdependency. LV ω may be a novel marker for fluid‐tissue biomechanical interactions in LV‐RV interdependency.
Suppressing magnetic island and accelerating its rotation by modulated resonant magnetic perturbation
Authors: Hu Qiming , Yu Q.
Published: February 2016

A new method is investigated for stabilizing large magnetic islands or neoclassical tearing modes (NTMs) and for accelerating mode rotation by using modulated resonant magnetic perturbation (RMP). The RMP is applied via feedback control only when the phase difference between the mode and RMP is in the range of π  ⩽  Φ  ⩽  2π. Nonlinear numerical modeling based on reduced magnetohydrodynamics (MHD) equations has been carried out. It is found that the mode/island can be either completely or substantially suppressed, when the RMP is applied in the phase region π  ⩽  Φ  ⩽  1.5π or π  ⩽  Φ  ⩽  2π. The mode frequency is significantly increased for the second case. This method can also be utilized for avoiding mode locking, which often triggers plasma disruption.
Kinetic modelling for neoclassical transport of high-Z impurity particles using a binary collision method
Authors: Homma Y. , Yamoto S. , Sawada Y. , Inoue H. , Hatayama A.
Published: February 2016

A new kinetic model for neoclassical impurity particle transport simulation has been developed. Our model is able to simulate the following two effects, which have been theoretically predicted, but neglected in most of the existing kinetic impurity transport simulations in the SOL (scrape-off layer)/Divertor plasmas of tokamak; (1) the neoclassical inward pinch (NC IWP) due to the density gradient of background plasmas and (2) the neoclassical temperature screening effect (NC TSE, outward transport) caused by the plasma temperature gradient. The IWP and TSE, both proportional to the impurity charge number Z, become especially important for higher-Z impurities such as tungsten. In this paper we focus on the case where background plasmas are in the Pfirsch–Schlüter regime. The velocity distribution of background plasma ions is modelled by a distorted Maxwellian distribution, which includes the Pfirsch–Schlüter flow velocity and the Pfirsch–Schlüter heat flux density, in order to reproduce the NC IWP and NC TSE. A series of test simulations have been performed for a toroidal magnetic field geometry. Characteristics of the neoclassical transport, such as dependencies on the safety factor and on the impurity charge number, have been confirmed.