bluuebunny/crossref_metadata_2025 huggingface dataset:
Features of representations in general chemistry textbooks: a peek through the lens of the cognitive load theory
Authors: M. Nyachwaya James , Gillaspie Merry
Published: September 2015

The goals of this study were (1) determine the prevalence of various features of representations in five general chemistry textbooks used in the United States, and (2) use cognitive load theory to draw implications of the various features of analyzed representations. We adapted the Graphical Analysis Protocol (GAP) (Sloughet al., 2010) to look at the type of representations used, the function of each representation, the physical integration of representations with associated text, the presence and nature of captions and labels, the indexing of representations, and the number of representations requiring conceptual integration on a given page. Results indicate that on average, in all five textbooks each page had at least four representations. Most representations served a ‘representational’ function, but a number functioned as decorative representations. Most representations were directly integrated with text, but some of the remaining representations were separated by a whole page from associated text. While many pages had an average of two representations that required conceptual integration with text or other representations, some pages had as many as six representations requiring integration. While using textbooks, learners can experience intrinsic, germane or extraneous cognitive load (Sweller, 1994). Our findings indicate that there are various features of representations that could help reduce intrinsic or extraneous cognitive load. However, we also found prevalent features of representations that imply high intrinsic cognitive load or are likely to lead to extraneous cognitive load. Implications for textbook authors and editors, textbook selection, instruction, and science teacher preparation are discussed.
Morphology-controlled CH3NH3PbI3films by hexane-assisted one-step solution deposition for hybrid perovskite mesoscopic solar cells with high reproductivity
Authors: Lin Na , Qiao Juan , Dong Haopeng , Ma Fusheng , Wang Liduo
Published: September 2015

Morphology-controlled perovskite films were realized byn-hexane to promote crystallization of CH3NH3PbI3, thus improving their thermal stability and performance of the perovskite solar cells.
Carbon-tolerant Ni-based cermet anodes modified by proton conducting yttrium- and ytterbium-doped barium cerates for direct methane solid oxide fuel cells
Authors: Li Meng , Hua Bin , Luo Jing-li , Jiang San Ping , Pu Jian , Chi Bo , Jian Li
Published: September 2015

Impregnation of BCY and BCYb phases improved the initial cell performance and, most importantly, substantially enhanced the durability of the cells in wet methane.
Changes in telomere length and telomerase activity in human bronchial epithelial cells induced by coal tar pitch extract
Authors: Feng Feifei , Yang Yongli , Li Zhitao , Song Jinyan , Zhu Hansong , Wang Lixia , Zhao Yong , Xu Dong , Wu Yongjun , Wu Yiming , Wang Wei
Published: September 2015

Coal tar pitch is a confirmed human carcinogen and is composed mainly of polycyclic aromatic hydrocarbons.
Partial protection of N-acetylcysteine against MPA-capped CdTe quantum dot-induced neurotoxicity in rat primary cultured hippocampal neurons
Authors: Wu Tianshu , He Keyu , Zhan Qinglin , Ang Shengjun , Ying Jiali , Zhang Shihan , Zhang Ting , Xue Yuying , Chen Yilu , Tang Meng
Published: September 2015

CdTe QD exposure caused death and apoptosis of rat primary cultured hippocampal neurons via generating reactive oxygen species and increasing intracellular calcium levels, which could be reversed by a common antioxidant NAC.
Chaos synchronisation of electro‐optical chaotic systems with partially different parameters
Authors: Chen Xiao Feng , Hu Han Ping
Published: September 2015

The authors proposed a chaos synchronisation method for electro‐optical chaotic systems with partially different system parameters. This synchronisation method can not only effectively improve the robustness of synchronisation but also ensure transmission security. According to the Lyapunov stability theorem, the authors analysed the chaos synchronisation between two electro‐optical chaotic systems with partially different system parameters, and provided sufficient conditions to realise stable zero‐lag chaos synchronisation. The authors also designed simple and realisable adaptive control functions that met the sufficient conditions. Finally, the chaos synchronisation of electro‐optical chaotic systems with partially different system parameters was numerically investigated. The results showed that the adaptive control functions can greatly improve the synchronisation performance in such a sender–receiver setup. The numerical results were highly consistent with theoretical results.
Selective harmonic elimination strategy for cascaded H‐bridge five‐level inverter with arbitrary power sharing among the cells
Authors: Hajizadeh Mehdi , Fathi Seyed Hamid
Published: September 2015

Selective harmonic elimination PWM (SHEPWM) is a well‐known fundamental frequency switching method for cascaded multilevel inverters. The main goal in the conventional SHEPWM is to eliminate some lower order harmonics of the output voltage while the fundamental component is satisfied. Thus, this method only regards the inverter output voltage quality, which is not sufficient in many applications. Different cells of the cascaded H‐bridge multilevel inverter are supplied by isolated dc sources which may have different amounts of power. To deliver maximum power of these sources to a load or network, power should be properly shared among the cells. This study presents a modified SHEPWM method to control quality of the output voltage of the cascaded H‐bridge five‐level inverter in wide range of the modulation index while desired power sharing among the cells is also considered as the main priority in the whole range of the modulation index. The method forces new constraint in obtaining optimal switching angles and it may require additional switching. To study the problem, a genetic algorithm optimisation program, based on the modified method, is employed for a three‐phase five‐level inverter. Simulation and experimental results show the effectiveness of the proposed switching method.
Mitigating gas emissions at signalised intersections using wireless vehicle detectors
Authors: Torkudzor Moses Kwasi , Adjin Daniel M.O. , Asare Jack
Published: September 2015

Traffic congestion on roads wastes travel times and increases fuel consumption as well as gas emissions which are dangerous to human health. This has led to growing concern about environmental protection and energy conservation and a number of studies to increase fuel economy and reduce gas emissions. To increase travel times so as to reduce fuel consumption and gas emissions, traffic signals at intersections must be well implemented. It is therefore necessary to employ the current technology of wireless sensor networks to enhance the optimisation of the signalised intersections so as to address such a concern. In this study, a vehicular traffic control model was developed to optimise a signalised intersection, using wireless vehicle detectors. Real‐time traffic volume gathered were analysed to obtain the peak hour traffic volume causing congestion. The intersection was modelled and simulated in Synchro7 as an actuated signalised model using results from the analysed data. The model for morning peak and evening peak periods gave optimal cycle lengths which result in the reduction of gas emissions, fuel consumption and delay at the intersection.
Dynamics of evaporative colloidal patterning
Authors: Kaplan C. Nadir , Wu Ning , Mandre Shreyas , Aizenberg Joanna , Mahadevan L.
Published: September 2015

Drying suspensions often leave behind complex patterns of particulates, as might be seen in the coffee stains on a table. Here, we consider the dynamics of periodic band or uniform solid film formation on a vertical plate suspended partially in a drying colloidal solution. Direct observations allow us to visualize the dynamics of band and film deposition, where both are made of multiple layers of close packed particles. We further see that there is a transition between banding and filming when the colloidal concentration is varied. A minimal theory of the liquid meniscus motion along the plate reveals the dynamics of the banding and its transition to the filming as a function of the ratio of deposition and evaporation rates. We also provide a complementary multiphase model of colloids dissolved in the liquid, which couples the inhomogeneous evaporation at the evolving meniscus to the fluid and particulate flows and the transition from a dilute suspension to a porous plug. This allows us to determine the concentration dependence of the bandwidth and the deposition rate. Together, our findings allow for the control of drying-induced patterning as a function of the colloidal concentration and evaporation rate.
High strain-rate magnetoelasticity in Galfenol
Authors: Domann J. P. , Loeffler C. M. , Martin B. E. , Carman G. P.
Published: September 2015

This paper presents the experimental measurements of a highly magnetoelastic material (Galfenol) under impact loading. A Split-Hopkinson Pressure Bar was used to generate compressive stress up to 275 MPa at strain rates of either 20/s or 33/s while measuring the stress-strain response and change in magnetic flux density due to magnetoelastic coupling. The average Young's modulus (44.85 GPa) was invariant to strain rate, with instantaneous stiffness ranging from 25 to 55 GPa. A lumped parameters model simulated the measured pickup coil voltages in response to an applied stress pulse. Fitting the model to the experimental data provided the average piezomagnetic coefficient and relative permeability as functions of field strength. The model suggests magnetoelastic coupling is primarily insensitive to strain rates as high as 33/s. Additionally, the lumped parameters model was used to investigate magnetoelastic transducers as potential pulsed power sources. Results show that Galfenol can generate large quantities of instantaneous power (80 MW/m3), comparable to explosively driven ferromagnetic pulse generators (500 MW/m3). However, this process is much more efficient and can be cyclically carried out in the linear elastic range of the material, in stark contrast with explosively driven pulsed power generators.
An analogue of Weyl’s law for quantized irreducible generalized flag manifolds
Authors: Matassa Marco
Published: September 2015

We prove an analogue of Weyl’s law for quantized irreducible generalized flag manifolds. This is formulated in terms of a zeta function which, similarly to the classical setting, satisfies the following two properties: as a functional on the quantized algebra it is proportional to the Haar state and its first singularity coincides with the classical dimension. The relevant formulas are given for the more general case of compact quantum groups.
On the solenoidal heat-flux in quasi-ballistic thermal conduction
Authors: Ramu Ashok T. , Bowers John E.
Published: September 2015

The Boltzmann transport equation for phonons is recast directly in terms of the heat-flux by means of iteration followed by truncation at the second order in the spherical harmonic expansion of the distribution function. This procedure displays the heat-flux in an explicitly coordinate-invariant form, and leads to a natural decomposition into two components, namely, the solenoidal component in addition to the usual irrotational component. The solenoidal heat-flux is explicitly shown to arise by applying the heat-flux equation to a right-circular cylinder. These findings are important in the context of phonon resonators that utilize the strong quasi-ballistic thermal transport reported recently in silicon membranes at room temperature.
Analytic smoothing effect for a system of Schrödinger equations with three wave interaction
Authors: Hoshino Gaku , Ozawa Tohru
Published: September 2015

We consider the global Cauchy problem for a system of Schrödinger equations with quadratic interaction. Two types of analytic smoothing effect for the solutions are formulated in the small data setting under the mass resonance condition. One is the usual analytic smoothing effect in space variables in terms of the generator of Galilei transforms. We prove the existence and uniqueness of global solutions which are analytic with respect to Galilei generators for sufficiently small data with exponential decay at infinity in space ℝn with n ≥ 3. The other is analytic smoothing effect in space-time variables in terms of generator of pseudo-conformal and Galilei transforms. We prove the existence and uniqueness of global solutions which are analytic with respect to pseudo-conformal and Galilei generators for sufficiently small data with exponential decay in ℝ4. We also discuss the associated Lagrange structure.
How large are nonadiabatic effects in atomic and diatomic systems?
Authors: Yang Yubo , Kylänpää Ilkka , Tubman Norm M. , Krogel Jaron T. , Hammes-Schiffer Sharon , Ceperley David M.
Published: September 2015

With recent developments in simulating nonadiabatic systems to high accuracy, it has become possible to determine how much energy is attributed to nuclear quantum effects beyond zero-point energy. In this work, we calculate the non-relativistic ground-state energies of atomic and molecular systems without the Born-Oppenheimer approximation. For this purpose, we utilize the fixed-node diffusion Monte Carlo method, in which the nodes depend on both the electronic and ionic positions. We report ground-state energies for all systems studied, ionization energies for the first-row atoms and atomization energies for the first-row hydrides. We find the ionization energies of the atoms to be nearly independent of the Born-Oppenheimer approximation, within the accuracy of our results. The atomization energies of molecular systems, however, show small effects of the nonadiabatic coupling between electrons and nuclei.
Electron percolation in realistic models of carbon nanotube networks
Authors: Simoneau Louis-Philippe , Villeneuve Jérémie , Rochefort Alain
Published: September 2015

The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.
Development status of a next generation ECRIS: MARS-D at LBNL
Authors: Xie D. Z. , Benitez J. Y. , Hodgkinson A. , Loew T. , Lyneis C. M. , Phair L. , Pipersky P. , Reynolds B. , Todd D. S.
Published: September 2015

To demonstrate a Mixed Axial and Radial field System (MARS) as the best magnet scheme for future ECRISs, MARS-D, a demonstrative ECRIS using a NbTi MARS magnet is progressing at Lawrence Berkeley National Laboratory. An optimized MARS design can use either NbTi or Nb3Sn coils with reduced engineering complexities to construct the needed high-field magnets. The optimized magnet design could enhance MARS-D to a next generation ECRIS by producing minimum-B field maxima of 5.6 T axially and 3.2 T radially for operating frequencies up to 45 GHz. In-progress test winding has achieved a milestone demonstrating the fabrication feasibility of a MARS closed-loop coil.
Grand canonical Monte Carlo using solvent repacking: Application to phase behavior of hard disk mixtures
Authors: Kindt James T.
Published: September 2015

A new “solvent repacking Monte Carlo” strategy for performing grand canonical ensemble simulations in condensed phases is introduced and applied to the study of hard-disk systems. The strategy is based on the configuration-bias approach, but uses an auxiliary biasing potential to improve the efficiency of packing multiple solvent particles in the cavity formed by removing one large solute. The method has been applied to study the coexistence of ordered and isotropic phases in three binary mixtures of hard disks with a small mole fraction (xL < 0.02) of the larger “solute” component. A chemical potential of 12.81 ± 0.01 kBT was found to correspond to the freezing transition of the pure hard disk “solvent.” Simulations permitted the study of partitioning of large disks between ordered and isotropic phases, which showed a distinct non-monotonic dependence on size; the isotropic phase was enriched approximately 10-fold, 20-fold, and 5-fold over the coexisting ordered phases at diameter ratios d = 1.4, 2.5, and 3, respectively. Mixing of large and small disks within both phases near coexistence was strongly non-ideal in spite of the dilution. Structures of systems near coexistence were analyzed to determine correlations between large disks’ positions within each phase, the orientational correlation length of small disks within the fluid phases, and the nature of translational order in the ordered phase. The analyses indicate that the ordered phase coexists with an isotropic phase resembling a nanoemulsion of ordered domains of small disks, with large disks enriched at the disordered domain interfaces.
DGDFT: A massively parallel method for large scale density functional theory calculations
Authors: Hu Wei , Lin Lin , Yang Chao
Published: September 2015

We describe a massively parallel implementation of the recently developed discontinuous Galerkin density functional theory (DGDFT) method, for efficient large-scale Kohn-Sham DFT based electronic structure calculations. The DGDFT method uses adaptive local basis (ALB) functions generated on-the-fly during the self-consistent field iteration to represent the solution to the Kohn-Sham equations. The use of the ALB set provides a systematic way to improve the accuracy of the approximation. By using the pole expansion and selected inversion technique to compute electron density, energy, and atomic forces, we can make the computational complexity of DGDFT scale at most quadratically with respect to the number of electrons for both insulating and metallic systems. We show that for the two-dimensional (2D) phosphorene systems studied here, using 37 basis functions per atom allows us to reach an accuracy level of 1.3 × 10−4 Hartree/atom in terms of the error of energy and 6.2 × 10−4 Hartree/bohr in terms of the error of atomic force, respectively. DGDFT can achieve 80% parallel efficiency on 128,000 high performance computing cores when it is used to study the electronic structure of 2D phosphorene systems with 3500-14 000 atoms. This high parallel efficiency results from a two-level parallelization scheme that we will describe in detail.
Nonlinear Raman forward scattering driven by a short laser pulse in a collisional transversely magnetized plasma with nonextensive distribution
Authors: Qiu Hui-Bin , Song Hai-Ying , Liu Shi-Bing
Published: September 2015

Nonlinear Raman forward scattering of an intense short laser pulse with a duration shorter than the plasma period propagating through a homogenous collisional nonextensive distributed plasma in the presence of a uniform magnetic field perpendicular to both the direction of propagation and electric vector of the radiation field is investigated theoretically when ponderomotive, relativistic, and collisional nonlinearities are taken into account. The governing equations for nonlinear wave in the context of nonextensive statistics are given, the nonextensive coupled equations describing the nonlinear Raman forward scattering instability are solved by the Fourier transformation method, and the growth rate of the nonlinear Raman forward scattering instability is obtained. The results in the case q → 1 are consistent with those in the framework of the Maxwellian distribution. It is found that the instability growth rate first decreases on increasing electron thermal velocity, minimizes at a critical thermal velocity, and then increases steeply; the critical temperature dependents on the nonextensive parameter, and the greater nonextensive parameter, correspond to the greater critical temperature; when the thermal velocity of electron is less than the critical speed, the instability growth rate is found to be enhanced as the nonextensive parameter increases; but when the thermal velocity is greater than the critical speed, the instability growth rate decreases on increasing the nonextensive parameter.
Compact low temperature scanning tunneling microscope with in-situ sample preparation capability
Authors: Kim Jungdae , Nam Hyoungdo , Qin Shengyong , Kim Sang-ui , Schroeder Allan , Eom Daejin , Shih Chih-Kang
Published: September 2015

We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper and stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.
Multi-slit triode ion optical system with ballistic beam focusing
Authors: Davydenko V. , Amirov V. , Gorbovsky A. , Deichuli P. , Ivanov A. , Kolmogorov A. , Kapitonov V. , Mishagin V. , Shikhovtsev I. , Sorokin A. , Stupishin N. , Karpushov A. N. , Smirnov A. , Uhlemann R.
Published: September 2015

Multi-slit triode ion-optical systems with spherical electrodes are of interest for formation of intense focused neutral beams for plasma heating. At present, two versions of focusing multi-slit triode ion optical system are developed. The first ion optical system forms the proton beam with 15 keV energy, 140 A current, and 30 ms duration. The second ion optical system is intended for heating neutral beam injector of Tokamak Configuration Variable (TCV). The injector produces focused deuterium neutral beam with 35 keV energy, 1 MW power, and 2 s duration. In the later case, the angular beam divergence of the neutral beam is 20-22 mrad in the direction across the slits of the ion optical system and 12 mrad in the direction along the slits.
Novel modification of Hall-type ion source (study and the first results)
Authors: Goncharov A. A. , Litovko I. V. , Dobrovolsky A. N. , Najko L. V. , Najko I. V.
Published: September 2015

We present the original approach to use plasma accelerators with closed electron drift (Hall-type ion sources), which, unlike traditional accelerators with metal and dielectric walls, have open walls and can be applied for creation cost effective low maintenance plasma devices based on plasma lens configuration for production of converging towards axis accelerated ion beams. The paper describes pilot sample of Hall-type plasma accelerator, the first experimental results, one-dimensional theoretical model, and exact analytical solutions following from it.
β-sheet-like formation during the mechanical unfolding of prion protein
Authors: Tao Weiwei , Yoon Gwonchan , Cao Penghui , Eom Kilho , Park Harold S.
Published: September 2015

Single molecule experiments and simulations have been widely used to characterize the unfolding and folding pathways of different proteins. However, with few exceptions, these tools have not been applied to study prion protein, PrPC, whose misfolded form PrPSc can induce a group of fatal neurodegenerative diseases. Here, we apply novel atomistic modeling based on potential energy surface exploration to study the constant force unfolding of human PrP at time scales inaccessible with standard molecular dynamics. We demonstrate for forces around 100 pN, prion forms a stable, three-stranded β-sheet-like intermediate configuration containing residues 155-214 with a lifetime exceeding hundreds of nanoseconds. A mutant without the disulfide bridge shows lower stability during the unfolding process but still forms the three-stranded structure. The simulations thus not only show the atomistic details of the mechanically induced structural conversion from the native α-helical structure to the β-rich-like form but also lend support to the structural theory that there is a core of the recombinant PrP amyloid, a misfolded form reported to induce transmissible disease, mapping to C-terminal residues ≈160-220.
Anisotropic electrical and thermal conductivity in Bi2AE2Co2O8+δ [AE = Ca, Sr1−xBax (x = 0.0, 0.25, 0.5, 0.75, 1.0)] single crystals
Authors: Dong Song-Tao , Zhang Bin-Bin , Xiong Ye , Lv Yang-Yang , Yao Shu-Hua , Chen Y. B. , Zhou Jian , Zhang Shan-Tao , Chen Yan-Feng
Published: September 2015

Bi2AE2Co2O8+δ (AE represents alkaline earth), constructed by stacking of rock-salt Bi2AE2O4 and triangle CoO2 layers alternatively along c-axis, is one of promising thermoelectric oxides. The most impressive feature of Bi2AE2Co2O8+δ, as reported previously, is their electrical conductivity mainly lying along CoO2 plane, adjusting Bi2AE2O4 layer simultaneously manipulates both thermal conductivity and electrical conductivity. It in turn optimizes thermoelectric performance of these materials. In this work, we characterize the anisotropic thermal and electrical conductivity along both ab-plane and c-direction of Bi2AE2Co2O8+δ (AE = Ca, Sr, Ba, Sr1−xBax) single crystals. The results substantiate that isovalence replacement in Bi2AE2Co2O8+δ remarkably modifies their electrical property along ab-plane; while their thermal conductivity along ab-plane only has a slightly difference. At the same time, both the electrical conductivity and thermal conductivity along c-axis of these materials also have dramatic changes. Certainly, the electrical resistance along c-axis is too high to be used as thermoelectric applications. These results suggest that adjusting nano-block Bi2AE2O4 layer in Bi2AE2Co2O8+δ cannot modify the thermal conductivity along high electrical conductivity plane (ab-plane here). The evolution of electrical property is discussed by Anderson localization and electron-electron interaction U. And the modification of thermal conductivity along c-axis is attributed to the microstructure difference. This work sheds more light on the manipulation of the thermal and electrical conductivity in the layered thermoelectric materials.
Spin dynamics in driven composite multiferroics
Authors: Wang Zidong , Grimson Malcolm J.
Published: September 2015

A spin dynamics approach has been used to study the behavior of the magnetic spins and the electric pseudo-spins in a 1-D composite multiferroic chain with a linear magneto-electric coupling at the interface. The response is investigated with either external magnetic or electric fields driving the system. The spin dynamics is based on the Landau-Lifshitz-Gilbert equation. A Gaussian white noise is later added into the dynamic process to include the thermal effects. The interface requires a closer inspection of the magneto-electric effects. Thus, we construct a 2-D ladder model to describe the behavior of the magnetic spins and the electric pseudo-spins with different magneto-electric couplings.
Defect and temperature dependence of tunneling in InAs/GaSb heterojunctions
Authors: Iutzi Ryan M. , Fitzgerald Eugene A.
Published: September 2015

We assess the origin of the reported temperature dependence of subthreshold slope in many published tunnel field effect transistors (TFETs) by examining the temperature dependence of the intrinsic tunneling at InAs/GaSb interfaces in the absence of three-terminal parasitics. We compare the temperature dependence of peak current, excess current, and conductance slope for interfaces with and without heavy interface defect concentrations. We identify that the tunnel and excess currents depend on temperature and defect density but that the conductance slope, a two-terminal analog to subthreshold slope, depends only on defect density and not temperature, contrasting sharply with the heavy temperature dependence seen in TFETs in literature. We propose that TFETs based on this and similar materials systems are dominated by parasitic effects such as tunneling into oxide trap states, or other parasitics that are not intrinsic to the heterojunction itself, and that in the absence of these effects, the true steepness from band-to-band tunneling is limited by defects and inhomogeneity at the interface.
Frequency modulation in shock wave-boundary layer interaction by repetitive-pulse laser energy deposition
Authors: Tamba T. , Pham H. S. , Shoda T. , Iwakawa A. , Sasoh A.
Published: September 2015

Modulation of shock foot oscillation due to energy deposition by repetitive laser pulses in shock wave-boundary layer interaction over an axisymmetric nose-cylinder-flare model in Mach 1.92 flow was experimentally studied. From a series of 256 schlieren images, density oscillation spectra at each pixel were obtained. When laser pulses of approximately 7 mJ were deposited with a repetition frequency, fe, of 30 kHz or lower, the flare shock oscillation had a peak spectrum equivalent to the value of fe. However, with fe of 40 kHz–60 kHz, it experienced frequency modulation down to lower than 20 kHz.
Transfer-free synthesis of highly ordered Ge nanowire arrays on glass substrates
Authors: Nakata M. , Toko K. , Jevasuwan W. , Fukata N. , Saitoh N. , Yoshizawa N. , Suemasu T.
Published: September 2015

Vertically aligned Ge nanowires (NWs) are directly synthesized on glass via vapor-liquid-solid (VLS) growth using chemical-vapor deposition. The use of the (111)-oriented Ge seed layer, formed by metal-induced crystallization at 325 °C, dramatically improved the density, uniformity, and crystal quality of Ge NWs. In particular, the VLS growth at 400 °C allowed us to simultaneously achieve the ordered morphology and high crystal quality of the Ge NW array. Transmission electron microscopy demonstrated that the resulting Ge NWs had no dislocations or stacking faults. Production of high-quality NW arrays on amorphous insulators will promote the widespread application of nanoscale devices.
Generation of broadband supercontinuum light by double-focusing of a femtosecond laser pulse in air
Authors: Jang D. G. , Nam I. H. , Kim M. S. , Kang K. , Suk H.
Published: September 2015

Generation of broadband supercontinuum light has been of great interest in recent years. In this work, we investigated an interesting way for generation of broadband supercontinuum light by double-focusing of a femtosecond (fs) laser pulses in air. In this method, the fs laser pulse is focused in air and the produced supercontinuum light from the interaction of the laser pulse and air is focused again in air. In this way, we found that the spectral broadening of the supercontinuum light can be a lot more enhanced even with a relatively low laser energy of a few mJ/pulse, compared with the single-focusing method. In this paper, we present the experimental results for the broadband supercontinuum light by the double-focusing method, in addition to numerical simulation results.
An adaptive selective frequency damping method
Authors: Jordi Bastien E. , Cotter Colin J. , Sherwin Spencer J.
Published: September 2015

The selective frequency damping (SFD) method is an alternative to classical Newton’s method to obtain unstable steady-state solutions of dynamical systems. However, this method has two main limitations: it does not converge for arbitrary control parameters, and when it does converge, the time necessary to reach a steady-state solution may be very long. In this paper, we present an adaptive algorithm to address these two issues. We show that by evaluating the dominant eigenvalue of a “partially converged” steady flow, we can select a control coefficient and a filter width that ensure an optimum convergence of the SFD method. We apply this adaptive method to several classical test cases of computational fluid dynamics and we show that a steady-state solution can be obtained with a very limited (or without any) a priori knowledge of the flow stability properties.
Leakage current of germanium-on-insulator-based junctionless nanowire transistors
Authors: Sun Chuanchuan , Liang Renrong , Liu Libin , Wang Jing , Xu Jun
Published: September 2015

Junctionless nanowire transistors (JNTs) have been fabricated on ultra-thin-body germanium-on-insulator (GOI) substrates using a simple Si-compatible top-down process. These JNTs, which have gate lengths and widths that are both less than 100 nm, exhibit good electrical characteristics (Ion/Ioff ratio of ∼105 at Vd = −1 V). The effects of the back gate voltage, temperature, the device dimensions, and the channel doping concentration on the leakage currents of the fabricated devices were experimentally analyzed in detail. The results indicate that the leakage current is mainly affected by the gate tunneling current, the Shockley-Read-Hall generation current, the band-to-band tunneling current and the trap-assisted tunneling current. Design guidelines were then proposed to reduce the leakage currents of GOI-based JNTs.
Integrated tuning fork nanocavity optomechanical transducers with high fMQM product and stress-engineered frequency tuning
Authors: Zhang R. , Ti C. , Davanço M. I. , Ren Y. , Aksyuk V. , Liu Y. , Srinivasan K.
Published: September 2015

Cavity optomechanical systems are being widely developed for precision force and displacement measurements. For nanomechanical transducers, there is usually a trade-off between the frequency (fM) and quality factor (QM), which limits temporal resolution and sensitivity. Here, we present a monolithic cavity optomechanical transducer supporting both high fM and high QM. By replacing the common doubly clamped, Si3N4 nanobeam with a tuning fork geometry, we demonstrate devices with the fundamental fM≈29 MHz and QM≈2.2×105, corresponding to an fMQM product of 6.35×1012 Hz, comparable to the highest values previously demonstrated for room temperature operation. This high fMQM product is partly achieved by engineering the stress of the tuning fork to be 3 times the residual film stress through clamp design, which results in an increase of fM up to 1.5 times. Simulations reveal that the tuning fork design simultaneously reduces the clamping, thermoelastic dissipation, and intrinsic material damping contributions to mechanical loss. This work may find application when both high temporal and force resolution are important, such as in compact sensors for atomic force microscopy.
Modulation of interlayer exchange coupling strength in magnetic tunnel junctions via strain effect
Authors: Jiang Xin , Li Zhipeng , Zheng Yuankai , Kaiser Christian , Diao Zhitao , Fang Jason , Leng Qunwen
Published: September 2015

Interlayer exchange coupling of two ferromagnetic electrodes separated by a thin MgO tunnel barrier is investigated using magneto-optical Kerr effect. We find that the coupling field can be reduced by more than 40% as the thickness of a top Ta capping layer increases from 0.5 to 1.2 nm. In contrast, a similar film stack with an additional 3 nm Ru capping layer displays no such dependence on Ta thickness. Transmission electron microscopy study shows that the oxidation of the exposed Ta capping layer induces changes in the crystalline structures of the underlying films, giving rise to the observed reduction of the interlayer coupling field.
Microsatellite variation for phylogenetic, phylogeographic and population-genetic studies in Lomatia (Proteaceae)
Authors: Milner Melita L. , McIntosh Emma J. , Crisp Michael D. , Weston Peter H. , Rossetto Maurizio
Published: September 2015

Lomatia R.Br. is a genus of 12 species in South America and eastern Australia. Hybridisation is extensive in the Australian species and molecular work is required to understand phylogenetic relationships and examine potential gene flow among species. We developed a library of microsatellite markers for Lomatia silaifolia (Sm.) R.Br. These markers were tested across population samples of L. silaifolia and L. myricoides (C.F.Gaertn.) Domin, assessed for cross amplification across all 12 species of Lomatia, sequenced and inspected for variation in the microsatellite flanking region (MFR), and utilised for phylogeographic and phylogenetic analysis. Nineteen microsatellite markers were tested, 13 of which were polymorphic in size analysis. Four of the markers amplified consistently within Lomatia and the MFR had equivalent to or more sequence variation than the three universal markers (psbA–trnH intergenic spacer, PHYA, ITS). Variation within five individuals of L. silaifolia indicated that MFR could be phylogeographically informative. Combined phylogenetic analysis of Lomatia using universal markers and MFR resulted in a well supported tree; however, phylogenetic analysis of only MFR suggested non-monophyly of the species. Phylogenetic trees supported South American species as being diverged from the Australian species but paraphyletic with respect to the Australian lineage. Relationships among Australian species of Lomatia are correlated with geography rather than morphology. We found that microsatellite markers designed for Lomatia and the flanking regions can be informative at population, phylogenetic and phylogeographic levels.
Morphological and amplified fragment length polymorphism (AFLP) data show that New Zealand endemic Myosotis petiolata (Boraginaceae) comprises three rare and threatened species
Authors: Meudt Heidi M. , Prebble Jessica M. , Stanley Rebecca J. , Thorsen Michael J.
Published: September 2015

Species delimitation is of critical importance in systematics and biological and conservation research. The general-lineage species concept, which defines species as separately evolving metapopulation lineages, considers multiple lines of evidence to identify lineages and delimit species boundaries. Here, we apply the general-lineage concept to the New Zealand endemic Myosotis petiolata Hook.f. (Boraginaceae) species complex, to test its usefulness in the New Zealand Myosotis L. species radiation. We aimed to determine whether the complex contains separately evolving lineages to assess the criteria of monophyly, distinct genotypic clusters and fixed morphological differences by using amplified fragment length polymorphism (AFLP) and morphological data. The use of multiple criteria to identify separately evolving lineages within the M. petiolata complex was effective, but the different criteria were satisfied to varying degrees. Species rank is recommended for each of the currently recognised varieties as Myosotis pottsiana (L.B.Moore) Meudt, Prebble, R.J.Stanley & Thorsen (comb. & stat. nov.), M. pansa (L.B.Moore) Meudt, Prebble, R.J.Stanley & Thorsen (comb. & stat. nov.) and M. petiolata Hook.f. (North Island individuals only). A new allopatric subspecies, M. pansa subsp. praeceps Meudt, Prebble, R.J.Stanley & Thorsen (subsp. nov.), is also described. The distinguishing morphological characters and conservation status of each species are discussed. In addition, the low genetic diversity revealed in our population genetic analyses, coupled with few, fluctuating, disjunct populations, underscores the conservation priority of these three rare endemic New Zealand species.
Orbital pacing of carbon fluxes by a ∼9-My eccentricity cycle during the Mesozoic
Authors: Martinez Mathieu , Dera Guillaume
Published: September 2015

Significance

The Milankovitch cycles are orbitally paced variations in insolation that drove periodic climate changes on Earth at the scale of tens to hundreds of thousands years. Longer ‟grand orbital cycles” also exist, but their impacts on paleoclimate dynamics are not well documented for pre-Cenozoic times. Here we tackle this issue by analyzing the stable isotope fluctuations recorded by fossil cephalopods throughout the Jurassic–Early Cretaceous interval. We document a periodicity of ∼9 My in the carbon cycle, except from 190 to 180 Ma when disturbances occurred. This orbital forcing affected carbon transfers by modulating the hydrological processes and sea-level changes. In summary, this ∼9-My orbital cycle is an important metronome of the greenhouse climate dynamics.
Genetic specificity of face recognition
Authors: Shakeshaft Nicholas G. , Plomin Robert
Published: September 2015

Significance

Diverse cognitive abilities have typically been found to intercorrelate highly and to be strongly influenced by genetics. Recent twin studies have suggested that the ability to recognize human faces is an exception: it is similarly highly heritable, but largely uncorrelated with other abilities. However, assessing genetic relationships—the degree to which traits are influenced by the same genes—requires very large samples, which have not previously been available. This study, using data from more than 2,000 twins, shows for the first time, to our knowledge, that the genetic influences on face recognition are almost entirely unique. This finding provides strong support for the view that face recognition is “special” and may ultimately illuminate the nature of cognitive abilities in general.
Enhanced precipitation variability decreases grass- and increases shrub-productivity
Authors: Gherardi Laureano A. , Sala Osvaldo E.
Published: September 2015

Significance

Although increased climatic variability resulting from climate change has been accepted by the scientific community and forms part of the public narrative, studies of the effect of climatic variability on ecosystems have received much less attention than effects of changes in the mean state of climate. Here, we report on a field experiment where we experimentally increased interannual variability of precipitation while maintaining average precipitation constant. Our results indicated that total productivity and that of grasses declined in response to increased precipitation variability, although shrubs benefited, suggesting a potential shift from grassland to shrubland in the future, with large consequences for the supply of ecosystem services. In addition, the effect of variability increased through time.
Mathematical framework for activity-based cancer biomarkers
Authors: Kwong Gabriel A. , Dudani Jaideep S. , Carrodeguas Emmanuel , Mazumdar Eric V. , Zekavat Seyedeh M. , Bhatia Sangeeta N.
Published: September 2015

Significance

The discovery of cancer at an early stage improves treatment outcomes, yet cancer detection thresholds based on measuring the abundance of biomarkers produced by small tumors are biologically limited. Here we develop a mathematical framework to explore the use of activity-based biomarkers for early cancer detection. In contrast to abundance-based biomarkers, activity-based biomarkers rely on the catalytic activity of enzymes to amplify cancer-derived signals and allow detection of small tumors. Using a class of activity-based biomarkers called synthetic biomarkers, we comprehensively explore how detection sensitivities depend on probe design, enzymatic activity, and organ physiology, and how they may be precisely tuned to reveal the presence of small tumors in humans.
Stress impairs cognitive flexibility in infants
Authors: Seehagen Sabine , Schneider Silvia , Rudolph Julia , Ernst Stephanie , Zmyj Norbert
Published: September 2015

Significance

Infancy is regarded as a period of increased vulnerability to stress, but it is currently unknown how stress influences cognitive functioning in infants. Studies with adults have revealed that stress promotes rigid habitual behavior at the cost of flexible behavior. Here we show that stress similarly affects 15-mo-old infants. Half of the infants underwent a stress induction, the other half did not. Then, all infants learned to habitually perform an action that produced an interesting effect. Once the action had become ineffective, only stressed infants continued performing this action, showing rigid habitual behavior. Nonstressed infants explored an alternative action, showing flexible behavior. If stress occurs frequently, infants’ failure to explore alternative behaviors could hamper knowledge acquisition in the long term.
Glycan modulation and sulfoengineering of anti–HIV-1 monoclonal antibody PG9 in plants
Authors: Loos Andreas , Gach Johannes S. , Hackl Thomas , Maresch Daniel , Henkel Theresa , Porodko Andreas , Bui-Minh Duc , Sommeregger Wolfgang , Wozniak-Knopp Gordana , Forthal Donald N. , Altmann Friedrich , Steinkellner Herta , Mach Lukas
Published: September 2015

Significance

The broadly neutralizing anti–HIV-1 monoclonal antibody (mAb) PG9 requires multiple posttranslational modifications to exhibit its full biological activity, including properN-glycosylation and tyrosine sulfation. We now describe a technology that permits the controlled synthesis of these modifications inNicotiana benthamiana. This technology allowed us to show that sulfated PG9 neutralizes HIV-1 with much higher potency than unsulfated antibody. We also found that glycooptimized mAb versions made in plants are superior to PG9 produced in mammalian cells with respect to mediating antibody-dependent cellular cytotoxicity, an important mAb effector function. Because effector functions are of key importance for antibody-mediated immune control of HIV-1 infections, our results can instruct the development of improved immunotherapeutics for the treatment of AIDS patients.
A new therapeutic effect of simvastatin revealed by functional improvement in muscular dystrophy
Authors: Whitehead Nicholas P. , Kim Min Jeong , Bible Kenneth L. , Adams Marvin E. , Froehner Stanley C.
Published: September 2015

Significance

Duchenne muscular dystrophy (DMD) is a lethal, degenerative muscle disease for which there is no effective treatment. Statins have been used for decades to improve cardiovascular health. In addition to lowering blood cholesterol levels, statins also reduce inflammation, oxidative stress, and fibrosis. These pathogenic processes all contribute to functional decline in DMD muscles. Therefore, we reasoned that statins could be a beneficial treatment for dystrophic muscles. In this study, we show that simvastatin dramatically improves muscle strength and fatigue resistance in DMD (
mdx
) mice. This result was accompanied by significantly reduced inflammation, oxidative stress, and fibrotic deposition in old, degenerated
mdx
muscle. These findings indicate that simvastatin is a promising, novel therapeutic approach for DMD and related muscle disorders.