bluuebunny/crossref_metadata_2025 huggingface dataset:
High throughput integrated thermal characterization with non-contact optical calorimetry
Authors: Hou Sichao , Huo Ruiqing , Su Ming
Published: October 2017

Commonly used thermal analysis tools such as calorimeter and thermal conductivity meter are separated instruments and limited by low throughput, where only one sample is examined each time. This work reports an infrared based optical calorimetry with its theoretical foundation, which is able to provide an integrated solution to characterize thermal properties of materials with high throughput. By taking time domain temperature information of spatially distributed samples, this method allows a single device (infrared camera) to determine the thermal properties of both phase change systems (melting temperature and latent heat of fusion) and non-phase change systems (thermal conductivity and heat capacity). This method further allows these thermal properties of multiple samples to be determined rapidly, remotely, and simultaneously. In this proof-of-concept experiment, the thermal properties of a panel of 16 samples including melting temperatures, latent heats of fusion, heat capacities, and thermal conductivities have been determined in 2 min with high accuracy. Given the high thermal, spatial, and temporal resolutions of the advanced infrared camera, this method has the potential to revolutionize the thermal characterization of materials by providing an integrated solution with high throughput, high sensitivity, and short analysis time.
Roles of strain and domain boundaries on the phase transition stability of VO2 thin films
Authors: Jian Jie , Chen Aiping , Chen Youxing , Zhang Xinghang , Wang Haiyan
Published: October 2017

The fundamental phase transition mechanism and the stability of the semiconductor-to-metal phase transition properties during multiple thermal cycles have been investigated on epitaxial vanadium dioxide (VO2) thin films via both ex situ heating and in situ heating by transmission electron microscopy (TEM). VO2 thin films were deposited on c-cut sapphire substrates by pulsed laser deposition. Ex situ studies show the broadening of transition sharpness (ΔT) and the width of thermal hysteresis (ΔH) after 60 cycles. In situ TEM heating studies reveal that during thermal cycles, large strain was accumulated around the domain boundaries, which was correlated with the phase transition induced lattice constant change and the thermal expansion. It suggests that the degradation of domain boundary structures in the VO2 films not only caused the transition property reduction (e.g., the decrease in ΔT and ΔH) but also played an important role in preventing the film from fracture during thermal cycles.
A thermodynamic structural model of graphene oxide
Authors: Luo Haining , Auchterlonie Graeme , Zou Jin
Published: October 2017

Graphene oxide is an easy-to-make material that has a similar structure with graphene. However, the real structure of graphene oxide is still controversial, and an accurate structural model is crucial for understanding its various properties. In this study, by using molecular mechanics and density functional theory, we introduce a thermodynamically favorable structural model of graphene oxide with chemical composition variable from C1.5O to C2.5O. We also calculate their theoretical Raman spectra and electronic properties. It has been found that, in the proposed graphene oxide structure, the para-substituted epoxide groups stay in close proximity to the hydroxyl, but on the opposite sides of the carbon sheet. In addition, on the edge of graphene oxide sheet, the carboxyl prefers attachment in the armchair orientation, while the carbonyl prefers the zigzag orientation.
Ultra-low turn-on voltage and on-resistance vertical GaN-on-GaN Schottky power diodes with high mobility double drift layers
Authors: Fu Houqiang , Huang Xuanqi , Chen Hong , Lu Zhijian , Baranowski Izak , Zhao Yuji
Published: October 2017

This letter reports the implementation of double-drift-layer (DDL) design into GaN vertical Schottky barrier diodes (SBDs) grown on free-standing GaN substrates. This design balances the trade-off between desirable forward turn-on characteristics and high reverse breakdown capability, providing optimal overall device performances for power switching applications. With a well-controlled metalorganic chemical vapor deposition process, the doping concentration of the top drift layer was reduced, which served to suppress the peak electric field at the metal/GaN interface and increase the breakdown voltages of the SBDs. The bottom drift layer was moderately doped to achieve low on-resistance to reduce power losses. At forward bias, the devices exhibited a record low turn-on voltage of 0.59 V, an ultra-low on-resistance of 1.65 mΩ cm2, a near unity ideality factor of 1.04, a high on/off ratio of ∼1010, and a high electron mobility of 1045.2 cm2/(V s). Detailed comparisons with conventional single-drift-layer (SDL) GaN vertical SBDs indicated that DDL design did not degrade the forward characteristics of the SBDs. At reverse bias, breakdown voltages of the DDL GaN SBDs were considerably enhanced compared to those of the conventional SDL devices. These results showed that GaN vertical SBDs with DDL designs are promising candidates for high efficiency, high voltage, high frequency power switching applications.
Extended dynamic mode decomposition with dictionary learning: A data-driven adaptive spectral decomposition of the Koopman operator
Authors: Li Qianxiao , Dietrich Felix , Bollt Erik M. , Kevrekidis Ioannis G.
Published: October 2017

Numerical approximation methods for the Koopman operator have advanced considerably in the last few years. In particular, data-driven approaches such as dynamic mode decomposition (DMD)51 and its generalization, the extended-DMD (EDMD), are becoming increasingly popular in practical applications. The EDMD improves upon the classical DMD by the inclusion of a flexible choice of dictionary of observables which spans a finite dimensional subspace on which the Koopman operator can be approximated. This enhances the accuracy of the solution reconstruction and broadens the applicability of the Koopman formalism. Although the convergence of the EDMD has been established, applying the method in practice requires a careful choice of the observables to improve convergence with just a finite number of terms. This is especially difficult for high dimensional and highly nonlinear systems. In this paper, we employ ideas from machine learning to improve upon the EDMD method. We develop an iterative approximation algorithm which couples the EDMD with a trainable dictionary represented by an artificial neural network. Using the Duffing oscillator and the Kuramoto Sivashinsky partical differential equation as examples, we show that our algorithm can effectively and efficiently adapt the trainable dictionary to the problem at hand to achieve good reconstruction accuracy without the need to choose a fixed dictionary a priori. Furthermore, to obtain a given accuracy, we require fewer dictionary terms than EDMD with fixed dictionaries. This alleviates an important shortcoming of the EDMD algorithm and enhances the applicability of the Koopman framework to practical problems.
Irreversible light-soaking effect of perovskite solar cells caused by light-induced oxygen vacancies in titanium oxide
Authors: Liu Gang , Yang Bingchu , Liu Baoxing , Zhang Chujun , Xiao Si , Yuan Yongbo , Xie Haipeng , Niu Dongmei , Yang Junliang , Gao Yongli , Zhou Conghua
Published: October 2017

An irreversible light-soaking effect was disclosed in perovskite solar cells using TiO2 as an electron transporting layer. The power conversion efficiency of a fresh device was improved more by twice after light soaking for 15 min and then remained 70% even though the device was recovered in the dark for 4 days. The buried mechanism was explored by shedding light on the interaction between light and titanium dioxide. Oxygen vacancies in TiO2 were found to be increased by light-soaking, especially for wavelengths shorter than 400 nm. Such vacancies enhanced the N-type doping in the semiconductor, which not only increased the conductivity of the titania film but also accelerated the charge extraction rate between perovskite crystallites and titania, and finally contributed to upgraded power conversion efficiency.
Distance-including rigorous upper bounds and tight estimates for two-electron integrals over long- and short-range operators
Authors: Thompson Travis H. , Ochsenfeld Christian
Published: October 2017

We introduce both rigorous and non-rigorous distance-dependent integral estimates for four-center two-electron integrals derived from a distance-including Schwarz-type inequality. The estimates are even easier to implement than our so far most efficient distance-dependent estimates [S. A. Maurer et al., J. Chem. Phys. 136, 144107 (2012)] and, in addition, do not require well-separated charge-distributions. They are also applicable to a wide range of two-electron operators such as those found in explicitly correlated theories and in short-range hybrid density functionals. For two such operators with exponential distance decay [e−r12 and erfc(0.11⋅r12)/r12], the rigorous bound is shown to be much tighter than the standard Schwarz estimate with virtually no error penalty. The non-rigorous estimate gives results very close to an exact screening for these operators and for the long-range 1/r12 operator, with errors that are completely controllable through the integral screening threshold. In addition, we present an alternative form of our non-rigorous bound that is particularly well-suited for improving the PreLinK method [J. Kussmann and C. Ochsenfeld, J. Chem. Phys. 138, 134114 (2013)] in the context of short-range exchange calculations.
Instrumental development of a quasi-relativistic ultrashort electron beam source for electron diffractions and spectroscopies
Authors: Shin Young-Min , Figora Michael
Published: October 2017

A stable femtosecond electron beam system has been configured for time-resolved pump-probe experiments. The ultrafast electron diffraction (UED) system is designed with a sub-MeV photoelectron beam source pulsed by a femtosecond UV laser and nondispersive beamline components, including a bunch compressor—a pulsed S-band klystron is installed and fully commissioned with 5.5 MW peak power in a 2.5 μs pulse length. A single-cell RF photo-gun is designed to produce 1.6–16 pC electron bunches in a photoemission mode with 150 fs pulse duration at 0.5–1 MeV. The measured RF system jitters are within 1% in magnitude and 0.2° in phase, which would induce 3.4 keV and 0.25 keV of ΔE, corresponding to 80 fs and 5 fs of Δt, respectively. Our particle-in-cell simulations indicate that the designed bunch compressor reduces the time-of-arrival jitter by about an order of magnitude. The transport and focusing optics of the designed beamline with the bunch compressor enables an energy spread within 10−4 and a bunch length (electron probe) within <500 fs. In this paper, the design analysis and instrumental test results are presented along with the development of the quasi-relativistic UED system.
Ultrafast and nonlinear spectroscopy of brilliant green-based nanoGUMBOS with enhanced near-infrared emission
Authors: Karam Tony E. , Siraj Noureen , Zhang Zhenyu , Ezzir Abdulrahman F. , Warner Isiah M. , Haber Louis H.
Published: October 2017

The synthesis, characterization, ultrafast dynamics, and nonlinear spectroscopy of 30 nm nanospheres of brilliant green–bis(pentafluoroethylsulfonyl)imide ([BG][BETI]) in water are reported. These thermally stable nanoparticles are derived from a group of uniform materials based on organic salts (nanoGUMBOS) that exhibit enhanced near-infrared emission compared with the molecular dye in water. The examination of ultrafast transient absorption spectroscopy results reveals that the overall excited-state relaxation lifetimes of [BG][BETI] nanoGUMBOS are longer than the brilliant green molecular dye in water due to steric hindrance of the torsional degrees of freedom of the phenyl rings around the central carbon. Furthermore, the second harmonic generation signal of [BG][BETI] nanoGUMBOS is enhanced by approximately 7 times and 23 times as compared with colloidal gold nanoparticles of the same size and the brilliant green molecular dye in water, respectively. A very clear third harmonic generation signal is observed from the [BG][BETI] nanoGUMBOS but not from either the molecular dye or the gold nanoparticles. Overall, these results show that [BG][BETI] nanoGUMBOS exhibit altered ultrafast and nonlinear spectroscopy that is beneficial for various applications including nonlinear imaging probes, biomedical imaging, and molecular sensing.
Characterization of single polyvinylidene fluoride (PVDF) nanofiber for flow sensing applications
Authors: Sengupta D. , Kottapalli A. G. P. , Chen S. H. , Miao J. M. , Kwok C. Y. , Triantafyllou M. S. , Warkiani M. E. , Asadnia M.
Published: October 2017

The use of Polyvinylidene Fluoride (PVDF) based piezoelectric nanofibers for sensing and actuation has been reported widely in the past. However, in most cases, PVDF piezoelectric nanofiber mats have been used for sensing applications. This work fundamentally characterizes a single electrospun PVDF nanofiber and demonstrates its application as a sensing element for nanoelectromechanical sensors (NEMS). PVDF nanofiber mats were spun by far field electrospinning (FFES) process and complete material characterization was conducted by means of scanning electron microscope (SEM) imaging, Raman Spectroscopy and FTIR spectroscopy. An optimized recipe was developed for spinning a single suspended nanofiber on a specially designed MEMS substrate which allows the nano-mechanical and electrical characterization of a single PVDF nanofiber. Electrical characterization is conducted using a single suspended nanofiber to determine the piezoelectric coefficient (d33) of the nanofiber to be -58.77 pm/V. Also the mechanical characterization conducted using a nanoindenter revealed a Young’s Modulus and hardness of 2.2 GPa and 0.1 GPa respectively. Finally, an application that utilizes the single PVDF nanofiber as a sensing element to form a NEMS flow sensor is demonstrated. The single nanofiber flow sensor is tested in presence of various oscillatory flow conditions.
Bias-free tunability of microwave properties in multilayer rhomboid shaped nanomagnets
Authors: Tian Chang , Adeyeye Adekunle Olusola
Published: October 2017

The magnetization dynamics of single multilayer rhomboid shaped nanomagnets is investigated using micro-focused Brillouin light scattering spectroscopy. The nanomagnets consist of two permalloy layers separated by a nonmagnetic Cr spacer layer. By varying the Cr thickness in the range from 0 to 15 nm, the dipolar coupling is effectively controlled, thus modifying the corresponding magnetic ground states. The magnetization dynamics as a function of initialization field orientation has been systematically investigated. A significant tunable frequency difference of ∼2 GHz in the microwave absorption between ferromagnetic and antiferromagnetic ground states is observed as the size of nanomagnets is varied. Micromagnetic simulations validate our experimental observations.
Microbead-regulated surface wrinkling patterns in a film–substrate system
Authors: Zhang Cheng , Wang Jiawen , Cao Yan-Ping , Lu Conghua , Li Bo , Feng Xi-Qiao
Published: October 2017

The control of surface wrinkling patterns at the microscale is a concern in many applications. In this letter, we regulate surface wrinkling patterns on a film–substrate system by introducing microbeads atop the film. Both experiments and theoretical analysis reveal the changes in surface wrinkles induced by microbeads. Under equibiaxial compression, the film–substrate system without microbeads bonded on its upper surface often buckles into global, uniform labyrinths, whereas the labyrinthine pattern locally gives way to radial stripes emanating from the microbeads. This regulation of surface wrinkles depends on the sizes and spacing of microbeads. We combine the finite element method and the Fourier spectral method to explore the physical mechanisms underlying the phenomena. This study offers a viable technique for engineering surfaces with tunable functions.
Large voltage-controlled magnetic anisotropy in the SrTiO3/Fe/Cu structure
Authors: Peng Shouzhong , Li Sai , Kang Wang , Zhou Jiaqi , Lei Na , Zhang Youguang , Yang Hongxin , Li Xiang , Amiri Pedram Khalili , Wang Kang L. , Zhao Weisheng
Published: October 2017

First-principles calculations are performed to investigate the magnetic anisotropy and voltage-controlled magnetic anisotropy (VCMA) in the strontium titanate (SrTiO3)-based structure. It is found that SrTiO3/Fe/Cu gives rise to an interfacial perpendicular magnetic anisotropy (PMA) of 1.3 mJ/m2. More importantly, the VCMA coefficient of this structure is 37% larger than that of the MgO-based counterpart. The microscopic mechanism is elucidated by resolving the VCMA effect to each atomic layer and each orbital hybridization. We demonstrate that the VCMA effect is not confined at the first Fe monolayer of the SrTiO3/Fe interface but extends into the second and third Fe monolayers. The origin of these phenomena can be explained with the changes of contributions to PMA from each orbital hybridization induced by redistributions of orbital occupancy under an electric field.
Highly sensitive humidity sensor based on graphene oxide foam
Authors: Zhang Kai-Lun , Hou Zhi-Ling , Zhang Bao-Xun , Zhao Quan-Liang
Published: October 2017

Since sensitive humidity sensing is strongly desired, we present a highly sensitive humidity sensor fabricated from graphene oxide (GO) foam based on low-frequency dielectric properties. The GO foam shows humidity- and compression-dependent dielectric. Upon applying compression on GO foam, the humidity sensitivity increases and the maximum humidity sensitivity of dielectric loss is more than 12-fold higher than that of direct-current electrical conductivity. The highly sensitive humidity response originates from the generation of local conductive networks, which is the result of the connected isolated conductive regions by water cluster. Additionally, the dielectric properties of fabricated GO foam show a stable and repeatable humidity response, suggesting a carbon prototype with great potential in humidity sensors.
On E–discretization of tori of compact simple Lie groups. II
Authors: Hrivnák Jiří , Juránek Michal
Published: October 2017

Ten types of discrete Fourier transforms of Weyl orbit functions are developed. Generalizing one-dimensional cosine, sine, and exponential, each type of the Weyl orbit function represents an exponential symmetrized with respect to a subgroup of the Weyl group. Fundamental domains of even affine and dual even affine Weyl groups, governing the argument and label symmetries of the even orbit functions, are determined. The discrete orthogonality relations are formulated on finite sets of points from the refinements of the dual weight lattices. Explicit counting formulas for the number of points of the discrete transforms are deduced. Real-valued Hartley orbit functions are introduced, and all ten types of the corresponding discrete Hartley transforms are detailed.
Coherent laser-millimeter-wave interactions en route to coherent population transfer
Authors: Grimes David D. , Barnum Timothy J. , Zhou Yan , Colombo Anthony P. , Field Robert W.
Published: October 2017

We demonstrate coherent two-photon population transfer to Rydberg states of barium atoms using a combination of a pulsed dye laser and a chirped-pulse millimeter-wave spectrometer. Numerical calculations, using a density matrix formalism, reproduce our experimental results and explain the factors responsible for the observed fractional population transferred, optimal experimental conditions, and possibilities for future improvements. The long coherence times associated with the millimeter-wave radiation aid in creating coherence between the ground state and Rydberg states, but higher-coherence laser sources are required to achieve stimulated Raman adiabatic passage and for applications to molecules.
Thermal-induced magnetic transition in CoFe2O4@ZnO
Authors: Herojit Singh L. , Pati Sudhanshu S. , Oliveira A. C. , Garg Vijayendra K , Kuzmann Erno
Published: October 2017

Composites of CoFe2O4 and ZnO (CFO@ZnO) nanomaterials were synthesized using double stage co-precipitation. The structural properties have been investigated by x-ray diffraction which shows the presence of hexagonal ZnO and spinel CoFe2O4. Variation in lattice parameters, after annealing at elevated temperature, indicates the diffusion of cations from the ZnO to CoFe2O4 and vice versa. Magnetic properties were measured by Mössbauer spectroscopy and superconducting quantum interference device magnetometer. The transition from ferrimagnet to paramagnet at 973 K is due to the formation of ZnFe2O4. High quadrupole splitting values in Mössbauer spectra depict the presence of interstitial Co defects. The Co cations diffuse in the ZnO lattice in the course of annealing at 1273 K, forming CoxZn1−xO resulting in ferromagnetism.
Femtosecond-laser surface modification and micropatterning of diamond-like nanocomposite films to control friction on the micro and macroscale
Authors: Pimenov S. M. , Zavedeev E. V. , Arutyunyan N. R. , Zilova O. S. , Shupegin M. L. , Jaeggi B. , Neuenschwander B.
Published: October 2017

Laser surface micropatterning (texturing) of hard materials and coatings is an effective technique to improve tribological systems. In the paper, we have investigated the laser-induced surface modifications and micropatterning of diamond-like nanocomposite (DLN) films (a-C:H,Si:O) using IR and visible femtosecond (fs) lasers, focusing on the improvement of frictional properties of laser-patterned films on the micro and macroscale. The IR and visible fs-lasers, operating at λ = 1030 nm and λ = 515 nm wavelengths (pulse duration 320 fs and pulse repetition rate 101 kHz), are used to fabricate different patterns for subsequent friction tests. The IR fs-laser is applied to produce hill-like micropatterns under conditions of surface graphitization and incipient ablation, and the visible fs-laser is used for making microgroove patterns in DLN films under ablation conditions. Regimes of irradiation with low-energy IR laser pulses are chosen to produce graphitized micropatterns. For these regimes, results of numerical calculations of the temperature and graphitized layer growth are presented to show good correlation with surface relief modifications, and the features of fs-laser graphitization are discussed based on Raman spectroscopy analysis. Using lateral force microscopy, the role of surface modifications (graphitization, nanostructuring) in the improved microfriction properties is investigated. New data of the influence of capillary forces on friction forces, which strongly changes the microscale friction behaviour, are presented for a wide range of loads (from nN to μN) applied to Si tips. In macroscopic ball-on-disk tests, a pair-dependent friction behaviour of laser-patterned films is observed. The first experimental data of the improved friction properties of laser-micropatterned DLN films under boundary lubricated sliding conditions are presented. The obtained results show the DLN films as an interesting coating material suitable for laser patterning applications in tribology.
Non-destructive patterning of 10 nm magnetic island array by phase transformation with low-energy proton irradiation
Authors: Dutta Tanmay , Pathak Sachin , Asbahi Mohamed , Celik Kubra , Lee Jong Min , Yang Ping , Saifullah M. S. M. , Oral Ahmet , Bhatia C. S. , Cha Jongin , Hong Jongill , Yang Hyunsoo
Published: October 2017

Nano-patterning on the order of sub-10 nm is integral to achieve high-density nano-scale devices for various data storage and data processing applications. However, the additional requirement of planarization and unwanted side-effects of physical or chemical etching have so far limited the patterning of sub-10 nm devices. In this work, we have demonstrated the creation of an array of ∼10 nm ferromagnetic islands through selective phase transformation of paramagnetic multilayers by low-energy proton irradiation. Paramagnetic Co3O4/Pd multilayers masked with patterned PMMA (polymethyl methacrylate) were reduced to ferromagnetic Co/Pd by proton irradiation. A clear contrast of the nano-islands was observed using magnetic force microscopy, establishing the formation of ferromagnetic nano-islands with perpendicular magnetic anisotropy. This process provides a way to circumvent the side-effects associated with both conventional nano-scale pattering and high-energy ion irradiation. Therefore, phase transformation by low energy proton irradiation can be used for patterning sub-10 nm nano-islands, not only for magnetic data storage but also for patterning various opto-electronic and spintronic devices.
Traveling wave solutions of the nonlinear Schrödinger equation
Authors: Akbari-Moghanjoughi M.
Published: October 2017

In this paper, we investigate the traveling soliton and the periodic wave solutions of the nonlinear Schrödinger equation (NLSE) with generalized nonlinear functionality. We also explore the underlying close connection between the well-known KdV equation and the NLSE. It is remarked that both one-dimensional KdV and NLSE models share the same pseudoenergy spectrum. We also derive the traveling wave solutions for two cases of weakly nonlinear mathematical models, namely, the Helmholtz and the Duffing oscillators' potentials. It is found that these models only allow gray-type NLSE solitary propagations. It is also found that the pseudofrequency ratio for the Helmholtz potential between the nonlinear periodic carrier and the modulated sinusoidal waves is always in the range 0.5 ≤ Ω/ω  ≤  0.537285 regardless of the potential parameter values. The values of Ω/ω = {0.5, 0.537285} correspond to the cnoidal waves modulus of m = {0, 1} for soliton and sinusoidal limits and m = 0.5, respectively. Moreover, the current NLSE model is extended to fully NLSE (FNLSE) situation for Sagdeev oscillator pseudopotential which can be derived using a closed set of hydrodynamic fluid equations with a fully integrable Hamiltonian system. The generalized quasi-three-dimensional traveling wave solution is also derived. The current simple hydrodynamic plasma model may also be generalized to two dimensions and other complex situations including different charged species and cases with magnetic or gravitational field effects.
Mechanical properties of nano and bulk Fe pillars using molecular dynamics and dislocation dynamics simulation
Authors: Nath S. K. Deb
Published: October 2017

Using molecular dynamics simulation, tension and bending tests of a Fe nanopillar are carried out to obtain its Young’s modulus and yield strength. Then the comparative study of Young’s modulus and yield strength of a Fe nanopillar under bending and tension are carried out varying its diameter in the range of diameter 1-15nm. We find out the reasons why bending Young’s modulus and yield strength of a Fe nanopillar are higher than those of tension Young’s modulus and yield strength of a Fe nanopillar. Using the mobility parameters of bulk Fe from the experimental study [N. Urabe and J. Weertman, Materials Science and Engineering 18, 41 (1975)], its temperature dependent stress-strain relationship, yield strength and strain hardening modulus are obtained from the dislocation dynamics simulations. Strain rate dependent yield strength and strain hardening modulus of bulk Fe pillars under tension are studied. Temperature dependent creep behaviors of bulk Fe pillars under tension are also studied. To verify the soundness of the present dislocation dynamics studies of the mechanical properties of bulk Fe pillars under tension, the stress vs. strain relationship and dislocation density vs. strain of bulk Fe pillars obtained by us are compared with the published results obtained by S. Queyreau, G. Monnet, and B. Devincre, International Journal of Plasticity 25, 361 (2009).
Autosurfactant of the second kind: Bi enables δ-doping of Bi in Si
Authors: Murata Koichi , Miki Kazushi , Fukatsu Susumu
Published: October 2017

Surfactants in heteroepitaxy are catalytic elements that float up to the surface during growth to control the energetics/kinetics of adatoms. “Autosurfactants” are exceptional in that the surfactant action is self-contained without foreign species. So far, autosurfactants as surface smootheners are known. Here, we demonstrate a different class of autosurfactants as surface-segregation quenchers: Bi, a dopant with a strong surface-segregation tendency in Si, is utilized to lock otherwise elusive Bi adatoms themselves to the Si lattice underneath during molecular beam epitaxy. Quasi-1D δ-doping of Bi in Si up to 4 × 1020 cm−3 in terms of volume concentration is achieved.
High performance metamaterial device with enhanced electromagnetic energy harvesting efficiency
Authors: Shang Shuai , Yang Shizhong , Shan Meng , Liu Jing , Cao Hailin
Published: October 2017

A high performance metamaterial device for electromagnetic energy harvesting is presented. The unit cell of the metamaterial device consists of four identical omega ring resonators arranged in rotational symmetry, and each omega ring is loaded with a 50 Ω resistor that mimics the input impedance of a rectifier circuit. A proof-of-concept prototype is designed for operation at the frequency of 5.8 GHz. Here, the efficient energy harvesting is validated by the energy dissipated in each resistor. Based on the full absorption concept, the metamaterial device achieves a harvesting efficiency up to 93.1% under normal incidence. In addition, the energy harvester shows polarization independent and wide-angle incident frequency responses with good harvesting characteristics over the entire operating range. The surface current distribution is analyzed to gain an insight into the energy harvesting mechanism. Moreover, the harvester prototype is manufactured and measured, and the simulated and measured results are in good agreement. Due to the enhanced electromagnetic energy harvesting efficiency, the proposed device is a good candidate for microwave power transmission.
Commonalities in frequency-dependent viscoelastic damping in glasses in the MHz to THz regime
Authors: Ranganathan Raghavan , Shi Yunfeng , Keblinski Pawel
Published: October 2017

We use non-equilibrium molecular dynamics oscillatory shear simulations to study frequency-dependent viscoelastic damping spanning nearly six decades in frequency range (MHz to THz), in a wide range of model glasses including binary glasses such as Cu-Zr metallic glass (MG), Wahnström glass and amorphous silica, and unary glasses, namely, Dzugutov glass and amorphous silicon. First, for the Cu-Zr MG, we elucidate the role of quench rate, number of shear cycles, shear amplitude, and shear temperature on the damping characteristics. We observe striking commonalities in damping characteristics for all glasses studied—(i) a peak in the loss modulus in the high-frequency regime (∼THz) and (ii) persistent damping in the low-frequency regime (extending down to 10 s of MHz). The high-frequency peak is seen to overlap with the range of natural vibrational frequencies for each glass, and arises from coupling between the excited harmonic vibrational modes. On the other hand, persistent damping at intermediate and low frequencies is shown to be a result of long time-scale local, irreversible deformation.
Fluid dynamic breakthrough in two connected capillaries: From stationary to oscillating state
Authors: Chevalier S. , Josset C. , Auvity B.
Published: October 2017

In this paper, we investigate the pore structure and the impacts of Haines jumps on the change in preferential pathways (called the dynamic breakthrough) during fluid percolation through thin porous media. Two capillaries connected in parallel are used to represent a thin porous medium, and Haines jumps are observed through the formation of droplets. Using a droplet growth model and experimental visualisations, the change in preferential pathways is shown to be strongly influenced by the pore lengths, pore radii ratios, and droplet detachment volumes. This work provides a better understanding of the redevelopment of continuous fluid paths observed through thin porous media in electrochemical systems.
Limit theorems for linear spectrum statistics of orthogonal polynomial ensembles and their applications in random matrix theory
Authors: Pan Guangming , Wang Shaochen , Zhou Wang
Published: October 2017

In this paper, we consider the asymptotic behavior of Xfn(n)≔∑i=1nfn(xi), where xi,i=1,…,n form orthogonal polynomial ensembles and fn is a real-valued, bounded measurable function. Under the condition that VarXfn(n)→∞, the Berry-Esseen (BE) bound and Cramér type moderate deviation principle (MDP) for Xfn(n) are obtained by using the method of cumulants. As two applications, we establish the BE bound and Cramér type MDP for linear spectrum statistics of Wigner matrix and sample covariance matrix in the complex cases. These results show that in the edge case (which means fn has a particular form f(x)I(x≥θn) where θn is close to the right edge of equilibrium measure and f is a smooth function), Xfn(n) behaves like the eigenvalues counting function of the corresponding Wigner matrix and sample covariance matrix, respectively.
Hafnium nitride films for thermoreflectance transducers at high temperatures: Potential based on heating from laser absorption
Authors: Rost Christina M. , Braun Jeffrey , Ferri Kevin , Backman Lavina , Giri Ashutosh , Opila Elizabeth J. , Maria Jon-Paul , Hopkins Patrick E.
Published: October 2017

Time domain thermoreflectance (TDTR) and frequency domain thermoreflectance (FDTR) are common pump-probe techniques that are used to measure the thermal properties of materials. At elevated temperatures, transducers used in these techniques can become limited by melting or other phase transitions. In this work, time domain thermoreflectance is used to determine the viability of HfN thin film transducers grown on SiO2 through measurements of the SiO2 thermal conductivity up to approximately 1000 K. Further, the reliability of HfN as a transducer is determined by measuring the thermal conductivities of MgO, Al2O3, and diamond at room temperature. The thermoreflectance coefficient of HfN was found to be 1.4 × 10−4 K−1 at 800 nm, one of the highest thermoreflectance coefficients measured at this standard TDTR probe wavelength. Additionally, the high absorption of HfN at 400 nm is shown to enable reliable laser heating to elevate the sample temperature during a measurement, relative to other transducers.
Stimulated Raman Adiabatic Passage enables Core-Nonpenetrating Rydberg states to be populated
Authors: Dowd Deborah
Published: October 2017

Researchers demonstrate feasibility of STIRAP for populating Core-Nonpenetrating Rydberg states.
Morphoanatomical characteristics of leaves of Anacardium othonianum seedlings subjected to different nitrogen doses under hydroponic conditions
Authors: Bessa Layara A. , Moreira Marialva A. , Silva Fabiano G. , Vitorino Luciana C. , Rodrigues Cássia L. , Filho Sebastião C. V.
Published: October 2017

Nitrogen is an essential nutrient that plants generally require in large amounts. Knowing the nitrogen dose that stimulates primary and secondary metabolic pathways is important for the management of nitrogen fertilisation in plants in general; however, this information is still unavailable for seedlings of the cerrado cashew tree. Based on the hypothesis that the availability of nitrogen for Anacardium othonianum Rizz. seedlings can affect can affect the development of anatomical structures, as well as the synthesis of secondary metabolism compounds in leaves, an experiment was conducted to determine the qualitative and quantitative anatomy this tissue collected from plants of this species subjected to N doses of 0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 mmol L−1 in nutrient solution and evaluated the effect at 30 and 90 days after transplanting (DAT). The largest leaf morphoanatomical changes were observed under the doses of 0 and 15.0 mmol L−1 of N. The lowest stomatal density being observed in the plants exposed to an N dose of 15 mmol L−1. The level of flavonoids was not influenced by the availability of N in the solution; however, the absence of nitrogen directly affected the accumulation of phenolic compounds, alkaloids and polysaccharides present in the leaves, whereas the doses of 7.5, 10.0 and 12.5 mmol L−1 were essential to stimulate the presence of this latter compound in cerrado-cashew-tree seedlings maintained in nutrient solution. Regarding the epochs of evaluation, effect was observed only for the thickness of the adaxial epidermis. These data confirm the hypothesis that the leaf anatomy as well as the accumulation of secondary metabolism compounds in leaves of A. ohonianum can be modified because of the availability of N to the plant.
Breast tumor cell-specific knockout of
Twist1
inhibits cancer cell plasticity, dissemination, and lung metastasis in mice
Authors: Xu Yixiang , Lee Dong-Kee , Feng Zhen , Xu Yan , Bu Wen , Li Yi , Liao Lan , Xu Jianming
Published: October 2017

Significance

We found that Twist1 is coexpressed with multiple other epithelial–mesenchymal transition (EMT)-inducing transcription factors (TFs) in small subsets of primary and circulating breast tumor cells. Together, they program a partial EMT and a basal-like phenotype of tumor cells, which most likely are responsible for disseminating into the circulation and metastasizing to the lung in mice. Targeting Twist1 largely diminishes all the cellular features and phenotypes of breast tumor cells, indicating Twist1 may be a target for inhibiting breast cancer metastasis. These findings are in favor of the role of partial EMT in breast cancer progression toward the metastatic state.
Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F
1
F
0
-ATP synthase
Authors: Almendro-Vedia Víctor G. , Natale Paolo , Mell Michael , Bonneau Stephanie , Monroy Francisco , Joubert Frederic , López-Montero Iván
Published: October 2017

Significance

The shape of biological membranes is constantly remodeled and maintained out of equilibrium by active proteins. The functional capacity of membrane deformation is mainly determined by the mechanical interplay between protein activity and bending elasticity. In our experiments, we find that ATP synthase, a rotating membrane protein that synthesizes the biochemical energy in cells through proton-pumping activity across the membrane, promotes localized nonequilibrium membrane fluctuations when reconstituted in giant lipid vesicles. The large membrane deformations emerge from the pumping action of rotating proteins clustered at specific emplacements in the membrane. Our results pave the way to new experimental realizations to explore the collective effects of rotating ATP synthases and their possible biological implications for biomembrane organization and protein functionality.
Marine mammal population decline linked to obscured by-catch
Authors: Meyer Stefan , Robertson Bruce C. , Chilvers B. Louise , Krkošek Martin
Published: October 2017

Significance

Declines of marine megafauna such as turtles, pinnipeds, and whales are often related to mortality caused by capture or entanglement in fisheries gear. To help recovery of these species, trawl fisheries have implemented exclusion devices that release nontarget species. Despite decades of use, there has been no empirical evaluation of whether or not exclusion devices aid recovery of affected species. Long-term data on the endangered New Zealand sea lion and a trawl fishery in the Southern Ocean indicate that exclusion devices have paradoxically contributed to ongoing decline rather than recovery. Exclusion devices obscure the postrelease impact of elevated mortality or reproductive failure; meanwhile, reduced levels of reported by-catch may mislead management that continued decline is not associated with fisheries.
UTX-guided neural crest function underlies craniofacial features of Kabuki syndrome
Authors: Shpargel Karl B. , Starmer Joshua , Wang Chaochen , Ge Kai , Magnuson Terry
Published: October 2017

Significance

Several chromatin-modifying enzymes are mutated in human craniofacial disorders. These factors function genome-wide to regulate accessibility and expression of extensive gene sets. Therefore, understanding chromatin-modifier function requires identification of responsible cellular origins and genomic characterization of phenotypes in primary cells. We now combine reporter flow cytometry with low cell number genomics to identify neural crest stem-cell factors as molecular targets of UTX in Kabuki syndrome. UTX demethylates histones to regulate some gene expression, but many UTX-bound regions are subject to novel mechanisms of transcriptional regulation. This study identifies UTX cellular and molecular targets in craniofacial development and this methodology is broadly adaptable to study genome distribution of other chromatin factors in neural crest disorders.
Mechanistic principles underlying regulation of the actin cytoskeleton by phosphoinositides
Authors: Senju Yosuke , Kalimeri Maria , Koskela Essi V. , Somerharju Pentti , Zhao Hongxia , Vattulainen Ilpo , Lappalainen Pekka
Published: October 2017

Significance

Membrane phosphoinositides have emerged as key regulators of the actin cytoskeleton in cell migration, morphogenesis, cytokinesis, and endocytosis. However, the molecular mechanisms by which actin-binding proteins (ABPs) interact with phosphoinositide-rich membranes remain remarkably poorly understood. By applying a combination of biochemical, biophysical, and atomistic molecular dynamics simulation approaches on six central ABPs, we discovered that they employ multivalent electrostatic interactions for membrane binding. Strikingly, our experiments revealed that these proteins display enormous differences in their membrane interaction dynamics and in the ranges of phosphoinositide densities that they sense. These differences precisely correlate with the specific functions of these proteins in cytoskeletal dynamics. These findings uncover molecular principles by which membrane phosphoinositides regulate dynamics and architecture of the actin cytoskeleton in cells.
Selective neutralization of IL-12 p40 monomer induces death in prostate cancer cells via IL-12–IFN-γ
Authors: Kundu Madhuchhanda , Roy Avik , Pahan Kalipada
Published: October 2017

Significance

Different mouse and human cancer cells produce excess p40 monomer compared with p40 homodimer, IL-12, and IL-23. The serum level of p40 monomer is also much higher in patients with prostate cancer than in healthy control subjects. Interestingly, this p40 monomer helps cancer cells to escape IL-12–IFN-γ–mediated death via suppression of IL-12 receptor-β1 internalization. This report demonstrates a biological role of p40 monomer, the so-called nonfunctional member of the IL-12 family of cytokines, in cancer cell survival. These results also delineate that neutralization of p40 monomer may be a therapeutic target in prostate and other cancers, which are associated with excessive production of p40.
Small-molecule inhibitors directly target CARD9 and mimic its protective variant in inflammatory bowel disease
Authors: Leshchiner Elizaveta S. , Rush Jason S. , Durney Michael A. , Cao Zhifang , Dančík Vlado , Chittick Benjamin , Wu Huixian , Petrone Adam , Bittker Joshua A. , Phillips Andrew , Perez Jose R. , Shamji Alykhan F. , Kaushik Virendar K. , Daly Mark J. , Graham Daniel B. , Schreiber Stuart L. , Xavier Ramnik J.
Published: October 2017

Significance

Understanding the genetic basis of human disease can reveal mechanisms of disease pathology and guide the design of novel treatment strategies. Here, we leverage insights from genetic studies to create a blueprint for treatment of inflammatory bowel disease (IBD). We demonstrate the feasibility of using small-molecule inhibitors to recapitulate the antiinflammatory function of
CARD9
mutations associated with protection from IBD.
Opioid and orexin hedonic hotspots in rat orbitofrontal cortex and insula
Authors: Castro Daniel C. , Berridge Kent C.
Published: October 2017

Significance

Orbitofrontal cortex, insula, and related cortical regions are implicated in pleasure and motivation. However, determining whether cortical sites help cause hedonic reactions or instead merely encode signals generated elsewhere to facilitate other functions such as cognition remains unresolved. By mapping hedonic effects of individual drug microinjections, we generate detailed anatomical maps for potential gain-of-function affective sites in rat limbic cortex. Here, we show that opioid or orexin stimulations in orbitofrontal cortex and insula causally enhance hedonic “liking” reactions to sweetness and find a third cortical site where the same neurochemical stimulations reduce positive hedonic impact. For comparison, we also map overlapping but separable regions where stimulations increase the motivation to eat.
M344 promotes nonamyloidogenic amyloid precursor protein processing while normalizing Alzheimer’s disease genes and improving memory
Authors: Volmar Claude-Henry , Salah-Uddin Hasib , Janczura Karolina J. , Halley Paul , Lambert Guerline , Wodrich Andrew , Manoah Sivan , Patel Nidhi H. , Sartor Gregory C. , Mehta Neil , Miles Nancy T. H. , Desse Sachi , Dorcius David , Cameron Michael D. , Brothers Shaun P. , Wahlestedt Claes
Published: October 2017

Significance

Hundreds of failed clinical trials with Alzheimer’s disease (AD) patients over the last fifteen years demonstrate that the one-target–one-disease approach is not effective in AD. In silico, structure-based, multitarget drug design approaches to treat multifactorial diseases have not been successful in the context of AD either. Here, we show that M344, an inhibitor of class I and IIB histone deacetylases, affects multiple AD-related genes, including those related to both early- and late-onset AD. We also show that M344 improves memory in the 3xTg AD mouse model. This work endorses a shift to a multitargeted approach to the treatment of AD, supporting the therapeutic potential of a single small molecule with an epigenetic mechanism of action.
PAF promotes stemness and radioresistance of glioma stem cells
Authors: Ong Derrick Sek Tong , Hu Baoli , Ho Yan Wing , Sauvé Charles-Etienne Gabriel , Bristow Christopher A. , Wang Qianghu , Multani Asha S. , Chen Peiwen , Nezi Luigi , Jiang Shan , Gorman Claire Elizabeth , Monasterio Marta Moreno , Koul Dimpy , Marchesini Matteo , Colla Simona , Jin Eun-Jung , Sulman Erik P. , Spring Denise J. , Yung Wai-Kwan Alfred , Verhaak Roel G. W. , Chin Lynda , Wang Y. Alan , DePinho Ronald A.
Published: October 2017

Significance

Glioblastoma multiforme (GBM) is uniformly lethal and shows resistance to all forms of therapy. Glioma stem cells (GSCs) have been shown to support GBM maintenance and exhibit enhanced resistance to ionizing radiation, a cornerstone of GBM therapy. This study establishes that proliferating cell nuclear antigen-associated factor (PAF) depletion profoundly reduces GSC frequency and tumorigenicity, in part, by down-regulating DNA replication and pyrimidine metabolism. Moreover, PAF depletion impairs error-prone DNA translesion synthesis (TLS) and enhances sensitivity of GSCs to radiation treatment. Pharmacological impairment of DNA replication and TLS diminished GSC maintenance and radioresistance, illuminating a potential GBM treatment strategy of combined TLS inhibition and radiation therapy.