bluuebunny/crossref_metadata_2025 huggingface dataset:
Terahertz electron cyclotron maser interactions with an axis-encircling electron beam
Authors: Li G. D. , Kao S. H. , Chang P. C. , Chu K. R.
Published: April 2015

To generate terahertz radiation via the electron cyclotron maser instability, harmonic interactions are essential in order to reduce the required magnetic field to a practical value. Also, high-order mode operation is required to avoid excessive Ohmic losses. The weaker harmonic interaction and mode competition associated with an over-moded structure present challenging problems to overcome. The axis-encircling electron beam is a well-known recipe for both problems. It strengthens the harmonic interaction, as well as minimizing the competing modes. Here, we examine these advantages through a broad data base obtained for a low-power, step-tunable, gyrotron oscillator. Linear results indicate far more higher-harmonic modes can be excited with an axis-encircling electron beam than with an off-axis electron beam. However, multi-mode, time-dependent simulations reveal an intrinsic tendency for a higher-harmonic mode to switch over to a lower-harmonic mode at a high beam current or upon a rapid current rise. Methods are presented to identify the narrow windows in the parameter space for stable harmonic interactions.
The polarized Debye sheath effect on Kadomtsev-Petviashvili electrostatic structures in strongly coupled dusty plasma
Authors: Shahmansouri M. , Alinejad H.
Published: April 2015

We give a theoretical investigation on the dynamics of nonlinear electrostatic waves in a strongly coupled dusty plasma with strong electrostatic interaction between dust grains in the presence of the polarization force (i.e., the force due to the polarized Debye sheath). Adopting a reductive perturbation method, we derived a three-dimensional Kadomtsev-Petviashvili equation that describes the evolution of weakly nonlinear electrostatic localized waves. The energy integral equation is used to study the existence domains of the localized structures. The analysis provides the localized structure existence region, in terms of the effects of strong interaction between the dust particles and polarization force.
Mechanisms of template-assisted selective epitaxy of InAs nanowires on Si
Authors: Borg Mattias , Schmid Heinz , Moselund Kirsten E. , Cutaia Davide , Riel Heike
Published: April 2015

A comprehensive investigation of InAs epitaxy on silicon using template-assisted selective epitaxy is presented. The variation in axial growth rate of InAs nanowires inside oxide nanotube templates is studied as function of nanotube diameter (20–140 nm), growth time (0–30 min), growth temperature (520–580 °C), V/III ratio (40–160), nanotube spacing (300–2000 nm), and substrate crystal orientation. It is found that the effective V/III ratio is reduced at least by a factor of two within the nanotube templates compared to the outside, detectable by changes in the growth facet morphology. The reduced V/III ratio originates from the different transport mechanisms for the As and In precursor species; As and In species are both transported by Knudsen diffusion in the vapor, but an additional contribution of In surface diffusion reduces the V/III ratio. The results reveal the interplay of growth parameters, crystal facets and template geometry and thus are generally applicable for nanoscale selective epitaxy.
Novel pre-alloyed powder processing of modified alnico 8: Correlation of microstructure and magnetic properties
Authors: Anderson I. E. , Kassen A. G. , White E. M. H. , Zhou L. , Tang W. , Palasyuk A. , Dennis K. W. , McCallum R. W. , Kramer M. J.
Published: April 2015

Progress is reviewed on development of an improved near-final bulk magnet fabrication process for alnico 8, as a non-rare earth permanent magnet with promise for sufficient energy density and coercivity for electric drive motors. This study showed that alnico bulk magnets in near-final shape can be made by simple compression molding from spherical high purity gas atomized pre-alloyed powder. Dwell time at peak sintering temperature (1250 °C) greatly affected grain size of the resulting magnet alloys. This microstructure transformation was demonstrated to be useful for gaining partially aligned magnetic properties and boosting energy product. While a route to increased coercivity was not identified by these experiments, manufacturability of bulk alnico magnet alloys in near-final shapes was demonstrated, permitting further processing and alloy modification experiments that can target higher coercivity and better control of grain anisotropy during grain growth.
An ultra-compact, high-throughput molecular beam epitaxy growth system
Authors: Baker A. A. , Braun W. , Gassler G. , Rembold S. , Fischer A. , Hesjedal T.
Published: April 2015

We present a miniaturized molecular beam epitaxy (miniMBE) system with an outer diameter of 206 mm, optimized for flexible and high-throughput operation. The three-chamber system, used here for oxide growth, consists of a sample loading chamber, a storage chamber, and a growth chamber. The growth chamber is equipped with eight identical effusion cell ports with linear shutters, one larger port for either a multi-pocket electron beam evaporator or an oxygen plasma source, an integrated cryoshroud, retractable beam-flux monitor or quartz-crystal microbalance, reflection high energy electron diffraction, substrate manipulator, main shutter, and quadrupole mass spectrometer. The system can be combined with ultrahigh vacuum (UHV) end stations on synchrotron and neutron beamlines, or equivalently with other complex surface analysis systems, including low-temperature scanning probe microscopy systems. Substrate handling is compatible with most UHV surface characterization systems, as the miniMBE can accommodate standard surface science sample holders. We introduce the design of the system, and its specific capabilities and operational parameters, and we demonstrate the epitaxial thin film growth of magnetoelectric Cr2O3 on c-plane sapphire and ferrimagnetic Fe3O4 on MgO (001).
Vibrational dynamics of azide-derivatized amino acids studied by nonlinear infrared spectroscopy
Authors: Okuda Masaki , Ohta Kaoru , Tominaga Keisuke
Published: April 2015

Recently, biomolecules which are labeled by azide or thiocyanate groups in solutions and proteins have been studied to examine microscopic environment around a solute by nonlinear infrared (IR) spectroscopy. In this study, we have performed two-dimensional infrared (2D-IR) spectroscopy to investigate the vibrational frequency fluctuations of two different azide-derivatized amino acids, Ala (N3-Ala) and Pro (N3-Pro), and N3− in water. From the 2D-IR experiments, it was found that the frequency-frequency time correlation function (FFTCF) of solute can be modeled by a delta function plus an exponential function and constant. FFTCF for each probe molecule has a decay component of about 1 ps, and this result suggests that the stretching mode of the covalently bonded azide group is sensitive to the fluctuations of hydrogen bond network system, as found in previous studies of N3− in water. In contrast to FFTCF of N3−, FFTCF of the azide-derivatized amino acids contains static component. This static component may reflect dynamics of water affected by the solutes or the structural fluctuations of the solute itself. We also performed the IR pump-probe measurements for the probe molecules in water in order to investigate vibrational energy relaxation (VER) and reorientational relaxation. It was revealed that the charge fluctuations in the azide group are significant for the VER of this mode in water, reflecting that the VER rate of N3− is faster than those of the azide-derivatized amino acids. While the behaviors of the anisotropy decay of N3-Ala and N3− are similar to each other, the anisotropy decay of N3-Pro contains much slower decaying component. By considering the structural difference around the vibrational probe between N3-Ala and N3-Pro, it is suggested that the structural freedom of the probe molecules can affect the reorientational processes.
Equation-of-motion coupled-cluster method for doubly ionized states with spin-orbit coupling
Authors: Wang Zhifan , Hu Shu , Wang Fan , Guo Jingwei
Published: April 2015

In this work, we report implementation of the equation-of-motion coupled-cluster method for doubly ionized states (EOM-DIP-CC) with spin-orbit coupling (SOC) using a closed-shell reference. Double ionization potentials (DIPs) are calculated in the space spanned by 2h and 3h1p determinants with the EOM-DIP-CC approach at the CC singles and doubles level (CCSD). Time-reversal symmetry together with spatial symmetry is exploited to reduce computational effort. To circumvent the problem of unstable dianion references when diffuse basis functions are included, nuclear charges are scaled. Effect of this stabilization potential on DIPs is estimated based on results from calculations using a small basis set without diffuse basis functions. DIPs and excitation energies of some low-lying states for a series of open-shell atoms and molecules containing heavy elements with two unpaired electrons have been calculated with the EOM-DIP-CCSD approach. Results show that this approach is able to afford a reliable description on SOC splitting. Furthermore, the EOM-DIP-CCSD approach is shown to provide reasonable excitation energies for systems with a dianion reference when diffuse basis functions are not employed.
Uniform asymptotics of area-weighted Dyck paths
Authors: Haug Nils , Prellberg Thomas
Published: April 2015

Using the generalized method of steepest descents for the case of two coalescing saddle points, we derive an asymptotic expression for the bivariate generating function of Dyck paths, weighted according to their length and their area in the limit of the area generating variable tending towards 1. The result is valid uniformly for a range of the length generating variable, including the tricritical point of the model.
Spontaneous domain nucleation under in-plane fields in ultrathin films with Dzyaloshinskii-Moriya interaction
Authors: Agrawal Parnika , Bauer Uwe , Beach Geoffrey S. D.
Published: April 2015

In this paper, we show that applying a hard axis field reduces the energy barrier for the spontaneous formation of a multi-domain state in magnetic ultrathin films sandwiched between a heavy metal and an oxide. This provides a simple technique to generate a metastable multi-domain state in magnetic films where the ground state is uniform. This approach could be particularly interesting in materials with strong Dzyaloshinskii-Moriya interaction as a means to realize metastable chiral textures.
Experimental and theoretical study of the HXeI⋯HCl and HXeI⋯HCCH complexes
Authors: Zhu Cheng , Tsuge Masashi , Räsänen Markku , Khriachtchev Leonid
Published: April 2015

The HXeI⋯HCl and HXeI⋯HCCH complexes are studied computationally and experimentally in a Xe matrix. In the experiments, three bands of the HXeI⋯HCl complex and one band of the HXeI⋯HCCH complex in the H–Xe stretching region are observed. The monomer-to-complex shifts are +94, +111, and +155 cm−1 for the HXeI⋯HCl complex and +49 cm−1 for the HXeI⋯HCCH complex. The bands of the complexed HCl molecules are also observed with large red shifts from the HCl monomer (−187, −252, and −337 cm−1). The ab initio calculations at the CCSD(T)/def2-TZVPPD level of theory predict two stable structures for the HXeI⋯HCl complex with interaction energies of −3.72 and −0.28 kcal mol−1 and one structure for the HXeI⋯HCCH complex with an interaction energy of −2.67 kcal mol−1 and the calculated monomer-to-complex shifts are in a good agreement with experiment (in the case of HXeI⋯HCl, for the stronger structure). The HXeI molecules are decomposed by broad-band infrared light; however, the decomposition is much more efficient for the HXeI monomer than for the complexes studied here as well as for the previously studied HXeI⋯HI and HXeI⋯HBr complexes. In fact, the decomposition efficiency decreases as the monomer-to-complex shift of the H–Xe stretching mode increases.
Towards an on-chip platform for the controlled application of forces via magnetic particles: A novel device for mechanobiology
Authors: Monticelli M. , Albisetti E. , Petti D. , Conca D. V. , Falcone M. , Sharma P. P. , Bertacco R.
Published: April 2015

In-vitro tests and analyses are of fundamental importance for investigating biological mechanisms in cells and bio-molecules. The controlled application of forces to activate specific bio-pathways and investigate their effects, mimicking the role of the cellular environment, is becoming a prominent approach in this field. In this work, we present a non-invasive magnetic on-chip platform which allows for the manipulation of magnetic particles, through micrometric magnetic conduits of Permalloy patterned on-chip. We show, from simulations and experiments, that this technology permits to exert a finely controlled force on magnetic beads along the chip surface. This force can be tuned from few to hundreds pN by applying a variable external magnetic field.
Hopkins-Skellam index and origin of spatial regularity in InAs quantum dot formation on GaAs(001)
Authors: Konishi Tomoya , Bell Gavin R. , Tsukamoto Shiro
Published: April 2015

We investigate the origin of the spatial regularity of arrays of InAs quantum dots (QDs) grown on GaAs(001). The Hopkins-Skellam index (HSI) is used with a newly developed calculation algorithm to quantify the spatial regularity both of QDs and of nm-sized surface reconstruction territories (SRTs) present in the InxGa1−xAs wetting layer prior to QD nucleation. The SRT is the minimum extent of a surface reconstruction region needed for one QD to nucleate. By computing the evolving HSI of SRTs from sequences of in situ scanning tunnelling microscopy images during growth, we find that the spatial regularity of QDs is traced back to that of the (n × 3) SRTs as early as 0.6 monolayers of InAs coverage. This regularity is disturbed by the (n × 4) SRTs which appear at higher coverage. The SRT approach is discussed in comparison to conventional capture zone theories of surface growth.
Low frequency 2D Raman-THz spectroscopy of ionic solution: A simulation study
Authors: Pan Zhijun , Wu Tianmin , Jin Tan , Liu Yong , Nagata Yuki , Zhang Ruiting , Zhuang Wei
Published: April 2015

The 2D Raman-THz spectrum of the MgCl2 solution was simulated using the molecular dynamics simulation and the stability matrix method and compared with that of the pure water. The 2D Raman-THz signal provides more information on the ion effects on the collective water motion than the conventional 1D signal. The presence of MgCl2 suppresses the cross peak of water between the hydrogen bond bending and the other intermolecular vibrational mode, which clearly illustrates that the water hydrogen bending motion is affected by the confining effect of the ions. Our theoretical work thus demonstrates that the 2D Raman-THz technique can become a valuable nonlinear vibrational probe for the molecular dynamics in the ionic solutions.
The design of a correlation electron cyclotron emission system on J-TEXT
Authors: Yang Z. J. , Xiao Y. , Ma X. D. , Pan X. M. , Xiao J. S.
Published: April 2015

To study the anomalous transport, a correlation electron cyclotron emission (CECE) was planned to be developed on J-TEXT for electron temperature fluctuation measurement. The spectral decorrelation method was employed for the CECE system. It was developed based on the previous 16-channel electron cyclotron emission system. They shared the optical transmission line and mixer. The CECE part consists of 4 channels. Two fixed frequency narrow band filters were used for two channels and two yttrium iron garnet (YIG) filters for the other two channels. To meet the measuring requirement, some tests have been taken for the YIG filters. The results show good performance of the filters. Gaussian optics is used to produce a good poloidal resolution. Wavenumbers resolved by the CECE diagnostic are kθ ≤ 1.5 rad/cm and kr ≤ 12 rad/cm. Some preliminary experiment results are also presented in this paper.
The distribution of ion orbit loss fluxes of ions and energy from the plasma edge across the last closed flux surface into the scrape-off layer
Authors: Stacey Weston M. , Schumann Matthew T.
Published: April 2015

A more detailed calculation strategy for the evaluation of ion orbit loss of thermalized plasma ions in the edge of tokamaks is presented. In both this and previous papers, the direct loss of particles from internal flux surfaces is calculated from the conservation of canonical angular momentum, energy, and magnetic moment. The previous result that almost all of the ion energy and particle fluxes crossing the last closed flux surface are in the form of ion orbit fluxes is confirmed, and the new result that the distributions of these fluxes crossing the last closed flux surface into the scrape-off layer are very strongly peaked about the outboard midplane is demonstrated. Previous results of a preferential loss of counter current particles leading to a co-current intrinsic rotation peaking just inside of the last closed flux surface are confirmed. Various physical details are discussed.
Direct-drive cryogenic-target implosion experiments on SGIII prototype laser facility
Authors: Pu Yudong , Huang Tianxuan , Lei Haile , Li Ping , Zhang Xin , Zheng Jiahua , Yang Zhiwen , Tang Qi , Song Zifeng , Yang Jiamin , Liu Shenye , Jiang Shaoen , Ding Yongkun
Published: April 2015

Directly driven cryogenic target implosion experiments are performed on the SGIII prototype laser facility. X-ray pinhole images reveal frozen condensation on the sealing film. The influence of the condensation on the delivery of laser energy to the capsule surface is then quantified experimentally. It is found that, with a carefully chosen pre-pulse duration, the influence can be reduced, and the neutron yield is increased by an order of magnitude. Subsequently, the cryogenic layered capsule and cryogenic gas-filled capsule are imploded using 6.5-kJ laser energy. The implosion performance is characterized by the neutron yield, the 2D self-emission images of the in-flight shell, and the primary proton spectrum. The neutron yield is 2 × 107 for the gas-filled capsule and 2.8 × 107 for the layered capsule. The 2D self-emission images of the in-flight shell exhibit significant implosion asymmetry. The energy downshift of the proton spectrum is used to infer the areal density. For the gas-filled capsule, the spectrum is downshifted by 0.1 MeV, yielding an areal density of 1–3 mg/cm2. For the layered capsule, the spectrum is downshifted by 0.5 MeV, yielding an areal density of 4–6 mg/cm2. Improving the implosion symmetry would help to further increase the areal density.
Exchange coupling in hybrid anisotropy magnetic multilayers quantified by vector magnetometry
Authors: Morrison C. , Miles J. J. , Anh Nguyen T. N. , Fang Y. , Dumas R. K. , Åkerman J. , Thomson T.
Published: April 2015

Hybrid anisotropy thin film heterostructures, where layers with perpendicular and in-plane anisotropy are separated by a thin spacer, are novel materials for zero/low field spin torque oscillators and bit patterned media. Here, we report on magnetization reversal and exchange coupling in a archetypal Co/Pd (perpendicular)-NiFe (in-plane) hybrid anisotropy system studied using vector vibrating sample magnetometry. This technique allows us to quantify the magnetization reversal in each individual magnetic layer, and measure of the interlayer exchange as a function of non-magnetic spacer thickness. At large (>1 nm) spacer thicknesses Ruderman-Kittel-Kasuya-Yosida-like exchange dominates, with orange-peel coupling providing a significant contribution only for sub-nm spacer thickness.
Robust dynamic mitigation of instabilities
Authors: Kawata S. , Karino T.
Published: April 2015

A dynamic mitigation mechanism for instability growth was proposed and discussed in the paper [S. Kawata, Phys. Plasmas 19, 024503 (2012)]. In the present paper, the robustness of the dynamic instability mitigation mechanism is discussed further. The results presented here show that the mechanism of the dynamic instability mitigation is rather robust against changes in the phase, the amplitude, and the wavelength of the wobbling perturbation applied. Generally, instability would emerge from the perturbation of the physical quantity. Normally, the perturbation phase is unknown so that the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superposition of perturbations imposed actively: If the perturbation is induced by, for example, a driving beam axis oscillation or wobbling, the perturbation phase could be controlled, and the instability growth is mitigated by the superposition of the growing perturbations.
Zero photoelastic and water durable ZnO–SnO–P2O5–B2O3 glasses
Authors: Saitoh Akira , Nakata Kohei , Tricot Grégory , Chen Yuanyuan , Yamamoto Naoki , Takebe Hiromichi
Published: April 2015

We report properties of zero birefringent xZnO–(67–x)SnO–(33–y)P2O5–y B2O3 glasses, within 18.5 ≤ x ≤ 22 and y = 0, 3, and 10 mol. %. These compositions of boro-phosphate glasses provide both zero photoelastic constant (PEC) and improved water durability. x = 19 and y = 3 compositions show minimum PEC of −0.002 × 10−12 Pa−1, which can contribute to candidate material for fiber current sensor devise without lead. The structures of zero photoelastic glasses were investigated by Raman scattering and nuclear magnetic resonance spectroscopies. Compositions of zero PEC glasses are explained by the empirical model proposed by Zwanziger et al. [Chem. Mater. 19, 286-290 (2007)].
Radiation tolerant nanocrystalline ZrN films under high dose heavy-ion irradiations
Authors: Jiao L. , Yu K. Y. , Chen D. , Jacob C. , Shao L. , Zhang X. , Wang H.
Published: April 2015

ZrN, a refractory ceramic material, finds many potential applications in advanced nuclear reactors. However, the grain size dependent radiation response in nanocrystalline (nc) ZrN under high dose heavy ion irradiation has not yet been studied to date. Here, we compare the radiation response of nc-ZrN films (with a respective average grain size of ∼9 and 31 nm) to Fe2+ ion irradiations up to a damage level of 10 displacements-per-atom (dpa). The ZrN film with the average grain size of 9 nm shows prominently enhanced radiation tolerance as evidenced by suppressed grain growth, alleviated radiation softening, as well as reduced variation in electrical resistivity. In contrast, ZrN with the larger average grain size of 31 nm shows prominent radiation softening and resistivity increase, attributed to the high density of defect cluster formed inside the grains. The influence of grain boundaries on enhanced irradiation tolerance in nc-ZrN is discussed.
Molecular photoelectron angular distribution rotations in multi-photon resonant ionization of H2+ by circularly polarized ultraviolet laser pulses
Authors: Yuan Kai-Jun , Chelkowski Szczepan , Bandrauk André D.
Published: April 2015

We study effects of pulse durations on molecular photoelectron angular distributions (MPADs) in ultrafast circular polarization ultraviolet resonant ionization processes. Simulations performed on aligned H2+ by numerically solving time dependent Schrödinger equations show rotations of MPADs with respect to the molecular symmetry axes. It is found that in multi-photon resonant ionization processes, rotation angles are sensitive to pulse durations, which we attribute to the coherent resonant excitation between the ground state and the intermediate excited electronic state induced by Rabi oscillations. Multi-photon nonresonant and single photon ionization processes are simulated and compared which exhibit a constant rotation angle. An asymmetry parameter is introduced to describe the pulse duration sensitivity by perturbation theory models. Influence of pulse frequency detunings on MPADs is also investigated where oscillations of rotations are absent at long pulse durations due to nonresonance excitation.
Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films
Authors: Luk Ting S. , de Ceglia Domenico , Liu Sheng , Keeler Gordon A. , Prasankumar Rohit P. , Vincenti Maria A. , Scalora Michael , Sinclair Michael B. , Campione Salvatore
Published: April 2015

We experimentally demonstrate efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10−6 is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.
Simulation of injector dynamics during steady inductive helicity injection current drive in the HIT-SI experiment
Authors: Hansen C. , Marklin G. , Victor B. , Akcay C. , Jarboe T.
Published: April 2015

We present simulations of inductive helicity injection in the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI) device that treats the entire plasma volume in a single dynamic MHD model. A new fully 3D numerical tool, the PSI-center TETrahedral mesh code, was developed that provides the geometric flexibility required for this investigation. Implementation of a zero-β Hall MHD model using PSI-TET will be presented including formulation of a new self-consistent magnetic boundary condition for the wall of the HIT-SI device. Results from simulations of HIT-SI are presented focusing on injector dynamics that are investigated numerically for the first time. Asymmetries in the plasma loading between the two helicity injectors and progression of field reversal in each injector are observed. Analysis indicates cross-coupling between injectors through confinement volume structures. Injector impedance is found to scale with toroidal current at fixed density, consistent with experimental observation. Comparison to experimental data with an injector drive frequency of 14.5 kHz shows good agreement with magnetic diagnostics. Global mode structures from Bi-Orthogonal decomposition agree well with experimental data for the first four modes.
Nonlinear delayed symmetry breaking in a solid excited by hard x-ray free electron laser pulses
Authors: Ferrer A. , Johnson J. A. , Huber T. , Mariager S. O. , Trant M. , Grübel S. , Zhu D. , Chollet M. , Robinson J. , Lemke H. T. , Ingold G. , Milne C. , Staub U. , Beaud P. , Johnson S. L.
Published: April 2015

We have studied the ultrafast changes of electronic states in bulk ZnO upon intense hard x-ray excitation from a free electron laser. By monitoring the transient anisotropy induced in an optical probe beam, we observe a delayed breaking of the initial c-plane symmetry of the crystal that lasts for several picoseconds. Interaction with the intense x-ray pulses modifies the electronic state filling in a manner inconsistent with a simple increase in electronic temperature. These results may indicate a way to use intense ultrashort x-ray pulses to investigate high-energy carrier dynamics and to control certain properties of solid-state materials.
Development of low-fluorescence thick photoresist for high-aspect-ratio microstructure in bio-application
Authors: Tamai H. , Maruo K. , Ueno H. , Terao K. , Kotera H. , Suzuki T.
Published: April 2015

In this study, we propose and evaluate a novel low-auto-fluorescence photoresist (SJI photoresist) for bio-application, e.g., in gene analysis and cell assay. The spin-coated SJI photoresist has a wide thickness range of ten to several hundred micrometers, and photoresist microstructures with an aspect ratio of over 7 and micropatterns of less than 2 μm are successfully fabricated. The emission spectrum intensity of the SJI photoresist is found to be over 80% less than that of the widely used SU-8 photoresist. To evaluate the validity of using the proposed photoresist in bio-application for fluorescence observation, we demonstrate a chromosome extension device composed of the SJI photoresist. The normalized contrast ratio of the SJI photoresist exhibits a 50% improvement over that of the SU-8 photoresist; thus, the SJI photoresist is a versatile tool for bio-application.
Ferromagnetism in Ti-doped ZnO thin films
Authors: Shao Q. , Wang C. , Zapien J. A. , Leung C. W. , Ruotolo A.
Published: April 2015

We report our study on the origin of ferromagnetism in Ti-doped ZnO. A series of Ti doped ZnO films with increasing concentration of Ti dopant were grown and characterized in terms of structural, electrical, and magnetic properties. We found that Ti has a low solubility in the ZnO wurtzite structure. This favors stabilization of a large number of Zn vacancies, and theoretical calculations have shown that they can carry substantial magnetic moment. A carrier mediated exchange interaction between Zn vacancies is at the origin of the surprisingly high magnetic moment we measure in this compound.
Study of non-contact measurement of the thermal expansion coefficients of materials based on laser feedback interferometry
Authors: Zheng Fasong , Tan Yidong , Lin Jing , Ding Yingchun , Zhang Shulian
Published: April 2015

The noncooperative and ultrahigh sensitive length measurement approach is of great significance to the study of a high-precision thermal expansion coefficient (TEC) determination of materials at a wide temperature range. The novel approach is presented in this paper based on the Nd:YAG microchip laser feedback interferometry with 1064 nm wavelength, the beam frequency of which is shifted by a pair of acousto-optic modulators and then the heterodyne phase measurement technique is used. The sample is placed in a muffle furnace with two coaxial holes opened on the opposite furnace walls. The measurement beams are perpendicular and coaxial on each surface of the sample, the configuration which can not only achieve the length measurement of sample but also eliminate the influence of the distortion of the sample supporter. The reference beams inject on the reference mirrors which are put as possible as near the holes, respectively, to eliminate the air disturbances and the influence of thermal lens effect out of the furnace chamber. For validation, the thermal expansion coefficients of aluminum and steel 45 samples are measured from room temperature to 748 K, which proved measurement repeatability of TECs is better than 0.6 × 10−6(K−1) at the range of 298 K–598 K and the high-sensitive non-contact measurement of the low reflectivity surface induced by the oxidization of the samples at the range of 598 K–748 K.
A tunable microwave slot antenna based on graphene
Authors: Dragoman Mircea , Neculoiu Dan , Bunea Alina-Cristina , Deligeorgis George , Aldrigo Martino , Vasilache D. , Dinescu A. , Konstantinidis George , Mencarelli Davide , Pierantoni Luca , Modreanu M.
Published: April 2015

The paper presents the experimental and modeling results of a microwave slot antenna in a coplanar configuration based on graphene. The antennas are fabricated on a 4 in. high-resistivity Si wafer, with a ∼300 nm SiO2 layer grown through thermal oxidation. A CVD grown graphene layer is transferred on the SiO2. The paper shows that the reflection parameter of the antenna can be tuned by a DC voltage. 2D radiation patterns at various frequencies in the X band (8–12 GHz) are then presented using as antenna backside a microwave absorbent and a metalized surface. Although the radiation efficiency is lower than a metallic antenna, the graphene antenna is a wideband antenna while the metal antennas with the same geometry and working at the same frequencies are narrowband.
Uniaxially oriented polycrystalline thin films and air-stable n-type transistors based on donor-acceptor semiconductor (diC8BTBT)(FnTCNQ) [n = 0, 2, 4]
Authors: Shibata Yosei , Tsutsumi Jun'ya , Matsuoka Satoshi , Matsubara Koji , Yoshida Yuji , Chikamatsu Masayuki , Hasegawa Tatsuo
Published: April 2015

We report the fabrication of high quality thin films for semiconducting organic donor-acceptor charge-transfer (CT) compounds, (diC8BTBT)(FnTCNQ) (diC8BTBT = 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene and FnTCNQ [n = 0,2,4] = fluorinated derivatives of 7,7,8,8,-tetracyanoquinodimethane), which have a high degree of layered crystallinity. Single-phase and uniaxially oriented polycrystalline thin films of the compounds were obtained by co-evaporation of the component donor and acceptor molecules. Organic thin-film transistors (OTFTs) fabricated with the compound films exhibited n-type field-effect characteristics, showing a mobility of 6.9 × 10−2 cm2/V s, an on/off ratio of 106, a sub-threshold swing of 0.8 V/dec, and an excellent stability in air. We discuss the suitability of strong intermolecular donor–acceptor interaction and the narrow CT gap nature in compounds for stable n-type OTFT operation.
A broadband terahertz absorber using multi-layer stacked bars
Authors: Liu Shuo , Chen Haibing , Cui Tie Jun
Published: April 2015

We present the simulation, implementation, and measurement of a broadband terahertz (THz) metamaterial absorber. By stacking 12 metallic bars of varying lengths on three polyimide layers with equal spacing, a broadband absorption spectrum is formed through merging multiple successive resonance peaks. The measured total absorption exceeds 95% from 0.81 to 1.32 THz at the normal incidence and the full width at half maximum is 64% (from 0.76 to 1.48 THz). The absorption decreases with fluctuations as the incident angle increases but remains above 62% even at the incident angle of 40°. The physical explanation to the absorption mechanism is presented and verified by a 9-bar example, which exhibits narrower absorption bandwidth. It is also experimentally demonstrated that the proposed structure is robust against misalignment of each metallic layer.
Carbon quantum dots coated BiVO4 inverse opals for enhanced photoelectrochemical hydrogen generation
Authors: Nan Feng , Kang Zhenhui , Wang Junling , Shen Mingrong , Fang Liang
Published: April 2015

Carbon quantum dots (CQDs) coated BiVO4 inverse opal (io-BiVO4) structure that shows dramatic improvement of photoelectrochemical hydrogen generation has been fabricated using electrodeposition with a template. The io-BiVO4 maximizes photon trapping through slow light effect, while maintaining adequate surface area for effective redox reactions. CQDs are then incorporated to the io-BiVO4 to further improve the photoconversion efficiency. Due to the strong visible light absorption property of CQDs and enhanced separation of the photoexcited electrons, the CQDs coated io-BiVO4 exhibit a maximum photo-to-hydrogen conversion efficiency of 0.35%, which is 6 times higher than that of the pure BiVO4 thin films. This work is a good example of designing composite photoelectrode by combining quantum dots and photonic crystal.
Stochastic D-bifurcation for a damped sine-Gordon equation with noise
Authors: Huang Qiongwei , Xue Changfeng , Tang Jiashi
Published: April 2015

We investigate the stochastic bifurcation of a damped sine-Gordon equation with Dirichlet boundary conditions under the influence of multiplicative Gaussian white noise. Introducing a slow time scale, we derive the amplitude equations near the trivial solution by multiscale analysis. And the stationary probability density functions are formulated analytically using the stochastic averaging of energy envelope. The numerical calculations show that the system undergoes a stochastic D-bifurcation of energy envelope from a delta measure to new stationary measures when the control parameter crosses a critical point.
Saline water irrigation of quinoa (Chenopodium quinoa) under Mediterranean conditions
Authors: Yazar Attila , Incekaya Çigdem , Sezen S. Metin , Jacobsen Sven-Erik
Published: April 2015

Field experiments were set up in order to evaluate the yield response of quinoa (Chenopodium quinoa Willd. cv. Titicaca) to irrigation with saline and fresh water under Mediterranean climate from 2010 to 2012 in Adana, Turkey. Irrigation treatments in 2010 and 2011 comprised full irrigation with fresh water, full irrigation with saline water of different salt concentrations (40, 30, 20, 10 dS m–1), deficit irrigations with fresh water (50%, 75% of full irrigation), partial root-zone drying, and deficit irrigation with saline water of 40 dS m–1 (50%). In 2012, in addition to the full irrigation treatments, two deficit irrigation levels of 67% and 33% of full irrigation with fresh or saline (30, 20, 10 dS m–1) water were considered. The results indicated that grain yields were slightly reduced by irrigation water salinity up to 30 dS m–1 compared with fresh water irrigation. Salinity and drought stress together interfered considerably with crop grain and biomass yields. However, salinity stress alone did not interfere with grain and biomass yield significantly; therefore, quinoa may be defined as a crop tolerant to salinity. Yield parameters such as aboveground biomass, seed yield and harvest index suggested a good adaptation of quinoa cv. Titicaca to Mediterranean environments.
Heavy metal soil pollution is influenced by the location of green spaces within urban settings
Authors: Curran-Cournane Fiona , Lear Gavin , Schwendenmann Luitgard , Khin Jade
Published: April 2015

Heavy metals are naturally present in soils but are significantly altered by anthropogenic activity which can pose both environmental and human health risks. Sixty green space reserves were chosen in New Zealand’s largest city and separated into six site categories to determine the influence of site location, soil depth, underlying substrate, canopy cover, and distance from roads and central business district on soil heavy metals. Soils in native urban forests had the lowest pools (g m–2) of heavy metals compared with green spaces close to high-traffic, park, school, industrial and residential areas. Least variability in heavy metals was determined among forest sites, with variability increasing in the order: residential, school, industrial, park, and high-traffic sites. Using forest sites as a baseline, a ‘pollution index’ (PI) was established and deemed high for nickel, cadmium and copper and moderate for arsenic, zinc, chromium, lead and mercury. The mean ‘integrated’ PI was high at 3.3 (range 0.3–9.3), indicating elevated levels of soil pollution. The PI was considered a useful technique for interpreting data and complemented traditional ways of reporting concentrations of heavy metals through use of soil pools, which has been limited to date. This study provides important heavy metal data for use in determining where resources may be required to mitigate future risk of increased soil pollution.
Effects of feeding outer bran fraction of rice on lipid accumulation and fecal excretion in rats
Authors: Ijiri Daichi , Nojima Tsutomu , Kawaguchi Mana , Yamauchi Yoko , Fujita Yoshikazu , Ijiri Satoru , Ohtsuka Akira
Published: April 2015

Outer bran fraction of rice (OBFR) contains higher concentrations of crude fiber, γ-oryzanol, and phytic acid compared to whole rice bran (WRB). In this study, we examined the effects of feeding OBFR on lipid accumulation and fecal excretion in rats. Twenty-one male rats at seven-week-old were divided into a control group and two treatment groups. The control group was fed a control diet, and the treatment groups were fed OBFR- or WRB-containing diet for 21 days. There was no significant difference in growth performance. Feeding OBFR diet increased fecal number and weight accompanied by increased fecal lipid content, while it did not affect mRNA expressions encoding lipid metabolism-related protein in liver. In addition, feeding OBFR-diet decreased the abdominal fat tissue weight and improved plasma lipid profiles, while WRB-containing diet did not affect them. These results suggested that feeding OBFR-diet might prevent lipid accumulation via enhancing fecal lipid excretion in rats.
A regulatory motif in nonmuscle myosin II-B regulates its role in migratory front–back polarity
Authors: Juanes-Garcia Alba , Chapman Jessica R. , Aguilar-Cuenca Rocio , Delgado-Arevalo Cristina , Hodges Jennifer , Whitmore Leanna A. , Shabanowitz Jeffrey , Hunt Donald F. , Horwitz Alan Rick , Vicente-Manzanares Miguel
Published: April 2015

In this study, we show that the role of nonmuscle myosin II (NMII)-B in front–back migratory cell polarity is controlled by a short stretch of amino acids containing five serines (1935–1941). This motif resides near the junction between the C terminus helical and nonhelical tail domains. Removal of this motif inhibited NMII-B assembly, whereas its insertion into NMII-A endowed an NMII-B–like ability to generate large actomyosin bundles that determine the rear of the cell. Phosphomimetic mutation of the five serines also inhibited NMII-B assembly, rendering it unable to support front–back polarization. Mass spectrometric analysis showed that several of these serines are phosphorylated in live cells. Single-site mutagenesis showed that serine 1935 is a major regulatory site of NMII-B function. These data reveal a novel regulatory mechanism of NMII in polarized migrating cells by identifying a key molecular determinant that confers NMII isoform functional specificity.
Spatiotemporal control of phosphatidylinositol 4-phosphate by Sac2 regulates endocytic recycling
Authors: Hsu FoSheng , Hu Fenghua , Mao Yuxin
Published: April 2015

It is well established that the spatial- and temporal-restricted generation and turnover of phosphoinositides (PIs) by a cascade of PI-metabolizing enzymes is a key regulatory mechanism in the endocytic pathway. Here, we demonstrate that the Sac1 domain–containing protein Sac2 is a PI 4-phosphatase that specifically hydrolyzes phosphatidylinositol 4-phosphate in vitro. We further show that Sac2 colocalizes with early endosomal markers and is recruited to transferrin (Tfn)-containing vesicles during endocytic recycling. Exogenous expression of the catalytically inactive mutant Sac2C458S resulted in altered cellular distribution of Tfn receptors and delayed Tfn recycling. Furthermore, genomic ablation of Sac2 caused a similar perturbation on Tfn and integrin recycling as well as defects in cell migration. Structural characterization of Sac2 revealed a unique pleckstrin-like homology Sac2 domain conserved in all Sac2 orthologues. Collectively, our findings provide evidence for the tight regulation of PIs by Sac2 in the endocytic recycling pathway.
Recent insights into the cellular biology of atherosclerosis
Authors: Tabas Ira , García-Cardeña Guillermo , Owens Gary K.
Published: April 2015

Atherosclerosis occurs in the subendothelial space (intima) of medium-sized arteries at regions of disturbed blood flow and is triggered by an interplay between endothelial dysfunction and subendothelial lipoprotein retention. Over time, this process stimulates a nonresolving inflammatory response that can cause intimal destruction, arterial thrombosis, and end-organ ischemia. Recent advances highlight important cell biological atherogenic processes, including mechanotransduction and inflammatory processes in endothelial cells, origins and contributions of lesional macrophages, and origins and phenotypic switching of lesional smooth muscle cells. These advances illustrate how in-depth mechanistic knowledge of the cellular pathobiology of atherosclerosis can lead to new ideas for therapy.
PI(4)P gets Sac-rificed in the name of endocytic recycling
Authors: Short Ben
Published: April 2015

Two studies reveal that Sac2 acts as a phosphoinositide 4-phosphatase on early endosomes.
Dyche Mullins: Finding filaments at the fringes
Authors: Powell Kendall
Published: April 2015

Mullins has made his mark by exploring the actin cytoskeleton’s frontiers.
Functional and genomic diversity of methylotrophic Rhodocyclaceae: description of Methyloversatilis discipulorum sp. nov.
Authors: Smalley Nicole E. , Taipale Sami , De Marco Paolo , Doronina Nina V. , Kyrpides Nikos , Shapiro Nicole , Woyke Tanja , Kalyuzhnaya Marina G.
Published: April 2015

Three strains of methylotrophic Rhodocyclaceae (FAM1T, RZ18-153 and RZ94) isolated from Lake Washington sediment samples were characterized. Based on phylogenetic analysis of 16S rRNA gene sequences the strains should be assigned to the genus Methyloversatilis. Similarly to other members of the family, the strains show broad metabolic capabilities and are able to utilize a number of organic acids, alcohols and aromatic compounds in addition to methanol and methylamine. The main fatty acids were 16:1ω7c (49–59 %) and 16:0 (32–29 %). Genomes of all isolates were sequenced, assembled and annotated in collaboration with the DOE Joint Genome Institute (JGI). Genome comparison revealed that the strains FAM1T, RZ18-153 and RZ94 are closely related to each other and almost equally distant from two previously described species of the genus Methyloversatilis, Methyloversatilis universalis and Methyloversatilis thermotolerans. Like other methylotrophic species of the genus Methyloversatilis, all three strains possess one-subunit PQQ-dependent ethanol/methanol dehydrogenase (Mdh-2), the N-methylglutamate pathway and the serine cycle (isocitrate lyase/malate synthase, Icl/ms+ variant). Like M. universalis, strains FAM1T, RZ18-153 and RZ94 have a quinohemoprotein amine dehydrogenase, a tungsten-containing formaldehyde ferredoxin oxidoreductase, phenol hydroxylase, and the complete Calvin cycle. Similarly to M. thermotolerans, the three strains possess two-subunit methanol dehydrogenase (MxaFI), monoamine oxidase (MAO) and nitrogenase. Based on the phenotypic and genomic data, the strains FAM1T, RZ18-153 and RZ94 represent a novel species of the genus Methyloversatilis, for which the name Methyloversatilis discipulorum sp. nov. is proposed. The type strain is FAM1T ( = JCM 30542T = VKM = B-2888T).
Mameliella atlantica sp. nov., a marine bacterium of the Roseobacter clade isolated from deep-sea sediment of the South Atlantic Ocean
Authors: Xu Hongxiu , Jiang Lijing , Li Shaoneng , Zeng Xiang , Shao Zongze
Published: April 2015

A taxonomic study was carried out on strain L6M1-5T, which was isolated from deep-sea sediment collected from the South Atlantic Ocean. The isolate was Gram-reaction-negative, oxidase-negative and catalase-weakly positive. Growth was observed in the presence of 0.5–15 % (w/v) NaCl (optimum 3–5 %), at 10–41 °C (optimum 28–30 °C), and pH 5.0–10.5 (optimum pH 7.0). The principal fatty acids were summed feature8 (C18 : 1ω7c/ω6c) (84.2 %), C18 : 0 (6.3 %), C12 : 1 3-OH (3.2 %) and C16 : 0 (2.7 %). The polar lipid profile comprised phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminolipids, two unknown phospholipids and one unknown lipid. Ubiquinone-10 was the major quinone. The G+C content of the genomic DNA was 66.0 mol %. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain L6M1-5T belonged to the genus Mameliella and shared 95.8 % sequence similarity with Mameliella alba JLT354-WT. The combined genotypic and phenotypic data show that strain L6M1-5T represents a novel species of the genus Mameliella, for which the name Mameliella. atlantica sp. nov. is proposed. The type strain is L6M1-5T ( = MCCC 1A07531T = JCM 30230T).