bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced extrinsic absorption promotes the visible light photocatalytic activity of wide band-gap (BiO)2CO3 hierarchical structure
Authors: Xiong Ting , Dong Fan , Wu Zhongbiao
Published: October 2014

(BiO)2CO3 hierarchical microspheres showed higher visible light photocatalytic activity due to enhanced extrinsic absorption benefiting from light reflecting and scattering.
Strain hardening and highly resilient hydrogels crosslinked by chain-extended reactive pseudo-polyrotaxane
Authors: Cui Yulin , Tan Mei , Zhu Aidi , Guo Mingyu
Published: October 2014

Hydrogels with obvious strain hardening and high resilience properties in both stretching and compressing processes are constructed by simple free-radical copolymerization of acrylamide and reactive pseudo-polyrotaxane.
The pentafluorophenyl group as π-acceptor for anions: a case study
Authors: Giese Michael , Albrecht Markus , Valkonen Arto , Rissanen Kari
Published: October 2014

A unique structural study investigates the variability of anion–π bonding in the solid state structures of pentafluorophenyl arenes. The hapticity concept is used as tool to describe the structural differences of various anion–π complexes.
A distyrylbenzene based highly efficient deep red/near-infrared emitting organic solid
Authors: Kim Mina , Whang Dong Ryeol , Gierschner Johannes , Park Soo Young
Published: October 2014

A highly efficient deep red/near-infrared emitting organic solid based on a β-dicyanostyrylbenzene derivative was reported.
Lumino-magnetic YAG:Ce nanophosphors: novel synthesis routes for efficient luminescence and magnetic properties
Authors: Jayanthi K. , Manorama Sunkara V.
Published: October 2014

Multifunctional lumino-magnetic YAG:Ce nanophosphors for LEDs and spintronics devices.
Enhanced photochromic efficiency of transparent and flexible nanocomposite films based on PEO–PPO–PEO and tungstate hybridization
Authors: Wang C. , Zhou B. P. , Zeng X. P. , Hong Y. Y. , Gao Y. B. , Wen W. J.
Published: October 2014

Enhanced photochromism of hybrid films synthesized by a simple one-pot self-assembly method.
Stability of the Medial Olivocochlear Reflex as Measured by Distortion Product Otoacoustic Emissions
Authors: Mishra Srikanta K. , Abdala Carolina
Published: October 2014

Purpose

The purpose of this study was to assess the repeatability of a fine-resolution, distortion product otoacoustic emission (DPOAE)–based assay of the medial olivocochlear (MOC) reflex in normal-hearing adults.

Method

Data were collected during 36 test sessions from 4 normal-hearing adults to assess short-term stability and 5 normal-hearing adults to assess long-term stability. DPOAE level and phase measurements were recorded with and without contralateral acoustic stimulation. MOC reflex indices were computed by (a) noting contralateral acoustic stimulation-induced changes in DPOAE level (both absolute and normalized) at fine-structure peaks, (b) recording the effect as a vector difference, and (c) separating DPOAE components and considering a component-specific metric.

Results

Analyses indicated good repeatability of all indices of the MOC reflex in most frequency ranges. Short- and long-term repeatability were generally comparable. Indices normalized to a subject's own baseline fared best, showing strong short- and long-term stability across all frequency intervals.

Conclusions

These results suggest that fine-resolution DPOAE-based measures of the MOC reflex measured at strategic frequencies are stable, and natural variance from day-to-day or week-to-week durations is small enough to detect between-group differences and possibly to monitor intervention-related success. However, this is an empirical question that must be directly tested to confirm its utility.
Veridical and False Recall in Adults Who Stutter
Authors: Byrd Courtney T. , Sheng Li , Ratner Nan Bernstein , Gkalitsiou Zoi
Published: October 2014

Purpose

This study used a false memory paradigm to explore the veridical and false recall of adults who stutter.

Method

Twelve adults who stutter and 12 age-matched typically fluent peers listened to and then verbally recalled lists of words that consisted of either semantic or phonological associates or an equal number of semantic and phonological associates (i.e., hybrid condition) of a single, unpresented critical “lure” word. Three parameters of recall performance were measured across these 3 conditions: (a) number of accurately recalled words, (b) order of recall (primacy vs. recency effect), and (c) number of critical lures produced (i.e., false memories).

Results

Significant group differences were noted in recall accuracy specific to list type and also list position as well as relative to critical lure productions.

Conclusions

Results suggest that certain basic memory processes (i.e., recency effect) and the processing of gist semantic information are largely intact in adults who stutter, but recall of verbatim phonological information and subvocal rehearsal may be deficient.
Multi‐blocks scheme for high definition video display based on digital micro‐mirror device
Authors: Liu Yiqing , Sun Li
Published: October 2014

The digital micro‐mirror device (DMD) and its related techniques have been widely used in various projection equipments. The application of a high‐resolution video display scheme based on the DMD is considered. The scheme has been implemented in hardware with a field programmable gate array (FPGA)‐based platform, which organises and selects the visual data, and then feeds them into the micro‐mirror chip for the projection display based on pulse width modulation (PWM). The proposed scheme divides the video frame into a set of blocks, and the arrays of digital mirrors in different blocks work in a sequential way, so that the needed bandwidth for transferring the image data can be reduced significantly without loss of visual quality.
Compact diamond MOSFET model accounting for PAMDLE applicable down 150 nm node
Authors: Gimenez S.P. , Davini E. , Peruzzi V.V. , Renaux C. , Flandre D.
Published: October 2014

The performance improvements for integrated circuit applications of silicon‐on‐insulator (SOI) metal–oxide semiconductor field‐effect transistors (MOSFETs) implemented with diamond layout style (hexagonal gate geometry) are quantified, thanks to the longitudinal corner effect and parallel association of MOSFETs with different channel lengths effect contributions. Futhermore, an accurate analytical drain current model for planar diamond SOI MOSFET for micrometre scale effective channel lengths is proposed and validated. The concept is then extended by 3D simulations for the 150 nm node fully‐depleted SOI n‐channel MOSFETs.
Crosstalk ratio‐based adaptive 2 × 2 MIMO‐OFDM PLC
Authors: Yoo Jeonghwa , Choe Sangho
Published: October 2014

Practical implementations of power line communications (PLCs) with multiple‐input–multiple‐output (MIMO) generally suffer from crosstalk between ports. Presented is a crosstalk ratio (CR)‐based adaptive 2 × 2 MIMO PLC along with simulation results that demonstrate an improvement on conventional 2 × 2 MIMO PLC in terms of bit‐error‐rate.
Simultaneous process self‐calibration method using TDC for 3D DDR4 DRAM
Authors: Oh Reum , Jang J. , Kim J. , Sung Man Young
Published: October 2014

Three‐dimensional (3D) dynamic random‐access memory (DRAM) with TSVs has been proposed due to continuous demands for low‐power and high‐density memory without IO loading limitation. However, the process difference among the stacked dies causes the timing mismatch of internal signals. To remove signal confliction and reduce signal skews among the stacked dies, the simultaneous process self‐calibration scheme is proposed. The stacked dies using the proposed scheme detect the slowest signal among the stacked dies and internal signals are aligned with the slowest signal at the same time. The time for aligned operation is within one read loop and the scheme is turned off after calibration to reduce additional standby current. The 3D double‐data rate 4 (DDR4) DRAM using the proposed scheme is operated over 2133 Mbit/s at 1.2 V.
Noise reduction in chaotic multi‐dimensional time series using dictionary learning
Authors: Sun Jiancheng
Published: October 2014

Chaotic multi‐dimensional time series (MDTS) exist in some fields such as stock markets and life sciences. To effectively extract the desired information from the measured MDTS, it is important to preprocess data to reduce noise. On the basis of dictionary learning, a method to remove noise is proposed, and the proposed approach is shown to be very effective in the case of MDTS. An MDTS is first considered as a whole, namely an image, and then the method is applied on it. Compared with traditional methods, the proposed approach can utilise the information among the different dimensional time series to improve noise reduction. Using the Lorenz data superimposed by the Gaussian noise as an example, the simulation results have validated the mathematical framework and the performance.
High‐frequency performance of AlGaN channel HEMTs with high breakdown voltage
Authors: Nanjo T. , Kurahashi K. , Imai A. , Suzuki Y. , Nakmura M. , Suita M. , Yagyu E.
Published: October 2014

The high‐frequency characteristics of high electron mobility transistors applying AlGaN for a channel layer (AlGaN channel HEMTs) with greater impacts of alloy disorder scattering than those in conventional HEMTs with a GaN channel layer (GaN channel HEMTs) are investigated. The obtained electron saturation velocity was 4.7 × 106 cm/s and the cutoff frequency was 7 GHz in the AlGaN channel HEMTs with a gate length of 1 μm. These results are promising for several gigahertz band operations of AlGaN channel HEMTs.
9 bit superconductive single‐flux‐quantum digital‐to‐analogue converter
Authors: Mizugaki Y. , Takahashi Y. , Shimada H. , Maezawa M.
Published: October 2014

The design and operation of a 9 bit superconductive single‐flux‐quantum (SFQ) digital‐to‐analogue converter (DAC) are presented. The DAC comprises a 9 bit variable SFQ pulse number multiplier and a 100‐fold voltage multiplier. An SFQ pulse‐frequency modulation technique is employed for coding the analogue output voltage. The DAC is fabricated using an Nb Josephson integration technology. Its output voltage waveform, the amplitude of which is up to 2.54 mVpp, is controlled by digital input signals from a room‐temperature data generator.
Rapid electronic prediction of gene expression regulation in bacterial cells
Authors: Alam S. , Lai E.M‐K. , Young J. , Hasan S.M.R.
Published: October 2014

A cytomorphic circuit that can mimic gene expression regulation mechanisms is presented. It is shown that this circuit can efficiently predict the cellular response of the bacterium Escherichia coli in real time. The simulation outputs of the circuit are compared with biological experimental results. The significant similarity between these results shows that the circuit can be used to predict cellular malfunctioning within microseconds.
Fast sparse reconstruction algorithm for multidimensional signals
Authors: Qiu Wei , Zhou Jianxiong , Zhao Hong Zhong , Fu Qiang
Published: October 2014

The problem of reconstruction for a sparse multidimensional signal from a multilinear system with separable dictionaries by a limited amount of measurements is addressed. For this aim, a continuous Gaussian function is used to approximate the l0 norm of a tensor signal, and a steepest ascent algorithm is exploited to optimise the cost function. Compared with the conventional reconstruction techniques, which usually convert the multidimensional signal into a one‐dimensional (1D) vector, the proposed method can deal with the multidimensional signal directly, and thus it works fast and saves memory usage. Finally, experimental results of hyperspectral imaging demonstrate that the proposed algorithm can well reconstruct the hyperspectral images with a low computational cost.
Strain variation measurement with short‐time Fourier transform‐based Brillouin optical time‐domain reflectometry sensing system
Authors: Tu Guojie , Zhang Xuping , Zhang Yixin , Ying Zhoufeng , Lv Lidong
Published: October 2014

A novel technique to perform dynamic strain measurement with a Brillouin optical time‐domain reflectometry (BOTDR) sensing system based on short‐time Fourier transform (STFT) is proposed. Unlike traditional frequency scanning methods, the proposed system samples the Brillouin backscattering signal directly after it has been downconverted to the intermediated frequency (IF) region. The Brillouin frequency shift (BFS) of the sensing fibre was reconstructed from the recorded time‐domain data continuously without dead‐time, which provided a much higher refreshing rate of the strain measurement. Therefore, dynamic strain variation over an optical fibre can be measured with a single‐end structure that is more flexible and reliable. A 16.7 Hz strain variation on a 12 m section was successfully detected at the end of a 270 m sensing fibre with 4 m spatial resolution and 45 με uncertainty.
Energy‐efficient, reliable wireless body area networks: cooperative diversity switched combining with transmit power control
Authors: Liang Tian , Smith David B.
Published: October 2014

Cooperative diversity using switched combining, incorporating transmit power control (PC), is investigated for wireless body area networks (BANs). Outage probability and switching rate are derived from extensive empirical measurements, along with savings in circuit power consumption using simple ‘sample‐and‐hold’ PC in conjunction with switch‐and‐examine combining (SwC). Theoretical approximation of the switching rate gives a reasonable match with the empirical analysis. It is shown that transmit PC with SwC is an attractive method for increasing network lifetime, through reduced power usage, and for improving radio communications reliability in BANs.
Non‐dispersive tunable reflection phase shifter based on non‐Foster circuits
Authors: Gao Fei , Zhang Fushun , Long Jiang , Jacob Minu , Sievenpiper Daniel
Published: October 2014

A new non‐dispersive tunable reflection phase shifter is introduced based on the artificial magnetic conductor (AMC) loaded with non‐Foster circuits (NFCs). An AMC structure circuit model is extracted and the possibility of mitigating its intrinsic strong dispersion is discussed by loading it with both negative capacitance and negative inductance. The NFC is designed to produce the negative capacitance and inductance based on highly accurate, scalable measurement‐based models, and co‐simulated with a realistic model of the AMC. The numerical results are in good agreement with the analysis and show a nearly flat reflection phase from 450 to 600 MHz. This flat reflection phase can further be tuned by tuning the loaded inductance from 30 to 50 nH. This investigation paves the way towards a dispersion‐less reflection phase shifter design.
Ka‐band circularly polarised omnidirectional antenna for wide elevation coverage
Authors: Verma P.K. , Kumar R. , Singh M.
Published: October 2014

The design, development and characterisation of an inclined waveguide slot‐based circularly polarised (CP) omnidirectional antenna at Ka‐band frequency are described. The antenna consists of inclined slots on a circular waveguide and a coaxial feeding probe. All the radiating slots are fed by the TM01 mode of the circular waveguide to generate the omnidirectional pattern. Inclination of slots has been used to generate circular polarisation. The designed antenna has omni coverage in the azimuthal plane and −10° to +45° coverage in the elevation plane. The antenna has been simulated on finite element method‐based ANSYS high‐frequency structure simulator (HFSS) EM simulator software using proper boundary conditions. The proposed antenna has the advantages of being robust, having wide coverage, being easy to fabricate (being in waveguide configuration) and is suitable for mass production. The measured axial ratio lies well below 2.8 over the horizontal plane. A voltage standing wave ratio of 2.0:1 has been achieved over the frequency band of 37.9–38.55 GHz and the minimum omni gain of the antenna is 0 dBi over the frequency band as well as over the coverage.
Statistical model of the angular power distribution for wireless multipath environments
Authors: Ziółkowski Cezary
Published: October 2014

The study presents a two‐dimensional model of angular power distribution for land mobile environments that can extend the capabilities of modelling the spatial properties of received signals in simulation studies. The developed model gives statistical description of the power azimuth spectrum (PAS) as the closed‐form function. In the literature, the authors can find large collection of small‐scale propagation models that characterise the spatial properties of the received signals. However, their practical use in simulation studies is associated with a significant problem that concerns the matching model parameters for transmission properties of the modelled environment. For the presented PAS model, the power delay profile or the power delay spectrum are the source of input data. Therefore unlike the existing models, the developed PAS model is highly dependent on the transmission characteristics of the modelled environment. For sample scenarios, PAS dependencies on the type of environment, the distance between the transmitter and the receiver, and the uplink and downlink transmissions are shown. Results predicted by this model are compared with those for other models as well with experimental results available for typical and bad urban environments. Comparison shows that the developed PAS model produces results that very closely agree with experimental data.
Design of band‐notched ultra wideband antenna for indoor and wearable wireless communications
Authors: Ur‐Rehman Masood , Abbasi Qammer Hussain , Akram Muhammad , Parini Clive
Published: October 2014

Design of a tapered‐slot ultra wideband (UWB) band‐notched wearable antenna is presented in this study. The antenna operation covers the whole UWB frequency spectrum of 7.5 GHz ranging from 3.1 to 10.6 GHz, while rejecting the wireless local area network operation at 5.25 GHz band. The performance of the antenna is analysed through simulations and validated through measurements. The antenna makes use of ultra‐thin liquid crystal polymer (LCP) substrate. The presented return loss and radiation pattern results show that the antenna offers excellent performance in the UWB frequency band in free space. Use of the LCP substrate makes the antenna to efficiently mitigate the bending effects. Moreover, the antenna performs well in on‐body configurations and its working is little affected in adversely hot and humid weather conditions. Furthermore, it offers good on‐body communication link and pulse fidelity. These features make the proposed antenna design a well‐suited choice for hand‐held and wearable UWB applications.
High step‐up interleaved converter with soft‐switching using a single auxiliary switch for a fuel cell system
Authors: Chao Kuei‐Hsiang , Yang Min‐Sen
Published: October 2014

This study aims to develop a soft‐switching interleaved converter with a high‐voltage conversion ratio using a single auxiliary switch. As a step‐up voltage converter, it performs zero voltage switching and zero current switching operations on main switches by means of the manipulation of the single auxiliary switch. In this manner, both the switching loss and switching stress of main switches can be reduced, giving rise to an improvement in the conversion efficiency. Placed in parallel with a converter available, merely a single resonant branch is employed in the proposed soft‐switching mechanism, a simple and elegant way to reach the goal. This proposal is further applied to a fuel cell system as a high performance DC voltage booster so as to drive a high‐voltage DC load. PSIM simulations are conducted and subsequent experimental validation is presented at the end of this work.
Magnetically coupled high‐gain Y‐source isolated DC/DC converter
Authors: Siwakoti Yam P. , Loh Poh Chiang , Blaabjerg Frede , Town Graham E.
Published: October 2014

A new form of magnetically coupled DC/DC converter is proposed for medium power applications (250 W to 2 kW), requiring a high‐voltage gain, short inductive charging time and galvanic isolation. The proposed converter can be realised using a unique Y‐source impedance network and a two‐switch push–pull circuit with voltage‐doubling rectification. The converter's voltage gain is presently not matched by any other converter operating at the same switch duty ratio. The converter also has more degrees of freedom in design for setting the desired gain than other converters, and hence can better meet the demands of many applications. The operating principles of the converter have been analysed mathematically, and are verified by both simulation and experiment.
Evaluation of current stresses in nine‐switch energy conversion systems
Authors: Qin Zian , Loh Poh Chiang , Bahman Amir Sajjad , Blaabjerg Frede
Published: October 2014

Converters with reduced‐switch counts usually face some performance tradeoffs, which make them suitable for some applications but not others. The same applies to the nine‐switch converter, which is a reduced‐switch version of the back‐to‐back twelve‐switch converter. The nine‐switch converter has since been shown to experience a higher voltage stress, which can be lowered in some cases. A corresponding evaluation of its current stress is however lacking, and is hence addressed now by computing its switch currents when used for ac–ac, ac–dc, dc–ac and dc–dc energy conversions. Relevant expressions, application requirements and simulation results are presented for identifying cases, where the nine‐switch converter can have an improvement in performance despite its reduced‐switch count. These cases are verified in experiments using a 1.5 kW prototype built in the laboratory.
New harmonic mitigation scheme for modular multilevel converter – an experimental approach
Authors: Sreedhar Madichetty , Dasgupta Abhijit , Mishra Sambeet
Published: October 2014

The multilevel converter has been brought into limelight in this study; however, particular attention has been provided to the form and function of modular multilevel converter (MMC) with new controller to mitigate the circulating currents and harmonics present in the system. Till date, research in this field is very limited with circulating currents and harmonics as the major problem. The stability analysis of proposed controller has been derived and analysed with its experimental results. The system is examined before and after application of controller and results is analysed. This article effectively addresses the problem with prototype of 1 KVA implementation and attempts to make a detailed analysis with their functions in comprehensive manner with HVDC application under different conditions. Also, the applicability of zero voltage switching at turn on, zero current transition at turn off has been verified experimentally. Computer simulations and experiment on a 50 Hz power supply show that the new controller is effective and easy to implement for modular multilevel inverters.
Neutron emission measurement at the HL-2A tokamak device with a liquid scintillation detector
Authors: Xie Xufei , Chen Zhongjing , Peng Xingyu , Yuan Xi , Zhang Xing , Gorini Giuseppe , Cui Zhiqiang , Du Tengfei , Hu Zhimeng , Li Tao , Fan Tieshuan , Chen Jinxiang , Li Xiangqing , Zhang Guohui , Yuan Guoliang , Yang Jinwei , Yang Qingwei
Published: October 2014

Neutron emission measurement at the HL-2A tokamak device with a liquid scintillation detector is described. The detector was placed at a location with little structure material in the field of view, and equipped with a gain monitoring system which could provide the possibility to evaluate the gain variation as well as to correct for the detector response. Time trace of the neutron emissivity was obtained and it was consistent with the result of a standard 235U fission chamber. During the plasma discharge the neutron yield could vary by about four orders of magnitude and the fluctuation of the detector gain was up to about 6%. Pulse height spectrum of the liquid scintillation detector was constructed and corrected with the aid of the gain monitoring system, and the correction was found to be essential for the assessment of the neutron energy spectrum. This successful measurement offered experience and confidence for the application of liquid scintillation detectors in the upcoming neutron camera system.
Sensitivity of aerodynamic forces in laminar and turbulent flow past a square cylinder
Authors: Meliga Philippe , Boujo Edouard , Pujals Gregory , Gallaire François
Published: October 2014

We use adjoint-based gradients to analyze the sensitivity of the drag force on a square cylinder. At Re = 40, the flow settles down to a steady state. The quantity of interest in the adjoint formulation is the steady asymptotic value of drag reached after the initial transient, whose sensitivity is computed solving a steady adjoint problem from knowledge of the stable base solution. At Re = 100, the flow develops to the time-periodic, vortex-shedding state. The quantity of interest is rather the time-averaged mean drag, whose sensitivity is computed integrating backwards in time an unsteady adjoint problem from knowledge of the entire history of the vortex-shedding solution. Such theoretical frameworks allow us to identify the sensitive regions without computing the actually controlled states, and provide a relevant and systematic guideline on where in the flow to insert a secondary control cylinder in the attempt to reduce drag, as established from comparisons with dedicated numerical simulations of the two-cylinder system. For the unsteady case at Re = 100, we also compute an approximation to the mean drag sensitivity solving a steady adjoint problem from knowledge of only the mean flow solution, and show the approach to carry valuable information in view of guiding relevant control strategy, besides reducing tremendously the related numerical effort. An extension of this simplified framework to turbulent flow regime is examined revisiting the widely benchmarked flow at Reynolds number Re = 22 000, the theoretical predictions obtained in the frame of unsteady Reynolds-averaged Navier–Stokes modeling being consistent with experimental data from the literature. Application of the various sensitivity frameworks to alternative control objectives such as increasing the lift and reducing the fluctuating drag and lift is also discussed and illustrated with a few selected examples.
Study of the electronic and rovibronic structure of the X 2Σ+, A 2Π, and B 2Σ+ states of AlO
Authors: Patrascu Andrei T. , Hill Christian , Tennyson Jonathan , Yurchenko Sergei N.
Published: October 2014

The electronic structure of the X 2Σ+, A 2Π, and B 2Σ+ states of aluminum monoxide (AlO) are studied via ab initiomulti-reference configuration interaction calculations. Core correlation corrections, several basis sets, and active space choices are considered. Angular momentum and spin-orbit coupling terms are obtained at different levels of theory. The resulting ab initio curves are used to solve the associated rovibronic problem for the total angular momentum J up to 112.5 and then also refined by fitting to the experimental wavenumbers available in the literature, reproducing them with the root-mean-square error of 0.07 cm−1. Theoretical rovibronic energy levels of AlO in its X 2Σ+, A 2Π, and B 2Σ+ electronic states are presented including those from the X − B blue-green system.
Studies of singlet Rydberg series of LiH derived from Li(nl) + H(1s), with n ≤ 6 and l ≤ 4
Authors: Gim Yeongrok , Lee Chun-Woo
Published: October 2014

The 50 singlet states of LiH composed of 49 Rydberg states and one non-Rydberg ionic state derivable from Li(nl) + H(1s), with n ≤ 6 and l ≤ 4, are studied using the multi-reference configuration interaction method combined with the Stuttgart/Köln group's effective core potential/core polarization potential method. Basis functions that can yield energy levels up to the 6g orbital of Li have been developed, and they are used with a huge number of universal Kaufmann basis functions for Rydberg states. The systematics and regularities of the physical properties such as potential energies, quantum defects, permanent dipole moments, transition dipole moments, and nonadiabatic coupling matrix elements of the Rydberg series are studied. The behaviors of potential energy curves and quantum defect curves are explained using the Fermi approximation. The permanent dipole moments of the Rydberg series reveal that they are determined by the sizes of the Rydberg orbitals, which are proportional to n2. Interesting mirror relationships of the dipole moments are observed between l-mixed Rydberg series, with the rule Δl = ±1, except for s–d mixing, which is also accompanied by n-mixing. The members of the l-mixed Rydberg series have dipole moments with opposite directions. The first derivatives of the dipole moment curves, which show the charge-transfer component, clearly show not only mirror relationships in terms of direction but also oscillations. The transition dipole moment matrix elements of the Rydberg series are determined by the small-r region, with two consequences. One is that the transition dipole moment matrix elements show n−3/2 dependence. The other is that the magnitudes of the transition dipole moment matrix elements decrease rapidly as l increases.
Statistics of dislocation pinning at localized obstacles
Authors: Dutta A. , Bhattacharya M. , Barat P.
Published: October 2014

Pinning of dislocations at nanosized obstacles like precipitates, voids, and bubbles is a crucial mechanism in the context of phenomena like hardening and creep. The interaction between such an obstacle and a dislocation is often studied at fundamental level by means of analytical tools, atomistic simulations, and finite element methods. Nevertheless, the information extracted from such studies cannot be utilized to its maximum extent on account of insufficient information about the underlying statistics of this process comprising a large number of dislocations and obstacles in a system. Here, we propose a new statistical approach, where the statistics of pinning of dislocations by idealized spherical obstacles is explored by taking into account the generalized size-distribution of the obstacles along with the dislocation density within a three-dimensional framework. Starting with a minimal set of material parameters, the framework employs the method of geometrical statistics with a few simple assumptions compatible with the real physical scenario. The application of this approach, in combination with the knowledge of fundamental dislocation-obstacle interactions, has successfully been demonstrated for dislocation pinning at nanovoids in neutron irradiated type 316-stainless steel in regard to the non-conservative motion of dislocations. An interesting phenomenon of transition from rare pinning to multiple pinning regimes with increasing irradiation temperature is revealed.
On the existence of vapor-liquid phase transition in dusty plasmas
Authors: Kundu M. , Avinash K. , Sen A. , Ganesh R.
Published: October 2014

The phenomenon of phase transition in a dusty-plasma system (DPS) has attracted some attention in the past. Earlier Farouki and Hamaguchi [J. Chem. Phys. 101, 9876 (1994)] have demonstrated the existence of a liquid to solid transition in DPS where the dust particles interact through a Yukawa potential. However, the question of the existence of a vapor-liquid (VL) transition in such a system remains unanswered and relatively unexplored so far. We have investigated this problem by performing extensive molecular dynamics simulations which show that the VL transition does not have a critical curve in the pressure versus volume diagram for a large range of the Yukawa screening parameter κ and the Coulomb coupling parameter Γ. Thus, the VL phase transition is found to be super-critical, meaning that this transition is continuous in the dusty plasma model given by Farouki and Hamaguchi. We provide an approximate analytic explanation of this finding by means of a simple model calculation.
Conducting polymer functionalized single-walled carbon nanotube based chemiresistive biosensor for the detection of human cardiac myoglobin
Authors: Puri Nidhi , Niazi Asad , Biradar Ashok M. , Mulchandani Ashok , Rajesh
Published: October 2014

We report the fabrication of a single-walled carbon nanotube (SWNT) based ultrasensitive label-free chemiresistive biosensor for the detection of human cardiac biomarker, myoglobin (Ag-cMb). Poly(pyrrole-co-pyrrolepropylic acid) with pendant carboxyl groups was electrochemically deposited on electrophoretically aligned SWNT channel, as a conducting linker, for biomolecular immobilization of highly specific cardiac myoglobin antibody. The device was characterized by scanning electron microscopy, source-drain current-voltage (I-V), and charge-transfer characteristic studies. The device exhibited a linear response with a change in conductance in SWNT channel towards the target, Ag-cMb, over the concentration range of 1.0 to 1000 ng ml−1 with a sensitivity of ∼118% per decade with high specificity.
Dielectric and shear relaxations of ionic liquid composed of symmetric ions
Authors: Yamaguchi Tsuyoshi , Koda Shinobu
Published: October 2014

The frequency-dependent conductivity and shear viscosity of an ionic liquid composed of symmetric ions were determined experimentally in the MHz region. The ionic liquid studied was tetraoctylphosphonium bromide. An isomer with an asymmetric cation, trihexyltetradecylphosphonium bromide, was also investigated to clarify the possible role of the reorientational motion of the cations in the two relaxation spectra. Both the conductivity and the shear viscosity show relaxation in the MHz region, and these relaxation spectra scarcely depend on the asymmetry of the cations. It is, therefore, concluded that the coupling of the reorientational mode of cations with these relaxation spectra is marginal, and that these spectra reflect mainly the frequency-dependent translational motion of ions.
Generation and characterization of plasma channels in gas puff targets using soft X-ray radiography technique
Authors: Wachulak P. W. , Bartnik A. , Jarocki R. , Fok T. , Węgrzyński Ł. , Kostecki J. , Szczurek M. , Jabczyński J. , Fiedorowicz H.
Published: October 2014

We present our recent results of a formation and characterization of plasma channels in elongated krypton and xenon gas puff targets. The study of their formation and temporal expansion was carried out using a combination of a soft X-ray radiography (shadowgraphy) and pinhole camera imaging. Two high-energy short laser pulses were used to produce the channels. When a pumping laser pulse was shaped into a line focus, using cylindrical and spherical lenses, the channels were not produced because much smaller energy density was deposited in the gas puff target. However, when a point focus was obtained, using just a spherical lens, the plasma channels appeared. The channels were up to 9 mm in length, had a quite uniform density profile, and expanded in time with velocities of about 2 cm/μs.
Enhanced hardness in epitaxial TiAlScN alloy thin films and rocksalt TiN/(Al,Sc)N superlattices
Authors: Saha Bivas , Lawrence Samantha K. , Schroeder Jeremy L. , Birch Jens , Bahr David F. , Sands Timothy D.
Published: October 2014

High hardness TiAlN alloys for wear-resistant coatings exhibit limited lifetimes at elevated temperatures due to a cubic-AlN to hexagonal-AlN phase transformation that leads to decreasing hardness. We enhance the hardness (up to 46 GPa) and maximum operating temperature (up to 1050 °C) of TiAlN-based coatings by alloying with scandium nitride to form both an epitaxial TiAlScN alloy film and epitaxial rocksalt TiN/(Al,Sc)N superlattices on MgO substrates. The superlattice hardness increases with decreasing period thickness, which is understood by the Orowan bowing mechanism of the confined layer slip model. These results make them worthy of additional research for industrial coating applications.
Structural and emission properties of InGaAs/GaAs quantum dots emitting at 1.3 μm
Authors: Goldmann Elias , Paul Matthias , Krause Florian F. , Müller Knut , Kettler Jan , Mehrtens Thorsten , Rosenauer Andreas , Jetter Michael , Michler Peter , Jahnke Frank
Published: October 2014

A combined experimental and theoretical study of InGaAs/GaAs quantum dots (QDs) emitting at 1.3 μm under the influence of a strain-reducing InGaAs quantum well is presented. We demonstrate a red shift of 20–40 nm observed in photoluminescence spectra due to the quantum well. The InGaAs/GaAs QDs grown by metal organic vapor phase epitaxy show a bimodal height distribution (1 nm and 5 nm) and indium concentrations up to 90%. The emission properties are explained with combined tight-binding and configuration-interaction calculations of the emission wavelengths in conjunction with high-resolution scanning transmission electron microscopy investigations of QD geometry and indium concentrations in the QDs, which directly enter the calculations. QD geometries and concentration gradients representative for the ensemble are identified.
Multi-direction high-efficiency second harmonic generation in ellipse structure nonlinear photonic crystals
Authors: Chen Bao-Qin , Zhang Chao , Liu Rong-Juan , Li Zhi-Yuan
Published: October 2014

We have designed and fabricated a lithium niobate (LN) nonlinear photonic crystal (NPC) with a two-dimensional (2D) ellipse structure of inverse poling domains. The structure can offer continuously varying reciprocal lattice vectors in different directions to compensate the phase-mismatching during the second harmonic generation (SHG) for diverse pump wavelengths. We consider three propagation directions with large effective nonlinear susceptibility and measure the nonlinear conversion efficiency of SHG. The experimental data are in good agreement with the quantitative calculation results using the effective susceptibility model with pump depletion. With high-efficiency SHG in multiple propagation direction, the 2D ellipse structure of LN NPC has the potential to realize various broadband nonlinear frequency conversion processes in different propagation direction with a single crystal.
Charge carrier transport properties in layer structured hexagonal boron nitride
Authors: Doan T. C. , Li J. , Lin J. Y. , Jiang H. X.
Published: October 2014

Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0)−α with α = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.
Investigation of chemical composition and crystal structure in sintered Ce15Nd15FebalB1 magnet
Authors: Huang Shu-lin , Feng Hai-bo , Zhu Ming-gang , Li An-hua , Zhang Yue , Li Wei
Published: October 2014

The substitution of cerium, a more abundant rare-earth element, for sintered Nd-Fe-B magnets has drawn intense interest. In the present work, nominal composition of Ce15Nd15FebalB1 (wt. %), with cerium constitutes increased to 50% of the total rare-earth content, was used. And Ce-free Nd30FebalB1 (wt. %) was prepared by the same preparation process as comparison. The microstructure of the sintered magnets has been investigated by means of X-ray diffraction and transmission electron microscope. The results show that there are three kinds of RE-rich phases in the same magnet, i.e., fcc-(Ce,Nd)Ox (a=0.547nm), hcp-(Ce,Nd)2O3 (a=0.386nm, c=0.604nm) and bcc-(Ce,Nd)2O3 (a=1.113nm). Ors of (140)(Ce,Nd)2Fe14B// (1-21)bcc-(Ce,Nd)2O3(∼3°), [001](Ce,Nd)2Fe14B// [-214]bcc-(Ce,Nd)2O3; (01-1)(Ce,Nd)2Fe14B// (101)fcc- (Ce,Nd)Ox(∼2°), [101](Ce,Nd)2Fe14B// [12-1]fcc-(Ce,Nd)Ox were found through selected area electron diffraction (SAED) analysis. According to the analysis, it can be concluded that cerium has partly substituted for neodymium by occupying the corresponding atom sites in the Ce15Nd15FebalB1 magnet, without changing the crystal configuration.
Demographic history and niche conservatism of tropical rainforest trees separated along an altitudinal gradient of a biogeographic barrier
Authors: Mellick Rohan , Wilson Peter D. , Rossetto Maurizio
Published: October 2014

The genetic disjunctions and distributions of long-lived species provide valuable signatures of past demographic response to environmental change. Here we use genetic markers to study two Elaeocarpus species from the Australian Wet Tropics to understand changes in palaeodistribution and demography associated with environmental change on either side of the Black Mountain Corridor (BMC). Contrasting the genetic structure of species with different distributions along altitudinal gradients is important to explore some of the environmental drivers of adaptive evolution. Using coalescent-based molecular and environmental niche models, we investigate the demographic history of two long-lived, altitudinally differentiated species that were previously identified as genetically divergent across the BMC. The origin of the genetic disjunction across the BMC is inferred to have occurred during the last glacial cycle in relation to 13 combined molecular histories of both plastid and nuclear loci. Interestingly, whereas midland populations show a dynamic history of expansion and contraction, the highland populations do not. Molecular history and environmental niche models show the populations north of the BMC have remained relatively stable over time in response to environmental change. Populations south of the BMC have been more dynamic in response to environmental change. These differences are likely to highlight the topographical character and environmental heterogeneity of areas separated by the BMC.
DNA supercoiling: A regulatory signal for the λ repressor
Authors: Ding Yue , Manzo Carlo , Fulcrand Geraldine , Leng Fenfei , Dunlap David , Finzi Laura
Published: October 2014

Significance

Low levels of λ repressor (CI) can autoenhance expression and lysogeny (quiescence) of bacteriophage λ infection. However, additional CI mediates an autorepressive DNA loop. Supercoiling catalyzes looping in unstretched plasmids, but whether supercoiling catalyzes looping under tension, and whether the
cI
promoter within the loop becomes superhelically isolated were investigated. CI efficiently partitioned plasmids into topological domains and formed barriers to the passage of supercoiling from one into another. Furthermore, in single DNA molecules twisted with magnetic tweezers, CI-mediated DNA loops confined as much as −15% to +11% supercoiling. Finally, under gentle tensions likely to occur in vivo, supercoiling was essential for looping. CI may exploit supercoil-driven looping events to regulate the lysogenic/lytic switch.
Highly cooperative stress relaxation in two-dimensional soft colloidal crystals
Authors: van der Meer Berend , Qi Weikai , Fokkink Remco G. , van der Gucht Jasper , Dijkstra Marjolein , Sprakel Joris
Published: October 2014

Significance

The creation, annihilation, and diffusion of defects in crystal lattices play an important role during crystal melting and deformation. Although it is well understood how defects form and react when crystals are subjected to external stresses, it remains unclear how crystals cope with internal stresses. We report a study in which we create a highly localized internal stress in a crystal formed from micrometer-sized colloidal spheres and directly observe how the solid reacts using microscopy. We find that, even though the excitation is highly localized, a collective dance of colloidal particles results, even when the excitations are thermally driven. These data shed light on the importance of highly collective motions on the stability and instability of crystalline solids.
Investigating the optimal size of anticancer nanomedicine
Authors: Tang Li , Yang Xujuan , Yin Qian , Cai Kaimin , Wang Hua , Chaudhury Isthier , Yao Catherine , Zhou Qin , Kwon Mincheol , Hartman James A. , Dobrucki Iwona T. , Dobrucki Lawrence W. , Borst Luke B. , Lezmi Stéphane , Helferich William G. , Ferguson Andrew L. , Fan Timothy M. , Cheng Jianjun
Published: October 2014

Significance

Understanding the interdependency of physiochemical properties of nanomedicine (NM) in correlation to its biological response and function is crucial for additional development of anticancer NM. Here, we prepared monodisperse drug–silica nanoconjugates in three distinct sizes (20, 50, and 200 nm) with other physiochemical properties controlled to be identical to investigate size-dependent biodistribution, tumor tissue penetration and clearance, and anticancer efficacy in various tumor models. We also developed a mathematical model of the spatiotemporal distribution of NM within a tumor to gain insight into the size-dependent interaction with tumor. Our studies show clear evidence that there is an optimal size of anticancer NM and that NM with the optimal size has the highest tumor retention integrated over time.
Traditional and Fermented Soybean Meals as Ingredients in Feeds for White Seabass and Yellowtail Jack
Authors: Trushenski Jesse T , Rombenso Artur N , Page Michael , Jirsa David , Drawbridge Mark
Published: October 2014

Soybean meal is commonly used as a protein source in aquafeeds, but its benefits can be limited by its digestibility and the presence of antinutritional factors. Fermentation may address both of these issues, thereby improving utilization of soybean meal by carnivorous fish. We compared the production performance of juvenile White Seabass Atractoscion nobilis and Yellowtail Jack Seriola lalandi that were fed diets containing fish meal, or graded levels of traditional soybean meal or fermented soybean meal. These diets were also compared to reduced or fish-meal-free feeds based on soy protein concentrate, poultry byproduct meal, or algal meal (spirulina Spirulina spp.). Complete fish meal replacement yielded poor performance in both species, regardless of the alternative protein source used. White Seabass performed well on diets containing blends of fish meal and traditional or fermented soybean meals or soy protein concentrate; similar results were observed in Yellowtail Jack, though performance was slightly reduced among fish fed the feed containing fermented soybean meal. These results conflict somewhat with investigations of fermented soybean meal in other fish taxa, as well as previous investigations of poultry byproduct meal and spirulina algal meal in White Seabass and Yellowtail Jack. Each of these feedstuffs has potential as a protein source in aquafeeds but presents limitations which must be addressed.