bluuebunny/crossref_metadata_2025 huggingface dataset:
Approaching real‐time terahertz imaging with photo‐induced coded apertures and compressed sensing
Authors: Shams M.I.B. , Jiang Z. , Rahman S. , Qayyum J. , Cheng L.‐J. , Xing H. G. , Fay P. , Liu L.
Published: May 2014

Photo‐induced coded‐aperture imaging (PI‐CAI) based on compressed sensing (CS) at 590 GHz using a WR‐1.5 (500–750 GHz) vector network analyser is demonstrated. For a 256‐pixel (16 × 16) frame, the acquisition time can be reduced by 40%, as compared with PI‐CAI without CS, while maintaining high imaging quality. On the basis of this approach, it is envisioned that real‐time (26 fps) THz imaging with 1000 pixels (32 × 32) can be realised using high‐speed digital micromirror device chipsets and optimised data‐acquisition software.
Contactless radio frequency probes for high‐temperature characterisation of microwave integrated circuits
Authors: Jordan J.L. , Simons R.N. , Zorman C.A.
Published: May 2014

The first ever demonstration of a viable contactless radio frequency (RF) probing technique at elevated temperatures is presented. The design utilises an inverted microstrip design for the probe, which is suspended over and placed in close proximity to the input/output microstrip lines of the device under test to couple signals in and out. To demonstrate the efficacy of the contactless RF probing technique, three example circuits, namely, a microstrip spurline bandstop filter, a microstrip pin diode series switch and a monolithic microwave integrated circuit amplifier mounted on a microstrip line were designed, fabricated and performance measured against temperature up to 200°C.
Adaptive weighted real‐time compressive tracking
Authors: Zhu Jianzhang , Ma Yue , Qin Qianqing , Zheng Chen , Hu Yijun
Published: May 2014

Many tracking methods often suffer from the drift problems caused by appearance change. Therefore developing a robust online tracker is still a challenging test. Recently, a simple yet effective and efficient tracking algorithm has been proposed by compressive tracking (CT) paradigm to alleviate the drift to some degree. The CT tracker introduced an appearance model based on features extracted from the multi‐scale image feature space in the compressed domain. However, the CT tracker may detect the positive sample that is less important because it does not discriminatively consider the sample importance in its learning procedure. In this study, the authors integrate the sample importance into the CT tracker online learning procedure. They also add an efficient feature select method which can choose the most discriminative power weak classifier and employ the co‐training criterion into CT tracker to improve the tracking performance. Experiments show that the proposed tracker demonstrates the superior performance in robustness and efficiency than other state‐of‐the‐art trackers.
Comprehensive optimal photovoltaic inverter control strategy in unbalanced three‐phase four‐wire low voltage distribution networks
Authors: Su Xiangjing , Masoum Mohammad A.S. , Wolfs Peter
Published: May 2014

The continuous expansion of consumer‐driven installations of residential rooftop photovoltaic (PV) systems causes serious power quality, notable voltage variations and unbalance, which limit the number and capacity of the further connections. The latent reactive power capability of PV inverters can increase the network PV hosting capability. This study proposes both reactive power control and real power curtailment as a comprehensive inverter control strategy to improve the operating performance of unbalanced three‐phase four‐wire low voltage distribution networks with high penetrations of residential PV systems. A multi‐objective optimal power flow (OPF) problem that can simultaneously improve voltage magnitude and balance profiles while minimising network loss and generation costs is defined. The solution is found using the global solver based on Sequential Quadratic Programming algorithm with multiple starting points in Matlab. Detailed simulations are performed and analysed for typical operating scenarios over 24‐h period on a real three‐phase four‐wire unbalanced distribution network in Perth Solar City trial, Australia. Smart meter readings are used to justify the accuracy and validation of the network model and the proposed multi‐objective OPF model.
Variations in Emergence and Course of the Inferior Palpebral Nerve
Authors: Nderitu Joseph , Butt Fawzia , Saidi Hassan
Published: May 2014

Comprehensive understanding of the anatomy of the inferior palpebral (IP) nerve is crucial to preservation of sensation in the inferior eyelid and conjunctiva. Iatrogenic injuries may occur during blepharoplasty, repair of orbitozygomatic fracture and other maxillofacial surgeries involving this region. Although several studies depict the anatomical variations of the main infraorbital nerve (ION), little information exclusive to the IP nerve exists. This study provides information on the additional variations of the ION with reference to the IP nerve. The study was performed on 84 IP nerves by dissection of 42 formalin-fixed cadavers from the laboratory of topographic anatomy, Department of Human Anatomy, University of Nairobi, Kenya. Each of the nerves were exposed at the emergence and followed to their termination. Variations encountered involved emergence, course, and even absence. Variant emergence was through an accessory infraorbital foramen, an infraorbital notch, and as a common trunk with the external nasal nerve. This nerve shows high anatomical variability that may account for the difficulties and complications encountered in clinical interventions. It is believed that this information will improve clinical management of conditions affecting the region of distribution of the IP nerve.
Transconjunctival Inferior Orbitotomy: Indications, Surgical Technique, and Complications
Authors: Davies Brett W. , Hink Eric M. , Durairaj Vikram D.
Published: May 2014

Surgical access to the inferior orbit can be accomplished through either a transcutaneous or transconjunctival incision. The preferred approach should provide adequate surgical exposure with the fewest adverse effects. The purpose of this article is to review the literature on the transconjunctival incision and to discuss the indications and complications of the approach. The authors also discuss their preferred technique and provide a step-by-step instruction. The transconjunctival approach provides good surgical access with a low incidence of complications and a better aesthetic outcome than transcutaneous approaches.
A Review of the Diagnosis and Treatment of Atlantoaxial Dislocations
Authors: Yang Sun Y. , Boniello Anthony J. , Poorman Caroline E. , Chang Andy L. , Wang Shenglin , Passias Peter G.
Published: May 2014

Study Design

Literature review.

Objective

Atlantoaxial dislocation (AAD) is a rare and potentially fatal disturbance to the normal occipital-cervical anatomy that affects some populations disproportionately, which may cause permanent neurologic deficits or sagittal deformity if not treated in a timely and appropriate manner. Currently, there is a lack of consensus among surgeons on the best approach to diagnose, characterize, and treat this condition. The objective of this review is to provide a comprehensive review of the literature to identify timely and effective diagnostic techniques and treatment modalities of AAD.

Methods

This review examined all articles published concerning “atlantoaxial dislocation” or “atlantoaxial subluxation” on the PubMed database. We included 112 articles published between 1966 and 2014.

Results

Results of these studies are summarized primarily as defining AAD, the normal anatomy, etiology of dislocation, clinical presentation, diagnostic techniques, classification, and recommendations for timely treatment modalities.

Conclusions

The Wang Classification System provides a practical means to diagnose and treat AAD. However, future research is required to identify the most salient intervention component or combination of components that lead to the best outcomes.
Sampling the equilibrium kinetic network of Trp-cage in explicit solvent
Authors: Du Weina , Bolhuis Peter G.
Published: May 2014

We employed the single replica multiple state transition interface sampling (MSTIS) approach to sample the kinetic (un)folding network of Trp-cage mini-protein in explicit water. Cluster analysis yielded 14 important metastable states in the network. The MSTIS simulation thus resulted in a full 14 × 14 rate matrix. Analysis of the kinetic rate matrix indicates the presence of a near native intermediate state characterized by a fully formed alpha helix, a slightly disordered proline tail, a broken salt-bridge, and a rotated arginine residue. This intermediate was also found in recent IR experiments. Moreover, the predicted rate constants and timescales are in agreement with previous experiments and simulations.
High spatial resolution mapping of deposition layers on plasma facing materials by laser ablation microprobe time-of-flight mass spectroscopy
Authors: Xiao Qingmei , Li Cong , Hai Ran , Zhang Lei , Feng Chunlei , Zhou Yan , Yan Longwen , Duan Xuru , Ding Hongbin
Published: May 2014

A laser ablation microprobe time-of-flight mass spectroscopy (LAM-TOF-MS) system with high spatial resolution, ∼20 nm in depth and ∼500 μm or better on the surface, is developed to analyze the composition distributions of deposition layers on the first wall materials or first mirrors in tokamak. The LAM-TOF-MS system consists of a laser ablation microprobe combined with a TOF-MS and a data acquisition system based on a LabVIEW program software package. Laser induced ablation combined with TOF-MS is an attractive method to analyze the depth profile of deposited layer with successive laser shots, therefore, it can provide information for composition reconstruction of the plasma wall interaction process. In this work, we demonstrate that the LAM-TOF-MS system is capable of characterizing the depth profile as well as mapping 2D composition of deposited film on the molybdenum first mirror retrieved from HL-2A tokamak, with particular emphasis on some of the species produced during the ablation process. The presented LAM-TOF-MS system provides not only the 3D characterization of deposition but also the removal efficiency of species of concern.
Vapor liquid solid-hydride vapor phase epitaxy (VLS-HVPE) growth of ultra-long defect-free GaAs nanowires: Ab initio simulations supporting center nucleation
Authors: André Yamina , Lekhal Kaddour , Hoggan Philip , Avit Geoffrey , Cadiz Fabian , Rowe Alistair , Paget Daniel , Petit Elodie , Leroux Christine , Trassoudaine Agnès , Réda Ramdani M. , Monier Guillaume , Colas David , Ajib Rabih , Castelluci Dominique , Gil Evelyne
Published: May 2014

High aspect ratio, rod-like and single crystal phase GaAs nanowires (NWs) were grown by gold catalyst-assisted hydride vapor phase epitaxy (HVPE). High resolution transmission electron microscopy and micro-Raman spectroscopy revealed polytypism-free zinc blende (ZB) NWs over lengths of several tens of micrometers for a mean diameter of 50 nm. Micro-photoluminescence studies of individual NWs showed linewidths smaller than those reported elsewhere which is consistent with the crystalline quality of the NWs. HVPE makes use of chloride growth precursors GaCl of which high decomposition frequency after adsorption onto the liquid droplet catalysts, favors a direct and rapid introduction of the Ga atoms from the vapor phase into the droplets. High influxes of Ga and As species then yield high axial growth rate of more than 100 μm/h. The diffusion of the Ga atoms in the liquid droplet towards the interface between the liquid and the solid nanowire was investigated by using density functional theory calculations. The diffusion coefficient of Ga atoms was estimated to be 3 × 10−9 m2/s. The fast diffusion of Ga in the droplet favors nucleation at the liquid-solid line interface at the center of the NW. This is further evidence, provided by an alternative epitaxial method with respect to metal-organic vapor phase epitaxy and molecular beam epitaxy, of the current assumption which states that this type of nucleation should always lead to the formation of the ZB cubic phase.
Electronic state spectroscopy of diiodomethane (CH2I2): Experimental and computational studies in the 30 000–95 000 cm−1 region
Authors: Mandal Anuvab , Singh Param Jeet , Shastri Aparna , Jagatap B. N.
Published: May 2014

The electronic absorption spectrum of diiodomethane in the 30 000–95 000 cm−1 region is investigated using synchrotron radiation; the spectrum in the 50 000–66 500 cm−1 region is reported for the first time. The absorption bands in the 30 000–50 000 cm−1 region are attributed to valence transitions, while the vacuum ultraviolet (VUV) spectrum (50 000–95 000 cm−1) is dominated by several Rydberg series converging to the first four ionization potentials of CH2I2 at 9.46, 9.76, 10.21, and 10.56 eV corresponding to the removal of an electron from the outermost 3b2, 2b1, 1a2, and 4a1 non-bonding orbitals, respectively. Rydberg series of ns, np, and nd type converging to each of the four ionization potentials are assigned based on a quantum defect analysis. Time dependent density functional theory calculations of excited states support the analysis and help in interpretation of the Rydberg and valence nature of observed transitions. Density functional theory calculations of the neutral and ionic ground state geometries and vibrational frequencies are used to assign the observed vibronic structure. Vibronic features accompanying the Rydberg series are mainly due to excitation of the C-I symmetric stretch (ν3) and CH2 wag (ν8) modes, with smaller contributions from the C-H symmetric stretch (ν1). UV absorption bands are assigned to low lying valence states 11B2, 11B1, 21A1, 31A1, 21B1, and 21B2 and the unusually high underlying intensity in parts of the VUV spectrum is attributed to valence states with high oscillator strength. This is the first report of a comprehensive Rydberg series and vibronic analysis of the VUV absorption spectrum of CH2I2 in the 50 000–85 000 cm−1 region. The VUV absorption spectrum of CD2I2 which serves to verify and consolidate spectral assignments is also reported here for the first time.
Asymptotic solutions of the Oosawa model for the length distribution of biofilaments
Authors: Michaels Thomas C. T. , Garcia Gonzalo A. , Knowles Tuomas P. J.
Published: May 2014

Nucleated polymerisation phenomena are general linear growth processes that underlie the formation of a range of biofilaments in nature, including actin and tubulin that are key components of the cellular cytoskeleton. The conventional theoretical framework for describing this process is the Oosawa model that takes into account homogeneous nucleation coupled to linear growth. In his original work, Oosawa provided an analytical solution to the total mass concentration of filaments; the time evolution of the full length distribution has, however, been challenging to access, in large part due to the nonlinear nature of the rate equations inherent in the description of such phenomena and to date analytical solutions for the filament distribution are known only in certain special cases. Here, by exploiting a technique based on the method of matched asymptotics, we present an analytical treatment of the Oosawa model that describes the shape of the length distribution of biofilaments reversibly growing through primary nucleation and filament elongation. Our work highlights the power of matched asymptotics for obtaining closed-form analytical solutions to nonlinear master equations in biophysics and allows us to identify the key time scales that characterize biological polymerization processes.
Experimental cell for molecular beam deposition and magnetic resonance studies of matrix isolated radicals at temperatures below 1 K
Authors: Sheludiakov S. , Ahokas J. , Vainio O. , Järvinen J. , Zvezdov D. , Vasiliev S. , Khmelenko V. V. , Mao S. , Lee D. M.
Published: May 2014

We present the design and performance of an experimental cell constructed for matrix isolation studies of H and D atoms in solid H2/D2 films, which are created by molecular beam deposition at temperatures below 1 K. The sample cell allows sensitive weighing of the films by a quartz microbalance (QM) and their studies by magnetic resonance techniques in a strong magnetic field of 4.6 T. We are able to regulate the deposition rate in the range from 0.01 to 10 molecular layers/s, and measure the thickness with ≈0.2 monolayer resolution. The upper QM electrode serves as a mirror for a 128 GHz Fabry-Perot resonator connected to an electron spin resonance (ESR) spectrometer. H and D atoms were created by RF discharge in situ in the sample cell, and characterized by ESR and electron-nuclear double resonance. From the magnetic resonance measurements we conclude that the films are smooth and provide homogeneous trapping conditions for embedded atoms. The current sample cell design also makes it possible to calibrate the ESR signal and estimate the average and local concentrations of H and D radicals in the film.
Cu2ZnSnSxO4−x and Cu2ZnSnSxSe4−x: First principles simulations of optimal alloy configurations and their energies
Authors: Dun Chaochao , Holzwarth N. A. W. , Li Yuan , Huang Wenxiao , Carroll David L.
Published: May 2014

With the aim of exploring oxidation and selenization of the photovoltaic material Cu2ZnSnS4, we used first principles methods to study the structure and stability of Cu2ZnSnSxO4−x and Cu2ZnSnSxSe4−x alloys for 0 ≤ x ≤ 4. Pure Cu2ZnSnO4 was found to have the lowest heat of formation, followed by Cu2ZnSnS4, and finally Cu2ZnSnSe4. This suggests that oxidization is very likely to occur, whereas selenization can only be accomplished under high temperature. For the alloys, the energetically favorable chalcogen configurations are very different for oxygen and selenium. While the energies of the selenium alloys are insensitive to the distribution of S and Se configurations, the lowest energy oxygen alloys have alternating S and O sites in the a–b planes. In considering the heats of formation of the Cu2ZnSnSxO4−x alloys, we find that they are unstable with respect to decomposition into binary oxides and sulfides except for small concentrations of O. Our results also show that it is energetically more favorable to sulfurize Cu2ZnSnSe4 than to selenize Cu2ZnSnS4.
Enhanced flow of core-softened fluids through narrow nanotubes
Authors: Bordin José Rafael , Andrade José S. , Diehl Alexandre , Barbosa Marcia C.
Published: May 2014

We investigate through non-equilibrium molecular dynamic simulations the flow of anomalous fluids inside rigid nanotubes. Our results reveal an anomalous increase of the overall mass flux for nanotubes with sufficiently smaller radii. This is explained in terms of a transition from a single-file type of flow to the movement of an ordered-like fluid as the nanotube radius increases. The occurrence of a global minimum in the mass flux at this transition reflects the competition between the two characteristic length scales of the core-softened potential. Moreover, by increasing further the radius, another substantial change in the flow behavior, which becomes more evident at low temperatures, leads to a local minimum in the overall mass flux. Microscopically, this second transition is originated by the formation of a double-layer of flowing particles in the confined nanotube space. These nano-fluidic features give insights about the behavior of confined isotropic anomalous fluids.
Spontaneous chiral resolution in two-dimensional systems of patchy particles
Authors: Martínez-González J. A. , Chapela G. A. , Quintana-H J.
Published: May 2014

Short ranged potentials and their anisotropy produce spontaneous chiral resolution in a two dimensional model of patchy particles introduced in this paper. This model could represent an equimolar binary mixture (racemic mixture) of two kinds of chiral molecules (enantiomers) adsorbed to a bi-dimensional domain where only lateral short ranged interactions are present. Most racemic mixtures undergo chiral resolution due to their spatial anisotropy, the combined effect of long range forces and the thermodynamic conditions. The patchy particles are modeled as a hard disk and four different bonding sites located to produce chirality. Phase behavior and structural properties are analysed using Discontinuous Molecular Dynamics in the canonical ensemble. When the four patchy particles are separated by the angles {60°, 120°, 60°, 120°}, spontaneous chiral resolution is produced, given by the formation of homochiral clusters, if started from the corresponding racemic mixture. Gel behavior is also obtained in all the systems for low temperatures and low densities.
An induction method to calculate the complex permeability of soft magnetic films without a reference sample
Authors: Wei Jinwu , Wang Jianbo , Liu Qingfang , Li Xiaoyu , Cao Derang , Sun Xiaojun
Published: May 2014

A new analytical method has been proposed by utilizing an electromagnetic induction principle with a short-circuited microstrip line jig and the complex permeability spectra can be calculated without a known reference sample. The new method using the short-circuited microstrip line can exhibit higher sensitivity and a wider frequency band than coplanar waveguide and pick-up coil. Two magnetic thin films having a good in-plane uniaxial anisotropy are measured by using the induction method. The results show typical complex permeability spectra in good agreement with the theoretical analytical results. The measured permeability values are verified by comparing with the initial susceptibility derived from the sweeping field results. The difference of measured permeability values is less than 5%.
A long-pulse repetitive operation magnetically insulated transmission line oscillator
Authors: Fan Yu-Wei , Zhong Hui-Huang , Zhang Jian-De , Shu Ting , Liu Jin Liang
Published: May 2014

The improved magnetically insulated transmission line oscillator (MILO) is a gigawatt-class L-band high power microwave tube. It has allowed us to generate 3.1 GW pulse of 40 ns duration in the single-pulse operation and 500 MW pulse of 25 ns duration in the repetition rate operation. However, because of the severe impedance mismatch, the power conversion efficiency is only about 4% in the repetition rate operation. In order to eliminate the impedance mismatch and obtain repetitive long-pulse high-power microwave (HPM), a series of experiments are carried out and the recent progress is presented in this paper. In the single-pulse operation, when the diode voltage is 466 kV and current is 41.6 kA, the radiated microwave power is above 2.2 GW, the pulse duration is above 102 ns, the microwave frequency is about 1.74 GHz, and the power conversion efficiency is about 11.5%. In the repetition rate operation, under the condition of the diode voltage about 400 kV, beam current about 38 kA, the radiated microwave power is about 1.0 GW, the pulse duration is about 85 ns. Moreover, the radiated microwave power and the pulse duration decline little by little when the shot numbers increase gradually. The experimental results show that the impedance matching is a vital factor for HPM systems and one of the major technical challenges is to improve the cathode for the repetition rate operation MILO.
Non-contacting transfer of elastic energy into explosive simulants for dynamic property estimation
Authors: Greeney Nathan S. , Strovink Kurt M. , Scales John A. , Jessop Andrew M. , Stuart Bolton J. , Watson Christopher C. , Adams Douglas E.
Published: May 2014

Non-contacting acoustical methods can be used to extract various material properties of liquid or solid samples without disturbing the sample. These methods are useful even in the lab since they do not involve coupling anything to the sample, which might change its properties. A forteriori, when dealing with potentially dangerous materials, non-contacting methods may be the only safe solutions to mechanical characterization. Here, we show examples of using laser ultrasound to remotely insonify and monitor the elastic properties of several granular explosive simulants. The relatively short near-infrared laser pulse length (a few hundred nanoseconds) provides a broad-band thermoelastic source of ultrasound; we intentionally stay in the thermoelastic regime to avoid damaging the material. Then, we use a scanning laser Doppler vibrometer to measure the ultrasonic response of the sample. LDV technology is well established and very sensitive at ultrasonic frequencies; atomic level motions can be measured with modest averaging. The resulting impulse response of the explosive simulant can be analyzed to determine decay rates and wave speeds, with stiffer samples showing faster wave speeds and lower decay rates. On the other hand, at the low-frequency end of the acoustic spectrum, we use an electronically phased array to couple into a freely suspended sample's normal modes. This allows us to gently heat up the sample (3 °C in just under 5 min, as shown with a thermal IR camera). In addition to the practical interest in making the sample more chemically visible through heat, these two measurements (low-frequency resonant excitation vs high-frequency wave propagation) bracket the frequency range of acoustic non-destructive evaluation methods available.
Assessing the role of secondary electron emission on the characteristics of 6-cavity magnetrons with transparent cathode through particle-in-cell simulations
Authors: Qiu Hao , Prasad Sarita , Ludeking Lars , Joshi Ravi P. , Schamiloglu Edl
Published: May 2014

Effects of secondary electron emission (SEE) on the performance of a 6-cavity relativistic magnetron with transparent cathodes are probed through particle-in-cell simulations. Appropriate relations for the secondary electron yield have been developed and used. For comparisons, separate simulations have been performed with- and without electron cascading. Simulation results seem to indicate SEE to be detrimental to the power output due to deviations in the starting trajectories of secondary electrons, and the reduced fraction with synchronized rotational velocity. A higher reduction in output power is predicted with electron cascading, though mode competition was not seen at the 0.65 T field. A possible solution to mitigating SEE in magnetrons for high power microwave applications would be to alter the surface properties of emitting electrodes through irradiation, which can lead to graphitic film formation.
Highly efficient, broadband coherent surface-mixing-wave generation using amplified surface plasmonic polaritons
Authors: Zhu C. J. , Ren Y. , Zhao X. , Huang G. X. , Deng L. , Hagley E. W.
Published: May 2014

We show that coherent broadband surface mixing-wave (SMW) by a hyper-Raman process can be efficiently generated near a metallic surface abutting a quasi-three-level gain medium. The generation process is significantly enhanced by the amplified surface plasmonic polaritons (SPPs) in the gain layer, resulting in rapid growth of both fields. The highly efficient and directional amplified SPP and hyper-Raman SMW may facilitate engineering applications in which amplified-SPP propagation is desirable.
Critical sizes for the stabilization of coherent precipitates
Authors: Kumar Arun , Gautam Monika , Subramaniam Anandh
Published: May 2014

On growth of a precipitate beyond a critical size (r*), interfacial misfit dislocation loops are energetically stabilized. In the case of precipitation in (small) finite crystals, the energy of both the coherent precipitate and the dislocation loop are altered with respect to bulk crystals. Thus, as the crystal (domain) size approaches nanoscale, the critical size (r*) is expected to be altered with respect to bulk crystals. In the current investigation, finite element simulations are performed to study the variation of critical size (r*) with crystal/domain size and it is shown that below a critical domain size, the coherent precipitate is stabilized. Important findings include: (i) strain energy versus precipitate-size plot shows change in curvature for large precipitate sizes and (ii) coherent state is stable in two distinct regimes of precipitate sizes. Further, a phase diagram showing the stability regions of the coherent and semi-coherent states of the precipitate is drawn.
Dual band complementary metamaterial absorber in near infrared region
Authors: Pitchappa Prakash , Ho Chong Pei , Kropelnicki Piotr , Singh Navab , Kwong Dim-Lee , Lee Chengkuo
Published: May 2014

In this paper, we present the dual band absorption characteristics of complementary metamaterial absorber in near infrared (1.3–2.5 μm) region. The dual band absorption is caused by two distinct resonance mechanisms—electrical resonance and cavity resonance. Electrical resonance occurs in the metal layer—top complementary metamaterial and the cavity resonance occurs in the spacer cavity formed between the top complementary metamaterial and bottom metal reflector layers. In order to elucidate the resonant mechanisms and study the effects of geometrical variations on both the resonant absorption behaviours, two sets of experiment were performed. It was seen that with increasing complementary metamaterial pattern dimension, the electrical resonance absorption peak showed a blue shift, while the cavity resonance showed a slight red shift. However, on the other hand, for the increase in spacer thickness, the cavity resonance peak showed a strong red shift, while the electrical resonance peak remained uninfluenced. The reason for these geometrical dependencies, for both resonances, is conceptually analysed. Furthermore, the design was optimized to attain single absorption band by engineering the cavity and electrical resonances to be at the same wavelength. The single absorption band was successfully realized, however, the peak wavelength showed a red shift from the electrical resonance as in dual band absorber case. The reason for the shift was further explored to be caused due to the strong coupling of electrical and cavity resonances. This approach of utilizing different resonant mechanisms for absorption at different wavelengths provides the means to achieve multiband absorbers, using a simple design and low cost fabrication process.
Direct experimental determination of the anisotropic magnetoresistive effects
Authors: Perna P. , Maccariello D. , Rodrigo C. , Cuñado J. L. F. , Muñoz M. , Prieto J. L. , Niño M. A. , Bollero A. , Camarero J. , Miranda R.
Published: May 2014

We present an experimental study devoted to determine the magnetoresistive signals as imposed by the system magnetic anisotropy and applied current direction in a model ferromagnetic system. By having direct experimental access to the magnetization vector during the reversal (measured through angular- and field-dependent vectorial-resolved magnetization loops), we can predict both longitudinal and transverse magnetoresistive signals, i.e., anisotropic magnetoresistance and planar Hall effect. This has been done by experimentally disclosing the resistance changes occurring during (and simultaneously to) the magnetization reversal processes.
A uniform model for direct and converse magnetoelectric effect in laminated composite
Authors: Zhou Jian-Ping , Ma Yuan-Jun , Zhang Guang-Bin , Chen Xiao-Ming
Published: May 2014

Direct and converse magnetoelectric effects are two opposite processes, which were integrated in a model based on equivalent circuit. Following the piezoelectric and magnetostrictive constitutive equations, we obtained magnetic-mechanical-electric equations, and then built a symmetric equivalent circuit about the magnetoelectric coupling. We equivalently analyzed the direct and converse magnetoelectric effects with this equivalent circuit. The numerical calculations fit the reported results very well, including the magnetoelectric changes with the thickness ratio and frequency, the relative lower converse magnetoelectric resonance frequency, and the phase increase of π around the direct and converse magnetoelectric resonance frequencies. This model helps us understand the magnetoelectric properties deeply, especially for the converse magnetoelectric effect.
Note: A novel piezoelectrically driven pipette using centrifugal force
Authors: Deng Zhi Sen , Ma Yu Ting , Feng Zhi Hua
Published: May 2014

This paper proposes a novel piezoelectrically driven pipette, which utilizes centrifugal force in swing motion of a vibrating tube as the driving force, to input and output liquid at first bending resonant frequency. Control circuit capable of frequency tracking is designed. Pulse volume changing with different driving voltage amplitude, driving frequency, tip size, and target reagents are studied in experiments. The output pulse volume of a prototype pipette driven by voltage of 560 Vpp at 175.9 Hz is 43.2 μl with a variation of ±3.5%. Minimum water spots of 3 μl can be deposited in this manner. This pipette represents an alternative to standard liquid transfer techniques in chemical or biological experiments.
Communication: Nanosize-induced restructuring of Sn nanoparticles
Authors: Sabet Sareh , Kaghazchi Payam
Published: May 2014

Stabilities and structures of β- and α-Sn nanoparticles are studied using density functional theory. Results show that β-Sn nanoparticles are more stable. For both phases of Sn, nanoparticles smaller than 1 nm (∼48 atoms) are amorphous and have a band gap between 0.4 and 0.7 eV. The formation of band gap is found to be due to amorphization. By increasing the size of Sn nanoparticles (1–2.4 nm), the degree of crystallization increases and the band gap decreases. In these cases, structures of the core of nanoparticles are bulk-like, but structures of surfaces on the faces undergo reconstruction. This study suggests a strong size dependence of electronic and atomic structures for Sn nanoparticle anodes in Li-ion batteries.
Stable high temperature metamaterial emitters for thermophotovoltaic applications
Authors: Shemelya Corey , DeMeo Dante , Latham Nicole Pfiester , Wu Xueyuan , Bingham Chris , Padilla Willie , Vandervelde Thomas E.
Published: May 2014

We report a metamaterial design for a thermophotovoltaic (TPV) emitter. TPVs are similar to photovoltaic solar cells, but they convert heat to electricity instead of sunlight. The focus of this paper is on the emitter stage of the TPV system, which converts the heat into a spectral band which is easily absorbable by the TPV photodiode. The proposed structure consists of a platinum metallic element, an alumina dielectric spacer, and platinum grounding plane on a sapphire substrate. This perfect absorber based metamaterial emitter is shown to robustly operate at 600 °C. This temperature is high enough to enable TPV use for many industrial applications.
An operating condition fuzzy assessment strategy for large scale doubly-fed wind power generation system
Authors: Yunqi Xiao , Kunpeng Wang , Guanju He , Xiyun Yang
Published: May 2014

Timely and accurate assessment of wind turbine operating condition can save the maintenance cost effectively, because equipment repair and replacement for large wind turbine are expensive. Therefore, an efficient operating condition assessment strategy for wind turbine is proposed based on fuzzy synthesis method. First, the traditional fuzzy assessment process is introduced briefly a foundation for comparison. Second, a wind turbine assessment model is established and assessed in detail, with an improved fuzzy prediction strategy and de-fuzzy strategy. Finally, a comparison between the improved strategy and the traditional strategy is studied based on wind turbine operation data, and the results validate that the strategy proposed in this paper can alarm operation fault more promptly and efficiently, which is better for wind turbine operation safety and maintenance.
Room temperature magnetocaloric effect, critical behavior, and magnetoresistance in Na-deficient manganite La0.8Na0.1MnO3
Authors: Khlifi M. , Dhahri E. , Hlil E. K.
Published: May 2014

The La0.8Na0.1MnO3 oxide was prepared by the solid-state reaction and annealed in air. The X-ray diffraction data reveal that the sample is crystallized in a rhombohedral structure with R3¯c space group. Magnetic study shows a second-order magnetic phase transition from ferromagnetic to paramagnetic state at the Curie temperature TC = 295 K. In addition, the magnetizations as a function of temperature and the magnetic field is used to evaluate the magnetic entropy change ΔSM. Then, we have deduced that the La0.8Na0.1MnO3 oxide has a large magnetocaloric effect at room temperature. Such effect is given by the maximum of the magnetic entropy change ΔSMmax = 5.56, and by the Relative cooling power (RCP) factor which is equal to 235 under a magnetic field of 5 T. Moreover, the magnetic field dependence of the magnetic entropy change is used to determine the critical exponents β, γ, and δ which are found to be β = 0.495, γ = 1.083, and δ = 3.18. These values are consistent with the prediction of the mean field theory (β = 0.5, γ = 1, and δ = 3). Above all, the temperature dependence of electrical resistivity shows a metal–insulator transition at Tρ. The electrical resistivity decrease when we apply a magnetic field giving a magnetoresistance effect in the order of 60% at room temperature.
Pressure-induced amorphization in orthorhombic Ta2O5: An intrinsic character of crystal
Authors: Li Quanjun , Zhang Huafang , Cheng Benyuan , Liu Ran , Liu Bo , Liu Jing , Chen Zhiqiang , Zou Bo , Cui Tian , Liu Bingbing
Published: May 2014

The phase transition of orthorhombic Ta2O5 was investigated by in situ synchrotron X-ray diffraction and Raman spectroscopy. The orthorhombic phase transforms into an amorphous form completely at 24.7 GPa. A bulk modulus B0 = 139 (9) GPa for the orthorhombic Ta2O5 is derived from the P-V data. We suggest that the pressure-induced amorphization (PIA) in Ta2O5 can be attributed to the unstability of the a axis under high pressure leads to the connections of polyhedral breaking down and even triggers disorder of the whole crystal frame. These results demonstrate that the PIA is an intrinsic character of Ta2O5 which depends on its orthorhombic crystal structure rather than nanosize effects. This study provides a new kind of bulk material for investigating PIA in metal oxides.
Lattice thermal conductivity of nanograined half-Heusler solid solutions
Authors: Geng Huiyuan , Meng Xianfu , Zhang Hao , Zhang Jian
Published: May 2014

We report a phenomenological model of atomic weight, lattice constant, temperature, and grain size to calculate the high-temperature lattice thermal conductivity of nanograined solid solutions. The theoretical treatment developed here is reasonably consistent with the experimental results of n-type MNiSn and p-type MCoSb alloys, where M is the combination of Hf, Zr, and Ti. For disordered half-Heusler alloys with moderated grain sizes, we predict that the reduction in lattice thermal conductivity due to grain boundary scattering is independent of the scattering parameter, which characterizes the phonon scattering cross section of point defects. In addition, the lattice thermal conductivity falls off with temperature as T–1∕2 around the Debye temperature.
Chemical solution deposition of ferroelectric yttrium-doped hafnium oxide films on platinum electrodes
Authors: Starschich S. , Griesche D. , Schneller T. , Waser R. , Böttger U.
Published: May 2014

Ferroelectric hafnium oxide films were fabricated by chemical solution deposition with a remnant polarization of >13 μC/cm2. The samples were prepared with 5.2 mol. % yttrium-doping and the thickness varied from 18 nm to 70 nm. The hafnium oxide layer was integrated into a metal-insulator-metal capacitor using platinum electrodes. Due to the processing procedure, no thickness dependence of the ferroelectric properties was observed. To confirm the ferroelectric nature of the deposited samples, polarization, capacitance, and piezoelectric displacement measurements were performed. However, no evidence of the orthorhombic phase was found which has been proposed to be the non-centrosymmetric, ferroelectric phase in HfO2.
Review of the phytogeography of Cape York Peninsula: a flora that illustrates the development of the Australian sclerophyll biota
Authors: Wannan Bruce
Published: May 2014

Paleontological records from north-eastern Australia suggest that Cape York Peninsula is likely to have retained a warm and humid environment throughout the Cenozoic. The cooling and drying trend of the last 15 million years has been moderated on Cape York Peninsula by its position on the northern leading edge of the continent, its maritime or aquatic influences and partly montane topography. Cape York Peninsula shares a close geographic relationship with New Guinea, with 40% of its species shared, but has a distinctively separate flora that includes 330 bioregionally endemic plant species and five bioregionally endemic plant genera. Comparison with the monsoon savanna areas of Western Australia (Kimberley) and Northern Territory (Top End) suggests that Cape York Peninsula has a much richer rainforest flora. The non-rainforest flora of all three areas contains a significant regional element. The Peninsula has a mix of plant communities that are similar to those identified from Australia’s vegetation in the Cenozoic including rainforest, woodlands and grasslands. Cape York Peninsula demonstrates the mosaic of these environments, which were typical of much of Australia during the Cenozoic but which were lost in most areas during the cooling and drying of the Pliocene and Quaternary. The fossil record and dated phylogenies suggest that some of the taxa first evident in Australia during the Cenozoic are still growing on Cape York Peninsula. In the Myrtaceae and Poaceae, Cape York Peninsula demonstrates nationally and internationally significant taxonomic diversity. Its taxa are related to many that emerged in the forests of the Paleocene and to taxa which became dominant following the drying of the Miocene. The Peninsula contains elements which represent both older and modern lineages of many families in Australia. The phytogeographic significance of Cape York Peninsula is that it has a highly diverse flora, which contains plant communities and taxa that demonstrate the development of the sclerophyll biota in Australia during the Cenozoic.
Phosphorus content of the soil influences the growth and productivity of Themeda triandra Forssk. and Microlaena stipoides (Labill.) R.Br.
Authors: Clark Cameron E. F. , Mitchell Meredith L. , Islam Mohammed R. , Jacobs Brent
Published: May 2014

Despite native grasses occupying a large area of land in Australia, there has been limited work on the responses of these species to the addition of phosphorus (P). The main objective of this study was to investigate the effect of the addition of P to create a range of P contents in the soil on the productivity and morphology of two native grasses at two times of harvests. Two contrasting perennial native grasses, namely kangaroo grass (Themeda triandra Forssk. syn. T. australis R. Br. Stapf) and weeping grass [Microlaena stipoides var. stipoides (Labill.) R. Br.] were grown in a glasshouse with the addition of P to create five contents of P in the soil (7, 17, 32, 107 and 307 mg kg–1 soil) using a completely randomised design with four replicates per treatment. Grasses were harvested to 5 cm above the substrate surface, and the number of tillers and leaf area were recorded on Day 84 (harvest 1) and Day 112 (harvest 2) of the experiment. Dry matter production for kangaroo and weeping grass increased with P contents of the soil of 32 mg and ≥107 mg P kg–1 soil, respectively. Increased dry matter production for both species was the result of increased leaf area, tiller number and root growth. These results provide data that help to understand the disappearance sequence of kangaroo grass from more fertile soils and an increase in weeping grass, particularly in soils with greater fertility. Further research is required to determine if these results hold for other grass ecotypes.
Modern fire regime resembles historical fire regime in a ponderosa pine forest on Native American lands
Authors: Stan Amanda B. , Fulé Peter Z. , Ireland Kathryn B. , Sanderlin Jamie S.
Published: May 2014

Forests on tribal lands in the western United States have seen the return of low-intensity surface fires for several decades longer than forests on non-tribal lands. We examined the surface fire regime in a ponderosa pine-dominated (Pinus ponderosa) forest on the Hualapai tribal lands in the south-western United States. Using fire-scarred trees, we inferred temporal (frequency and seasonality) and spatial (synchrony) attributes and regulators of the fire regime over three land-use periods (historical, suppression, modern) between 1702 and 2007. Patterns of fire frequency and synchrony were similar, but fire seasonality was dissimilar, between the historical and modern periods. Logistic regression and generalised linear mixed models identified a suite of variables representing fuels, climate and human land uses that were associated with the probability of a site burning. Combined, these results allow for valuable insights regarding past fire spread and variability in fire frequency throughout our study area. In some respects, the current distinct fire regime in our study area, which predominately consists of prescribed fires implemented since the 1960s, resembles the past frequent surface fire regime that occurred here and in similar forest types on non-tribal lands in the south-western United States. Our results will be useful for informing adaptive management throughout the region as climate warms.
Feeling the hidden mechanical forces in lipid bilayer is an original sense
Authors: Anishkin Andriy , Loukin Stephen H. , Teng Jinfeng , Kung Ching
Published: May 2014

Life’s origin entails enclosing a compartment to hoard material, energy, and information. The envelope necessarily comprises amphipaths, such as prebiotic fatty acids, to partition the two aqueous domains. The self-assembled lipid bilayer comes with a set of properties including its strong anisotropic internal forces that are chemically or physically malleable. Added bilayer stretch can alter force vectors on embedded proteins to effect conformational change. The force-from-lipid principle was demonstrated 25 y ago when stretches opened purified
Escherichia coli
MscL channels reconstituted into artificial bilayers. This reductionistic exercise has rigorously been recapitulated recently with two vertebrate mechanosensitive K
+
channels (TREK1 and TRAAK). Membrane stretches have also been known to activate various voltage-, ligand-, or Ca
2+
-gated channels. Careful analyses showed that Kv, the canonical voltage-gated channel, is in fact exquisitely sensitive even to very small tension. In an unexpected context, the canonical transient-receptor-potential channels in the
Drosophila
eye, long presumed to open by ligand binding, is apparently opened by membrane force due to PIP
2
hydrolysis-induced changes in bilayer strain. Being the intimate medium, lipids govern membrane proteins by physics as well as chemistry. This principle should not be a surprise because it parallels water’s paramount role in the structure and function of soluble proteins. Today, overt or covert mechanical forces govern cell biological processes and produce sensations. At the genesis, a bilayer’s response to osmotic force is likely among the first senses to deal with the capricious primordial sea.
Molecular-crowding effects on single-molecule RNA folding/unfolding thermodynamics and kinetics
Authors: Dupuis Nicholas F. , Holmstrom Erik D. , Nesbitt David J.
Published: May 2014

Significance

The cell cytoplasm is a multicomponent solution that is much more concentrated than typically sampled in conventional in vitro studies. The presence of cosolutes can strongly influence biomolecular folding due to “molecular-crowding” effects, which are poorly understood and yet crucial to understand. In this study, the thermodynamics/kinetics of “crowding” effects are probed at the single-molecule level for an isolated RNA tertiary interaction. We observe dramatic stabilization of the folded state and, for the first time (to our knowledge), establish the kinetic origin of molecular crowding to be dominated by entropic acceleration of folding.