bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro and in vivoactivity of the chloroaryl-substituted imidazole viniconazole againstTrypanosoma cruzi
Authors: DA SILVA CRISTIANE FRANÇA , BATISTA DENISE DA GAMA JAEN , BATISTA MARCOS MEUSER , LIONEL JESSICA , HAMMER ERICA RIPOLL , BRUN RETO , SOEIRO MARIA DE NAZARÉ CORREIA
Published: October 2013

Chagas disease (CD) is caused by the intracellular protozoan parasiteTrypanosoma cruziand affects more than 10 million people in poor areas of Latin America. There is an urgent need for alternative drugs with better safety, broader efficacy, lower costs and shorter time of administration. Thus the biological activity of viniconazole, a chloroaryl-substituted imidazole was investigated usingin vitroandin vivoscreening models ofT. cruziinfection. Ultrastructural findings demonstrated that the most frequent cellular damage was associated with plasma membrane (blebs and shedding events), Golgi (swelling aspects) and the appearance of large numbers of vacuoles suggesting an autophagic process. Our data demonstrated that although this compound is effective against bloodstream and intracellular forms (16 and 24 μm, respectively)in vitro, it does not presentin vivoefficacy. Due to the urgent need for novel agents againstT. cruzi, the screening of natural and synthetic products must be further supported with the aim of finding more selective and affordable drugs for CD.
ON THE ASYMPTOTIC EFFICIENCY OF GMM
Authors: Carrasco Marine , Florens Jean-Pierre
Published: October 2013

The efficiency of the generalized method of moment (GMM) estimator is addressed by using a characterization of its variance as an inner product in a reproducing kernel Hilbert space. We show that the GMM estimator is asymptotically as efficient as the maximum likelihood estimator if and only if the true score belongs to the closure of the linear space spanned by the moment conditions. This result generalizes former ones to autocorrelated moments and possibly infinite number of moment restrictions. Second, we derive the semiparametric efficiency bound when the observations are known to be Markov and satisfy a conditional moment restriction. We show that it coincides with the asymptotic variance of the optimal GMM estimator, thus extending results by Chamberlain (1987,Journal of Econometrics34, 305–33) to a dynamic setting. Moreover, this bound is attainable using a continuum of moment conditions.
Research gaps in understanding how climate change will affect arboviral diseases
Authors: Baylis Matthew
Published: October 2013

Climate change is widely expected to cause the emergence and spread of vector-borne diseases, and predictive models are needed so that we can be prepared. We developed a climate-sensitive, predictive, model that describes the risk of bluetongue, an arboviral disease of ruminants, which has emerged dramatically in Europe. Developing the predictive bluetongue model led to the identification of numerous gaps in both the understanding and the availability of data. These mostly pertain to the vectors and their interaction with hosts. Closing these gaps will allow better models, with more precise predictions, to be produced. These research gaps apply to many other arboviral diseases as well. As a consequence, there needs to be an increase in research on the vectors that transmit arboviral diseases. Priorities are the training of a new generation of taxonomists, studies on the field biology of potential vectors, and increased coordination of vector surveillance and recording between countries facing similar threats.
Increasing Predictive Estimations Without Further Learning
Authors: Struyf Dieter , Iberico Carlos , Vervliet Bram
Published: October 2013

The peak of learned responding normally occurs at the learning stimulus itself, but can shift to a different stimulus after discriminative learning. This provides important information about the nature of the generalization mechanism, and reveals alternative pathways through which learned responses can increase. Over two experiments, we established the peak-shift effect in a human predictive learning paradigm. Participants were asked to predict the occurrence of a neutral outcome (drawing of a lightning bolt) based on preceding geometrical figures (rings of different sizes). During learning, the middle-sized ring was sometimes followed by the outcome, whereas a larger ring was never followed by the outcome. At test, we presented larger and smaller rings (Experiment 1), or only a slightly smaller ring (Experiment 2). We consistently observed highest prediction of the outcome to the slightly smaller ring. Predictive estimations in humans can reach their height to stimuli that have never actually participated in the learning experiences. We argue that the results are most in line with an associative learning account, rather than an adaptation-level or a rule-learning account.
Allosteric coupling of the inner activation gate to the outer pore of a potassium channel
Authors: Peters Christian J. , Fedida David , Accili Eric A.
Published: October 2013

In potassium channels, functional coupling of the inner and outer pore gates may result from energetic interactions between residues and conformational rearrangements that occur along a structural path between them. Here, we show that conservative mutations of a residue near the inner activation gate of the Shaker potassium channel (I470) modify the rate of C-type inactivation at the outer pore, pointing to this residue as part of a pathway that couples inner gate opening to changes in outer pore structure and reduction of ion flow. Because they remain equally sensitive to rises in extracellular potassium, altered inactivation rates of the mutant channels are not secondary to modified binding of potassium to the outer pore. Conservative mutations of I470 also influence the interaction of the Shaker N-terminus with the inner gate, which separately affects the outer pore.
Electrically Controlled Membranes Exploiting Cassie-Wenzel Wetting Transitions
Authors: Bormashenko Edward , Pogreb Roman , Balter Sagi , Aurbach Doron
Published: October 2013

We report electrically controlled membranes which become permeable when an electrical field is exerted on a droplet deposited on the membrane. Micro-porous polycarbonate membranes are obtained with the breath-figures assembly technique, using micro-scaled stainless steel gauzes as supports. The membranes demonstrate pronounced Cassie-Baxter wetting. Air cushions trapped by the droplet prevent water penetration through the membrane. We demonstrate two possibilities for controlling the permeability of the membrane, namely contact and non-contact scenarios. When an electrical field is exerted on a droplet deposited on the membrane, the triple-line is de-pinned and the wetting transition occurs in the non-contact scheme. Thus, the membrane becomes permeable. The contact scheme of the permeability control is based on the electrowetting phenomenon.
Multiuser analogue network coding with code division multiple access
Authors: Mao Shunfu , Lee Jungwoo
Published: October 2013

An analogue network coding technique combined with asynchronous code division multiple access is proposed. A scenario is considered where there are multiple pairs of nodes with a single relay and where each pair of nodes exchange information asynchronously. With the assumption of asynchronous transmission, the analysis and the simulations show a trade‐off between the number of nodes and the inter‐user interference because the spreading codes are not orthogonal to each other. The analysis also shows that analogue network coding improves throughput compared with the conventional routing protocol with a large Eb/N0, a low number of users and a large spreading factor.
Simplified circuit and modulation scheme for five‐phase three‐level voltage source inverter
Authors: Liu Hongchen , Wang Guoli , Yu Hailong
Published: October 2013

The simplified circuit and modulation scheme is presented for a five‐phase three‐level voltage source inverter (FPTL‐VSI). The simplified FPTL‐VSI is a concatenation of a dual‐buck stage and a two‐level VSI (TL‐VSI), and the space vector pulse width modulation (SVPWM) is used as the modulation scheme. Owing to the merit of the dual‐buck stage which uses only four controllable switching devices, the TL‐VSI can produce a three‐level voltage waveform. By simplification of the space voltage vectors, a simplified SVPWM scheme can be obtained. Thus, the simplified FPTL‐VSI reduces the hardware costs and improves the quality of the output voltage waveforms. Furthermore, the hardware implementation of the simplified SVPWM scheme can be easily realised. The experimental results prove the feasibility and validity of the proposed inverter and the modulation scheme.
Multi‐target tracking using social force model in discrete‐continuous optimisation framework
Authors: Bang G. , Kweon I.‐S.
Published: October 2013

A multi‐target tracking algorithm in dense‐crowded environments is proposed. Existing global optimisation based multi‐target tracking assumes that each pedestrian's motion is independent and shows impressive results in sparse datasets. However, in semi‐crowded environments, pedestrians often occlude and interact with each other, making tracking a challenging task. In this reported work, social group behaviour to mitigate ambiguities is considered using the social force model, which is widely used in crowd simulation applications, and the robustness of the proposed method compared to state‐of‐the‐art multi‐target tracking in more crowded scenarios is demonstrated.
Miniaturised microstrip lowpass filter with sharp roll‐off and ultra‐wide stopband
Authors: Karimi Gh. , Khamin‐Hamedani F. , Siahkamari H.
Published: October 2013

A new semi‐fractal technique is applied to hairpin microstrip lowpass filters to realise compact size and sharp roll‐off. To achieve wide stopband suppression, both a semi‐fractal hairpin resonator and a U‐shaped resonator are employed in the filter. A demonstration filter with 3 dB cutoff frequency at 1.51 GHz has been designed, fabricated and measured. The results show that a roll‐off of 217.6 dB/GHz with a relative stopband bandwidth of 159.7% (referred to a suppression degree of 32 dB) can be obtained while achieving a high figure‐of‐merit of 44 832.
Miniaturised wideband circularly‐polarised log‐periodic Koch fractal antenna
Authors: Liu Guo , Xu Liang , Wu Zhensen
Published: October 2013

A small size wideband (2–6 GHz) circularly‐polarised log‐periodic Koch fractal antenna (LPKFA) is proposed. The circular polarisation is produced by using a pair of unequal length crossed‐dipoles, and the wideband property is achieved based on the concept of the log‐periodic dipole antenna without a matching network. In addition, Koch‐shaped dipoles are used as the radiation elements in the design.
0.013 mm2, kHz‐to‐GHz‐bandwidth, third‐order all‐pole lowpass filter with 0.52‐to‐1.11 pW/pole/Hz efficiency
Authors: Chen Yong , Mak Pui‐In , Zhang Li , Qian He , Wang Yan
Published: October 2013

A third‐order all‐pole analogue lowpass filter (LPF) with kHz‐to‐GHz bandwidth tunability is proposed. It embeds a current‐reuse active inductor into a current‐scalable source follower to realise three concurrently tunable poles in a single branch. The LPF fabricated in 0.18 μm CMOS measures a tunable − 3 dB cutoff from 0.8 kHz to 1.2 GHz, under a scalable power of 1.25 nW to 4.01 mW. Owing to no tuning capacitor, the die area is extremely compact (0.013 mm2) and the achieved filter efficiency is 0.52 to 1.11 pW/pole/Hz.
High‐efficiency fast‐transient‐response V2‐controlled boost converter with small ESR capacitor
Authors: Hwang Yah‐Shyan , Shen Jian‐Hong , Chen Jiann‐Jong
Published: October 2013

A high‐efficiency fast‐transient‐response V2‐controlled boost converter with a small equivalent series resistance (ESR) capacitor is presented. The proposed boost converter can achieve a fast and stable load transient response without relying on the ESR of the output capacitor. The switching frequency of the proposed boost converter is 500 kHz for a nominal 2.5–4.2 V input and a 3.3–5 V output application. Experimental results show that the transient recovery time inheriting the advantage of V2 control is shorter than 6.4 µs with the load step from 250 to 20 mA and the highest efficiency can be up to 95.4%. The proposed boost converter has been fabricated with a 0.35 µm 2P4M CMOS process, the total chip area is about 1.5 × 1.5 mm2, including the PADs.
Frequency reconfigurable patch antenna using liquid metal as switching mechanism
Authors: Kelley M. , Koo C. , McQuilken H. , Lawrence B. , Li S. , Han A. , Huff G.
Published: October 2013

The use of liquid metal as a switching mechanism for a frequency‐reconfigurable edge‐fed microstrip patch antenna designed to operate in either the 2.4 GHz ISM band or the 1.6 GHz GPS band is illustrated. A partitioned fluidic manifold bonded to the top of the antenna enables the pressure‐driven displacement of a low‐loss dielectric fluid and the liquid metal from a reservoir atop the patch to switch between the two antenna states. Fabrication and measurement of the antenna illustrates the use of fluidics as an alternative to RF switches for reconfigurable antennas.
Equalisation digital on‐channel repeater with a feedback interference canceller for the advanced television systems committee terrestrial digital television system
Authors: Park Sung Ik , Lee Young‐Jun , Kim Heung Mook , Kim Hyoung‐Nam
Published: October 2013

In this study, the authors propose a novel equalisation digital on‐channel repeater (EDOCR) with a feedback interference canceller (FIC) for a single frequency network of the advanced television systems committee terrestrial digital television system. The proposed EDOCR with an FIC not only has high output power by the cancellation of feedback signals caused by insufficient antenna isolation through the FIC, but also shows better quality of output signals than conventional digital on‐channel repeaters (DOCRs) by removing multipath signals existing between the main transmitter and DOCR, as well as residual feedback signals through an equaliser. Computer simulation results are provided to demonstrate the superior performance of the proposed EDOCR with an FIC.
Optimal energy harvesting from a high‐speed brushless DC generator‐based flywheel energy storage system
Authors: Gurumurthy Salinamakki Ramabhatta , Agarwal Vivek , Sharma Archana
Published: October 2013

Brushless DC (BLDC) motors are highly suitable for usage in high‐speed applications like flywheel energy storage. A bidirectional power converter (BDC) interfaces the DC power source to BLDC machine which is coupled to the flywheel. The BDC acts as an energy harvesting converter (EHC) (in voltage boosting mode) during extraction of stored energy from the flywheel. However, usually an optimal energy is not extracted because of limitation on the maximum gain of the EHC and equivalent source resistance (Rs) of the generator. This study presents the effects of generator parameters on EHC and relevant analysis for the extraction of optimum energy stored in the flywheel. Existing literature on a similar system does not consider the effect Rs of the generator on the BDC's performance. If RL is the load resistance, then as the Rs/RL ratio increases, maximum voltage gain and operating duty cycle range decrease. Rs can be reduced by designing machine/chokes using low loss core material like nickel–iron or cobalt–iron. This study also deals with the design and implementation of the controller for EHC taking Rs of the generator into consideration. Studies on the effect of Rs on the converter harvestable energy have been conducted and the experimental results are included.
Simple sensorless algorithm for interior permanent magnet synchronous motors based on high‐frequency voltage injection method
Authors: Park Nae‐Chun , Kim Sang‐Hoon
Published: October 2013

This study presents a simple sensorless algorithm based on the high‐frequency signal injection for an interior permanent magnet synchronous motor. The sensorless drive using a square‐wave‐type injection signal has an enhanced control bandwidth and reduced acoustic noise owing to the reduction of filters and availability of high injection frequency. However, this method still needs discrete filters to extract the fundamental and the injected frequency component currents; so it has a limitation in enhancing the sensorless control performance. Therefore this study proposes a simple algorithm, which eliminates these filters and further simplifies the signal process for estimating the rotor position. As a result, the overall sensorless control can be implemented easily without any filters while providing an enhanced dynamics. Additionally, a detection method of an initial rotor position for start‐up by using the same square‐wave‐type voltage injection is introduced. The experimental result shows that the speed control bandwidth in the sensorless drive simplified by the proposed algorithm becomes very close to the one achieved in sensored drives.
Commutation technique in the supply of electromagnetic actuators
Authors: Balan Horia , Tirnovan Radu , Buzdugan Mircea I.
Published: October 2013

This study presents some specific problems concerning the DC–AC commutation of the power converters used in frequency controlled electromagnetic actuators. Starting from the initial conditions imposed for a low‐cost simple inverter used for driving an electromagnetic vibrator, two commutation possibilities are analysed (unmodulated voltages and simple modulated voltages). The harmonic analysis performed in this study, permitted the analytic determination of the load current distortion coefficient against the control angle in the case of simple modulated voltage. The energetic performances (the real power and the power factor) of the system were evaluated through the power factor, determined analytically as a function of the operating frequency and the control angle α. The influence of the control angle on the current distortion factor has been highlighted experimentally using a programmable source, which allowed the synthesis of different waveforms at different frequencies. The novelty of this study consists in the analysis of the influence of the control variable angle α on energy parameters of electromagnetic vibrators, which allows a lower distortion factor and an appropriate power factor, both at a lower cost and lower commutation losses compared with pulse width modulation converters. Section 1 presents the technologies using commutation techniques analysed in Sections 2 and 3; Section 4 represents an analysis of the energetic performances, whereas in Section 5 experimental results for a vibro‐compaction equipment are presented.
Modified one‐cycle‐controlled three‐phase pulse‐width modulation rectifiers with a reduced switching frequency to power line frequency ratio
Authors: Wei Zheng , Chen Xin , Chen Jie , Gong Chun‐ying , Fan Yi , Chen Jia‐wei
Published: October 2013

In the aircraft power systems with 360–800 Hz line frequency or medium‐ and high‐power three‐phase pulse‐width modulation (PWM) rectifier applications operating at the utility line frequency (50/60 Hz), the ratio of switching frequency to power line frequency will be reduced because of the increased line frequency or low switching frequency. Therefore the assumptions that the average voltage drop across the input inductor of the PWM rectifiers can be neglected if the conventional one‐cycle controlled (OCC) method had been adopted can no longer be true anymore, which will deteriorate the system power factor (PF) dramatically. To solve this issue, a modified OCC scheme is proposed in this study. The proposed control method can improve the input PF of three‐phase PWM rectifier without sacrificing the advantages of the conventional OCC scheme, such as no phase‐locked loop and constant switching frequency. The control equation of the modified OCC method, which considered the voltage drop across the input inductor, is first derived. The theoretic analysis is supported by the experimental verification performed by a 2.5 kW modified OCC‐based three‐phase three‐switch Vienna rectifier.
Analysis and investigation of energy transmission process in different operating modes of Sepic converter
Authors: Babaei Ebrahim , Seyed Mahmoodieh Mir Esmaeel
Published: October 2013

This study investigates the energy transmission process of the Sepic converter in each of its operating modes. In this converter, the continuous conduction mode (CCM) is classified into two complete inductor supply mode (CISM) and incomplete inductor supply mode (IISM). The discontinuous CM (DCM) of the converter just contains an interval of IISM. The equivalent critical inductances between CISM–IISM and CCM–DCM are calculated in this study. In addition, for a specific range of input voltage and load resistance, the minimum and maximum values of the equivalent critical inductances are obtained. The minimum and maximum values of the equivalent critical inductances are calculated in such a manner that the converter operates in one of CISM‐CCM, IISM‐CCM and IISM‐DCM in whole of the operational area. The experimental results are used to prove the validity of the presented theoretical subjects.
Non‐linear coefficient of BaTiO3‐doped ZnO varistor
Authors: Kharchouche Fayçal , Belkhiat Saâd , Belkhiat Djamel Eddine Chouaib
Published: October 2013

The effect of additions up to 9.6%wt BaTiO3 on grain growth and microstructure in ZnO samples sintered at 1300°C has been studied using scanning electron microscopy, energy dispersive X‐ray, X‐ray diffraction and impedance analyser as techniques. The sample doped with 1.6%wt BaTiO3, leads to grain size increasing and forms (BaO10.89Ti3.93Zn2.03 and Ba4O27Ti11 Zn) solid solutions with ZnO. A homogeneous structure was obtained whereas with further additions 3%wt the structure was inhomogeneous and the solid solutions formed in the first segregate to grain boundaries. Afterwards, an excess of 9.6%wt BaTiO3 leads to BaTiO3 phase segregation locating on the surface of the sample and in the grain boundaries near the junctions between matrix grains. Experimental I–V current‐voltage characteristics show that BaTiO3 as additive in ZnO varistors, increases the non‐linear coefficient (α) and the breakdown voltage. The highest non‐linearity was obtained for 9.6%wt BaTiO3 content with α = 121.03 and 1.79 µA in leakage current. The average breakdown voltage per grain boundary (Vgb) was evaluated in the ranges 1.7–3.46 V/gb and 1.34–2.54 V/gb in agreement with the literature.
Cavity‐first approach for microelectromechanical system–CMOS monolithic integration
Authors: Lu Jian , Zhang Lan , Takagi Hideki , Maeda Ryutaro
Published: October 2013

Presented is a cavity‐first approach for producing released microelectromechanical system (MEMS) structures from the front side of a silicon on insulator (SOI) wafer. This approach shows excellent process compatibilities to CMOS and is significantly valuable to MEMS–CMOS monolithic integration. In this approach, prior to metal layer deposition and other components fabrication, which are easily damaged by vapour‐phase hydrofluoric (HF) acid, release holes with a diameter of a few micrometres were created in the active silicon layer, and the cavities were formed after removing the underneath SiO2 box layer by vapour‐phase HF etching. An amorphous fluoropolymer thin film was then successfully introduced to refill those release holes without entering into the cavities, after which the wafer can be fabricated by standard process with negligible surface fluctuation. Finally, MEMS structures were released from the front side of the wafer by inductively coupled plasma reactive ion etching (ICP‐RIE). This approach enables monolithic integration of MEMS with CMOS circuits on SOI wafers with easy‐package capability, eliminates the requirements on device release by wet chemical etching or ICP‐RIE from the backside of the wafer and reduces the risk of device damage by vapour‐phase HF etching. This approach also excels others in simplicity and high yields with better thickness uniformity and less residual stress in a MEMS structure.
Ab initio analytical Raman intensities for periodic systems through a coupled perturbed Hartree-Fock/Kohn-Sham method in an atomic orbital basis. II. Validation and comparison with experiments
Authors: Maschio Lorenzo , Kirtman Bernard , Rérat Michel , Orlando Roberto , Dovesi Roberto
Published: October 2013

In this work, we validate a new, fully analytical method for calculating Raman intensities of periodic systems, developed and presented in Paper I [L. Maschio, B. Kirtman, M. Rérat, R. Orlando, and R. Dovesi, J. Chem. Phys. 139, 164101 (2013)]. Our validation of this method and its implementation in the CRYSTAL code is done through several internal checks as well as comparison with experiment. The internal checks include consistency of results when increasing the number of periodic directions (from 0D to 1D, 2D, 3D), comparison with numerical differentiation, and a test of the sum rule for derivatives of the polarizability tensor. The choice of basis set as well as the Hamiltonian is also studied. Simulated Raman spectra of α-quartz and of the UiO-66 Metal-Organic Framework are compared with the experimental data.
Intermittency in 2D soap film turbulence
Authors: Cerbus R. T. , Goldburg W. I.
Published: October 2013

The Reynolds number dependency of intermittency for 2D turbulence is studied in a flowing soap film. The Reynolds number used here is the Taylor microscale Reynolds number Rλ, which ranges from 20 to 800. Strong intermittency is found for both the inverse energy and direct enstrophy cascades as measured by (a) the pdf of velocity differences P(δu(r)) at inertial scales r, (b) the kurtosis of P(∂xu), and (c) the scaling of the so-called intermittency exponent μ, which is zero if intermittency is absent. Measures (b) and (c) are quantitative, while (a) is qualitative. These measurements are in disagreement with some previous results but not all. The velocity derivatives are nongaussian at all Rλ but show signs of becoming gaussian as Rλ increases beyond the largest values that could be reached. The kurtosis of P(δu(r)) at various r indicates that the intermittency is scale dependent. The structure function scaling exponents also deviate strongly from the Kraichnan prediction. For the enstrophy cascade, the intermittency decreases as a power law in Rλ. This study suggests the need for a new look at the statistics of 2D turbulence.
Statistical mechanics of DNA rupture: Theory and simulations
Authors: Nath S. , Modi T. , Mishra R. K. , Giri D. , Mandal B. P. , Kumar S.
Published: October 2013

We study the effects of the shear force on the rupture mechanism on a double stranded DNA. Motivated by recent experiments, we perform the atomistic simulations with explicit solvent to obtain the distributions of extension in hydrogen and covalent bonds below the rupture force. We obtain a significant difference between the atomistic simulations and the existing results in the literature based on the coarse-grained models (theory and simulations). We discuss the possible reasons and improve the coarse-grained model by incorporating the consequences of semi-microscopic details of the nucleotides in its description. The distributions obtained by the modified model (simulations and theoretical) are qualitatively similar to the one obtained using atomistic simulations.
Comparison of atmospheric air plasmas excited by high-voltage nanosecond pulsed discharge and sinusoidal alternating current discharge
Authors: Zhang Shuai , Wang Wen-chun , Jiang Peng-chao , Yang De-zheng , Jia Li , Wang Sen
Published: October 2013

In this paper, atmospheric pressure air discharge plasma in quartz tube is excited by 15 ns high-voltage nanosecond pulsed discharge (HVNPD) and sinusoidal alternating current discharge (SACD), respectively, and a comparison study of these two kinds of discharges is made through visual imaging, electrical characterization, optical detection of active species, and plasma gas temperature. The peak voltage of the power supplies is kept at 16 kV while the pulse repetition rate of nanosecond pulse power supply is 100 Hz, and the frequency of sinusoidal power supply is 10 kHz. Results show that the HVNPD is uniform while the SACD presents filamentary mode. For exciting the same cycles of discharge, the average energy consumption in HVNPD is about 1/13 of the SACD. However, the chemical active species generated by the HVNPD is about 2–9 times than that excited by the SACD. Meanwhile, the rotational and vibrational temperatures have been obtained via fitting the simulated spectrum of N2 (C3Πu → B3Πg, 0-2) with the measured one, and the results show that the plasma gas temperature in the HVNPD remains close to room temperature whereas the plasma gas temperature in the SACD is about 200 K higher than that in HVNPD in the initial phase and continually increases as discharge exposure time goes on.
Local order variations in confined hard-sphere fluids
Authors: Nygård Kim , Sarman Sten , Kjellander Roland
Published: October 2013

Pair distributions of fluids confined between two surfaces at close distance are of fundamental importance for a variety of physical, chemical, and biological phenomena, such as interactions between macromolecules in solution, surface forces, and diffusion in narrow pores. However, in contrast to bulk fluids, properties of inhomogeneous fluids are seldom studied at the pair-distribution level. Motivated by recent experimental advances in determining anisotropic structure factors of confined fluids, we analyze theoretically the underlying anisotropic pair distributions of the archetypical hard-sphere fluid confined between two parallel hard surfaces using first-principles statistical mechanics of inhomogeneous fluids. For this purpose, we introduce an experimentally accessible ensemble-averaged local density correlation function and study its behavior as a function of confining slit width. Upon increasing the distance between the confining surfaces, we observe an alternating sequence of strongly anisotropic versus more isotropic local order. The latter is due to packing frustration of the spherical particles. This observation highlights the importance of studying inhomogeneous fluids at the pair-distribution level.
Stokes shift dynamics of ionic liquids: Solute probe dependence, and effects of self-motion, dielectric relaxation frequency window, and collective intermolecular solvent modes
Authors: Daschakraborty Snehasis , Pal Tamisra , Biswas Ranjit
Published: October 2013

In this paper we have used a semi-molecular theory for investigating the probe dependence of Stokes shift dynamics in room temperature ionic liquids (ILs) by considering three different but well-known dipolar solvation probes—coumarin 153, trans-4-dimethylamino-4′-cyanostilbene, and 4-aminophthalimide. In addition, effects on polar solvation energy relaxation in ILs of solute motion, frequency coverage (frequency window) accessed by dielectric relaxation measurements and collective IL intermolecular modes (CIMs) at tera-hertz range have been explored. Eleven different ILs have been considered for the above theoretical study. Calculated results show better agreement with the recent (fluorescence up-conversion (FLUPS) + time-correlated single photon counting (TCSPC)) experimental results, particularly at short times, when the CIM contribution to the frequency dependent dielectric function (ɛ(ω)) is included. This is done via assigning the missing dispersion in an experimental ɛ(ω) to an IL intermolecular mode at 30 cm−1. No significant probe dependence has been observed for solvation energy relaxation although the magnitude of dynamic Stokes shift varies with the dipole moment of the excited solute. Calculations using experimental ɛ(ω) measured with broader frequency window generate solvation response functions closer to experiments. However, average solvation rates predicted by using different ɛ(ω) for the same IL do not differ appreciably, implying over-all validity of these dielectric relaxation measurements. Results presented here indicate that inclusion of solvent molecularity via wavenumber dependent static correlations and ion dynamic structure factor relaxation improves significantly the comparison between theory and experiments over the continuum model predictions for polar solvation dynamics in these solvents.
Sub-Ohmic spin-boson model with off-diagonal coupling: Ground state properties
Authors: Lü Zhiguo , Duan Liwei , Li Xin , Shenai Prathamesh M. , Zhao Yang
Published: October 2013

We have carried out analytical and numerical studies of the spin-boson model in the sub-ohmic regime with the influence of both the diagonal and the off-diagonal coupling accounted for, via the Davydov D1 variational ansatz. While a second-order phase transition is known to be exhibited by this model in the presence of diagonal coupling only, we demonstrate the emergence of a discontinuous first order phase transition upon incorporation of the off-diagonal coupling. A plot of the ground state energy versus magnetization highlights the discontinuous nature of the transition between the isotropic (zero magnetization) state and nematic (finite magnetization) phases. We have also calculated the entanglement entropy and a discontinuity found at a critical coupling strength further supports the discontinuous crossover in the spin-boson model in the presence of off-diagonal coupling. It is further revealed via a canonical transformation approach that for the special case of identical exponents for the spectral densities of the diagonal and the off-diagonal coupling, there exists a continuous crossover from a single localized phase to doubly degenerate localized phase with differing magnetizations.
Mechanisms of H2O desorption from amorphous solid water by 157-nm irradiation: An experimental and theoretical study
Authors: DeSimone Alice J. , Crowell Vernon D. , Sherrill C. David , Orlando Thomas M.
Published: October 2013

The photodesorption of water molecules from amorphous solid water (ASW) by 157-nm irradiation has been examined using resonance-enhanced multiphoton ionization. The rotational temperature has been determined, by comparison with simulations, to be 425 ± 75 K. The time-of-flight spectrum of H2O (v = 0) has been fit with a Maxwell-Boltzmann distribution with a translational temperature of 700 ± 200 K (0.12 ± 0.03 eV). H+ and OH+ fragment ions have been detected with non-resonant multiphoton ionization, indicating vibrationally excited parent water molecules with translational energies of 0.24 ± 0.08 eV. The cross section for water removal from ASW by 7.9-eV photons near 100 K is (6.9 ± 1.8) × 10−20 cm2 for >10 L H2O exposure. Electronic structure computations have also probed the excited states of water and the mechanisms of desorption. Calculated electron attachment and detachment densities show that exciton delocalization leads to a dipole reversal state in the first singlet excited state of a model system of hexagonal water ice. Ab Initio Molecular Dynamics simulations show possible desorption of a photo-excited water molecule from this cluster, though the non-hydrogen bonded OH bond is stretched significantly before desorption. Potential energy curves of this OH stretch in the electronic excited state show a barrier to dissociation, lending credence to the dipole reversal mechanism.
An integrated experimental and quantum-chemical investigation on the vibrational spectra of chlorofluoromethane
Authors: Charmet Andrea Pietropolli , Stoppa Paolo , Tasinato Nicola , Giorgianni Santi , Barone Vincenzo , Biczysko Malgorzata , Bloino Julien , Cappelli Chiara , Carnimeo Ivan , Puzzarini Cristina
Published: October 2013

The vibrational analysis of the gas-phase infrared spectra of chlorofluoromethane (CH2ClF, HCFC-31) was carried out in the range 200–6200 cm−1. The assignment of the absorption features in terms of fundamental, overtone, combination, and hot bands was performed on the medium-resolution (up to 0.2 cm−1) Fourier transform infrared spectra. From the absorption cross section spectra accurate values of the integrated band intensities were derived and the global warming potential of this compound was estimated, thus obtaining values of 323, 83, and 42 on a 20-, 100-, and 500-year horizon, respectively. The set of spectroscopic parameters here presented provides the basic data to model the atmospheric behavior of this greenhouse gas. In addition, the obtained vibrational properties were used to benchmark the predictions of state-of-the-art quantum-chemical computational strategies. Extrapolated complete basis set limit values for the equilibrium geometry and harmonic force field were obtained at the coupled-cluster singles and doubles level of theory augmented by a perturbative treatment of triple excitations, CCSD(T), in conjunction with a hierarchical series of correlation-consistent basis sets (cc-pVnZ, with n = T, Q, and 5), taking also into account the core-valence correlation effects and the corrections due to diffuse (aug) functions. To obtain the cubic and quartic semi-diagonal force constants, calculations employing second-order Møller-Plesset perturbation (MP2) theory, the double-hybrid density functional B2PLYP as well as CCSD(T) were performed. For all anharmonic force fields the performances of two different perturbative approaches in computing the vibrational energy levels (i.e., the generalized second order vibrational treatment, GVPT2, and the recently proposed hybrid degeneracy corrected model, HDCPT2) were evaluated and the obtained results allowed us to validate the spectroscopic predictions yielded by the HDCPT2 approach. The predictions of the deperturbed second-order perturbation approach, DVPT2, applied to the computation of infrared intensities beyond the double-harmonic approximation were compared to the accurate experimental values here determined. Anharmonic DFT and MP2 corrections to CCSD(T) intensities led to a very good agreement with the absorption cross section measurements over the whole spectral range here analysed.
Superconducting magnets for the RAON electron cyclotron resonance ion source
Authors: Choi S. , Kim Y. , Hong I. S. , Jeon D.
Published: October 2013

The RAON linear accelerator of Rare Isotope Science Project has been developed since 2011, and the superconducting magnet for ECRIS was designed. The RAON ECR ion source was considered as a 3rd generation source. The fully superconducting magnet has been designed for operating using 28 GHz radio frequency. The RAON ECRIS operates in a minimum B field configuration which means that a magnetic sextupole field for radial confinement is superimposed with a magnetic mirror field for axial confinement. The highest field strength reaches 3.5 T on axis and 2 T at the plasma chamber wall for operating frequency up to 28 GHz. In this paper, the design results are presented of optimized superconducting magnet consisting of four solenoids and sextupole. The prototype magnet for ECRIS was fabricated and tested to verify the feasibility of the design. On the basis of test results, a fully superconducting magnet will be fabricated and tested.
Unsteady pressure-sensitive paint measurement based on the heterodyne method using low frame rate camera
Authors: Matsuda Yu , Yorita Daisuke , Egami Yasuhiro , Kameya Tomohiro , Kakihara Noriaki , Yamaguchi Hiroki , Asai Keisuke , Niimi Tomohide
Published: October 2013

The pressure-sensitive paint technique based on the heterodyne method was proposed for the precise pressure measurement of unsteady flow fields. This measurement is realized by detecting the beat signal that results from interference between a modulating illumination light source and a pressure fluctuation. The beat signal is captured by a camera with a considerably lower frame rate than the frequency of the pressure fluctuation. By carefully adjusting the frequency of the light and the camera frame rate, the signal at the frequency of interest is detected, while the noise signals at other frequencies are eliminated. To demonstrate the proposed method, we measured the pressure fluctuations in a resonance tube at the fundamental, second, and third harmonics. The pressure fluctuation distributions were successfully obtained and were consistent with measurements from a pressure transducer. The proposed method is a useful technique for measuring unsteady phenomena.
Thermopower in quantum confined La-doped SrTiO3 epitaxial heterostructures
Authors: Kerman K. , Ramanathan S. , Baniecki J. D. , Ishii M. , Kotaka Y. , Aso H. , Kurihara K. , Schafranek R. , Vailionis A.
Published: October 2013

We characterize effects of dimensionality reduction and electron confinement on thermopower in La-doped SrTiO3 (LSTO) thin films using hetero-epitaxial capping layers with known conduction band offsets. Hall measurements on SrZrO3/LSTO/(La0.3Sr0.7)(Al0.65Ta0.35)O3 quantum well structures indicate carriers are homogeneously confined in the LSTO film, leading to an unambiguous well width. We do not observe a substantial enhancement of the Seebeck coefficient (S) for confinement widths as thin as 8 Å. Recent work towards elucidating the role of thickness scaling on S in complex oxides and implications of our results for using 2D electron confinement to develop advanced thermoelectric materials are discussed.
Energy decay result in a Timoshenko-type system of thermoelasticity of type III with distributive delay
Authors: Kafini Mohammad , Messaoudi Salim A. , Mustafa Muhammad I.
Published: October 2013

In this paper, we consider a one-dimensional linear thermoelastic system of Timoshenko type with distributive delay, where the heat conduction is given by Green and Naghdi theories. We establish the stability of the system for the case of equal and nonequal speeds of wave propagation.
Wide frequencies range of spin excitations in a rare-earth Bi-doped iron garnet with a giant Faraday rotation
Authors: Parchenko Sergii , Stupakiewicz Andrzej , Yoshimine Isao , Satoh Takuya , Maziewski Andrzej
Published: October 2013

Ultrafast magnetization dynamics of a rare-earth Bi-doped garnet were studied using an optical pump–probe technique via the inverse Faraday effect. We observed a wide range of frequency modes of the magnetization precession, covering two orders of magnitude. The excitation efficiency of low-frequency precessions in the GHz range, together with a significant beating effect, strongly depended on the amplitude of the external magnetic field. On the contrary, high-frequency precession was independent of the external magnetic field. The obtained results may be exploited in the development of wide class of microwave and magneto-optical devices.
A quantum molecular dynamics study of aqueous solvation dynamics
Authors: Videla Pablo E. , Rossky Peter J. , Laria D.
Published: October 2013

Ring polymer molecular dynamics experiments have been carried out to examine effects derived from nuclear quantum fluctuations at ambient conditions on equilibrium and non-equilibrium dynamical characteristics of charge solvation by a popular simple, rigid, water model, SPC/E , and for a more recent, and flexible, q-TIP4P/F model, to examine the generality of conclusions. In particular, we have recorded the relaxation of the solvent energy gap following instantaneous, ±e charge jumps in an initially uncharged Lennard-Jones-like solute. In both charge cases, quantum effects are reflected in sharper decays at the initial stages of the relaxation, which produce up to a ∼20% reduction in the characteristic timescales describing the solvation processes. For anionic solvation, the magnitude of polarization fluctuations controlling the extent of the water proton localization in the first solvation shell is somewhat more marked than for cations, bringing the quantum solvation process closer to the classical case. Effects on the solvation response from the explicit incorporation of flexibility in the water Hamiltonian are also examined. Predictions from linear response theories for the overall relaxation profile and for the corresponding characteristic timescales are reasonably accurate for the solvation of cations, whereas we find that they are much less satisfactory for the anionic case.
The effect of passivation on different GaAs surfaces
Authors: Yu Ted H. , Yan Liang , You Wei , Laghumavarapu Ramesh B. , Huffaker Diana , Ratsch Christian
Published: October 2013

The surface passivation of semiconductors on different surface orientations results in vastly disparate effects. Experiments of GaAs/poly(3,4-ethylenedioxythiophene/indium tin oxide solar cells show that sulfur passivation results in threefold conversion efficiency improvements for the GaAs (100) surface. In contrast, no improvements are observed after passivation of the GaAs (111B) surface, which achieves 4% conversion efficiency. This is explained by density-functional theory calculations, which find a surprisingly stable (100) surface reconstruction with As defects that contains midgap surface states. Band structure calculations with hybrid functionals of the defect surface show a surface state on the undimerized As atoms and its disappearance after passivation.
Interstitial-boron solution strengthened WB3+x
Authors: Cheng Xiyue , Zhang Wei , Chen Xing-Qiu , Niu Haiyang , Liu Peitao , Du Kui , Liu Gang , Li Dianzhong , Cheng Hui-Ming , Ye Hengqiang , Li Yiyi
Published: October 2013

By means of variable-composition evolutionary algorithm coupled with density functional theory and in combination with aberration-corrected high-resolution transmission electron microscopy experiments, we have studied and characterized the composition, structure, and hardness properties of WB3+x (x < 0.5). We provide robust evidence for the occurrence of stoichiometric WB3 and non-stoichiometric WB3+x, both crystallizing in the metastable hP16 (P63/mmc) structure. No signs for the formation of the highly debated WB4 (both hP20 and hP10) phases were found. Our results rationalize the seemingly contradictory high-pressure experimental findings and suggest that the interstitial boron atom is located in the tungsten layer and vertically interconnect with four boron atoms, thus forming a typical three-center boron net with the upper and lower boron layers in a three-dimensional covalent network, which thereby strengthen the hardness.
Engineering domain structures in nanoscale magnetic thin films via strain
Authors: Hu Jia-Mian , Yang T. N. , Chen L. Q. , Nan C. W.
Published: October 2013

We study the strain effects on magnetic domain stability and dynamics in nanoscale magnetic thin films using phase-field simulations. Numerous strain-stabilized single-/multi-domain states are discovered, including various magnetic vortices with circular in-plane domains. Furthermore, a strain-domain stability map was constructed, displaying the stable magnetic domain and domain wall structures as a function of biaxial isotropic and anisotropic in-plane strains at room temperature. The present work provides useful guidelines for a precise engineering and experimental observation of domain structures in nanoscale magnetic thin films and a promising scheme towards a low-power and local control over magnetic domain structures.
Analysis of 140 gigahertz folded frame travelling wave tube
Authors: Guo Guo , Wei Yanyu , Zhang Minghao , Travish Gil , Yue Lingna , Xu Jin , Yin Hairong , Huang Minzhi , Gong Yubin , Wang Wenxiang
Published: October 2013

A study on the low voltage, high efficiency and wide bandwidth travelling wave tube by using a novel folded frame slow-wave structure is carried out in this paper. The radio frequency characteristics of the folded frame structure, including dispersion property, interaction impedances, and reflection property are investigated and compared to the similar symmetric double V-shape meander-line structure. Then, the beam-wave interaction process of the folded frame travelling wave tube (TWT) with rectangular sheet electron beam is simulated by 3-D particle-in-cell algorithms. The results show that the output power and electron efficiency can reach 259 W and 13.5% at the center frequency of 140 GHz, respectively. Simultaneously, the instantaneous 3-dB bandwidth is 24 GHz. Compared to the symmetric double V-shaped TWT, the output power and electron efficiency of the folded frame TWT are increased.