bluuebunny/crossref_metadata_2025 huggingface dataset:
Successful Treatment of Athletic Pubalgia in a Lacrosse Player with Ultrasound‐Guided Needle Tenotomy and Platelet‐Rich Plasma Injection: A Case Report
Authors: Scholten Paul M. , Massimi Stephen , Dahmen Nick , Diamond Joanne , Wyss James
Published: August 2014

Athletic pubalgia is a syndrome of persistent groin pain due to chronic repetitive trauma or stress involving the pelvic joints and many musculotendinous structures that cross the anterior pelvis. As a result, the differential diagnosis can be complex, but insertional tendinopathies are the most common. This case report describes a novel approach to the treatment of distal rectus abdominis tendinopathies with ultrasound‐guided needle tenotomy and platelet‐rich plasma (PRP) injection. After injection, the patient returned to pain‐free play at his previous level of intensity. This suggests that PRP may be a useful treatment for this diagnosis.
Use of an Ankle‐Foot Orthosis Improves Aerobic Capacity in Subacute Hemiparetic Stroke Patients
Authors: Hyun Chul Woong , Kim Bo Ryun , Han Eun Young , Kim Sun Mi
Published: August 2014

Objective

To investigate aerobic capacity with and without an ankle‐foot orthosis (AFO) in subacute hemiparetic stroke patients.

Design

Prospective crossover intervention study.

Setting

Rehabilitation clinic in secondary care.

Patients

Patients diagnosed with first‐ever cerebral stroke involving the cortical or subcortical area resulting in hemiparesis (n = 15, 8 men and 7 women; average age, 62.1 years).

Methods

All subjects participated in 2 continuous, symptom‐limited, low‐velocity graded treadmill exercise stress tests under 2 different conditions, namely, with and without an AFO. The rest interval between tests was at least 48 hours. The order of exercise stress tests was randomized.

Main Outcome Measurements

To assess cardiorespiratory responses, oxygen consumption, heart rate, systolic blood pressure, diastolic blood pressure, rate‐pressure product, and respiratory exchange ratio were measured continuously throughout the test, and peak values were obtained. The rating of perceived exertion was recorded immediately after each test. The percentage of the age‐predicted maximal heart rate and total exercise duration were also measured. Gait function was assessed by the Six‐Minute Walk Test.

Results

Using an AFO significantly increased peak oxygen consumption and Six‐Minute Walk Test results. Peak values of each of heart rate, systolic blood pressure, diastolic blood pressure, rate‐pressure product, and respiratory exchange ratio, rating of perceived exertion, percentage of age‐predicted maximal heart rate, and total exercise duration were similar regardless of AFO use.

Conclusions

Use of an AFO may improve aerobic capacity in subacute hemiparetic stroke patients, and may improve energy efficiency and gait endurance.
Does non‐interest income make banks more risky? Retail‐ versus investment‐oriented banks
Authors: Köhler Matthias
Published: August 2014

In this paper, we show that the impact of non‐interest income on bank risk differs between retail‐ and investment‐oriented banks. More specifically, while retail‐oriented banks such as savings, cooperative and other banks that focus on lending and deposit‐taking services become significantly more stable (in the sense of having a higher Z‐score) if they increase their share of non‐interest income, investment‐oriented banks become significantly more risky. They do not only generate a higher share of their income from non‐traditional activities, but also engage in significantly different activities from retail‐oriented banks. This might limit the potential benefits to investment‐oriented banks of diversifying into non‐interest income. Overall, therefore, our paper implies that it is important to distinguish between retail‐ and investment‐oriented banks when drawing general conclusions regarding the impact of non‐interest income on bank risk.
Many roads lead to Rome? Multiple modes of Cu,Zn superoxide dismutase destabilization, misfolding and aggregation in amyotrophic lateral sclerosis
Authors: Broom Helen R. , Rumfeldt Jessica A.O. , Meiering Elizabeth M.
Published: August 2014

ALS (amyotrophic lateral sclerosis) is a fatal neurodegenerative syndrome characterized by progressive paralysis and motor neuron death. Although the pathological mechanisms that cause ALS remain unclear, accumulating evidence supports that ALS is a protein misfolding disorder. Mutations in Cu,Zn-SOD1 (copper/zinc superoxide dismutase 1) are a common cause of familial ALS. They have complex effects on different forms of SOD1, but generally destabilize the protein and enhance various modes of misfolding and aggregation. In addition, there is some evidence that destabilized covalently modified wild-type SOD1 may be involved in disease. Among the multitude of misfolded/aggregated species observed for SOD1, multiple species may impair various cellular components at different disease stages. Newly developed antibodies that recognize different structural features of SOD1 represent a powerful tool for further unravelling the roles of different SOD1 structures in disease. Evidence for similar cellular targets of misfolded/aggregated proteins, loss of cellular proteostasis and cell–cell transmission of aggregates point to common pathological mechanisms between ALS and other misfolding diseases, such as Alzheimer's, Parkinson's and prion diseases, as well as serpinopathies. The recent progress in understanding the molecular basis for these devastating diseases provides numerous avenues for developing urgently needed therapeutics.
Plasmonic formation mechanism of periodic 100-nm-structures upon femtosecond laser irradiation of silicon in water
Authors: Derrien T. J.-Y. , Koter R. , Krüger J. , Höhm S. , Rosenfeld A. , Bonse J.
Published: August 2014

The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of silicon by multiple (N = 100) linearly polarized Ti:sapphire femtosecond laser pulses (duration τ = 30 fs, center wavelength λ0 ∼ 790 nm) is studied experimentally in air and water environment. The LIPSS surface morphologies are characterized by scanning electron microscopy and their spatial periods are quantified by two-dimensional Fourier analyses. It is demonstrated that the irradiation environment significantly influences the periodicity of the LIPSS. In air, so-called low-spatial frequency LIPSS (LSFL) were found with periods somewhat smaller than the laser wavelength (ΛLSFL ∼ 0.7 × λ0) and an orientation perpendicular to the laser polarization. In contrast, for laser processing in water a reduced ablation threshold and LIPSS with approximately five times smaller periods ΛLIPSS ∼ 0.15 × λ0 were observed in the same direction as in air. The results are discussed within the frame of recent LIPSS theories and complemented by a thin film based surface plasmon polariton model, which successfully describes the tremendously reduced LIPSS periods in water.
Microjetting from a grooved Al surface under supported and unsupported shocks
Authors: Shao Jian-Li , Wang Pei , He An-Min
Published: August 2014

Using molecular dynamics methods, we simulate and compare the microjetting from a grooved Al surface induced by supported and unsupported shocks at different breakout pressures. Via the analysis on the microjetting morphologies and mass distributions, we find that the threshold of shock breakout pressure for the microjetting formation is almost same, but the variation of microjet mass with shock pressure shows a great difference for the two loading patterns. Under supported shock loading, the microjet mass keeps a continuous increase with increasing shock pressure, and release melting can enhance it markedly. By contrast, the microjet mass under unsupported shocks is smaller and seems no remarkable increase with shock pressure in our simulations (at extremely short pulses), implying the shock decaying can weaken the microjetting. Of course, a large area of fragments near the surface may form in this case. The microjet source distributions corresponding to supported and unsupported shocks are presented. It is found that the former becomes apparently broader than the latter with increasing shock pressure. Besides, the microjet tip velocity under supported shocks may appear a reduction because of the material strength effect below release melting. While under unsupported shocks, all the microjets in solid and melted states will experience the reduction of tip velocity. These decrements of tip velocity can be fitted by an exponential function.
Autocorrelation study of the Θ transition for a coarse-grained polymer model
Authors: Qi Kai , Bachmann Michael
Published: August 2014

By means of Metropolis Monte Carlo simulations of a coarse-grained model for flexible polymers, we investigate how the integrated autocorrelation times of different energetic and structural quantities depend on the temperature. We show that, due to critical slowing down, an extremal autocorrelation time can also be considered as an indicator for the collapse transition that helps to locate the transition point. This is particularly useful for finite systems, where response quantities such as the specific heat do not necessarily exhibit clear indications for pronounced thermal activity.
The ReactorSTM: Atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions
Authors: Herbschleb C. T. , van der Tuijn P. C. , Roobol S. B. , Navarro V. , Bakker J. W. , Liu Q. , Stoltz D. , Cañas-Ventura M. E. , Verdoes G. , van Spronsen M. A. , Bergman M. , Crama L. , Taminiau I. , Ofitserov A. , van Baarle G. J. C. , Frenken J. W. M.
Published: August 2014

To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions.
Potential of mean force analysis of the self-association of leucine-rich transmembrane α-helices: Difference between atomistic and coarse-grained simulations
Authors: Nishizawa Manami , Nishizawa Kazuhisa
Published: August 2014

Interaction of transmembrane (TM) proteins is important in many biological processes. Large-scale computational studies using coarse-grained (CG) simulations are becoming popular. However, most CG model parameters have not fully been calibrated with respect to lateral interactions of TM peptide segments. Here, we compare the potential of mean forces (PMFs) of dimerization of TM helices obtained using a MARTINI CG model and an atomistic (AT) Berger lipids-OPLS/AA model (ATOPLS). For helical, tryptophan-flanked, leucine-rich peptides (WL15 and WALP15) embedded in a parallel configuration in an octane slab, the ATOPLS PMF profiles showed a shallow minimum (with a depth of approximately 3 kJ/mol; i.e., a weak tendency to dimerize). A similar analysis using the CHARMM36 all-atom model (ATCHARMM) showed comparable results. In contrast, the CG analysis generally showed steep PMF curves with depths of approximately 16–22 kJ/mol, suggesting a stronger tendency to dimerize compared to the AT model. This CG > AT discrepancy in the propensity for dimerization was also seen for dilauroylphosphatidylcholine (DLPC)-embedded peptides. For a WL15 (and WALP15)/DLPC bilayer system, ATOPLS PMF showed a repulsive mean force for a wide range of interhelical distances, in contrast to the attractive forces observed in the octane system. The change from the octane slab to the DLPC bilayer also mitigated the dimerization propensity in the CG system. The dimerization energies of CG (AALALAA)3 peptides in DLPC and dioleoylphosphatidylcholine bilayers were in good agreement with previous experimental data. The lipid headgroup, but not the length of the lipid tails, was a key causative factor contributing to the differences between octane and DLPC. Furthermore, the CG model, but not the AT model, showed high sensitivity to changes in amino acid residues located near the lipid-water interface and hydrophobic mismatch between the peptides and membrane. These findings may help interpret CG and AT simulation results on membrane proteins.
Equation of motion coupled cluster methods for electron attachment and ionization potential in fullerenes C60 and C70
Authors: Bhaskaran-Nair Kiran , Kowalski Karol , Moreno Juana , Jarrell Mark , Shelton William A.
Published: August 2014

In both molecular and periodic solid-state systems there is a need for the accurate determination of the ionization potential and the electron affinity for systems ranging from light harvesting polymers and photocatalytic compounds to semiconductors. The development of a Green's function approach based on the coupled cluster (CC) formalism would be a valuable tool for addressing many properties involving many-body interactions along with their associated correlation functions. As a first step in this direction, we have developed an accurate and parallel efficient approach based on the equation of motion-CC technique. To demonstrate the high degree of accuracy and numerical efficiency of our approach we calculate the ionization potential and electron affinity for C60 and C70. Accurate predictions for these molecules are well beyond traditional molecular scale studies. We compare our results with experiments and both quantum Monte Carlo and GW calculations.
Topos models for physics and topos theory
Authors: Wolters Sander
Published: August 2014

What is the role of topos theory in the topos models for quantum theory as used by Isham, Butterfield, Döring, Heunen, Landsman, Spitters, and others? In other words, what is the interplay between physical motivation for the models and the mathematical framework used in these models? Concretely, we show that the presheaf topos model of Butterfield, Isham, and Döring resembles classical physics when viewed from the internal language of the presheaf topos, similar to the copresheaf topos model of Heunen, Landsman, and Spitters. Both the presheaf and copresheaf models provide a “quantum logic” in the form of a complete Heyting algebra. Although these algebras are natural from a topos theoretic stance, we seek a physical interpretation for the logical operations. Finally, we investigate dynamics. In particular, we describe how an automorphism on the operator algebra induces a homeomorphism (or isomorphism of locales) on the associated state spaces of the topos models, and how elementary propositions and truth values transform under the action of this homeomorphism. Also with dynamics the focus is on the internal perspective of the topos.
Velocity-changing collisions in pure H2 and H2-Ar mixture
Authors: Wcisło P. , Tran H. , Kassi S. , Campargue A. , Thibault F. , Ciuryło R.
Published: August 2014

We show how to effectively introduce a proper description of the velocity-changing collisions into the model of isolated molecular transition for the case of self- and Ar-perturbed H2. We demonstrate that the billiard-ball (BB) approximation of the H2-H2 and H2-Ar potentials gives an accurate description of the velocity-changing collisions. The BB model results are compared with ab initio classical molecular dynamics simulations. It is shown that the BB model correctly reproduces not only the principal properties such as frequencies of velocity-changing collisions or collision kernels, but also other characteristics of H2-H2 and H2-Ar gas kinetics like rate of speed-changing collisions. Finally, we present line-shape measurement of the Q(1) line of the first overtone band of self-perturbed H2. We quantify the systematic errors of line-shape analysis caused by the use of oversimplified description of velocity-changing collisions. These conclusions will have significant impact on recent rapidly developing ultra-accurate metrology based on Doppler-limited spectroscopic measurements such as Doppler-width thermometry, atmosphere monitoring, Boltzmann constant determination, or transition position and intensity determination for fundamental studies.
Generalized metaplectic operators and the Schrödinger equation with a potential in the Sjöstrand class
Authors: Cordero Elena , Gröchenig Karlheinz , Nicola Fabio , Rodino Luigi
Published: August 2014

It is well known that the matrix of a metaplectic operator with respect to phase-space shifts is concentrated along the graph of a linear symplectic map. We show that the algebra generated by metaplectic operators and by pseudodifferential operators in a Sjöstrand class enjoys the same decay properties. We study the behavior of these generalized metaplectic operators and represent them by Fourier integral operators. Our main result shows that the one-parameter group generated by a Hamiltonian operator with a potential in the Sjöstrand class consists of generalized metaplectic operators. As a consequence, the Schrödinger equation preserves the phase-space concentration, as measured by modulation space norms.
Sub-harmonic resonant wave interactions in the presence of a linear interfacial instability
Authors: Campbell Bryce K. , Liu Yuming
Published: August 2014

This work considers the role of nonlinear sub-harmonic resonant wave interactions in the development of interfacial waves, which may be under the influence of a linear interfacial instability, in an inviscid two-fluid stratified flow through a horizontal channel. We begin by examining the case of resonant interactions between one linearly unstable mode and its sub-harmonic that may be linearly stable or unstable. Using the method of multiple scales, we derive the nonlinear interaction equations governing the time evolution of interacting wave amplitudes. These nonlinear equations account for the combined effects of both the nonlinear resonant interaction and the linear instability. We show that through this nonlinear coupling, the linearly stable sub-harmonic mode can achieve faster than exponential growth. It is found that such a mechanism is capable of generating large-amplitude long waves that are stable by linear stability analysis. The analytical predictions are cross validated by comparisons with direct nonlinear numerical simulations based on a more general perturbation based spectral method. Good agreement between the analytical and numerical solutions is observed. The more complicated case where a single mode is simultaneously involved in multiple (sub-harmonic and triad) resonances is also investigated numerically. The results demonstrate that chains of resonances can permit the energy generated by the linear instability, among high wavenumber components, to be passed across the spectrum to the longest wave components creating an efficient mechanism for the generation of large-amplitude long waves from unstable short waves.
Design and construction of an Offner spectrometer based on geometrical analysis of ring fields
Authors: Kim Seo Hyun , Kong Hong Jin , Lee Jong Ung , Lee Jun Ho , Lee Jai Hoon
Published: August 2014

A method to obtain an aberration-corrected Offner spectrometer without ray obstruction is proposed. A new, more efficient spectrometer optics design is suggested in order to increase its spectral resolution. The derivation of a new ring equation to eliminate ray obstruction is based on geometrical analysis of the ring fields for various numerical apertures. The analytical design applying this equation was demonstrated using the optical design software Code V in order to manufacture a spectrometer working in wavelengths of 900–1700 nm. The simulation results show that the new concept offers an analytical initial design taking the least time of calculation. The simulated spectrometer exhibited a modulation transfer function over 80% at Nyquist frequency, root-mean-square spot diameters under 8.6 μm, and a spectral resolution of 3.2 nm. The final design and its realization of a high resolution Offner spectrometer was demonstrated based on the simulation result. The equation and analytical design procedure shown here can be applied to most Offner systems regardless of the wavelength range.
Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers
Authors: Leger Joel D. , Nyby Clara M. , Varner Clyde , Tang Jianan , Rubtsova Natalia I. , Yue Yuankai , Kireev Victor V. , Burtsev Viacheslav D. , Qasim Layla N. , Rubtsov Grigory I. , Rubtsov Igor V.
Published: August 2014

A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm−1 to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ∼70 as. The anharmonicity of smaller than 10−4 cm−1 was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 μrad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy.
Band alignment of InN/6H-SiC heterojunction determined by x-ray photoelectron spectroscopy
Authors: Jing Qiang , Wu Guoguang , Zhang Yuantao , Gao Fubin , Cai Xupu , Zhao Yang , Li Wancheng , Du Guotong
Published: August 2014

The valence band offset (VBO) of InN/6H-SiC heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be −0.10 ± 0.23 eV and the conduction band offset is deduced to be −2.47 ± 0.23 eV, indicating that the heterojunction has a type-II band alignment. The accurate determination of the valence and conduction band offsets is important for applications and analysis of InN/6H-SiC optoelectronic devices.
UV absorption spectrum of the C2 Criegee intermediate CH3CHOO
Authors: Smith Mica C. , Ting Wei-Lun , Chang Chun-Hung , Takahashi Kaito , Boering Kristie A. , Lin Jim Jr-Min
Published: August 2014

The UV spectrum of CH3CHOO was measured by transient absorption in a flow cell at 295 K. The absolute absorption cross sections of CH3CHOO were measured by laser depletion in a molecular beam to be (1.06 ± 0.09) × 10−17 cm2 molecule−1 at 308 nm and (9.7 ± 0.6) × 10−18 cm2 molecule−1 at 352 nm. After scaling the UV spectrum of CH3CHOO to the absolute cross section at 308 nm, the peak UV cross section is (1.27 ± 0.11) × 10−17 cm2 molecule−1 at 328 nm. Compared to the simplest Criegee intermediate CH2OO, the UV absorption band of CH3CHOO is similar in intensity but blue shifted by 14 nm, resulting in a 20% slower photolysis rate estimated for CH3CHOO in the atmosphere.
Effect of cation species on surface-induced phase transition observed for platinum complex anions in platinum electrodeposition using nanoporous silicon
Authors: Koda Ryo , Koyama Akira , Fukami Kazuhiro , Nishi Naoya , Sakka Tetsuo , Abe Takeshi , Kitada Atsushi , Murase Kuniaki , Kinoshita Masahiro
Published: August 2014

In an earlier work [K. Fukami et al., J. Chem. Phys. 138, 094702 (2013)], we reported a transition phenomenon observed for platinum complex anions in our platinum electrodeposition experiment using nanoporous silicon. The pore wall surface of the silicon electrode was made hydrophobic by covering it with organic molecules. The anions are only weakly hydrated due to their large size and excluded from the bulk aqueous solution to the hydrophobic surface. When the anion concentration in the bulk was gradually increased, at a threshold the deposition behavior exhibited a sudden change, leading to drastic acceleration of the electrochemical deposition. It was shown that this change originates from a surface-induced phase transition: The space within a nanopore is abruptly filled with the second phase in which the anion concentration is orders of magnitude higher than that in the bulk. Here we examine how the platinum electrodeposition behavior is affected by the cation species coexisting with the anions. We compare the experimental results obtained using three different cation species: K+, (CH3)4N+, and (C2H5)4N+. One of the cation species coexists with platinum complex anions [PtCl4]2−. It is shown that the threshold concentration, beyond which the electrochemical deposition within nanopores is drastically accelerated, is considerably dependent on the cation species. The threshold concentration becomes lower as the cation size increases. Our theoretical analysis suggests that not only the anions but also the cations are remarkably enriched in the second phase. The remarkable enrichment of the anions alone would give rise to the energetic instability due to electrostatic repulsive interactions among the anions. We argue that the result obtained cannot be elucidated by the prevailing view based on classical electrochemistry. It is necessitated to consult a statistical-mechanical theory of confined aqueous solutions using a molecular model for water.
Rotationally adiabatic pair interactions of para- and ortho-hydrogen with the halogen molecules F2, Cl2, and Br2
Authors: Berg Matthias , Accardi Antonio , Paulus Beate , Schmidt Burkhard
Published: August 2014

The present work is concerned with the weak interactions between hydrogen and halogen molecules, i.e., the interactions of pairs H2–X2 with X = F, Cl, Br, which are dominated by dispersion and quadrupole-quadrupole forces. The global minimum of the four-dimensional (4D) coupled cluster with singles and doubles and perturbative triples (CCSD(T)) pair potentials is always a T shaped structure where H2 acts as the hat of the T, with well depths (De) of 1.3, 2.4, and 3.1 kJ/mol for F2, Cl2, and Br2, respectively. MP2/AVQZ results, in reasonable agreement with CCSD(T) results extrapolated to the basis set limit, are used for detailed scans of the potentials. Due to the large difference in the rotational constants of the monomers, in the adiabatic approximation, one can solve the rotational Schrödinger equation for H2 in the potential of the X2 molecule. This yields effective two-dimensional rotationally adiabatic potential energy surfaces where pH2 and oH2 are point-like particles. These potentials for the H2–X2 complexes have global and local minima for effective linear and T-shaped complexes, respectively, which are separated by 0.4-1.0 kJ/mol, where oH2 binds stronger than pH2 to X2, due to higher alignment to minima structures of the 4D-pair potential. Further, we provide fits of an analytical function to the rotationally adiabatic potentials.
Surface stress variation as a function of applied compressive stress and temperature in microscale silicon
Authors: Gan Ming , Tomar Vikas
Published: August 2014

Surface stress has been shown to affect the mechanical properties of materials at or below the microscale. Surface-stress-induced dislocation activity at such length scales has been shown to be a major factor affecting the mechanical behavior of materials. Defect generation as a function of applied stress at the microscale has previously been measured experimentally and predicted using simulations. However, the change in surface stress in a material in response to externally applied stress as a function of temperature has not been explored experimentally. Such an investigation is presented in this work for the case of microscale silicon samples. In-situ nondestructive measurements of the applied compressive stress and the corresponding microscale surface stress were performed from room temperature to 100 °C. The applied stress was controlled by a nanomechanical loading system. Micro-Raman spectroscopy was used to measure the surface stress in-situ as the samples deformed under the applied uniaxial compressive stress. The surface stress was found to be lower than the applied stress at all temperatures. The difference between the surface stress and the applied stress became higher at higher temperatures indicating that surface relaxation was induced by the temperature increase. Based on the measured values and observed trends, an exponential Gaussian function is proposed to describe the stress as a function of surface depth.
Improving the efficiency of configurational-bias Monte Carlo: A density-guided method for generating bending angle trials for linear and branched molecules
Authors: Sepehri Aliasghar , Loeffler Troy D. , Chen Bin
Published: August 2014

A new method has been developed to generate bending angle trials to improve the acceptance rate and the speed of configurational-bias Monte Carlo. Whereas traditionally the trial geometries are generated from a uniform distribution, in this method we attempt to use the exact probability density function so that each geometry generated is likely to be accepted. In actual practice, due to the complexity of this probability density function, a numerical representation of this distribution function would be required. This numerical table can be generated a priori from the distribution function. This method has been tested on a united-atom model of alkanes including propane, 2-methylpropane, and 2,2-dimethylpropane, that are good representatives of both linear and branched molecules. It has been shown from these test cases that reasonable approximations can be made especially for the highly branched molecules to reduce drastically the dimensionality and correspondingly the amount of the tabulated data that is needed to be stored. Despite these approximations, the dependencies between the various geometrical variables can be still well considered, as evident from a nearly perfect acceptance rate achieved. For all cases, the bending angles were shown to be sampled correctly by this method with an acceptance rate of at least 96% for 2,2-dimethylpropane to more than 99% for propane. Since only one trial is required to be generated for each bending angle (instead of thousands of trials required by the conventional algorithm), this method can dramatically reduce the simulation time. The profiling results of our Monte Carlo simulation code show that trial generation, which used to be the most time consuming process, is no longer the time dominating component of the simulation.
Creating localized-droplet train by traveling thermal waves
Authors: Frumkin Valeri , Mao Wenbin , Alexeev Alexander , Oron Alexander
Published: August 2014

We investigate the nonlinear dynamics of a two-layer system consisting of a thin liquid film and an overlying gas layer driven by the Marangoni instability induced by thermal waves propagating along the solid substrate. In the case of a stationary thermal wave with sufficiently large amplitude and Marangoni number, liquid film rupture takes place with a flattish wide trough. For sufficiently small but not too small frequencies of the thermal wave, a periodic structure consisting of localized drops interconnected by thin liquid bridges emerges. This train of drops travels unidirectionally along the heated substrate following the thermal wave. For larger thermal wave frequencies, the thickness of the bridges increases enabling fluid flow between the neighboring drops. The drop-train regimes may be utilized in microfluidic applications for directed transport of liquid content enclosed in drops formed by thermocapillary forces.
Electronic structures and water reactivity of mixed metal sulfide cluster anions
Authors: Saha Arjun , Raghavachari Krishnan
Published: August 2014

The electronic structures and chemical reactivity of the mixed metal sulfide cluster anion (MoWS4−) have been investigated with density functional theory. Our study reveals the presence of two almost isoenergetic structural isomers, both containing two bridging sulfur atoms in a quartet state. However, the arrangement of the terminal sulfur atoms is different in the two isomers. In one isomer, the two metals are in the same oxidation state (each attached to one terminal S). In the second isomer, the two metals are in different oxidation states (with W in the higher oxidation state attached to both terminal S). The reactivity of water with the two lowest energy isomers has also been studied, with an emphasis on pathways leading to H2 release. The reactive behavior of the two isomers is different though the overall barriers in both systems are small. The origin of the differences are analyzed and discussed. The reaction pathways and barriers are compared with the corresponding behavior of monometallic sulfides (Mo2S4− and W2S4−) as well as mixed metal oxides (MoWO4−).
Conductance fluctuations in Si nanowires studied from first-principles
Authors: Iori Federico , Ossicini Stefano , Rurali Riccardo
Published: August 2014

We study how the variability of the conductance associated with single-dopant configurations affects the overall conductivity of long, realistic ultrathin Si nanowires (NW). We calculate the resistance associated with each single-dopant configuration from density-functional theory (DFT) calculations and we sum them up classically to obtain the resistance of the long wire. This allows to identify limiting factors for the performance of Si NWs based devices.
Intrinsic correlations between dynamic heterogeneity and conformational transition in polymers during glass transition
Authors: Nie Yijing , Ye Xubo , Zhou Zhiping , Yang Wenming , Tao Lu
Published: August 2014

We performed dynamic Monte Carlo simulation to investigate the micro-structural evolutions of polymers during glass transition. A new parameter, probability of segment movement, was proposed to probe the heterogeneity of local segment dynamics. A microscopic picture of spatial distribution of dynamic heterogeneity was obtained. A conformational transition was also detected. Further analysis demonstrated the existence of intrinsic links between the two phenomena. Compared with chain segments with gauche-conformation, segments with trans-conformation were packed more closely, and thus easier to be frozen. This difference in segmental mobility between the gauche- and trans-conformations results in the emergence of dynamic heterogeneity. Our simulation results reveal the underlying mechanism controlling the dynamic heterogeneity during glass transition from the viewpoint of local conformational changes.
Disjoining pressure of an electrolyte film confined between semipermeable membranes
Authors: Maduar Salim R. , Vinogradova Olga I.
Published: August 2014

We consider an electrolyte solution confined by infinitesimally thin semipermeable membranes in contact with a salt-free solvent. Membranes are uncharged, but since small counter-ions leak-out into infinite salt-free reservoirs, we observe a distance-dependent membrane potential, which generates a repulsive electrostatic disjoining pressure. We obtain the distribution of the potential and of ions, and derive explicit formulas for the disjoining pressure, which are validated by computer simulations. We predict a strong short-range power-law repulsion, and a weaker long-range exponential decay. Our results also demonstrate that an interaction between membranes does strongly depend on the screening lengths, valency of an electrolyte solution, and an inter-membrane film thickness. Finally, our analysis can be directly extended to the study of more complex situations and some biological problems.
On Type VI–V transition in hypersonic double-wedge flows with thermo-chemical non-equilibrium effects
Authors: Li Ji , Zhu Yujian , Luo Xisheng
Published: August 2014

The transition from Type VI to V of inviscid shock interactions on a double-wedge geometry is investigated theoretically and numerically for hypersonic non-equilibrium gas flows. The shock polar method valid for the non-equilibrium gas is developed by introducing a non-equilibrium relaxation length. A preliminary rule for choosing the suitable non-equilibrium relaxation length in different regions of the double-wedge flow is proposed by analyzing the relaxing characteristics. Following this proposal, the shock polar method valid for the non-equilibrium gas can be easily applied to other hypersonic shock interactions. Numerical simulation is used to capture the complete transition from Type VI to V and to obtain the second wedge angle span for this process. The comparison between the theory and the computation indicates that the shock polar method for the non-equilibrium gas can well predict the regional pressure and the critical angle. It is found that the non-equilibrium gas effects lead to a larger second wedge angle for the shock interaction transition and these effects become more significant with a larger Mach number of the inflow. It is interesting that the variation of the transition wedge angle with the Mach number of inflow behaves oppositely for the calorically perfect gas and the non-equilibrium gas.
Free falling and rising of spherical and angular particles
Authors: Rahmani M. , Wachs A.
Published: August 2014

Direct numerical simulations of freely falling and rising particles in an infinitely long domain, with periodic lateral boundary conditions, are performed. The focus is on characterizing the free motion of cubical and tetrahedral particles for different Reynolds numbers, as an extension to the well-studied behaviour of freely falling and rising spherical bodies. The vortical structure of the wake, dynamics of particle movement, and the interaction of the particle with its wake are studied. The results reveal mechanisms of path instabilities for angular particles, which are different from those for spherical ones. The rotation of the particle plays a more significant role in the transition to chaos for angular particles. Following a framework similar to that of Mougin and Magnaudet [“Wake-induced forces and torques on a zigzagging/spiralling bubble,” J. Fluid Mech. 567, 185–194 (2006)], the balance of forces and torques acting on particles is discussed to gain more insight into the path instabilities of angular particles.
Three-dimensional numerical analysis on blade response of a vertical-axis tidal current turbine under operational conditions
Authors: Li Ye , Karri Naveen , Wang Qi
Published: August 2014

Tidal current as a large-scale renewable source of energy has received significant attention recently. The technology used to harvest energy from tidal current is called a tidal current turbine. Although some of the principles of wind turbine design are applicable to tidal current turbines, to ensure long-term reliability in tidal current turbines, designers must consider elements such as cavitation damage and corrosion. Depending on the orientation of axis, tidal current turbines can be classified as vertical-axis turbines or horizontal-axis turbines. Existing studies on the vertical-axis tidal current turbines focus more on the hydrodynamic aspects of the turbine rather than the structural aspects. This paper summarizes our recent efforts to study the integrated hydrodynamic and structural aspects of vertical-axis tidal current turbines. After reviewing existing methods for modeling tidal current turbines, we developed a hybrid approach that combines a discrete vortex method with a finite element method that can simulate the integrated hydrodynamic and structural response of a vertical-axis turbine. This hybrid method was employed to analyze a typical three-blade vertical-axis turbine. The power coefficient was used to evaluate the hydrodynamic performance, and critical deflection was considered to evaluate the structural reliability. A sensitivity analysis was also conducted with various turbine height-to-radius (H/R) ratios. The results indicated that both the power output and failure probability increase with the turbine height, suggesting a necessity for optimal design. The optimization of a three-blade vertical-axis turbine design using the hybrid method yielded a turbine H/R ratio of about 3.0 for reliable maximum power output.
Mode couplings in a two-stream free-electron laser with a helical wiggler and an ion-channel guiding
Authors: Mohsenpour Taghi , Alirezaee Hajar
Published: August 2014

In this study, the method of perturbation has been applied to obtain the dispersion relation (DR) of a two-stream free-electron laser (FEL) with a helical wiggler and an ion-channel with all relativistic effects on waves. This DR has been solved numerically to find the unstable modes and their growth rate. Numerical solutions of DR show that the growth rate is considerably enhanced in comparison with single-stream free-electron laser. In group II orbits, with relatively large wiggler induced velocities, new couplings are found. The effect of the velocity difference of the two electron beams on the instabilities has also been investigated in this study. Moreover, the effect of the ion-channel density on the maximum growth rate of FEL resonance has been analyzed.
Multi-scale approach for the rheological characteristics of emulsions using molecular dynamics and lattice Boltzmann method
Authors: Choi Se Bin , Yoon Hong Min , Lee Joon Sang
Published: August 2014

An emulsion system was simulated under simple shear rates to analyze its rheological characteristics using a hierarchical multi-scale approach. The molecular dynamics (MD) simulation was used to describe the interface of droplets in an emulsion. The equations derived from the MD simulation relative to interfacial tension, temperature, and surfactant concentration were applied as input parameters within lattice Boltzmann method (LBM) calculations. In the LBM simulation, we calculated the relative viscosity of an emulsion under a simple shear rate along with changes in temperature, shear rate, and surfactant concentration. The equations from the MD simulation showed that the interfacial tension of the droplets tended to decrease with an increase in temperature and surfactant concentration. The relative viscosity from the LBM simulation decreased with an increase in temperature. The shear thinning phenomena explaining the inverse proportion between shear rate and viscosity were observed. An increase in the surfactant concentration caused an increase in the relative viscosity for a decane-in-water emulsion, because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.
Magnetoelectric effect in magnetostrictive/piezoelectric laminated composite operating in shear-shear mode
Authors: Liu Guoxi , Zhang Chunli , Dong Shuxiang
Published: August 2014

This paper investigates the magnetoelectric (ME) effect of magnetostrictive/piezoelectric laminated composite operating in a shear-shear (S-S) mode, i.e., the magnetostrictive and piezoelectric phases of the laminated composite both operate in thickness shear modes. Theoretical analysis shows that the S-S mode laminated ME composite exhibits stronger ME coupling coefficients, i.e., the ME electric field, voltage, and charge coefficients, than those of a typical L-T mode laminated ME composite (longitudinally magnetized and transversely polarized) because of the higher piezomagnetic and piezoelectric coefficients in thickness shear modes of the magnetostrictive and piezoelectric phases, respectively. Our theoretical analysis provides the optimum design method for practical applications of the S-S mode laminated ME composite.
Observation of a new high-β and high-density state of a magnetospheric plasma in RT-1
Authors: Saitoh H. , Yano Y. , Yoshida Z. , Nishiura M. , Morikawa J. , Kawazura Y. , Nogami T. , Yamasaki M.
Published: August 2014

A new high-β and high-density state is reported for a plasma confined in a laboratory magnetosphere. In order to expand the parameter regime of an electron cyclotron resonance heating experiment, the 8.2 GHz microwave power of the Ring Trap 1 device has been upgraded with the installation of a new waveguide system. The rated input power launched from a klystron was increased from 25 to 50 kW, which enabled the more stable formation of a hot-electron high-β plasma. The diamagnetic signal (the averaged value of four magnetic loops signals) of a plasma reached 5.2 mWb. According to a two-dimensional Grad-Shafranov analysis, the corresponding local β value is close to 100%.
Energy and frequency dependence of the alpha particle redistribution produced by internal kink modes
Authors: Farengo R. , Ferrari H. E. , Garcia-Martinez P. L. , Firpo M.-C. , Ettoumi W. , Lifschitz A. F.
Published: August 2014

The redistribution of alpha particles due to internal kink modes is studied. The exact particle trajectories in the total fields, equilibrium plus perturbation, are calculated. The equilibrium has circular cross section and the plasma parameters are similar to those expected in ITER. The alpha particles are initially distributed according to a slowing down distribution function and have energies between 18 keV and 3.5 MeV. The (1, 1), (2, 2), and (2, 1) modes are included and the effect of changing their amplitude and frequency is studied. When only the (1, 1) mode is included, the spreading of high energy (E≳1 MeV) alpha particles increases slowly with the energy and mode frequency. At lower energies, the redistribution is more sensitive to the mode frequency and particle energy. When a (2, 1) mode is added, the spreading increases significantly and particles can reach the edge of the plasma. Trapped particles are the most affected and the redistribution parameter can have maxima above 1 MeV, depending on the mode frequency. These results can have important implications for ash removal.
Non-linear tearing of 3D null point current sheets
Authors: Wyper P. F. , Pontin D. I.
Published: August 2014

The manner in which the rate of magnetic reconnection scales with the Lundquist number in realistic three-dimensional (3D) geometries is still an unsolved problem. It has been demonstrated that in 2D rapid non-linear tearing allows the reconnection rate to become almost independent of the Lundquist number (the “plasmoid instability”). Here, we present the first study of an analogous instability in a fully 3D geometry, defined by a magnetic null point. The 3D null current layer is found to be susceptible to an analogous instability but is marginally more stable than an equivalent 2D Sweet-Parker-like layer. Tearing of the sheet creates a thin boundary layer around the separatrix surface, contained within a flux envelope with a hyperbolic structure that mimics a spine-fan topology. Efficient mixing of flux between the two topological domains occurs as the flux rope structures created during the tearing process evolve within this envelope. This leads to a substantial increase in the rate of reconnection between the two domains.