bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Train Derailments Caused by Damage to Suspension Systems
Authors: Ju S. H.
Published: August 2015

A nonlinear finite element method was used to investigate the derailments of trains moving on multispan simply supported bridges due to damage to suspension systems. At the simulation beginning, the initial vertical trainloads to simulate the train gravity weight are gradually added into the mass center of each rigid body in the train model with large system damping, so the initial fake vibration is well reduced. A suspension is then set to damage within the damage interval time, while the spring and/or damper changes from no damage to a given percentage of damage. Finite element parametric studies indicate the following: (1) the derailment coefficients of the wheel axis nearby the damage location are significantly increased. (2) Damage to the spring is more critical than that to the damper for the train derailment effect. (3) The derailment coefficient induced by damage to the primary suspension is more serious than that to the secondary suspension. (4) If rail irregularities are neglected, the train speed has little influence on the derailment coefficients generated from damage to suspensions. (5) The train derailment coefficients rise with a decrease in the damage interval time, so sudden damages to suspension systems should be avoided.
On the Importance of Displacement History in Soft-Body Contact Models
Authors: Fleischmann Jonathan , Serban Radu , Negrut Dan , Jayakumar Paramsothy
Published: August 2015

Two approaches are commonly used for handling frictional contact within the framework of the discrete element method (DEM). One relies on the complementarity method (CM) to enforce a nonpenetration condition and the Coulomb dry-friction model at the interface between two bodies in mutual contact. The second approach, called the penalty method (PM), invokes an elasticity argument to produce a frictional contact force that factors in the local deformation and relative motion of the bodies in contact. We give a brief presentation of a DEM-PM contact model that includes multi-time-step tangential contact displacement history. We show that its implementation in an open-source simulation capability called Chrono is capable of accurately reproducing results from physical tests typical of the field of geomechanics, i.e., direct shear tests on a monodisperse material. Keeping track of the tangential contact displacement history emerges as a key element of the model. We show that identical simulations using contact models that include either no tangential contact displacement history or only single-time-step tangential contact displacement history are unable to accurately model the direct shear test.
Framework for alternating-least-squares-based multivariate curve resolution with application to time-of-flight secondary ion mass spectrometry imaging
Authors: Keenan Michael R. , Windig Willem , Arlinghaus Henrik
Published: August 2015

Multivariate statistical analysis, in general, and multivariate curve resolution (MCR), in particular, have found an important role in extracting chemical information from the very large datasets typical of time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging. MCR seeks to uncover and describe the underlying chemistry that gives rise to the spectral image. It is often implemented with alternating least squares procedures that include physically inspired constraints, like non-negativity of concentrations and mass spectra, to guide the solution process toward those that are physically plausible. Besides appropriate constraints, the ToF-SIMS community has long recognized the importance of proper preprocessing of the mass spectra to achieving good results. This has led to an analysis paradigm of preprocess–analyze–postprocess. In this article, a number of limitations of this approach will be identified, and the authors propose a framework for MCR calculations that integrates the three steps into a unified algorithm that is implemented with alternating weighted least squares and is numerically efficient. Several advantages of the proposed framework are illustrated with simple examples, some of which are not easily accommodated by the existing approach. As a byproduct, a couple of new analyses are suggested. These include a new variant of the angle constraint that expresses a preference for relatively orthogonal image components, an alternative maximum autocorrelation factors-like procedure for empirically estimating the error covariance matrix, and an approach that may be suitable for simultaneously analyzing several spectral images that share a common chemistry.
Surface chemistry of InP ridge structures etched in Cl2-based plasma analyzed with angular XPS
Authors: Bouchoule Sophie , Chanson Romain , Pageau Arnaud , Cambril Edmond , Guilet Stephane , Rhallabi Ahmed , Cardinaud Christophe
Published: August 2015

Two x-ray photoelectron spectroscopy configurations are proposed to analyze the surface chemistry of micron-scale InP ridge structures etched in chlorine-based inductively coupled plasma (ICP). Either a classical or a grazing configuration allows to retrieve information about the surface chemistry of the bottom surface and sidewalls of the etched features. The procedure is used to study the stoichiometry of the etched surface as a function of ridge aspect ratio for Cl2/Ar and Cl2/H2 plasma chemistries. The results show that the bottom surface and the etched sidewalls are P-rich, and indicate that the P-enrichment mechanism is rather chemically driven. Results also evidence that adding H2 to Cl2 does not necessarily leads to a more balanced surface stoichiometry. This is in contrast with recent experimental results obtained with the HBr ICP chemistry for which fairly stoichiometric surfaces have been obtained.
Characterization of CdMnTe films deposited from polycrystalline powder source using closed-space sublimation method
Authors: Lai Jianming , Wang Junnan , Wang Lin , Ji Huanhuan , Xu Run , Zhang Jijun , Huang Jian , Shen Yue , Min Jiahua , Wang Linjun , Xia Yiben
Published: August 2015

CdMnTe films were prepared on quartz substrates by closed-space sublimation of polycrystalline Cd0.74Mn0.26Te powders. This was performed at different substrate temperatures (Ts = 200, 300, 350, and 400 °C). The interfacial adhesion strength between the films and substrates, when fabricated from polycrystalline powders, was greater than that of films grown using a bulk source. X-ray diffraction studies revealed that the as-deposited films had a zinc blende structure with a preferential (111) orientation. Precipitation of Te occurred in the films deposited at Ts = 200 °C, as confirmed using scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. The growth mode and re-evaporation dependence on the value of Ts of the films were investigated. Our results suggested that materials suitable for radiation detection can be grown from a powder source at lower substrate temperatures then when grown from a bulk source.
Thermal chemistry of copper acetamidinate atomic layer deposition precursors on silicon oxide surfaces studied by XPS
Authors: Yao Yunxi , Zaera Francisco
Published: August 2015

The thermal surface chemistry of copper(I)-N,N′-di-sec-butylacetamidinate, [Cu(sBu-amd)]2, a metalorganic complex recently proposed for the chemical-based deposition of copper films, has been characterized on SiO2 films under ultrahigh vacuum conditions by x-ray photoelectron spectroscopy (XPS). Initial adsorption at cryogenic temperatures results in the oxidation of the copper centers with Cu 2p3/2 XPS binding energies close to those seen for a +2 oxidation state, an observation that the authors interpret as the result of the additional coordination of oxygen atoms from the surface to the Cu atoms of the molecular acetamidinate dimer. Either heating to 300 K or dosing the precursor directly at that temperature leads to the loss of one of its two ligands, presumably via hydrogenation/protonation with a hydrogen/proton from a silanol group, or following a similar reaction on a defect site. By approximately 500 K the Cu 2p3/2, C 1s, and N 1s XPS data suggest that the remaining acetamidinate ligand is displaced from the copper center and bonds to the silicon oxide directly, after which temperatures above 900 K need to be reached to promote further (and only partial) decomposition of those organic moieties. It was also shown that the uptake of the Cu precursor is self-limiting at either 300 or 500 K, although the initial chemistry is somewhat different at the two temperatures, and that the nature of the substrate also defines reactivity, with the thin native silicon oxide layer always present on Si(100) surfaces being less reactive than thicker films grown by evaporation, presumably because of the lower density of surface nucleation sites.
Li induced effects in the core level and π-band electronic structure of graphene grown on C-face SiC
Authors: Johansson Leif I. , Xia Chao , Virojanadara Chariya
Published: August 2015

Studies of the effects induced in the electronic structure after Li deposition, and subsequent heating, on graphene samples prepared on C-face SiC are reported. The as prepared graphene samples are essentially undoped, but after Li deposition, the Dirac point shifts down to 1.2 eV below the Fermi level due to electron doping. The shape of the C 1s level also indicates a doping concentration of around 1014 cm−2 after Li deposition, when compared with recent calculated results of core level spectra of graphene. The C 1s, Si 2p, and Li 1s core level results show little intercalation directly after deposition but that most of the Li has intercalated after heating at 280 °C. Heating at higher temperatures leads to desorption of Li from the sample, and at 1030 °C, Li can no longer be detected on the sample. The single π-band observable from multilayer C-face graphene samples in conventional angle resolved photoelectron spectroscopy is reasonably sharp both on the initially prepared sample and after Li deposition. After heating at 280 °C, the π-band appears more diffuse and possibly split. The Dirac point becomes located at 0.4 eV below the Fermi level, which indicates occurrence of a significant reduction in the electron doping concentration. Constant energy photoelectron distribution patterns extracted from the as prepared graphene C-face sample and also after Li deposition and heating at 280 °C look very similar to earlier calculated distribution patterns for monolayer graphene.
Passive models of viscothermal wave propagation in acoustic tubes
Authors: Bilbao Stefan , Harrison Reginald , Kergomard Jean , Lombard Bruno , Vergez Christophe
Published: August 2015

A continued fraction expansion to the immittances defining viscothermal wave propagation in a cylindrical tube has been presented recently in this journal, intended as a starting point for time domain numerical method design. Though the approximation has the great benefit of passivity, or positive realness under truncation, its convergence is slow leading to approximations of high order in practice. Other passive structures, when combined with optimisation methods, can lead to good accuracy over a wide frequency range, and for relatively low order.
Body Mass-Related Predictors of the Female Athlete Triad Among Adolescent Athletes
Authors: Thralls Katie J. , Nichols Jeanne F. , Barrack Michelle T. , Kern Mark , Rauh Mitchell J.
Published: August 2015

Early detection of the female athlete triad is essential for the long-term health of adolescent female athletes. The purpose of this study was to assess relationships between common anthropometric markers (ideal body weight [IBW] via the Hamwi formula, youth-percentile body mass index [BMI], adult BMI categories, and body fat percentage [BF%]) and triad components, (low energy availability [EA], measured by dietary restraint [DR], menstrual dysfunction [MD], low bone mineral density [BMD]). In the sample (n = 320) of adolescent female athletes (age 15.9± 1.2 y), Spearman’s rho correlations and multiple logistic regression analyses evaluated associations between anthropometric clinical cutoffs and triad components. All underweight categories for the anthropometric measures predicted greater likelihood of MD and low BMD. Athletes with an IBW ≤85% were nearly 4 times more likely to report MD (OR = 3.7, 95% CI [1.8, 7.9]) and had low BMD (OR = 4.1, 95% CI [1.2, 14.2]). Those in <5th percentile for their age-specific BMI were 9 times more likely to report MD (OR 9.1, 95% CI [1.8, 46.9]) and had low BMD than those in the 50th to 85th percentile. Athletes with a high BF% were almost 3 times more likely to report DR (OR = 2.8, 95% CI [1.4, 6.1]). Our study indicates that low age-adjusted BMI and low IBW may serve as evidence-based clinical indicators that may be practically evaluated in the field, predicting MD and low BMD in adolescents. These measures should be tested for their ability as tools to minimize the risk for the triad.
A Combination of Amino Acids and Caffeine Enhances Sprint Running Capacity in a Hot, Hypoxic Environment
Authors: Eaton Tom R. , Potter Aaron , Billaut François , Panchuk Derek , Pyne David B. , Gore Christopher J. , Chen Ting-Ting , McQuade Leon , Stepto Nigel K.
Published: August 2015

Heat and hypoxia exacerbate central nervous system (CNS) fatigue. We therefore investigated whether essential amino acid (EAA) and caffeine ingestion attenuates CNS fatigue in a simulated team sport–specific running protocol in a hot, hypoxic environment. Subelite male team sport athletes (n = 8) performed a repeat sprint running protocol on a nonmotorized treadmill in an extreme environment on 4 separate occasions. Participants ingested one of four supplements: a double placebo, 3 mg.kg-1 body mass of caffeine + placebo, 2 × 7 g EAA (Musashi Create)+placebo, or caffeine + EAA before each exercise session using a randomized, double-blind crossover design. Electromyography (EMG) activity and quadriceps evoked responses to magnetic stimulation were assessed from the dominant leg at preexercise, halftime, and postexercise. Central activation ratio (CAR) was used to quantify completeness of quadriceps activation. Oxygenation of the prefrontal cortex was measured via near-infrared spectroscopy. Mean sprint work was higher (M = 174 J, 95% CI [23, 324], p < .05, d = 0.30; effect size, likely beneficial) in the caffeine + EAA condition versus EAAs alone. The decline in EMG activity was less (M = 13%, 95% CI [0, 26]; p < .01, d = 0.58, likely beneficial) in caffeine + EAA versus EAA alone. Similarly, the pre- to postexercise decrement in CAR was significantly less (M = −2.7%, 95% CI [0.4, 5.4]; p < .05, d = 0.50, likely beneficial) when caffeine + EAA were ingested compared with placebo. Cerebral oxygenation was lower (M = −5.6%, 95% CI [1.0, 10.1]; p < .01, d = 0.60, very likely beneficial) in the caffeine + EAA condition compared with LNAA alone. Coingestion of caffeine and EAA appears to maintain muscle activation and central drive, with a small improvement in running performance.
Amino Acid Mixture Enriched With Arginine, Alanine, and Phenylalanine Stimulates Fat Metabolism During Exercise
Authors: Ueda Keisuke , Nakamura Yutaka , Yamaguchi Makoto , Mori Takeshi , Uchida Masayuki , Fujita Satoshi
Published: August 2015

Although there have been many investigations of the beneficial effects of both exercise and amino acids (AAs), little is known about their combined effects on the single-dose ingestion of AAs for lipid metabolism during exercise. We hypothesize that taking a specific combination of AAs implicated in glucagon secretion during exercise may increase fat metabolism. We recently developed a new mixture, d–AA mixture (D-mix), that contains arginine, alanine, and phenylalanine to investigate fat oxidation. In a double-blind, placebo-controlled crossover study, 10 healthy male volunteers were randomized to ingest either D-mix (3 g/dose) or placebo. Subjects in each condition subsequently performed a physical task that included workload trials on a cycle ergometer at 50% of maximal oxygen consumption for 1 hr. After oral intake of D-mix, maximum serum concentrations of glycerol (9.32 ± 6.29 mg/L and 5.22 ± 2.22 mg/L, respectively; p = .028), free fatty acid level (0.77 ± 0.26 mEq/L and 0.63 ± 0.28 mEq/L, respectively; p = .022), and acetoacetic acid levels (37.9 ± 17.7 μmol/L and 30.3 ± 13.9 μmol/L, respectively; p = .040) were significantly higher than in the placebo groups. The area under the curve for glucagon during recovery was numerically higher than placebo (6.61 ± 1.33 μg/L • min and 6.06 ± 1.23 μg/L • min, respectively; p = .099). These results suggest that preexercise ingestion of D-mix may stimulate fat metabolism. Combined with exercise, the administration of AA mixtures could prove to be a useful nutritional strategy to maximize fat metabolism.
Effect of Resistance Training and Various Sources of Protein Supplementation on Body Fat Mass and Metabolic Profile in Sarcopenic Overweight Older Adult Men: A Pilot Study
Authors: Maltais Mathieu L. , Perreault Karine , Courchesne-Loyer Alexandre , Lagacé Jean-Christophe , Barsalani Razieh , Dionne Isabelle J.
Published: August 2015

The decrease in resting energy expenditure (REE) and fat oxidation with aging is associated with an increase in fat mass (FM), and both could be prevented by exercise such as resistance training. Dairy consumption has also been shown to promote FM loss in different subpopulations and to be positively associated with fat oxidation. Therefore, we sought to determine whether resistance exercise combined with dairy supplementation could have an additive impact on FM and energy metabolism, especially in individuals with a deficit in muscle mass. Twenty-six older overweight sarcopenic men (65 ± 5 years old) were recruited for the study. They participated in 4 months of resistance exercise and were randomized into three groups for postexercise shakes (control, dairy, and nondairy isocaloric and isoprotein supplement with 375 ml and ~280 calories per shake). Body composition was measured by dual X-ray absorptiometry and REE by indirect calorimetry. Fasting glucose, insulin, leptin, inflammatory profile, and blood lipid profile were also measured. Significant decreases were observed with FM only in the dairy supplement group; no changes were observed for any other variables. To conclude, FM may decrease without changes in metabolic parameters during resistance training and dairy supplementation with no caloric restriction without having any impact on metabolic properties. More studies are warranted to explain this significant decrease in FM.
Nutritional Considerations for the Overweight Young Athlete
Authors: Chu Lisa , Timmons Brian W.
Published: August 2015

Nutritional considerations for the overweight young athlete have not been thoroughly discussed in the scientific literature. With the high prevalence of childhood obesity, more children participating in sports are overweight or obese. This is particularly true for select sports, such as American football, where large size provides an added advantage. While sport participation should be encouraged because of the many benefits of physical activity, appropriate nutritional practices are vital for growth, and optimizing performance and health. The overweight young athlete may face certain challenges because of variable energy costs and nutrient requirements for growth and routine training, compared with nonoverweight athletes. Special attention should be given to adopting healthy lifestyle choices to prevent adverse health effects due to increased adiposity. In this review, we aim to discuss special nutritional considerations and highlight gaps in the literature concerning nutrition for overweight young athletes compared with their nonoverweight peers.
Effects of Short-Term Exercise Training With and Without Milk Intake on Cardiometabolic and Inflammatory Adaptations in Obese Adolescents
Authors: Liu Maple , Gillis Linda J. , Persadie Nicholas R. , Atkinson Stephanie A. , Phillips Stuart M. , Timmons Brian W.
Published: August 2015

There is some evidence that a combination of factors can reduce inflammation and associated metabolic risk factors. We studied the early cardiometabolic and inflammatory adaptations to a short-term exercise intervention with and without milk in obese adolescents. Fifty-four adolescents were randomized to consume milk post exercise (MILK) or a carbohydrate beverage (CONT) during one-week of daily exercise. Insulin levels were not different between the groups post training. Glucose was reduced over time in both groups (-9 ± 13 mg/dl MILK and -6 ± 14 mg/dl CONT, p < .05) but not different between groups. There was a greater decrease in mean arterial pressure (MAP) in the MILK group (-3 ± 6 mmHg MILK vs. 2 ± 7 mmHg CONT, p < .04). Milk provided postexercise did not affect C-reactive protein (CRP), tumor necrosis factor-α (TNF-α) or interleukin-6 (IL-6). The exercise intervention led to an increase in TNF-α in both groups (0.27 ± 0.7 pg/ml MILK and 0.48 ± 0.6 pg/ml CONT, p < .001). The early adaptations to a short-term exercise intervention in obese adolescents include a reduction in MAP and an increase in some inflammatory markers.
Effects of a Cognitively Demanding Aerobic Intervention During Recess on Children’s Physical Fitness and Executive Functioning
Authors: van der Niet Anneke G. , Smith Joanne , Oosterlaan Jaap , Scherder Erik J.A. , Hartman Esther , Visscher Chris
Published: August 2015

The objective of this study was to analyze the effects of a physical activity program including both aerobic exercise and cognitively engaging physical activities on children’s physical fitness and executive functions. Children from 3 primary schools (aged 8–12 years) were recruited. A quasi-experimental design was used. Children in the intervention group (n = 53; 19 boys, 34 girls) participated in a 22-week physical activity program for 30 min during lunch recess, twice a week. Children in the control group (n = 52; 32 boys, 20 girls) followed their normal lunch routine. Aerobic fitness, speed and agility, and muscle strength were assessed using the Eurofit test battery. Executive functions were assessed using tasks measuring inhibition (Stroop test), working memory (Visual Memory Span test, Digit Span test), cognitive flexibility (Trailmaking test), and planning (Tower of London). Children in the intervention group showed significantly greater improvement than children in the control group on the Stroop test and Digit Span test, reflecting enhanced inhibition and verbal working memory skills, respectively. No differences were found on any of the physical fitness variables. A physical activity program including aerobic exercise and cognitively engaging physical activities can enhance aspects of executive functioning in primary school children.
Solitary osteochondroma of the trapezoid disguised as a tooth fragment
Authors: Baumann Andreas , Pereira Daniela , Baldwin Katy , Weusten Axel
Published: August 2015

Fight bite injuries of the hand are common presentations in A&E departments and usually result from a fist blow to the mouth. The authors report a case of a 24-year-old man who presented 6 weeks after an injury to his right wrist following an altercation. Radiographic examination and CT scans were in keeping with a tooth fragment embedded in the trapezoid. However, post excision histology subsequently revealed the lesion to be a solitary osteochondroma of the trapezoid. Osteochondromas are benign lesions of bony or cartilaginous origin and are usually found in the metaphyseal region of long bones. They represent by far the most common primary bone tumours. However, osteochondromas arising from the carpal bones are extremely rare with very few cases reported in the literature. This case illustrates the need to include ‘tumour’ as a differential diagnosis in every unusual appearing bony lesion, even if there is a history of trauma.
An epibulbar chocolate cyst: a rare complication of silicone-based scleral buckle
Authors: Venkatesh Pradeep , Gogia Varun , Gupta Shikha , Nayak Bhagabat
Published: August 2015

A patient with a history of vitreoretinal surgery presented with nasal dystopia, diplopia and epibulbar bluish black mass simulating a chocolate cyst in the right eye. After a non-conclusive ocular examination, he underwent CT of the orbit along with volume rendition and three-dimensional reconstruction, which demonstrated intact globe with laterally displaced band-buckle assembly along with peri-scleral buckle element (SBE) soft tissue proliferation. Imaging-assisted exploration of the lesion was performed and retained scleral buckle element (SBE) was removed in toto; thus relieving the patient long-standing dystopia.
Stability of Einstein static universe over Lyra geometry
Authors: Darabi F. , Heydarzade Y. , Hajkarim F.
Published: August 2015

The existence and stability conditions of Einstein static universe against homogeneous scalar perturbations in the context of Lyra geometry is investigated. The stability condition is obtained in terms of the constant equation of state parameter ω = p/ρ depending on energy density ρ0 and scale factor a0 of the initial Einstein static universe. Also, the stability against vector and tensor perturbations is studied. It is shown that a stable Einstein static universe can be found in the context of Lyra geometry against scalar, vector, and tensor perturbations for suitable range and values of physical parameters.
LABOR, PRODUCTIVITY AND SINGAPORE'S DEVELOPMENT MODEL
Authors: PANG ENG FONG , LIM LINDA Y. C.
Published: August 2015

This paper discusses how Singapore's labor market policies since independence have been molded by the state-driven, foreign investment-led, export-oriented, manufacturing-focused development model the country has followed over the past fifty years. The literature we review shows that high GDP growth has been achieved through factor accumulation rather than productivity increase, a strategy of extensive growth that has now run into diminishing returns as well as political, social and resource constraints. Prolonged heavy dependence on imports of foreign labor and skills to attract foreign investment has contributed to low, declining and even negative productivity growth, with low real GDP growth in recent years. In response, the government is pursuing renewed economic restructuring, limiting foreign labor inflows, targeting investments more selectively, and promoting productivity and innovation, so far with uncertain results. This paper suggests that Singapore should let market forces propel the economy toward services, domestic consumption and regional trade, led by domestic private enterprise. But the retreat from established state industrial and social policies will be difficult.
Testing isotropy of cosmos with WMAP and PLANCK data
Authors: Rath Pranati K. , Samal Pramoda Kumar
Published: August 2015

In recent years, there have been a large number of studies which support violation of statistical isotropy. Meanwhile, there are some studies which also found inconsistency. We use the power tensor method defined earlier in the literature to study the new CMBR data. The orientation of these three orthogonal vectors, as well as the power associated with each vector, contains information about possible violation of statistical isotropy. This information is encoded in two entropy measures, the power-entropy and alignment-entropy. We apply this method to WMAP 9-year and PLANCK data. Here, we also revisit the statistics to test high-[Formula: see text] anomaly reported in our earlier paper and find that the high degree of isotropy seen in earlier WMAP 5-year data is absent in the revised WMAP 9-year data.
Gravitational waves, energy and Feynman’s “sticky bead”
Authors: Cooperstock F. I.
Published: August 2015

It is noted that in the broader sense, gravitational waves viewed as spacetime curvature which necessarily accompanies electromagnetic waves at the speed of light, are the routine perception of our everyday experience. We focus on the energy issue and Feynman’s “sticky bead” argument which has been regarded as central in supporting the conclusion that gravitational waves carry energy through the vacuum in general relativity. We discuss the essential neglected aspects of his approach which leads to the conclusion that gravitational waves would not cause Feynman’s bead to heat the stick on which it would supposedly rub. This opens the way to an examination of the entire issue of energy in general relativity. We briefly discuss our naturally-defined totally invariant spacetime energy expression for general relativity incorporating the contribution from gravity. When the cosmological term is included in the field equations, our energy expression includes the vacuum energy as required.
Size and temperature dependent plasmons of quantum particles
Authors: Xiao Mufei , Rakov Nikifor
Published: August 2015

This work reports on the influences of temperature changes on plasmons of metallic particles that are so small that electric carriers in the conduction band are forced to be at discrete sub-bands due to quantum confinement. In the framework of the electron-in-a-box model and with an every-electron-count computational scheme, the spatial electric distribution inside the particle is calculated. In the calculations, the intra-subband fluctuations are taken into account. The numerical results have shown that the small-particle plasmon frequency shifts with the temperature. The findings suggest that it would be possible to control the plasmons of quantum particles externally.
Bandgap modulation and hydrogen storage with Cr-doped BN sheets
Authors: Ma Shengqian
Published: August 2015

The theoretical calculations indicate that the metal-doped boron nitride (BN) sheets are potential materials to store the hydrogen and tune the bandgap. It is all known that the BN sheet is a nonmagnetic wide-bandgap semiconductor. Using density function theory (DFT), the lattice parameters of Cr-doped BN sheets are optimized, which are still kept on two-dimensional (2D) planar geometry, and the bandgap and [Formula: see text] storage are studied. The simulation results show that the [Formula: see text] molecule can be easily absorbed by Cr-doped N in BN sheet. As the adsorption energy was greatly decreasing with the increasing number of Cr-doped N, B had an affinity for adsorption of [Formula: see text]. With the increase of Cr doping, the bandgap of Cr-doped BN sheet is decreasing. The bandgap decreases from 4.705 eV to 0.08 eV. So Cr-doped BN sheet is a promising material in storing [Formula: see text] and tuning the bandgap.
First-principles study on the band structure, magnetic and elastic properties of half-metallic Cr2MnAl
Authors: Qi Santao , Zhang Chuan-Hui , Chen Bao , Shen Jiang
Published: August 2015

In this study, we have investigated the structural, electronic, magnetic and elastic properties of the full-Heusler [Formula: see text] alloy in the framework of density functional theory with generalized gradient approximation (GGA). The calculated results showed that [Formula: see text] was stable in ferrimagnetic configuration and crystallized in the [Formula: see text]-type structure. From the band structure and density of states calculation results, we concluded that [Formula: see text] belongs to a kind of half-metallic compound with an indirect band gap of 0.37 eV. Immediately thereafter, we have analyzed the origin of half-metallic band gap. The total magnetic moment of [Formula: see text] at the stable state is [Formula: see text] per formula unit, obeying the Slater–Pauling rule [Formula: see text]. In addition, various mechanical properties have been obtained and discussed based on the three principle elastic tensor elements [Formula: see text] and [Formula: see text] for the first time in the present work. We expect that our calculated results may trigger the application of [Formula: see text] in future spintronics field.
Evaluation of the quality for sheet deep drawing using a magnetorheological fluid (MRF)
Authors: Li Feng , Xu Peng , Sui Xiaochong , Zhou Fujian
Published: August 2015

Sealing problems, subsequent cleaning processes and poor force transmission effect etc. series of problems which strongly restrict the development and application of traditional medium pressure-based sheet forming technology. To overcome these problems, the magnetorheological fluid (MRF) can be used as the alternative force transmission medium. In this study, the deep drawing process of a 304 stainless steel sheet using MRF was investigated. The die cavity was filled with MRF and electric current was used to quantitatively adjust the magnetic fields distribution, which then controls the deformation behavior of the forming sheet. As compared to the conventional deep drawing process, experimental results clearly show that significant improvement in the produced sample quality was obtained when using the MRF with the electric current of 2 A. These improvements include: the height of the boundary circle reduces by 20%, the wall thickness distribution is more uniform, the rebound ratio correspondingly reduces from 9.6% to 0.67%, and the degree of sticking mode and the size precision are significantly increased. The results of this study provide scientific guidance to solve the bottleneck in the traditional deep drawing forming technology. The potential applications of the MRF-based new deep drawing technology to improve the product quality were explored.
Effect of Magnetic Field on Generalized Thermo-Viscoelastic Diffusion Medium with Voids
Authors: Othman Mohamed I. A. , Fekry Montaser
Published: August 2015

The present paper is concerned with the investigation of disturbances in a homogeneous, isotropic, generalized thermo-viscoelastic diffusion material with voids under the influence of magnetic field. The formulation is applied to the generalized thermoelasticity theory under the Lord–Shulman and the classical dynamical coupled theories. The analytical expressions for the physical quantities are obtained in the physical domain by using the normal mode analysis. These expressions are calculated numerically for a specific material and explained graphically. Comparisons are made with the results predicted by the Lord–Shulman and the coupled theories in the presence and absence of the magnetic field and diffusion.
An Efficient Algorithm for Nonlinear Analysis of Vehicle/Track Interaction Problems
Authors: Sadeghi J. , Khajehdezfuly A. , Esmaeili M. , Poorveis D.
Published: August 2015

In this paper, a new algorithm for solving the vehicle/track dynamic interaction problem is developed, aimed at reducing the computational cost. The algorithm called Advanced Solver Algorithm (ASA) uses the full Newton–Raphson incremental-iterative method in conjunction with the Newmark integration scheme to solve the equilibrium equations of the coupled vehicle/track system in time domain. Considering the track as a beam resting on a viscoelastic foundation and each vehicle as a wagon with ten degrees of freedom, the governing differential equations of motion of the vehicle/track system were derived. The wheel/rail contact was considered as a nonlinear Hertz spring and consequently the vehicle/track nonlinear dynamic interaction problem was solved. A comparison between the results of the ASA and those of the most advanced algorithm available was made to evaluate the efficiency of the ASA. It is confirmed that using the ASA can result in 40–70 % of reduction in computational cost.
Valid Post-Selection and Post-Regularization Inference: An Elementary, General Approach
Authors: Chernozhukov Victor , Hansen Christian , Spindler Martin
Published: August 2015

We present an expository, general analysis of valid post-selection or post-regularization inference about a low-dimensional target parameter in the presence of a very high-dimensional nuisance parameter that is estimated using selection or regularization methods. Our analysis provides a set of high-level conditions under which inference for the low-dimensional parameter based on testing or point estimation methods will be regular despite selection or regularization biases occurring in the estimation of the high-dimensional nuisance parameter. A key element is the use of so-called immunized or orthogonal estimating equations that are locally insensitive to small mistakes in the estimation of the high-dimensional nuisance parameter. As an illustration, we analyze affine-quadratic models and specialize these results to a linear instrumental variables model with many regressors and many instruments. We conclude with a review of other developments in post-selection inference and note that many can be viewed as special cases of the general encompassing framework of orthogonal estimating equations provided in this article.
Credit, Financial Stability, and the Macroeconomy
Authors: Taylor Alan M.
Published: August 2015

Since the 2008 global financial crisis, and after decades of relative neglect, the importance of the financial system and its episodic crises as drivers of macroeconomic outcomes has attracted fresh scrutiny from academics, policy makers, and practitioners. Theoretical advances are following a lead set by a fast-growing empirical literature. Recent long-run historical work has uncovered a range of important stylized facts concerning financial instability and the role of credit in advanced economies, and this article provides an overview of the key findings.
The Effects of Complete Vestibular Deafferentation on Spatial Memory and the Hippocampus in the Rat: The Dunedin Experience
Authors: Smith Paul F. , Darlington Cynthia L. , Zheng Yiwen
Published: August 2015

Our studies conducted over the last 14 years have demonstrated that a complete bilateral vestibular deafferentation (BVD) in rats results in spatial memory deficits in a variety of behavioural tasks, such as the radial arm maze, the foraging task and the spatial T maze, as well as deficits in other tasks such as the five-choice serial reaction time task (5-CSRT task) and object recognition memory task. These deficits persist long after the BVD, and are not simply attributable to ataxia, anxiety, hearing loss or hyperactivity. In tasks such as the foraging task, the spatial memory deficits are evident in darkness when vision is not required to perform the task. The deficits in the radial arm maze, the foraging task and the spatial T maze, in particular, suggest hippocampal dysfunction following BVD, and this is supported by the finding that both hippocampal place cells and theta rhythm are dysfunctional in BVD rats. Now that it is clear that the hippocampus is adversely affected by BVD, the next challenge is to determine what vestibular information is transmitted to it and how that information is used by the hippocampus and the other brain structures with which it interacts.
Gravity in the Brain as a Reference for Space and Time Perception
Authors: Lacquaniti Francesco , Bosco Gianfranco , Gravano Silvio , Indovina Iole , La Scaleia Barbara , Maffei Vincenzo , Zago Myrka
Published: August 2015

Moving and interacting with the environment require a reference for orientation and a scale for calibration in space and time. There is a wide variety of environmental clues and calibrated frames at different locales, but the reference of gravity is ubiquitous on Earth. The pull of gravity on static objects provides a plummet which, together with the horizontal plane, defines a three-dimensional Cartesian frame for visual images. On the other hand, the gravitational acceleration of falling objects can provide a time-stamp on events, because the motion duration of an object accelerated by gravity over a given path is fixed. Indeed, since ancient times, man has been using plumb bobs for spatial surveying, and water clocks or pendulum clocks for time keeping. Here we review behavioral evidence in favor of the hypothesis that the brain is endowed with mechanisms that exploit the presence of gravity to estimate the spatial orientation and the passage of time. Several visual and non-visual (vestibular, haptic, visceral) cues are merged to estimate the orientation of the visual vertical. However, the relative weight of each cue is not fixed, but depends on the specific task. Next, we show that an internal model of the effects of gravity is combined with multisensory signals to time the interception of falling objects, to time the passage through spatial landmarks during virtual navigation, to assess the duration of a gravitational motion, and to judge the naturalness of periodic motion under gravity.
Contribution of Bodily and Gravitational Orientation Cues to Face and Letter Recognition
Authors: Barnett-Cowan Michael , Snow Jacqueline C. , Culham Jody C.
Published: August 2015

Sensory information provided by the vestibular system is crucial in cognitive processes such as the ability to recognize objects. The orientation at which objects are most easily recognized — the perceptual upright (PU) — is influenced by body orientation with respect to gravity as detected from the somatosensory and vestibular systems. To date, the influence of these sensory cues on the PU has been measured using a letter recognition task. Here we assessed whether gravitational influences on letter recognition also extend to human face recognition. 13 right-handed observers were positioned in four body orientations (upright, left-side-down, right-side-down, supine) and visually discriminated ambiguous characters (‘p’-from-‘d’; ‘i’-from-‘!’) and ambiguous faces used in popular visual illusions (‘young woman’-from-‘old woman’; ‘grinning man’-from-‘frowning man’) in a forced-choice paradigm. The two transition points (e.g., ‘p-to-d’ and ‘d-to-p’; ‘young woman-to-old woman’ and ‘old woman-to-young woman’) were fit with a sigmoidal psychometric function and the average of these transitions was taken as the PU for each stimulus category. The results show that both faces and letters are more influenced by body orientation than gravity. However, faces are more optimally recognized when closer in alignment with body orientation than letters — which are more influenced by gravity. Our results indicate that the brain does not utilize a common representation of upright that governs recognition of all object categories. Distinct areas of ventro-temporal cortex that represent faces and letters may weight bodily and gravitational cues differently — possibly to facilitate the specific demands of face and letter recognition.
Making Sense of the Body: the Role of Vestibular Signals
Authors: Lopez Christophe
Published: August 2015

The role of the vestibular system in posture and eye movement control has been extensively described. By contrast, how vestibular signals contribute to bodily perceptions is a more recent research area in the field of cognitive neuroscience. In the present review article, I will summarize recent findings showing that vestibular signals play a crucial role in making sense of the body. First, data will be presented showing that vestibular signals contribute to bodily perceptions ranging from low-level bodily perceptions, such as touch, pain, and the processing of the body’s metric properties, to higher level bodily perceptions, such as the sense of owning a body, the sense of being located within this body (embodiment), and the anchoring of the visuo-spatial perspective to this body. In the second part of the review article, I will show that vestibular information seems to be crucially involved in the visual perception of biological motion and in the visual perception of human body structure. Reciprocally, observing human bodies in motion influences vestibular self-motion perception, presumably due to sensorimotor resonance between the self and others. I will argue that recent advances in the mapping of the human vestibular cortex afford neuroscientific models of the vestibular contributions to human bodily self-consciousness.
The Moving History of Vestibular Stimulation as a Therapeutic Intervention
Authors: Grabherr Luzia , Macauda Gianluca , Lenggenhager Bigna
Published: August 2015

Although the discovery and understanding of the function of the vestibular system date back only to the 19th century, strategies that involve vestibular stimulation were used long before to calm, soothe and even cure people. While such stimulation was classically achieved with various motion devices, like Cox’s chair or Hallaran’s swing, the development of caloric and galvanic vestibular stimulation has opened up new possibilities in the 20th century. With the increasing knowledge and recognition of vestibular contributions to various perceptual, motor, cognitive, and emotional processes, vestibular stimulation has been suggested as a powerful and non-invasive treatment for a range of psychiatric, neurological and neurodevelopmental conditions. Yet, the therapeutic interventions were, and still are, often not hypothesis-driven as broader theories remain scarce and underlying neurophysiological mechanisms are often vague. We aim to critically review the literature on vestibular stimulation as a form of therapy in various selected disorders and present its successes, expectations, and drawbacks from a historical perspective.
Prediction in the Vestibular Control of Arm Movements
Authors: Blouin Jean , Bresciani Jean-Pierre , Guillaud Etienne , Simoneau Martin
Published: August 2015

The contribution of vestibular signals to motor control has been evidenced in postural, locomotor, and oculomotor studies. Here, we review studies showing that vestibular information also contributes to the control of arm movements during whole-body motion. The data reviewed suggest that vestibular information is used by the arm motor system to maintain the initial hand position or the planned hand trajectory unaltered during body motion. This requires integration of vestibular and cervical inputs to determine the trunk motion dynamics. These studies further suggest that the vestibular control of arm movement relies on rapid and efficient vestibulomotor transformations that cannot be considered automatic. We also reviewed evidence suggesting that the vestibular afferents can be used by the brain to predict and counteract body-rotation-induced torques (e.g., Coriolis) acting on the arm when reaching for a target while turning the trunk.
Internal Models, Vestibular Cognition, and Mental Imagery: Conceptual Considerations
Authors: Mast Fred W. , Ellis Andrew W.
Published: August 2015

Vestibular cognition has recently gained attention. Despite numerous experimental and clinical demonstrations, it is not yet clear what vestibular cognition really is. For future research in vestibular cognition, adopting a computational approach will make it easier to explore the underlying mechanisms. Indeed, most modeling approaches in vestibular science include a top-down ora prioricomponent. We review recent Bayesian optimal observer models, and discuss in detail the conceptual value of prior assumptions, likelihood and posterior estimates for research in vestibular cognition. We then consider forward models in vestibular processing, which are required in order to distinguish between sensory input that is induced by active self-motion, and sensory input that is due to passive self-motion. We suggest that forward models are used not only in the service of estimating sensory states but they can also be drawn upon in an offline mode (e.g., spatial perspective transformations), in which interaction with sensory input is not desired. A computational approach to vestibular cognition will help to discover connections across studies, and it will provide a more coherent framework for investigating vestibular cognition.