bluuebunny/crossref_metadata_2025 huggingface dataset:
Naïve optimality: Subjects' heuristics can be better motivated than experimenters' optimal models
Authors: Nelson Jonathan D.
Published: July 2013

Is human cognition best described by optimal models, or by adaptive but suboptimal heuristic strategies? It is frequently hard to identify which theoretical model is normatively best justified. In the context of information search, naïve subjects' heuristic strategies are better motivated than some “optimal” models.
On is an ought: Levels of analysis and the descriptive versus normative analysis of human reasoning
Authors: Schroyens Walter
Published: July 2013

Algorithmic-level specifications carry part of the explanatory burden in most psychological theories. It is, thus, inappropriate to limit a comparison and evaluation of theories to the computational level. A rational analysis considers people's goal-directed and environmentally adaptive rationality; it is not normative. Adaptive rationality is by definition non-absolute; hence, neither deductive logic nor Bayesian probability theory has absolute normative status.
p-adic L-functions over the false Tate curve extensions
Authors: KIM DOHYEONG
Published: July 2013

Let f be a primitive modular form of CM type of weight k and level Γ0(N). Let p be an odd prime which does not divide N, and for which f is ordinary. Our aim is to p-adically interpolate suitably normalized versions of the critical values L(f, ρχ,n), where n=1,2,. . .,k − 1, ρ is a fixed self-dual Artin representation of M∞ defined by (1.1) below, and χ runs over the irreducible Artin representations of the Galois group of the cyclotomic $\mathbb{Z}_p$-extension of $\mathbb{Q}$. As an application, if k ≥ 4, we will show that there are only finitely many χ such that L(f, ρχ,k/2)=0, generalizing a result of David Rohrlich. Also, we conditionally establish a congruence predicted by non-commutative Iwasawa theory and give numerical evidence for it.
Education and Training of Hospital Workers: Who Are Essential Personnel during a Disaster?
Authors: Reilly Michael , Markenson David S.
Published: July 2013

Hospital plans often vary when it comes to the specific functional roles that are included in emergency and incident management positions.Bioterrorism coordinators and emergency managers for 31 hospitals in a seven-county region outside of a major metropolitan area, with urban, suburban, and rural demographics were surveyed to determine which specific functional roles were considered “essential” to their hospital's emergency operations plans. Furthermore, they were asked to estimate the percentage of their “essential” staff trained to perform the functional roles delineated in the hospital's plan. Responses were entered into a database and descriptive statistical computations were performed. Only three categories of hospital personnel were reported to be “essential” by all hospitals to their emergency preparedness plans: emergency department physicians, nurse, and support staff. Training for overall “essential” staff ranged by hospital 73.6–83.3%. Some hospitals reported that these staff members have received no training in their anticipated role based on the hospital emergency response plan. Allied health professionals and emergency medical technicians/paramedics (that are employed by hospitals) had the least amount of training on their role in the hospital preparedness and response plan, 33.3% and 22.2% respectively.Without improved guidance on benchmarks for preparedness from regulators and professional organizations, hospitals will continue to lack the capacity to effectively respond to disasters and public health emergencies.
Curious Lexicographic Relic of the Cultural Revolution
Authors: BRANNER DAVID PRAGER , MENG YUAN-YUAN
Published: July 2013

This paper considers the fact that many verbal Chinese idioms are defined in recent Chinese-English dictionaries with misleading parts of speech — they are generally described only as being nouns. This situation originates in the 1978 Hàn-Yīng cídiǎn 汉英词典 of Wú Jǐngróng 吴景荣, whose definitions have exerted overwhelming influence on the field since then. We document Wú's principal sources and the viewpoints that motivated him, including the heavy political pressure to which his lexicographic team were subjected in the late Cultural Revolution. In addition, we consider Wú's anomalous misreading of the purpose of the influential Giles and Mathews dictionaries, which had been to document the many senses of each character with multi-character words, rather than to document multi-character words per se.
Can a questionnaire predict vitamin D status in postmenopausal women?
Authors: Nabak Andrea C , Johnson Rachael Erin , Keuler Nicholas S , Hansen Karen E
Published: July 2013

Objective

Our objective was to determine whether a questionnaire can identify individuals with vitamin D insufficiency (VDI).

Design

Women completed the Vitamin D & Sun (VIDSUN) questionnaire and we measured their serum 25-hydrocyvitamin D (25(OH)D) levels. We assessed the sensitivity and specificity of the questionnaire to identify VDI (25(OH)D level <50 nmol/l).

Setting

Clinical Research Unit, University of Wisconsin–Madison.

Subjects

Postmenopausal women.

Results

We recruited 609 postmenopausal women with a mean age of 61 (sd 6 years), of whom 113 (19 %) had VDI. Women with VDI were more likely to be black (17 % v. 2 %, P < 0·001), heavier (BMI 33·0 (sd 7) kg/m2v. 29·0 (sd 7) kg/m2, P < 0·001) and less likely to tan in the past year (49 % v. 72 %, P < 0·001), use sunscreen (57 % v. 72 %, P < 0·001) or report sun exposure in the last 3 months. They consumed less vitamin D from supplements (2·15 (sd 5·24) μg/d (86 (sd 210) IU/d) v. 4·55 (sd 8·48) μg/d (188 (sd 344) IU/d), P = 0·003). In logistic regression models, black race, BMI, suntan within the past year, sun exposure in the past 3 months, sunscreen use and supplemental vitamin D intake were the most useful questions to identify VDI. From these six items, a composite score of ≤2·25 demonstrated ≥89 % sensitivity but ≤35 % specificity for VDI.

Conclusions

The VIDSUN questionnaire provides an initial tool to identify postmenopausal women at high or low risk of VDI. Existing studies suggest that inclusion of physical activity and TAG levels might improve the performance of the VIDSUN questionnaire.
‘I mean, obviously you're using your discretion’: Nurses Use of Discretion in Policy Implementation
Authors: Hoyle Louise
Published: July 2013

This article explores the application of Lipsky's (1980) notion of street-level bureaucracy for nursing staff. This article aims to demonstrate the importance of discretion within the day-to-day work of front-line nursing staff, which is similar to that of other public-sector workers. The findings are from an exploratory case study based within a Scottish inner-city hospital. It specifically focuses on how nurses can be seen to be street-level bureaucrats and how front-line nursing staff interpret policy. Discretion can be seen to be a significant feature within the front-line practice of nursing staff and this may have implications for the implementation of health policy.
AN ARGUMENT FOR CONJUNCTION CONDITIONALIZATION
Authors: WALTERS LEE , WILLIAMS J. ROBERT G.
Published: July 2013

Are counterfactuals with true antecedents and consequents automatically true? That is, is Conjunction Conditionalization: (X ∧ Y) ⊃ (X > Y) valid? Stalnaker and Lewis think so, but many others disagree. We note here that the extant arguments for Conjunction Conditionalization are unpersuasive, before presenting a family of more compelling arguments. These arguments rely on some standard theorems of the logic of counterfactuals as well as a plausible and popular semantic claim about certain semifactuals. Denying Conjunction Conditionalization, then, requires rejecting other aspects of the standard logic of counterfactuals or else our intuitive picture of semifactuals.
The potential role of the Antarctic Ice Sheet in global biogeochemical cycles
Authors: Wadham J. L. , De'ath R. , Monteiro F. M. , Tranter M. , Ridgwell A. , Raiswell R. , Tulaczyk S.
Published: July 2013

Once thought to be devoid of life, the Antarctic Ice Sheet is now known to be a dynamic reservoir of organic carbon and metabolically active microbial cells. At the ice-bed interface, subglacial lake and sedimentary environments support low diversity microbial populations, adapted to perennial cold, anoxia and lack of light. The dynamic exchange of water between these shallow environments conveys meltwaters and associated sediments into the coastal ocean. This, together with the release of iceberg-rafted debris to more distal coastal environments, could be important for sustaining primary productivity in the iron-limited Southern Ocean, via the release of associated nutrients and bioavailable iron. We estimate the magnitude and review the wider impacts of the potential export of nutrients (N, P, C, Si and bioavailable Fe) dissolved and associated with suspended sediments in Antarctic runoff and entombed in iceberg rafted debris. Located beneath subglacial lakes and the subglacial till complex are deep sedimentary basins up to 14 km thick, located largely around the Antarctic periphery. These sedimentary basins are largely hydrologically decoupled from shallower lake and till environments by the presence of highly consolidated sediments which limit the penetration of glacial meltwaters to depth. They provide extensive habitats for sustained microbial activity over Ma timescales, and are likely to be a focal point for the anaerobic cycling of organic carbon and other elements in the deep sub-surface. Organic carbon buried in these basins during ice sheet formation is thought to be microbially cycled to methane gas, and the methane largely stored as hydrate within sediments, stabilised by the high pressure/low temperature conditions. We conclude that the export of nutrients and biogenic gases from deep and shallow subglacial Antarctic environments designates Antarctica as a potentially important component of the Earth's carbon cycle, and highlight the importance of evaluating these potential impacts further via global and regional-scale biogeochemical modelling.
Platelet-activating factor synthesis and receptor-mediated signaling are downregulated in ovine newborn lungs: relevance in postnatal pulmonary adaptation and persistent pulmonary hypertension of the newborn
Authors: Renteria L. S. , Cruz E. , Ibe B. O.
Published: July 2013

Platelet-activating factor (PAF) is a phospholipid with a wide range of biological activities. We studied PAF metabolism and PAF receptor (PAFR) signaling in perinatal ovine lungs to understand PAF's role in transition of the perinatal pulmonary hemodynamics and pathophysiology of persistent pulmonary hypertension of the newborn. We hypothesized that downregulation of PAF synthesis with upregulation of PAF catabolism by acetylhydrolase (PAF-Ah) in the newborn lung is needed for fetus-to-newborn pulmonary adaptation. Studies were conducted on fetal and newborn lamb pulmonary arteries (PA), veins (PV) and smooth muscle cells (SMC). PAF metabolism, PAFR binding and cell proliferation were studied by cell culture; gene expression was studied by qPCR. Fetal lungs synthesized 60% more PAF than newborn lungs. Compared with the fetal PVs and SMCs, PAF-Ah activity in newborn was 40–60% greater. PAF-Ah mRNA expression in newborn vessels was different from the expression by fetal PA. PAF-Ah gene clone activity confirmed deletion of hypoxia-sensitive site. PAFR mRNA expression by the PVs and SMC-PV of the fetus and newborn was greater than by corresponding PAs and SMC-PA. Q-PCR study of PAFR expression by the SMC-PV of both groups was greater than SMC-PA. Fetal SMCs bound more PAF than the newborn SMCs. PAFR antagonist, CV-3988, inhibited PAFR binding and DNA synthesis by the fetal SMCs, but augmented binding and DNA synthesis by newborn cells. We show different PAF–PAFR mediated effects in perinatal lungs, suggesting both transcriptional and translational regulation of PAF-Ah and PAFR expression in the perinatal lamb lungs. These indicate that the downregulation of PAF-mediated effects postnatally protects against persistent pulmonary hypertension of the newborn.
High arsenic in rice is associated with elevated genotoxic effects in humans
Authors: Banerjee Mayukh , Banerjee Nilanjana , Bhattacharjee Pritha , Mondal Debapriya , Lythgoe Paul R. , Martínez Mario , Pan Jianxin , Polya David A. , Giri Ashok K.
Published: July 2013

Arsenic in drinking water may cause major deleterious health impacts including death. Although arsenic in rice has recently been demonstrated to be a potential exposure route for humans, there has been to date no direct evidence for the impact of such exposure on human health. Here we show for the first time, through a cohort study in West Bengal, India, involving over 400 human subjects not otherwise significantly exposed to arsenic through drinking water, elevated genotoxic effects, as measured by micronuclei (MN) in urothelial cells, associated with the staple consumption of cooked rice with >200 μg/kg arsenic. Further work is required to determine the applicability to populations with different dietary and genetic characteristics, but with over 3 billion people in the world consuming rice as a staple food and several percent of this rice containing such elevated arsenic concentrations, this study raises considerable concerns over the threat to human health.
Time-resolved dynamics of granular matter by random laser emission
Authors: Folli Viola , Ghofraniha Neda , Puglisi Andrea , Leuzzi Luca , Conti Claudio
Published: July 2013

Because of the huge commercial importance of granular systems, the second-most used material in industry after water, intersecting the industry in multiple trades, like pharmacy and agriculture, fundamental research on grain-like materials has received an increasing amount of attention in the last decades. In photonics, the applications of granular materials have been only marginally investigated. We report the first phase-diagram of a granular as obtained by laser emission. The dynamics of vertically-oscillated granular in a liquid solution in a three-dimensional container is investigated by employing its random laser emission. The granular motion is function of the frequency and amplitude of the mechanical solicitation, we show how the laser emission allows to distinguish two phases in the granular and analyze its spectral distribution. This constitutes a fundamental step in the field of granulars and gives a clear evidence of the possible control on light-matter interaction achievable in grain-like system.
Self-assembled dextran sulphate nanoparticles for targeting rheumatoid arthritis
Authors: Kim Seol-Hee , Kim Jong-Ho , You Dong Gil , Saravanakumar Gurusamy , Yoon Hong Yeol , Choi Ki Young , Thambi Thavasyappan , Deepagan V. G. , Jo Dong-Gyu , Park Jae Hyung
Published: July 2013

Self-assembled nanoparticles, composed of hydrophilic dextran sulfate and polycaprolactone as a hydrophobic segment, have potential as nanocarriers for targeting rheumatoid arthritis.
Improving the low voltage ride through of doubly fed induction generator during intermittent voltage source converter faults
Authors: Abdou A. F. , Abu-Siada A. , Pota H. R.
Published: July 2013

The impact of different voltage source converter (VSC) faults on the low voltage ride through (LVRT) capability of the doubly fed induction generator (DFIG) is also investigated. Faults such as fire-through of the VSC switches and short circuit across the DC-link capacitor are considered in this paper. The impact of internal VSC faults when they occur within the grid side converter (GSC), and rotor side converter is investigated. A proper static synchronous compensator (STATCOM) controller to mitigate the effects of these faults is proposed. The DFIG compliance with numerous and recently released LVRT grid codes under these faults, with and without the STATCOM, is examined and compared. Simulation results indicate that these types of faults have a severe impact on the DFIG voltage profile, especially when these faults occur in the GSC. This is attributed to the fact that the GSC directly regulates the point of common coupling (PCC) voltage. Moreover, the proposed controller is capable of bringing the voltage profile at the PCC to the nominal steady state level and hence maintaining the connection of the wind turbine during the various studied faults.
Scale effects in the latent heat of melting in nanopores
Authors: Shin J.-H. , Parlange J.-Y. , Deinert M. R.
Published: July 2013

The curvature of a liquid vapor interface has long been known to change the equilibrium vapor pressure. It has also been shown that a capillary structure will affect the temperature at which both freezing and vaporization of a substance will occur. However, describing interfacial effects on the latent heat of a phase change has proven more difficult. Here, we present a classical thermodynamic model for how the latent heat of melting changes as the size of the particles undergoing the transition decreases. The scale dependence for the surface tension is taken into consideration using a Tolman length correction. The resulting model is tested by fitting to published experimental data for the latent heat of melting for benzene, heptane, naphthalene, and water contained in nano-porous glass. In all cases the model fits the data with a R2 ≥ 0.94.
Shape characteristics of equilibrium and non-equilibrium fractal clusters
Authors: Mansfield Marc L. , Douglas Jack F.
Published: July 2013

It is often difficult in practice to discriminate between equilibrium and non-equilibrium nanoparticle or colloidal-particle clusters that form through aggregation in gas or solution phases. Scattering studies often permit the determination of an apparent fractal dimension, but both equilibrium and non-equilibrium clusters in three dimensions frequently have fractal dimensions near 2, so that it is often not possible to discriminate on the basis of this geometrical property. A survey of the anisotropy of a wide variety of polymeric structures (linear and ring random and self-avoiding random walks, percolation clusters, lattice animals, diffusion-limited aggregates, and Eden clusters) based on the principal components of both the radius of gyration and electric polarizability tensor indicates, perhaps counter-intuitively, that self-similar equilibrium clusters tend to be intrinsically anisotropic at all sizes, while non-equilibrium processes such as diffusion-limited aggregation or Eden growth tend to be isotropic in the large-mass limit, providing a potential means of discriminating these clusters experimentally if anisotropy could be determined along with the fractal dimension. Equilibrium polymer structures, such as flexible polymer chains, are normally self-similar due to the existence of only a single relevant length scale, and are thus anisotropic at all length scales, while non-equilibrium polymer structures that grow irreversibly in time eventually become isotropic if there is no difference in the average growth rates in different directions. There is apparently no proof of these general trends and little theoretical insight into what controls the universal anisotropy in equilibrium polymer structures of various kinds. This is an obvious topic of theoretical investigation, as well as a matter of practical interest. To address this general problem, we consider two experimentally accessible ratios, one between the hydrodynamic and gyration radii, the other between the viscosity and hydrodynamic radii, as potential measures of shape anisotropy. We also find a strong correlation between anisotropy and effective fractal dimension. These observations should provide new practical methods for quantifying the nature of particle clustering in diverse contexts.
Magnetic hollow cages with colossal moments
Authors: Wu Menghao , Jena Puru
Published: July 2013

A comprehensive study of the interaction of transition metal clusters with B, C, N, O, and Si reveal novel structure and properties: Co12C6, Mn12C6, and Mn24C18 clusters form stable ferromagnetic hollow cages with total magnetic moments of 14 μB, 38 μB, and 70 μB, respectively. Replacement of C with B, N, O, or Si has significant impact on their structure and magnetic properties. For example, Mn20Si12 cluster forms a ferrimagnetic dodecahedral hollow cage with a total magnetic moment of 36 μB while Mn12N6, X12C6 (X = Ni, Cu, Pd, Pt), and Cu12O6 possess no magnetic moment, although they retain hollow cage structures. Mn12B6 and Mn24Si18, on the other hand, form compact ferrimagnetic structures. Synthesis of hollow cage clusters with unique magnetic properties may lead to important applications.
Diesel-solar electricity supply for remote monasteries
Authors: Nikolić Zoran , Shiljkut Vladimir M. , Nikolić Dušan
Published: July 2013

This paper proposes a hybrid autonomous electricity supply system for monasteries as a specific type of load. Chilandar monastery (Mount Athos, Greece) was presented as a case study. Taking into consideration specific location, historical significance, present and future needs of the monastery, and peculiar life style of its inhabitants, a new hybrid system for 400 kWh daily energy consumption and 80 kW peak load have been designed, proposed and elaborated here. It is based on combined use of three new diesel aggregates and a field of photovoltaic panels. Paper further outlines the methodology for selection and sizing up of power generating sources and other equipment. The primary goal for the new system was the reduction of diesel fuel and operational costs. Finally, cost-benefit analysis results of the proposed hybrid system are presented as well.
Investigations of droplet movement excited by Lamb waves on a non-piezoelectric substrate
Authors: Liang Wei , Lindner Gerhard
Published: July 2013

A model for the numerical simulation of the movement of liquid droplets excited by Lamb waves propagating on non-piezoelectric substrates was developed, and the results of simulation calculations based on this model were compared with experimental observations. In the experiments antisymmetrical zero order Lamb waves with 1 MHz center frequency were excited on a 1 mm thick glass substrate by piezoelectric single phase transducers, which caused the propulsion of microliter water droplets. The acoustic streaming within the droplet was calculated by solving the incompressible Navier-Stokes equations with an inhomogeneous acoustic streaming force field. These calculations were validated by optical measurements of the streaming effects in the droplet and by measurements of the displacement amplitudes of the Lamb waves with a laser-Doppler-vibrometer. Another part of the numerical simulations was related to the transient motion of acoustically driven droplets by solving the incompressible Navier-Stokes equations using the moving mesh application mode of the comsol software including a weak formulation for the calculation of the surface tension. The corresponding measurements with a high-speed camera revealed a silkworm-like movement of the droplet resulting from the interaction with acoustic force, surface tension, gravity, and inertial force, which was reproduced by the numerical simulations.
Observation of nanophase segregation in LiCl aqueous solutions from transient grating experiments
Authors: Bove L. E. , Dreyfus C. , Torre R. , Pick R. M.
Published: July 2013

Transient grating experiments performed on supercooled LiCl, RH2O solutions with R > 6 reveal the existence of well resolved, short time, extra signal which superposes to the normal signal observed for the R = 6 solution and for homogenous glass forming systems. This extra signal shows up below 190 K, its shape and the associated timescale depend only on temperature, while its intensity increases with R. We show that the origin of this signal is a phase separation between clusters with a low solute concentration and the remaining, more concentrated, solution. Our analysis demonstrates that these clusters have a nanometer size and a composition which are rather temperature independent, while increasing R simply increases the density of these clusters.
Subsingular vectors in Verma modules, and tensor product of weight modules over the twisted Heisenberg-Virasoro algebra and W(2, 2) algebra
Authors: Radobolja Gordan
Published: July 2013

We show that subsingular vectors may exist in Verma modules over W(2, 2), and present the subquotient structure of these modules. We prove conditions for irreducibility of the tensor product of intermediate series module with a highest weight module. Relation to intertwining operators over vertex operator algebra associated with W(2, 2) is discussed. Also, we study the tensor product of intermediate series and a highest weight module over the twisted Heisenberg-Virasoro algebra, and present series of irreducible modules with infinite-dimensional weight spaces.
Effect of surface tension on electrocaloric effects in the ferroelectric nanomaterial with vortex domain structures
Authors: Li B. , Wang J. B. , Zhong X. L. , Wang F. , Wang L. J. , Zhou Y. C.
Published: July 2013

The influence of intrinsic surface tension on the electrocaloric effect (ECE) in the ferroelectric nanomaterial with vortex domain structures is studied by using the phase field method. The calculation results show that a giant adiabatic temperature change (ΔT = 5.8 K) related to the toroidal moment change appears in the PbTiO3 (PTO) ferroelectric nanoparticle with the surface tension coefficient μ = 5 N/m under the vorticity vector of curled electric field (Q1 = 0 mV/Å2, ΔQ1 = 0.9 mV/Å2) at room temperature. The magnitude of the adiabatic temperature change decreases with the increase in surface tension. The decrease in size is found to enhance the ECE of PTO nanoparticle with vortex domain structures when the surface tension is not considered.
A period-doubling cascade precedes chaos for planar maps
Authors: Sander Evelyn , Yorke James A.
Published: July 2013

A period-doubling cascade is often seen in numerical studies of those smooth (one-parameter families of) maps for which as the parameter is varied, the map transitions from one without chaos to one with chaos. Our emphasis in this paper is on establishing the existence of such a cascade for many maps with phase space dimension 2. We use continuation methods to show the following: under certain general assumptions, if at one parameter there are only finitely many periodic orbits, and at another parameter value there is chaos, then between those two parameter values there must be a cascade. We investigate only families that are generic in the sense that all periodic orbit bifurcations are generic. Our method of proof in showing there is one cascade is to show there must be infinitely many cascades. We discuss in detail two-dimensional families like those which arise as a time-2π maps for the Duffing equation and the forced damped pendulum equation.
A versatile ultra high vacuum sample stage with six degrees of freedom
Authors: Ellis A. W. , Tromp R. M.
Published: July 2013

We describe the design and practical realization of a versatile sample stage with six degrees of freedom. The stage was designed for use in a Low Energy Electron Microscope, but its basic design features will be useful for numerous other applications. The degrees of freedom are X, Y, and Z, two tilts, and azimuth. All motions are actuated in an ultrahigh vacuum base pressure environment by piezoelectric transducers with integrated position sensors. The sample can be load-locked. During observation, the sample is held at a potential of −15 kV, at temperatures between room temperature and 1500 °C, and in background gas pressures up to 1 × 10−4 Torr.
Spatial and temporal scales of force and torque acting on wall-mounted spherical particles in open channel flow
Authors: Chan-Braun C. , García-Villalba M. , Uhlmann M.
Published: July 2013

Data from direct numerical simulation of open channel flow over a geometrically rough wall at a bulk Reynolds number of Reb = 2900, generated by Chan-Braun et al. [“Force and torque acting on particles in a transitionally rough open-channel flow,” J. Fluid Mech. 684, 441–474 (2011)]10.1017/jfm.2011.311 are further analysed with respect to the time and length scales of force and torque acting on the wall-mounted spheres. For the two sizes of spheres in a square arrangement (11 and 49 wall units in diameter, yielding hydraulically smooth and transitionally rough flow, respectively), the spatial structure of drag, lift, and spanwise torque is investigated. The auto-correlation and spectra in time as well as the space-time correlation and convection velocities are presented and discussed. It is found that the statistics of spanwise particle torque are similar to those of shear stress at a smooth wall. Particle drag and lift are shown to differ from spanwise particle torque, exhibiting considerably smaller time and length scales; the convection velocities of drag and lift are somewhat larger than those of spanwise torque. Furthermore, correlations between the flow field and particle-related quantities are presented. The spatial structure of the correlation between streamwise velocity and drag/spanwise torque features elongated shapes reminiscent of buffer-layer streaks. The correlation between the pressure field and the particle drag exhibits two opposite-signed bulges on the upstream and downstream sides of a particle.
A skin friction model for axisymmetric turbulent boundary layers along long thin circular cylinders
Authors: Jordan Stephen A.
Published: July 2013

Only a few engineering design models are presently available that adequately depict the axisymmetric skin friction (Cf) maturity along long thin turbulent cylinders. This deficit rests essentially on the experimental and numerical difficulties of measuring (or computing) the spatial evolution of the thin cylinder turbulence. Consequently, the present axisymmetric Cf models have questionable accuracy. Herein, we attempt to formulate a more robust Cf model that owns acceptable error. The formulation is founded on triple integration of the governing equation system that represents a thin cylinder turbulent boundary layer (TBL) at statistical steady-state in appropriate dimensionless units. The final model requires only the radius-based Reynolds number (Rea) and transverse curvature (δ/a) as input parameters. We tuned the accompanying coefficients empirically via an expanded statistical database (over 60 data points) that house new Cf values from large-eddy simulations (LES). The LES computations employed a turbulence inflow generation procedure that permits spatial resolution of the TBL at low-high Reynolds numbers and transverse curvatures. Compared to the new skin friction database, the Cf model revealed averaged predictive errors under 5% with a 3.5% standard deviation. Apart from owning higher values than the flat plate TBL, the most distinguishing characteristic of the axisymmetric skin friction is its rising levels when the boundary layer thickness exceeds the cylinder radius. All Cf levels diminish with increasing Reynolds number. These unique features differentiate the axisymmetric TBL along thin cylinders as a separate canonical flow when compared to the turbulent wall shear-layers of channels, pipes, and planar-type geometries.
Nonlinear fluid-structure interaction of an elastic panel in an acoustically excited two-dimensional inviscid compressible fluid
Authors: Aginsky Z. , Gottlieb O.
Published: July 2013

The focus of this paper is on the asymptotic investigation of the nonlinear fluid-structure interaction of an acoustically excited clamped panel immersed in an inviscid compressible fluid. A multiple-scales analysis of the corresponding two-dimensional unsteady potential flow initial-boundary-value-problem is employed to investigate both primary resonance and a 3:1 internal resonance between the panel fifth and ninth modes. Validation of the asymptotic structural response and the fluid pressure shows good agreement with numerical solution of a weakly nonlinear panel in a quadratic Euler field. The results shed light on the intricate acoustic interaction bifurcation structure which exhibits coexisting bi-stable periodic solutions, and quasiperiodic response reflecting spatially periodic modal energy transfer for both panel and fluid. This behavior is found to occur for panel excitation by finite level acoustic pressure waves that can be a crucial factor for design of high integrity structural systems required for aviation or space where light structures are exposed to intensive acoustic pressure fluctuations.
Plane Couette-Poiseuille flow past a homogeneous poroelastic layer
Authors: Alexiou Terpsichori S. , Kapellos George E.
Published: July 2013

An analytical solution is presented for the problem of fully developed plane Couette-Poiseuille flow past a homogeneous, permeable poroelastic layer. Main novel feature of this work is that the compressibility, which is related to the action of the free-fluid pressure on the poroelastic layer, is taken into account. Therefore, the solid stress problem is two-dimensional, although the fluid flow problem remains one-dimensional in the limit of infinitesimal strain. The pressure-related compressibility affects strongly the distribution of the von Mises stress in the poroelastic layer by shifting the local maximum towards the high-pressure region of the channel. Furthermore, the established analytical solution is used to investigate some aspects of the mechanotransducing role of the endothelial surface layer. A compressible surface layer might serve as a “bumper’’ by reducing the magnitude of the overall shearing force (viscous and elastic) acting on endothelial cells, as compared to the magnitude of the fluid shear force that would be exerted in its absence.
Design principles for HgTe based topological insulator devices
Authors: Sengupta Parijat , Kubis Tillmann , Tan Yaohua , Povolotskyi Michael , Klimeck Gerhard
Published: July 2013

The topological insulator properties of CdTe/HgTe/CdTe quantum wells are theoretically studied. The CdTe/HgTe/CdTe quantum well behaves as a topological insulator beyond a critical well width dimension. It is shown that if the barrier (CdTe) and well-region (HgTe) are altered by replacing them with the alloy CdxHg1−xTe of various stoichiometries, the critical width can be changed. The critical quantum well width is shown to depend on temperature, applied stress, growth directions, and external electric fields. Based on these results, a novel device concept is proposed that allows to switch between a normal semiconducting and topological insulator state through application of moderate external electric fields.
Length scales and interfacial potentials in ion hydration
Authors: Shi Yu , Beck Thomas L.
Published: July 2013

The Quasichemical Theory (QCT) involves a length-scale organization of solvation thermodynamics. The QCT has been employed in studies of solutes ranging in size from small molecules and ions to proteins. There are three contributions to the QCT free energy: (1) an inner-shell term that includes the direct solute-solvent chemical interactions, (2) an outer-shell packing term that is the free energy to dig out a cavity in the solvent, and (3) an outer-shell long-ranged term that includes all interactions of the solute with the solvent conditional on an empty inner shell. The present study utilizes a regularizing generalization of the QCT and classical simulations to compute these three contributions to the ion hydration free energy out to large cavity radii for eight ions in the alkali halide series. The accuracy of simple approximations for the long-ranged term is also examined. The inner-shell contribution exhibits ion specificity for cavity sizes less than 4–5 Å, followed by a common length scale of 6.15 Å at which its value equals the bulk hydration free energy for all eight of the ions. The 6.15 Å length scale is closely approximated by the distance at which the revised scaled-particle theory packing contribution matches the magnitude of a simple Born estimate for the long-ranged term.
NAIS: Nuclear activation-based imaging spectroscopy
Authors: Günther M. M. , Britz A. , Clarke R. J. , Harres K. , Hoffmeister G. , Nürnberg F. , Otten A. , Pelka A. , Roth M. , Vogt K.
Published: July 2013

In recent years, the development of high power laser systems led to focussed intensities of more than 1022 W/cm2 at high pulse energies. Furthermore, both, the advanced high power lasers and the development of sophisticated laser particle acceleration mechanisms facilitate the generation of high energetic particle beams at high fluxes. The challenge of imaging detector systems is to acquire the properties of the high flux beam spatially and spectrally resolved. The limitations of most detector systems are saturation effects. These conventional detectors are based on scintillators, semiconductors, or radiation sensitive films. We present a nuclear activation-based imaging spectroscopy method, which is called NAIS, for the characterization of laser accelerated proton beams. The offline detector system is a combination of stacked metal foils and imaging plates (IP). After the irradiation of the stacked foils they become activated by nuclear reactions, emitting gamma decay radiation. In the next step, an autoradiography of the activated foils using IPs and an analysis routine lead to a spectrally and spatially resolved beam profile. In addition, we present an absolute calibration method for IPs.
A new direct absorption tunable diode laser spectrometer for high precision measurement of water vapor in the upper troposphere and lower stratosphere
Authors: Sargent M. R. , Sayres D. S. , Smith J. B. , Witinski M. , Allen N. T. , Demusz J. N. , Rivero M. , Tuozzolo C. , Anderson J. G.
Published: July 2013

We present a new instrument for the measurement of water vapor in the upper troposphere and lower stratosphere (UT/LS), the Harvard Herriott Hygrometer (HHH). HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell. The direct absorption technique provides a direct link between the depth of the observed absorption line and the measured water vapor concentration, which is calculated based on spectroscopic parameters in the HITRAN database. While several other tunable diode laser (TDL) instruments have been used to measure water vapor in the UT/LS, HHH is set apart by its use of an optical cell an order of magnitude smaller than those of other direct absorption TDLs in operation, allowing for a more compact, lightweight instrument. HHH is also unique in its integration into a common duct with the Harvard Lyman-α hygrometer, an independent photo-fragment fluorescence instrument which has been thoroughly validated over 19 years of flight measurements. The instrument was flown for the first time in the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) on NASA's WB-57 aircraft in spring, 2011, during which it demonstrated in-flight precision of 0.1 ppmv (1 s) with 1-sigma uncertainty of 5% ± 0.7 ppmv. Since the campaign, changes to the instrument have lead to improved accuracy of 5% ± 0.2 ppmv as demonstrated in the laboratory. During MACPEX, HHH successfully measured water vapor at concentrations from 3.5 to 600 ppmv in the upper troposphere and lower stratosphere. HHH and Lyman-α, measuring independently but under the same sampling conditions, agreed on average to within 1% at water vapor mixing ratios above 20 ppmv and to within 0.3 ppmv at lower mixing ratios. HHH also agreed with a number of other in situ water vapor instruments on the WB-57 to within their stated uncertainties, and to within 0.7 ppmv at low water. This agreement constitutes a significant improvement over past in situ comparisons, in which differences of 1.5–2 ppmv were routinely observed, and demonstrates that the accuracy of HHH is consistent with other instruments which use a range of detection methods and sampling techniques.
An accurate online calibration system based on combined clamp-shape coil for high voltage electronic current transformers
Authors: Li Zhen-hua , Li Hong-bin , Zhang Zhi
Published: July 2013

Electronic transformers are widely used in power systems because of their wide bandwidth and good transient performance. However, as an emerging technology, the failure rate of electronic transformers is higher than that of traditional transformers. As a result, the calibration period needs to be shortened. Traditional calibration methods require the power of transmission line be cut off, which results in complicated operation and power off loss. This paper proposes an online calibration system which can calibrate electronic current transformers without power off. In this work, the high accuracy standard current transformer and online operation method are the key techniques. Based on the clamp-shape iron-core coil and clamp-shape air-core coil, a combined clamp-shape coil is designed as the standard current transformer. By analyzing the output characteristics of the two coils, the combined clamp-shape coil can achieve verification of the accuracy. So the accuracy of the online calibration system can be guaranteed. Moreover, by employing the earth potential working method and using two insulating rods to connect the combined clamp-shape coil to the high voltage bus, the operation becomes simple and safe. Tests in China National Center for High Voltage Measurement and field experiments show that the proposed system has a high accuracy of up to 0.05 class.
Polymer translocation through a gradient channel
Authors: Zhang Shuang , Wang Chao , Sun Li-Zhen , Li Chao-Yang , Luo Meng-Bo
Published: July 2013

The translocation of polymer through a channel with a gradient interaction between the polymer and the channel is studied. The interaction is expressed by E = E0 + kx, where E0 is the initial potential energy at the entrance, x is the position of the monomer inside the channel, and k is the energy gradient. The mean first passage time τ is calculated by using Fokker-Planck equation for two cases (1) N > L and (2) N < L under the assumption that the diffusion rate D is a constant, here N is the polymer length and L is the length of channel. Results show that there is a minimum of τ at k = kc for both cases, and the value kc is dependent on E0 and driving force f. At large f, the scaling relation τ ∼ N is observed for long polymer chains. But the scaling relation is dependent on the energy gradient k for an unforced driving translocation.
Effect of disorder on carrier transport in ZnO thin films grown by atomic layer deposition at different temperatures
Authors: Saha D. , Das Amit. K. , Ajimsha R. S. , Misra P. , Kukreja L. M.
Published: July 2013

We have grown ∼200 nm thick ZnO films on (0001) sapphire substrates using atomic layer deposition at different substrate temperatures ranging from ∼150 to 350 °C. X-ray diffraction and photoluminescence spectra of these films showed that crystalline and compositional native defects were strongly dependent on the substrate temperature. Room temperature Hall measurement showed that all the films were degenerate with carrier concentration exceeding the Mott's critical density nc required for metallic conduction. The lowest value of room temperature resistivity ∼3.6 × 10−3 Ω cm was achieved for the film deposited at ∼200 °C, which had an estimated carrier concentration ∼5.7 × 1019 cm−3 and mobility ∼30 cm2/V s. The films deposited both below and above ∼200 °C showed increased resistivity and decreased mobility presumably due to the intensified defects and deteriorated crystalline quality of these films. To investigate the effect of disorder on the underlying charge transport mechanisms in these films, the electrical resistivity was measured in the temperature range of ∼4.2 to 300 K. The films grown at ∼150, 300, and 350 °C were found to be semiconducting in the entire range of the measurement temperature due to the intensified disorder which impeded the metallic transport in these films. However, the films grown at ∼200 and 250 °C showed a transition from metallic to semiconducting transport behaviour at lower temperatures due to the reduced defects and improved crystalline quality of these films. The observed semiconducting behaviour below the transition temperature for these films could be well explained by considering quantum corrections to the Boltzmann conductivity which includes the effect of disorder induced weak localization and coulomb electron-electron interactions.
Crystalline structure effect on the performance of flexible ZnO/polyimide surface acoustic wave devices
Authors: Zhou Jian , He Xingli , Jin Hao , Wang Wenbo , Feng Bin , Dong Shurong , Wang Demiao , Zou Guangyi , Luo J. K.
Published: July 2013

This paper reports the fabrication of flexible surface acoustic wave (SAW) devices on ZnO/polyimide substrates and investigation of the effects of the deposition conditions, crystal quality, and film thickness of the ZnO films on the performance of the SAW devices. The deposition pressure has a significant effect on the crystal quality of the ZnO film, and which in turn affects the transmission of the SAW devices strongly. The device performance improves greatly and is mainly attributed to the better crystal quality of the film deposited at high pressure. The performance of the SAW devices also improves significantly with increase in ZnO film thickness, owing to the reduced defects and improved piezoelectric effect for the films with large grain sizes and better crystallinity as the film thickness increases. Flexible SAW devices with a resonant frequency of 153 MHz, a phase velocity of 1836 m/s, and a coupling coefficient of 0.79% were obtained on the ZnO film of 4 μm thickness, demonstrated its great potential for applications in electronics and microsystems.
Droplet-induced deformation of a polymer microfiber
Authors: Liu Jianlin , Sun Jing , Mei Yue
Published: July 2013

Capillary force of a liquid drop embedded in a microfiber has great influence on the mechanics behavior of the microfiber. In this study, we investigated the buckling and finite deformation of a microfiber filled with a droplet. First, the critical load for the buckling of the microfiber was presented under the combined action of the surface tension and Laplace pressure. Both global buckling based on slender rod model and local buckling according to thin shell model has been considered. Then in use of the Mooney-Rivlin model, we calculated the true axial stress of the microfiber, and clearly showed that the microfiber takes a different load carrying capability due to the capillary force. These investigations emphasize the important role of capillary force in microfibers, and the conclusions hold great potentials in micro/nanotechnologies, fabrics, blood vessels, and animal/plant surfaces.
Controlled improvement in specific contact resistivity for thermoelectric materials by ion implantation
Authors: Taylor Patrick J. , Maddux Jay R. , Meissner Greg , Venkatasubramanian Rama , Bulman Gary , Pierce Jonathan , Gupta Rahul , Bierschenk Jim , Caylor Chris , D’Angelo Jonathan , Ren Zhifeng
Published: July 2013

To obtain reduced specific contact resistivity, iodine donors and silver acceptors were ion-implanted into n-type and p-type (Bi,Sb)2(Se,Te)3 materials, respectively, to achieve >10 times higher doping at the surface. Implantation into n-type materials caused the specific contact resistivity to decrease from 1.7 × 10−6 Ω cm2 to 4.5 × 10−7 Ω cm2. Implantation into p-type materials caused specific contact resistivity to decrease from 7.7 × 10−7 Ω cm2 to 2.7 × 10−7 Ω cm2. For implanted thin-film superlattices, the non-implanted values of 1.4 × 10−7 Ω cm2 and 5.3 × 10−8 Ω cm2 precipitously dropped below the detection limit after implantation, ≤10−8 Ω cm2. These reductions in specific contact resistivity are consistent with an increase in tunneling across the contact.