bluuebunny/crossref_metadata_2025 huggingface dataset:
Exceptional Integrals of a not completely Integrable Total Differential Equation
Authors: Piaggio H. T. H.
Published: May 2009

1. There are exceptional integrals of the total differential equation

in the case when it is not completely integrable, and so when the invariant

is not identically zero, which do not seem to be mentioned by any standard authorities such as Cartan, Goursat, de la Vallée Poussin, and Schouten and Kulk. These are integrals of (1) which do not reduce I to zero. They arise only when the first partial derivates of P, Q, R are not all continuous. A simple example is z = 0 as an integral of
A Minimum Problem for the Epstein Zeta-Function
Authors: Rankin R. A.
Published: May 2009

In some recent work by D. G. Kendall and the author † on the number of points of a lattice which lie in a random circle the mean value of the variance emerged as a constant multiple of the value of the Epstein zeta-functionZ(s)associated with the lattice, taken at the point s=. Because of the connexion with the problems of closest packing and covering it seemed likely that the minimum value ofZ() would be attained for the hexagonal lattice; it is the purpose of this paper to prove this and to extend the result to other real values of the variables.
The Schur Derivative of a Polynomial
Authors: Carlitz L.
Published: May 2009

For a given sequence {am} and p≠0, Schur (2) defined

In particular if p is a prime, a an integer and , then by Fermat's theorem

is integral. Schur proved that if p † a, then all the derivatives

are integral. Zorn (3) using p-adic methods proved Schur's results and also found the residue of Xm (mod pm), where and x = 1 (mod p). The writer (1) proved Zorn's congruences by elementary methods as well as certain additional results of a similar sort.
Conduction of Heat from Local Sources in a Medium Generating or Absorbing Heat
Authors: Paterson S.
Published: May 2009

An infinite or semi-infinite medium, in which heat is generated or absorbed at a rate proportional to the temperature, is placed at temperature zero in contact with a perfect conductor of finite heat capacity at a higher temperature. Expressions are derived for the subsequent behaviour in linear and spherical cases, and applications suggested.
Associated Basic Hypergeometric Series
Authors: Agarwal R. P.
Published: May 2009

The purpose of the present note is to give some interesting and simple identities connected with basic hypergeometric series of the types 2Φ1 and 3Φ2.
In situ and remote sensing signature of meddies east of the mid‐Atlantic ridge
Authors: Bashmachnikov I. , Machín F. , Mendonça A. , Martins A.
Published: May 2009

Mediterranean Water eddies (meddies) are thought to play an important climatic role. Nevertheless, their dynamics are not sufficiently known because of difficulties encountered in their observation. Though propagating below the main thermocline, a number of pieces of evidence of sea surface manifestation of meddies are collected. The present work is based on joint in situ and altimetry data analyses to prove that the meddies can be followed with remote sensing data for long periods of time. The in situ observations are based on data from an oceanographic cruise, which crossed three meddies, and reanalysis of historical data sets, including RAFOS floats paths. Suggested methodology permitted us to obtain uninterrupted tracks for several meddies for a period from several months to more than 2 years. It was found that the dynamically calm region to the north of the Azores current presents favorable conditions for meddy tracking. The meddy surface signal may become shattered and difficult to follow during interaction with a strong dynamic structures (the Azores current/surface vortexes) or peaking topography. Theoretical considerations support the observations and lead to the conclusion that the dynamic signature of meddies at the sea surface is an intrinsic property of meddy dynamics.
Behavior of iron in (Mg,Fe)SiO3 post‐perovskite assemblages at Mbar pressures
Authors: Jackson Jennifer M. , Sturhahn Wolfgang , Tschauner Oliver , Lerche Michael , Fei Yingwei
Published: May 2009

The electronic environment of the iron sites in post‐perovskite (PPv) structured (57Fe,Mg)SiO3 has been measured in‐situ at 1.12 and 1.19 Mbar at room temperature using 57Fe synchrotron Mössbauer spectroscopy. Evaluation of the time spectra reveals two distinct iron sites, which are well distinguished by their hyperfine fields. The dominant site is consistent with an Fe3+‐like site in a high spin state. The second site is characterized by a small negative isomer shift with respect to α‐iron and no quadrupole splitting, consistent with a metallic iron phase. Combined with SEM/EDS analyses of the quenched assemblage, our results are consistent with the presence of a metallic iron phase co‐existing with a ferric‐rich PPv. Such a reaction pathway may aid in our understanding of the chemical evolution of Earth's core‐mantle‐boundary region.
Cloud droplet spectral dispersion and the indirect aerosol effect: Comparison of two treatments in a GCM
Authors: Rotstayn Leon D. , Liu Yangang
Published: May 2009

Two parameterizations of cloud droplet spectral dispersion and their impact on the indirect aerosol effect are compared in a global climate model. The earlier scheme specifies β, the ratio of droplet effective radius to volume‐mean radius, in terms of N, the cloud droplet number concentration. The new scheme specifies β in terms of mean droplet mass (L/N), where L is liquid water content, to account for the effect of variations in L. For low to moderate N, the new scheme gives a stronger increase of β with increasing N than the old scheme. In a present‐climate simulation, the new scheme shows a stronger gradient between remote regions (small β) and polluted/continental regions (large β). The new scheme also offsets the first indirect aerosol forcing (ΔF) more strongly: ΔF = −0.65 W m−2 with constant β, −0.43 W m−2 with the old β, and −0.38 W m−2 with the new β.
Delivery by Caesarean section, rather than vaginal delivery, promotes hepatic steatosis in piglets
Authors: Hyde Matthew J. , Griffin Julian L. , Herrera Emilio , Byrne Christopher D. , Clarke Lynne , Kemp Paul R.
Published: May 2009

There has been a marked increase in the number of babies born by elective CS (Caesarean section). Following CS, the lack of normal stimuli that occur at birth alters the thermogeneic response, but any effects on hepatic metabolism have not been identified. In the present study, we compared the effect of delivery on hepatic metabolism in piglets, born either by CS or VD (vaginal delivery) and fed by TPN (total parenteral nutrition), by measuring lipid metabolism and enzyme activity coupled with metabolomic and genomic approaches. Hepatic lipid in the CS piglets at 7 days post-partum was in excess of 5 mg/g of liver consistent with hepatic steatosis, whereas in the VD piglets the amount of lipid was markedly lower (3 mg/g of liver) and below the threshold for a diagnosis of steatosis. Metabolomic analysis indicated that CS resulted in higher hepatic glycerol and lower glycerol phosphate dehydrogenase activity, suggesting that CS causes a decrease in hepatic gluconeogenesis from glycerol. CS also resulted in altered cholesterol handling and gene expression, despite the same dietary intake for 7 days post-partum. Furthermore, the CS piglets had a lower expression of interferon-responsive genes, but a higher expression of markers of immature hepatocytes. In conclusion, the results suggest that VD promotes normal liver maturation and hepatic metabolism, thereby reducing the accumulation of hepatic lipid.
Wine Consumers Information Search: Gender Differences and Implications for the Hospitality Industry
Authors: Barber Nelson
Published: May 2009

Marketing has always looked for new ways to sell consumer products or enhance loyalty, and in this consumer-driven economy, it is important to look for effective ways to market products. This study examines the relationship of market segmentation and consumer characteristics, in particular, product knowledge and gender differences during purchase decisions. By segmenting consumers in this manner, it is possible to better understand their concerns and motivations, which should aid wine producers and those in the hospitality industry, such as restaurants, and retailers in directing their marketing and advertising efforts. Using wine as the product for this study, the results indicate that men have greater actual and self-assessed wine knowledge compared with women. Yet, men use limited sources of information during purchase situations; thus, with the proper staff training and target marketing strategies, market share and brand loyalty could increase by focusing on men as wine consumers.
Role of zonal flows in trapped electron mode turbulence through nonlinear gyrokinetic particle and continuum simulation
Authors: Ernst D. R. , Lang J. , Nevins W. M. , Hoffman M. , Chen Y. , Dorland W. , Parker S.
Published: May 2009

Trapped electron mode (TEM) turbulence exhibits a rich variety of collisional and zonal flow physics. This work explores the parametric variation of zonal flows and underlying mechanisms through a series of linear and nonlinear gyrokinetic simulations, using both particle-in-cell and continuum methods. A new stability diagram for electron modes is presented, identifying a critical boundary at ηe=1, separating long and short wavelength TEMs. A novel parity test is used to separate TEMs from electron temperature gradient driven modes. A nonlinear scan of ηe reveals fine scale structure for ηe≳1, consistent with linear expectation. For ηe<1, zonal flows are the dominant saturation mechanism, and TEM transport is insensitive to ηe. For ηe>1, zonal flows are weak, and TEM transport falls inversely with a power law in ηe. The role of zonal flows appears to be connected to linear stability properties. Particle and continuum methods are compared in detail over a range of ηe=d ln Te/d ln ne values from zero to five. Linear growth rate spectra, transport fluxes, fluctuation wavelength spectra, zonal flow shearing spectra, and correlation lengths and times are in close agreement. In addition to identifying the critical parameter ηe for TEM zonal flows, this paper takes a challenging step in code verification, directly comparing very different methods of simulating simultaneous kinetic electron and ion dynamics in TEM turbulence.
Analysis of the vibration characteristics of fluid-conveying double-walled carbon nanotubes
Authors: Natsuki Toshiaki , Ni Qing-Qing , Endo Morinobu
Published: May 2009

Vibration characteristics of double-walled carbon nanotubes (DWCNTs) with conveying fluid are analyzed based on the Euler–Bernoulli beam theory and using the wave propagation approach. The DWCNTs are considered as two nanotube shells coupled through the van der Waals interaction between them. The influences of internal moving fluids, such as flow velocity and mass density of fluids, on the vibration frequency of DWCNTs and the DWCNTs embedded in an elastic matrix are investigated in detail. The effect of matrix surrounding carbon nanotubes is considered as a spring element defined by the Winkler model. In this paper, we consider the double-walled nanotubes with an inner diameter of 2.2 nm and an outer diameter of 3.0 nm. According to this analysis, the numerical results indicate that the vibration frequency for the first mode (mode 1) reduces to zero at a critical flow velocity in the case of higher flow velocity, which coincides with the previous study based on a single beam model. The critical flow velocity is largely affected by the fluid properties and the vibration modes.
Plasma torque and nonambipolar transport
Authors: Boozer Allen H.
Published: May 2009

Poloidal symmetry breaking in toroidal plasmas causes a damping of poloidal rotation and toroidal symmetry breaking a damping of toroidal rotation. These torques are transmitted by the magnetic field to the outside world. An upper limit exists on the torque that can be transmitted by magnetic asymmetries. This limit is enforced by shielding asymmetries from the plasma, which can be an important effect for toroidal asymmetries. The torque interaction of plasmas with magnetic fields can be either through an anisotropic pressure or by the drive for magnetic islands. The physics of both types of interactions are considered and paradoxical effects are clarified.
A broadband continuous-wave multichannel near-infrared system for measuring regional cerebral blood flow and oxygen consumption in newborn piglets
Authors: Diop Mamadou , Elliott Jonathan T. , Tichauer Kenneth M. , Lee Ting-Yim , St. Lawrence Keith
Published: May 2009

Near-infrared spectroscopy (NIRS) is a promising technique for assessing brain function in newborns, particularly due to its portability and sensitivity to cerebral hemodynamics and oxygenation. Methods for measuring cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) have been developed based on broadband continuous-wave NIRS. However, broadband NIRS apparatus typically have only one detection channel, which limits their applicability to measuring regional CBF and CMRO2. In this study, a relatively simple multiplexing approach based on electronically controlled mechanical shutters is proposed to expand the detection capabilities from one to eight channels. The tradeoff is an increase in the sampling interval; however, this has negligible effects on CBF measurements for intervals less than or equal to 1 s. The ability of the system to detect focal brain injury was demonstrated in piglets by injecting endothelin-1 (ET-1) into the cerebral cortex. For validation, CBF was independently measured by computed tomography (CT) perfusion. The average reduction in CBF from the source-detector pair that interrogated the injured region was 51%±9%, which was in good agreement with the CBF reduction measured by CT perfusion (55%±5%). No significant changes in regional CMRO2 were observed. The average regional differential pathlength prior to ET-1 injection was 8.4±0.2 cm (range of 7.1–9.6 cm) and did not significantly change after the injury.
Gravity-driven slug motion in capillary tubes
Authors: Lunati Ivan , Or Dani
Published: May 2009

The velocity of a liquid slug falling in a capillary tube is lower than predicted for Poiseuille flow due to presence of menisci, whose shapes are determined by the complex interplay of capillary, viscous, and gravitational forces. Due to the presence of menisci, a capillary pressure proportional to surface curvature acts on the slug and streamlines are bent close to the interface, resulting in enhanced viscous dissipation at the wedges. To determine the origin of drag-force increase relative to Poiseuille flow, we compute the force resultant acting on the slug by integrating Navier–Stokes equations over the liquid volume. Invoking relationships from differential geometry we demonstrate that the additional drag is due to viscous forces only and that no capillary drag of hydrodynamic origin exists (i.e., due to hydrodynamic deformation of the interface). Requiring that the force resultant is zero, we derive scaling laws for the steady velocity in the limit of small capillary numbers by estimating the leading order viscous dissipation in the different regions of the slug (i.e., the unperturbed Poiseuille-like bulk, the static menisci close to the tube axis and the dynamic regions close to the contact lines). Considering both partial and complete wetting, we find that the relationship between dimensionless velocity and weight is, in general, nonlinear. Whereas the relationship obtained for complete-wetting conditions is found in agreement with the experimental data of Bico and Quéré [J. Bico and D. Quéré, J. Colloid Interface Sci. 243, 262 (2001)], the scaling law under partial-wetting conditions is validated by numerical simulations performed with the Volume of Fluid method. The simulated steady velocities agree with the behavior predicted by the theoretical scaling laws in presence and in absence of static contact angle hysteresis. The numerical simulations suggest that wedge-flow dissipation alone cannot account for the entire additional drag and that the non-Poiseuille dissipation in the static menisci (not considered in previous studies) has to be considered for large contact angles.
Correlation between donor defects and ferromagnetism in insulating Sn1−xCoxO2 films
Authors: Liu X. F. , Iqbal Javed , Gong W. M. , Yang S. L. , Gao R. S. , Zeng F. , Yu R. H. , He B. , Hao Y. P. , Hao X. P.
Published: May 2009

Sn 1 − x Co x O 2 films have been fabricated to study the local structure of Co dopant and the mediation effects of donor defects (oxygen vacancies and Sn interstitials) on magnetic properties. Compared to as-grown film, the ferromagnetism is evidently enhanced after annealing in vacuum at 400 °C due to the increase in oxygen vacancies. While annealing at higher temperature, the ferromagnetism declines because of the domination of decrease in Sn interstitials over increase in oxygen vacancies in the films. The incorporation of Co dopant as well as the presence of oxygen vacancies and Sn interstitials is verified using x-ray absorption fine structure spectroscopy. The variations in the concentration of defects as a function of annealing temperature are obtained by positron annihilation spectroscopy technique. Additionally, the changes in structure and ferromagnetism after annealing in different atmospheres further demonstrate the crucial roles of oxygen vacancies and Sn interstitials in tuning ferromagnetism.
Particle model analyses of N2O dilution with He on electrical characteristics of radio-frequency discharges
Authors: Younis G. , Yousfi M. , Despax B.
Published: May 2009

The electrical characteristics (voltage, electric field, charged particle densities, dissipated power, particle energy, etc.) are analyzed in the case of low pressure (0.5 and 1 Torr) radio-frequency (rf) discharges in nitrous oxide (N2O)/Helium (He) mixtures. An optimized and validated particle model has been used for these analyses in the case of gradual dilutions of N2O with He buffer gas. A specific care is carried on the power density evolution and variation which show a complex behavior as a function of He proportion (up to 85%). These analyses are based on a microscopic approach enabling one to show the contribution of the different inelastic processes mainly between electrons and respectively N2O and He gases. This approach enables also one to show the discharge region (the positive column or the plasma region) where the power is preferentially dissipated. The power density variation is found to be mainly proportional to the electron density variation. The latter is dependent on the different processes occurring between the charged particles [i.e., electrons, negative ions (O− and NO−), and positive ions (N2O+ and He+)] and the neutral gas mixture (N2O and He). Furthermore, the particle model shows the role of the electron-He collisions on the variation in the electron energy and distribution. This allows more particularly explaining the effects of N2O dilution with He on the dissipated power variation in terms of creation and loss of electrons through collision processes.
Magnetic imaging method based on magnetic relaxation of magnetic nanoparticles
Authors: Sarangi S. , Tan I. C. , Brazdeikis A.
Published: May 2009

We present a well-posed magnetic imaging method based on magnetic relaxation of magnetic nanoparticles for obtaining high-spatial resolution image of magnetic tracers. The method relies on the principle that Néel relaxation of the magnetic nanoparticles is faster in a finite magnetic field than in the absence of the field. The magnetic nanoparticles are used as signal generator and a superconducting quantum interference device is used as the signal detector. An image of superparamagnetic iron oxide nanoparticle tracer is obtained directly by mapping the magnetization decays. The experimental imaging capability is demonstrated using commercially available gamma-ferric oxide (γ-Fe2O3) magnetic nanoparticles.
Photoreflectance study of exciton energies and linewidths for homoepitaxial and heteroepitaxial GaN layers
Authors: Kudrawiec R. , Rudziński M. , Serafinczuk J. , Zając M. , Misiewicz J.
Published: May 2009

Photoreflectance has been applied to study the exciton energies and linewidths for hetero- and homoepitaxial GaN layers (i.e., GaN layers grown on sapphire and truly bulk GaN crystal obtained by ammonothermal method). In order to modulate the built-in electric field inside the samples and eliminate photoluminescence signal from photoreflectance spectra, the surface band bending was modulated by the laser light with the photon energy smaller than the energy gap of GaN, i.e., a 532 nm laser line. The Varshni-type and Bose–Einstein-type parameters that describe the temperature dependence of the exciton transition energies have been evaluated and compared for the two GaN epilayers. It has been concluded that the residual strain in the heteroepitaxial layer influences the exciton transition energy but does not influence the Varshni and Bose–Einstein parameters. It has been found that this strain significantly influences the exciton linewidth. The broadening parameter, which is associated with the temperature-independent mechanisms (Γ0 parameter corresponding to the exciton linewidth at 0 K), has been found to be ∼1 meV for the homoepitaxial layer. For the heteroepitaxial layer this parameter is twice higher (this work) or few times higher (previous papers).
Correlation between microstructure and temperature dependence of magnetic properties in Fe60Co18(Nb,Zr)6B15Cu1 alloy series
Authors: Blázquez J. S. , Franco V. , Conde C. F. , Conde A. , Ferenc J. , Kulik T. , Kiss L. F.
Published: May 2009

Temperature dependence of magnetic properties of nanocrystalline Fe60Co18Cu1B15Nb6−xZrx (x=0, 3, 6) alloys has been studied at different stages of devitrification. Transmission electron microscopy shows nanocrystals of the size ∼5 nm, which remains almost constant along the nanocrystallization process. Curie temperature of the residual amorphous phase decreases as nanocrystallization progresses for all the studied alloys. Thermal dependence of the exchange stiffness constant is obtained from the measurement of specific magnetization and coercivity as a function of crystalline fraction and temperature for the three studied alloys.
Dependence of electron flux on electron temperature in spacecraft charging
Authors: Lai Shu T.
Published: May 2009

Two important observations when the onset of spacecraft surface charging occurs are (1) the electron flux measured in the high-energy (above several keV) channels onboard rises and (2) the ambient electron temperature rises above a critical value. We show by means of an analytical model that the two behaviors are consistent with each other.
Filamentation in argon microwave plasma at atmospheric pressure
Authors: Cardoso R. P. , Belmonte T. , Noël C. , Kosior F. , Henrion G.
Published: May 2009

Filamentation in an argon plasma is studied using a microwave cavity at atmospheric pressure. We show that the size and gas temperature of the filaments increase with the power absorbed by the plasma. The appearance of an additional filament occurs at specific values of the absorbed power. Each new filament appears with a smaller diameter than that of its parent filament but the sum of the diameters of all filaments evolves linearly with the absorbed power. A secondary filament emerges from a set of microfilaments created by a perturbation of the electric field (a slight increase in the incident power above a threshold value). This perturbation occurs over a larger radius than that of the parent filament. By resorting to modeling, we found that the filamentation process involves either a decrease in the effective frequency for momentum-transfer collisions, i.e., a lower electron temperature, or an increase in the electron density. We could show that a small change in the relative positions occupied by two filaments in the microwave cavity requires a strong variation in the electron temperature.
Isotropic transport in an oligothiophene derivative for single-crystal field-effect transistor applications
Authors: Reese Colin , Roberts Mark E. , Parkin Sean R. , Bao Zhenan
Published: May 2009

Single-crystal organic semiconductors have proven invaluable tools in the exploration of charge transport in molecular materials. We employ the elastomeric, photolithographically patterned single-crystal field-effect transistor in the study of an alpha-substituted oligothiophene. The terminal units specify a symmetric layered motif, while allowing the oligothiophene cores to pack closely. Angle-resolved measurements of the field-effect mobility reflect the symmetric edge/face interactions and isotropic mobility. These measurements are supported by electronic structure calculations that show nearly equivalent intermolecular interactions along cell diagonals. These results reveal that the transport is diffusive and a minimum of fourfold symmetry is required for in-plane mobility isotropy.
Frequency-resolved communication maps for proteins and other nanoscale materials
Authors: Leitner David M.
Published: May 2009

Proteins exhibit highly anisotropic flow of energy. There is presently much interest in locating channels that enable signaling between distant sites, possibly playing a role in protein function such as allostery. We present an approach for computing frequency-resolved local energy diffusivities, which provide a map of communication between protein residues as a function of the vibrational frequencies of the modes that carry energy between them. A network of vibrational energy transport channels can then be identified at select frequencies. Over most frequency ranges the communication maps vary widely with vibrational frequency, as we illustrate for the protein myoglobin. We expect the approach presented here to be useful in mapping frequency-sensitive signaling in a variety of materials on the nanoscale.
Thermodynamically dominant hydration structures of aqueous ions
Authors: Merchant Safir , Asthagiri D.
Published: May 2009

The hydration free energy of an ion is separated into a chemical term, arising due to the interaction of the ion with water molecules within the defined coordination sphere (the inner shell), a packing contribution, accounting for forming an ion-free coordination sphere (the observation volume) in the solvent, and a long range correction, accounting for the interaction of the ion with the solvent outside the coordination sphere. The chemical term is recast as a sum over coordination states, with the nth term depending on the probability of observing n water molecules in the observation volume and the free energy of assembling the n water molecules around the ion in the presence of the outer-shell solvent. Each stepwise increment in the coordination number more fully accounts for the chemical contribution, and this molecular aufbau approach is used to interrogate the thermodynamic importance of various hydration structures X[H2O]n of X(aq) (X=Na+, K+, F−) within a classical molecular mechanics framework. States with n less than (and at best equal to) the most probable coordination state ñ account for all of the chemical term and evince the role of the ion in drawing water molecules into the coordination sphere. For states with n>ñ, the influence of the ion is tempered and changes in coordination states due to density fluctuations in water also appear important. Thus the influence of the ion on the solvent matrix is local, and only a subset of water molecules (n≤ñ) contributes dominantly to the hydration thermodynamics. The n=4 state of Na+ (ñ=5) and K+ (ñ=7) and the n=6 state of F− (ñ=6) are thermodynamically dominant; adding a water molecule to the dominant state additionally contributes only about 2–3 kBT toward the chemical term, but removing a water molecule is very unfavorable.
Neutron and high energy deuteron anisotropy investigations in plasma focus device
Authors: Roshan M. V. , Rawat R. S. , Talebitaher A. , Lee P. , Springham S. V.
Published: May 2009

The anisotropies of neutron and high energy deuteron emissions from the NX2 plasma focus device [M. V. Roshan et al., Phys. Lett. A 373, 851 (2009)] are studied. The nuclear activation of graphite targets is used to measure the fluences of high energy deuterons in the axial and radial directions. Two bismuth germanate scintillation detectors connected to multichannel analyzer systems are used for the detection of 511 keV gamma rays resulting from positron annihilation in the two targets. In addition, fast neutron activation detectors are employed to measure the axial and radial fluences of fusion neutrons. These detection systems are calibrated using the simulation code MCNPX [L. S. Waters et al., AIP Conf. Proc. 896, 81 (2007)]. Two distinct regimes of neutron and deuteron anisotropies are observed for the NX2 device. For deuterium gas pressures below 10 mbar, the neutron anisotropy increases with increasing pressure, while the overall neutron yield remains low. For gas pressures of 10–14 mbar, the neutron anisotropy is essentially constant, while, with increasing pressure, the neutron yield rises rapidly and the deuteron anisotropy falls.
Sedimentation adsorption of a charge-regulated colloidal particle onto a large charged disk
Authors: Hsu Jyh-Ping , Liu Kuan-Liang
Published: May 2009

The sedimentation adsorption of a charge-regulated colloidal particle, which simulates biocolloids such as cells, onto a large, charged disk is modeled theoretically. The influences of the parameters’ key to the present problem, including the particle size, the nature of the acidic and basic functional groups on the particle surface, the initial particle-disk distance, and the surface potential of the disk, on the dynamic sedimentation behavior of the particle are investigated. The loci of a particle under various conditions are simulated to justify the specific behaviors of the phenomenon under consideration. In general, the smaller the fraction of the acidic functional groups and/or the lower the surface potential of the disk, the shorter the sedimentation time is. It is interesting to observe that the larger the particle and/or the longer the initial particle-disk distance do not necessarily lead to a longer sedimentation time.
Plasmon-enhanced luminescence in Yb3+:Y2O3 thin film and the potential for solar cell photon harvesting
Authors: Lu Yalin , Chen Xiaobing
Published: May 2009

Photoluminescence in Yb3+:Y2O3 thin films grown on sapphire substrates are enhanced using arrays of gold nanoparticles having different shape aspect ratios. The enhanced photoluminescence is attributed to the resonance of localized surface plasmon resonance modes of gold nanoparticles with multiple optical transition lines of the doped Yb3+ ions. Its potential as an effective means for solar cell photon harvesting through efficient frequency shifting is also discussed, considering the demonstrated benefits of broad spectral response and much relaxed tolerance for nanofabrication.
Molecular design of photoactive acenes for organic photovoltaics
Authors: Huang Liping , Rocca Dario , Baroni Stefano , Gubbins Keith E. , Nardelli Marco Buongiorno
Published: May 2009

Absorption spectra of n-acenes (n from 2 to 6, for naphthalene, anthracene, tetracene, pentacene, and hexacene, respectively) have been calculated using a newly developed code based on time-dependent density-functional theory. Our calculations show that absorption spectra and charge carrier mobility of acenes not only depend on the molecular identity but also on the molecular packing. By designing the interaction between metal substrates and the first layer of acene molecules, they can be packed in a face-to-face fashion instead of the conventional herringbone (face-to-edge) arrangement. Acenes in the cofacial packing would increase the π-orbital overlap and thus enhance the charge mobility by maximizing electronic coupling between adjacent molecules. Absorption spectra of cofacially packed acenes have a better overlap with the solar spectrum, which allows harvesting more of the solar energy from red photons.
Universal 1/f noise model for reverse biased diodes
Authors: Kinch M. A. , Wan C.-F. , Schaake H. , Chandra D.
Published: May 2009

A 1/f noise model is developed for reverse biased diodes based on McWhorter’s concept of charge tunneling into semiconductor states at passivation layer interfaces [A. L. McWhorter, in Semiconductor Surface Physics, edited by R. H. Kingston (University of Pennsylvania Press, Philadelphia, 1957), pp. 207–228]. The charge modulates the width of semiconductor surface charge layers on either side of the junction, resulting in fluctuations in dark current from these volumes due to the net difference in depletion and diffusion current generation rates per unit volume in the semiconductor. The 1/f spectrum associated with the fluctuating surface charge translates into a 1/f spectrum in thermally generated diode dark current. The model is applied to midwavelength infrared HgCdTe N+/P diode architectures.
Preparing spin-polarized scanning tunneling microscope probes on capped carbon nanotubes by Fe doping: A first-principles study
Authors: Zou Xiaolong , Zhou Gang , Li Jia , Yan Binghai , Wu Jian , Gu Bing-Lin , Duan Wenhui
Published: May 2009

Our first-principles calculations indicate the possibility of preparing spin-polarized scanning tunneling microscopy (SP-STM) probes from Fe-doped capped carbon nanotubes (CNTs). The structural stability, magnetic moment, and electronic property of hybrid systems are found to depend on the Fe adsorption site, which is attributed to the hybridization between Fe 3d and C 2p orbitals. The CNTs with Fe atoms adsorbed at the tip-top are demonstrated to be promising candidates for the SP-STM probe, with a high spin polarization leading to a completely spin-polarized current at lower voltages. In contrast, the CNTs encapsulating Fe atom are basically nonmagnetic, and thus useless for the SP-STM probe application in nature.
Nonlinear longitudinal compression of short laser pulses in the atmosphere
Authors: Yedierler Burak
Published: May 2009

Propagation of short and intense laser beams in the atmosphere is considered for the purpose of identifying the temporal compression. The conditions and validity of linear and nonlinear compression theories are discussed. The effects of chirping and pulse power in the preionization regime are deliberated. The fact that the linear theory cannot explain the pulse compression in the atmosphere is presented.
Significant second-harmonic generation in two lead-free polar oxides BiInO3 and BiAlO3: A first-principles investigation
Authors: Ju Sheng , Cai Tian-Yi
Published: May 2009

Density functional theory with the generalized gradient approximation is applied to study the second-harmonic generation (SHG) in two lead-free polar oxides BiInO3 and BiAlO3. Significant SHG susceptibilities, larger than 500 (10−9 esu), are revealed in both of them. The low frequency limit is found to reach 13 (10−9 esu) and 43 (10−9 esu) for BiInO3 and BiAlO3, respectively. In the meantime, the linear optical response shows weak optical anisotropy and the absorption edge is around 3 eV for both of them. All these results are consistent with their unusual polar structure and demonstrate their potential application in nonlinear optoelectronics.
Indentation-induced low-temperature solid-phase crystallization of Si1−xGex (x=–1) on insulator
Authors: Toko Kaoru , Sadoh Taizoh , Miyao Masanobu
Published: May 2009

Indentation-induced solid-phase crystallization (SPC) was proposed to achieve low-temperature growth of Si1−xGex (x=0–1) on insulator. Crystal nucleation was enhanced at the indented positions due to the stress effect, which triggered the lateral SPC. As a result, large Si1−xGex (x=0–1) crystal regions (>2 μm) were achieved on insulator at low temperatures (<590 °C). The growth kinetics for this catalyst metal-free process, i.e., activation energies for nucleation and lateral growth, are presented as a function of the Ge fraction (x).
The making of ferromagnetic Fe doped ZnO nanoclusters
Authors: Ganguli Nirmal , Dasgupta Indra , Sanyal Biplab
Published: May 2009

In this letter, the authors present a study of the energetics and magnetic interactions in Fe doped ZnO clusters by ab initio density functional calculations. The results indicate that defects under suitable conditions can induce ferromagnetic interactions between the dopant Fe atoms whereas antiferromagnetic coupling dominates in a neutral defect-free cluster. The calculations also reveal an unusual ionic state of the dopant Fe atom residing at the surface of the cluster, a feature that is important to render the cluster ferromagnetic.
High-resolution infrared spectroscopy of Mg–HF and Mg–(HF)2 solvated in helium nanodroplets
Authors: Stiles Paul L. , Douberly Gary E. , Miller Roger E.
Published: May 2009

High-resolution infrared (IR) spectroscopy is used to investigate the Mg–HF and Mg–(HF)2 van der Waals complexes. Both complexes are formed and probed within helium nanodroplets. Rotationally resolved zero-field and Stark spectra are assigned to a linear binary complex composed of a Mg atom bound to the hydrogen end of the HF molecule. Although high level ab initio calculations predict a fluorine bonded complex, none of the observed IR bands can be assigned to this complex. The collocation method is employed to determine the bound states on the two-dimensional intermolecular Mg–HF potential energy surface. The ground and first excited state wave functions for this potential surface have zero amplitude in the well corresponding to the fluorine bonded complex, consistent with experiment. The two HF stretching bands of the Mg–(HF)2 complex are observed and assigned using a combination of the spectral symmetry, ab initio calculations, pick-up cell pressure dependencies, and dipole moment measurements. Comparisons with the helium solvated HF dimer show large changes to the HF stretching frequencies upon the addition of a single Mg atom to the hydrogen side of (HF)2.
Enhancement of light absorption in a quantum well by surface plasmon polariton
Authors: Khurgin J. B. , Sun G.
Published: May 2009

We investigate analytically the degree to which the absorption of light in a single quantum well can be enhanced in the proximity of a structured metallic surface and show that the wavelength at which the maximum enhancement of about one order of magnitude is attained depends on metal loss and the initial absorption in a quantum well.
Domain wall conduit behavior in cobalt nanowires grown by focused electron beam induced deposition
Authors: Fernández-Pacheco A. , De Teresa J. M. , Córdoba R. , Ibarra M. R. , Petit D. , Read D. E. , O’Brien L. , Lewis E. R. , Zeng H. T. , Cowburn R. P.
Published: May 2009

The domain wall nucleation and propagation fields in cobalt nanowires grown by focused electron beam induced deposition are measured using spatially resolved magneto-optical Kerr effect. The study was systematically done for wire widths from 600 to 150 nm, finding significant differences in the value of both fields for the wires, indicating high quality domain wall conduit behavior. The extreme simplicity and flexibility of this technique with respect to the multistep lithographic processes used nowadays opens a different route to create magnetic nanostructures with a good control of the domain wall motion.
Influence of surface-related states on the carrier dynamics in (Ga,In)N/GaN single quantum wells
Authors: Othonos Andreas , Itskos G. , Bradley D. D. C. , Dawson M. D. , Watson I. M.
Published: May 2009

We report on the influence of surface-related states on the relaxation of carriers within single (Ga,In)N/GaN quantum wells. Two identical samples that differ only in the thickness of the top GaN cap layer were studied. Photoluminescence and pump-probe measurements reveal significant variations in the quantum well integrated emission and the carrier relaxation decay times in the two samples, when probing both the ground and excited states of the wells. The variations are attributed to the presence of an efficient nonradiative relaxation channel associated with the proximity of the quantum well excitations to the surface-related states in the thin-cap sample.
Metastable bouncing droplets
Authors: Terwagne D. , Gilet T. , Vandewalle N. , Dorbolo S.
Published: May 2009

An oil droplet is placed on an oil bath at least ten times more viscous. When the oil bath is vertically shaken according to a sinusoidal motion, the droplet may bounce indefinitely on the bath. This sustained bouncing mode is stable when the forcing acceleration is higher than a threshold value. On the other hand, the time of subsidence of the droplet on the bath is finite at weaker accelerations. The lifetime of bouncing droplets is measured for various viscosities and forcing parameters. The finiteness of the lifetime is correlated with the evolution of the interference fringe pattern made by the air film squeezed between the droplet and the bath when lighted by a monochromatic light. Finally, a model based on a combination of lubrication theory and droplet deformations rationalizes the experimental results.
Terrestrial-Passage Theory: Failing a Test
Authors: Reed Charles F , Krupinski Elizabeth A
Published: May 2009

Terrestrial-passage theory proposes that the ‘moon’ and ‘sky’ illusions occur because observers learn to expect an elevation-dependent transformation of visual angle. The transformation accompanies daily movement through ordinary environments of fixed-altitude objects.

Celestial objects display the same visual angle at all elevations, and hence are necessarily non-conforming with the ordinary transformation. On hypothesis, observers should target angular sizes to appear greater at elevation than at horizon. However, in a sample of forty-eight observers there was no significant difference between the perceived angular size of a constellation of stars at horizon and that predicted for a specific elevation. Occurrence of the illusion was not restricted to those observers who expected angular expansion. These findings fail to support the terrestrial-passage theory of the illusion.
The C-project: use of self-collection kits to screen for Chlamydia trachomatis in young people in a community-based health promotion project
Authors: Martin Lynne , Freedman Eleanor , Burton Leanne , Rutter Scott , Knight Vickie , D'Amato Alfa , Murray Carolyn , Drysdale Jackie , Harvey Sophie , McNulty Anna
Published: May 2009

Background: The present study aimed to ascertain the acceptability to at-risk young people of self-collected urine samples as a means of testing for Chlamydia trachomatis (chlamydia); to determine the effectiveness of drop-off and outreach collection methods as a means of detecting and treating chlamydia; and to determine the rate of positive chlamydia tests in a sample of the target group. Methods: Participants requested postal testing kits from the project website, the NSW Sexual Health Infoline or at an outreach event and either returned urine samples at selected drop-off locations or directly to the researchers during active outreach events. Results: A total of 413 kits were requested – 196 (47.5%) via email, 204 (49.4%) during outreach events and nine (2.2%) via the NSW Sexual Health Infoline. A total of 195 samples (47.2% of ordered kits) were returned. Participants were less likely to return samples if they had been requested by email (odds ratio = 9.6; 95% confidence interval: 6.0–15.0) or via telephone (odds ratio = 22.0; 95% confidence interval: 2.7–181.0) compared with directly obtaining a kit at an outreach event. The number of specimens positive for chlamydia in the targeted age range was 4, giving a 3.1% positive rate (95% confidence interval: 1.0–8.0). Conclusions: This study identified that free testing kits and online communication worked well as a means of engaging young people and raising awareness of sexual health. However, the requirement to drop-off urine samples at selected locations was not well accepted.
The check is in the mail: piloting a novel approach to Chlamydia trachomatis testing using self-collected, mailed specimen
Authors: Buhrer-Skinner Monika , Muller Reinhold , Bialasiewicz Seweryn , Sloots Theo P. , Debattista Joseph , Gordon Rose , Buettner Petra G.
Published: May 2009

Objectives: To develop, implement and evaluate the processes of a novel approach to chlamydia testing that is accessible, confidential, free of charge, easy to use, and allows for self-collection of specimens, their transportation by regular mail and the central management of results. Methods: A ‘self-collection kit’ was developed including all items and instructions necessary to obtain a sample. A network of distribution sites at locations frequented by the target population has been established. The ‘kits’ can be requested via an advertised website and by phone. Specimens are returned via reply paid mail. A centralised system for the management of results and follow up has been established. Test results are conveyed by the participant’s method of choice. Treatment is organised via a network of health care providers. Results: Of the first 100 returned kits 99% were safely packed and 86% were sent back with a completely filled out pathology request form. Ninety-two participants provided contact details; 70.7% indicated mobile phone or SMS as the preferred methods to receive results. Seven positive cases were identified and treatment was confirmed for all within 6 days. Discussion: These findings provide evidence that the presented approach to chlamydia testing is easy to implement, achieves excellent follow-up and treatment rates, and therefore opens important new channels to otherwise difficult to access high-risk populations, such as young people and geographically and socially isolated populations.
Lipid rafts inflate at the trans-Golgi
Authors: Short Ben
Published: May 2009

A new method to characterize the lipid content of vesicles suggests how cells sort secretory cargo.
Nemo kinase interacts with Mad to coordinate synaptic growth at the Drosophila neuromuscular junction
Authors: Merino Carlos , Penney Jay , González Miranda , Tsurudome Kazuya , Moujahidine Myriam , O'Connor Michael B. , Verheyen Esther M. , Haghighi Pejmun
Published: May 2009

Bone morphogenic protein (BMP) signaling is essential for the coordinated assembly of the synapse, but we know little about how BMP signaling is modulated in neurons. Our findings indicate that the Nemo (Nmo) kinase modulates BMP signaling in motor neurons. nmo mutants show synaptic structural defects at the Drosophila melanogaster larval neuromuscular junction, and providing Nmo in motor neurons rescues these defects. We show that Nmo and the BMP transcription factor Mad can be coimmunoprecipitated and find a genetic interaction between nmo and Mad mutants. Moreover, we demonstrate that Nmo is required for normal distribution and accumulation of phosphorylated Mad in motor neurons. Finally, our results indicate that Nmo phosphorylation of Mad at its N terminus, distinct from the BMP phosphorylation site, is required for normal function of Mad. Based on our findings, we propose a model in which phosphorylation of Mad by Nmo ensures normal accumulation and distribution of Mad and thereby fine tunes BMP signaling in motor neurons.