bluuebunny/crossref_metadata_2025 huggingface dataset:
Dust radiative forcing in snow of the Upper Colorado River Basin: 1. A 6 year record of energy balance, radiation, and dust concentrations
Authors: Painter Thomas H. , Skiles S. McKenzie , Deems Jeffrey S. , Bryant Ann C. , Landry Christopher C.
Published: June 2012

Dust in snow accelerates snowmelt through its direct reduction of snow albedo and its further indirect reduction of albedo by accelerating the growth of snow grains. Since the westward expansion of the United States that began in the mid‐19th century, the mountain snow cover of the Colorado River Basin has been subject to five‐fold greater dust loading, largely from the Colorado Plateau and Great Basin. Radiative forcing of snowmelt by dust is not captured by conventional micrometeorological measurements, and must be monitored by a more comprehensive suite of radiation instruments. Here we present a 6 year record of energy balance and detailed radiation measurements in the Senator Beck Basin Study Area, San Juan Mountains, Colorado, USA. Data include broadband irradiance, filtered irradiance, broadband reflected flux, filtered reflected flux, broadband and visible albedo, longwave irradiance, wind speed, relative humidity, and air temperatures. The gradient of the snow surface is monitored weekly and used to correct albedo measurements for geometric effects. The snow is sampled weekly for dust concentrations in plots immediately adjacent to each tower over the melt season. Broadband albedo in the last weeks of snow cover ranged from 0.33 to 0.55 across the 6 years and two sites. Total end of year dust concentration in the top 3 cm of the snow column ranged from 0.23 mg g−1 to 4.16 mg g−1. These measurements enable monitoring and modeling of dust and climate‐driven snowmelt forcings in the Upper Colorado River Basin.
Host genetic and environmental effects on mouse intestinal microbiota
Authors: Campbell James H , Foster Carmen M , Vishnivetskaya Tatiana , Campbell Alisha G , Yang Zamin K , Wymore Ann , Palumbo Anthony V , Chesler Elissa J , Podar Mircea
Published: June 2012

The mammalian gut harbors complex and variable microbial communities, across both host phylogenetic space and conspecific individuals. A synergy of host genetic and environmental factors shape these communities and account for their variability, but their individual contributions and the selective pressures involved are still not well understood. We employed barcoded pyrosequencing of V1-2 and V4 regions of bacterial small subunit ribosomal RNA genes to characterize the effects of host genetics and environment on cecum assemblages in 10 genetically distinct, inbred mouse strains. Eight of these strains are the foundation of the Collaborative Cross (CC), a panel of mice derived from a genetically diverse set of inbred founder strains, designed specifically for complex trait analysis. Diversity of gut microbiota was characterized by complementing phylogenetic and distance-based, sequence-clustering approaches. Significant correlations were found between the mouse strains and their gut microbiota, reflected by distinct bacterial communities. Cohabitation and litter had a reduced, although detectable effect, and the microbiota response to these factors varied by strain. We identified bacterial phylotypes that appear to be discriminative and strain-specific to each mouse line used. Cohabitation of different strains of mice revealed an interaction of host genetic and environmental factors in shaping gut bacterial consortia, in which bacterial communities became more similar but retained strain specificity. This study provides a baseline analysis of intestinal bacterial communities in the eight CC progenitor strains and will be linked to integrated host genotype, phenotype and microbiota research on the resulting CC panel.
One millimetre makes the difference: high-resolution analysis of methane-oxidizing bacteria and their specific activity at the oxic–anoxic interface in a flooded paddy soil
Authors: Reim Andreas , Lüke Claudia , Krause Sascha , Pratscher Jennifer , Frenzel Peter
Published: June 2012

Aerobic methane-oxidizing bacteria (MOB) use a restricted substrate range, yet >30 species-equivalent operational taxonomical units (OTUs) are found in one paddy soil. How these OTUs physically share their microhabitat is unknown. Here we highly resolved the vertical distribution of MOB and their activity. Using microcosms and cryosectioning, we sub-sampled the top 3-mm of a water-saturated soil at near in situ conditions in 100-μm steps. We assessed the community structure and activity using the particulate methane monooxygenase gene pmoA as a functional and phylogenetic marker by terminal restriction fragment length polymorphism (t-RFLP), a pmoA-specific diagnostic microarray, and cloning and sequencing. pmoA genes and transcripts were quantified using competitive reverse transcriptase PCR combined with t-RFLP. Only a subset of the methanotroph community was active. Oxygen microprofiles showed that 89% of total respiration was confined to a 0.67-mm-thick zone immediately above the oxic–anoxic interface, most probably driven by methane oxidation. In this zone, a Methylobacter-affiliated OTU was highly active with up to 18 pmoA transcripts per cell and seemed to be adapted to oxygen and methane concentrations in the micromolar range. Analysis of transcripts with a pmoA-specific microarray found a Methylosarcina-affiliated OTU associated with the surface zone. High oxygen but only nanomolar methane concentrations at the surface suggested an adaptation of this OTU to oligotrophic conditions. No transcripts of type II methanotrophs (Methylosinus, Methylocystis) were found, which indicated that this group was represented by resting stages only. Hence, different OTUs within a single guild shared the same microenvironment and exploited different niches.
The metatranscriptome of a deep-sea hydrothermal plume is dominated by water column methanotrophs and lithotrophs
Authors: Lesniewski Ryan A , Jain Sunit , Anantharaman Karthik , Schloss Patrick D , Dick Gregory J
Published: June 2012

Microorganisms mediate geochemical processes in deep-sea hydrothermal vent plumes, which are a conduit for transfer of elements and energy from the subsurface to the oceans. Despite this important microbial influence on marine geochemistry, the ecology and activity of microbial communities in hydrothermal plumes is largely unexplored. Here, we use a coordinated metagenomic and metatranscriptomic approach to compare microbial communities in Guaymas Basin hydrothermal plumes to background waters above the plume and in the adjacent Carmen Basin. Despite marked increases in plume total RNA concentrations (3–4 times) and microbially mediated manganese oxidation rates (15–125 times), plume and background metatranscriptomes were dominated by the same groups of methanotrophs and chemolithoautotrophs. Abundant community members of Guaymas Basin seafloor environments (hydrothermal sediments and chimneys) were not prevalent in the plume metatranscriptome. De novo metagenomic assembly was used to reconstruct genomes of abundant populations, including Marine Group I archaea, Methylococcaceae, SAR324 Deltaproteobacteria and SUP05 Gammaproteobacteria. Mapping transcripts to these genomes revealed abundant expression of genes involved in the chemolithotrophic oxidation of ammonia (amo), methane (pmo) and sulfur (sox). Whereas amo and pmo gene transcripts were abundant in both plume and background, transcripts of sox genes for sulfur oxidation from SUP05 groups displayed a 10–20-fold increase in plumes. We conclude that the biogeochemistry of Guaymas Basin hydrothermal plumes is mediated by microorganisms that are derived from seawater rather than from seafloor hydrothermal environments such as chimneys or sediments, and that hydrothermal inputs serve as important electron donors for primary production in the deep Gulf of California.
Genome-enabled transcriptomics reveals archaeal populations that drive nitrification in a deep-sea hydrothermal plume
Authors: Baker Brett J , Lesniewski Ryan A , Dick Gregory J
Published: June 2012

Ammonia-oxidizing Archaea (AOA) are among the most abundant microorganisms in the oceans and have crucial roles in biogeochemical cycling of nitrogen and carbon. To better understand AOA inhabiting the deep sea, we obtained community genomic and transcriptomic data from ammonium-rich hydrothermal plumes in the Guaymas Basin (GB) and from surrounding deep waters of the Gulf of California. Among the most abundant and active lineages in the sequence data were marine group I (MGI) Archaea related to the cultured autotrophic ammonia-oxidizer, Nitrosopumilus maritimus. Assembly of MGI genomic fragments yielded 2.9 Mb of sequence containing seven 16S rRNA genes (95.4–98.4% similar to N. maritimus), including two near-complete genomes and several lower-abundance variants. Equal copy numbers of MGI 16S rRNA genes and ammonia monooxygenase genes and transcription of ammonia oxidation genes indicates that all of these genotypes actively oxidize ammonia. De novo genomic assembly revealed the functional potential of MGI populations and enhanced interpretation of metatranscriptomic data. Physiological distinction from N. maritimus is evident in the transcription of novel genes, including genes for urea utilization, suggesting an alternative source of ammonia. We were also able to determine which genotypes are most active in the plume. Transcripts involved in nitrification were more prominent in the plume and were among the most abundant transcripts in the community. These unique data sets reveal populations of deep-sea AOA thriving in the ammonium-rich GB that are related to surface types, but with key genomic and physiological differences.
Esophagus
Authors: Babaei Arash
Published: June 2012

The esophagus is an important conduit between the oropharynx and the stomach. Having an understanding of the esophageal anatomy and physiology may allow the deglutologist to analyze a patient's signs and symptoms in order to arrive at a differential diagnosis, management, and treatment plan. This article describes the esophageal anatomy and physiology, including the important reflexes that underscore the interrelatedness of the oropharynx, airway, and esophagus.
Food for Thought
Authors: Easterling Caryn
Published: June 2012

Our professional American Speech-Language-Hearing Association (ASHA) guidelines state, if a speech-language pathologist suspects on the basis of the clinical history that there may be an esophageal disorder contributing to the patient's dysphagia, then “An esophageal screening can be incorporated into most [videofluoroscopic swallowing studies, or] VFSS” (ASHA, 2004). However, the esophageal screen has not been defined by ASHA or by the American College of Radiology. This “Food for Thought” column suggests deglutologists work together to determine the procedure and expected outcome for the esophageal screen so that there is acceptance and consensus among the multidisciplinary team members who evaluate patients with dysphagia.
Response to “Comment on ‘Continuum modes in rotating plasmas: General equations and continuous spectra for large aspect ratio tokamaks’ ” [Phys. Plasmas 19, 064701 (2012)]
Authors: Lakhin V. P. , Ilgisonis V. I.
Published: June 2012

The equations for the continuous spectra derived in our paper [V. P. Lakhin and V. I. Ilgisonis, Phys. Plasmas 18, 092103 (2011)] can be reduced to the matrix form used by Goedbloed et al. [Phys. Plasmas 11, 28 (2004)]. It is shown that the assumptions made in our paper provide the elliptic flow regime and guarantee the existence of plasma equilibrium with nested magnetic surfaces of circular cross-section. The new results on magnetohydrodynamic instabilities of such tokamak equilibria obtained in our paper but absent in the paper by Goedbloed et al. are emphasized.
Structure and aggregation of colloids immersed in critical solvents
Authors: Mohry T. F. , Maciołek A. , Dietrich S.
Published: June 2012

We consider an ensemble of spherical colloidal particles immersed in a near-critical solvent such as a binary liquid mixture close to its critical demixing point. The emerging long-ranged fluctuations of the corresponding order parameter of the solvent drive the divergence of the correlation length. Spatial confinements of these critical fluctuations by colloidal solute particles, acting as cavities in the fluctuating medium, restrict and modify the fluctuation spectrum in a way which depends on their relative configuration. This results in effective, so-called critical Casimir forces (CCFs) acting on the confining surfaces. Using the available knowledge about CCFs we study the structure and stability of such colloidal suspensions by employing an approach in terms of effective, one-component colloidal systems. Applying the approximation of pairwise additive CCFs we calculate the radial distribution function of the colloids, which is experimentally accessible. We analyze colloidal aggregation due to CCFs and thus allude to previous experimental studies which are still under debate.
The instantaneous shear modulus in the shoving model
Authors: Dyre Jeppe C. , Wang Wei Hua
Published: June 2012

We point out that the instantaneous shear modulus G∞ of the shoving model for the non-Arrhenius temperature dependence of viscous liquids’ relaxation time is the experimentally accessible high-frequency plateau modulus, not the idealized instantaneous affine shear modulus that cannot be measured. Data for a large selection of metallic glasses are compared to three different versions of the shoving model. The original shear-modulus based version shows a slight correlation to the Poisson ratio, which is eliminated by the energy-landscape formulation of the model in which the bulk modulus plays a minor role.
Characterizing hydrophobicity at the nanoscale: A molecular dynamics simulation study
Authors: Bandyopadhyay Dibyendu , Choudhury Niharendu
Published: June 2012

We use molecular dynamics (MD) simulations of water near nanoscopic surfaces to characterize hydrophobic solute-water interfaces. By using nanoscopic paraffin like plates as model solutes, MD simulations in isothermal-isobaric ensemble have been employed to identify characteristic features of such an interface. Enhanced water correlation, density fluctuations, and position dependent compressibility apart from surface specific hydrogen bond distribution and molecular orientations have been identified as characteristic features of such interfaces. Tetrahedral order parameter that quantifies the degree of tetrahedrality in the water structure and an orientational order parameter, which quantifies the orientational preferences of the second solvation shell water around a central water molecule, have also been calculated as a function of distance from the plate surface. In the vicinity of the surface these two order parameters too show considerable sensitivity to the surface hydrophobicity. The potential of mean force (PMF) between water and the surface as a function of the distance from the surface has also been analyzed in terms of direct interaction and induced contribution, which shows unusual effect of plate hydrophobicity on the solvent induced PMF. In order to investigate hydrophobic nature of these plates, we have also investigated interplate dewetting when two such plates are immersed in water.
Local and nonlocal contributions to molecular first-order hyperpolarizability: A Hirshfeld partitioning analysis
Authors: Zeng Qun , Liu Liuxia , Zhu Wenhai , Yang Mingli
Published: June 2012

Based on first-principles calculations, a decomposition scheme is proposed to investigate the molecular site-specific first-order hyperpolarizability (β) responses by means of Hirshfeld population analysis and finite field method. For a molecule, its β is decomposed into local and nonlocal contributions of individual atoms or groups. The former describes the response within the atomic sphere, while the latter describes the contributions from interatomic charge transfer. This scheme is then applied to six prototypical donor-acceptor (D-A) or D-π-A molecules for which the local and nonlocal hyperpolarizabilities are evaluated based on their MP2 density. Both the local and nonlocal parts exhibit site-specific characteristics, but vary differently with molecular structures. The local part depends mainly on the atomic attributes such as electronegativity and charge state, as well as its location in the molecule, while the nonlocal part relates to the ability and distance of charge delocalization within the molecule, increasing rapidly with molecular size. The proposed decomposition scheme provides a way to distinguish atomic or group contributions to molecular hyperpolarizabilities, which is useful in the molecular design for organic nonlinear optical materials.
Full-dimensional (15-dimensional) ab initio analytical potential energy surface for the ${\rm H}_7^+$H7+ cluster
Authors: Barragán Patricia , Prosmiti Rita , Wang Yimin , Bowman Joel M.
Published: June 2012

Full-dimensional ab initio potential energy surface is constructed for the \documentclass[12pt]{minimal}\begin{document}${\rm H}_7^+$\end{document}H7+ cluster. The surface is a fit to roughly 160 000 interaction energies obtained with second-order MöllerPlesset perturbation theory and the cc-pVQZ basis set, using the invariant polynomial method [B. J. Braams and J. M. Bowman, Int. Rev. Phys. Chem. 28, 577 (2009)10.1080/01442350903234923]. We employ permutationally invariant basis functions in Morse-type variables for all the internuclear distances to incorporate permutational symmetry with respect to interchange of H atoms into the representation of the surface. We describe how different configurations are selected in order to create the database of the interaction energies for the linear least squares fitting procedure. The root-mean-square error of the fit is 170 cm−1 for the entire data set. The surface dissociates correctly to the \documentclass[12pt]{minimal}\begin{document}${\rm H}_5^+$\end{document}H5+ + H2 fragments. A detailed analysis of its topology, as well as comparison with additional ab initio calculations, including harmonic frequencies, verify the quality and accuracy of the parameterized potential. This is the first attempt to present an analytical representation of the 15-dimensional surface of the \documentclass[12pt]{minimal}\begin{document}${\rm H}_7^+$\end{document}H7+ cluster for carrying out dynamics studies.
Different effects of zwitterion and ethylene glycol on proteins
Authors: Shao Qing , He Yi , White Andrew D. , Jiang Shaoyi
Published: June 2012

In this work, we investigated the effects of carboxybetaine (CB) and (ethylene glycol)4 (EG4) solutes on chymotrypsin inhibitor 2 (CI2) as a model protein using molecular dynamics simulations. The properties studied include the radial distribution functions of these two solutes to the C-α atoms of the 64 residues of CI2, the average numbers of solute-protein and water-protein hydrogen bonds, the root mean square deviation of the C-α atoms of the protein, and the solvent access surface area of the protein. Results show that these two solutes share some common properties while have some different effects on the protein. Both of these two solutes do not accumulate preferentially near the protein and CI2 is folded with either of them. However, CI2 is found to have properties in the CB solution closer to bulk water, whereas CI2 shows reduced flexibility and decreased SASA of the hydrophobic domain in the EG4 solution. Although the protein is folded with both CB and EG4, superhydrophilic CB has a minimal effect on the protein due to the shared zwitterionic nature of both CB and protein whereas amphiphilic EG4 alters the properties of the protein via hydrophobic interactions.
On a (β, q)-generalized Fisher information and inequalities involving q-Gaussian distributions
Authors: Bercher J.-F.
Published: June 2012

In the present paper, we would like to draw attention to a possible generalized Fisher information that fits well in the formalism of nonextensive thermostatistics. This generalized Fisher information is defined for densities on \documentclass[12pt]{minimal}\begin{document}$\mathbb {R}^{n}.$\end{document}Rn. Just as the maximum Rényi or Tsallis entropy subject to an elliptic moment constraint is a generalized q-Gaussian, we show that the minimization of the generalized Fisher information also leads a generalized q-Gaussian. This yields a generalized Cramér-Rao inequality. In addition, we show that the generalized Fisher information naturally pops up in a simple inequality that links the generalized entropies, the generalized Fisher information, and an elliptic moment. Finally, we give an extended Stam inequality. In this series of results, the extremal functions are the generalized q-Gaussians. Thus, these results complement the classical characterization of the generalized q-Gaussian and introduce a generalized Fisher information as a new information measure in nonextensive thermostatistics.
Existence of ground states for a one-dimensional relativistic Schrödinger equation
Authors: Borgna Juan P. , Rial Diego F.
Published: June 2012

Relativistic Schrödinger equation with a nonlinear potential interaction describes the dynamics of a particle, with rest mass m, travelling to a significant fraction |v| < 1 of the light speed c = 1. At first, we deal with the local and global existence of solutions of the flux, and in the second term, and according to the relativistic nature of the problem, we look for boosted solitons as ψ(x, t) = eiμtφv(x − vt), where the profile \documentclass[12pt]{minimal}\begin{document}$\varphi _{v}\in H^{1/2}\left( \mathbb {R}\right)$\end{document}φv∈H1/2R is a minimizer of a suitable variational problem. Our proof uses a concentration-compactness-type argument. Stability results for the boosted solitons are established.
Investigation of the Ti/MgCl2 interface on a Si(111) 7 × 7 substrate
Authors: Karakalos S. , Skala T. , Plekan O. , Ladas S. , Prince K. , Matolin V. , Chab V. , Siokou A.
Published: June 2012

Photoelectron spectroscopy with synchrotron radiation, low energy electron diffraction, and ion-scattering spectroscopy were used in order to study the Ti/MgCl2 interface grown on an atomically clean Si(111) 7 × 7 substrate. A series of high resolution spectra after deposition of a thick MgCl2 layer, step by step deposition of Ti and gradual annealing, indicated a very reactive interface even at room temperature. Strong interaction between the incoming Ti atoms and the MgCl2 layer, leads to the formation of Ti2+ and Ti4+ oxidation states. The interfacial interaction continues even at multilayer Ti coverage mainly by the partial disruption of Mg–Cl bonds and the formation of Ti–Cl sites, rendering this interface a very promising UHV-compatible model of a pre-catalyst for olefin polymerization. After the final annealing, the MgCl2 multilayers desorb while Ti remains on the surface forming a silicide layer on which Cl and Mg atoms are attached.
C-III flow measurements with a coherence imaging spectrometer
Authors: Weber T. R. , Allen S. L. , Howard J.
Published: June 2012

This work describes a coherence imaging spectrometer capable of making spatially resolved CIII flow measurements in the DIII-D lower divertor. The spectrometer exploits a periscope view of the plasma to produce line-of-sight averaged velocity measurements of CIII. From these chord averaged flow measurements, a 2D poloidal cross section of the CIII flow is tomographically reconstructed. Details of the diagnostic setup, acquired data, and data analysis will be presented, along with prospects for future applications.
Phase diagrams of binary mixtures of liquid crystals and rodlike polymers in the presence of an external field
Authors: Matsuyama Akihiko , Ueda Tomomi
Published: June 2012

We theoretically study phase separations in mixtures of a low molecular-weight-liquid crystalline molecule (LC) and a rigid-rodlike polymer (rod) under an external field, such as magnetic or electric fields. By taking into account two orientational order parameters of the rod and the LC, we define four nematic phases (N0, N1, N2, N3) on the temperature-concentration plane. Depending on the sign of the dielectric anisotropy Δεi of the rod (i = 1) and LC(i = 2), we examine the phase behavior of rod/LC mixtures in the case of Δε1 > 0, Δε2 > 0 (a), Δε1 < 0, Δε2 > 0 (b), Δε1 > 0, Δε2 < 0 (c), and Δε1 < 0, Δε2 < 0 (d). We predict a variety of phase separations induced by an external field.
Kinetic behavior of nitrogen penetration into indium double layer improving the smoothness of InN film
Authors: Huang Qiangcan , Li Shuping , Cai Duanjun , Kang Junyong
Published: June 2012

The kinetic process of the formation of InN thin film was clarified via the investigation of the layer-by-layer deposition on (0001) surface, by first-principles calculations. Site selection and diffusion behavior of In and N adatoms revealed an extraordinary growth kinetics. The indium bilayer preferably deposits in the initial stage and then the N atoms come up and penetrate vertically through a specific channel into between this double layer, finally forming the tetrahedral coordination of InN. Following this kinetic process, alternative pulse supply of precursors was proposed for the InN film growing and smoothening, which can effectively improve the surface smoothness.
Space charge corrected electron emission from an aluminum surface under non-equilibrium conditions
Authors: Wendelen W. , Mueller B. Y. , Autrique D. , Rethfeld B. , Bogaerts A.
Published: June 2012

A theoretical study has been conducted of ultrashort pulsed laser induced electron emission from an aluminum surface. Electron emission fluxes retrieved from the commonly employed Fowler-DuBridge theory were compared to fluxes based on a laser-induced non-equilibrium electron distribution. As a result, the two- and three-photon photoelectron emission parameters for the Fowler-DuBridge theory have been approximated. We observe that at regimes where photoemission is important, laser-induced electron emission evolves in a more smooth manner than predicted by the Fowler-DuBridge theory. The importance of the actual electron distribution decreases at higher laser fluences, whereas the contribution of thermionic emission increases. Furthermore, the influence of a space charge effect on electron emission was evaluated by a one dimensional particle-in-cell model. Depending on the fluences, the space charge reduces the electron emission by several orders of magnitude. The influence of the electron emission flux profiles on the effective electron emission was found to be negligible. However, a non-equilibrium electron velocity distribution increases the effective electron emission significantly. Our results show that it is essential to consider the non-equilibrium electron distribution as well as the space charge effect for the description of laser-induced photoemission.
An exact formalism to study the thermodynamic properties of hard-sphere systems under spherical confinement
Authors: Urrutia Ignacio , Castelletti Gabriela
Published: June 2012

This paper presents a modified grand canonical ensemble which provides a new simple and efficient scheme to study few-body fluid-like inhomogeneous systems under confinement. The new formalism is implemented to investigate the exact thermodynamic properties of a hard sphere (HS) fluid-like system with up to three particles confined in a spherical cavity. In addition, the partition function of this system was used to analyze the surface thermodynamic properties of the many-HS system and to derive the exact curvature dependence of both the surface tension and adsorption in powers of the density. The expressions for the surface tension and the adsorption were also obtained for the many-HS system outside of a fixed hard spherical object. We used these results to derive the dependence of the fluid-substrate Tolman length up to first order in density.
Nuclear charge-distribution effects on the NMR spectroscopy parameters
Authors: Maldonado Alejandro F. , Giménez Carlos A. , Aucar Gustavo A.
Published: June 2012

We present here a systematic study about the influence of the size and type of nuclear charge-distribution models (Gaussian and point-like) on the NMR spectroscopic parameters, the nuclear magnetic shielding σ and the indirect nuclear spin J-coupling. We found that relativistic effects largely enhance the nuclear charge-distribution effects (NChDE) on those parameters being them quite sensitive to the nuclear model adopted for calculations. Results for two rare gas atoms (Kr, Rn) and few molecular systems like HX, (X = Br, I, At), CH4, SnH4, SnIH3, SnI2H2, and PbIH3 are presented. J-couplings are more sensitive than shieldings in both, relativistic and non-relativistic (NR) regimes. The highest effect (close to 11% of variation in relativistic calculations with that two different nuclear models) is observed for J(Pb–I) in PbIH3. A similar effect is found for J(Pb–H) in the same molecule, close to 9%. The NChDE for σ(Sn) in SnI4−nHn with n = 1, 2 is as large as few ppm (between 3 and 8.56 ppm). For J(Sn–H) in this set of molecules, it goes from 37 Hz for SnH4 to 54 Hz for SnI2H2. Furthermore, we found that the vicinal NChDE is very small though not zero. For 1J(Sn–H) in SnIH3, the NChDE of iodine is close to 2 Hz (0.1%). We also studied the NChDE on the ground state electronic energies of atoms and molecules. We found that these effects are only important within the relativistic regime but not within the NR one. They are in good agreement with previous works.
Structural variation of hydrothermally synthesized KNbO3 nanowires
Authors: Joung Mi-Ri , Xu HaiBo , Kim Jin-Seong , Seo In-Tae , Nahm Sahn , Kang Jong-Yun , Yoon Seok-Jin
Published: June 2012

KNbO3 (KN) nanowires were synthesized using various process conditions and their structures and morphologies were investigated. Homogeneous KN nanowires were formed in specimens synthesized at 130 °C for 24.0–48.0 h. These KN nanowires have a tetragonal structure that is known to be stable at high temperatures in the range of 225–435 °C. Tetragonal KN nanowires changed to orthorhombic KN nanoplates when the process time increased and homogeneous orthorhombic KN nanoplates existed for specimens synthesized for 144.0 h. In addition, tetragonal and orthorhombic structures coexisted in KN nanoplates synthesized at 130 °C for 72.0 h. For specimens synthesized at 100 °C, a long process time of 144.0 h was required to develop homogeneous KN nanowires that were also considered to have both tetragonal and orthorhombic structures. On the other hand, for specimens synthesized at 150 °C for 8.0 h, KN nanowires and a cube-shaped KN phase coexisted. Furthermore, a K4Nb6O17 second phase was formed in specimens synthesized for short periods of time (<8.0 h), indicating that the formation of homogeneous KN nanowires is difficult at 150 °C. Therefore, homogeneous KN nanowires with a tetragonal structure can be obtained at a low temperature of 130 °C with a short process time in the range of 24.0–48.0 h.
The annealing mechanism of the radiation-induced vacancy-oxygen defect in silicon
Authors: Voronkov V. V. , Falster R. , Londos C. A.
Published: June 2012

Annealing experiments on the VO defect (the A-centre) produced by radiation in silicon—reported long ago—have been re-examined in order to deduce the two most important properties of VO: its diffusivity and the equilibrium constant for VO dissociation into V + O. The loss rate of VO is accounted for by two major reactions. One is the conventional reaction of the trapping of mobile VO by oxygen, thus producing VO2. The other is an annihilation of vacancies, which coexist in an equilibrium ratio with VO, by radiation-produced interstitial point defects. In some cases, a minor reaction, VO + V, should also be taken into account. The emerging minor defects V2O are also highly mobile. They partially dissociate back and partially get trapped by oxygen producing stable V2O2 defects.
Direct observation of inner and outer G′ band double-resonance Raman scattering in free standing graphene
Authors: Luo Zhiqiang , Cong Chunxiao , Zhang Jun , Xiong Qihua , Yu Ting
Published: June 2012

In contrary to the widely reported single and symmetric peak feature of G′ band in Raman spectrum of graphene, we herein report the observation of splitting in G′ band in free standing graphene. Our experimental findings provide a direct and strong support for the previous theoretical prediction that the coexistence of the outer and inner processes in the double-resonance Raman scattering would cause the splitting of G′ mode. The investigation of the influence of trigonal warping effect on the spectral features of G′ subbands further verified the theoretical interpretation established on the anisotropic electronic structure of graphene.
Crack-free InGaN multiple quantum wells light-emitting diodes structures transferred from Si (111) substrate onto electroplating copper submount with embedded electrodes
Authors: Chen Tufu , Wang Yunqian , Xiang Peng , Luo Ruihong , Liu Minggang , Yang Weimin , Ren Yuan , He Zhiyuan , Yang Yibin , Chen Weijie , Zhang Xiaorong , Wu Zhisheng , Liu Yang , Zhang Baijun
Published: June 2012

Crack-free InGaN multiple quantum wells (MQWs) light-emitting diodes with embedded electrode structures (EE-LEDs) were transferred from Si (111) substrate onto the electroplating copper submount. Crystalline quality was investigated by the high resolution x-ray diffraction (HR-XRD) measurement, in which no obvious deteriorations were found in the MQWs structure after the LEDs transferred from silicon substrate onto copper except for a partial residual strain relaxation in the film. The strain relaxation after silicon removal leads to a reduction in quantum confined stark effect (QCSE), which results in the enhancement of internal quantum efficiency (IQE). In comparison to the conventional LEDs on silicon substrate, the light output of the EE-LEDs on copper was enhanced by 122% at an injection current of 350 mA. Besides the enhancement of IQE, the improvement is also attributed to the following factors: the removal of the absorptive substrate, the inserting of the metal reflector between the EE-LEDs structure and the copper submount, the elimination of the electrode-shading, and the rough surface of the exposed AlN buffer layer.
Parameter estimation of the FitzHugh-Nagumo model using noisy measurements for membrane potential
Authors: Che Yanqiu , Geng Li-Hui , Han Chunxiao , Cui Shigang , Wang Jiang
Published: June 2012

This paper proposes an identification method to estimate the parameters of the FitzHugh-Nagumo (FHN) model for a neuron using noisy measurements available from a voltage-clamp experiment. By eliminating an unmeasurable recovery variable from the FHN model, a parametric second order ordinary differential equation for the only measurable membrane potential variable can be obtained. In the presence of the measurement noise, a simple least squares method is employed to estimate the associated parameters involved in the FHN model. Although the available measurements for the membrane potential are contaminated with noises, the proposed identification method aided by wavelet denoising can also give the FHN model parameters with satisfactory accuracy. Finally, two simulation examples demonstrate the effectiveness of the proposed method.
Graphene on Rh(111): Scanning tunneling and atomic force microscopies studies
Authors: Voloshina E. N. , Dedkov Yu. S. , Torbrügge S. , Thissen A. , Fonin M.
Published: June 2012

The electronic and crystallographic structure of the graphene/Rh(111) moiré lattice is studied via combination of density-functional theory calculations and scanning tunneling and atomic force microscopy (STM and AFM). Whereas the principal contrast between hills and valleys observed in STM does not depend on the sign of applied bias voltage, the contrast in atomically resolved AFM images strongly depends on the frequency shift of the oscillating AFM tip. The obtained results demonstrate the perspectives of application atomic force microscopy/spectroscopy for the probing of the chemical contrast at the surface.
Efficient manipulation of surface plasmon polariton waves in graphene
Authors: Ju Xu Hong , Bing Lu Wei , Zhu Wei , Gao Dong Zheng , Jun Cui Tie
Published: June 2012

The propagation of surface plasmon polariton (SPP) wave can be controlled by tunable graphene conductivity via electrostatic gating and/or chemical doping. Here, we propose an alternative way to manipulate the SPP waves efficiently by designing the thickness of dielectric cladding on the graphene. Meanwhile, the SPP wave properties can be changed gradually rather than abruptly through designing the topology of cladding. Compared to the traditional method, the proposed approach is more convenient for machining with lower scattering loss. A plasmonic Luneburg lens has been realized using this method, which opens a useful way to achieve the planar plasmonic devices.
Note: Modification of the Gay-Berne potential for improved accuracy and speed
Authors: Persson Rasmus A. X.
Published: June 2012

A modification of the Gay-Berne (GB) potential is proposed which is about 10% to 20% more speed efficient and statistically more accurate in reproducing the energy of interaction of two linear Lennard-Jones tetratomics when averaged over all orientations. For the special cases of end-to-end and side-by-side configurations, the new potential is equivalent to the GB one. A simple generalization to dissimilar particles of D∞h symmetry is presented but does not retain the superior agreement with respect to its GB counterpart, except at close range.
The Stream/Bounce Effect Occurs for Luminance- and Disparity-Defined Motion Targets
Authors: Grove Philip M , Kawachi Yousuke , Sakurai Kenzo
Published: June 2012

We generalised the stream/bounce effect to dynamic random element displays containing luminance- or disparity-defined targets. Previous studies investigating audio-visual interactions in this context have exclusively employed motion sequences with luminance-defined disks or squares and have focused on properties of the accompanying brief stimuli rather than the visual properties of the motion targets. We found that the presence of a brief sound temporally close to coincidence, or a visual flash at coincidence significantly promote bounce perception for motion targets defined by either luminance contrast or disparity contrast. A brief tone significantly promoted bouncing of luminance-defined targets above a no-sound baseline when it was presented at least 250 ms before coincidence and 100 ms after coincidence. A similar pattern was observed for disparity-defined targets, though the tone promoted bouncing above the no-sound baseline when presented at least 350 ms before and 300 ms after coincidence. We further explored the temporal properties of audio-visual interactions for these two display types and found that bounce perception saturated at similar durations after coincidence. The stream/bounce illusion manifests itself in dynamic random-element displays and is similar for luminance- and disparity-defined motion targets.
Simulated Angular Head Oscillation Enhances Vection in Depth
Authors: Kim Juno , Palmisano Stephen , Bonato Frederick
Published: June 2012

Research has shown that adding simulated linear head oscillation to radial optic flow displays enhances the illusion of self-motion in depth (ie linear vection). We examined whether this oscillation advantage for vection was due to either the added motion parallax or retinal slip generated by insufficient compensatory eye movement during display oscillation. We constructed radial flow displays which simulated 1 Hz horizontal linear head oscillation (generates motion parallax) or angular head oscillation in yaw (generates no motion parallax). We found that adding simulated angular or linear head oscillation to radial flow increased the strength of linear vection in depth. Neither type of simulated head oscillation significantly reduced vection onset latencies relative to pure radial flow. Simultaneous eye-movement recordings showed that slow-phase ocular following responses (OFRs) were induced in both linear and angular viewpoint oscillation conditions. Vection strength was significantly reduced by active central fixation when viewing displays which simulated angular, but not linear, head oscillation. When these displays with angular oscillation were viewed without stable fixation, vection strength was found to increase with the velocity and regularity of the OFR. We conclude that vection improvements observed during central viewing of displays with angular viewpoint oscillation depend on the generation of eye movements.
The Hierarchical Order of Processes Underlying the Direction Illusion and the Direction Aftereffect
Authors: Farrell-Whelan Max , Wenderoth Peter , Brooks Kevin R
Published: June 2012

Motion perception involves the processing of velocity signals through several hierarchical stages of the visual cortex. To better understand this process, a number of studies have sought to localise the neural substrates of two misperceptions of motion direction, the direction illusion (DI) and the direction aftereffect (DAE). These studies have produced contradictory evidence as to the hierarchical order of the processing stages from which the respective phenomena arise. We have used a simple stimulus configuration to further investigate the sequential order of processes giving rise to the DI and DAE. To this end, we measured the two phenomena invoked in combination, and also manually parsed this combined effect into its two constituents by measuring the two phenomena individually in both possible sequential orders. Comparing the predictions made from each order to the outcome from the combined effect allowed us to test the tenability of two models: the DAE-first model and the DI-first model. Our results indicate that DAE-invoking activity does not occur earlier in the motion processing hierarchy than DI-invoking activity. Although the DI-first model is not inconsistent with our data, the possible involvement of non-sequential processing may be better able to reconcile these results with those of previous studies.
Contributions of Visual and Embodied Expertise to Body Perception
Authors: Reed Catherine L , Nyberg Andrew A , Grubb Jefferson D
Published: June 2012

Recent research has demonstrated that our perception of the human body differs from that of inanimate objects. This study investigated whether the visual perception of the human body differs from that of other animate bodies and, if so, whether that difference could be attributed to visual experience and/or embodied experience. To dissociate differential effects of these two types of expertise, inversion effects (recognition of inverted stimuli is slower and less accurate than recognition of upright stimuli) were compared for two types of bodies in postures that varied in typicality: humans in human postures (human-typical), humans in dog postures (human-atypical), dogs in dog postures (dog-typical), and dogs in human postures (dog-atypical). Inversion disrupts global configural processing. Relative changes in the size and presence of inversion effects reflect changes in visual processing. Both visual and embodiment expertise predict larger inversion effects for human over dog postures because we see humans more and we have experience producing human postures. However, our design that crosses body type and typicality leads to distinct predictions for visual and embodied experience. Visual expertise predicts an interaction between typicality and orientation: greater inversion effects should be found for typical over atypical postures regardless of body type. Alternatively, embodiment expertise predicts a body, typicality, and orientation interaction: larger inversion effects should be found for all human postures but only for atypical dog postures because humans can map their bodily experience onto these postures. Accuracy data supported embodiment expertise with the three-way interaction. However, response-time data supported contributions of visual expertise with larger inversion effects for typical over atypical postures. Thus, both types of expertise affect the visual perception of bodies.
The Penny Drops: Change Blindness at Fixation
Authors: Smith Tim J , Lamont Peter , Henderson John M
Published: June 2012

Our perception of the visual world is fallible. Unattended objects may change without us noticing as long as the change does not capture attention (change blindness). However, it is often assumed that changes to a fixated object will be noticed if it is attended. In this experiment we demonstrate that participants fail to detect a change in identity of a coin during a magic trick even though eyetracking indicates that the coin is tracked by the eyes throughout the trick. The change is subsequently detected when participants are instructed to look for it. These results suggest that during naturalistic viewing, attention can be focused on an object at fixation without including all of its features.
A Comparative Study of Face Processing Using Scrambled Faces
Authors: Taubert Jessica , Aagten-Murphy David , Parr Lisa A
Published: June 2012

It is a widespread assumption that all primate species process faces in the same way because the species are closely related and they engage in similar social interactions. However, this approach ignores potentially interesting and informative differences that may exist between species. This paper describes a comparative study of holistic face processing. Twelve subjects (six chimpanzees Pan troglodytes and six rhesus monkeys Macaca mulatto) were trained to discriminate whole faces (faces with features in their canonical position) and feature-scrambled faces in two separate conditions. We found that both species tended to match the global configuration of features over local features, providing strong evidence of global precedence. In addition, we show that both species were better able to generalize from a learned configuration to an entirely novel configuration when they were first trained to match feature-scrambled faces compared to when they were trained with whole faces. This result implies that the subjects were able to access local information easier when facial features were presented in a scrambled configuration and is consistent with a holistic processing hypothesis. Interestingly, these data also suggest that, while holistic processing in chimpanzees is tuned to own-species faces, monkeys have a more general approach towards all faces. Thus, while these data confirm that both chimpanzees and rhesus monkeys process faces holistically, they also indicate that there are differences between the species that warrant further investigation.
Ambiguous Animals: Mutable Mammal Biases Bird
Authors: Wotton Janine M , Ferragamo Alys C
Published: June 2012

Ambiguous figures were primed with picture context, movement, and by presentation of a prior ambiguous figure. We tested two mammal/bird figures to determine if the multiple primes would add or interfere. Picture priming was effective for both figures but diminished with the presentation of a prior ambiguous figure. For the ‘swan/squirrel’ there was little movement priming. However, ‘rabbit/duck’ showed strong movement priming which cancelled the reducing effect of prior presentation and added to the picture effect.