bluuebunny/crossref_metadata_2025 huggingface dataset:
(P2-86) A Paradigm of Emergency Volunteering: The Case of a Remote Rural Area in Thailand
Authors: Chaleekrua T. , Phlainoi S.
Published: May 2011

Background

Changes in gender roles, the nature of the family, marriage patterns, political shifts, the nature of work, and the increase in the number and severity of emergencies are influencing volunteering and changing it in accordance with these changes. This study in a remote rural area in the north of Thailand explores paradigms of emergency volunteering in such areas based on the concept of the multi-paradigm model of volunteering.

Methods

A sample of twenty stakeholders: leaders, village health volunteers, the director of the local administrative organization and community heads provided data during in-depth interviews. Data were analyzed using content analysis.

Results

The results showed that the paradigms of emergency volunteering existing in the community were the functionalist paradigm and the interpreted paradigm. The functionalist paradigm relies on the belief in universal truths, thus emergency volunteering should be controlled and ordered. The community also believe that as a collective entity they achieve positive outcomes and benefits from emergency volunteering. In contrast, the interpreted paradigm relies on the belief in multiple truths. Thus emergency volunteering should be understood in terms of the individual experiences that emerge for each person from emergency volunteering. Furthermore, the community also believe that emergency volunteering should be focused on extracted cues and the process of helping emergency patients.

Conclusion

The conclusion of this study is that the management of emergency volunteering in the context of remote rural communities should be well ordered and be by consensus.
Introduction to a Special Issue on Electron Backscatter Diffraction
Authors: Deal Andrew
Published: May 2011

Arguably one of the most significant microscopy techniques of the past decade, electron backscatter diffraction (EBSD) has provided scientists and engineers with tremendous insight into the structure of crystalline materials. What started with basic observations of electron diffraction in the middle of the 20th century has grown into a mature technology that bridges the gap between the macro and micro length scales. EBSD has found a home in both the materials science and geological communities characterizing crystallographic texture and preferred orientations, residual strain, grain boundary character and networks, and identifying constituent phases. Advancements in computational power, camera technology, indexing algorithms, sample preparation, and dynamical simulations have made this possible.
Changing contributions of different agricultural policy instruments to global reductions in trade and welfare
Authors: CROSER JOHANNA , ANDERSON KYM
Published: May 2011

Trade negotiators and policy advisors are keen to know the relative contributions of different farm policy instruments to international trade and economic welfare. Nominal rates of assistance or producer support estimates are incomplete indicators, especially when (as in many developing countries) some commodities are taxed and others are subsidized, in which case positive contributions can offset negative contributions. This paper develops and estimates a new set of more-satisfactory partial equilibrium indicators of the relative contribution of different farm policy instruments to reductions in agricultural trade and welfare. It does so by drawing on the trade restrictiveness index literature and a recently compiled database on distortions to agricultural prices for 75 developing and high-income countries over the period 1960 to 2004. Results confirm earlier findings that border taxes are the dominant instrument affecting global trade and welfare, but they also suggest declines in export taxes contributed nearly as much as cuts in import protection to the trade and welfare effects of agricultural policy reforms since the 1980s.
Mapping potential foodsheds in New York State by food group: An approach for prioritizing which foods to grow locally
Authors: Peters Christian J. , Bills Nelson L. , Lembo Arthur J. , Wilkins Jennifer L. , Fick Gary W.
Published: May 2011

Public interest in local food continues to grow, but few analyses have examined the capacity for the US population to be supplied through local and regional food systems. This paper extends earlier work that demonstrated a method for mapping potential foodsheds and estimating the potential for New York to meet the food needs of the state's population centers. It provides a methodology for addressing the question, ‘If land is limited, which foods should be grown locally?’ A spatial model was developed to allocate the available agricultural land of New York State (NYS) to meet in-state food needs for six distinct food groups (grains, vegetables, fruits, dairy, meat and eggs) across the eight largest population centers. An optimization routine was used to allocate land to maximize economic land use value (LUV). Eleven scenarios were examined, ranging from a baseline level of consumption of New York produced foods to a 100% local diet. Across the 11 scenarios, the amount of food supplied, the LUV attained, and the area of land allocated increased as the ‘willingness’ to consume local products increased. This approach dictated that land was preferentially devoted to higher-value food groups relative to lower-value groups, and no scenario used all available land. Under the 100% local scenario, 69% of total food needs (on a fresh weight basis) were supplied in-state with an average food distance of 238 km. This scenario provided food from only four of the six groups, namely, dairy, eggs, fruit and vegetables. These results suggest that a much larger proportion of total food needs (on a weight basis) might be provided from in-state production than was found in previous work. LUV serves as a compelling optimization function, and future work should investigate the degree to which maximizing returns to land complements or conflicts with social and environmental goals of local and regional food systems.
Potential and limitations of organic and fair trade cotton for improving livelihoods of smallholders: evidence from Central Asia
Authors: Bachmann Felicitas
Published: May 2011

Cotton is a leading agricultural non-food commodity associated with soil degradation, water pollution and pesticide poisoning due to high levels of agrochemical inputs. Organic farming is often promoted as a means of addressing the economic, environmental and health risks of conventional cotton production, and it is slowly gaining ground in the global cotton market. Organic and fair trade cotton are widely seen as opportunities for smallholder farmers to improve their livelihoods thanks to higher returns, lower input costs and fewer risks. Despite an increasing number of studies comparing the profitability of organic and non-organic farming systems in developing and industrialized countries, little has been published on organic farming in Central Asia. The aim of this article is to describe the economic performance and perceived social and environmental impacts of organic cotton in southern Kyrgyzstan, drawing on a comparative field study conducted by the author in 2009. In addition to economic and environmental aspects, the study investigated farmers’ motivations toward and assessment of conversion to organic farming. Cotton yields on organic farms were found to be 10% lower, while input costs per unit were 42% lower; as a result, organic farmers’ cotton revenues were 20% higher. Due to lower input costs as well as organic and fair trade price premiums, the average gross margin from organic cotton was 27% higher. In addition to direct economic benefits, organic farmers enjoy other benefits, such as easy access to credit on favorable terms, provision of uncontaminated cottonseed cooking oil and cottonseed cake as animal feed, and marketing support as well as extension and training services provided by newly established organic service providers. The majority of organic farmers perceive improved soil quality, improved health conditions, and positively assess their initial decision to convert to organic farming. The major disadvantage of organic farming is the high manual labor input required. In the study area, where manual farm work is mainly women's work and male labor migration is widespread, women are most affected by this negative aspect of organic farming. Altogether, the results suggest that, despite the inconvenience of a higher workload, the advantages of organic farming outweigh its disadvantages and that conversion to organic farming improves the livelihoods of small-scale farmers.
T-EQUIVALENCES FOR POSITIVE SENTENCES
Authors: CIEŚLIŃSKI CEZARY
Published: May 2011

Answering a question formulated by Halbach (2009), I show that a disquotational truth theory, which takes as axioms all positive substitutions of the sentential T-schema, together with all instances of induction in the language with the truth predicate, is conservative over its syntactical base.
A complete high‐resolution Paleocene benthic stable isotope record for the central Pacific (ODP Site 1209)
Authors: Westerhold Thomas , Röhl Ursula , Donner Barbara , McCarren Heather K. , Zachos James C.
Published: May 2011

We have compiled the first stratigraphically continuous high‐resolution benthic foraminiferal stable isotope record for the Paleocene from a single site utilizing cores recovered at Pacific ODP Site 1209. The long‐term trend in the benthic isotope record suggests a close coupling of volcanic CO2 input and deep‐sea warming. Over the short‐term the record is characterized by slow excursions with a pronounced periodic beat related to the short (100 kyr) and long (405 kyr) eccentricity cycle. The phase relationship between the benthic isotope record and eccentricity is similar to patterns documented for the Oligocene and Miocene confirming the role of orbital forcing as the pace maker for paleoclimatic variability on Milankovitch time scales. In addition, the record documents an unusual transient warming of 2°C coeval with a 0.6‰ carbon isotope excursion and a decrease in carbonate content at 61.75 Ma. This event, which bears some resemblance to Eocene hyperthermals, marks the onset of a long‐term decline in δ13C. The timing indicates it might be related to the initiation of volcanism along Greenland margin.
Weak turbulence theory of the nonlinear evolution of the ion ring distribution
Authors: Mithaiwala M. , Rudakov L. , Ganguli G. , Crabtree C.
Published: May 2011

The nonlinear evolution of an ion ring instability in a low β magnetospheric plasma is considered. The evolution of the two-dimensional ring distribution is essentially quasilinear. Ignoring nonlinear processes the timescale for the quasilinear evolution is the same as for the linear instability 1/1τQL~γLτQL~γL. However, when nonlinear processes become important, a new timescale becomes relevant to the wave saturation mechanism. Induced nonlinear scattering of the lower-hybrid waves by plasma electrons is the dominant nonlinearity relevant for plasmas in the inner magnetosphere and typically occurs on the timescale 1/1τNL~ω(M/m)W/WnTnTτNL~ω(M/m)W/WnTnT, where W is the wave energy density, nT is the thermal energy density of the background plasma, and M/Mmm is the ion to electron mass ratio, which has the consequence that the wave amplitude saturates at a low level, and the timescale for quasilinear relaxation is extended by orders of magnitude.
Increased laser-accelerated proton energies via direct laser-light-pressure acceleration of electrons in microcone targets
Authors: Gaillard S. A. , Kluge T. , Flippo K. A. , Bussmann M. , Gall B. , Lockard T. , Geissel M. , Offermann D. T. , Schollmeier M. , Sentoku Y. , Cowan T. E.
Published: May 2011

We present experimental results showing a laser-accelerated proton beam maximum energy cutoff of 67.5 MeV, with more than 5 × 106 protons per MeV at that energy, using flat-top hollow microcone targets. This result was obtained with a modest laser energy of ∼80 J, on the high-contrast Trident laser at Los Alamos National Laboratory. From 2D particle-in-cell simulations, we attribute the source of these enhanced proton energies to direct laser-light-pressure acceleration of electrons along the inner cone wall surface, where the laser light wave accelerates electrons just outside the surface critical density, in a potential well created by a shift of the electrostatic field maximum with respect to that of the magnetic field maximum. Simulations show that for an increasing acceleration length, the continuous loading of electrons into the accelerating phase of the laser field yields an increase in high-energy electrons.
On the control of spin flop in synthetic antiferromagnetic films
Authors: Negulescu B. , Lacour D. , Hehn M. , Gerken A. , Paul J. , Duret C.
Published: May 2011

The paper presents a systematic study of anneal induced anisotropies in a CoFe/Ru/CoFe synthetic antiferromagnet (SAF) exchange coupled with an IrMn film. When the annealing is done with the SAF in a spin flop state, the magnetic layers can be pinned perpendicular to the annealing field direction. The main parameters controlling this process are identified and analyzed: the value and the direction of the annealing field along with the Ruderman-Kittel-Kasuya-Yosida coupling energy between the two ferromagnetic layers. The induced anisotropy is predicted within a theoretical model taking into account the thermal variation of the coupling constants. Finally, the spin flop annealing is used to orthogonally pin the reference and the detection electrodes in an IrMn/CoFe/Ru/CoFe/Cu/CoFe/IrMn spin valve structure. The magnetoresistance variation in this structure is analyzed as a function of the pinning direction of the SAF acquired during the annealing in the spin flop state. A very good agreement is observed between the experimental and theoretically predicted responses.
Scaling of normalized mean energy and scalar dissipation rates in a turbulent channel flow
Authors: Abe Hiroyuki , Antonia Robert Anthony
Published: May 2011

Non-dimensional parameters for the mean energy and scalar dissipation rates Cɛ and Cɛθ are examined using direct numerical simulation (DNS) data obtained in a fully developed turbulent channel flow with a passive scalar (Pr = 0.71) at several values of the Kármán (Reynolds) number h+. It is shown that Cɛ and Cɛθ are approximately equal in the near-equilibrium region (viz., y+ = 100 to y/h = 0.7) where the production and dissipation rates of either the turbulent kinetic energy or scalar variance are approximately equal and the magnitudes of the diffusion terms are negligibly small. The magnitudes of Cɛ and Cɛθ are about 2 and 1 in the logarithmic and outer regions, respectively, when h+ is sufficiently large. The former value is about the same for the channel, pipe, and turbulent boundary layer, reflecting the similarity between the mean velocity and temperature distributions among these three canonical flows. The latter value is, on the other hand, about twice as large as in homogeneous isotropic turbulence due to the existence of the large-scale u structures in the channel. The behaviour of Cɛ and Cɛθ impacts on turbulence modeling. In particular, the similarity between Cɛ and Cɛθ leads to a simple relation for the scalar variance to turbulent kinetic energy time-scale ratio, an important ingredient in the eddy diffusivity model. This similarity also yields a relation between the Taylor and Corrsin microscales and analogous relations, in terms of h+, for the Taylor microscale Reynolds number and Corrsin microscale Peclet number. This dependence is reasonably well supported by both the DNS data at small to moderate h+ and the experimental data of Comte-Bellot [Ph. D. thesis (University of Grenoble, 1963)] at larger h+. It does not however apply to a turbulent boundary layer where the mean energy dissipation rate, normalized on either wall or outer variables, is about 30% larger than for the channel flow.
A stochastic extension of the approximate deconvolution model
Authors: Adams Nikolaus A.
Published: May 2011

The approximate deconvolution model (ADM) for large-eddy simulation exploits a range of represented but non-resolved scales as buffer region for emulating the subgrid-scale energy transfer. ADM can be related to Langevin models for turbulence when filter operators are interpreted as stochastic kernel estimators. The main conceptual difference between ADM and Langevin models for turbulence is that the former is formulated with respect to an Eulerian reference frame whereas the latter are formulated with respect to a Lagrangian reference frame. This difference can be resolved by transforming the Langevin models to the Eulerian reference frame. However, the presence of a stochastic force prevents the classical convective transformation from being applicable. It is shown that for the transformation a stochastic number-density field can be introduced that essentially represents the Lagrangian particle distribution of the original model. Unlike previous derivations, the number-density field is derived by invoking the δ-function calculus, and for the resulting stochastic-momentum-field transport equation implies the necessity of a repulsive force in order to maintain a unique mapping between Lagrangian and Eulerian frame. Based on the number-density field and the stochastic-momentum field, a stochastic modification of ADM is possible by an approximate reconstruction of the small-scale field on the above-mentioned range of buffer scales. The objective of this paper is to introduce the concept of the Eulerian formulation of the Langevin model in a consistent form, allowing for stable numerical integration and to show how this model can be used for a modified way of subfilter-scale estimation. It should be noted that the overall concept can be applied more generally to any situation where a Lagrangian Langevin model is used. For an initial verification of the concept, which is within the scope of this paper, we consider the example of compressible isotropic turbulence and that of the three-dimensional Taylor-Green-Vortex.
Nanopatterning of Si surfaces by normal incident ion erosion: Influence of iron incorporation on surface morphology evolution
Authors: Zhou Jing , Facsko Stefan , Lu Ming , Möller Wolfhard
Published: May 2011

The surface morphology of Si(100) induced by 1200 eV Ar+ ion bombardment at normal incidence with and without Fe incorporation is presented. The formation of nanodot patterns is observed only when the stationary Fe areal density in the surface is above a threshold value of 8×1014 cm-2. This result is interpreted in terms of an additional surface instability due to locally nonuniform sputtering in connection with the presence of a Fe rich amorphous phase at the peak of the nanodots. At Fe concentrations below the threshold, smoothing dominates and pattern formation is inhibited. The transition from a k-2 to a k-4 behavior in the asymptotic power spectral density function supports the conclusion that under these conditions ballistic smoothing and ion-enhanced viscous flow are the two dominant mechanisms of surface relaxation.
Influence of the block hydrophilicity of AB2 miktoarm star copolymers on cluster formation in solutions
Authors: Han Minwoo , Hong Minhyung , Sim Eunji
Published: May 2011

We investigated the formation of various micelle shapes of lipid-like amphiphilic AB2 miktoarm star copolymers in a solution, by performing dissipative particle dynamics simulations. AB2 miktoarm star copolymer molecules are modeled with coarse-grained structures that consist of a relatively hydrophilic head (A) group with a single arm and a hydrophobic tail (B) group with double arms. A decrease in the hydrophilicity of the head group leads to a reduction of the polymer-solvent contact area, causing cluster structure changes from spherical micelles to vesicles. Consequently, a spherical exterior with multi-lamellar or cylindrical phase interior structures forms under poor solvent conditions without the introduction of spherical hard-wall containers. Furthermore we observed that, for small head group lengths, vesicles were formed in much wider range of solvent-head interaction strength than for long head groups, indicating that molecules with short head group offer a superior vesicle forming property. A phase diagram, the structure and kinetics of the cluster formation, a density profile, and a detailed shape analysis are presented to discuss the molecular characteristics of potential candidates for drug carriers that require superior and versatile vesicle forming properties. We also show that, under certain solvent-hydrophilic head group interaction conditions, initially formed cylindrical micelles transform to bilayer fragments through redistribution of copolymers within the cluster.
Terahertz generation by nonlinear mixing of laser pulses in a clustered gas
Authors: Kumar Manoj , Tripathi V. K.
Published: May 2011

A scheme of terahertz (THz) generation by two collinear laser pulses of finite spot size in a clustered gas is investigated theoretically. The lasers quickly ionize the atoms of the clusters, converting them into plasma balls, and exert a ponderomotive force on the cluster electrons, producing a beat frequency longitudinal current of limited transverse extent. The current acts as an antenna to produce beat frequency terahertz radiation. As the cluster expands under the hydrodynamic pressure, plasma frequency of cluster electrons ωpe decreases and approaches 3 times the frequency of laser, resonant heating and expansion of clusters occurs. On further expansion of clusters as ωpe approaches 3 times the terahertz frequency, resonant enhancement in THz radiated power occurs.
Application of tomographic particle image velocimetry to studies of transport in complex (dusty) plasma
Authors: Williams Jeremiah D.
Published: May 2011

Over the past twelve years, two-dimensional and stereoscopic particle image velocimetry (PIV) techniques have been used to obtain detailed measurements of the thermal and transport properties of the microparticle component of dusty plasma systems. This letter reports on an extension of these techniques to obtain a volumetric, three-dimensional velocity vector measurement using tomographic PIV. Initial measurements using the tomographic PIV diagnostic are presented.
Limiting effects on laser compression by resonant backward Raman scattering in modern experiments
Authors: Yampolsky Nikolai A. , Fisch Nathaniel J.
Published: May 2011

Through resonant backward Raman scattering, the plasma wave mediates the energy transfer between long pump and short seed laser pulses. These mediations can result in pulse compression at extraordinarily high powers. However, both the overall efficiency of the energy transfer and the duration of the amplified pulse depend upon the persistence of the plasma wave excitation. At least with respect to the recent state-of-the-art experiments, it is possible to deduce that at present the experimentally realized efficiency of the amplifier is likely constrained mainly by two effects, namely, the pump chirp and the plasma wave wavebreaking.
Molecular dynamics simulation study of nonconcatenated ring polymers in a melt. I. Statics
Authors: Halverson Jonathan D. , Lee Won Bo , Grest Gary S. , Grosberg Alexander Y. , Kremer Kurt
Published: May 2011

Molecular dynamics simulations were conducted to investigate the structural properties of melts of nonconcatenated ring polymers and compared to melts of linear polymers. The longest rings were composed of N = 1600 monomers per chain which corresponds to roughly 57 entanglement lengths for comparable linear polymers. For the rings, the radius of gyration squared, \documentclass[12pt]{minimal}\begin{document}$\langle R_g^2 \rangle$\end{document}⟨Rg2⟩, was found to scale as N4/5 for an intermediate regime and N2/3 for the larger rings indicating an overall conformation of a crumpled globule. However, almost all beads of the rings are “surface beads” interacting with beads of other rings, a result also in agreement with a primitive path analysis performed in the next paper [J. D. Halverson, W. Lee, G. S. Grest, A. Y. Grosberg, and K. Kremer, J. Chem. Phys. 134, 204905 (2011)]10.1063/1.3587138. Details of the internal conformational properties of the ring and linear polymers as well as their packing are analyzed and compared to current theoretical models.
Inverse spin-Hall effect induced by spin pumping in metallic system
Authors: Ando K. , Takahashi S. , Ieda J. , Kajiwara Y. , Nakayama H. , Yoshino T. , Harii K. , Fujikawa Y. , Matsuo M. , Maekawa S. , Saitoh E.
Published: May 2011

The inverse spin-Hall effect (ISHE) induced by the spin pumping has been investigated systematically in simple ferromagnetic/paramagnetic bilayer systems. The spin pumping driven by ferromagnetic resonance injects a spin current into the paramagnetic layer, which gives rise to an electromotive force transverse to the spin current using the ISHE in the paramagnetic layer. In a Ni81Fe19/Pt film, we found an electromotive force perpendicular to the applied magnetic field at the ferromagnetic resonance condition. The spectral shape of the electromotive force is well reproduced using a simple Lorentz function, indicating that the electromotive force is due to the ISHE induced by the spin pumping; extrinsic magnetogalvanic effects are eliminated in this measurement. The electromotive force varies systematically by changing the microwave power, magnetic-field angle, and film size, being consistent with the prediction based on the Landau–Lifshitz–Gilbert equation combined with the models of the ISHE and spin pumping. The electromotive force was observed also in a Pt/Y3Fe4GaO12 film, in which the metallic Ni81Fe19 layer is replaced by an insulating Y3Fe4GaO12 layer, supporting that the spin-pumping-induced ISHE is responsible for the observed electromotive force.
Double diffusive convection in a porous layer saturated with viscoelastic fluid using a thermal non-equilibrium model
Authors: Kumar Anoj , Bhadauria B. S.
Published: May 2011

In this paper, a study of double diffusive convection in an anisotropic porous layer, saturated with viscoelastic fluid, heated form below, and cooled from above, has been performed; the fluid and solid phases are not in thermal equilibrium. Extended Darcy model, which includes the time derivative term in the momentum equation, has been used. For the fluid and solid phase temperature fields, a two-field model has been used separately for energy equation. Linear stability analysis is performed, using normal mode technique, and the expression for Rayleigh number has been obtained. It is found that small inter-phase heat coefficient has substantial effect on the stability of the system. The criterion for both stationary and oscillatory convection is derived analytically. The effects of various parameters on the stability of the system have been investigated. A weak nonlinear stability analysis based on the truncated representation of Fourier series is performed to find Nusselt number and Sherwood number. Further, we studied the transient behavior of the Nusselt number and Sherwood number by solving the finite amplitude equations using a numerical method. The results obtained during the analysis have been presented graphically. A study of streamlines, isotherms, and isohalines has been also made for fluid and solid phases.
Edge states in a boundary layer
Authors: Cherubini S. , Palma P. De , Robinet J.-Ch. , Bottaro A.
Published: May 2011

The understanding of laminar-turbulent transition in shear flows has recently progressed along new paradigms based on the central role of nonlinear exact coherent states. We follow such paradigms to identify, for the first time in a spatially developing flow, localized flow structures living on the edge of chaos, which are the precursors of turbulence. These coherent structures are constituted by hairpin vortices and streamwise streaks. The results reported here extend the dynamical systems description of transition to spatially developing flows.
The additional symmetries for the BTL and CTL hierarchies
Authors: Cheng Jipeng , Tian Kelei , He Jingsong
Published: May 2011

In this paper, we construct the additional symmetries for the Toda lattice hierarchies of B type and C type (the BTL and CTL hierarchies), and show their algebraic structures are \documentclass[12pt]{minimal}\begin{document}$w_\infty ^B\times w_\infty ^B$\end{document}w∞B×w∞B and \documentclass[12pt]{minimal}\begin{document}$w_\infty ^C\times w_\infty ^C$\end{document}w∞C×w∞C , respectively. And also we discuss the generating functions of the additional symmetries.
Adiabatic versus diabatic descriptions of the lowest Rydberg and valence $1^\Sigma ^{+}$Σ+1 states of HCl
Authors: Lefebvre-Brion H. , Liebermann H. P. , Vázquez G. J.
Published: May 2011

In this contribution we first report new ab initio self–consistent field configuration interaction calculations of the first excited adiabatic potential of 1Σ+ symmetry, the 21Σ+ or B1Σ+ state, which presents two minima and can thus be seen as made up of the Rydberg E1Σ+ and the valence V1Σ+ states. Based on the computed 21Σ+ potential, we devised a theoretical procedure to compute the vibronic structure in order to try to explain the energy levels observed in the region above 76 254.4 cm−1 which display an irregular vibrational structure, indicative of spectral perturbations. We try to find out which representation of the electronic states, the diabatic or the adiabatic one, is best suited to replicate the lowest observed vibronic levels of the E and V states. To this end, we deduce, from the 21Σ+ potential and its complementary adiabatic potential, two diabatic potentials. We then carry out a coupled equation treatment based on these diabatic potentials. The results of this treatment indicate that, in the present case, the adiabatic representation is better than the diabatic one to describe the observed vibronic levels. This is due, as expected, to the existence of a strong electrostatic interaction between the two diabatic potentials.
Close pairs of relative equilibria for identical point vortices
Authors: Dirksen Tobias , Aref Hassan
Published: May 2011

Numerical solution of the classical problem of relative equilibria for identical point vortices on the unbounded plane reveals configurations that are very close to the analytically known, centered, symmetrically arranged, nested equilateral triangles. New numerical solutions of this kind are found for 3n + 1 vortices, where n = 2, 3, ..., 30. A sufficient, although apparently not necessary, condition for this phenomenon of close solutions is that the “core” of the configuration is marginally stable, as occurs for a central vortex surrounded by an equilateral triangle. The open, regular heptagon also has this property, and new relative equilibria close to the nested, symmetrically arranged, regular heptagons have been found. The centered regular nonagon is also marginally stable. Again, a new family of close relative equilibria has been found. The closest relative equilibrium pairs occur, however, for symmetrically nested equilateral triangles.
A unique vibrational signature of rotated water monolayers on Pt(111): Predicted and observed
Authors: Feibelman Peter J. , Kimmel Greg A. , Smith R. Scott , Petrik Nikolay G. , Zubkov Tykhon , Kay Bruce D.
Published: May 2011

Six H-bonds in the periodic di-interstitial structure that accounts for scanning tunneling microscope images of “$\sqrt {37}$37” and “$\sqrt {39}$39” wetting layers on Pt(111) are some 0.2 Å shorter than H-bonds are in ice Ih. According to a broadly obeyed correlation, this density functional theory result implies a stringent test of the di-interstitial motif, namely the presence of an OH-stretch band red-shifted from that of ice Ih by more than 1000 cm−1. Infrared absorption spectra satisfy the test, in showing a feature centered at about 1965 cm−1, which grows in as deposited water orders.
Temperature-dependent thermal conductivity of bent carbon nanotubes by molecular dynamics simulation
Authors: Huang Zhengxing , Tang Zhen’an , Yu Jun , Bai Suyuan
Published: May 2011

Molecular dynamics simulations were performed to evaluate temperature-dependent thermal conductivity of bent carbon nanotubes. Thermal conductivities of bent nanotubes are predicted to be smaller than those of straight nanotubes. This is due to the suppression of high frequency phonons from the density of states calculations. It was found that for the defect-free bent nanotubes, the ratio of thermal conductivity of bent nanotubes to that of the straight ones are temperature and diameter independent, while significantly relies on the bent characteristic size. The more is the nanotube bent, the smaller is thermal conductivity obtained. For the larger nanotubes, the buckled defects were observed after bending and the ratio decrease rapidly. The ratios of thermal conductivity of the buckled nanotubes to that of the straight ones increase with the increasing temperatures until a maximum is obtained.
In-situ observation of non-hemispherical tip shape formation during laser-assisted atom probe tomography
Authors: Koelling S. , Innocenti N. , Schulze A. , Gilbert M. , Kambham A. K. , Vandervorst W.
Published: May 2011

It is shown by SEM imaging of the tip and by observing the emission pattern of the evaporated atoms that laser assisted evaporation in an atom probe can lead to nonhemispherical tip shapes and time-dependent nonuniform emission. We have investigated this nonuniformity by observing the change in field of view when using laser wavelengths of 515 nm and 343 nm on silicon. The change is monitored in situ by 0.5 nm thick silicon oxide. We demonstrate that the field of view can easily be changed by more than 10 nm and that the apparent oxide layer thickness can deviate substantially from its correct value. The dependence of the tip shape deformations and the reconstruction artifacts on the laser wavelength are explained through simulations of the laser-tip interaction and nonhomogeneous heating effects.
The effect of chromium impurity on the thermoelectric properties of PbTe in the temperature range 100–600 K
Authors: Paul Biplab , Banerji P.
Published: May 2011

In this work we have investigated the effect of the chromium (Cr) impurity on the thermoelectric properties of lead telluride (PbTe) bulk crystal with different Cr-content. The structural characterization of the crystals was done by x-ray diffraction and high-resolution transmission electron microscopic analyses. The incorporation of Cr in PbTe over the soluble limit has been found to replace Pb from the lattice site, forcing it to be precipitated into nanodots, with their dimensions in the range of 2–13 nm and their numbers increasing with the increase in Cr doping. The transport properties of the samples with different Cr-content have been evaluated through temperature dependent electrical resistivity, the Hall coefficient, and thermopower measurements in the temperature range of 100–600 K. The highest mobility is obtained as 1404 cm2/V s for a sample with a carrier concentration of 3.84 × 1018 cm−3 at 300 K. The high electron mobility and moderately higher value of the thermopower are expected to produce a high power factor of the samples with the highest value of 38.49 × 10−4 Wm−1K−2 in a specimen with a Cr-content of 1.45 at. % at room temperature. The power factor of the specimen with 1.3 at. % Cr-content is found to be above 29 × 10−4 Wm−1K−2 in the wide temperature range of 300–600 K.
Observation of exclusively He-induced H emission in cooled laser plasma
Authors: Lie Z. S. , Niki H. , Kagawa K. , Tjia May On , Hedwig R. , Pardede M. , Jobiliong E. , Suliyanti M. M. , Abdulmadjid S. N. , Kurniawan K. H.
Published: May 2011

An experiment was performed for the observation of H emission induced in a cooled laser-induced atmospheric pressure gas plasma of He atoms in their metastable excited state. The strong H emission detected clearly established, to the exclusion of other well known major excitation processes, the exclusive contribution of the He-induced excitation (HIE) mechanism. The process is suggested to take place by means of energy transfer from the excited He atoms to the H atoms via Penning collision induced ionization involving electron exchange. The result further shows that this mechanism may also work for elements other than H and thereby strongly suggests the use of ambient He gas to broaden and complement the applications of standard laser-induced breakdown spectroscopy.
Photoelectron imaging spectroscopy and theoretical investigation of ZrSi
Authors: Gunaratne K. Don Dasitha , Hazra Anirban , Castleman A. W.
Published: May 2011

The photoelectron spectrum of ZrSi− has been measured at two different photon energies: 2.33 eV and 3.49 eV, providing electron binding energy and photoelectron angular distribution information. The obtained vertical detachment energy of ZrSi− is 1.584(14) eV. The neutral ground and excited state terms are assigned based on experimental and theoretical results. The ground state of ZrSi is tentatively assigned as a 3Σ+ state with a configuration of 1σ2 1π4 1δ0 2σ1 3σ1. A low lying 3Πi neutral excited state is identified to be 0.238 eV (1919 cm−1) above the ground state. The anion ground state is designated as a 2Σ+ state with a 1σ2 1π4 1δ0 2σ2 3σ1 valence electron configuration. A Franck-Condon (FC) simulation of the photoelectron spectrum has been carried out. For the 3Σ+ ← 2Σ+ band, theoretically calculated bond lengths and frequencies are used in the FC calculation which give good agreement with experiment, while for the 3Πi ← 2Σ+ band, the ZrSi bond length is estimated from the FC spectrum. Comparisons are made with previously published theoretical studies and inconsistencies are pointed out. To the best of our knowledge, this study provides the first spectroscopic information on the transition metal-silicon diatomic, ZrSi.
Monte Carlo simulations of charged dendrimer-linear polyelectrolyte complexes and explicit counterions
Authors: Kłos J. S. , Sommer J.-U.
Published: May 2011

We study complexes composed of one dendrimer of generation G = 4 (G4 dendrimer) with Nt = 32 charged terminal groups and an oppositely charged linear polyelectrolyte accompanied by neutralizing counterions in an athermal solvent using Monte Carlo simulations based on the bond fluctuation model. In our study both the full Coulomb potential and the excluded volume interactions are taken into account explicitly with the reduced temperature τ and the chain length Nch as the main simulation parameters. Our calculations indicate that there exist three temperature ranges that determine the behavior of such complexes. At τcomplex stable charged dendrimer-linear polyelectrolyte complexes are formed first, which are subsequently accompanied by selective counterion localization within the complex interior at τloc ⩽ τcomplex, and counterion condensation as temperature is further decreased below τcond < τloc. In particular, we observe that condensation takes place exclusively on the excess charges in the complex and thus no condensation is observed at the compensation point (Nch = Nt), irrespective of τ. For Nch ≠ Nt the complex is overally charged. Furthermore, we discuss the size and structure of the dendrimer and the linear polyelectrolyte within the complex, as well as spatial distributions of monomers and counterions. Conformations of the chain in the bound state are analysed in terms of loops, trains, and tails.
Nanostructures in a binary mixture confined in slit-like pores with walls decorated with tethered polymer brushes in the form of stripes: Dissipative particle dynamics study
Authors: Ilnytskyi Jaroslav M. , Patsahan Taras , Sokołowski Stefan
Published: May 2011

Using dissipative particle dynamics, we investigate the behavior of a binary mixture, exhibiting demixing in a bulk phase, confined in slit-like pores with walls modified by the stripes of tethered brush of chains. Our main interest is to determine possible morphologies that can be formed inside the pore, depending on the geometrical parameters characterizing the system (the size of the pore and the width of the stripes). In order to describe the observed morphologies we calculate several characteristics, as the density and local temperature profiles, the radii of gyration for the attached polymers, and the minimum polymer-polymer distances in the direction parallel and perpendicular to the pore walls. The summary of our findings is presented as a sketch of the diagram of morphologies.
Atomistic study of electronic structure of PbSe nanowires
Authors: Paul Abhijeet , Klimeck Gerhard
Published: May 2011

Lead Selenide (PbSe) is an attractive ‘IV-VI’ semiconductor material to design optical sensors, lasers, and thermoelectric devices. Improved fabrication of PbSe nanowires (NWs) enables the utilization of low dimensional quantum effects. The effect of cross-section size (W) and channel orientation on the band structure of PbSe NWs is studied using an 18 band sp3d5 tight-binding theory. The band gap increases almost with the inverse of the W for all the orientations indicating weak symmetry dependence. [111] and [110] NWs show higher ballistic conductance for the conduction and valence band compared to [100] NWs due to the significant splitting of the projected L-valleys in [100] NWs.
Significant ferrimagnetism observed in Aurivillius Bi4Ti3O12 doped by antiferromagnetic LaFeO3
Authors: Wu Fei-Xiang , Chen Zhong , Chen Y. B. , Zhang Shan-Tao , Zhou Jian , Zhu Yong-Yuan , Chen Yan-Feng
Published: May 2011

Highly crystalline quality c-axis epitaxial nLaFeO3–Bi4Ti3O12 (n=0.5,1.0,1.5) thin films were deposited on SrTiO3 (001) substrates by pulsed laser deposition. The x-ray diffraction and transmission electron microscopy characterizations confirm that there are designed even-odd number perovskite-block structures in n=0.5 and 1.5 films while it has even-even number ones in n=1.0 films. The remarkable physical property of n=0.5 and 1.5 samples is the presence of ferrimagnetism even up to room temperature. While it is antiferromagentic property in n=1.0 sample. The observed ferrimagentism is explained qualitatively by considering the crystal structure in nLaFeO3–Bi4Ti3O12.
Electronic structure of Pt based topological Heusler compounds with C1b structure and “zero band gap”
Authors: Ouardi Siham , Shekhar Chandra , Fecher Gerhard H. , Kozina Xeniya , Stryganyuk Gregory , Felser Claudia , Ueda Shigenori , Kobayashi Keisuke
Published: May 2011

Besides of their well-known wide range of properties it was recently shown that many of the heavy Heusler semiconductors with 1:1:1 composition and C1b structure exhibit a zero band gap behavior and are topological insulators induced by their inverted band structure. In the present study, the electronic structure of the Heusler compounds PtYSb and PtLaBi was investigated by bulk sensitive hard x-ray photoelectron spectroscopy. The measured valence band spectra are clearly resolved and in well agreement to the first-principles calculations of the electronic structure of the compounds. The experimental results give clear evidence for the zero band gap state.
Magnetoresistance origin in martensitic and austenitic phases of Ni2Mn1+xSn1−x
Authors: Singh Sandeep , Biswas C.
Published: May 2011

The magnetoresistance (MR) of Ni2Mn1+xSn1−x (0.40≤x≤0.52) is studied as functions of temperature and magnetic field in austenitic and martensitic phases. The maximum MR obtained is −36% (x=0.4) at 170 K with 7 T magnetic field during martensitic transition. The MR in the martensitic phase (maximum −2.2%) is less than that in austenitic phase (maximum −4.6%). The origin of less MR below and above martensitic transition is understood through the experimental data fitting with magnetic field dependence (Hn) of MR.
Polarized photoluminescence from single wurtzite InP/InAs/InP core-multishell nanowires
Authors: Masumoto Yasuaki , Hirata Yuuki , Mohan Premila , Motohisa Junichi , Fukui Takashi
Published: May 2011

The photoluminescence from single InP/InAs/InP core-multishell nanowires (CMNs) was highly linearly polarized in perpendicular to the nanowire long axis. Taking account of dielectric confinement of light field, we found the internal optical dipole squared perpendicular to the nanotube long axis d0x2 is larger than that parallel to the axis d0z2 by two orders of magnitude. With the increase in the thickness of InAs nanotubes, the ratio β=d0x2/d0z2 increases. This strong anisotropy in β comes from nearly perfect wurtzite structure of InP/InAs/InP CMNs and small inclusion of pz-character into the Γ7(B)-hole state.
Protein's electronic polarization contributes significantly to its catalytic function
Authors: Xiang Yun , Duan Lili , Zhang John Z. H.
Published: May 2011

Ab initio quantum mechanical/molecular mechanical method is combined with the polarized protein-specific charge to study the chemical reactions catalyzed by protein enzymes. Significant improvement in the accuracy and efficiency of free-energy simulation is demonstrated by calculating the free-energy profile of the primary proton transfer reaction in triosephosphate isomerase. Quantitative agreement with experimental results is achieved. Our simulation results indicate that electronic polarization makes important contribution to enzyme catalysis by lowering the energy barrier by as much as 3 kcal/mol.
Unidirectional channel-drop filter by one-way gyromagnetic photonic crystal waveguides
Authors: Fu Jin-Xin , Lian Jin , Liu Rong-Juan , Gan Lin , Li Zhi-Yuan
Published: May 2011

We theoretically and experimentally study the side coupling between guided modes and cavity modes in a one-way waveguide that is composed of a regular photonic crystal and a gyromagnetic photonic crystal. At the cavity resonant wavelength, the backward mode can be completely blocked while the forward mode is only slightly influenced in the transmissivity for a specially designed waveguide. This unique light transport property can be exploited to construct a unidirectional band stop filter and a unidirectional channel-drop filter that can selectively process a light signal propagating only along a particular direction.
Laser emission with excitonic gain in a ZnO planar microcavity
Authors: Guillet T. , Brimont C. , Valvin P. , Gil B. , Bretagnon T. , Médard F. , Mihailovic M. , Zúñiga-Pérez J. , Leroux M. , Semond F. , Bouchoule S.
Published: May 2011

The lasing operation of a ZnO planar microcavity under optical pumping is demonstrated from T=80 to 300 K. At the laser threshold, the cavity switches from the strong coupling to the weak coupling regime. A gain-related transition, which appears while still observing polariton branches and, thus, with stable excitons, is observed below 240 K. This shows that exciton scattering processes, typical of II-VI semiconductors, are involved in the gain process.
Tensile strained SiGe quantum well infrared photodetectors based on a light-hole ground state
Authors: Rauter P. , Mussler G. , Grützmacher D. , Fromherz T.
Published: May 2011

We report the fabrication and thorough characterization of tensile strained p-type SiGe quantum well infrared photodetectors (QWIPs) grown on a Si0.74Ge0.26 pseudosubstrate. The QWIPs operate from a light-hole (LH) ground state and feature responsivity peaks in both the terahertz and mid-infrared regimes with responsivity values up to 3.7 mA/W, originating from LH–LH, LH–heavy-hole, and LH–split-off-band transitions.
Mapping piezoelectric nonlinearity in the Rayleigh regime using band excitation piezoresponse force microscopy
Authors: Griggio F. , Jesse S. , Kumar A. , Marincel D. M. , Tinberg D. S. , Kalinin S. V. , Trolier-McKinstry S.
Published: May 2011

Band excitation piezoresponse force microscopy enables local investigation of the nonlinear piezoelectric behavior of ferroelectric thin films. However, the presence of additional nonlinearity associated with the dynamic resonant response of the tip-surface junction can complicate the study of a material’s nonlinearity. Here, the relative importance of the two nonlinearity sources was examined as a function of the excitation function. It was found that in order to minimize the effects of nonlinear tip-surface interactions but achieve good signal to noise level, an optimal excitation function must be used.