bluuebunny/crossref_metadata_2025 huggingface dataset:
The Current Scheme to Manage Migration between Europe and Cape Verde: Promoter of Development or Tool for Border Closure?
Authors: Pina‐Delgado José
Published: April 2013

This paper analyses cooperation between Europe and Cape Verde in the field of migration policy. Such cooperation fits into a broader trend that sees migrant‐receiving countries engage in agreements with sending states, in a way that is expected to bring together Western states' concerns with the control of migration and less‐developed countries' needs in terms of development aid and access to regular migration opportunities. The Republic of Cape Verde has signed and is negotiating several treaties and arrangements, especially with the European Union and its member states. A key factor here is Cape Verde's long‐standing reliance on emigration and the consequently problematic reduction of emigration opportunities in a world that is closing its borders to foreign (regular) workforce. A closer look at the cooperation dynamics between sending and receiving countries reveals, however, that management schemes are potentially biased in favour of developed countries, which would then use them to secure the cooperation of sending and/or transit countries to their own political objectives. The purpose of this paper is therefore to assess whether traditional emigration countries such as Cape Verde can reasonably expect such bilateral regimes of migration management to fit their interests or if this kind of cooperation will merely establish a basis for supporting European Union‐driven political agenda. Copyright © 2013 John Wiley & Sons, Ltd.
Effect of Resveratrol on Cultured Skin Fibroblasts from Patients with Oxidative Phosphorylation Defects
Authors: De Paepe Boel , Vandemeulebroecke Katrien , Smet Joél , Vanlander Arnaud , Seneca Sara , Lissens Willy , Van Hove Johan LK , Deschepper Ellen , Briones Paz , Van Coster Rudy
Published: April 2013

Few therapeutic options are available to patients with oxidative phosphorylation disorders. Administering pharmacological agents that are able to stimulate mitochondrial biogenesis have been put forward as a possible treatment, yet the approach remains in need of thorough testing. We investigated the effect of resveratrol in an in vitro setting. Mitochondrial enzymatic activities were tested in cultured skin fibroblasts from patients harboring a nuclear defect in either complex II or complex IV (n = 11), and in fibroblasts from healthy controls (n = 11). In the latter, preincubation with resveratrol resulted in a significant increase of citrate synthase, complex II and complex IV enzyme activity. In patients with complex II or complex IV deficiency, however, activity of the deficient complex could not be substantially augmented, and response was dependent upon the residual activity. We conclude that resveratrol is not capable of normalizing oxidative phosphorylation activities in deficient cell lines. Copyright © 2013 John Wiley & Sons, Ltd.
INITIAL MOTION AND BEDLOAD TRANSPORT DISTANCE DETERMINED BY PARTICLE TRACKING IN A LARGE REGULATED RIVER
Authors: May C. L. , Pryor B. S.
Published: April 2013

Reservoir releases on large regulated rivers are increasingly being used to rejuvenate riverine habitat downstream of dams. Determining the effective flow level is complicated by the trade‐off between mobilizing bed particles and retaining coarse sediment in rivers with low sediment supply. This study determined mobilization and transport distance of bed particles using motion‐sensing radio transmitting particles that approximated the reach‐average D84 grain size. The distribution of shear stress at initial motion varied substantially between flood events, and suggests that the sequence of flood events and the history of under‐threshold flows may be an important determinant of bed strength and thus particle mobility. In addition, particle activity was greatest on the rising limb of each flood and was maximized at near bankfull flow. Travel distances did not vary between floods when scaled by transport event duration, and a negative exponential distribution was a good fit to the data. Results of this study provide important insight into individual particle movement, which can be used to inform flow releases and understand the effects of flood magnitude on particle mobility and transport. Copyright © 2013 John Wiley & Sons, Ltd.
Bayesian modeling and inference for clinical trials with partial retrieved data following dropout
Authors: Chen Qingxia , Chen Ming‐Hui , Ohlssen David , Ibrahim Joseph G.
Published: April 2013

In randomized clinical trials, it is common that patients may stop taking their assigned treatments and then switch to a standard treatment (standard of care available to the patient) but not the treatments under investigation. Although the availability of limited retrieved data on patients who switch to standard treatment, called off‐protocol data, could be highly valuable in assessing the associated treatment effect with the experimental therapy, it leads to a complex data structure requiring the development of models that link the information of per‐protocol data with the off‐protocol data. In this paper, we develop a novel Bayesian method to jointly model longitudinal treatment measurements under various dropout scenarios. Specifically, we propose a multivariate normal mixed‐effects model for repeated measurements from the assigned treatments and the standard treatment, a multivariate logistic regression model for those stopping the assigned treatments, logistic regression models for those starting a standard treatment off protocol, and a conditional multivariate logistic regression model for completely withdrawing from the study. We assume that withdrawing from the study is non‐ignorable, but intermittent missingness is assumed to be at random. We examine various properties of the proposed model. We develop an efficient Markov chain Monte Carlo sampling algorithm. We analyze in detail via the proposed method a real dataset from a clinical trial. Copyright © 2013 John Wiley & Sons, Ltd.
Mesoporous Silica Nanoparticles Act as a Self‐Adjuvant for Ovalbumin Model Antigen in Mice
Authors: Mahony Donna , Cavallaro Antonino S. , Stahr Frances , Mahony Timothy J. , Qiao Shi Zhang , Mitter Neena
Published: April 2013

Immunization to the model protein antigen ovalbumin (OVA) is investigated using MCM‐41 mesoporous silica nanoparticles as a novel vaccine delivery vehicle and adjuvant system in mice. The effects of amino surface functionalization and adsorption time on OVA adsorption to nanoparticles are assessed. Amino‐functionalized MCM‐41 (AM‐41) shows an effect on the amount of OVA binding, with 2.5‐fold increase in binding capacity (72 mg OVA/g AM‐41) compared to nonfunctionalized MCM‐41 (29 mg OVA/g MCM‐41). Immunization studies in mice with a 10 μg dose of OVA adsorbed to AM‐41 elicits both antibody and cell‐mediated immune responses following three subcutaneous injections. Immunizations at a lower 2 μg dose of OVA adsorbed to AM‐41 particles results in an antibody response but not cell‐mediated immunity. The level of antibody responses following immunization with nanoformulations containing either 2 μg or 10 μg of OVA are only slightly lower than that in mice which receive 50 μg OVA adjuvanted with QuilA, a crude mixture of saponins extracted from the bark of the Quillaja saponaria Molina tree. This is a significant result, since it demonstrates that AM‐41 nanoparticles are self‐adjuvanting and elicit immune responses at reduced antigen doses in vivo compared to a conventional delivery system. Importantly, there are no local or systemic negative effects in animals injected with AM‐41. Histopathological studies of a range of tissue organs show no changes in histopathology of the animals receiving nanoparticles over a six week period. These results establish the biocompatible MCM‐41 silica nanoparticles as a new method for vaccine delivery which incorporates a self‐adjuvant effect.
Selective inhibition of phosphodiesterase 5 enhances glutamatergic synaptic plasticity and memory in mice
Authors: Uthayathas Subramaniam , Parameshwaran Kodeeswaran , Karuppagounder Senthilkumar S. , Ahuja Manuj , Dhanasekaran Muralikrishnan , Suppiramaniam Vishnu
Published: April 2013

Phosphodiesterases (PDEs) belong to a family of proteins that control metabolism of cyclic nucleotides. Targeting PDE5, for enhancing cellular function, is one of the therapeutic strategies for male erectile dysfunction. We have investigated whether in vivo inhibition of PDE5, which is expressed in several brain regions, will enhance memory and synaptic transmission in the hippocampus of healthy mice. We have found that acute administration of sildenafil, a specific PDE5 inhibitor, enhanced hippocampus‐dependent memory tasks. To elucidate the underlying mechanism in the memory enhancement, effects of sildenafil on long‐term potentiation (LTP) were measured. The level of LTP was significantly elevated, with concomitant increases in basal synaptic transmission, in mice treated with sildenafil (1 mg/kg/day) for 15 days compared to control mice. These results suggest that moderate PDE5 inhibition enhances memory by increasing synaptic plasticity and transmission in the hippocampus. Synapse 67:741–747, 2013. © 2013 Wiley Periodicals, Inc.
Synthesis and Characterisation of Sigma‐ and Pi‐Bonded Metallaphosphacarboranes
Authors: McLellan Ross , Bailo Marta , Ellis David , Rosair Georgina M. , Welch Alan J.
Published: April 2013

Two new metallaphosphacarboranes have been synthesised from [7, 8‐nido‐CPB9H11]– by deprotonation followed by treatment with a metal fragment. Starting with [HNMe3][7, 8‐nido‐CPB9H11] deprotonation and reaction with a source of {(indenyl)Co}2+ affords the η‐bonded cobaltaphosphacarborane 3‐(η‐C9H7)‐3,1,2‐closo‐CoCPB9H10 (1) the first “half‐sandwich“ 3,1,2‐metallaphosphacarborane. The indenyl ligand conformation in 1 (cisoid between the indenyl bridgehead carbon atoms and cage heteroatoms, with the cage carbon atom lying below the indenyl C–C bond) reveals that the structural trans effect in a phosphacarborane ligand is weakest for carbon and therefore varies in the order B > P > C. Starting with [HNC5H11][7, 8‐nido‐CPB9H11] deprotonation and reaction with half an equivalent of [Ru(p‐cymene)Cl2]2 affords the σ‐bonded ruthenaphosphacarborane 8‐{Ru(p‐cymene)Cl(C5H11N)}‐7, 8‐nido‐CPB9H11 (2), the first example of a molecule with a phosphacarborane σ‐bonded to a metal to be crystallographically characterised.
The type 2 anti‐Müllerian hormone receptor has splice variants that are dominant‐negative inhibitors
Authors: Imhoff Floriane M. , Yang Dee , Mathew Suneeth F. , Clarkson Andrew N. , Kawagishi Yui , Tate Warren P. , Koishi Kyoko , McLennan Ian S.
Published: April 2013

Anti‐Müllerian hormone (AMH) has both paracrine and hormonal actions that occur at different AMH concentrations, and in cells with different densities of its specific receptor (Amhr2). This diversity is not explained by canonical AMH signaling. We report that Amhr2 has two splice variants: Amhr2Δ2 (AMH binding site) and Amhr2Δ9/10 (kinase domain). Both spliced variants inhibit AMH signaling in a reporter assay. The mRNA for the spliced variants was relatively less abundant than Amhr2 mRNA in all tissues. This suggests that the physiological function(s) of the receptor variants may be restricted to specific cellular/subcellular sites and/or to the transport of AMH.
Integration durch Sport – Ein quartiersbezogener Ansatz
Authors: Gieß-Stüber Petra , Tausch Berndt , Baumgartner Juliane
Published: April 2013

Einleitung

Im Freizeit- und Breitensport werden humanitäre und wohlfahrtsorientierte sozialpolitische Ziele verfolgt, die eine gesamtgesellschaftliche Integration durch die Teilhabe am Sport anstreben. Gleichberechtigte Partizipation von Migranten ist jedoch nicht selbstverständlich. Soziale Integration ist ein komplexes Geschehen, das interkulturelle Kompetenz, aufsuchende pädagogische Arbeit und strukturelle Öffnung voraussetzt. Die Bedeutung stadtteilbezogener Intervention und gezielter pädagogischer Maßnahmen sowie deren Umsetzung werden anhand des Freiburger Mädchenfußballprojekts „kick for girls“ aufgezeigt.
Leicht erhöhte Transaminasen
Authors: Krähenbühl Stephan
Published: April 2013

Erhöhte Transaminasen bei asymptomatischen Patienten kommen bei über 5 % der Untersuchungen vor. Wenn nicht offensichtliche Gründe vorliegen, sollte der Befund innerhalb der nächsten 3 Monate bestätigt werden. Häufige Ursachen sind nicht-alkoholische Fettleber (NAFLD), nicht-alkoholische Steatohepatitis (NASH), Alkohol, Virushepatitiden, Hämochromatose und Medikamente oder Toxine. Seltener sind Autoimmunhepatitis, M. Wilson und alpha1-Antitrypsinmangel. Daneben gibt es auch nicht hepatische Ursachen wie Sprue oder Hämolyse und Myopathien bei alleiniger Erhöhung der ASAT. Es wird ein zweiteiliger Abklärungsvorgang vorgeschlagen, in dem zuerst die häufigsten Ursachen gesucht und allenfalls therapeutisch angegangen werden, bevor die selteneren Ursachen abgeklärt werden. Die Wertigkeit der Untersuchungsmethoden wird diskutiert.
All astrocytes are not created equal—the role of astroglia in brain injury
Authors: Moore Darcie L , Jessberger Sebastian
Published: April 2013

In two recent papers published in Nature Neuroscience and Cell Stem Cells, Magdalena Götz and colleagues shed new light on the in vivo response of glial cells to brain injury and characterize a highly heterogeneous behavior of astrocytes to chronic and acute brain injury.
Grain size effect on magnetic properties of REMnO3 (RE = Pr, Nd)
Authors: Dyakonov V. , Bażela W. , Duraj R. , Dul M. , Kravchenko Z. , Zubov E. , Dyakonov K. , Baran S. , Szytuła A. , Szymczak H.
Published: April 2013

X-ray diffraction and magnetic using dc and ac methods measurements of the polycrystalline and nanosize REMnO3 (RE = Pr, Nd) powdered samples have been performed. The nanosize manganites were synthesized with a sol-gel method at different (800, 850 and 900 °C) temperatures. The average size of synthesized nanoparticles (from 56 to 89 nm) and polycrystalline powders (above 200 nm) was estimated using the x-ray diffraction data. All the compounds studied crystallize in the orthorhombic crystal structure (space group Pnma) at room temperature with smaller values of the lattice parameters in the nanosamples. The temperature-dependent ac magnetic susceptibilities show a sharp high-temperature peak connected with Mn magnetic moments ordering. The low-temperature maximum of magnetic susceptibility is proposed to be due to the polarization of the rare-earth sublattice by an effective exchange field of the Mn ordered sublattice. The antiferromagnetic ordering of Mn sublattice and paramagnetic Curie temperatures as well as the magnetic moment values for the nanosize samples was found to be smaller than those for polycrystalline sample.
Experimental observation of spontaneous spin polarization of electrons in hybridized states of transition element impurities in semiconductors
Authors: Okulov V. I. , Govorkova T. E. , Zhevstovskikh I. V. , Lonchakov A. T. , Okulova K. A. , Pamyatnykh E. A. , Podgornykh S. M. , Andriichuk M. D. , Paranchich L. D.
Published: April 2013

Experimental evidence of the possible existence of spontaneous spin polarization of the electron system in hybridized states formed by transition element impurity atoms in the conduction band of semiconducting crystals is examined. The details of a quantitative interpretation of experiments on the temperature dependence of the specific heat and elastic moduli of mercury selenide crystals with iron impurities confirm the feasibility of establishing the presence of electron spin polarization in this type of experiment, as well as the possible existence of polarization in the crystals studied here. Theoretical arguments support the observation of a thermodynamic anomalous Hall effect owing to spontaneously polarized donor electrons from low-concentration impurities.
Controllable light filters using an all-solid-state switchable mirror with a Mg-Ir thin film for preterm infant incubators
Authors: Tajima Kazuki , Shimoike Mika , Li Heng , Inagaki Masumi , Izumi Hitomi , Akiyama Misaki , Matsushima Yukiko , Ohta Hidenobu
Published: April 2013

We have fabricated a controllable light filter using an all-solid-state switchable mirror incorporating a Mg-Ir thin film for use in preterm infant incubators. The solid-state switchable mirror device was fabricated by depositing a multilayer on a glass substrate. The mixed hydride of MgH2 and Mg6Ir2H11 created from the Mg-Ir thin film is red in the transparent state. The optical switching speeds between the reflective and transparent red states depended on applied voltage. The device showed three states, namely, reflective, black, and transparent red, due to the properties of the switchable mirror material. These results suggest that the material could be used as a controllable light filter for preterm infant incubators, since it eliminates the light wavelength that disturbs regular sleep-wake cycles of preterm infants.
Local Marchenko-Pastur law at the hard edge of sample covariance matrices
Authors: Cacciapuoti Claudio , Maltsev Anna , Schlein Benjamin
Published: April 2013

Let XN be a N × N matrix whose entries are independent identically distributed complex random variables with mean zero and variance \documentclass[12pt]{minimal}\begin{document}$\frac{1}{N}$\end{document}1N. We study the asymptotic spectral distribution of the eigenvalues of the covariance matrix \documentclass[12pt]{minimal}\begin{document}$X_N^*X_N$\end{document}XN*XN for N → ∞. We prove that the empirical density of eigenvalues in an interval [E, E + η] converges to the Marchenko-Pastur law locally on the optimal scale, \documentclass[12pt]{minimal}\begin{document}$N \eta /\sqrt{E} \gg (\log N)^b$\end{document}Nη/E≫(logN)b, and in any interval up to the hard edge, \documentclass[12pt]{minimal}\begin{document}$\frac{(\log N)^b}{N^2}\lesssim E \le 4-\kappa$\end{document}(logN)bN2≲E≤4−κ, for any κ > 0. As a consequence, we show the complete delocalization of the eigenvectors.
Applied magnetic field design for the field reversed configuration compression heating experiment
Authors: Domonkos M. T. , Amdahl D. , Camacho J. F. , Coffey S. K. , Degnan J. H. , Delaney R. , Frese M. , Gale D. , Grabowski T. C. , Gribble R. , Intrator T. P. , McCullough J. , Montano N. , Robinson P. R. , Wurden G.
Published: April 2013

Detailed calculations of the formation, guide, and mirror applied magnetic fields in the FRC compression-heating experiment (FRCHX) were conducted using a commercially available generalized finite element solver, COMSOL Multiphysics®. In FRCHX, an applied magnetic field forms, translates, and finally captures the FRC in the liner region sufficiently long to enable compression. Large single turn coils generate the fast magnetic fields necessary for FRC formation. Solenoidal coils produce the magnetic field for translation and capture of the FRC prior to liner implosion. Due to the limited FRC lifetime, liner implosion is initiated before the FRC is injected, and the magnetic flux that diffuses into the liner is compressed. Two-dimensional axisymmetric magnetohydrodynamic simulations using MACH2 were used to specify optimal magnetic field characteristics, and this paper describes the simulations conducted to design magnetic field coils and compression hardware for FRCHX. This paper presents the vacuum solution for the magnetic field.
An excess current in Bi2223–Ag contacts above the critical temperature
Authors: Dyachenko A. I. , Tarenkov V. Yu. , Sidorov S. L. , Varyukhin V. N. , Soloviev A. L.
Published: April 2013

In contacts normal metal–superconductor Bi1.6Pb0.4Sr1.8Ca2.2Cu3O10 (Bi2223), the energy gap Δ(T) of the superconductor and the excess current Iexc(T) were measured by means of the Andreev spectroscopy. It is shown that the parameter Δ(T) turns to zero at the superconducting transition temperature of the cuprate, Tc ≈ 110 K, and the dependence Δ(T) follows the BCS theory; at the same time, the excess current Iexc(T) persists up to the temperature Tpair ≈ 180 K, significantly higher than Tc. The result obtained indicates a possible existence in Bi2223 of a wide temperature range Tc < T < Tpair where a condensate of Cooper pairs starts to form.
Magnetic properties of Ce3+ ion in iron-containing oxypnictide CeFeAsO
Authors: Gornostaeva O. V. , Lamonova K. V. , Orel S. M. , Pashkevich Yu. G.
Published: April 2013

Magnetic properties of a Ce3+ ion in two crystallographic phases of a nonsuperconducting oxipnictide CeFeAsO were studied. Ce3+-ion energy levels, g-factor values, temperature dependences of magnetic susceptibility components and the forth-order anisotropy constant were calculated within a modified crystal field approach. It was shown that in the tetragonal and orthorhombic phases, the easy direction for the magnetic moment of Ce3+ ions corresponds to [110] axis. Comparison of the calculated temperature dependences of susceptibility components to the respective experimental data showed that at temperatures below 100 K, it is necessary to take into account the internal field produced by the magnetic subsystem of iron ions.
Surface magnetic anisotropy of CoFe2O4 nanoparticles with a giant low-temperature hysteresis
Authors: Mozul' K. A. , Ol'khovik L. P. , Sizova Z. I. , Bludov A. N. , Pashchenko V. A. , Baumer V. N. , Vashchenko V. V. , Kolosov M. O. , Kryshtal' A. P. , Prodanov M. F.
Published: April 2013

Ferrimagnetic nanoparticles of CoFe2O4 about 4–16 nm in diameter were synthesized by pyrolysis of a mixture of Fe and Co acetylacetonates. The field dependences of magnetization and hysteresis loops were investigated in magnetic fields up to 4000 kA/m at various temperatures from 4.2 to 500 K. A considerable contribution, positive or negative depending on the temperature, of “surface” anisotropy to the effective magnetic anisotropy of the nanoparticles was observed. A correlation was found between the magnetic properties that represent the specificity of small particles, namely, between “surface” anisotropy, magnetization, and high-field susceptibility.
Improvements to Kramers turnover theory
Authors: Pollak Eli , Ankerhold Joachim
Published: April 2013

The Kramers turnover problem, that is, obtaining a uniform expression for the rate of escape of a particle over a barrier for any value of the external friction was solved in the 1980s. Two formulations were given, one by Mel'nikov and Meshkov (MM) [V. I. Mel'nikov and S. V. Meshkov, J. Chem. Phys. 85, 1018 (1986)10.1063/1.451844], which was based on a perturbation expansion for the motion of the particle in the presence of friction. The other, by Pollak, Grabert, and Hänggi (PGH) [E. Pollak, H. Grabert, and P. Hänggi, J. Chem. Phys. 91, 4073 (1989)10.1063/1.456837], valid also for memory friction, was based on a perturbation expansion for the motion along the collective unstable normal mode of the particle. Both theories did not take into account the temperature dependence of the average energy loss to the bath. Increasing the bath temperature will reduce the average energy loss. In this paper, we analyse this effect, using a novel perturbation theory. We find that within the MM approach, the thermal energy gained from the bath diverges, the average energy gain becomes infinite implying an essential failure of the theory. Within the PGH approach increasing the bath temperature reduces the average energy loss but only by a finite small amount of the order of the inverse of the reduced barrier height. Then, this does not seriously affect the theory. Analysis and application for a cubic potential and Ohmic friction are presented.
Thermally induced solid-solid structural transition of copper nanoparticles through direct geometrical conversion
Authors: Cheng Bingqing , Ngan Alfonso H. W.
Published: April 2013

Molecular dynamics simulations of small Cu nanoparticles using three different interatomic potentials at rising temperature indicate that small nanoparticles can undergo solid-solid structural transitions through a direct geometrical conversion route. The direct geometrical conversion can happen for cuboctahedral nanoparticles, which turn into an icosahedra shape: one diagonal of the square faces contracts, and the faces are folded along the diagonal to give rise to two equilateral triangles. The transition is a kinetic process that cannot be fully explained through an energetic point of view. It has low activation energy and fast reaction time in the simulations. The transition mechanism is via the transmission of shear waves initiated from the particle surface and does not involve dislocation activity.
Computing the phase diagram of binary mixtures: A patchy particle case study
Authors: Rovigatti Lorenzo , de las Heras Daniel , Tavares José Maria , Telo da Gama Margarida M. , Sciortino Francesco
Published: April 2013

We investigate the phase behaviour of 2D mixtures of bi-functional and three-functional patchy particles and 3D mixtures of bi-functional and tetra-functional patchy particles by means of Monte Carlo simulations and Wertheim theory. We start by computing the critical points of the pure systems and then we investigate how the critical parameters change upon lowering the temperature. We extend the successive umbrella sampling method to mixtures to make it possible to extract information about the phase behaviour of the system at a fixed temperature for the whole range of densities and compositions of interest.
Prediction of channel flow characteristics through square arrays of emergent cylinders
Authors: Ben Meftah M. , Mossa M.
Published: April 2013

This paper describes a theoretical approach of turbulent flow in an infinite square array of emergent cylinders distributed uniformly along a channel bottom. Laboratory experiments were carried out to investigate the flow velocity characteristics in order to confirm this theoretical approach. A model array of vertical, rigid, circular, and threaded steel cylinders, of regular distribution, was mounted on the bed of a recirculating hydraulic channel. Measurements of the three-dimensional flow velocity components were carried out using a 3D acoustic Doppler velocimeter. At a certain distance downstream of a lateral row of cylinders, the transversal profiles of velocities and turbulence parameters are expected to be periodic functions in the lateral position whose period is the centre-to-centre spacing of two side-by-side cylinders. Some empirical expressions for predicting the turbulent flow features have been established. The formulation proposed is consistent with the experimental data over a certain range of the Reynolds number based on the cylinder diameter. In addition, a new formula to estimate the bulk drag coefficient $\overline {C_D }$CD¯ of the array of cylinders is proposed and validated.
Valence photoelectron spectra of alkali bromides calculated within the propagator theory
Authors: Karpenko Alexander , Iablonskyi Denys , Aksela Helena
Published: April 2013

The valence ionization spectra covering the binding energy range 0–45 eV of alkali bromide XBr (X = Li, Na, K, Rb) vapors are studied within the framework of the propagator theory. Relativistic Algebraic Diagrammatic Construction calculations have been carried out in order to investigate photoionization processes and to describe molecular electronic structure. Theoretical results are compared with available experimental data.
Improved molecular constants of the 000-000 band of the electronic transition A2Σ+-X2Π of N2O+ radical
Authors: Fellows C. E.
Published: April 2013

In this paper the 000-000 vibrational band of the electronic transition A2Σ+-X2Π of the N2O+ radical is analyzed, through high resolution Fourier Transform spectroscopy. The N2O+ radical was produced by Penning ionization of N2O by colliding with metastable atoms of He(23S) in a vacuum chamber. The spectrum was recorded in a spectral range of 24 500-30 000 cm−1 and obtained from 200 coadded interferograms recorded at an apodized resolution of 0.08 cm−1. Through a recursive way, the wavenumbers of the correspondent rotational transitions were reduced into molecular constants. A total of 280 lines were adjusted to the model with a standard deviation of 0.006 cm−1.
Line-mixing in absorption bands of linear molecules diluted in high-density rare gases: Measurements and modeling for OCS-He
Authors: Buldyreva Jeanna V. , Gennadiev Nikolai A. , Filippov Nikolai N.
Published: April 2013

Absorption coefficients in the bending ν2 and stretching 2ν3 bands of OCS perturbed by He at high pressures up to 300 atm have been measured and analyzed in the impact-approximation region by two theoretical models accounting for the line mixing. In the first approach, the frequency-independent relaxation operator is treated semi-classically [N. N. Filippov and M. V. Tonkov, J. Quant. Spectrosc. Radiat. Transf. 50, 111 (1993)10.1016/0022-4073(93)90134-4] with adiabatic corrections. To characterize the strength of collisions and the line mixing efficiency a single parameter G is used and its value is estimated from the intermolecular interaction potential. The adiabaticity of collisions and the corresponding correction to the collisional cross sections amplitude are taken into account by two other parameters νcorr and σ deduced from fitting to experimental line widths. In the second approach, the symmetrized non-Markovian relaxation operator of Energy-Corrected Sudden type developed for rototranslational Raman spectra of linear rotators [J. Buldyreva and L. Bonamy, Phys. Rev. A 60, 370 (1999)10.1103/PhysRevA.60.370] and satisfying all the basic properties (in particular, the detailed balance relation and the double-sided sum rules) is adapted to absorption spectra for the first time. Its off-diagonal elements are determined via the common adiabaticity factor and the basic transition rates whose parameters are adjusted on experimental values of isolated line widths. Both models provide a very consistent description of OCS-He 2ν3 and ν2 band intensities up to the maximal experimentally studied pressure, with a slightly more realistic picturing of the inter-branch exchange by the second approach.
Recursive procedures for Krall-Sheffer operators
Authors: Fordy Allan P. , Scott Michael J.
Published: April 2013

We consider the Krall-Sheffer class of admissible, partial differential operators in the plane. We concentrate on algebraic structures, such as the role of commuting operators and symmetries. For the polynomial eigenfunctions, we give explicit forms of the 3-level recurrence relations and differential raising operators, which are shown to satisfy unusual commutation relations. We present new generating functions for two of the cases.
Generalized Gibbs’ approach in heterogeneous nucleation
Authors: Abyzov Alexander S. , Schmelzer Jürn W. P.
Published: April 2013

Heterogeneous nucleation (condensation and boiling) on planar solid surfaces is described taking into account changes of the state parameters of the critical clusters in dependence on supersaturation. The account of the variation of the state parameters of the cluster phase on nucleation is performed in the framework of the generalized Gibbs’ approach. One-component van der Waals fluids are chosen as a model for the analysis of the basic qualitative characteristics of the process. The analysis is performed for both hydrophobic and hydrophilic surfaces and similarities and differences between condensation and boiling processes are discussed for the two different cases. It is shown that, in the generalized Gibbs’ approach, contact angle and catalytic factor for heterogeneous nucleation become dependent on the degree of metastability (undercooling or superheating) of the fluid. For the case of formation of a droplet in supersaturated vapor on a hydrophobic surface and bubble formation in a liquid on a hydrophilic surface the solid surface has only a minor influence on nucleation. In the alternative cases of condensation of a droplet on a hydrophilic surface and of bubble formation in a liquid on a hydrophobic surface, nucleation is significantly enhanced by the solid. Effectively, the existence of the solid surface results in a significant shift of the spinodal to lower supersaturations as compared with homogeneous nucleation. Qualitatively the same behavior is observed now near the new (solid surface induced) limits of instability of the fluid as compared with the behavior near to the spinodal curve in the case of homogeneous nucleation.
The effect of glass transition in fullerite C60 on Ar impurity diffusion
Authors: Dolbin A. V. , Esel'son V. B. , Gavrilko V. G. , Manzhelii V. G. , Vinnikov N. A. , Basnukaeva R. M.
Published: April 2013

The kinetics of sorption and subsequent desorption of argon gas by powdered fullerite C60 has been investigated in the temperature interval 58–290 K. The temperature dependence of the Ar diffusion coefficients in fullerite has been obtained using measured characteristic times of sorption. The diffusion coefficients for Ar decrease monotonically with decreasing temperature in the entire temperature range, which corresponds to the thermally activated diffusion of Ar atoms in fullerite. The glass transition in fullerite induces an order-of magnitude decrease in the activation energy of Ar diffusion in fullerite. This appears to be due to new paths that appeared as a result of the glass transition, in which the barriers separating the interstitial voids in the C60 lattice are significantly lower.
Molecular dynamics study on the failure modes of aluminium under decaying shock loading
Authors: Shao Jian-Li , Wang Pei , He An-Min , Duan Su-Qing , Qin Cheng-Sen
Published: April 2013

We have investigated the failure modes of single crystal aluminium under decaying shock loading by using molecular dynamics simulations. The microstructure evolution during the failure is presented in terms of the central symmetry parameter, and the corresponding pressure and temperature profiles are calculated and discussed. These results explain the failure morphology and mechanical properties under dynamic tension and especially the difference between solid and melted states. In addition, the fracture strength of aluminium is analyzed from surface velocity within acoustic approximation and virial theorem.
Large-area broad band saturable Bragg reflectors using oxidized AlAs in the circular and inverted mesa geometries
Authors: Nabanja Sheila P. , Kolodziejski Leslie A. , Petrich Gale S. , Sander Michelle Y. , Morse Jonathan L. , Shtyrkova Katia , Ippen Erich P. , Kärtner Franz X.
Published: April 2013

A semiconductor Saturable Bragg Reflector (SBR) is a mirror structure comprising alternating layers of high and low refractive index materials with an incorporated saturable absorber. SBRs can be used to initiate and sustain ultra-short pulses in various laser systems. In order to form ultra-short pulses, SBRs with high reflectivity over a broad wavelength range are required. Furthermore, large-area SBRs facilitate easy integration in a laser cavity. One of the key elements for the realization of broad band SBRs is the development of the thermal oxidation process that creates buried low-index AlxOy layers over large areas. The design, fabrication, characterization, and implementation of broad band, high index contrast III-V/AlxOy SBRs in the form of circular mesas, as well as inverted mesa structures, is presented.
Evanescent wave decomposition in a novel resonator comprising unmagnetized and magnetized plasma layers
Authors: Kong Xiang-kun , Liu Shao-bin , Zhang Hai-feng , Bian Bo-rui , Li Hai-ming , Zhao Xin
Published: April 2013

A 4 × 4 transfer matrix method has been applied to study the decomposition of any elliptically polarized wave in a magnetized resonator. When the incident elliptically polarized wave passes through the structure, it is orthogonally decomposed into two circular polarizations at two resonance frequencies. Without changing the structure of the resonator, the positions of the resonant frequencies of the right- and left-handed circularly polarized waves can be modulated by changing the external magnetized field. The results show that the proposed magnetized structure can be used to design a novel resonator, which can be applied in the decomposition of polarized electromagnetic waves.
High efficiency two-dimensional grating reflectors with angularly tunable polarization efficiency
Authors: Kroker Stefanie , Käsebier Thomas , Steiner Stefan , Kley Ernst-Bernhard , Tünnermann Andreas
Published: April 2013

We report on two-dimensional high-contrast subwavelength gratings with a polarization efficiency that is tunable in the angular spectrum. Due to the high index contrast it is possible to realize highly efficient reflectors with nearly angular independent reflection for light with transverse-electric polarization. Simultaneously, for transverse-magnetic polarized light the minimum and maximum reflectance can be tuned to a defined angle of incidence. Configurations with minimized and maximized polarization efficiencies at incidence angles of 0° and 45° are exemplified for a design wavelength of 1550 nm. For the case of minimum polarization efficiency we present the experimental results for a non-monolithic and a monolithic realization.
Planar and nonplanar ion acoustic shock waves in relativistic degenerate astrophysical electron-positron-ion plasmas
Authors: Ata-ur-Rahman  , Ali S. , Mirza Arshad M. , Qamar A.
Published: April 2013

We have studied the propagation of ion acoustic shock waves involving planar and non-planar geometries in an unmagnetized plasma, whose constituents are non-degenerate ultra-cold ions, relativistically degenerate electrons, and positrons. By using the reductive perturbation technique, Korteweg–deVries Burger and modified Korteweg–deVries Burger equations are derived. It is shown that only compressive shock waves can propagate in such a plasma system. The effects of geometry, the ion kinematic viscosity, and the positron concentration are examined on the ion acoustic shock potential and electric field profiles. It is found that the properties of ion acoustic shock waves in a non-planar geometry significantly differ from those in planar geometry. The present study has relevance to the dense plasmas, produced in laboratory (e.g., super-intense laser-dense matter experiments) and in dense astrophysical objects.
Resiliency in offshore wind farm communication networks
Authors: Gajrani Kiran , Gopal Sharma Krishan , Bhargava Annapurna
Published: April 2013

Wind energy is getting a considerable attention worldwide from the fraternity of the power system engineers as clean and green energy that can help reduce the carbon content and limit dependence on conventional fossil fuels. This has lead to the development of offshore wind farms in last few years. Real time monitoring and control of offshore wind farm require high speed, reliable, fault resilient, and cost effective communication infrastructure. The availability and reliability of wind energy mainly depend on resilient communication network. This can be achieved through a combination of redundancy and Quality of Service (QoS). In this paper, we have proposed fault resilient architecture of the medium scale offshore wind farm and simulated different fault scenarios based on IEC 61400-25 standard in OPNET. The wind farm communication is based on Transmission Control Protocol and Internet Protocol. The performance has been analysed with respect to QoS in terms of latency, traffic drop, and traffic congestion.
Two-dimensional weak anti-localization in Bi2Te3 thin film grown on Si(111)-(7 × 7) surface by molecular beam epitaxy
Authors: Roy Anupam , Guchhait Samaresh , Sonde Sushant , Dey Rik , Pramanik Tanmoy , Rai Amritesh , Movva Hema C. P. , Colombo Luigi , Banerjee Sanjay K.
Published: April 2013

We report on low temperature transport studies of Bi2Te3 topological insulator thin films grown on Si(111)-(7 × 7) surface by molecular beam epitaxy. A sharp increase in the magnetoresistance with magnetic field at low temperature indicates the existence of weak anti-localization. The measured weak anti-localization effect agrees well with the Hikami-Larkin-Nagaoka model, and the extracted phase coherence length shows a power-law dependence with temperature indicating the existence of a two-dimensional system. An insulating ground state has also been observed at low temperature showing a logarithmic divergence of the resistance that appears to be the influence of electron-electron interaction in a two-dimensional system.
Strain-driven synthesis of self-catalyzed branched GaAs nanowires
Authors: Zha Guowei , Li Mifeng , Yu Ying , Wang Lijuan , Xu Jianxing , Shang Xiangjun , Ni Haiqiao , Niu Zhichuan
Published: April 2013

We report the strain-driven synthesis of self-catalyzed branched GaAs nanowires (NWs). Decoration of facets with branches is achieved as NWs elongate or with the insertion of InAs. The hemisphere tip shaped branches on the backbone implies identical Vapor-Liquid-Solid growth mechanism. We present the homogeneous gallium-droplets (GDs) nucleation on the GaAs {110} side facets in the form of GaAs quantum-rings, specifying the role of GDs in branching. Structural characterization revealed strain defects at the crotch between the backbones and branches of the NWs. The evolution mechanism of self-catalyzed branched NWs is discussed and finally nano-trees with hyper-branches are demonstrated.
High longitudinal relaxivity of ultra-small gadolinium oxide prepared by microsecond laser ablation in diethylene glycol
Authors: Luo Ningqi , Tian Xiumei , Xiao Jun , Hu Wenyong , Yang Chuan , Li Li , Chen Dihu
Published: April 2013

Ultra-small gadolinium oxide (Gd2O3) can be used as T1-weighted Magnetic Resonance Imaging (MRI) contrast agent own to its high longitudinal relaxivity (r1) and has attracted intensive attention in these years. In this paper, ultra-small Gd2O3 nanoparticles of 3.8 nm in diameter have been successfully synthesized by a microsecond laser ablating a gadolinium (Gd) target in diethylene glycol (DEG). The growth inhibition effect induced by the large viscosity of DEG makes it possible to synthesize ultra-small Gd2O3 by laser ablation in DEG. The r1 value and T1-weighted MR images are measured by a 3.0 T MRI spectroscope. The results show these nanoparticles with a high r1 value of 9.76 s−1 mM−1 to be good MRI contrast agents. We propose an explanation for the high r1 value of ultra-small Gd2O3 by considering the decreasing factor (surface to volume ratio of the nanoparticles, S/V) and the increasing factor (water hydration number of the Gd3+ on Gd2O3 surface, q), which offer a new look into the relaxivity studies of MRI contrast agents. Our research provides a new approach to preparing ultra-small Gd2O3 of high r1 value by laser ablation in DEG and develops the understanding of high relaxivity of ultra-small Gd2O3 MRI contrast agents.
Effect of metal oxide morphology on electron injection from CdSe quantum dots to ZnO
Authors: Zheng Kaibo , Žídek Karel , Abdellah Mohamed , Chábera Pavel , Abd El-sadek Mahmoud S. , Pullerits Tõnu
Published: April 2013

Performance of quantum dot sensitized solar cells relies on a rapid electron injection from quantum dot to metal oxide. We studied the injection process in CdSe-ZnO system by ultrafast time-resolved absorption spectroscopy for two types of acceptor morphologies—nanowires and nanoparticles' films. Based on comparison between experimental data and Marcus theory, we demonstrate that the acceptor morphology has a significant impact on electron injection due to (i) change in material permittivity and (ii) different density of the band-edge states. The results open a reference to improve injection efficiency in quantum dot-metal oxide system by selection of the acceptor morphology.
The effect of infrared radiation on quantum magnetotransport in n-InGaAs/GaAs with two strongly coupled quantum wells
Authors: Gudina S. V. , Arapov Yu. G. , Neverov V. N. , Podgornykh S. M. , Yakunin M. V.
Published: April 2013

Longitudinal ρxx(B) and Hall ρxy(B) magnetoresistances are measured as a function of transverse magnetic field in n-InGaAs/GaAs nanostructures with strongly coupled double quantum wells in the temperature range T = 0.05–60 K and magnetic fields B = 0–16 T before and after low-temperature infrared irradiation. The appearance of persistent photoconductivity causes the type of the temperature dependence of resistance to be changed: from insulator-like (dρ/dT < 0) for T ≤ 8 K to metallic-like (dρ/dT > 0) at higher temperatures. It is shown that this is related to the temperature dependence of electron density. The strong temperature dependence of electron mobility observed before the illumination practically disappears after infrared irradiation.
Ultraviolet-driven white light generation from oxyfluoride glass co-doped with Tm3+-Tb3+-Eu3+
Authors: Kuznetsov A. S. , Nikitin A. , Tikhomirov V. K. , Shestakov M. V. , Moshchalkov V. V.
Published: April 2013

Tm3+-Tb3+-Eu3+ co-doped oxyfluoride glasses, doped with about 3.0 mol. % TmF3, 0.25 mol. % TbF3, and 0.25 mol. % EuF3, have been prepared by melt quenching technique. Under excitation at commercial 365 nm, the rare-earth co-dopants are all directly excited and emit in the blue, green, and red, respectively, without appreciable energy transfer amongst the co-dopants. Tint of the white luminescence can be adjusted by changing the ratio of the co-dopants. Properties of the glass host promote excellent dissolution of the co-dopants and low non-radiative decay rate. The white emission at 365 nm excitation is suitable for light emitting diodes applications.
A chip scale lin⊥lin quasi-bichromatic laser scheme
Authors: Tan Bozhong , Yun Peter , Yang Jing , Tian Yuan , Gu Sihong
Published: April 2013

We present a chip scale lin⊥lin quasi-bichromatic laser beam generator scheme and our experimental study results. Through modulating two vertical-cavity surface-emitting lasers (VCSELs) with the same microwave, both VCSELs output multichromatic lasers and every frequency component in their outputs contributes for the frequency mutual injection locking between VCSELs. The system outputs a lin⊥lin quasi-bichromatic laser beam in which the two wanted frequency components share more than 90% of the total laser power. It is promising to apply the chip device in the chip scale coherent population trapping (CPT) atomic clock and the chip scale CPT magnetometer.
Enhanced performance of GaN-based light-emitting diodes with graphene/Ag nanowires hybrid films
Authors: Li Zhi , Kang Junjie , Liu Zhiqiang , Du Chengxiao , Lee Xiao , Li Xiao , Wang Liancheng , Yi Xiaoyan , Zhu Hongwei , Wang Guohong
Published: April 2013

Incorporating Ag nanowires with graphene resulted in improved electrical conductivity and enhanced contact properties between graphene and p-GaN. The graphene/AgNWs hybrid films exhibited high transmittance and lower sheet resistance compared to bare graphene. The specific contact resistance between graphene and p-GaN reduced nearly an order of magnitude with the introduction of AgNWs. As a result, light emitting diodes based on the hybrid films showed 44% lower forward voltage and 2-fold higher light output power. The enhanced performance was attributed to the bridging by AgNWs of cracks, grain boundaries in graphene and the reduction of Schottky barrier height at graphene/ p-GaN interface.