bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of clomipramine as chemotherapy of the chronic phase of Chagas disease
Authors: FAURO ROMINA , PRESTI SILVINA LO , BAZAN CAROLINA , BAEZ ALEJANDRA , STRAUSS MARIANA , TRIQUELL FERNANDA , CREMONEZZI DAVID , NEGRETE OLGA SANCHEZ , WILLHUBER GASTON CAMINO , PAGLINI-OLIVA PATRICIA , RIVAROLA HECTOR WALTER
Published: March 2013

Chagas infection is a major endemic disease affecting Latin American countries. The persistence ofTrypanosoma cruzigenerates a chronic inflammatory reactivity that induces an immune response directed to the host's tissues. The effectiveness of the treatment in the chronic phase is still unsatisfactory due, amongst other reasons, to the collateral effects of the drugs used. We investigated the effect of clomipramine, a tricyclic antidepressant that, when used as a treatment ofT. cruzi-chronically infected mice, inhibits trypanothione reductase, an exclusive and vital enzyme ofT. cruzi. Clomipramine improved survival (P<0·05) by diminishing the parasite intensity as demonstrated by PCR studies in the heart and skeletal muscle, and significantly prevented the evolution to fibrosis of the inflammatory infiltrates. Clomipramine could be a good candidate for the treatment of chronic Chagas disease.
Identity in crisis: The role of work in the formation and renegotiation of a musical identity
Authors: Oakland Jane , MacDonald Raymond , Flowers Paul
Published: March 2013

This study presents a qualitative investigation into the effects of enforced occupational change on a professional musical identity. Interpretative Phenomenological Analysis (IPA) is used to explore the meaning of redundancy for six professional opera choristers. The paper highlights aspects of career disruption that are unique to singers who make their living using a biologically embedded instrument. Findings show the ‘opera singer’ identity to be a professional identity which consists of several subjective sub-identities. Adaptation to change is dependent on the salience given to these subjective identities. It is suggested that if more attention is given to these subjective sub-identities during a professional career, musicians may be better prepared for unexpected disruption to an established career pattern.
Intonation influences how children and adults interpret sarcasm
Authors: GLENWRIGHT MELANIE , PARACKEL JAYANTHI M. , CHEUNG KRISTENE R. J. , NILSEN ELIZABETH S.
Published: March 2013

Adults distinguish sarcasm from literal language according to intonation involving a reduction in fundamental frequency (F0). We examined whether children's and adults' interpretation of a sarcastic speaker's belief, attitude, and humor was affected by degree of F0 reduction by presenting five- to six-year-olds and adults with sarcastic and literal criticisms with a small, medium, or large mean F0 reduction. Children and adults were more accurate in attributing the speaker's belief and intent for sarcastic criticisms for large F0 reductions compared to small reductions. These results show that F0 reduction is a helpful cue to sarcasm interpretation for both children and adults.
Biphasic assembly of the contractile apparatus during the first two cell division cycles in zebrafish embryos
Authors: Webb Sarah E. , Goulet Cécile , Chan Ching Man , Yuen Michael Y. F. , Miller Andrew L.
Published: March 2013

The large and optically clear embryos of the zebrafish provide an excellent model system in which to study the dynamic assembly of the essential contractile band components, actin and myosin, via double fluorescent labelling in combination with confocal microscopy. We report the rapid appearance (i.e. within <2 min) of a restricted arc of F-actin patches along the prospective furrow plane in a central, apical region of the blastodisc cortex. These patches then fused with each other end-to-end forming multiple actin cables, which were subsequently bundled together forming an F-actin band. During this initial assembly phase, the F-actin-based structure did not elongate laterally, but was still restricted to an arc extending ~15° either side of the blastodisc apex. This initial assembly phase was then followed by an extension phase, where additional F-actin patches were added to each end of the original arc, thus extending it out to the edges of the blastodisc. The dynamics of phosphorylated myosin light chain 2 (MLC2) recruitment to this F-actin scaffold also reflect the two-phase nature of the contractile apparatus assembly. MLC2 was not associated with the initial F-actin arc, but MLC2 clusters were recruited and assembled into the extending ends of the band. We propose that the MLC2-free central region of the contractile apparatus acts to position and then extend the cleavage furrow in the correct plane, while the actomyosin ends alone generate the force required for furrow ingression. This biphasic assembly strategy may be required to successfully divide the early cells of large embryos.
Unusual DNA Structures Formed on Bare Highly Oriented Pyrolytic Graphite Surfaces Studied by Atomic Force Microscopy
Authors: Liu Zhiguo , Zhao Lin , Zu Yuangang , Tan Shengnan , Wang Yuanlin , Zhang Yiming
Published: March 2013

It is important to know the detailed DNA structure on carbonaceous surfaces for further application of DNA-functionalized carbonaceous materials in diverse research areas. In this study, the topographic and structural characteristics of the separated single DNA molecules and their assembly on highly oriented pyrolytic graphite (HOPG) surfaces have been investigated by atomic force microscopy (AFM). AFM results indicate that both circular and linear DNA molecules tend to form hexagonal patterns along with some unusual structures that include node, protrusion, cruciform, parallel single-stranded DNA (ssDNA), and compact zigzag. Furthermore, parallel ssDNA patterns and their crossed structures have been obtained under high-temperature conditions. Our AFM results reveal that a bare HOPG surface can induce DNA molecules to form various unusual structures. This finding is helpful for understanding the adsorption behavior of DNA on other carbonaceous surfaces such as carbon nanotubes and graphene. In addition, the hexagonal DNA patterns in this study are similar to those formed on the alkylamine-modified HOPG surface, which implies that a bare HOPG, without any chemical modification, has a strong ability to align biomolecules. This study could expand our knowledge of the diversities of DNA structures and the aligning ability of carbonaceous surfaces.
Voicing the Labyrinth: the Collaborations of Edoardo Sanguineti and Luciano Berio
Authors: OSMOND-SMITH DAVID
Published: March 2013

In this article David Osmond-Smith discusses the ‘creative cross-fertilization’ between Luciano Berio and the poet Edoardo Sanguineti. Berio first approached Sanguineti at the suggestion of Umberto Eco, and the article begins with a discussion of Berio and Eco's radiophonic project Onomatopea nel linguaggio poetico, which in turn stimulated one of the composer's most celebrated electroacoustic works, Thema/Omaggio a Joyce (1958). The author argues that the preoccupation revealed there with ‘working at the boundary where the word as bearer of meaning dissolves into the word as reservoir of sonic potentials’ remained central to the collaborations of Berio and Sanguineti, principally Passaggio (1961–2), Laborintus II (1965), and A-Ronne (1974–5). In particular, the former two works explore their ‘aesthetics of fragmentation and juxtaposition’ in the context of a music theatre that embraces Umberto Eco's poetics of the opera aperta (open work), Guy Debord's notion of ‘spectacularity’, and various dimensions of political and social critique. (CW)
A Semblance of Freedom: Karl Amadeus Hartmann between Democratic Renewal and Cold War, 1945–7
Authors: BLOMANN ULRICH J. , THYM JÜRGEN
Published: March 2013

For more than a decade, literature on the cultural politics of the Cold War in postwar Europe has done much to question the notion that the political manipulation of music was confined to the Soviet bloc, and that musicians in the West enjoyed untrammelled autonomy and freedom. This article focuses on the case of the German composer Karl Amadeus Hartmann, presenting evidence that the reorientation he underwent in the late 1940s (during which he revised, retitled, or suppressed nearly all the works he had composed between 1930 and 1945) was motivated not by purely aesthetic or personal considerations, as some writers have suggested, but by strong pressures to eradicate from his output all manifestations of social(ist) and political commitment. In Bavaria, where Hartmann lived, anti-communism was rife in political circles. Meanwhile, in the cultural sphere, critics such as Hans Heinz Stuckenschmidt (strongly influenced by Nicolas Nabokov) abandoned their pre-war commitment to socially relevant art, denounced Shostakovich (a composer much admired by Hartmann), and began promoting Schoenberg as a rational, apolitical exemplar of formalism in music. Against this background – and in the light of his experiences with one work in particular, theSymphonische Ouvertüre ‘China kämpft’– Hartmann felt compelled to reassess his political position.
Palm frond biochar production and characterisation
Authors: Som A. Md , Wang Z. , Al-Tabbaa A.
Published: March 2013

Palm oil has been the world's main source of oil and fats since 2004, producing over 45 million tonnes in 2009. Malaysia alone has over 4·5 million hectares planted with oil palm and, based on common practice, ∼300 palm fronds are pruned per hectare per year. This agricultural waste is currently either being used as roughage feed or, more frequently, being left between rows of palm trees to prevent soil erosion, or for nutrient recycling purposes. This paper proposes an alternative use for palm frond as a source of biochar. A traditional method commonly use by gardeners in Malaysia to improve soil fertility was used to produce the biochar. A shallow earth pit was dug in the ground for the carbonisation process. The process is described and the impact of carbonisation on the earth wall is analysed and presented. The process was later re-assessed by using TGA-FTIR. Most of the hemicelluloses had fully disintegrated, but the depolymerisation of the cellulose was still incomplete at the carbonisation temperature. Most of the lignin aromatic structure was still present in the biochar. The carbonisation process was repeated in the laboratory and biochar was characterised by using BET, SEM and FTIR. An adsorption isotherm study was conducted and the experimental data were fitted to the Langmuir model. The model predicted Pb2+ adsorption rates of 83·3 mg/g, Cu2+ 41·4 mg/g, Ni2+ 13·0 mg/g and Zn2+ 19·7 mg/g.
Governance by Disclosure: Transnational Convergence in the Field of Nanotechnology
Authors: Snir Reut
Published: March 2013

‘Nanotechnology’, the manipulation of matter on an atomic and molecular scale, is projected to profoundly alter manufacturing systems globally. However, along with the promise that these new technologies hold, there are concerns about the possibility of unknown latent risks to human health or the environment. Under current scientific uncertainties, regulators explore new strategies for overseeing the development and safe use of nanotechnologies. Information disclosure plays a prominent role among these strategies. Thus far, however, the informational strategies actually employed by governments have focused on means by which to collect information from industry, and the types of information requested do not allow for an adequate health risk assessment. Moreover, little effort has been made to make the information collected publicly available. The article addresses the question of what information is disclosed (or not disclosed) and why, highlighting the socio-political context within which these decisions are made, and their democratic implications. It argues that the current ‘light-touch’ disclosure-based approach may lie in technical, evidence-based, ‘risk’ conception, which is common to both the United States and the European Union. It further argues for a more democratic ‘governance-by-disclosure’ approach, which allows society to prioritize risks that it is willing to take to enjoy the benefit of technological progress.
TIMP-1 Attenuates Blood–Brain Barrier Permeability in Mice with Acute Liver Failure
Authors: Chen Feng , Radisky Evette S , Das Pritam , Batra Jyotica , Hata Toshiyuki , Hori Tomohide , Baine Ann-Marie T , Gardner Lindsay , Yue Mei Y , Bu Guojun , del Zoppo Gregory , Patel Tushar C , Nguyen Justin H
Published: March 2013

Blood-brain barrier (BBB) dysfunction in acute liver failure (ALF) results in increased BBB permeability that often precludes the patients from obtaining a life-saving liver transplantation. It remains controversial whether matrix metalloproteinase-9 (MMP-9) from the injured liver contributes to the deregulation of BBB function in ALF. We selectively upregulated a physiologic inhibitor of MMP-9 (TIMP-1) with a single intracerebroventricular injection of TIMP-1 cDNA plasmids at 48 and 72 hours, or with pegylated-TIMP-1 protein. Acute liver failure was induced with tumor necrosis factor-α and D-(+)-galactosamine in mice. Permeability of BBB was assessed with sodium fluorescein (NaF) extravasation. We found a significant increase in TIMP-1 within the central nervous system (CNS) after the administration of TIMP-1 cDNA plasmids and that increased TIMP-1 within the CNS resulted in an attenuation of BBB permeability, a reduction in activation of epidermal growth factor receptor and p38 mitogen-activated protein kinase signals, and a restoration of the tight junction protein occludin in mice with experimental ALF. Pegylated TIMP-1 provided similar protection against BBB permeability in mice with ALF. Our results provided a proof of principle that MMP-9 contributes to the BBB dysfunction in ALF and suggests a potential therapeutic role of TIMP-1 in ALF.
Assessing White Matter Ischemic Damage in Dementia Patients by Measurement of Myelin Proteins
Authors: Barker Rachel , Wellington Dannielle , Esiri Margaret M , Love Seth
Published: March 2013

White matter ischemia is difficult to quantify histologically. Myelin-associated glycoprotein (MAG) is highly susceptible to ischemia, being expressed only adaxonally, far from the oligodendrocyte cell body. Myelin-basic protein (MBP) and proteolipid protein (PLP) are expressed throughout the myelin sheath. We compared MAG, MBP, and PLP levels in parietal white matter homogenates from 17 vascular dementia (VaD), 49 Alzheimer's disease (AD), and 33 control brains, after assessing the post-mortem stability of these proteins. Small vessel disease (SVD) and cerebral amyloid angiopathy (CAA) severity had been assessed in paraffin sections. The concentration of MAG remained stable post-mortem, declined with increasing SVD, and was significantly lower in VaD than controls. The concentration of MBP fell progressively post-mortem, limiting its diagnostic utility in this context. Proteolipid protein was stable post-mortem and increased significantly with SVD severity. The MAG/PLP ratio declined significantly with SVD and CAA severity. The MAG and PLP levels and MAG/PLP did not differ significantly between AD and control brains. We validated the utility of MAG and MAG/PLP measurements on analysis of 74 frontal white matter samples from an Oxford cohort in which SVD had previously been scored. MAG concentration and the MAG/PLP ratio are useful post-mortem measures of ante-mortem white matter ischemia.
Diameter-modulated ferromagnetic CoFe nanowires
Authors: Esmaeily A. S. , Venkatesan M. , Razavian Asra S. , Coey J. M. D.
Published: March 2013

Highly ordered nanoporous anodic aluminium oxide templates with uniform or periodically modulated pore diameters have been fabricated by the hard-pulse anodization technique. Straight and diameter-modulated CoFe nanowires with diameters of 60 nm and 60/120 nm, respectively, were AC-pulse electrodeposited into the templates. A comparison of magnetisation curves of the two types of nanowires show a typical coercivity (μ0Hc) of 74 mT and squareness (SQ) of 92% for the modulated wires, which are significantly squarer but have 12% lower coercivity compared to the 60 nm straight CoFe wires (μ0Hc = 84 mT, SQ = 60%). The difference is attributed to magnetostatic interactions between the segments due to the stray field of the modulated wires. Diameter modulation is an attractive way of producing soft magnetic nanowires with a controllable hysteresis loop shape. The time required for the nanoporous template fabrication by hard-pulse anodization is typically one tenth of that needed for conventional template fabrication methods, hence making it suitable for large-scale nanowire production.
Cathodic corrosion. I. Mechanism of corrosion via formation of metal anions in aqueous medium
Authors: Yanson Yu. I. , Yanson A. I.
Published: March 2013

In this paper we describe an unusual electrochemical phenomenon, namely, cathodic corrosion of platinum. We show that all existing models of cathodic corrosion are inconsistent with our experimental observations. Therefore, we present a new model of cathodic corrosion, which is based on the assumption that metal anions are formed at the electrode surface during the corrosion process. These anionic species function as precursors for the formation of the final product of cathodic corrosion, i.e., metal nanoparticles.
New directions in point-contact spectroscopy based on scanning tunneling microscopy techniques (Review Article)
Authors: Tartaglini E. , Verhagen T. G. A. , Galli F. , Trouwborst M. L. , Müller R. , Shiota T. , Aarts J. , van Ruitenbeek J. M.
Published: March 2013

Igor Yanson showed 38 yr ago for the first time a point-contact measurement where he probed the energy resolved spectroscopy of the electronic scattering inside the metal. Since this first measurement, the point contact spectroscopy (PCS) technique improved enormously. The application of the scanning probe microscopy (SPM) techniques in the late 1980 s allowed achieving contacts with a diameter of a single atom. With the introduction of the mechanically controlled break junction technique, even spectroscopy on freely suspended chains of atoms could be performed. In this paper, we briefly review the current developments of PCS and show recent experiments in advanced scanning PCS based on SPM techniques. We describe some results obtained with both needle-anvil type of point contacts and scanning tunneling microscopy (STM). We also show our first attempt to lift up with a STM a chain of single gold atoms from a Au(110) surface.
Andreev experiments on superconductor/ferromagnet point contacts
Authors: Bouvron S. , Stokmaier M. , Marz M. , Goll G.
Published: March 2013

Andreev reflection is a smart tool for investigating the spin polarization P of the current through point contacts between a superconductor and a ferromagnet. We compare different models for extracting P from experimental data and investigate the dependence of P on various parameters of a contact.
Effect of cold working of the metal on the conductance of platinum, copper, and silver nanocontacts
Authors: Shklyarevskii O. I. , Yanson I. K.
Published: March 2013

Cold metal working, which leads to strengthening and changes in various physical properties of metals on a macroscopic level, can have a significant effect on the conductance of nanowires drawn from these materials when they break. This effect is studied for Ag, Cu, Pt, and a number of other metals. Molecular hydrogen is found to affect the characteristics of breaking in silver nanowires.
Charge density waves in d-wave superconductors: Thermodynamics and Josephson tunneling (Review Article)
Authors: Gabovich A. M. , Voitenko A. I.
Published: March 2013

The problem of coexistence between charge-density-waves (CDWs) and superconductivity is revisited. Recent evidence was analyzed for different classes of materials with the emphasis on high-Tc oxides. For the latter, the model of the d-wave or extended s-wave Cooper pairing competing with checkerboard or unidirectional CDWs is suggested. The corresponding phase diagrams were plotted and used as a guide to predict new features in the tunnel or photoemission spectra. In the framework of the model concerned, dc Josephson tunneling through junctions involving CDW superconductors is examined. It is shown that CDWs distort current dependences on the angle between crystal axes and the junction plane inherent to d-wave superconductors leading to an extra periodicity.
Macroscopic quantum tunneling and retrapping processes in moderately damped YBaCuO Josephson junctions
Authors: Massarotti D. , Longobardi L. , Galletti L. , Stornaiuolo D. , Rotoli G. , Tafuri F.
Published: March 2013

The moderately damped regime in Josephson junctions (JJ) is quite common in devices characterized by low critical currents and, therefore, by low Josephson energies. Measurements of the switching current distribution (SCD) are a direct way of determining the phase dynamics in the nontrivial case of moderate damping, which is becoming more common with advances in nanopatterning superconductors and in materials science for fabricating hybrid systems. We report measurements of SCDs, in both the thermal and quantum regimes for moderately damped YBaCuO grain boundary biepitaxial JJs. A direct transition from a phase diffusion regime to macroscopic quantum tunnelling occurs at about 130 mK. The crossover to the quantum regime is determined by the magnetic field and the phase dynamics can be described by a fully consistent set of junction parameters obtained by numerical simulation.
High temperature reaction kinetics of CN(v = 0) with C2H4 and C2H6 and vibrational relaxation of CN(v = 1) with Ar and He
Authors: Saidani Ghassen , Kalugina Yulia , Gardez Aline , Biennier Ludovic , Georges Robert , Lique François
Published: March 2013

The investigation of the chemical complexity of hot environments, ranging from combustion flames to circumstellar envelopes of evolved stars, relies on the determination of the reaction kinetics and product branching ratio. We have designed a chemical reactor for the exploration of high temperature chemistry. This apparatus is employed in the present study to measure the reaction kinetics of the CN radical with C2H4 and C2H6 over the 300–1200 K temperature range. In our setup and in some environments, the CN radical is partially produced in a vibrationally excited state, before relaxing by collision with the surrounding gas. We complement the experimental kinetic studies of hydrocarbons reactions with CN(v = 0) with a theoretical study of vibrational relaxation of CN(v = 1) by He and Ar atoms, the main collisional partners in our apparatus. Calculations are carried out to determine the collisional elastic and inelastic cross sections versus the kinetic energy as well as the corresponding vibrationally elastic and inelastic rate coefficients. The results are compared with empirical calculations and with a few experimental observations. The range of validity of the empirical model is discussed and potential applications sketched.
Nonadiabatic anharmonic electron transfer
Authors: Schmidt P. P.
Published: March 2013

The effect of an inner sphere, local mode vibration on an electron transfer is modeled using the nonadiabatic transition probability (rate) expression together with both the anharmonic Morse and the harmonic oscillator potential. For an anharmonic inner sphere mode, a variational analysis uses harmonic oscillator basis functions to overcome the difficulties evaluating Morse-model Franck-Condon overlap factors. Individual matrix elements are computed with the use of new, fast, robust, and flexible recurrence relations. The analysis therefore readily addresses changes in frequency and/or displacement of oscillator minimums in the different electron transfer states. Direct summation of the individual Boltzmann weighted Franck-Condon contributions avoids the limitations inherent in the use of the familiar high-temperature, Gaussian form of the rate constant. The effect of harmonic versus anharmonic inner sphere modes on the electron transfer is readily seen, especially in the exoergic, inverted region. The behavior of the transition probability can also be displayed as a surface for all temperatures and values of the driving force/exoergicity Δ = −ΔG. The temperature insensitivity of the transfer rate is clearly seen when the exoergicity equals the collective reorganization energy (Δ = Λs) along a maximum ln (w) vs. Δ ridge of the surface. The surface also reveals additional regions for Δ where ln (w) appears to be insensitive to temperature, or effectively activationless, for some kinds of inner sphere contributions.
Graphene as transparent electrode for direct observation of hole photoemission from silicon to oxide
Authors: Yan Rusen , Zhang Qin , Kirillov Oleg A. , Li Wei , Basham James , Boosalis Alex , Liang Xuelei , Jena Debdeep , Richter Curt A. , Seabaugh Alan C. , Gundlach David J. , Xing Huili G. , Nguyen N. V.
Published: March 2013

We demonstrate the application of graphene as collector material in internal photoemission (IPE) spectroscopy, which enables direct observation of both electron and hole injections at a Si/Al2O3 interface and overcomes the long-standing difficulty of detecting holes in IPE measurements. The observed electron and hole barrier heights are 3.5 ± 0.1 eV and 4.1 ± 0.1 eV, respectively. Thus, the bandgap of Al2O3 can be deduced to be 6.5 ± 0.2 eV, in good agreement with the value obtained by ellipsometry analysis. Our modeling effort reveals that, by using graphene, the carrier injection from the emitter is significantly enhanced and the contribution from the collector electrode is minimal.
Direct measurements of field-induced strain in magnetoelectric composites by X-ray diffraction studies of forbidden reflections
Authors: Abes M. , Koops C. T. , Hrkac S. B. , Quandt E. , Bouchenoire L. , Murphy B. M. , Magnussen O. M.
Published: March 2013

Static and magnetic field induced strains at a magnetoelectric (ME) buried interface, consisting of a ZnO(001) piezoelectric substrate and an amorphous Fe58Tb42 magnetostrictive layer, were determined by measuring the intensity of the forbidden ZnO(3–31) Bragg reflection. The comparison with an uncoated ZnO substrate shows that a permanent strain is induced by the growth process. For FeTb coated ZnO, an additional static strain of (1.6 ± 0.2) × 10−4 relative to the pure ZnO substrate is found near the interface, which is close to that determined from the peak position shift of the allowed ZnO(4–40) Bragg reflection. Upon applying a magnetic field along the [1–10] direction, the intensity of the ZnO(3–31) forbidden Bragg reflection increases with increasing field magnitude as predicted. The induced strain, transferred to the piezoelectric ZnO substrate due to the external magnetic field acting on the magnetostriction FeTb layer, approaches a saturation value of εH = (3.7 ± 0.2) × 10−4 at B ≥ 0.05 T, in good agreement with the results from cantilever bending measurements. These results indicate an excellent coupling at this ME interface.
Magnon softening in exchange-coupled hard-soft nanocomposites
Authors: Belemuk A. M. , Chui S. T.
Published: March 2013

We study spin excitations of the fully aligned state for three-dimensional nanocomposites of exchange coupled hard (SmFeN) and soft (FeCo) phases. The dipolar interaction lowers the magnon energy and controls the spin wave gap at k = 0, which closes when the amount of soft phase exceeds a critical value. With the addition of soft phase or increasing temperature the system moves to another ground state characterized by a tilting of the magnetization at the boundaries between spins of the hard and the soft phases.
Indirect exchange of magnetic impurities in zigzag graphene ribbon
Authors: Sun J. H. , Hu F. M. , Tang H. K. , Guo W. , Lin H. Q.
Published: March 2013

We use quantum Monte Carlo method to study the indirect coupling between two magnetic impurities on the zigzag edge of graphene ribbon. If the two adatoms are located on the sites belonging to opposite sublattices, their antiferromagnetic spin-spin correlation is drastically suppressed at the zero-energy, and is first enhanced and then decreased as we lower the chemical potential. If the two adatoms are adsorbed on the same sublattice, we find similar behavior of spin-spin correlation except for a crossover from ferromagnetic to antiferromagnetic correlation as we lower the chemical potential. We also calculate the weight of different components of d-electron wave function and local magnet moment for various values of parameters, and all the results are consistent with those of spin-spin correlation between two magnetic impurities.
Negative pressures in nanoporous membranes for thin film evaporation
Authors: Xiao Rong , Maroo Shalabh C. , Wang Evelyn N.
Published: March 2013

We present a nanoporous membrane-based approach, which decouples the capillary pressure from the viscous resistance, to achieve high driving pressures and efficient liquid delivery for thin film evaporation. By using alumina membranes with ≈150 nm pore diameters, absolute liquid pressures as low as −300 kPa were achieved using isopropyl alcohol, while dissipating maximum interfacial heat fluxes of ≈96 W/cm2. Design guidelines are provided to achieve higher interfacial heat fluxes with reduced membrane thicknesses. This work shows a promising approach to address thermal management needs for next generation electronic devices.
Thermal transport in C20 fullerene-chained carbon nanobuds
Authors: Loh G. C. , Baillargeat D.
Published: March 2013

Carbon nanobuds, which are hybrid fullerene-nanotube structures, have previously shown glimpses of their potential in nanotechnology applications. By performing molecular dynamics simulations, a novel study of thermal conduction in a compact form of carbon nanobuds is presented. We demonstrate that nanobuds conduct thermal energy relatively well, within an order compared to nanotubes. Alike their close relatives—the carbon peapod, this essentially extends the dimensionality of thermal management applications. A rigorous calculation of the vibrational entropy and specific heat at the interfacial locations suggests that both functions are relatively identical in magnitude at fullerene-fullerene and fullerene-nanotube interfaces. Two common nanobud configurations are compared: while both are comparable in mechanical stability, a type 2 carbon nanobud (perfect fullerene, nanotube with vacancies) is less thermally conductive than a type 1 nanobud (perfect fullerene, perfect nanotube) due to more scattering of long-wavelength modes at the defect sites of the nanotube.
Investigation of the magnetic hyperfine field at R and Zn sites in RZn (R = Gd, Tb, Dy) compounds using perturbed gamma-gamma angular correlation spectroscopy with 140Ce and 111Cd as probe nuclei
Authors: Bosch-Santos B. , Carbonari A. W. , Cabrera-Pasca G. A. , Costa M. S. , Saxena R. N.
Published: March 2013

The magnetic hyperfine field (Bhf) in RZn compounds (R = Gd, Tb, Dy) has been investigated by perturbed angular correlation spectroscopy using 140Ce and 111Cd as probe nuclei, respectively, at R and Zn sites, in order to study the origin of the magnetic coupling in these compounds. The results for 111Cd probe showed that the temperature dependence of Bhf roughly follows the Brillouin function for the R total angular momentum J of each compound. The temperature dependence of Bhf measured with 140Ce probes showed, however, a sharp deviation from the Brillouin curve for all compounds, which was ascribed to the contribution of the 4f-electron of Ce3+ to Bhf.
A concept of power generator using wind turbine, hydrodynamic retarder, and organic Rankine cycle drive
Authors: Sami Samuel
Published: March 2013

This paper describes a concept of electric power generating system that uses a wind turbine to generate kinetic energy which converts heat through a hydrodynamic retarder. The heat so generated is utilized to drive an organic Rankine cycle that converts thermal energy into electricity power for continuous and undisrupted supply during the year. A hydrodynamic retarder converts kinetic energy into heat through hot fluid by directing the flow of the fluid into the hydrodynamic retarder in a manner that resists rotation of blades of the wind turbine. The hot fluid circulating in the hydrodynamic retarder is a thermal heat source for vapor regeneration of organic heat exchange fluid mixture(s) used in the Rankine cycle. The expansion of the organic heat exchange fluid gets converted into rotation of the generator rotor.
Large magnetocaloric effects over a wide temperature range in MnCo1−xZnxGe
Authors: Samanta Tapas , Dubenko Igor , Quetz Abdiel , Stadler Shane , Ali Naushad
Published: March 2013

The magnetic and structural transitions can be controlled to coincide by partial substitution of Zn for Co in MnCo1−xZnxGe, leading to a large magnetocaloric effects over a wide temperature range. The magnetostructural transition from paramagnetic to ferromagnetic state results in magnetic entropy changes (−ΔSM) of 26 J/kg K at 327 K for ΔH = 5 T in the case of x = 0.045. Interestingly, a structurally driven first-order phase transition between two high magnetization states as observed for x = 0.05 and 0.06 also lead to large values of −ΔSM = 31.4 and 20.6 J/kg K for ΔH = 5 T at 281 and 209 K, respectively. The observed large magnetocaloric effects with tunable phase transition temperatures make these materials promising for near room-temperature magnetic cooling applications.
Exchange bias in La0.7Sr0.3MnO3/SrMnO3/La0.7Sr0.3MnO3 trilayers
Authors: Jungbauer M. , Hühn S. , Michelmann M. , Goering E. , Moshnyaga V.
Published: March 2013

Exchange bias (EB) has been observed for all-manganite La0.7Sr0.3MnO3/SrMnO3/La0.7Sr0.3MnO3 trilayers with ferromagnetic La0.7Sr0.3MnO3 and G-type antiferromagnetic SrMnO3 (SMO) layers, grown on (001) SrTiO3 substrates by metalorganic aerosol deposition. The field shift of the magnetic hysteresis loop HE and the coercivity HC decay exponentially with temperature. HE exhibits a global maximum as a function of SMO interlayer thickness at tSMO≈4.5 nm. We argue that EB behaviour can be explained by the interplay of a spinglass state at the interface and theoretically proposed mechanism based on the Dzyaloshinskii-Moriya interaction.
Parameter determination for device simulations of thin film silicon solar cells by inverse modeling based on temperature and spectrally dependent measurements
Authors: Ostertag Julia P. , Klein Stefan , Schmidt Oliver , Brüggemann Rudolf
Published: March 2013

Opto-electronic device simulation of thin-film silicon solar cells requires a set of many input parameters for the electronic properties of amorphous and microcrystalline silicon. In this paper, a systematic determination of these is performed by inverse modeling and particle swarm optimization with experimental and simulated current-voltage characteristics of amorphous and microcrystalline silicon pin diodes, both in the dark and under illumination. The parameters are validated by additional experiments and simulations of the temperature-dependent dark current, of spectrally selective illumination, and of the external quantum efficiency of the amorphous and microcrystalline silicon diode, respectively. The validation of the input parameters is complemented by simulation of a tandem solar cell with the amorphous and the microcrystalline silicon input parameters. Simulation and experiment (spectrally dependent current-voltage characteristics and external quantum efficiency) of such a tandem solar cell show good agreement. Sensitivity studies on different sets of input parameters for the inverse modeling process are also presented.
N-doped graphene-supported Pt and Pt-Ru nanoparticles with high electrocatalytic activity for methanol oxidation
Authors: Dong Hongzhou , Bai Jincheng , Zhu Qianqian , Yu Jianhua , Yu Liyan , Dong Lifeng
Published: March 2013

In this work, Pt and Pt-Ru nanoparticles were synthesized on both graphene and nitrogen (N)-doped graphene sheets, and their effects on electrocatalytic activity for methanol oxidation were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. Experimental results show that, in comparison to pure graphene as catalyst support, N-doped graphene-supported Pt and Pt-Ru nanoparticles demonstrate enhanced characteristics for methanol electro-oxidations with regard to oxidation potential, forward peak oxidation current density, and charge transfer resistance. For instance, the forward peak current densities of graphene-supported Pt and Pt-Ru nanoparticles were 9.5 mA/cm2 and 7.3 mA/cm2, respectively; however, the current densities of N-doped graphene-supported Pt and Pt-Ru nanoparticles were 19.9 mA/cm2 and 16.2 mA/cm2, respectively. The doping of nitrogen into graphene can effectively improve the currently density by twice. Our findings suggest the use of N-doped graphene sheets as promising catalyst supports for direct methanol fuel cells.
Molybdenum modified AISI 304 stainless steel bipolar plate for proton exchange membrane fuel cell
Authors: Wang Lixia , Sun Juncai
Published: March 2013

A molybdenum diffusion layer has been prepared on the surface of AISI 304 stainless steel (Mo-304 SS) by means of plasma surface diffusion alloying method. X-ray diffraction data show that the molybdenum modified layer of 304 SS mainly consists of cubic Mo. The results of scanning electron microscopy in combination with energy-dispersive X-ray analysis spectrometer indicate that the as-prepared molybdenum diffusion layer is ∼3 μm with dominant molybdenum element. A series of electrochemical evaluation tests were conducted on the Mo-304 SS specimens to determine if the Mo-304 SS is suitable to be used as proton exchange membrane fuel cell (PEMFC) bipolar plate. The corrosion resistance and the passivated behavior of the Mo-304 SS are improved, which yield better results than those found in the untreated 304 SS after the potentiodynamic and potentiostatic polarization under simulated typical PEMFC operating conditions (0.05 M H2SO4 +2 ppm F− solution at 70 °C purged with either hydrogen or air). Also, the interfacial contact resistance for the as-prepared Mo-304 SS is ameliorated. The molybdenum modified 304 SS can be a promising candidate bipolar plate for proton exchange membrane fuel cell.
Effects of using vortex tubes on events during cold start of a direct injection diesel engine
Authors: Çelik Adem , Akif Ceviz Mehmet , Yilmaz Mehmet , Volkan Öner İlhan , Karagöz Şendoğan
Published: March 2013

Vortex tubes use a compressed gas flow and separate it into low and high temperature regions without using any moving mechanical parts. Cold and hot exhaust flows of vortex tubes can be used for different purposes. In this study, a vortex tube was used to improve the cold start performance of a six cylinders, four stroke and direct injection diesel engine of a truck. To increase the engine intake air temperature, hot exhaust of vortex tube was introduced to the engine intake manifold. Pressured air was supplied to the vortex tube from the air tank of the compressed-air brake system of the truck. Variation in the cold starting events was observed by both in cylinder pressure data and revolution of engine crank shaft. Experiments were started when the ambient air and engine cooling fluid temperatures were at 0 °C, which is a critical temperature for cold-starting diesel engines. Experimental results showed that the cold starting performance of the engine can be successfully improved by using vortex tubes. Durations of engine starting-cranking, cranking-idling, and idling-stabling were decreased due to the increase in the intake air temperature.
Effects of proton-conducting electrolyte microstructure on the performance of electrolyte-supported solid oxide fuel cells
Authors: Sui Jing , Cao Lei , Zhu Qianqian , Yu Liyan , Zhang Qian , Dong Lifeng
Published: March 2013

Three kinds of proton-conducting electrolyte powder BaCe0.8Sm0.2O2.9 (BCS) with different microstructures are synthesized by three different methods: EDTA-citrate method, EDTA-citrate and ball-milling method, and hydrothermal method. X-ray diffraction and scanning electron microscopy are used to investigate the microstructure and morphology of the BCS powders, and electrochemical measurements and impedance spectroscopy are employed to analyze electrical characteristics of the electrolyte-supported solid oxide fuel cells (SOFCs). It is found that the performance of electrolyte-supported SOFCs strongly depends upon the electrolyte microstructure, which is dominated by the synthesis methods. At the operating temperature of 650 °C, the highest SOFC performance (80 mW/cm2) is obtained from the cell with nanostructured proton conducting electrolyte powder synthesized by the hydrothermal method, while the lowest performance (17 mW/cm2) is the cell with the largest grain powder synthesized by the EDTA-citrate method without ball-milling treatment.
Emission of radiation induced by pervading Alfvén waves
Authors: Zhao G. Q. , Wu C. S.
Published: March 2013

It is shown that under certain conditions, propagating Alfvén waves can energize electrons so that consequently a new cyclotron maser instability is born. The necessary condition is that the plasma frequency is lower than electron gyrofrequency. This condition implies high Alfvén speed, which can pitch-angle scatter electrons effectively and therefore the electrons are able to acquire free energy which are needed for the instability.
Mechanoelectric transduction in ionic polymer-metal composite
Authors: Tiwari Rashi , Kim Kwang J.
Published: March 2013

The ability of ionic polymer-metal composite (IPMC) to generate current on mechanical deformation, defined as mechanoelectric transduction, can be exploited for design and development of numerous sensors and energy harvesters. However, sensor application of IPMC is currently limited due to the lack of understanding of the transduction mechanism. This paper presents a physics-based mechanoelectric model that takes into account material properties, electrostatic phenomenon, and ion transport in the IPMC. Experimental verification of the model predictions is also reported.
Mechanical oscillation of kinked silicon nanowires: A natural nanoscale spring
Authors: Jiang Jin-Wu , Rabczuk Timon
Published: March 2013

We perform classical molecular dynamics simulations to demonstrate the application of kinked silicon nanowires (KSiNWs) as nanoscale springs. The spring-like oscillation in gigahertz frequency range is successfully actuated using a similar procedure as the actuation of a classical mass spring oscillator. We detect the spring-like mechanical oscillation and some other low-frequency oscillations by the energy spectrum analysis, where a dimensional crossover phenomenon is observed for the transverse mode in KSiNWs with decreasing aspect ratio. Our findings shed light on the elastic properties of the KSiNW and open a way for its application in nanomechanical devices.
Small angle x-ray scattering and electron microscopy of nanoparticles formed in an electrical arc
Authors: Carvou E. , Garrec J. L. Le , Pérez J. , Praquin J. , Djeddi M. , Mitchell J. B. A.
Published: March 2013

Small Angle X-ray Scattering has been used to characterize nanoparticles generated by electrical arcing between metallic (AgSnO2) electrodes. The particles are found to have diameters between 30 and 40 nm and display smooth surfaces suggesting that they are either in liquid form or have solidified from the liquid state. Particles collected around the electrodes were analyzed by Transmission Electron Microscopy and were seen to be much larger than those seen in the SAXS measurement, to be spherical in form and composed of silver metal with irregular tin oxide particles deposited on their surface. Mixed metal nanoparticles can have important practical applications and the use of mixed sintered electrodes may be a direct method for their production.
Mechanism of voltage-sensitive fluorescence in a microbial rhodopsin
Authors: Maclaurin Dougal , Venkatachalam Veena , Lee Hohjai , Cohen Adam E.
Published: March 2013

Microbial rhodopsins were recently introduced as genetically encoded fluorescent indicators of membrane voltage. An understanding of the mechanism underlying this function would aid in the design of improved voltage indicators. We asked, what states can the protein adopt, and which states are fluorescent? How does membrane voltage affect the photostationary distribution of states? Here, we present a detailed spectroscopic characterization of Archaerhodopsin 3 (Arch). We performed fluorescence spectroscopy on Arch and its photogenerated intermediates in
Escherichia coli
and in single HEK293 cells under voltage-clamp conditions. These experiments probed the effects of time-dependent illumination and membrane voltage on absorption, fluorescence, membrane current, and membrane capacitance. The fluorescence of Arch arises through a sequential three-photon process. Membrane voltage modulates protonation of the Schiff base in a 13-
cis
photocycle intermediate (
M
⇌
N
equilibrium), not in the ground state as previously hypothesized. We present experimental protocols for optimized voltage imaging with Arch, and we discuss strategies for engineering improved rhodopsin-based voltage indicators.
Magnitude and variation of prehistoric bird extinctions in the Pacific
Authors: Duncan Richard P. , Boyer Alison G. , Blackburn Tim M.
Published: March 2013

The largest extinction event in the Holocene occurred on Pacific islands, where Late Quaternary fossils reveal the loss of thousands of bird populations following human colonization of the region. However, gaps in the fossil record mean that considerable uncertainty surrounds the magnitude and pattern of these extinctions. We use a Bayesian mark-recapture approach to model gaps in the fossil record and to quantify losses of nonpasserine landbirds on 41 Pacific islands. Two-thirds of the populations on these islands went extinct in the period between first human arrival and European contact, with extinction rates linked to island and species characteristics that increased susceptibility to hunting and habitat destruction. We calculate that human colonization of remote Pacific islands caused the global extinction of close to 1,000 species of nonpasserine landbird alone; nonpasserine seabird and passerine extinctions will add to this total.
Potential shortfall of pyramided transgenic cotton for insect resistance management
Authors: Brévault Thierry , Heuberger Shannon , Zhang Min , Ellers-Kirk Christa , Ni Xinzhi , Masson Luke , Li Xianchiun , Tabashnik Bruce E. , Carrière Yves
Published: March 2013

To delay evolution of pest resistance to transgenic crops producing insecticidal proteins from
Bacillus thuringiensis
(Bt), the “pyramid” strategy uses plants that produce two or more toxins that kill the same pest. In the United States, this strategy has been adopted widely, with two-toxin Bt cotton replacing one-toxin Bt cotton. Although two-toxin plants are likely to be more durable than one-toxin plants, the extent of this advantage depends on several conditions. One key assumption favoring success of two-toxin plants is that they kill insects selected for resistance to one toxin, which is called “redundant killing.” Here we tested this assumption for a major pest,
Helicoverpa zea
, on transgenic cotton producing Bt toxins Cry1Ac and Cry2Ab. Selection with Cry1Ac increased survival on two-toxin cotton, which contradicts the assumption. The concentration of Cry1Ac and Cry2Ab declined during the growing season, which would tend to exacerbate this problem. Furthermore, analysis of results from 21 selection experiments with eight species of lepidopteran pests indicates that some cross-resistance typically occurs between Cry1A and Cry2A toxins. Incorporation of empirical data into simulation models shows that the observed deviations from ideal conditions could greatly reduce the benefits of the pyramid strategy for pests like
H. zea,
which have inherently low susceptibility to Bt toxins and have been exposed extensively to one of the toxins in the pyramid before two-toxin plants are adopted. For such pests, the pyramid strategy could be improved by incorporating empirical data on deviations from ideal assumptions about redundant killing and cross-resistance.