bluuebunny/crossref_metadata_2025 huggingface dataset:
I - Introduction: Background and Problems
Authors: Rutherford Richard
Published: March 2013

EPICI have lived in important places, timesWhen great events were decided, who ownedThat half a rood of rock, a no-man's landSurrounded by our pitchfork-armed claims.I heard the Duffys shouting ‘Damn your soul’And old McCabe stripped to the waist, seenStep the plot defying blue cast-steel—‘Here is the march along these iron stones’That was the year of the Munich bother. WhichWas more important? I inclinedTo lose my faith in Ballyrush and GortinTill Homer's ghost came whispering to my mindHe said: I made the Iliad from suchA local row. Gods make their own importance.1
Patrick Kavanagh's short poem confronts the reader with a number of questions which will preoccupy us in this survey. The Homeric poems show us a world which in many respects seems primitive and remote; even if the expedition of the Greeks against Troy really happened, even if it took place on the scale which the Iliad asserts, and lasted the full ten-year span, it would still be ‘a local row’ compared with later historical conflicts, ancient or modern. Can the bad-tempered disputes of warrior chiefs, the violent revenge of a savage and undisciplined soldier, the lies and posturing of a vagabond rogue, still move or excite an audience today? It will be necessary to show here some of the ways in which Homer gives the conflict at Troy, and the homecoming of Odysseus, a timeless importance, so that these mere episodes in the vanished heroic age – long past even for the poet and his audience – become microcosmic images of human life. The vast subject of Homer's influence upon later western literature cannot be even superficially addressed here; but occasional comparisons and illustrations may help to show how much subsequent poets and artists have found in the Iliad and the Odyssey to enlighten and inspire their own work.
Geoffrey Francis Hattersley-Smith (‘Geoff’)
Authors: Stonehouse Bernard
Published: March 2013

Geoffrey Francis Hattersley-Smith (‘Geoff’), who died on 21 July 2012, served for many years as a polar field scientist, contributing substantially to glaciological and geological surveys in both north and south polar regions. In later life he undertook research in another discipline altogether – the sorting and cataloguing of polar place names – an achievement in scholarship for which all other polar researchers may be thankful.
L2 perception of Spanish palatal variants across different tasks
Authors: SHEA CHRISTINE , RENAUD JEFFREY
Published: March 2013

While considerable dialectal variation exists, almost all varieties of Spanish exhibit some sort of alternation in terms of the palatal obstruent segments. Typically, the palatal affricate [ɟʝ] tends to occur in word onset following a pause and in specific linear phonotactic environments. The palatal fricative [ʝ] tends to occur in syllable onset in other contexts. We show that listeners’ perceptual sensitivity to the palatal alternation depends upon the task and exposure to Spanish input. For native Spanish listeners, the palatal alternation boosts segmentation accuracy on an artificial speech segmentation task and also reduces latencies on a phonotactically-conditioned elision task. L2 Spanish listeners, on the other hand, only benefit from the palatal alternation in the second task. These results suggest that while Spanish L2 learners benefit from the presence of the alternation in linear phonotactic terms, this benefit does not carry over to a more abstract segmentation task.
MASS CONCENTRATION WITH MIXED NORM FOR A NONELLIPTIC SCHRÖDINGER EQUATION
Authors: HAM SEHEON
Published: March 2013

This paper is concerned with a mass concentration phenomenon for a two-dimensional nonelliptic Schrödinger equation. It is well known that this phenomenon occurs when the ${L}^{4} $-norm of the solution blows up in finite time. We extend this result to the case where a mixed norm of the solution blows up in finite time.
Disproportionate early fetal growth predicts postnatal thymic size in humans
Authors: Fulford A. J. C. , Moore S. E. , Arifeen S. E. , Persson L. Å. , Neufeld L. M. , Wagatsuma Y. , Prentice A. M.
Published: March 2013

Prenatal events can affect neonatal thymus size and adult immune function. The causal insults are unknown, although fetal nutrient restriction is suspected. We used ultrasound at three time points during pregnancy (14, 19 and 30 weeks) to measure the growth of six fetal dimensions in rural Bangladeshi women participating in the Maternal and Infant Nutrition Interventions, Matlab study. Postnatal ultrasound was used to calculate thymic index (TI) at birth, 2, 6 and 12 m. Of the 3267 women recruited, 2861 participated by providing data at least at one fetal biometry and one TI time point. Patterns of fetal growth were summarized using principal components calculated from fetal dimensionz-scores. Random effects regression, controlling for infant size and season of measurement were used to relate these patterns to TI. We found that smaller leg length relative to head circumference, characteristic of head-sparing growth restriction, was predictive of lower TI. This association was significant at all time points but strongest in earlier pregnancy. Each standard deviation increase in leg–head proportion was associated with an increase in TI of ∼5%. We conclude that growth patterns typical of poor fetal nutrition are associated with poor thymic development. The greater strength of this association in the first trimester is consistent with a period of vulnerability during the early ontogeny of the thymus and suggests that preventative intervention would need to be given in early pregnancy.
Couples’ Resolution of an Infertility Diagnosis Before Undergoing in Vitro Fertilization
Authors: Darwiche Joëlle , Favez Nicolas , Maillard Florine , Germond Marc , Guex Patrice , Despland Jean-Nicolas , de Roten Yves
Published: March 2013

Although the use of assisted reproductive technology has today become more familiar, the suffering associated with the experience of infertility remains. This study assesses the emotional resolution of couples faced with an infertility diagnosis by examining their narratives. Fifty-seven couples were recruited from fertility clinics to participate in a semistructured interview prior to in vitro fertilization. Two aspects of the couples’ reactions to the infertility diagnosis were assessed: (1) each individual’s capacity to acknowledge the emotional reality of the diagnosis (diagnosis resolution) and (2) the couple’s ability to construct a shared meaning of the infertility diagnosis experience (narrative co-construction). Associations between these aspects and self-reported marital satisfaction, infertility-related stress, and diagnosis-related variables were analyzed. 73.7% of women and 61.4% of men had acknowledged the emotional reality of the diagnosis, and their scores for narrative co-construction were comparable to reference samples. Marital satisfaction, but not infertility-related stress, was associated with diagnosis resolution and narrative co-construction. The results indicate the importance of detecting couples with fewer individual and marital resources needed to face the reality of the diagnosis. A couple’s capacity to perceive the infertility diagnosis as a shared problem is also essential for dealing with this common life event.
Exploring Audience Judgments of Social Science in Media Discourse
Authors: Sjöström Arne , Sowka Alexandra , Gollwitzer Mario , Klimmt Christoph , Rothmund Tobias
Published: March 2013

In contrast to research on the communication of “hard” sciences (e.g., nanotechnology), research on public assessments of social science’s role in media discourse is rare. Extending previous work on how the general audience perceives and assesses the quality of journalistic news reports about scientific research programs and their respective results, the present study explored how the lay audience perceives and evaluates the visibility of social sciences in the media discourse on controversial public issues (in this particular case, the violent video games debate). The results revealed that the public audience recognizes a high visibility of social sciences and furthermore believes that social sciences can substantially contribute to the public debate about violent video games and their effects. Moreover, we found a positive association between people’s recognition of social sciences in the debate and the quality of journalistic coverage on the violent video games debate. These findings are discussed with regard to their implications for research on public understanding of, and public engagement with, science.
The central role of selenium in the biochemistry and ecology of the harmful pelagophyte, Aureococcus anophagefferens
Authors: Gobler Christopher J , Lobanov Alexei V , Tang Ying-Zhong , Turanov Anton A , Zhang Yan , Doblin Martina , Taylor Gordon T , Sañudo-Wilhelmy Sergio A , Grigoriev Igor V , Gladyshev Vadim N
Published: March 2013

The trace element selenium (Se) is required for the biosynthesis of selenocysteine (Sec), the 21st amino acid in the genetic code, but its role in the ecology of harmful algal blooms (HABs) is unknown. Here, we examined the role of Se in the biology and ecology of the harmful pelagophyte, Aureococcus anophagefferens, through cell culture, genomic analyses, and ecosystem studies. This organism has the largest and the most diverse selenoproteome identified to date that consists of at least 59 selenoproteins, including known eukaryotic selenoproteins, selenoproteins previously only detected in bacteria, and novel selenoproteins. The A. anophagefferens selenoproteome was dominated by the thioredoxin fold proteins and oxidoreductase functions were assigned to the majority of detected selenoproteins. Insertion of Sec in these proteins was supported by a unique Sec insertion sequence. Se was required for the growth of A. anophagefferens as cultures grew maximally at nanomolar Se concentrations. In a coastal ecosystem, dissolved Se concentrations were elevated before and after A. anophagefferens blooms, but were reduced by >95% during the peak of blooms to 0.05 nm. Consistent with this pattern, enrichment of seawater with selenite before and after a bloom did not affect the growth of A. anophagefferens, but enrichment during the peak of the bloom significantly increased population growth rates. These findings demonstrate that Se inventories, which can be anthropogenically enriched, can support proliferation of HABs, such as A. anophagefferens through its synthesis of a large arsenal of Se-dependent oxidoreductases that fine-tune cellular redox homeostasis.
Proteomic analysis and molecular modelling characterize the iron-regulatory protein haemojuvelin/repulsive guidance molecule c
Authors: Nili Mahta , David Larry , Elferich Johannes , Shinde Ujwal , Rotwein Peter
Published: March 2013

HJV (haemojuvelin) plays a key role in iron metabolism in mammals by regulating expression of the liver-derived hormone hepcidin, which controls systemic iron uptake and release. Mutations in HJV cause juvenile haemochromatosis, a rapidly progressing iron overload disorder in humans. HJV, also known as RGMc (repulsive guidance molecule c), is a member of the three-protein RGM family. RGMs are GPI (glycosylphosphatidylinositol)-linked glycoproteins that share ~50% amino acid identity and several structural motifs, including the presence of 14 cysteine residues in analogous locations. Unlike RGMa and RGMb, HJV/RGMc is composed of both single-chain and two-chain isoforms. To date there is no structural information for any member of the RGM family. In the present study we have mapped the disulfide bonds in mouse HJV/RGMc using a proteomics strategy combining sequential MS steps composed of ETD (electron transfer dissociation) and CID (collision-induced dissociation), in which ETD induces cleavage of disulfide linkages, and CID establishes disulfide bond assignments between liberated peptides. The results of the present study identified an HJV/RGMc molecular species containing four disulfide linkages. We predict using ab initio modelling that this molecule is a single-chain HJV/RGMc isoform. Our observations outline a general approach using tandem MS and ab initio molecular modelling to define unknown structural features in proteins.
Co-operative function and mutual stabilization of the half ATP-binding cassette transporters HAF-4 and HAF-9 in Caenorhabditis elegans
Authors: Tanji Takahiro , Nishikori Kenji , Shiraishi Hirohisa , Maeda Masatomo , Ohashi-Kobayashi Ayako
Published: March 2013

Caenorhabditis elegans HAF-4 and HAF-9 are half ABC (ATP-binding-cassette) transporters that are highly homologous to the human lysosomal peptide transporter TAPL [TAP (transporter associated with antigen processing)-like; ABCB9]. We reported previously that both HAF-4 and HAF-9 localize to the membrane of a subset of intestinal organelles, and are required for the formation of these organelles and other physiological aspects. In the present paper, we report the genetic and physical interactions between HAF-4 and HAF-9. Overexpression of HAF-4 and HAF-9 did not rescue the intestinal organelle defect of the haf-9 and haf-4 deletion mutants respectively, indicating that they cannot substitute for each other. Double haf-4 and haf-9 mutants do not exhibit more severe phenotypes than the single mutants, suggesting their co-operative function. Immunoprecipitation experiments demonstrated their physical interaction. The results of the present study suggest that HAF-4 and HAF-9 form a heterodimer. Furthermore, Western blot analysis of the deletion mutants and RNAi (RNA interference) knockdown experiments in GFP (green fluorescent protein)-tagged HAF-4 or HAF-9 transgenic worms suggest that HAF-4–HAF-9 heterodimer formation is required for their stabilization. The findings provide a clue as to how ABC transporters adopt a stable functional form.
Theoretical study on low-lying electronic states of Kr2+, Xe2+, and Rn2+
Authors: Liang Yan-Ni , Wang Fan , Guo Jingwei
Published: March 2013

In this work, the equation-of-motion coupled-cluster approach with spin-orbit coupling (SOC) for ionization potentials (IP) at the singles and doubles level (EOMIP-CCSD) is employed to calculate spectroscopic constants of low-lying states of rare gas dimer ions Kr2+, Xe2+, and Rn2+. Two approaches are proposed to include contributions of triples: (1) energies of these states are calculated by adding the IPs from EOMIP-CCSD and the CCSD(T) energy of the rare gas dimers and (2) CCSD(T) energies without SOC for Rg2+ are first calculated and energies of these states with SOC are determined subsequently using the SOC matrix between these states. The first approach can provide accurate results for the three most stable states, while overestimates bond lengths for the other states. The second approach has been adopted previously and the SOC matrix element between 2Σ1/2+ and 2Π1/2 states was set to be ${\bf 1}/\sqrt {\bf 2}$1/2 times that of the SOC constant. In our work, the SOC matrix elements are determined from the calculated IPs and reasonable results for these states can be achieved with this approach, which could be useful for experimental works.
Translocation of a polymer through a nanopore modulated by a sticky site
Authors: de Haan Hendrick W. , Slater Gary W.
Published: March 2013

Using a one-dimensional model for the translocation of a polymer through a nanopore, the effect of a “sticky site” at which the polymer binds to the pore is explored via exact numerical techniques. Results for the mean translocation time and the probability of translocation on the insertion of the first monomer in the pore are generated across a wide range of driving forces and binding potential strengths (well depths). The balance between the driving force, diffusion, and well depth yields a rich set of dynamics that depend strongly on where the sticky site is located along the polymer. For example, when the sticky site is located near the head of the polymer, the translocation time is found to be a maximum at an intermediate driving force with events at lower driving forces taking less time. Additionally, the critical well depth at which the sticky site dominates the dynamics, is found to be a non-monotonic function of the driving force when the sticky site is located at the head or tail of the polymer, but not in the middle. Modeling of the process yields good agreement with simulation results.
Minimizing memory as an objective for coarse-graining
Authors: Guttenberg Nicholas , Dama James F. , Saunders Marissa G. , Voth Gregory A. , Weare Jonathan , Dinner Aaron R.
Published: March 2013

Coarse-graining a molecular model is the process of integrating over degrees of freedom to obtain a reduced representation. This process typically involves two separate but related steps, selection of the coordinates comprising the reduced system and modeling their interactions. Both the coordinate selection and the modeling procedure present challenges. Here, we focus on the former. Typically, one seeks to integrate over the fast degrees of freedom and retain the slow degrees of freedom. Failure to separate timescales results in memory. With this motivation, we introduce a heuristic measure of memory and show that it can be used to compare competing coordinate selections for a given modeling procedure. We numerically explore the utility of this heuristic for three systems of increasing complexity. The first example is a four-particle linear model, which is exactly solvable. The second example is a sixteen-particle nonlinear model; this system has interactions that are characteristic of molecular force fields but is still sufficiently simple to permit exhaustive numerical treatment. The third example is an atomic-resolution representation of a protein, the class of models most often treated by relevant coarse-graining approaches; we specifically study an actin monomer. In all three cases, we find that the heuristic suggests coordinate selections that are physically intuitive and reflect molecular structure. The memory heuristic can thus serve as an objective codification of expert knowledge and a guide to sites within a model that requires further attention.
Revised structural phase diagram of (Ba0.7Ca0.3TiO3)-(BaZr0.2Ti0.8O3)
Authors: Keeble Dean S. , Benabdallah Feres , Thomas Pam A. , Maglione Mario , Kreisel Jens
Published: March 2013

The temperature-composition phase diagram of barium calcium titanate zirconate (x(Ba0.7Ca0.3TiO3)-(1 − x)(BaZr0.2Ti0.8O3); BCTZ) has been reinvestigated using high-resolution synchrotron x-ray powder diffraction. Contrary to previous reports of an unusual rhombohedral-tetragonal phase transition in this system, we have observed an intermediate orthorhombic phase, isostructural to that present in the parent phase, BaTiO3, and we identify the previously assigned T-R transition as a T-O transition. We also observe the O-R transition coalescing with the previously observed triple point, forming a phase convergence region. The implication of the orthorhombic phase in reconciling the exceptional piezoelectric properties with the surrounding phase diagram is discussed.
Impact of electronic defects on the Raman spectra from electrodeposited Cu(In,Ga)Se2 solar cells: Application for non-destructive defect assessment
Authors: Ruiz C. M. , Fontané X. , Fairbrother A. , Izquierdo-Roca V. , Broussillou C. , Bodnar S. , Pérez-Rodríguez A. , Bermúdez V.
Published: March 2013

This work reports on the electrical and Raman scattering analysis of Cu(In,Ga)Se2 cells synthesised with different densities of Se and Cu related point defects. The analysis of the Raman spectra from the surface region of the absorbers shows a direct correlation between the spectral features of the main Raman peak and the density of Se vacancies detected by admittance spectroscopy, being sensitive to the presence of vacancy densities higher than 1015 cm−3. These results corroborate the potential of Raman scattering for the non-destructive detection of electronic defects with potential impact on the characteristics of the solar cells.
Continuous-wave coherent imaging with terahertz quantum cascade lasers using electro-optic harmonic sampling
Authors: Ravaro M. , Jagtap V. , Santarelli G. , Sirtori C. , Li L. H. , Khanna S. P. , Linfield E. H. , Barbieri S.
Published: March 2013

We demonstrate a coherent imaging system based on a terahertz (THz) frequency quantum cascade laser (QCL) phase-locked to a near-infrared fs-laser comb. The phase locking enables coherent electro-optic sampling of the continuous-wave radiation emitted by the QCL through the generation of a heterodyne beat-note signal. We use this beat-note signal to demonstrate raster scan coherent imaging using a QCL emitting at 2.5 THz. At this frequency the detection noise floor of our system is of 3 pW/Hz and the long-term phase stability is <3°/h, limited by the mechanical stability of the apparatus.
Debye relaxation and 250 K anomaly in glass forming monohydroxy alcohols
Authors: Bauer S. , Burlafinger K. , Gainaru C. , Lunkenheimer P. , Hiller W. , Loidl A. , Böhmer R.
Published: March 2013

A previous dielectric, near-infrared (NIR), and nuclear magnetic resonance study on the hydrogen-bonded liquid 2-ethyl-1-hexanol [C. Gainaru et al., Phys. Rev. Lett. 107, 118304 (2011)10.1103/PhysRevLett.107.118304] revealed anomalous behavior in various static quantities near 250 K. To check whether corresponding observations can be made for other monohydroxy alcohols as well, these experimental methods were applied to such substances with 5, 6, 7, 8, and 10 carbon atoms in their molecular backbone. All studied liquids exhibit a change of behavior near 250 K, which is tentatively ascribed to effects of hydrogen bond cooperativity. By analyzing the NIR band intensities, a linear cluster size is derived that agrees with estimates from dielectric spectroscopy. All studied alcohols, except 4-methyl-3-heptanol, display a dominant Debye-like peak. Furthermore, neat 2-ethyl-1-butanol exhibits a well resolved structural relaxation in its dielectric loss spectrum, which so far has only been observed for diluted monohydroxy alcohols.
Effect of multiple time-delay on vibrational resonance
Authors: Jeevarathinam C. , Rajasekar S. , Sanjuán M. A. F.
Published: March 2013

We report our investigation on the effect of multiple time-delay on vibrational resonance in a single Duffing oscillator and in a system of n Duffing oscillators coupled unidirectionally and driven by both a low- and a high-frequency periodic force. For the single oscillator, we obtain analytical expressions for the response amplitude Q and the amplitude g of the high-frequency force at which resonance occurs. The regions in parameter space of enhanced Q at resonance, as compared to the case in absence of time-delay, show a bands-like structure. For the two-coupled oscillators, we explain all the features of variation of Q with the control parameter g. For the system of n-coupled oscillators with a single time-delay coupling, the response amplitudes of the oscillators are shown to be independent of the time-delay. In the case of a multi time-delayed coupling, undamped signal propagation takes place for coupling strength (δ) above a certain critical value (denoted as δu). Moreover, the response amplitude approaches a limiting value QL with the oscillator number i. We obtain analytical expressions for both δu and QL.
Effect of temperature and magnetic field on the electrical transport of polyaniline nanofibers
Authors: Nath Chandrani , Kumar A.
Published: March 2013

The detailed nature of conduction in polyaniline nanofibers has been studied as a function of temperature as well as magnetic field. Three batches of nanofibers doped with different levels of hydrochloric acid are synthesized by interfacial polymerization technique with an average diameter of 7.5 nm. The structural studies show an increase in crystallinity with doping while the Raman spectroscopy reveals polaron as the major charge carrier. All the samples show a metal-insulator transition around 16 K. At low temperature, the metallic conduction has been ascribed to electron-electron interaction effects while in the high temperature insulating regime, the conduction mainly occurs by variable range hopping mechanism among superlocalized states. All the materials exhibit a sizable amount of magnetoresistance at all temperatures. It is, however, intriguing that the nature of magnetoresistance changes from positive to negative with temperature, and the magnitude of magnetoresistance itself modifies with the doping concentration. We have qualitatively explained this behavior of magnetoresistance with a polaron-bipolaron based model.
Electron and laser beam-induced current measurements of diamond-like carbon films modified by scanning probe method
Authors: Hayashi Shigehiro , Han Younggun , Choi Woon , Tomokage Hajime
Published: March 2013

A nitrogen-doped diamond-like carbon (DLC) film deposited on n-type silicon is modified by applying an electric field in a vacuum between a tungsten tip and the DLC film surface using a scanning probe field emission current method. The resistance decreases and a Schottky barrier is formed between the modified DLC and the silicon surface, while micro-Raman measurements show a slight nano-crystalline graphitization. The electron beam induced current from the modified area is measured without any metal contact deposition. An infrared laser beam with a wavelength of 1400 nm is scanned across the backside of the silicon, and the induced current from the DLC modified area is measured. It is shown that both infrared laser and electron beam induced current measurements were possible for the modified DLC film on silicon structures.
Broadband and low loss high refractive index metamaterials in the microwave regime
Authors: Campbell T. , Hibbins A. P. , Sambles J. R. , Hooper I. R.
Published: March 2013

A broadband, low-loss, isotropic, high refractive index metamaterial comprising an array of close-packed cubic elements of cross-linked square metal plates is demonstrated in the microwave regime. The structuring of the cubic elements reduces the diamagnetic response exhibited by arrays of solid metal cubes, whilst maintaining the strongly enhanced permittivity arising from capacitative coupling between adjacent metal elements. The corresponding increase in refractive index can be tailored through appropriate structuring of the faces and/or spacing of the cubes.
Chemically modulated multiferroicity in Dy-doped Gd2Ti2O7
Authors: Lin L. , Zhao Z. Y. , Liu D. , Xie Y. L. , Dong S. , Yan Z. B. , Liu J.-M.
Published: March 2013

The ferroelectricity and magnetoelectric coupling of Gd2Ti2O7 and Gd2−xDyxTi2O7 with Dy3+ substitution of Gd3+ are investigated. For Gd2Ti2O7, a ferroelectric polarization emerges at ∼30 K and is only ∼1.80 μC/m2 at 2 K, while the magnetoelectric response is quite weak. The Dy3+ substitution in Gd2−xDyxTi2O7, however, results in significant enhancement of polarization with remarkable magnetoelectric response up to 35% at 2 K under a magnetic field of 9 T, suggesting the multiferroicity of Gd2−xDyxTi2O7. It is understood that the chemical modulation of the multiferroicity is basically related to the extreme sensitivity of the spin-spin interactions in this highly frustrated system.
Structural and magnetic properties in Heusler-type ferromagnet/antiferromagnet bilayers
Authors: Fukatani N. , Inagaki K. , Miyawaki T. , Ueda K. , Asano H.
Published: March 2013

The structure and magnetic properties of Heusler ferromagnet/antiferromagnet (FM/AFM) bilayers were investigated. Structural characterization revealed that Fe2CrSi/Ru2MnGe bilayers were epitaxially grown with an L21 ordered structure when the Ru2MnGe growth temperature was 573 K. The magnetization curve indicates that exchange bias occurs in the Fe2CrSi/Ru2MnGe bilayers at 77 K. The appearance of an exchange-anisotropy field Hex depends on the growth of Ru2MnGe layer, indicating that the exchange bias originates from the epitaxial Fe2CrSi/Ru2MnGe interface. The exchange anisotropy energy Jk of the Fe2CrSi/Ru2MnGe and Co2MnGe/Ru2MnGe bilayer systems appears to follow a Heisenberg-like exchange coupling model. This suggests that the Cr and Mn interface atoms in the FM layers play significant roles in exchange coupling in the Fe2CrSi/Ru2MnGe and Co2MnGe/Ru2MnGe bilayer systems, respectively.
Magnetic field advection in two interpenetrating plasma streams
Authors: Ryutov D. D. , Kugland N. L. , Levy M. C. , Plechaty C. , Ross J. S. , Park H. S.
Published: March 2013

Laser-generated colliding plasma streams can serve as a test-bed for the study of various astrophysical phenomena and the general physics of self-organization. For streams of a sufficiently high kinetic energy, collisions between the ions of one stream with the ions of the other stream are negligible, and the streams can penetrate through each other. On the other hand, the intra-stream collisions for high-Mach-number flows can still be very frequent, so that each stream can be described hydrodynamically. This paper presents an analytical study of the effects that these interpenetrating streams have on large-scale magnetic fields either introduced by external coils or generated in the plasma near the laser targets. Specifically, a problem of the frozen-in constraint is assessed and paradoxical features of the field advection in this system are revealed. A possibility of using this system for studies of magnetic reconnection is mentioned.
Hydrodynamic simulations of long-scale-length two-plasmon–decay experiments at the Omega Laser Facility
Authors: Hu S. X. , Michel D. T. , Edgell D. H. , Froula D. H. , Follett R. K. , Goncharov V. N. , Myatt J. F. , Skupsky S. , Yaakobi B.
Published: March 2013

Direct-drive–ignition designs with plastic CH ablators create plasmas of long density scale lengths (Ln ≥ 500 μm) at the quarter-critical density (Nqc) region of the driving laser. The two-plasmon–decay (TPD) instability can exceed its threshold in such long-scale-length plasmas (LSPs). To investigate the scaling of TPD-induced hot electrons to laser intensity and plasma conditions, a series of planar experiments have been conducted at the Omega Laser Facility with 2-ns square pulses at the maximum laser energies available on OMEGA and OMEGA EP. Radiation–hydrodynamic simulations have been performed for these LSP experiments using the two-dimensional hydrocode draco. The simulated hydrodynamic evolution of such long-scale-length plasmas has been validated with the time-resolved full-aperture backscattering and Thomson-scattering measurements. draco simulations for CH ablator indicate that (1) ignition-relevant long-scale-length plasmas of Ln approaching ∼400 μm have been created; (2) the density scale length at Nqc scales as Ln(μm)≃(RDPP×I1/4/2); and (3) the electron temperature Te at Nqc scales as Te(keV)≃0.95×I, with the incident intensity (I) measured in 1014 W/cm2 for plasmas created on both OMEGA and OMEGA EP configurations with different-sized (RDPP) distributed phase plates. These intensity scalings are in good agreement with the self-similar model predictions. The measured conversion fraction of laser energy into hot electrons fhot is found to have a similar behavior for both configurations: a rapid growth [fhot≃fc×(Gc/4)6 for Gc < 4] followed by a saturation of the form, fhot≃fc×(Gc/4)1.2 for Gc ≥ 4, with the common wave gain is defined as Gc=3 × 10−2×IqcLnλ0/Te, where the laser intensity contributing to common-wave gain Iqc, Ln, Te at Nqc, and the laser wavelength λ0 are, respectively, measured in [1014 W/cm2], [μm], [keV], and [μm]. The saturation level fc is observed to be fc ≃ 10–2 at around Gc ≃ 4. The hot-electron temperature scales roughly linear with Gc. Furthermore, to mitigate TPD instability in long-scale-length plasmas, different ablator materials such as saran and aluminum have been investigated on OMEGA EP. Hot-electron generation has been reduced by a factor of 3–10 for saran and aluminum plasmas, compared to the CH case at the same incident laser intensity. draco simulations suggest that saran might be a better ablator for direct-drive–ignition designs as it balances TPD mitigation with an acceptable hydro-efficiency.
A wedge-mounting technique for nanoscale electron backscatter diffraction
Authors: Carpenter J. S. , McCabe R. J. , Beyerlein I. J. , Wynn T. A. , Mara N. A.
Published: March 2013

The practical spatial resolution of electron backscatter diffraction (EBSD) is around 100 nm, which limits the length scales from which phase and orientation relationship characterization can be accomplished. This precludes collection of statistically relevant data on the crystallography of interfaces within nanomaterials where such information is essential for understanding the unique properties of these materials. In this work, we present a wedge-mounting technique that enables EBSD data to be collected for sub-100 nm thick layers of Cu-Nb bimetallic multilayers fabricated via accumulative roll bonding. We present statistics on layer thickness distributions, grain morphology, orientation distributions, twin volume fraction, and interface character for material with an averaged layer thickness of 86 and 56 nm.
Epitaxial growth of radial Si p-i-n junctions for photovoltaic applications
Authors: Yoo Jinkyoung , Dayeh Shadi A. , Tang Wei , Picraux S. T.
Published: March 2013

Achieving high quality radial junctions in nanowire arrays with controlled doping profiles is critical for their potential photovoltaic applications. We present a low temperature epitaxial growth process for silicon radial p-n and p-i-n junction arrays on top-down fabricated nanowires using silane-based chemical vapor deposition. Epitaxial growth on [111] oriented nanowires of ∼300 nm diameter and up to 10 μm in length exhibits well-defined, single crystalline {110} faceted surfaces at temperatures as low as 710 °C. The growth rate G at 810 °C for intrinsic Si is greater than that for heavily B- and P-doped Si (Gi > Gp > Gn). Faceted growth morphology at the tip of the nanowires results in well-defined “match-head” structures for undoped and B-doped growth. Preliminary photovoltaic device arrays of ∼4 × 104 nanowires based on our radial epitaxial p-i-n junction growth approach achieve solar energy conversion efficiencies of 10% under AM 1.5 G illumination.
Particle-in-cell/Monte Carlo collision simulation of the ionization process of surface-wave plasma discharges resonantly excited by surface plasmon polaritons
Authors: Chen Zhaoquan , Ye Qiubo , Xia Guangqing , Hong Lingli , Hu Yelin , Zheng Xiaoliang , Li Ping , Zhou Qiyan , Hu Xiwei , Liu Minghai
Published: March 2013

Although surface-wave plasma (SWP) sources have many industrial applications, the ionization process for SWP discharges is not yet well understood. The resonant excitation of surface plasmon polaritons (SPPs) has recently been proposed to produce SWP efficiently, and this work presents a numerical study of the mechanism to produce SWP sources. Specifically, SWP resonantly excited by SPPs at low pressure (0.25 Torr) are modeled using a two-dimensional in the working space and three-dimensional in the velocity space particle-in-cell with the Monte Carlo collision method. Simulation results are sampled at different time steps, in which the detailed information about the distribution of electrons and electromagnetic fields is obtained. Results show that the mode conversion between surface waves of SPPs and electron plasma waves (EPWs) occurs efficiently at the location where the plasma density is higher than 3.57 × 1017 m−3. Due to the effect of the locally enhanced electric field of SPPs, the mode conversion between the surface waves of SPPs and EPWs is very strong, which plays a significant role in efficiently heating SWP to the overdense state.
On thermodynamics in the primary power conversion of oscillating water column wave energy converters
Authors: Sheng Wanan , Alcorn Raymond , Lewis Anthony
Published: March 2013

The paper presents an investigation to the thermodynamics of the air flow in the air chamber for the oscillating water column wave energy converters, in which the oscillating water surface in the water column pressurizes or de-pressurises the air in the chamber. To study the thermodynamics and the compressibility of the air in the chamber, a method is developed in this research: the power take-off is replaced with an accepted semi-empirical relationship between the air flow rate and the oscillating water column chamber pressure, and the thermodynamic process is simplified as an isentropic process. This facilitates the use of a direct expression for the work done on the power take-off by the flowing air and the generation of a single differential equation that defines the thermodynamic process occurring inside the air chamber. Solving the differential equation, the chamber pressure can be obtained if the interior water surface motion is known or the chamber volume (thus the interior water surface motion) if the chamber pressure is known. As a result, the effects of the air compressibility can be studied. Examples given in the paper have shown the compressibility, and its effects on the power losses for large oscillating water column devices.
Suppressing void defects in long wavelength semipolar (202¯1¯) InGaN quantum wells by growth rate optimization
Authors: Zhao Yuji , Wu Feng , Huang Chia-Yen , Kawaguchi Yoshinobu , Tanaka Shinichi , Fujito Kenji , Speck James S. , DenBaars Steven P. , Nakamura Shuji
Published: March 2013

We report on void defect formation in (202¯1¯) semipolar InGaN quantum wells (QWs) emitting in the green spectral region. Fluorescence and transmission electron microscopy studies indicate that this type of defect is associated with voids with {101¯1}, {101¯0}, and {0001¯} side facets in the QW region. Systematic growth studies show that this defect can be effectively suppressed by reducing the growth rate for the active region. Green light-emitting diodes (LEDs) with reduced active region growth rate showed enhanced power and wavelength performance. The improved LED performance is attributed to the absence of void defects in the active region.
Polarization relaxation kinetics in ultrathin ferroelectric capacitors
Authors: Stamm A. , Kim D. J. , Lu H. , Bark C. W. , Eom C. B. , Gruverman A.
Published: March 2013

Electrical pulse measurements were used to study the polarization relaxation behavior of ultrathin epitaxial BaTiO3 ferroelectric capacitors and to assess the effect of interface engineering on the relaxation process. The relaxation behavior was described as a transition from a single- to a poly-domain state driven by an internal depolarizing field using the Kolmogorov-Avrami-Ishibashi switching model with a Lorentzian distribution of characteristic switching times. It was found that although the interface engineering stabilizes polarization to a larger value by removing a pinned interfacial dipole, the introduction of an additional polar discontinuity by interface engineering reduces screening effectiveness and leads to a larger depolarizing field and faster relaxation.
Post-fabrication, in situ laser reduction of graphene oxide devices
Authors: Petridis C. , Lin Y.-H. , Savva K. , Eda G. , Kymakis E. , Anthopoulos T. D. , Stratakis E.
Published: March 2013

We report on post-fabrication, in situ, laser induced reduction of graphene oxide (GO) field effect transistors. Our one-step method is efficient, fast, and elevates the conductivity of GO transistor channels by two orders of magnitude. Compared to other reduction techniques, it is facile and simple since it does not require any stringent experimental conditions. Most importantly, we show here that it can be applied for, in situ, post-fabrication reduction of GO devices without compromising any of its components. The physical properties of the laser-reduced graphene oxide were assessed by micro-Raman and X-ray photoelectron spectroscopy analysis and the electrical properties by electric field effect measurements. The application of this technique in other graphene-based optoelectronic devices, especially those fabricated on inexpensive and temperature sensitive flexible substrates such as plastic, is envisaged.
Electronic and phonon bandstructures of pristine few layer and metal doped graphene using first principles calculations
Authors: Gupta Sanjeev K. , Soni Himadri R. , Jha Prafulla K.
Published: March 2013

In the frame work of density functional theoretical calculations, the electronic and lattice dynamical properties of graphene (multilayers and supercell) have been systematically investigated and analyzed using the plane wave pseudopotentials within the generalized gradient approximation and local density approximation functional. We have also studied the functionalization of graphene by adsorption and absorption of transition metals like Al and Ag. We find that the electronic properties exhibit large sensitivity to the number of layers and doping. The Al and Ag doped graphene exhibits peak at Fermi level in the density of states arising from the flat bands near Fermi level. The bonding of metal atoms and graphene leads to a charge transfer between them and consequently shift Fermi level with respect to the conical point at K-point. The adsorption of Ag/Al atoms suggests an effective interaction between the adatoms and graphene layers without disturbing the original graphene structure of lower graphene layers. Compared to single layer graphene, the optical phonon E2g mode and out of plane ZA mode at Γ-point splits in the bi-, tri- and four- layer graphene. We observe a shift for highest optical branch at Dirac K- point. We find that the different derivatives of graphene have different phonon dispersion relations. We demonstrate that there is removal of degeneracy of ZO/ZA modes at K- point with transition metal doping. The highest optical phonon branch becomes flat at Dirac point with doping of transition metals. Our study points that the substituted graphene sheets can have potential applications in ordered-disordered separated quantum films with two to four layers of atoms and new nano devices using graphene.
Experimental investigation of a solar cooker based on parabolic dish collector with phase change thermal storage unit in Indian climatic conditions
Authors: Chaudhary Avinash , Kumar Amit , Yadav Avadhesh
Published: March 2013

Solar cooker based on parabolic dish collector with phase change thermal storage unit was investigated. In this experimental setup, solar cooker with phase change thermal storage unit was kept on absorber plate of parabolic dish collector. During day time, acetanilide (phase change material) stores solar heat and during evening, solar cooker is kept in the insulator box. Then, the phase change material delivers heat to the food. To enhance the performance of solar cooker, three cases have been considered: ordinary solar cooker, solar cooker with outer surface painted black, and solar cooker with outer surface painted black along with glazing. It was observed that solar cooker with outer surface painted black along with glazing performs better as compared to other cases. Also phase change material (PCM) in solar cooker with outer surface painted black stored 26.8% more heat as compared to PCM in ordinary solar cooker, whereas PCM in solar cooker with outer surface painted black along with glazing stored 32.3% more heat as compared to PCM in ordinary solar cooker.
Follicular dynamics and gene expression in granulosa cells, corpora lutea and oocytes from gilts of breeds with low and high ovulation rates
Authors: Silva P. V. , Guimarães S. E. F. , Guimarães J. D. , Nascimento C. S. , Lopes P. S. , Siqueira J. B. , Amorim L. S. , Fonseca e Silva F. , Foxcroft G. R.
Published: March 2013

Follicular dynamics and the expression of candidate genes using real-time polymerase chain reaction (PCR) were compared during the oestrous cycle of pig breeds with high (commercial line; n = 24) and low (local Brazilian Piau; n = 21) ovulation rates and prolificacy. Gilts were killed on Days 0, 4, 10 and 18 of the oestrous cycle and visible ovarian follicles were classified by follicular diameter. Recovered cumulus–oocyte complexes were classified as normal or atretic and frozen in liquid nitrogen until RNA extraction. Low ovulation rates and/or prolificacy in Piau gilts was associated with a different pattern of follicle development, with lower numbers of small follicles on Day 18, fewer large follicles on Days 0 and 18 (P ≤ 0.05) and a higher proportion of atretic follicles on Days 0 and 18 (P ≤ 0.05). Compared with commercial line gilts, less-prolific Piau gilts exhibited higher expression of apoptotic genes during luteolysis (CASP3 and FASL; P ≤ 0.05), decreased expression of TGFBR2 and BAX mRNA in the corpus luteum (P ≤ 0.05), higher expression of apoptotic genes (FAS, BCL2 and CASP8; P ≤ 0.05) in granulosa cells and a greater abundance (P ≤ 0.05) of genes controlling oocyte-secreted factors (GDF9, BMP15 and BMP6), suggesting underlying mechanisms controlling differences in follicular development, ovulation rate and inherent prolificacy in this pig breed.
Analysis of Mental Health Substance Abuse–Related Emergency Department Visits from 2002 to 2008
Authors: Chakravarthy Bharath , Tenny Montessa , Anderson Craig L. , Rajeev Sindhya , Istanbouli Tala , Lotfipour Shahram
Published: March 2013

Background

Mental health substance abuse (MHSA)-related visits in the emergency department (ED) are a growing concern.

Methods

This study analyzed MHSA ED visits by age, gender, ethnicity, region, season, and duration of stay between 2002 and 2008 using the National Hospital Ambulatory Care Survey (NHAMCS). The authors used descriptive statistics and examined ED length of stay using a generalized linear model with a log link, and compared length of stay for these visits.

Results

Mental health–related visits increased from 6.4% of visits in 2002 to 7.0% in 2008 ( P = .002). Substance abuse–related visits increased from 1.8% to 2.1% ( P = .004). Substance abuse-related visits accounted for a 49% increase (CI = 0.051–0.23%) in the total mental health visits to the ED. Male visits increased whereas female visits remained unchanged, with non-Latino white males showing the highest increase. The southern United States had the highest increase in MHSA visits. MHSA visits (5.6 hours) were on average 1.2 hours longer than other non–MHSA-related visits (4.4 hours). MHSA-related visits had a higher percentage of all visits on weekends (2.3%) than on weekdays (2.0%; P < .00005).

Conclusions

Concentrated programmatic efforts to decrease the burden of MHSA visits to the ED may reduce the burden of disease.
Conundrum, an ARHGAP18 orthologue, regulates RhoA and proliferation through interactions with Moesin
Authors: Neisch Amanda L. , Formstecher Etienne , Fehon Richard G.
Published: March 2013

RhoA, a small GTPase, regulates epithelial integrity and morphogenesis by controlling filamentous actin assembly and actomyosin contractility. Another important cytoskeletal regulator, Moesin (Moe), an ezrin, radixin, and moesin (ERM) protein, has the ability to bind to and organize cortical F-actin, as well as the ability to regulate RhoA activity. ERM proteins have previously been shown to interact with both RhoGEF (guanine nucleotide exchange factors) and RhoGAP (GTPase activating proteins), proteins that control the activation state of RhoA, but the functions of these interactions remain unclear. We demonstrate that Moe interacts with an unusual RhoGAP, Conundrum (Conu), and recruits it to the cell cortex to negatively regulate RhoA activity. In addition, we show that cortically localized Conu can promote cell proliferation and that this function requires RhoGAP activity. Surprisingly, Conu's ability to promote growth also appears dependent on increased Rac activity. Our results reveal a molecular mechanism by which ERM proteins control RhoA activity and suggest a novel linkage between the small GTPases RhoA and Rac in growth control.