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  • Oxford University Press  (21,336)
  • Hindawi  (19,371)
  • American Institute of Physics (AIP)  (15,980)
  • International Union of Crystallography (IUC)
  • 2010-2014  (58,018)
  • 1950-1954
  • 2014  (58,018)
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  • 2010-2014  (58,018)
  • 1950-1954
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  • 1
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    The Sensible Heat Flux in the Course of the Year at Ny-Ålesund, Svalbard: Characteristics of Eddy Covariance Data and Corresponding Model Results (2014)
    Hindawi
    In:  EPIC3Advances in Meteorology, Hindawi, pp. Article ID 852108, ISSN: 1687-9309
    Details
    Publication Date: 2020-03-05
    Description: In this paper we present one year of meteorological and flux measurements obtained near Ny-Ålesund, Spitsbergen. Fluxes are derived by the eddy covariance method and by a hydrodynamic model approach (HMA) as well. Both methods are compared and analyzed with respect to season and mean wind direction. Concerning the wind field we find a clear distinction between 3 prevailing regimes (which have influence on the flux behavior) mainly caused by the topography at the measurement site. Concerning the fluxes we find a good agreement between the HMA and the eddy covariance method in cases of turbulent mixing in summer but deviations at stable conditions, when the HMA almost always shows negative fluxes. Part of the deviation is based on a dependence of HMA fluxes on friction velocity and the influence of the molecular boundary layer. Moreover, the flagging system of the eddy covariance software package TK3 is briefly revised. A new quality criterion for the use of fluxes obtained by the eddy covariance method, which is based on integral turbulence characteristics, is proposed.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Post-seismic viscoelastic deformation and stress transfer after the 1960 M9.5 Valdivia, Chile earthquake : effects on the 2010 M8.8 Maule, Chile earthquake (2014)
    Oxford University Press
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2014. This article is posted here by permission of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 197 (2014): 697-704, doi:10.1093/gji/ggu048.
    Description: After the 1960 M9.5 Valdivia, Chile earthquake, three types of geodetic observations were made during four time periods at nearby locations. These post-seismic observations were previously explained by post-seismic afterslip on the downdip extension of the 1960 rupture plane. In this study, we demonstrate that the post-seismic observations can be explained alternatively by volumetric viscoelastic relaxation of the asthenosphere mantle. In searching for the best-fitting viscosity model, we invert for two variables, the thickness of the elastic lithosphere, He, and the effective Maxwell decay time of the asthenosphere mantle, TM, assuming a 100-km-thick asthenosphere mantle. The best solutions to fit the observations in four sequential time periods, 1960–1964, 1960–1968, 1965–1973 and 1980–2010, each yield a similar He value of about 65 km but significantly increasing TM values of 0.7, 6, 10 and 80 yr, respectively. We calculate the corresponding viscoelastic Coulomb stress increase since 1960 on the future rupture plane of the 2010 M8.8 Maule, Chile earthquake. The calculated viscoelastic stress increase on the 2010 rupture plane varies gradually from 13.1 bars at the southern end to 0.1 bars at the northern end. In contrast, the stress increase caused by an afterslip model has a similar spatial distribution but slightly smaller values of 0.1–3.2 bars on the 2010 rupture plane.
    Description: This work was supported by a MIT/WHOI Joint Program Student Fellowship and a Graduate Student Fellowship from the WHOI Deep Ocean Exploration Institute (MD), as well as NSF Grant OCE-1141785 and a Deerbrook Foundation Award (JL).
    Keywords: Seismic cycle ; Transient deformation ; Seismicity and tectonics ; Subduction zone processes ; Dynamics: seismotectonics ; South America
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Horizontal gene transfer is a significant driver of gene innovation in dinoflagellates (2014)
    Oxford University Press
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Genome Biology and Evolution 5 (2013): 2368-2381, doi:10.1093/gbe/evt179.
    Description: The dinoflagellates are an evolutionarily and ecologically important group of microbial eukaryotes. Previous work suggests that horizontal gene transfer (HGT) is an important source of gene innovation in these organisms. However, dinoflagellate genomes are notoriously large and complex, making genomic investigation of this phenomenon impractical with currently available sequencing technology. Fortunately, de novo transcriptome sequencing and assembly provides an alternative approach for investigating HGT. We sequenced the transcriptome of the dinoflagellate Alexandrium tamarense Group IV to investigate how HGT has contributed to gene innovation in this group. Our comprehensive A. tamarense Group IV gene set was compared with those of 16 other eukaryotic genomes. Ancestral gene content reconstruction of ortholog groups shows that A. tamarense Group IV has the largest number of gene families gained (314–1,563 depending on inference method) relative to all other organisms in the analysis (0–782). Phylogenomic analysis indicates that genes horizontally acquired from bacteria are a significant proportion of this gene influx, as are genes transferred from other eukaryotes either through HGT or endosymbiosis. The dinoflagellates also display curious cases of gene loss associated with mitochondrial metabolism including the entire Complex I of oxidative phosphorylation. Some of these missing genes have been functionally replaced by bacterial and eukaryotic xenologs. The transcriptome of A. tamarense Group IV lends strong support to a growing body of evidence that dinoflagellate genomes are extraordinarily impacted by HGT.
    Description: J.H.W. was supported by the NSF IGERT Program in Comparative Genomics at the University of Arizona (grant number DGE-0654435). This work was supported by grants from the National Science Foundation (grant numbers OCE-0723498, EF-0732440) and funding provided by the BIO5 Institute at the University of Arizona to J.D.H.
    Keywords: Gene innovation ; Alexandrium tamarense Group IV ; Phylogenetic profile ; Phylogenomics ; De novo transcriptome assembly ; Mitochondrial metabolism
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Magnetotelluric data, stable distributions and impropriety: an existential combination (2014)
    Oxford University Press
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Author, 2014. This article is posted here by permission of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 198 (2014): 622-636, doi: 10.1093/gji/ggu121.
    Description: The robust statistical model of a Gaussian core contaminated by outlying data that underlies robust estimation of the magnetotelluric (MT) response function has been re-examined. The residuals from robust estimators are systematically long tailed compared to a distribution based on the Gaussian, and hence are inconsistent with the robust model. Instead, MT data are pervasively described by the alpha stable distribution family whose variance and sometimes mean are undefined. A maximum likelihood estimator (MLE) that exploits the stable nature of MT data is formulated, and its two-stage implementation in which stable parameters are first fit to the data and then the MT responses are solved for is described. The MLE is shown to be inherently robust, but differs from the conventional robust estimator because it is based on a model derived from the data, while robust estimators are ad hoc, being based on the robust model that is inconsistent with actual data. Propriety versus impropriety of the complex MT response was investigated, and a likelihood ratio test for propriety and its null distribution was established. The Cramér-Rao lower bounds for the covariance matrix of proper and improper MT responses were specified. The MLE was applied to exemplar long period and broad-band data sets from South Africa. Both are shown to be significantly stably distributed using the Kolmogorov–Smirnov goodness of fit and Ansari-Bradley non-parametric dispersion tests. Impropriety of the MT responses at both sites is pervasive, hence the improper Cramér-Rao bound was used to estimate the MLE covariance. The MLE is shown to be nearly unbiased and well described by a Gaussian distribution based on bootstrap simulation. The MLE was compared to a conventional robust estimator, establishing that the standard errors of the former are systematically smaller than for the latter and that the standardized differences between them exhibit excursions that are both too frequent and too large to be described by a Gaussian model. This is ascribed to pervasive bias of the robust estimator that is to some degree obscured by their systematically large confidence bounds. Finally, a series of topics for further investigation is proposed.
    Description: This work was supported by NSF grant EAR0809074.
    Keywords: Time series analysis ; Numerical approximations and analysis ; Fractals and multifractals ; Probability distributions ; Magnetotellurics
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Virus infection of Haptolina ericina and Phaeocystis pouchetii implicates evolutionary conservation of programmed cell death induction in marine haptophyte–virus interactions (2014)
    Oxford University Press
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Plankton Research 36 (2014): 943-955, doi:10.1093/plankt/fbu029.
    Description: The mechanisms by which phytoplankton cope with stressors in the marine environment are neither fully characterized nor understood. As viruses are the most abundant entities in the global ocean and represent a strong top-down regulator of phytoplankton abundance and diversity, we sought to characterize the cellular response of two marine haptophytes to virus infection in order to gain more knowledge about the nature and diversity of microalgal responses to this chronic biotic stressor. We infected laboratory cultures of the haptophytes Haptolina ericina and Phaeocystis pouchetii with CeV-01B or PpV-01B dsDNA viruses, respectively, and assessed the extent to which host cellular responses resemble programmed cell death (PCD) through the activation of diagnostic molecular and biochemical markers. Pronounced DNA fragmentation and activation of cysteine aspartate-specific proteases (caspases) were only detected in virus-infected cultures of these phytoplankton. Inhibition of host caspase activity by addition of the pan-caspase inhibitor z-VAD-fmk did not impair virus production in either host–virus system, differentiating it from the Emiliania huxleyi-Coccolithovirus model of haptophyte–virus interactions. Nonetheless, our findings point to a general conservation of PCD-like activation during virus infection in ecologically diverse haptophytes, with the subtle heterogeneity of cell death biochemical responses possibly exerting differential regulation on phytoplankton abundance and diversity.
    Description: Funding to J.L.R, R.-A.S. and A.L. was provided by the Norwegian Research Council for the “VIPMAP” (nr. 186142) and “HAPTODIV” (nr. 190307) projects, and by the European Research Council Advanced Grant ERC-AG-LS8 “Microbial Network Organisation” (MINOS, project number 250254). J.L.R. received a FRIBIO overseas research fellowship from the Norwegian Research Council. K.D.B. and B.V.M. were supported by funding from the United States National Science Foundation (OCE-1061883).
    Keywords: Caspase ; DNA fragmentation ; IETD ; Phycodnaviridae ; z-VAD-fmk ; Haptophyte
    Repository Name: Woods Hole Open Access Server
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  • 6
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    The evolution of the four subunits of voltage-gated calcium channels : ancient roots, increasing complexity, and multiple losses (2014)
    Oxford University Press
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Genome Biology and Evolution 6 (2014): 2210-2217, doi:10.1093/gbe/evu177.
    Description: The alpha subunits of voltage-gated calcium channels (Cavs) are large transmembrane proteins responsible for crucial physiological processes in excitable cells. They are assisted by three auxiliary subunits that can modulate their electrical behavior. Little is known about the evolution and roles of the various subunits of Cavs in nonbilaterian animals and in nonanimal lineages. For this reason, we mapped the phyletic distribution of the four channel subunits and reconstructed their phylogeny. Although alpha subunits have deep evolutionary roots as ancient as the split between plants and opistokonths, beta subunits appeared in the last common ancestor of animals and their close-relatives choanoflagellates, gamma subunits are a bilaterian novelty and alpha2/delta subunits appeared in the lineage of Placozoa, Cnidaria, and Bilateria. We note that gene losses were extremely common in the evolution of Cavs, with noticeable losses in multiple clades of subfamilies and also of whole Cav families. As in vertebrates, but not protostomes, Cav channel genes duplicated in Cnidaria. We characterized by in situ hybridization the tissue distribution of alpha subunits in the sea anemone Nematostella vectensis, a nonbilaterian animal possessing all three Cav subfamilies common to Bilateria. We find that some of the alpha subunit subtypes exhibit distinct spatiotemporal expression patterns. Further, all six sea anemone alpha subunit subtypes are conserved in stony corals, which separated from anemones 500 MA. This unexpected conservation together with the expression patterns strongly supports the notion that these subtypes carry unique functional roles.
    Keywords: Voltage-gated calcium channel ; Ion channel ; Cnidaria ; Nematostella vectensis ; Evolution of nervous system
    Repository Name: Woods Hole Open Access Server
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  • 7
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    Multi-events earthquake early warning algorithm using a Bayesian approach (2014)
    Oxford University Press
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    Publication Date: 2014-12-13
    Description: Current earthquake early warning (EEW) systems lack the ability to appropriately handle multiple concurrent earthquakes, which led to many false alarms during the 2011 Tohoku earthquake sequence in Japan. This paper uses a Bayesian probabilistic approach to handle multiple concurrent events for EEW. We implement the theory using a two-step algorithm. First, an efficient approximate Bayesian model class selection scheme is used to estimate the number of concurrent events. Then, the Rao-Blackwellized Importance Sampling method with a sequential proposal probability density function is used to estimate the earthquake parameters, that is hypocentre location, origin time, magnitude and local seismic intensity. A real data example based on 2 months data (2011 March 9–April 30) around the time of the 2011 M 9 Tohoku earthquake is studied to verify the proposed algorithm. Our algorithm results in over 90 per cent reduction in the number of incorrect warnings compared to the existing EEW system operating in Japan.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 8
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    Extensive Copy Number Variations in Admixed Indian Population of African Ancestry: Potential Involvement in Adaptation (2014)
    Oxford University Press
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    Publication Date: 2014-12-13
    Description: Admixture mapping has been enormously resourceful in identifying genetic variations linked to phenotypes, adaptation, and diseases. In this study through analysis of copy number variable regions (CNVRs), we report extensive restructuring in the genomes of the recently admixed African-Indian population (OG-W-IP) that inhabits a highly saline environment in Western India. The study included subjects from OG-W-IP (OG), five different Indian and three HapMap populations that were genotyped using Affymetrix version 6.0 arrays. Copy number variations (CNVs) detected using Birdsuite were used to define CNVRs. Population structure with respect to CNVRs was delineated using random forest approach. OG genomes have a surprising excess of CNVs in comparison to other studied populations. Individual ancestry proportions computed using STRUCTURE also reveals a unique genetic component in OGs. Population structure analysis with CNV genotypes indicates OG to be distant from both the African and Indian ancestral populations. Interestingly, it shows genetic proximity with respect to CNVs to only one Indian population IE-W-LP4, which also happens to reside in the same geographical region. We also observe a significant enrichment of molecular processes related to ion binding and receptor activity in genes encompassing OG-specific CNVRs. Our results suggest that retention of CNVRs from ancestral natives and de novo acquisition of CNVRs could accelerate the process of adaptation especially in an extreme environment. Additionally, this population would be enormously useful for dissecting genes and delineating the involvement of CNVs in salt adaptation.
    Electronic ISSN: 1759-6653
    Topics: Biology
    Published by Oxford University Press
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  • 9
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    A catalogue of 2D photometric decompositions in the SDSS-DR7 spectroscopic main galaxy sample: preferred models and systematics (2014)
    Oxford University Press
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    Publication Date: 2014-12-12
    Description: We present a catalogue of 2D, point spread function-corrected de Vacouleurs, Sérsic, de Vacouleurs+Exponential, and Sérsic+Exponential fits of ~7 x 10 5 spectroscopically selected galaxies drawn from the Sloan Digital Sky Survey (SDSS) Data Release 7. Fits are performed for the SDSS r band utilizing the fitting routine galfit and analysis pipeline pymorph . We compare these fits to prior catalogues. Fits are analysed using a physically motivated flagging system. The flags suggest that more than 90 per cent of two-component fits can be used for analysis. We show that the fits follow the expected behaviour for early and late galaxy types. The catalogues provide a robust set of structural and photometric parameters for future galaxy studies. We show that some biases remain in the measurements, e.g. the presence of bars significantly affect the bulge measurements although the bulge ellipticity may be used to separate barred and non-barred galaxies, and about 15 per cent of bulges of two-component fits are also affected by resolution. The catalogues are available in electronic format. We also provide an interface for generating postage stamp images of the 2D model and residual as well as the 1D profile. These images can be generated for a user-uploaded list of galaxies on demand.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    Bio-Optical Characteristics of the Northern Gulf of California during June 2008 (2014)
    Hindawi
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    Publication Date: 2014-12-08
    Description: Bio-optical variables in the Northern Gulf of California were analyzed using in situ and satellite data obtained during a cruise in June 2008. The study area was divided into three bio-optical regions: Upper Gulf (UG), Northern Gulf (NG), and Great Isles (GI). Each region was characterized according to phytoplankton pigment concentration, phytoplankton and nonpigmented material spectral absorption coefficients, and spectral reflectance. Observed patterns were an indication of the shift in bio-optical conditions from north to south going from turbid and eutrophic waters to mesotrophic ones. Although there was a good agreement between satellite and in situ Chla (RMSE ±33%), an overestimation of in situ Chla was observed. This was partly explained by the presence of nonalgal particles, as well as the influence of desert and continental aerosols, which is generally overcorrected in the standard processing. The UG and NG could be considered as Case  2 waters, but they did exhibit different bio-optical characteristics. This implies that both biological and optical properties should be invoked to better understand water reflectance variability in the study region and its implications for the remote sensing of Chla and biogeochemical processes.
    Print ISSN: 1687-9406
    Electronic ISSN: 1687-9414
    Topics: Geosciences
    Published by Hindawi
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  • 11
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    The influence of charge injection from intermediate connectors on the performance of tandem organic light-emitting devices (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-13
    Description: Charge generation in a typical intermediate connector, composed of “n-type doped layer/transition metal oxide (TMO)/hole transporting layer (HTL),” of a tandem organic light-emitting device (OLED) has recently been found to arise from charge transfer at the TMO/HTL interfaces. In this paper, we investigate the effect of hole injection barriers from intermediate connectors on the performance of tandem OLEDs. The hole injection barriers are caused by the offset of the highest occupied molecular orbital (HOMO) energy levels between HTLs contained in the intermediate connector and the top electroluminescence (EL) unit. We also find that although charge generation can occur at the interfaces between the TMO and a wide variety of HTLs of different HOMO values, an increase in the hole injection barrier however limits the electroluminescence efficiency of the top EL units. In the case of large hole injection barriers, significant charge accumulation in the HTLs makes the intermediate connector lose its functionality gradually over operating time, and limits device stability.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 12
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    Stochastic Consensus of Single-Integrator Multiagent Systems with Inherent Nonlinear Dynamics and Measurement Noises in Directed Fixed Topologies (2014)
    Hindawi
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    Publication Date: 2014-12-08
    Description: Consensus of continuous-time single-integrator multiagent systems with inherent nonlinear dynamics and measurement noises is addressed in this paper. The consensus controller is developed for directed interaction topologies. Each agent’s control input is constructed based on its own state and its neighbors’ states corrupted by noises. The control input contains a time-varying consensus gain in order to attenuate the noises. Conditions for ensuring mean square convergence under noisy measurement and asymptotic convergence in the noise-free case are derived. Finally, some simulations were carried out to show the effectiveness of our control law and how it can solve the consensus problem.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 13
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    Phantom Eye Syndrome: A Review of the Literature (2014)
    Hindawi
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    Publication Date: 2014-12-08
    Description: The purpose of this literature review was to describe the main features of phantom eye syndrome in relation to their possible causes, symptoms, treatments, and influence of eye amputation on quality of life of anophthalmic patients. For this, a bibliographical research was performed in Pubmed database using the following terms: “eye amputation,” “eye trauma,” “phantom eye syndrome,” “phantom pain,” and “quality of life,” associated or not. Thirteen studies were selected, besides some relevant references contained in the selected manuscripts and other studies hallowed in the literature. Thus, 56 articles were included in this review. The phantom eye syndrome is defined as any sensation reported by the patient with anophthalmia, originated anophthalmic cavity. In phantom eye syndrome, at least one of these three symptoms has to be present: phantom vision, phantom pain, and phantom sensations. This syndrome has a direct influence on the quality of life of the patients, and psychological support is recommended before and after the amputation of the eyeball as well as aid in the treatment of the syndrome. Therefore, it is suggested that, for more effective treatment of phantom eye syndrome, drug therapy should be associated with psychological approach.
    Electronic ISSN: 1537-744X
    Topics: Natural Sciences in General
    Published by Hindawi
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  • 14
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    Effect of electron trap states on spin-dependent transport characteristics in CoFe/MgO/n+-Si junctions investigated by Hanle effect measurements and inelastic electron tunneling spectroscopy (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-09
    Description: Spin-dependent transport properties in CoFe/MgO/n + -Si junctions were investigated by Hanle effect measurements and inelastic electron tunneling (IET) spectroscopy. The CoFe/MgO/n + -Si junctions examined in this study exhibited two different Hanle curves. In the low bias region, broad Hanle signals were mainly observed; in the high bias region, narrow Hanle signals were mainly observed. The d 2 I / dV 2 - V curves (which correspond to IET spectra) contain several peaks originating from phonon modes and other peaks originating from electron trap states. At the bias voltage where electron trap states are observed, Δ d 2 I / dV 2 depends on the magnetic field and the full width at half-maximum of the Δ d 2 I / dV 2 – H curves corresponds to that of the broad Hanle signals. These results indicate that electron trap states are located in the low energy region and cause a decrease in spin lifetime.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 15
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    Carrier thermalization under stimulated emission in In0.17Ga0.83N epilayer at room temperature (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-09
    Description: We elucidate a strong room temperature stimulated emission (SE) of In 0.17 Ga 0.83 N epilayer grown by molecular beam epitaxy under the subpicosecond pulse excitation. The SE peak at 428 nm emerges on the higher energy side of the spontaneous emission in photoluminescence spectra when the excitation density exceeds the threshold of ∼3.68 mJ/cm 2 . Nondegenerate transient differential reflectivity measurements show that a multi-stage carrier thermalization from excited states to localized edge states and stimulated emission dominate the decay processes of photogenerated carriers under various excitation densities. Our results indicate that the existence of phonon bottleneck effect could result in a slow thermalization process in the InGaN material even under the condition of stimulated emission.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 16
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    Frustrated incomplete donor ionization in ultra-low resistivity germanium films (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-09
    Description: The relationship between carrier concentration and donor atomic concentration has been determined in n -type Ge films doped with P. The samples were carefully engineered to minimize non-active dopant incorporation by using specially designed P(SiH 3 ) 3 and P(GeH 3 ) 3 hydride precursors. The in situ nature of the doping and the growth at low temperatures, facilitated by the Ge 3 H 8 and Ge 4 H 10 Ge sources, promote the creation of ultra-low resistivity films with flat doping profiles that help reduce the errors in the concentration measurements. The results show that Ge deviates strongly from the incomplete ionization expected when the donor atomic concentration exceeds N d  = 10 17  cm −3 , at which the energy separation between the donor and Fermi levels ceases to be much larger than the thermal energy. Instead, essentially full ionization is seen even at the highest doping levels beyond the solubility limit of P in Ge. The results can be explained using a model developed for silicon by Altermatt and coworkers, provided the relevant model parameter is properly scaled. The findings confirm that donor solubility and/or defect formation, not incomplete ionization, are the major factors limiting the achievement of very high carrier concentrations in n -type Ge. The commercially viable chemistry approach applied here enables fabrication of supersaturated and fully ionized prototypes with potential for broad applications in group-IV semiconductor technologies.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 17
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    Reduction of skin effect losses in double-level-T-gate structure (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-09
    Description: We developed a T-gate technology based on selective wet etching yielding 200 nm wide T-gate structures used for fabrication of High Electron Mobility Transistors (HEMT). Major advantages of our process are the use of only standard photolithographic process and the ability to generate T-gate stacks. A HEMT fabricated on AlGaN/GaN/sapphire with gate length L g  = 200 nm and double-stacked T-gates exhibits 60 GHz cutoff frequency showing ten-fold improvement compared to 6 GHz for the same device with 2  μ m gate length. HEMTs with a double-level-T-gate (DLTG) structure exhibit up to 35% improvement of f max value compared to a single T-gate device. This indicates a significant reduction of skin effect losses in DLTG structure compared to its standard T-gate counterpart. These results agree with the theoretical predictions.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 18
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    Wake effects on drift in two-dimensional inviscid incompressible flows (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-12
    Description: This investigation analyzes the effect of vortex wakes on the Lagrangian displacement of particles induced by the passage of an obstacle in a two-dimensional incompressible and inviscid fluid. In addition to the trajectories of individual particles, we also study their drift and the corresponding total drift areas in the Föppl and Kirchhoff potential flow models. Our findings, which are obtained numerically and in some regimes are also supported by asymptotic analysis, are compared to the wakeless potential flow which serves as a reference. We show that in the presence of the Föppl vortex wake, some of the particles follow more complicated trajectories featuring a second loop. The appearance of an additional stagnation point in the Föppl flow is identified as a source of this effect. It is also demonstrated that, while the total drift area increases with the size of the wake for large vortex strengths, it is actually decreased for small circulation values. On the other hand, the Kirchhoff flow model is shown to have an unbounded total drift area. By providing a systematic account of the wake effects on the drift, the results of this study will allow for more accurate modeling of hydrodynamic stirring.
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 19
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    Anomalous magnetic configuration of Mn2NiAl ribbon and the role of hybridization in the martensitic transformation of Mn50Ni50−xAlx ribbons (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-09
    Description: The magnetic configuration of Mn 2 NiAl ribbon has been investigated. In contrast to Ni 2 MnAl, the compound Mn 2 NiAl with considerable disorder does exhibit ferromagnetism and, due to exchange interaction competition, both ferromagnetic and antiferromagnetic moment orientations can coexist between nearest neighbor Mn atoms. This is unexpected in Heusler alloys. Regarding the mechanism of the martensitic transformation in Mn 50 Ni 50− x Al x , it is found that increasing the Al content results in an unusual change in the lattice constant, a decrease of the transformation entropy change, and enhancement of the calculated electron localization. These results indicate that the p-d covalent hybridization between Mn (or Ni) and Al atoms gradually increases at the expense of the d-d hybridization between Ni and Mn atoms. This leads to an increased stability of the austenite phase and a decrease of the martensitic transformation temperature. For 11 ≤  x  ≤ 14, Mn 50 Ni 50− x Al x ferromagnetic shape memory alloys are obtained.
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  • 20
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    Continuous electrowetting at the low concentration electrolyte-insulator-semiconductor junction (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-09
    Description: Electrowetting (EW) has applications including displays, microactuation, miniaturized chemistry, adaptive optics, and energy harvesting—understanding the physics of EW junctions is of key importance. Here, the roles of semiconductor space-charge and electric double layer in continuous EW at an electrolyte-insulator-semiconductor junction are considered. A model is formulated in terms of experimental parameters—applied voltage, zero-bias wetting contact angle, semiconductor type and doping, insulator thickness and dielectric constant, and electrolyte concentration and dielectric constant. The model predicts, and experiments indicate, that the EW behavior is diminished for low concentration solutions (∼1–10 nM) and lowly doped silicon (10 14 –10 15  cm −3 ).
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  • 21
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    Effect of the helicity injection rate and the Lundquist number on spheromak sustainment (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-12
    Description: The dynamics of the magnetic relaxation process during the sustainment of spheromak configurations at different helicity injection rates is studied. The three-dimensional activity is recovered using time-dependent resistive magnetohydrodynamic simulations. A cylindrical flux conserver with concentric electrodes is used to model configurations driven by a magnetized coaxial gun. Magnetic helicity is injected by tangential boundary flows. Different regimes of sustainment are identified and characterized in terms of the safety factor profile. The spatial and temporal behavior of fluctuations is described. The dynamo action is shown to be in close agreement with existing experimental data. These results are relevant to the design and operation of helicity injected devices, as well as to basic understanding of the plasma relaxation mechanism in quasi-steady state.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
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  • 22
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    Filamentary structure of plasma produced by compression of puffing deuterium by deuterium or neon plasma sheath on plasma-focus discharge (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-12
    Description: The present experiments were performed on the PF-1000 plasma focus device at a current of 2 MA with the deuterium injected from the gas-puff placed in the axis of the anode face. The XUV frames showed, in contrast with the interferograms, the fine structure: filaments and spots up to 1 mm diameter. In the deuterium filling, the short filaments are registered mainly in the region of the internal plasmoidal structures and their number correlates with the intensity of neutron production. The longer filamentary structure was recorded close to the anode after the constriction decay. The long curve-like filaments with spots were registered in the big bubble formed after the pinch phase in the head of the umbrella shape of the plasma sheath. Filaments can indicate the filamentary structure of the current in the pinch. Together with the filaments, small compact balls a few mm in diameter were registered by both interferometry and XUV frame pictures. They emerge out of the dense column and their life-time can be greater than hundreds of ns.
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  • 23
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    Generation of energetic protons in the interaction of Gaussian laser pulses with surface modulated targets (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-12
    Description: The radiation pressure acceleration of protons in the interaction of Gaussian laser pulses and surface modulated targets is examined by multi-dimensional particle-in-cell simulations. It is shown that strong longitudinal quasi-static magnetic field is generated on the modulated surface of the target, which significantly enhances the transverse diffusion of electrons. This is beneficial for suppressing the transverse Rayleigh-Taylor instability. Finally, the surface of the accelerated proton beams becomes smoother than that in the case of the planar target, and a final mono-energetic proton beam is obtained by using the surface modulated target.
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  • 24
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    Rejuvenated bouncing of non-Newtonian droplet via nanoparticle enwrapping (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-09
    Description: We have studied the impact dynamics of non-Newtonian droplets containing poly-(ethylene oxide) (PEO) by using a high speed camera. To get a deeper insight into the droplet-substrate interaction on droplet impact behavior, both the bare droplet and the liquid marbles have been investigated. The usually observed anti-rebound phenomenon caused by the PEO additives can be rejuvenated by enwrapment of droplets with nanoparticles. The presence of PEO in bare droplets greatly enhances the contact line friction and leads to irreversible impalement of the surface structure. Whereas for liquid marbles, the nanoparticle shell on the droplet surface inhibits the impalement. Our results clearly demonstrate that it is the droplet-substrate friction rather than the bulk rheological properties of the liquid that plays the essential role in the anti-rebound effect.
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  • 25
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    Crystal structure of (±)-(4RS,5RS,7SR)-4-[(1RS,2RS,3RS,6RS)-3-benzoyloxy-2-(2-hydroxyethyl)-6-methoxymethoxy-2-methylcyclohexyl]-8,10,10-trimethyl-2-oxo-1,3-dioxaspiro[4.5]dec-8-en-7-yl benzoate benzene monosolvate (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: In the title compound, C36H44O10·C6H6, the dioxolane ring adopts an envelope conformation with the C atom bonded to the H atom as the flap, while the cyclohexene and cyclohexane rings are in half-chair and chair conformations, respectively. In the crystal, a pair of O—H...O hydrogen bonds with an R22(26) graph-set motif connect the benzoate molecules into an inversion dimer. The dimers are linked by a weak C—H...O interaction into a tape structure along [01-1]. The benzene molecule links the tapes through C—H...O and C—H...π interactions, forming a sheet parallel to (100).
    Keywords: crystal structurehydrogen bondstaxane skeletonpaclitaxel
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  • 26
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    Crystal structures of isoquinoline–3-chloro-2-nitrobenzoic acid (1/1) and isoquinolinium 4-chloro-2-nitrobenzoate (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: In each of the title isomeric compounds, C9H7.3N·C7H3.7ClNO4, (I), and C9H8N·C7H3ClNO4, (II), of isoquinoline with 3-chloro-2-nitrobenzoic acid and 4-chloro-2-nitrobenzoic acid, the two components are linked by a short hydrogen bond between a base N atom and a carboxy O atom. In the hydrogen-bonded unit of (I), the H atom is disordered over two positions with N and O site occupancies of 0.30 (3) and 0.70 (3), respectively, while in (II), an acid–base interaction involving H-atom transfer occurs and the H atom is located at the N site. In the crystal of (I), the acid–base units are connected through C—H...O hydrogen bonds into a tape structure along the b-axis direction. Inversion-related adjacent tapes are further linked through π–π interactions [centroid–centroid distances = 3.6389 (7)–3.7501 (7) Å], forming a layer parallel to (001). In the crystal of (II), the acid–base units are connected through C—H...O hydrogen bonds into a ladder structure along the a-axis direction. The ladders are further linked by another C—H...O hydrogen bond into a layer parallel to (001).
    Keywords: crystal structureshort hydrogen bondchloro- and nitro-substituted benzoic acidisoquinoline
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  • 27
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    Crystal structure of (Z)-2-[(E)-2-benzylidenehydrazin-1-ylidene]-1,2-diphenylethanone (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The title compound, C21H16N2O, has an almost planar (r.m.s. deviation = 0.0074 Å) 1,2-dibenzylidenehydrazine backbone with an approximately orthogonal almost planar (r.m.s. deviation = 0.0368 Å) phenylethanone substituent on one of the imine C atoms. The dihedral angle between the two mean planes is 76.99 (4)°. In the crystal, molecules are linked via C—H...O hydrogen bonds and C—H...π contacts, forming a three-dimensional structure with molecules stacked along the a-axis direction.
    Keywords: crystal structureSchiff baseazinesdimersC—H...π contacts
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  • 28
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    Crystal structure of 5-(4-benzyloxyphenyl)-3-(4-methoxyphenyl)-6-methylcyclohex-2-en-1-one (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The title compound, C27H26O3, crystallized with two independent molecules (A and B) in the asymmetric unit. In molecule A, the plane of the central benzene ring forms dihedral angles of 75.78 (14) and 52.75 (16)° with that of the terminal benzene rings, and the dihedral angle between the planes of the terminal benzene rings is 51.49 (17)°. The corresponding values for molecule B are 75.18 (14), 58.11 (16) and 47.91 (16)°, respectively. The cyclohexene ring adopts an envelope conformation in both molecules, with the C atom to which is attached the central benzene ring as the flap. The crystal packing, is stabilized by C—H...π interactions.
    Keywords: crystal structurecyclohexenecyclcohexen-1-one
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  • 29
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    Crystal structure of 8-[7,8-bis(4-chlorobenzoyl)-7H-cyclopenta[a]acenaphthylen-9-yl]naphthalene-1-carboxylic acid (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The title compound, C40H22Cl2O4, was formed by a Michael–Aldol domino reaction sequence, which coupled acenaphthenequinone with 4-chloroacetophenone in the presence of KOH in methanol. The dihedral angles between the central cyclopenta[a]acenaphthylene fused-ring system (r.m.s. deviation = 0.066 Å) and the 4-chlorobenzoyl rings are 62.25 (10) and 70.19 (10)°. The dihedral angle between the central ring system and the naphthoic acid grouping is 62.46 (7)°. This twisting of the pendant rings facilitates the formation of an intramolecular aromatic π–π stacking interaction between the 4-chlorobenzoyl and naphthoic acid rings, with centroid–centroid distances of 3.4533 (16) and 3.5311 (16) Å, and a C—H...π interaction between one of the H atoms of the central moiety and the 4-chlorobenzoyl ring with an H...π distance of 2.57 Å. In the crystal, carboxylic acid inversion dimers generate R22(8) loops. The dimers are linked by weak C—H...O and C—H...Cl hydrogen bonds and C—H...π interactions, generating a three-dimensional architecture.
    Keywords: crystal structuredomino reactionacenaphthenequinone4-chloroacetophenonehydrogen bonding
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  • 30
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    Crystal structure of (E)-1-(4′-methoxy-[1,1′-biphenyl]-4-yl)-3-(3-nitrophenyl)prop-2-en-1-one (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The title compound, C22H17NO4, crystallizes with two independent molecules (A and B) in the asymmetric unit. Each molecule exists as an E isomer with C—C=C—C torsion angles of −175.69 (17) and −178.41 (17)° in A and B, respectively. In molecule A, the planes of the terminal benzene rings are twisted by an angle of 26.67 (10)°, while the biphenyl unit is non-planar, the dihedral angle between the rings being 30.81 (10)°. The dihedral angle between the nitrophenyl ring and the inner phenyl ring is 6.50 (9)°. The corresponding values in molecule B are 60.61 (9), 31.07 (8) and 31.05 (9)°. In the crystal, molecules are arranged in a head-to-head manner, with the 3-nitrophenyl groups nearly parallel to one another. The A and B molecules are linked to one another via C—H...O hydrogen bonds, forming chains lying parallel to (-320) and enclosing R22(10) and R22(12) ring motifs. The methoxy group in both molecules is positionally disordered with a refined occupancy ratio of 0.979 (4):0.021 (4) for molecule A and 0.55 (4):0.45 (4) for molecule B.
    Keywords: crystal structurechalconesC—H...O hydrogen bondingmain-residue disorder
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  • 31
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    Crystal structure of dioxidobis(pentane-2,4-dionato-κ2O,O′)[1-phenyl-3-(pyridin-4-yl)propane-κN]uranium(VI) (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: In the title compound, [UO2(C5H7O2)2(C14H15N)], the uranyl(VI) unit ([O=U=O]2+) is coordinated to two acetylacetonate (acac) anions and one 1-phenyl-3-(pyridin-4-yl)propane (ppp) molecule. The geometry around the U atom is UNO6 pentagonal–bipyramidal; two uranyl(VI) O atoms are located at the axial positions, whereas four O atoms from two chelating bidentate acac ligands and one N atom of a ppp ligand form the equatorial plane.
    Keywords: crystal structurepentane-2,4-dionate1-phenyl-3-(pyridin-4-yl)propaneuranium(VI) complex
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  • 32
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    Coordination of bis(pyrazol-1-yl)amine to palladium(II): influence of the co-ligands and counter-ions on the molecular and crystal structures (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The structures of a series of complexes with general formula n[Pd(pza)X]Y·mH2O (n = 1, 2; X = Cl, Br, I, N3, NCS; Y = NO3, I, N3, [Pd(SCN)4]; m = 0, 0.5, 1) have been determined, where pza is the tridentate ligand bis[2-(3,5-dimethylpyrazol-1-yl)ethyl]amine, C14H23N5. In all complexes, {bis[2-(3,5-dimethylpyrazol-1-yl-κN2)ethyl]amine-κN}chloridopalladium nitrate, [Pd(pza)Cl]NO3, (1), {bis[2-(3,5-dimethylpyrazol-1-yl-κN2)ethyl]amine-κN}bromidopalladium nitrate, [Pd(pza)Br]NO3, (2), {bis[2-(3,5-dimethylpyrazol-1-yl-κN2)ethyl]amine-κN}iodidopalladium iodide hemihydrate, [Pd(pza)I]I·0.5H2O, (3), azido{bis[2-(3,5-dimethylpyrazol-1-yl-κN2)ethyl]amine-κN}palladium azide monohydrate, [Pd(pza)N3]N3·H2O, (4), and bis[{bis[2-(3,5-dimethylpyrazol-1-yl-κN2)ethyl]amine-κN}(thiocyanato-κN)palladium] tetrakis(thiocyanato-κS)palladate, [Pd(pza)NCS]2[Pd(SCN)4], (5), the [Pd(pza)X]+ complex cation displays a square-planar coordination geometry, and the pza ligand is twisted, approximating twofold rotation symmetry. Although the pza ligand is found with the same conformation along the series, the dihedral angle between pyrazole rings depends on the co-ligand X. This angle span the range 79.0 (3)–88.6 (1)° for the studied complexes. In (3), two complex cations, two I− anions and one water molecule of crystallization are present in the asymmetric unit. In (5), the central amine group of pza is disordered over two positions [occupancy ratio 0.770 (18):0.230 (18)]. The complex [Pd(SCN)4]2− anion of this compound exhibits inversion symmetry and shows the Pd2+ transition metal cation likewise in a square-planar coordination environment. Compound (5) is also a rare occurrence of a non-polymeric compound in which the pseudohalide ligand NCS− behaves both as thiocyanate and isothiocyanate, i.e. is coordinating either through the N atom (in the cation) or the S atom (in the anion).
    Keywords: crystal structurecoordination compoundsbis[2-(3,5-dimethylpyrazol-1-yl)ethyl]amine (pza) ligandbis(pyrazol-1-yl)aminepalladium(II)
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  • 33
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    Crystal structure of 1,3-bis(4-methylbenzyl)-1H-1,3-benzimidazol-3-ium bromide monohydrate (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: In the title hydrated symetrically substituted 1,3-bis(4-methylbenzyl)benzimidazolium salt, C23H23N2+·Br−·H2O, the dihedral angles between the benzimidazole ring system (r.m.s. deviation = 0.003 Å) and the pendant benzene rings are 73.18 (16) and 77.52 (16)°. Both benzene rings lie to the same side of the benzimidazole ring system, giving the cation an overall U-shape. In the crystal, the cation is linked to the water molecule by a short C—H...O hydrogen bond and the water molecule forms O—H...Br hydrogen bonds. Together, these interactions lead to [010] chains. The packing is consolidated by C—H...Br hydrogen bonds and aromatic π–π stacking interactions [centroid–centroid distances = 3.5401 (17) and 3.8815 (18) Å], generating a three-dimensional network.
    Keywords: crystal structure1,3-bis(4-methylbenzyl)-1H-3,1-benzimidazol-3-ium bromide monohydratebenzimidazolium saltsN-heterocyclic carbeneshydrogen bondsaromatic π–π stacking interactions
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  • 34
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    Crystal structure of 6,9-dimethyl-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazepin-8(9H)-one 0.40-hydrate (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: In the molecule of the title compound, C7H9N5O·0.40H2O, the seven-membered heterocyclic ring exhibits a boat conformation, whereas the five-membered triazole ring is almost planar (r.m.s. deviation = 0.005 Å). In the crystal, centrosymmetric dimers are linked by pairs of C—H...O hydrogen bonds into dimers, which are further connected via O—H...N and C—H...N hydrogen bonds, forming a three-dimensional network. The structure contains a partially occupied water molecule lying on a twofold axis with an occupancy factor of 0.4.
    Keywords: crystal structure1,2,4-triazepin-8(9H)-onepharmacological and biological activitieshydrogen bonding
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  • 35
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    Crystal structure of bis(η5-cyclopentadienyl)(2,3-diethylbutane-1,4-diyl)hafnium(IV) (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The title compound, [Hf(C5H5)2(C8H16)], proves a structural motif of hafnacyclopentane besides the coordination of two cyclopentadienyl ligands in an η5-fashion. The hafnacyclopentane ring has a twist conformation and is substituted by two ethyl groups in the β,β′-positions, which are trans orientated to each other. One cyclopentadienyl ring and one ethyl group are each disordered over two positions with site-occupancy ratios of 0.679 (15):0.321 (15) and 0.702 (18):0.298 (18), respectively.
    Keywords: crystal structurehafnocenefive-membered metallacycle
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  • 36
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    Crystal structure of 2-azaniumyl-3-bromo-6-oxo-5,6-dihydropyrido[1,2-a]quinoxalin-11-ium dibromide (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The title salt, C12H10BrN3O2+·2Br−, was synthesized from the reaction of N1,N4-bis(pyridin-2-ylmethylidene)benzene-1,4-diamine and bromine in a methanol solution. All non-H atoms of the 2-azaniumyl-3-bromo-6-oxo-5,6-dihydropyrido[1,2-a]quinoxalin-11-ium cation are nearly coplanar, the maximum deviation being 0.114 (4) Å. In the crystal, the cations and anions are linked through N—H...Br hydrogen bonds and weak C—H...Br interactions, forming a three-dimensional supramolecular architecture. A short Br...Br contact [3.3088 (9) Å] is observed in the crystal.
    Keywords: crystal structurebromidepyrido[1,2-a]quinoxalin-11-iumC—H...Br interactions
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  • 37
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    Crystal structure of ethyl 2-[2-((1E)-{(1E)-2-[2-(2-ethoxy-2-oxoethoxy)benzylidene]hydrazin-1-ylidene}methyl)phenoxy]acetate (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The complete molecule of the title compound, C22H24N2O6, is generated by crystallographic inversion symmetry and is approximately planar (r.m.s. deviation of the non-H atoms = 0.134 Å). The packing consists of inter-digitated sheets inclined at 25.9 (4)° to one another and linked by short C—H...O hydrogen bonds.
    Keywords: crystal structureazomethenesbis-phenoxy carboxylate
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  • 38
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    Crystal structure of 2,2-dichloro-1-(piperidin-1-yl)butane-1,3-dione (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: In the title compound, C9H13Cl2NO2, the piperidine ring shows a chair conformation and the O—C—C—O torsion angle between the carbonyl groups is 183.6 (4)°. In the crystal, molecules are linked into an infinite layer along the ab plane by a bifurcated C—H...O hydrogen bond between the carbonyl O atom adjacent to the methyl group and one of the methylene groups next to nitrogen and an additional hydrogen bond of the C—H...Cl type. These layers are connected into a three-dimensional supramolecular arrangement by O...Cl contacts [2.8979 (12) and 3.1300 (12) Å].
    Keywords: crystal structure2,2-dichloro-1-(piperidin-1-yl)butane-1,3-dionehydrogen bondingO...Cl contacts
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  • 39
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    Crystal structure of (E)-N-(3,4-dimethoxybenzylidene)morpholin-4-amine. Corrigendum (2014)
    International Union of Crystallography (IUC)
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    Publication Date: 2014-12-14
    Description: The list of authors in the paper by Çelikesir et al. [Acta Cryst. (2014), E70, o935] is corrected.
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  • 40
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    Crystal structure of (E)-4-{1-[2-(carbamothioyl)hydrazin-1-ylidene]ethyl}phenyl 4-methylbenzoate (2014)
    International Union of Crystallography (IUC)
    Details
    Publication Date: 2014-12-14
    Description: The asymmetric unit of the title compound, C17H17N3O2S, consists of two independent molecules, A and B, with different conformations: in molecule A, the dihedral angles between the central benzene ring and the pendant tolyl and carbamothioylhydrazono groups are 71.12 (9) and 5.95 (8)°, respectively. The corresponding angles in molecule B are 50.56 (12) and 26.43 (11)°, respectively. Both molecules feature an intramolecular N—H...N hydrogen bond, which closes an S(5) ring. In the crystal, molecules are linked by N—H...O, N—H...S and C—H...O hydrogen bonds, generating a three-dimensional network.
    Keywords: crystal structurethiosemicarbazones derivativesbiological activityhydrogen bondingester
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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    Crystal structure of (E)-2-[1-(benzo[d][1,3]dioxol-5-yl)ethylidene]-N-methylhydrazine-1-carbothioamide (2014)
    International Union of Crystallography (IUC)
    Details
    Publication Date: 2014-12-14
    Description: In the title compound, C11H13N3O2S, there is a short intramolecular N—H...N contact. The benzo[d][1,3]dioxole ring system is approximately planar (r.m.s. deviation = 0.025 Å) and makes a dihedral angle of 56.83 (6)° with the mean plane of the methylthiosemicarbazone fragment [–N—N—C(=S)—N—C; maximum deviation = 0.1111 (14) Å for the imino N atom]. In the crystal, molecules are linked via pairs of N—H...S hydrogen bonds, forming inversion dimers. The dimers are connected by N—H...S hydrogen bonds into layers parallel to (100). The H atoms of both methyl groups are disordered over two sets of sites and were refined with occupancy ratios of 0.5:0.5 and 0.75:0.25.
    Keywords: crystal structurethiosemiarbazone3′,4′-(methylenedioxy)acetophenone4-methylthiosemicarbazonehydrogen bondingtwo-dimensional network
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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    The H I-dominated low-surface-brightness galaxy KKR 17 (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-13
    Description: We present new narrow-band (Hα and [O  iii ]) images and optical spectrophotometry of H  ii regions for a gas-rich low-surface-brightness irregular galaxy, KKR 17. The central surface brightness of the galaxy is μ 0 ( B ) = 24.15 ± 0.03 mag s –2 . The galaxy was detected by the Arecibo Legacy Fast ALFA survey (ALFALFA). Its mass is dominated by neutral hydrogen (H  i ) gas. In contrast, both the stellar masses of the bright H  ii and diffuse stellar regions are small. In addition, the fit to the spectral energy distribution to each region shows the stellar populations of H  ii and diffuse regions are different. The bright H  ii region contains a large fraction of O-type stars, revealing recent strong star formation, whereas the diffuse region is dominated by median age stars with a typical age of ~600 Myr. Using McGaugh's abundance model, we found that the average metallicity of KKR 17 is 12 + (O/H) = 8.0 ± 0.1. The star-formation rate of KKR 17 is 0.21 ± 0.04 M  yr –1 , which is ~1/5 of our Milky Way's. Based on the analysis results for young stellar clusters in the H  ii region, the bright H  ii region has two sub-components with different velocities and metallicities. This may be caused by the outflow of massive stars or merging events. However, the mechanism triggering star formation in the H  ii region is still uncertain.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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    A multiwavelength study of the M dwarf binary YY Geminorum (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-13
    Description: We review the results of the 1988 multiwavelength campaign on the late-type eclipsing binary YY Geminorum. Observations include: broad-band optical and near-infrared photometry, simultaneous optical and ultraviolet ( IUE ) spectroscopy, X-ray ( Ginga ) and radio (VLA) data. From models fitted to the optical light curves, fundamental physical parameters have been determined together with evidence for transient maculations (spots) located near quadrature longitudes and intermediate latitudes. Eclipses were observed at optical, ultraviolet and radio wavelengths. Significant drops in 6 cm radio emission near the phases of both primary and secondary eclipse indicate relatively compact radio emitting volumes that may lie between the binary components. IUE observations during secondary eclipse are indicative of a uniform chromosphere saturated with Mg  ii emission and an extended volume of Lyα emission. Profile fitting of high-dispersion Hα spectra confirms the chromospheric saturation and indicates significant Hα opacity to heights of a few per cent of the photospheric radius. There is evidence for an enhanced Hα emission region visible near phase 0.25–0.35 which may be associated with a large spot on the primary and with two small optical flares which were also observed at other wavelengths: one in microwave radiation and the other in X-rays. For both flares, L X / L opt is consistent with energy release in closed magnetic structures.
    Print ISSN: 0035-8711
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    Topics: Physics
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    Effects of heating power on divertor in-out asymmetry and scrape-off layer flow in reversed field on Experimental Advanced Superconducting Tokamak (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-13
    Description: The dependence of divertor asymmetry and scrape-off layer (SOL) flow on heating power has been investigated in the Experimental Advanced Superconducting Tokamak (EAST). Divertor plasma exhibits an outboard-enhanced in-out asymmetry in heat flux in lower single null configuration for in reversed (ion ∇ B drift direction toward the upper X-point) field directions. Upper single null exhibits an inboard-favored asymmetry in low heating power condition, while exhibits an outboard-favored asymmetry when increasing the heating power. Double null has the strongest in-out asymmetry in heat flux, favoring the outer divertor. The in-out asymmetry ratios of q t , out / q t , in and P out / P total increase with the power across the separatrix P loss , which is probably induced by the enhanced radial particle transport due to a large pressure gradient. The characteristics of the measured SOL parallel flow under various discharge conditions are consistent with the Pfirsch-Schlüter (PS) flow with the parallel Mach number M ∥ decreasing with the line averaged density but increasing with P loss , in the same direction as the PS flow. The contributions of both poloidal E × B drift and parallel flow on poloidal particle transport in SOL on EAST are also assessed.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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    Effects of magnetic islands on drift wave instability (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-13
    Description: Magnetic islands have been implemented in the gyrokinetic toroidal code to study the effects of the islands on microturbulence. The pressure profile flattening is verified in the simulation with the islands. Simulations of ion temperature gradient instability find that different toroidal modes are linearly coupled together and that toroidal spectra become broader when the island width increases. The real frequencies and growth rates of different toroidal modes approach each other with the averaged value independent of the island width. The linear mode structures are enhanced at the island separatrices and weakened at the island centers, consistent with the flattening of the pressure profile inside the islands.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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    Slow motion of a circular cylinder in a plane Poiseuille flow in a microchannel (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-13
    Description: The slow motion of a circular cylinder in a plane Poiseuille flow in a microchannel is analyzed for a wide range of cylinder radii and positions across the channel. The cylinder translates parallel to the channel walls and rotates about its axis. The Stokes approximation is used and the problem is solved analytically using the Papkovich-Fadle eigenfunction expansion and the least-squares method. The stream function and the pressure distribution of the flow field are obtained as results. The force and moment exerted on the cylinder, and the pressure change far from the cylinder, are calculated and shown as functions of the size and location of the cylinder. The results confirm some reciprocal relations exactly. In particular, the translational and rotational velocities of the drifting cylinder in the existing Poiseuille flow are determined. The induced pressure change, when the cylinder drifts in the Poiseuille flow, is also calculated. Some typical streamline patterns, depending on the size and location of the cylinder, are shown and discussed. When the cylinder translates and/or rotates in the channel blocked at infinity, a series of Moffatt eddies appears far from the cylinder in the channel, as expected.
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
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    Elastocapillary flows in flexible tubes (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-13
    Description: Interactions between capillary and elastic effects are relevant to a variety of applications from micro- and nano-scale manufacturing to biological systems. In this work, we investigate capillary flows in flexible, millimeter-scale cylindrical elastic tubes. We demonstrate that surface tension can cause sufficiently flexible tubes to collapse and coalesce spontaneously through non-axisymmetric buckling, and develop criteria for the initial deformation and complete collapse of a circular tube. Experimental results for capillary rise and evaporation of a liquid in a flexible tube are presented, and several regimes are seen for the equilibrium state of a flexible tube deforming under capillary pressure. Deformations of the tube walls are measured in different regimes and compared with a shell theory model. Analysis and experimental results show that despite the complex and non-axisymmetric deformed shapes of cylindrical structures, the elastocapillary length used in previous literature for flat plates and sheets can be used to predict the behavior of flexible tubes.
    Print ISSN: 1070-6631
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    Oblique ion-acoustic cnoidal waves in two temperature superthermal electrons magnetized plasma (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-13
    Description: A study is presented for the oblique propagation of ion acoustic cnoidal waves in a magnetized plasma consisting of cold ions and two temperature superthermal electrons modelled by kappa-type distributions. Using the reductive perturbation method, the nonlinear Korteweg de-Vries equation is derived, which further gives the solutions with a special type of cnoidal elliptical functions. Both compressive and rarefactive structures are found for these cnoidal waves. Nonlinear periodic cnoidal waves are explained in terms of plasma parameters depicting the Sagdeev potential and the phase curves. It is found that the density ratio of hot electrons to ions μ significantly modifies compressive/refractive wave structures. Furthermore, the combined effects of superthermality of cold and hot electrons κ c , κ h , cold to hot electron temperature ratio σ , angle of propagation and ion cyclotron frequency ω ci have been studied in detail to analyze the height and width of compressive/refractive cnoidal waves. The findings in the present study could have important implications in understanding the physics of electrostatic wave structures in the Saturn's magnetosphere where two temperature superthermal electrons are present.
    Print ISSN: 1070-664X
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    Smart monitoring system based on adaptive current control for superconducting cable test (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-13
    Description: A smart monitoring system for superconducting cable test is proposed with an adaptive current control of a superconducting transformer secondary. The design, based on Fuzzy Gain Scheduling, allows the controller parameters to adapt continuously, and finely, to the working variations arising from transformer nonlinear dynamics. The control system is integrated in a fully digital control loop, with all the related benefits, i.e., high noise rejection, ease of implementation/modification, and so on. In particular, an accurate model of the system, controlled by a Fuzzy Gain Scheduler of the superconducting transformer, was achieved by an experimental campaign through the working domain at several current ramp rates. The model performance was characterized by simulation, under all the main operating conditions, in order to guide the controller design. Finally, the proposed monitoring system was experimentally validated at European Organization for Nuclear Research (CERN) in comparison to the state-of-the-art control system [P. Arpaia, L. Bottura, G. Montenero, and S. Le Naour, “Performance improvement of a measurement station for superconducting cable test,” Rev. Sci. Instrum.83, 095111 (2012)] of the Facility for the Research on Superconducting Cables, achieving a significant performance improvement: a reduction in the system overshoot by 50%, with a related attenuation of the corresponding dynamic residual error (both absolute and RMS) up to 52%.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    Characterization of solid state nuclear track detectors of the polyallyl-diglycol-carbonate (CR-39/PM-355) type for light charged particle spectroscopy (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-13
    Description: This paper presents a method which uses the characteristics of the etch pits induced in a polyallyl-diglycol-carbonate (PADC) detector of the CR-39/PM-355 type to estimate particle energy. This method is based on the data provided by a semiautomatic system that selects tracks according to two parameters, crater diameters, and mean gray level values. In this paper we used the results of the calibration measurements that were obtained in our laboratory in the period 2000–2014. Combining the information on the two parameters it is possible to determine unambiguously the incident projectile energy values. The paper presents the results of an attempt to estimate the energy resolution of the method when analyzing the tracks produced in the CR-39/PM-355 detector by energetic ions such as alpha particles, protons, and deuterons. We discuss the energy resolution of the measurement of light charged particle energy which is based on the parameters (crater diameter and mean gray level value) of tracks induced in solid state nuclear track detectors of the PADC type.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    Automated electrostatic probe device of high resolution and accuracy (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-13
    Description: In this work, an automated apparatus for driving single electrostatic probes and acquiring the plasma-related data has been designed and fabricated. The voltage range of the present system is ±110 V with an adjustable voltage step as low as 3 mV. Voltage and current measurements are carried out with high resolution and high accuracy circuits, both based on 16 bit analog-to-digital converters. The code embedded in a micro-controller, schedules the operation of the device and transfers the experimental data to a personal computer. The modular design of the system makes possible its modification and thus increases its adaptability to different plasma setups. Finally, the reliable operation of the entire device is confirmed by tests in Electron Cyclotron Resonance plasma.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    How Do Metal Ion Levels Change over Time in Hip Resurfacing Patients? A Cohort Study (2014)
    Hindawi
    Details
    Publication Date: 2014-12-15
    Description: Metal-on-metal hip resurfacing (MOM-HR) is offered as an alternative to traditional hip arthroplasty for young, active adults with advanced osteoarthritis. Nevertheless, concerns remain regarding wear and corrosion of the bearing surfaces and the resulting increase in metal ion levels. We evaluated three cohorts of patients with Birmingham hip resurfacing (BHR) at an average follow-up of 2, 5, and 9 years. We asked whether there would be differences in ion levels between the cohorts and inside the gender. Nineteen patients were prospectively analyzed. The correlation with clinical-radiographic data was also performed. Chromium, cobalt, nickel, and molybdenum concentrations were measured by atomic absorption spectrophotometry. Chromium and cobalt levels demonstrated a tendency to decrease over time. Such tendency was present only in females. An inverse correlation between chromium, implant size, and Harris hip score was present at short term; it disappeared over time together with the decreased ion levels. The prospective analysis showed that, although metal ion levels remained fairly constant within each patient, there was a relatively large variation between subjects, so mean data in this scenario must be interpreted with caution. The chronic high exposure should be carefully considered during implant selection, particularly in young subjects, and a stricter monitoring is mandatory.
    Electronic ISSN: 1537-744X
    Topics: Natural Sciences in General
    Published by Hindawi
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    Adsorption of Polyanion onto Large Alpha Alumina Beads with Variably Charged Surface (2014)
    Hindawi
    Details
    Publication Date: 2014-12-16
    Description: Adsorption of strong polyelectrolyte, poly(styrenesulfonate), PSS, of different molecular weights onto large α-Al2O3 beads was systematically investigated as functions of pH and NaCl concentrations. The ultraviolet (UV) absorption spectra of PSS at different pH and salt concentrations confirmed that the structure of PSS is independent of pH. With the change of molecular weight from 70 kg/mol (PSS 70) to 1000 kg/mol (PSS 1000), adsorption amount of PSS increases and proton coadsorption on the surface of α-Al2O3 decreases at given pH and salt concentration. It suggests that higher molecular weight of PSS was less flat conformation than lower one. The adsorption density of PSS 70 and PSS 1000 decreases with decreasing salt concentrations, indicating that both electrostatic and nonelectrostatic interactions are involved. Experimental results of both PSS 70 and PSS 1000 adsorption isotherms onto α-Al2O3 at different pH and salt concentrations can be represented well by two-step adsorption model. The effects of molecular weight and salt concentration are explained by structure of adsorbed PSS onto α-Al2O3. The influence of added SDS on the isotherms is evaluated from the sequential adsorption. The SDS uptake onto α-Al2O3 in the presence of hemimicelles can prevent the adsorption of PSS at low concentration so that adsorption of PSS reduces with preadsorbed SDS.
    Print ISSN: 1687-7985
    Electronic ISSN: 1687-7993
    Topics: Chemistry and Pharmacology , Physics
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    Goos-Hänchen effect and bending of spin wave beams in thin magnetic films (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-16
    Description: For magnon spintronic applications, the detailed knowledge of spin wave (SW) beam dispersion, transmission (reflection) of SWs passing through (reflected from) interfaces, or borders or the scattering of SWs by inhomogeneities is crucial. These wave properties are decisive factors on the usefulness of a particular device. Here, we demonstrate, using micromagnetic simulations supported by an analytical model, that the Goos-Hänchen (GH) shift exists for SW reflecting from thin film edge and that with the effect becomes observable. We show that this effect will exist for a broad range of frequencies in the dipole-exchange range, with the magnetization degree of pinning at the film edge as the crucial parameter, whatever its nature. Moreover, we have also found that the GH effect can be accompanied or even dominating by a bending of the SW beam due to the inhomogeneity of the internal magnetic field. This inhomogeneity, created by demagnetizing field taking place at the film edge, causes gradual change of SWs refractive index. The refraction of the SW beams by the non-uniformity of the magnetic field enables the exploration of graded index magnonics and metamaterial properties for the transmission and processing of information at nanoscale.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
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    Heat-driven spin transport in a ferromagnetic metal (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: As a non-magnetic heavy metal is attached to a ferromagnet, a vertically flowing heat-driven spin current is converted to a transverse electric voltage, which is known as the longitudinal spin Seebeck effect (SSE). If the ferromagnet is a metal, this voltage is also accompanied by voltages from two other sources, i.e., the anomalous Nernst effect in both the ferromagnet and the proximity-induced ferromagnetic boundary layer. By properly identifying and carefully separating those different effects, we find that in this pure spin current circuit the additional spin current drawn by the heavy metal generates another significant voltage by the ferromagnetic metal itself which should be present in all relevant experiments.
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    Confocal shift interferometry of coherent emission from trapped dipolar excitons (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We introduce a confocal shift-interferometer based on optical fibers. The presented spectroscopy allows measuring coherence maps of luminescent samples with a high spatial resolution even at cryogenic temperatures. We apply the spectroscopy onto electrostatically trapped, dipolar excitons in a semiconductor double quantum well. We find that the measured spatial coherence length of the excitonic emission coincides with the point spread function of the confocal setup. The results are consistent with a temporal coherence of the excitonic emission down to temperatures of 250 mK.
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    Enhanced hydrogen evolution rates at high pH with a colloidal cadmium sulphide–platinum hybrid system (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We demonstrate enhanced hydrogen generation rates at high pH using colloidal cadmium sulphide nanorods decorated with Pt nanoparticles. We introduce a simplified procedure for the decoration and subsequent hydrogen generation, reducing both the number of working steps and the materials costs. Different Pt precursor concentrations were tested to reveal the optimal conditions for the efficient hydrogen evolution. A sharp increase in hydrogen evolution rates was measured at pH 13 and above, a condition at which the surface charge transfer was efficiently mediated by the formation of hydroxyl radicals and further consumption by the sacrificial triethanolamine hole scavenger.
    Electronic ISSN: 2166-532X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    Enhancement of the electrical characteristics of metal-free phthalocyanine films using cold isostatic pressing (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: Spatial gaps between grains and other grains, substrates, or electrodes in organic electronic devices are one of the causes of the reduction in the electrical characteristics. In this study, we demonstrate that cold isostatic pressing (CIP) is an effective method to crush the gaps and enhance the electrical characteristics. CIP of metal-free phthalocyanine (H 2 PC) films induced a decrease in the film thickness by 34%–40% because of the gap crush. The connection of smaller grains into a larger grain and planarization of the film surface were also observed in the CIP film. The crystal axes of the H 2 PC crystallites were rearranged from the a-axis to the c-axis of the α-phase crystal structure in a direction perpendicular to the substrate by CIP, indicating favorable hole injection and transport in this direction because of a better overlap of π orbitals. Thermally stimulated current measurements showed that deep hole traps disappeared and the total hole-trap density decreased after CIP. These CIP-induced changes of the film thicknesses, crystal axes and the hole traps lead to a marked increase in the hole mobility of the H 2 PC films from 2.0 × 10 −7 to 4.0 × 10 −4 cm 2 /V s by 2000 times in the perpendicular direction. We believe that these findings are important for unveiling the underlying carrier injection and transport mechanisms of organic films and for enhancing the performance of future organic electronic devices.
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    Quantized spin waves in single Co/Pt dots detected by anomalous Hall effect based ferromagnetic resonance (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: Anomalous Hall effect (AHE) based ferromagnetic resonance (FMR) measurements were carried out on perpendicularly magnetized Co/Pt multilayer single dots of 0.4–3  μ m in diameter. The resonance behavior was measured by detecting the decrease of perpendicular magnetization component due to magnetization precession. Resonance behavior was observed as a clear decrease of Hall voltages, and the obtained resonance fields were consistent with the results of vector-network-analyzer FMR. Spin-waves with cylindrical symmetry became significant by decreasing the dot diameter, and quantized multiple resonances were observed in the dot of 0.4 μm in diameter. The AHE based FMR proposed here is a powerful method to approach magnetization dynamics including spin waves and non-linear behavior excited in a finite nanostructure.
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    An efficient radiative cooling approximation for use in hydrodynamic simulations (2014)
    Oxford University Press
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    Publication Date: 2014-12-14
    Description: To make relevant predictions about observable emission, hydrodynamical simulation codes must employ schemes that account for radiative losses, but the large dimensionality of accurate radiative transfer schemes is often prohibitive. Stamatellos and collaborators introduced a scheme for smoothed particle hydrodynamics (SPH) simulations based on the notion of polytropic pseudo-clouds that uses only local quantities to estimate cooling rates. The computational approach is extremely efficient and works well in cases close to spherical symmetry, such as in star formation problems. Unfortunately, the method, which takes the local gravitational potential as an input, can be inaccurate when applied to non-spherical configurations, limiting its usefulness when studying discs or stellar collisions, among other situations of interest. Here, we introduce the ‘pressure scale height method,’ which incorporates the fluid pressure scaleheight into the determination of column densities and cooling rates, and show that it produces more accurate results across a wide range of physical scenarios while retaining the computational efficiency of the original method. The tested models include spherical polytropes as well as discs with specified density and temperature profiles. We focus on applying our techniques within an SPH code, although our method can be implemented within any particle-based Lagrangian or grid-based Eulerian hydrodynamic scheme. Our new method may be applied in a broad range of situations, including within the realm of stellar interactions, collisions, and mergers.
    Print ISSN: 0035-8711
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    Time dependent potentials associated with exceptional orthogonal polynomials (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We introduce a method for generating rational extensions of time-dependent potentials, such that the associated Schrödinger equation admits solutions in terms of exceptional orthogonal polynomials. Our method is applicable to position-dependent Schrödinger equations, as well as to their conventional counterparts for constant mass.
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
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    Existence of the Stark-Wannier quantum resonances (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: In this paper, we prove the existence of the Stark-Wannier quantum resonances for one-dimensional Schrödinger operators with smooth periodic potential and small external homogeneous electric field. Such a result extends the existence result previously obtained in the case of periodic potentials with a finite number of open gaps.
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
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    Citrate synthase proteins in extremophilic organisms: Studies within a structure-based model (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-16
    Description: We study four citrate synthase homodimeric proteins within a structure-based coarse-grained model. Two of these proteins come from thermophilic bacteria, one from a cryophilic bacterium and one from a mesophilic organism; three are in the closed and two in the open conformations. Even though the proteins belong to the same fold, the model distinguishes the properties of these proteins in a way which is consistent with experiments. For instance, the thermophilic proteins are more stable thermodynamically than their mesophilic and cryophilic homologues, which we observe both in the magnitude of thermal fluctuations near the native state and in the kinetics of thermal unfolding. The level of stability correlates with the average coordination number for amino acid contacts and with the degree of structural compactness. The pattern of positional fluctuations along the sequence in the closed conformation is different than in the open conformation, including within the active site. The modes of correlated and anticorrelated movements of pairs of amino acids forming the active site are very different in the open and closed conformations. Taken together, our results show that the precise location of amino acid contacts in the native structure appears to be a critical element in explaining the similarities and differences in the thermodynamic properties, local flexibility, and collective motions of the different forms of the enzyme.
    Electronic ISSN: 1931-9223
    Topics: Chemistry and Pharmacology , Physics
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    How to efficiently select an arbitrary Clifford group element (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We give an algorithm which produces a unique element of the Clifford group on n qubits ( C n ) from an integer 0 ≤ i 〈 C n (the number of elements in the group). The algorithm involves O ( n 3 ) operations and provides, in addition to a canonical mapping from the integers to group elements g , a factorization of g into a sequence of at most 4 n symplectic transvections. The algorithm can be used to efficiently select random elements of C n which are often useful in quantum information theory and quantum computation. We also give an algorithm for the inverse map, indexing a group element in time O ( n 3 ).
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
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    Erratum: “Symmetry principles in quantum systems theory” [J. Math. Phys. 52, 113510 (2011)] (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
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    Experimental study of global-scale turbulence in a librating ellipsoid (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We present laboratory experimental results demonstrating that librational forcing of an ellipsoidal container of water can produce intense motions through the mechanism of a libration driven elliptical instability (LDEI). These libration studies are conducted using an ellipsoidal acrylic container filled with water. A particle image velocimetry method is used to measure the 2D velocity field in the equatorial plane over hundreds libration cycles for a fixed Ekman number, E = 2 × 10 −5 . In doing so, we recover the libration induced base flow and a time averaged zonal flow. Further, we show that LDEI in non-axisymmetric container geometries is capable of driving both intermittent and saturated turbulent motions in the bulk fluid. Additionally, we measure the growth rate and amplitude of the LDEI induced excited flow in a fully ellipsoidal container at more extreme parameters than previously studied [Noir et al. , “Experimental study of libration-driven flows in nonaxisymmetric containers,” Phys. Earth Planet. Inter. 204-205 , 1 (2012); Cébron et al. , Phys. Fluids 24 , 061703, “Libration driven elliptical instability,” (2012)]. Excitation of bulk filling turbulence by librational forcing provides a mechanism for transferring rotational energy into turbulent fluid motion and thus can play an important role in the thermal evolution, interior dynamics, and magneto-hydrodynamics of librating bodies, as appear to be common in solar system settings [e.g., Comstock and Bills, “A solar system survey of forced librations in longitude,” J. Geophys. Res. Planets 108 , 1 (2003)].
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
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    Miscible heavy-light displacement flows in an inclined two-dimensional channel: A numerical approach (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We numerically study the displacement flow of two iso-viscous Newtonian fluids in an inclined two-dimensional channel, formed by two parallel plates. The results are complementary to our previous studies on displacement flows in pipes and channels. The heavier displacing fluid moves the lighter displaced fluid in the downward direction. Three dimensionless groups largely describe these flows: the densimetric Froude number ( Fr ), the Reynolds number ( Re ), and the duct inclination (β). As a first order approximation, we are able to classify different flow regimes phenomenologically in a two-dimensional ( Fr ; Re cosβ/ Fr )-plane and provide leading order expressions for the transitions between different regimes. The stabilizing and/or de-stabilizing effects of the imposed mean flow on buoyant exchange flows (zero imposed velocity) are described for a broad range of dimensionless parameters.
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
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    Symmetric model of compressible granular mixtures with permeable interfaces (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: Compressible granular materials are involved in many applications, some of them being related to energetic porous media. Gas permeation effects are important during their compaction stage, as well as their eventual chemical decomposition. Also, many situations involve porous media separated from pure fluids through two-phase interfaces. It is thus important to develop theoretical and numerical formulations to deal with granular materials in the presence of both two-phase interfaces and gas permeation effects. Similar topic was addressed for fluid mixtures and interfaces with the Discrete Equations Method (DEM) [R. Abgrall and R. Saurel, “Discrete equations for physical and numerical compressible multiphase mixtures,” J. Comput. Phys. 186 (2), 361-396 (2003)] but it seemed impossible to extend this approach to granular media as intergranular stress [K. K. Kuo, V. Yang, and B. B. Moore, “Intragranular stress, particle-wall friction and speed of sound in granular propellant beds,” J. Ballist. 4 (1), 697-730 (1980)] and associated configuration energy [J. B. Bdzil, R. Menikoff, S. F. Son, A. K. Kapila, and D. S. Stewart, “Two-phase modeling of deflagration-to-detonation transition in granular materials: A critical examination of modeling issues,” Phys. Fluids 11 , 378 (1999)] were present with significant effects. An approach to deal with fluid-porous media interfaces was derived in Saurel et al. [“Modelling dynamic and irreversible powder compaction,” J. Fluid Mech. 664 , 348-396 (2010)] but its validity was restricted to weak velocity disequilibrium only. Thanks to a deeper analysis, the DEM is successfully extended to granular media modelling in the present paper. It results in an enhanced version of the Baer and Nunziato [“A two-phase mixture theory for the deflagration-to-detonation transition (DDT) in reactive granular materials,” Int. J. Multiphase Flow 12 (6), 861-889 (1986)] model as symmetry of the formulation is now preserved. Several computational examples are shown to validate and illustrate method’s capabilities.
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
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    Finite amplitude electroconvection induced by strong unipolar injection between two coaxial cylinders (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We perform a theoretical and numerical study of the Coulomb-driven electroconvection flow of a dielectric liquid between two coaxial cylinders. The specific case, where the inner to outer diameter ratio is 0.5, is analyzed. A strong unipolar injection of ions either from the inner or outer cylinder is considered to introduce free charge carriers into the system. A finite volume method is used to solve all governing equations including Navier-Stokes equations and a simplified set of Maxwell’s equations. The flow is characterized by a subcritical bifurcation in the finite amplitude regime. A linear stability criterion and a nonlinear one that correspond to the onset and stop of the flow motion, respectively, are linked with a hysteresis loop. In addition, we also explore the behavior of the system for higher values of the stability parameter. For inner injection, we observe a transition between the patterns made of 7 and 8 cells, before an oscillatory regime is attained. Such a transition leads to a second finite amplitude stability criterion. A simple modal analysis reveals that the competition of different modes is at the origin of this behavior. The charge density, as well as velocity field distributions is provided to help understand the bifurcation behavior.
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
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    Generation of metal ions in the beam plasma produced by a forevacuum-pressure electron beam source (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We report on the production of metal ions of magnesium and zinc in the beam plasma formed by a forevacuum-pressure electron source. Magnesium and zinc vapor were generated by electron beam evaporation from a crucible and subsequently ionized by electron impact from the e-beam itself. Both gaseous and metallic plasmas were separately produced and characterized using a modified RGA-100 quadrupole mass-spectrometer. The fractional composition of metal isotopes in the plasma corresponds to their fractional natural abundance.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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    Massive Conformal Gravity (2014)
    Hindawi
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    Publication Date: 2014-12-15
    Description: We construct a massive theory of gravity that is invariant under conformal transformations. The massive action of the theory depends on the metric tensor and a scalar field, which are considered the only field variables. We find the vacuum field equations of the theory and analyze its weak-field approximation and Newtonian limit.
    Print ISSN: 1687-7357
    Electronic ISSN: 1687-7365
    Topics: Physics
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    The role of residual charges in the repeatability of the dynamics of atmospheric pressure room temperature plasma plume (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: To better understand the role of residual electrons in the repeatability of an atmospheric pressure plasma plume, the characteristics of a helium plasma jet from the 1st, 2nd,… until the repeatable discharge pulse are investigated for the first time. It's found that the longest plasma plume is achieved in the 1st discharge pulse. The length of the plasma plume becomes shorter and shorter and reaches a constant value in the 3rd discharge pulse and keeps the same for the following pulses. The dynamics of the 1st discharge pulse show that the plasma bullet appears random in nature. Two photomultiplier tubes are used to distinguish the two potential factors that could result in the stochastic dynamics of the plasma bullet, i.e., stochastic ignition of the plasma and the stochastic propagation velocity. The results show that the stochastic propagation velocity occurs only in the 1st and the 2nd discharge pulses, while the stochastic ignition of the plasma presents until the 100th pulse. The dynamics of the plasma propagation become repeatable after about 100 pulses. Detail analysis shows that the repeatability of plasma bullet is due to the residual electrons density. The residual electron density of 10 9  cm −3 or higher is needed for repeatable discharges mode.
    Print ISSN: 1070-664X
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    Topics: Physics
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    Two-fluid turbulence including electron inertia (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: We present a full two-fluid magnetohydrodynamic (MHD) description for a completely ionized hydrogen plasma, retaining the effects of the Hall current, electron pressure, and electron inertia. According to this description, each plasma species introduces a new spatial scale: the ion inertial length λ i and the electron inertial length λ e , which are not present in the traditional MHD description. In the present paper, we seek for possible changes in the energy power spectrum in fully developed turbulent regimes, using numerical simulations of the two-fluid equations in two-and-a-half dimensions. We have been able to reproduce different scaling laws in different spectral ranges, as it has been observed in the solar wind for the magnetic energy spectrum. At the smallest wavenumbers where plain MHD is valid, we obtain an inertial range following a Kolmogorov k −5∕3 law. For intermediate wavenumbers such that λ i − 1 ≪ k ≪ λ e − 1 , the spectrum is modified to a k −7∕3 power-law, as has also been obtained for Hall-MHD neglecting electron inertia terms. When electron inertia is retained, a new spectral region given by k 〉 λ e − 1 arises. The power spectrum for magnetic energy in this region is given by a k −11∕3 power law. Finally, when the terms of electron inertia are retained, we study the self-consistent electric field. Our results are discussed and compared with those obtained in the solar wind observations and previous simulations.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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    Collisionless electron heating in periodic arrays of inductively coupled plasmas (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: A novel mechanism of collisionless heating in large planar arrays of small inductive coils operated at radio frequencies is presented. In contrast to the well-known case of non-local heating related to the transversal conductivity, when the electrons move perpendicular to the planar coil, we investigate the problem of electrons moving in a plane parallel to the coils. Two types of periodic structures are studied. Resonance velocities where heating is efficient are calculated analytically by solving the Vlasov equation. Certain scaling parameters are identified. The concept is further investigated by a single particle simulation based on the ergodic principle and combined with a Monte Carlo code allowing for collisions with Argon atoms. Resonances, energy exchange, and distribution functions are obtained. The analytical results are confirmed by the numerical simulation. Pressure and electric field dependences are studied. Stochastic heating is found to be most efficient when the electron mean free path exceeds the size of a single coil cell. Then the mean energy increases approximately exponentially with the electric field amplitude.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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    Critical Blow-Up and Global Existence for Discrete Nonlinear p-Laplacian Parabolic Equations (2014)
    Hindawi
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    Publication Date: 2014-12-15
    Description: The goal of this paper is to investigate the blow-up and the global existence of the solutions to the discrete p-Laplacian parabolic equation , , , , , depending on the parameters and . Besides, we provide several types of the comparison principles to this equation, which play a key role in the proof of the main theorems. In addition, we finally give some numerical examples which exploit the main results.
    Print ISSN: 1026-0226
    Electronic ISSN: 1607-887X
    Topics: Mathematics
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    A Complex Dynamical Analysis of the Indian Stock Market (2014)
    Hindawi
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    Publication Date: 2014-12-15
    Description: This paper seeks to analyze the dynamical structure of the Indian stock market by considering two major Indian stock market indices, namely, BSE Sensex and CNX Nifty. The recurrence quantification analysis (RQA) is applied on the daily closing data of the two series during the period from January 2, 2002, to October 10, 2013. A Rolling Window of 100 and step size 21 are applied in order to see how both the series behave over time. The analysis based on three RQA measures, namely, % determinism (DET), laminarity (LAM), and trapping time (TT), provides conclusive evidence that the Indian equity market is chaotic in nature. Evidences for phase transition in the Indian equity market around the time of financial crisis are also found.
    Print ISSN: 2090-2123
    Electronic ISSN: 2090-2131
    Topics: Economics
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    Digitized detection of gamma-ray signals concentrated in narrow time windows for transient positron annihilation lifetime spectroscopy (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-16
    Description: A pulsed slow-positron beam generated by an electron linear accelerator was directly used for positron annihilation lifetime spectroscopy without any positron storage devices. A waveform digitizer was introduced to simultaneously capture multiple gamma-ray signals originating from positron annihilation events during a single accelerator pulse. The positron pulse was chopped and bunched with the chopper signals also sent to the waveform digitizer. Time differences between the annihilation gamma-ray and chopper peaks were calculated and accumulated as lifetime spectra in a computer. The developed technique indicated that positron annihilation lifetime spectroscopy can be performed in a 20 μ s time window at a pulse repetition rate synchronous with the linear accelerator. Lifetime spectra of a Kapton sheet and a thermally grown SiO 2 layer on Si were successfully measured. Synchronization of positron lifetime measurements with pulsed ion irradiation was demonstrated by this technique.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    Magnetic resonance tomography using elongated transmitter and in-loop receiver arrays for time-efficient 2-D imaging of subsurface aquifer structures (2014)
    Oxford University Press
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    Publication Date: 2014-12-17
    Description: Surface nuclear magnetic resonance (surface-NMR) is a promising technique for exploring shallow subsurface aquifer structures. Surface-NMR can be applied in environments that are characterized as a 1-D layered Earth. The technique utilizes a single loop and is referred to as magnetic resonance sounding. The technique referred to as magnetic resonance tomography (MRT) allows complex 2-D aquifer structures to be explored. Currently, MRT requires multiple loops and a roll along measurement scheme, which causes long survey time. We propose a loop layout using an elongated transmitter and an in-loop receiver arrays (ETRA) to conduct a 2-D survey with just one measurement. We present a comprehensive comparison between the new layout and the common approaches based on sensitivity and resolution analyses and show synthetic and field data. The results show that ETRA generates subsurface images at sufficient resolution with significantly lower survey times than other loop layouts.
    Keywords: Geomagnetism, Rock Magnetism and Palaeomagnetism
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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    Integrated velocity field from ground and satellite geodetic techniques: application to Arenal volcano (2014)
    Oxford University Press
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    Publication Date: 2014-12-17
    Description: Measurements of ground deformation can be used to identify and interpret geophysical processes occurring at volcanoes. Most studies rely on a single geodetic technique, or fit a geophysical model to the results of multiple geodetic techniques. Here we present a methodology that combines GPS, Total Station measurements and InSAR into a single reference frame to produce an integrated 3-D geodetic velocity surface without any prior geophysical assumptions. The methodology consists of five steps: design of the network, acquisition and processing of the data, spatial integration of the measurements, time series computation and finally the integration of spatial and temporal measurements. The most significant improvements of this method are (1) the reduction of the required field time, (2) the unambiguous detection of outliers, (3) an increased measurement accuracy and (4) the construction of a 3-D geodetic velocity field. We apply this methodology to ongoing motion on Arenal's western flank. Integration of multiple measurement techniques at Arenal volcano revealed a deformation field that is more complex than that described by individual geodetic techniques, yet remains consistent with previous studies. This approach can be applied to volcano monitoring worldwide and has the potential to be extended to incorporate other geodetic techniques and to study transient deformation.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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    Review of Polymer, Dye-Sensitized, and Hybrid Solar Cells (2014)
    Hindawi
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    Publication Date: 2014-12-15
    Description: The combination of inorganic nanoparticles semiconductor, conjugated polymer, and dye-sensitized in a layer of solar cell is now recognized as potential application in developing flexible, large area, and low cost photovoltaic devices. Several conjugated low bandgap polymers, dyes, and underlayer materials based on the previous studies are quoted in this paper, which can provide guidelines in designing low cost photovoltaic solar cells. All of these materials are designed to help harvest more sunlight in a wider range of the solar spectrum besides enhancing the rate of charge transfer in a device structure. This review focuses on developing solid-state dye-synthesized, polymer, and hybrid solar cells.
    Print ISSN: 1110-662X
    Electronic ISSN: 1687-529X
    Topics: Electrical Engineering, Measurement and Control Technology , Energy, Environment Protection, Nuclear Power Engineering
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    A Middleware for the Integration of Smart Grid Elements with WSN Based Solutions (2014)
    Hindawi
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    Publication Date: 2014-12-17
    Description: Currently, electricity distributors make use of various types of equipment divided into levels of automation. This automation enables the integration of elements such as Intelligent Electronic Devices (IEDs) to the supervision of the distribution electrical system, but there is not an appropriate environment to increase the scale of these elements. In this context, the smart grid comes with specifications that allow adding new elements to the intelligence of the power grid operation. However, the cost of communication is still an impediment to the scalability of the integration of these elements into the current structure. In this paper, we propose a middleware that optimizes the communication of this integration using wireless sensor networks (WSN). The goal is to ensure a gradual integration of new elements taking advantage of the increase in the number of sensor nodes in the network due to the scalability of the system itself. The conversion solutions have been used to allow easy communication between the WSN and the smart grid system, and we also have used data aggregation and compression techniques to increase the lifetime of the wireless sensor network.
    Print ISSN: 1550-1329
    Electronic ISSN: 1550-1477
    Topics: Electrical Engineering, Measurement and Control Technology
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    Study on Zeeman-split spoof surface plasmon polaritons by use of spin-sensitive enhanced electromagnetic transmission (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: Structured metal surfaces could support spoof surface plasmon polaritons (SPPs), the dispersion of which is determined by the cutoff condition of guided modes in the nanostructures. We show that we can achieve split spoof SPPs by breaking the degeneracy of guided helical modes in concentric nanostructures via the classic analogue of the Zeeman effect. This split effect is shown to be observable from the spectra of enhanced electromagnetic transmission. Spin-sensitive enhanced electromagnetic transmission and the associated characteristics of field are investigated. Transmission branches versus parallel wavevector can be satisfactorily fitted by using the dispersion of spoof SPPs.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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    Formation kinetics of copper-related light-induced degradation in crystalline silicon (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: Light-induced degradation (LID) is a deleterious effect in crystalline silicon, which is considered to originate from recombination-active boron-oxygen complexes and/or copper-related defects. Although LID in both cases appears as a fast initial decay followed by a second slower degradation, we show that the time constant of copper-related degradation increases with increasing boron concentration in contrast to boron-oxygen LID. Temperature-dependent analysis reveals that the defect formation is limited by copper diffusion. Finally, interface defect density measurements confirm that copper-related LID is dominated by recombination in the wafer bulk.
    Print ISSN: 0021-8979
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    Intervalence charge transfer luminescence: Interplay between anomalous and 5d − 4f emissions in Yb-doped fluorite-type crystals (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: In this paper, we report the existence of intervalence charge transfer (IVCT) luminescence in Yb-doped fluorite-type crystals associated with Yb 2+ –Yb 3+ mixed valence pairs. By means of embedded cluster, wave function theory ab initio calculations, we show that the widely studied, very broad band, anomalous emission of Yb 2+ -doped CaF 2 and SrF 2 , usually associated with impurity-trapped excitons, is, rather, an IVCT luminescence associated with Yb 2+ –Yb 3+ mixed valence pairs. The IVCT luminescence is very efficiently excited by a two-photon upconversion mechanism where each photon provokes the same strong 4 f 14 –1 A 1g → 4 f 13 ( 2 F 7/2 )5 de g –1 T 1u absorption in the Yb 2+ part of the pair: the first one, from the pair ground state; the second one, from an excited state of the pair whose Yb 3+ moiety is in the higher 4 f 13 ( 2 F 5/2 ) multiplet. The Yb 2+ –Yb 3+ → Yb 3+ –Yb 2+ IVCT emission consists of an Yb 2+ 5 de g → Yb 3+ 4 f 7/2 charge transfer accompanied by a 4 f 7/2 → 4 f 5/2 deexcitation within the Yb 2+ 4 f 13 subshell: [ 2 F 5/2 5 de g , 2 F 7/2 ] → [ 2 F 7/2 ,4 f 14 ]. The IVCT vertical transition leaves the oxidized and reduced moieties of the pair after electron transfer very far from their equilibrium structures; this explains the unexpectedly large band width of the emission band and its low peak energy, because the large reorganization energies are subtracted from the normal emission. The IVCT energy diagrams resulting from the quantum mechanical calculations explain the different luminescent properties of Yb-doped CaF 2 , SrF 2 , BaF 2 , and SrCl 2 : the presence of IVCT luminescence in Yb-doped CaF 2 and SrF 2 ; its coexistence with regular 5 d -4 f emission in SrF 2 ; its absence in BaF 2 and SrCl 2 ; the quenching of all emissions in BaF 2 ; and the presence of additional 5 d –4 f emissions in SrCl 2 which are absent in SrF 2 . They also allow to interpret and reproduce recent experiments on transient photoluminescence enhancement in Yb 2+ -doped CaF 2 and SrF 2 , the appearance of Yb 2+ 4 f –5 d absorption bands in the excitation spectra of the IR Yb 3+ emission in partly reduced CaF 2 :Yb 3+ samples, and to identify the broadband observed in the excitation spectrum of the so far called anomalous emission of SrF 2 :Yb 2+ as an IVCT absorption, which corresponds to an Yb 2+ 4 f 5/2 → Yb 3+ 4 f 7/2 electron transfer.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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    Dynamics in the quantum/classical limit based on selective use of the quantum potential (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: A classical limit of quantum dynamics can be defined by compensation of the quantum potential in the time-dependent Schrödinger equation. The quantum potential is a non-local quantity, defined in the trajectory-based form of the Schrödinger equation, due to Madelung, de Broglie, and Bohm, which formally generates the quantum-mechanical features in dynamics. Selective inclusion of the quantum potential for the degrees of freedom deemed “quantum,” defines a hybrid quantum/classical dynamics, appropriate for molecular systems comprised of light and heavy nuclei. The wavefunction is associated with all of the nuclei, and the Ehrenfest, or mean-field, averaging of the force acting on the classical degrees of freedom, typical of the mixed quantum/classical methods, is avoided. The hybrid approach is used to examine evolution of light/heavy systems in the harmonic and double-well potentials, using conventional grid-based and approximate quantum-trajectory time propagation. The approximate quantum force is defined on spatial domains, which removes unphysical coupling of the wavefunction fragments corresponding to distinct classical channels or configurations. The quantum potential, associated with the quantum particle, generates forces acting on both quantum and classical particles to describe the backreaction.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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    The action principle for dissipative systems (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-17
    Description: In the present work, we redefine and generalize the action principle for dissipative systems proposed by Riewe by fixing the mathematical inconsistencies present in the original approach. In order to formulate a quadratic Lagrangian for non-conservative systems, the Lagrangian functions proposed depend on mixed integer order and fractional order derivatives. As examples, we formulate a quadratic Lagrangian for a particle under a frictional force proportional to the velocity and to the classical problem of an accelerated point charge.
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
    Published by American Institute of Physics (AIP)
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  • 87
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    Entanglement and the three-dimensionality of the Bloch ball (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: We consider a very natural generalization of quantum theory by letting the dimension of the Bloch ball be not necessarily three. We analyze bipartite state spaces where each of the components has a d -dimensional Euclidean ball as state space. In addition to this, we impose two very natural assumptions: the continuity and reversibility of dynamics and the possibility of characterizing bipartite states by local measurements. We classify all these bipartite state spaces and prove that, except for the quantum two-qubit state space, none of them contains entangled states. Equivalently, in any of these non-quantum theories, interacting dynamics is impossible. This result reveals that “existence of entanglement” is the requirement with minimal logical content which singles out quantum theory from our family of theories.
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
    Published by American Institute of Physics (AIP)
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  • 88
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    Conformal killing tensors and covariant Hamiltonian dynamics (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: A covariant algorithm for deriving the conserved quantities for natural Hamiltonian systems is combined with the non-relativistic framework of Eisenhart, and of Duval, in which the classical trajectories arise as geodesics in a higher dimensional space-time, realized by Brinkmann manifolds. Conserved quantities which are polynomial in the momenta can be built using time-dependent conformal Killing tensors with flux. The latter are associated with terms proportional to the Hamiltonian in the lower dimensional theory and with spectrum generating algebras for higher dimensional quantities of order 1 and 2 in the momenta. Illustrations of the general theory include the Runge-Lenz vector for planetary motion with a time-dependent gravitational constant G ( t ), motion in a time-dependent electromagnetic field of a certain form, quantum dots, the Hénon-Heiles and Holt systems, respectively, providing us with Killing tensors of rank that ranges from one to six.
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
    Published by American Institute of Physics (AIP)
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  • 89
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    EOQ Model for Deteriorating Items with Stock-Level-Dependent Demand Rate and Order-Quantity-Dependent Trade Credit (2014)
    Hindawi
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    Publication Date: 2014-12-17
    Description: This paper develops a generalized inventory model for exponentially deteriorating items with current-stock-dependent demand rate and permissible delay in payments. In the model, the payment for the item must be made immediately if the order quantity is less than the predetermined quantity; otherwise, a fixed trade credit period is permitted. The maximization of the average profit per unit of time is taken as the inventory system’s objective. The necessary and sufficient conditions and some properties of the optimal solution to the model are developed. Simple solution procedures are proposed to efficiently determine the optimal ordering policies of the considered problem. Numerical example is also presented to illustrate the solution procedures obtained.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 90
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    Microwave shielding enhancement of high-transparency, double-layer, submillimeter-period metallic mesh (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: We demonstrate both theoretically and experimentally that the microwave-shielding effectiveness of a double-layer metallic mesh with a submillimeter period can be improved by increasing the separation between the two mesh layers (without affecting transmittance). This double-layer mesh consists of two layers of square aluminum mesh separated by a quartz-glass substrate. By increasing the substrate's optical thickness from zero to λ / 4   of the shielding band's upper frequency, the shielding of the double-layer mesh improves considerably, owing to the increased reflectivity of the double-layer mesh with increasing separation in the low-frequency band. A Ku-band shielding effectiveness of over 32 dB is observed for the double-layer mesh with a normalized visible transmittance greater than 91%. It is found that the electromagnetic shielding effectiveness is enhanced by over 7 dB (80.0% energy attenuation) across the Ku-band, compared with that of a single-layer mesh, while the optical transmittances are almost identical for both tested structures. Such an enhancement permits the design of high-transparency optical elements with stronger microwave shielding that can be achieved using single-layer metallic mesh.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 91
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    Polarized micro Raman scattering spectroscopy for curved edges of epitaxial graphene (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: This letter performed polarized microscopic laser Raman scattering spectroscopy on the curved edges of transferred epitaxial graphene on SiO 2 /Si. The intensity ratio between the parallel and perpendicular polarized D band is evolved, providing a spectroscopy-based technique to probe the atomic-scale edge structures in graphene. A detailed analysis procedure for non-ideal disordered curved edges of graphene is developed combining the atomic-scale zigzag and armchair edge structures along with some point defects. These results could provide valuable information of the realistic edges of graphene at the atomic-scale that can strongly influence the performance of graphene-based nanodevices.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 92
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    Galactic outflow and diffuse gas properties at z 〉= 1 using different baryonic feedback models (2014)
    Oxford University Press
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    Publication Date: 2014-12-17
    Description: We measure and quantify properties of galactic outflows and diffuse gas at z ≥ 1 in cosmological hydrodynamical simulations. Our novel subresolution model, Multi-Phase Particle Integrator (MUPPI), implements supernova feedback using fully local gas properties, where the wind velocity and mass loading are not given as input. We find the following trends at z  = 2 by analysing central galaxies having a stellar mass higher than 10 9 M . The outflow velocity and mass outflow rate ( $\dot{M}_{\rm out}$ ) exhibit positive correlations with galaxy mass and with the star formation rate (SFR). However, most of the relations present a large scatter. The outflow mass loading factor () is between 0.2 and 10. The comparison effective model generates a constant outflow velocity, and a negative correlation of with halo mass. The number fraction of galaxies where outflow is detected decreases at lower redshifts, but remains more than 80 per cent over z  = 1–5. The outflow velocity correlation with SFR becomes flatter at z  = 1, and displays a negative correlation with halo mass in massive galaxies. Our study demonstrates that both the MUPPI and effective models produce significant outflows at ~1/10 of the virial radius; at the same time shows that the properties of outflows generated can be different from the input speed and mass loading in the effective model. Our MUPPI model, using local properties of gas in the subresolution recipe, is able to develop galactic outflows whose properties correlate with global galaxy properties , and consistent with observations.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 93
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    Encapsulated high frequency (235 kHz), high-Q (100 k) disk resonator gyroscope with electrostatic parametric pump (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-17
    Description: In this paper, we explore the effects of electrostatic parametric amplification on a high quality factor (Q 〉 100 000) encapsulated disk resonator gyroscope (DRG), fabricated in 〈100〉 silicon. The DRG was operated in the n = 2 degenerate wineglass mode at 235 kHz, and electrostatically tuned so that the frequency split between the two degenerate modes was less than 100 mHz. A parametric pump at twice the resonant frequency is applied to the sense axis of the DRG, resulting in a maximum scale factor of 156.6  μ V/(°/s), an 8.8× improvement over the non-amplified performance. When operated with a parametric gain of 5.4, a minimum angle random walk of 0.034°/√h and bias instability of 1.15°/h are achieved, representing an improvement by a factor of 4.3× and 1.5×, respectively.
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    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 94
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    Josephson magnetic rotary valve (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: We propose a control element for a Josephson spin valve. It is a complex Josephson device containing ferromagnetic (F) layer in the weak-link area consisting of two regions, representing 0 and π Josephson junctions, respectively. The valve's state is defined by mutual orientations of the F-layer magnetization vector and boundary line between 0 and π sections of the device. We consider possible implementation of the control element by introduction of a thin normal metal layer in a part of the device area. By means of theoretical simulations, we study properties of the valve's structure as well as its operation, revealing such advantages as simplicity of control, high characteristic frequency, and good legibility of the basic states.
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    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 95
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    Structural observation of piezoelectric inhomogeneity in a mixed-orientation Na0.5Bi0.5TiO3 perovskite thin film (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-17
    Description: Thin films of the lead-free ferroelectric Na 0.5 Bi 0.5 TiO 3 grown on thin-film Pt electrodes supported by SrTiO 3 substrates have a complex microstructure consisting of crystalline grains with three distinct major crystallographic orientations. The piezoelectric response measured in spatially separated sub-micron grains using time-resolved synchrotron x-ray microdiffraction is highly inhomogeneous even among grains sharing the same major orientation. The piezoelectric coefficient d 33 varies by nearly a factor of two in a series of areas sharing the 〈001〉 orientation. The piezoelectric inhomogeneity is linked to the peculiar microstructure of the film, arising from local variations in the stress imposed by surrounding grains with different crystallographic orientations and differing directions of the ferroelectric remnant polarization. A systematic nonlinearity of the piezoelectric strain is observed in applied electric fields with small magnitudes in all regions, consistent with the coexistence of domains of differing polarization direction at zero applied electric field.
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    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 96
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    Multiplex sequencing of pooled mitochondrial genomes--a crucial step toward biodiversity analysis using mito-metagenomics (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-17
    Description: The advent in high-throughput-sequencing (HTS) technologies has revolutionized conventional biodiversity research by enabling parallel capture of DNA sequences possessing species-level diagnosis. However, polymerase chain reaction (PCR)-based implementation is biased by the efficiency of primer binding across lineages of organisms. A PCR-free HTS approach will alleviate this artefact and significantly improve upon the multi-locus method utilizing full mitogenomes. Here we developed a novel multiplex sequencing and assembly pipeline allowing for simultaneous acquisition of full mitogenomes from pooled animals without DNA enrichment or amplification. By concatenating assemblies from three de novo assemblers, we obtained high-quality mitogenomes for all 49 pooled taxa, with 36 species 〉15 kb and the remaining 〉10 kb, including 20 complete mitogenomes and nearly all protein coding genes (99.6%). The assembly quality was carefully validated with Sanger sequences, reference genomes and conservativeness of protein coding genes across taxa. The new method was effective even for closely related taxa, e.g. three Drosophila spp., demonstrating its broad utility for biodiversity research and mito-phylogenomics. Finally, the in silico simulation showed that by recruiting multiple mito-loci, taxon detection was improved at a fixed sequencing depth. Combined, these results demonstrate the plausibility of a multi-locus mito-metagenomics approach as the next phase of the current single-locus metabarcoding method.
    Keywords: Genomics
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 97
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    Easy quantitative assessment of genome editing by sequence trace decomposition (2014)
    Oxford University Press
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    Publication Date: 2014-12-17
    Description: The efficacy and the mutation spectrum of genome editing methods can vary substantially depending on the targeted sequence. A simple, quick assay to accurately characterize and quantify the induced mutations is therefore needed. Here we present TIDE, a method for this purpose that requires only a pair of PCR reactions and two standard capillary sequencing runs. The sequence traces are then analyzed by a specially developed decomposition algorithm that identifies the major induced mutations in the projected editing site and accurately determines their frequency in a cell population. This method is cost-effective and quick, and it provides much more detailed information than current enzyme-based assays. An interactive web tool for automated decomposition of the sequence traces is available. TIDE greatly facilitates the testing and rational design of genome editing strategies.
    Keywords: Targeted gene modification
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 98
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    Accurate ab initio prediction of NMR chemical shifts of nucleic acids and nucleic acids/protein complexes (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-17
    Description: NMR chemical shift predictions based on empirical methods are nowadays indispensable tools during resonance assignment and 3D structure calculation of proteins. However, owing to the very limited statistical data basis, such methods are still in their infancy in the field of nucleic acids, especially when non-canonical structures and nucleic acid complexes are considered. Here, we present an ab initio approach for predicting proton chemical shifts of arbitrary nucleic acid structures based on state-of-the-art fragment-based quantum chemical calculations. We tested our prediction method on a diverse set of nucleic acid structures including double-stranded DNA, hairpins, DNA/protein complexes and chemically-modified DNA. Overall, our quantum chemical calculations yield highly/very accurate predictions with mean absolute deviations of 0.3–0.6 ppm and correlation coefficients ( r 2 ) usually above 0.9. This will allow for identifying misassignments and validating 3D structures. Furthermore, our calculations reveal that chemical shifts of protons involved in hydrogen bonding are predicted significantly less accurately. This is in part caused by insufficient inclusion of solvation effects. However, it also points toward shortcomings of current force fields used for structure determination of nucleic acids. Our quantum chemical calculations could therefore provide input for force field optimization.
    Keywords: Nucleic acid structure, Protein-nucleic acid interaction
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 99
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    Synthesis, biophysical properties and biological activity of second generation antisense oligonucleotides containing chiral phosphorothioate linkages (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-17
    Description: Bicyclic oxazaphospholidine monomers were used to prepare a series of phosphorothioate (PS)-modified gapmer antisense oligonucleotides (ASOs) with control of the chirality of each of the PS linkages within the 10-base gap. The stereoselectivity was determined to be 98% for each coupling. The objective of this work was to study how PS chirality influences biophysical and biological properties of the ASO including binding affinity ( T m ), nuclease stability, activity in vitro and in vivo , RNase H activation and cleavage patterns (both human and E. coli ) in a gapmer context. Compounds that had nine or more Sp-linkages in the gap were found to be poorly active in vitro , while compounds with uniform Rp-gaps exhibited activity very similar to that of the stereo-random parent ASOs. Conversely, when tested in vivo , the full Rp-gap compound was found to be quickly metabolized resulting in low activity. A total of 31 ASOs were prepared with control of the PS chirally of each linkage within the gap in an attempt to identify favorable Rp/Sp positions. We conclude that a mix of Rp and Sp is required to achieve a balance between good activity and nuclease stability.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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    qDNAmod: a statistical model-based tool to reveal intercellular heterogeneity of DNA modification from SMRT sequencing data (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-17
    Description: In an isogenic cell population, phenotypic heterogeneity among individual cells is common and critical for survival of the population under different environment conditions. DNA modification is an important epigenetic factor that can regulate phenotypic heterogeneity. The single molecule real-time (SMRT) sequencing technology provides a unique platform for detecting a wide range of DNA modifications, including N6-methyladenine (6-mA), N4-methylcytosine (4-mC) and 5-methylcytosine (5-mC). Here we present qDNAmod, a novel bioinformatic tool for genome-wide quantitative profiling of intercellular heterogeneity of DNA modification from SMRT sequencing data. It is capable of estimating proportion of isogenic haploid cells, in which the same loci of the genome are differentially modified. We tested the reliability of qDNAmod with the SMRT sequencing data of Streptococcus pneumoniae strain ST556. qDNAmod detected extensive intercellular heterogeneity of DNA methylation (6-mA) in a clonal population of ST556. Subsequent biochemical analyses revealed that the recognition sequences of two type I restriction–modification (R-M) systems are responsible for the intercellular heterogeneity of DNA methylation initially identified by qDNAmod. qDNAmod thus represents a valuable tool for studying intercellular phenotypic heterogeneity from genome-wide DNA modification.
    Keywords: Nucleic acid modification, Computational Methods
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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