bluuebunny/crossref_metadata_2025 huggingface dataset:
HIV epidemic trend and antiretroviral treatment need in Karonga District, Malawi
Authors: WHITE R. G. , VYNNYCKY E. , GLYNN J. R. , CRAMPIN A. C. , JAHN A. , MWAUNGULU F. , MWANYONGO O. , JABU H. , PHIRI H. , McGRATH N. , ZABA B. , FINE P. E. M.
Published: January 2007

We describe the development of the HIV epidemic in Karonga District, Malawi over 22 years using data from population surveys and community samples. These data are used to estimate the trend in HIV prevalence, incidence and need for antiretroviral treatment (ART) using a simple mathematical model. HIV prevalence rose quickly in the late 1980s and early 1990s, stabilizing at around 12% in the mid-1990s. Estimated annual HIV incidence rose quickly, peaking in the early 1990s at 2·2% among males and 3·1% among females, and then levelled off at 1·3% among males and 1·1% among females by the late 1990s. Assuming a 2-year eligibility period, both our model and the UNAIDS models predicted 2·1% of adults were in need of ART in 2005. This prediction was sensitive to the assumed eligibility period, ranging from 1·6% to 2·6% if the eligibility period was instead assumed to be 1·5 or 2·5 years, respectively.
HIV-1 and HIV-2 prevalence and associated risk factors among postnatal women in Harare, Zimbabwe
Authors: HUMPHREY J. H. , NATHOO K. J. , HARGROVE J. W. , ILIFF P. J. , MUTASA K. E. , MOULTON L. H. , CHIDAWANYIKA H. , MALABA L. C. , ZIJENAH L. S. , ZVANDASARA P. , NTOZINI R. , ZUNGUZA C. D. , WARD B. J. ,   and the ZVITAMBO Study Group
Published: January 2007

Studies of antenatal women form the predominant source of data on HIV-1 prevalence in Africa. Identifying factors associated with prevalent HIV is important in targeting diagnostic services and care. Between November 1997 and January 2000, 14 110 postnatal women from Harare, Zimbabwe were tested by ELISAs reactive to both HIV-1 and HIV-2; a subset of positive samples was confirmed with assays specific for HIV-1 and HIV-2. Baseline characteristics were elicited and modelled to identify risk factors for prevalent HIV infection. HIV-1 and HIV-2 prevalences were 32·0% (95% CI 31·2–32·8) and 1·3% (95% CI 1·1–1·5), respectively; 4% of HIV-1-positive and 99% of HIV-2-positive women were co-infected. HIV-1 prevalence increased from 0% among 14-year-olds to >45% among women aged 29–31 years, then fell to <20% among those aged >40 years. In multivariate analyses, prevalence increased with parity, was lower in married women than in single women, divorcees and widows, and higher in women with the lowest incomes and those professing no religion. Adjusted HIV-1 prevalence increased during 1998 and decreased during 1999. Age modified the effects of parity, home ownership and parental education. Among older women, prevalence was greater for women who were not homeowners. Among younger women, prevalence increased with parity and low parental education. None of these factors distinguished women co-infected with HIV-2 from those infected with HIV-1 alone. Prevalent HIV-1 infection is associated with financial insecurity and weak psychosocial support. The ZVITAMBO study apparently spanned the peak of the HIV-1 epidemic among reproductive women in Harare.
Comparison of smallpox outbreak control strategies using a spatial metapopulation model
Authors: HALL I. M. , EGAN J. R. , BARRASS I. , GANI R. , LEACH S.
Published: January 2007

To determine the potential benefits of regionally targeted mass vaccination as an adjunct to other smallpox control strategies we employed a spatial metapopulation patch model based on the administrative districts of Great Britain. We counted deaths due to smallpox and to vaccination to identify strategies that minimized total deaths. Results confirm that case isolation, and the tracing, vaccination and observation of case contacts can be optimal for control but only for optimistic assumptions concerning, for example, the basic reproduction number for smallpox (R0=3) and smaller numbers of index cases (∼10). For a wider range of scenarios, including larger numbers of index cases and higher reproduction numbers, the addition of mass vaccination targeted only to infected districts provided an appreciable benefit (5–80% fewer deaths depending on where the outbreak started with a trigger value of 1–10 isolated symptomatic individuals within a district).
Phänomenologie und Komorbidität der Zwangsstörung bei Kindern und Jugendlichen
Authors: Jans Thomas , Wewetzer Christoph , Klampfl Karin , Schulz Eberhard , Herpertz-Dahlmann Beate , Remschmidt Helmut , Warnke Andreas
Published: January 2007

Zusammenfassung: Fragestellung: Gegenstand der Studie waren die Symptomatologie und die Komorbidität der Zwangsstörung mit Beginn im Kindes- und Jugendalter. Methodik: Untersucht wurde eine Inanspruchnahmestichprobe von 55 kinder- und jugendpsychiatrischen Patienten (29 männlich, 26 weiblich), die überwiegend stationär behandelt wurden (95%). Strukturierte diagnostische Interviews zur Erfassung von Zwangsstörung und weiteren psychischen Störungen wurden zu Befragungen von Eltern und Kind eingesetzt. Ergebnis: Das mittlere Alter bei Beginn der Zwangsstörung betrug 11,3 Jahre. Jungen waren bei Störungsbeginn etwas, aber nicht statistisch signifikant jünger als Mädchen. Zwangshandlungen bezogen sich vorwiegend auf Waschen und Sauberkeit, Kontrollieren sowie Wiederholungen, Ordnen und Zählen. Zwangsgedanken beinhalteten vor allem Verunreinigung, die Erwartung schlimmer Ereignisse, Sexualität oder Aggression. In der klinischen Behandlungsroutine wurden seltener eine gemischte Zwangsstörung mit Gedanken und Handlungen diagnostiziert als bei Anwendung strukturierter Interviews. Die Komorbiditätsrate war Elternangaben zufolge hoch (Lebenszeit-Diagnosen: 69%; aktuelle Diagnosen: 53%). Angststörungen, affektive Störungen, hyperkinetische Störungen, Störungen des Sozialverhaltens und Ess-Störungen standen im Vordergrund. Die Zwangssymptomatik war bei Patienten mit einer höheren Anzahl an komorbiden Lebenszeitdiagnosen signifikant stärker ausgeprägt. Schlussfolgerungen: Die Studienergebnisse stehen in Einklang mit denjenigen internationaler Studien. Deutlich wurde eine Methodenabhängigkeit gestellter Diagnosen. In der Subtypisierung von Patientengruppen durch Symptomdimensionen wird ein fruchtbarer Ansatz für weitere Studien gesehen.
Wie gut stimmen Eltern und Erzieherinnen in der Beurteilung von Verhaltensproblemen bei Kindergartenkindern überein?
Authors: Kuschel Annett , Heinrichs Nina , Bertram Heike , Naumann Sebastian , Hahlweg Kurt
Published: January 2007

Zusammenfassung: Fragestellung: Im Rahmen zweier Projekte zur Wirksamkeit universeller und selektiver Präventionsmaßnahmen für Familien mit Vorschulkindern wird untersucht, wie gut Mütter, Väter und Erzieherinnen in der Einschätzung von Verhaltensproblemen bei Kindergartenkindern übereinstimmen. Methode: Die Rekrutierung der Familien erfolgte über Kindertagesstätten in Braunschweig. Von N = 310 Kindern im Alter zwischen drei und sechs Jahren liegen Einschätzungen vor, die mit Hilfe des Eltern- bzw. Erzieherinnenfragebogens über das Verhalten von Klein- und Vorschulkindern (CBCL 11/2-5; C-TRF 11/2-5) erhoben wurden. Ergebnisse: Zwischen den Eltern besteht eine sehr gute Übereinstimmung in der Beurteilung von Verhaltensproblemen; im Vergleich zu den Erzieherinnen schätzen Eltern die Kinder als auffälliger ein. Der Median der Intraklassenkorrelationen für das Elternurteil liegt bei 0.64, für den Vergleich Eltern- vs. Erzieherinnenurteil bei 0.18 bzw. 0.17. Im Bereich erhöhter Auffälligkeiten wird für die Eltern ein mittleres κ von 0.41 ermittelt, während zwischen Eltern/Erziehern diesbezüglich keine Übereinstimmung besteht. Diskussion: Abschließend werden die vorliegenden Ergebnisse mit anderen Untersuchungen verglichen und Implikationen vor allem für die Diagnostik psychischer Störungen im Vorschulalter diskutiert.
Space geodetic determination of spatial variability in relative sea level change, Los Angeles basin
Authors: Brooks B. A. , Merrifield M. A. , Foster J. , Werner C. L. , Gomez F. , Bevis M. , Gill S.
Published: January 2007

We combine Synthetic Aperture Radar Interferometry (InSAR), tide gauge, and continuous GPS measurements to determine the spatial variation in vertical land motion (VLM) along the coast of the Los Angeles basin over the past decade, and to examine the impact of spatially variable VLM on relative sea level trends. By identifying radar scattering targets with long‐term coherence we make height corrections which allow interferogram creation for nearly the entire ERS‐1 catalog and permit estimation of average deformation rates with minimal temporal aliasing. Between Los Angeles Harbor and Newport Beach, mean VLM trends range from ∼3.4 to −4.3 mm/yr, reflecting the high level of ground water and oil extraction activity in the region. West of Los Angeles Harbor, VLM rates and spatial variability are roughly half as large. The 8‐year VLM trends exceed the long‐term sea level trend (0.8 mm/yr) determined from the 80 year Los Angeles Harbor tide gauge. The high degree of observed VLM variability emphasizes the need for the spatially continuous measurements provided by InSAR; a single tide gauge assessment of regional RSL would otherwise have limited applicability.
Oxygenated and water‐soluble organic aerosols in Tokyo
Authors: Kondo Y. , Miyazaki Y. , Takegawa N. , Miyakawa T. , Weber R. J. , Jimenez J. L. , Zhang Q. , Worsnop D. R.
Published: January 2007

Submicron organic aerosol was measured simultaneously with an Aerodyne aerosol mass spectrometer (AMS) and a particle‐into‐liquid sampler (PILS) capable of measuring water‐soluble organic carbon (WSOC) during the winter and summer of 2004 in Tokyo. Both techniques are being used to investigate the formation of secondary organic aerosol (SOA), and the combined data sets provide unique insights. In summer, about 80% (40–65%) of organic aerosols were oxygenated when scaled by total (carbon) mass concentration, due to high photochemical activity, leading to the active formation of SOA. In winter the fraction of oxygenated organic aerosol is reduced to 39% (total mass base) and 23% (carbon mass base). Previous AMS studies have shown that signals at m/z 44 of the AMS mass spectra of ambient aerosols are dominated by COO+, which typically originates from oxygenated organic aerosols (OOA). The signals at m/z 44 and the derived OOA mass concentrations were highly correlated with WSOC (r2 = 0.78–0.91) throughout these seasons, indicating that OOA and WSOC were very similar in their chemical characteristics. Approximately 88 ± 29% of OOA was found to be water soluble on the basis of the comparison of the WSOC concentrations with those of oxygenated organic carbon (OOC) derived from the AMS data.
Regional carbon fluxes and the effect of topography on the variability of atmospheric CO2
Authors: van der Molen M. K. , Dolman A. J.
Published: January 2007

Using a mesoscale atmospheric circulation model, it is shown that relatively modest topography height differences of ∼500 m over 200 km near Zotino (60°N, 89°E) in central Siberia may generate horizontal gradients in CO2 concentration in the order of 30 ppm. In a case study for 15 and 16 July 1996, when Lloyd et al. (2001) conducted a convective boundary layer budget experiment in the area, we show that advection of these gradients disturbs the relation between diurnal concentration changes in the boundary layer and the surface fluxes. This demonstrates that mesoscale atmospheric heterogeneity may have severe impact on the applicability of methods to derive the regional‐scale fluxes from CO2 concentrations measurements, such as the convective boundary layer budget method or inverse modeling. It is shown that similar mesoscale gradients are likely to occur at many long‐term observation stations and tall towers. We use the modeled concentration fields to quantify the horizontal and vertical variability of carbon dioxide in the atmosphere. In future observation campaigns, mesoscale processes may be best accounted for by measuring horizontal variability over a few hundred kilometers and by attempting to quantify the representation errors as a function of mesoscale conditions.
Extreme electron fluxes in the outer zone
Authors: O'Brien T. P. , Fennell J. F. , Roeder J. L. , Reeves G. D.
Published: January 2007

Following the work of Koons (2001), we examine the statistical properties of extremely high fluxes of MeV electrons in the outer zone. We extend the analysis to include a variety of timescales and energies using observations from Los Alamos monitors at geosynchronous orbit and to include outer zone fluxes observed from L ∼ 2–8 by spacecraft in highly elliptical Molniya orbits. We use the statistical formalism of the generalized extreme value distribution, which represents the probability distribution of the maximum value taken out of a sample of fixed size. By taking the maximum flux observed in many nonoverlapping intervals of several hours to several days, we can determine whether the maximum flux is likely to have a finite upper limit or an exponential or power law tail. Our analysis indicates that MeV electron fluxes over a broad range of energies, L shells, and timescales have a finite upper limit, a true worst case. However, the statistical estimate of this upper limit is inherently uncertain. We compare our upper limits to the internal charging specifications provided by Fennell et al. (2000). We discuss several possible physical explanations for the flux limits.
Escherichia coli with a linear genome
Authors: Cui Tailin , Moro‐oka Naoki , Ohsumi Katsufumi , Kodama Kenichi , Ohshima Taku , Ogasawara Naotake , Mori Hirotada , Wanner Barry , Niki Hironori , Horiuchi Takashi
Published: January 2007

Chromosomes in eukaryotes are linear, whereas those of most, but not all, prokaryotes are circular. To explore the effects of possessing a linear genome on prokaryotic cells, we linearized the Escherichia coli genome using the lysogenic λ‐like phage N15. Linear genome E. coli were viable and their genome structure was stable. There were no appreciable differences between cells with linear or circular genomes in growth rates, cell and nucleoid morphologies, genome‐wide gene expression (with a few exceptions), and DNA gyrase‐ and topoisomerase IV‐dependent growth. However, under dif‐defective conditions, only cells with a circular genome developed an abnormal phenotype. Microscopy indicated that the ends of the linear genome, but not the circular genome, were separated and located at each end of a new‐born cell. When tos—the cis‐element required for linearization—was inserted into different chromosomal sites, those strains with the genome termini that were more remote from dif showed greater growth deficiencies.
Tunable negative refraction based on the Pockels effect in two-dimensional photonic crystals composed of electro-optic crystals
Authors: Li Jian , Lu Ming-Hui , Feng Liang , Liu Xiao-Ping , Chen Yan-Feng
Published: January 2007

A two-dimensional square lattice photonic crystal composed of ferroelectric cylinder rods in air background is proposed to realize tunable negative refraction by applying electric field. Based on the Pockels effect, refractive indices of rods can be changed linearly along with applied electric field, and then photonic band structure and equifrequency surface can be modified. The refractive angle could vary from negative to positive depending on intensity of electric field at a certain incident angle. The feasibility of the photonic crystal operating in visible region at the frequency of 476.5THz was presented, which might have potential applications in photoelectronic devices.
Unusual vortex structure in ultrathin Pb(Zr0.5Ti0.5)O3 films
Authors: Wu Zhongqing , Huang Ningdong , Liu Zhirong , Wu Jian , Duan Wenhui , Gu Bing-Lin
Published: January 2007

Using a first-principles-based approach, we determine the ferroelectric pattern in PbZr0.5Ti0.5O3 ultrathin film. It is found that vortex stripes are formed in the system. The relation between the vortex stripes and the 180° domains is discussed. When a local external field is exerted, the vortex stripe transforms into the vortex loop structure, which leads to the formation of a smaller domain with the polarization antiparallel to the field in the center of the field region. This may provide a convenient way to manipulate nanodomains in thin films.
Vapor phase nucleation on neutral and charged nanoparticles: Condensation of supersaturated trifluoroethanol on Mg nanoparticles
Authors: Abdelsayed Victor , Samy El-Shall M.
Published: January 2007

A new technique is described to study the condensation of supersaturated vapors on nanoparticles under well-defined conditions of vapor supersaturation, temperature, and carrier gas pressure. The method is applied to the condensation of supersaturated trifluoroethanol (TFE) vapor on Mg nanoparticles. The nanoparticles can be activated to act as condensation nuclei at supersaturations significantly lower than those required for homogeneous nucleation. The number of activated nanoparticles increases with increasing the vapor supersaturation. The small difference observed in the number of droplets formed on positively and negatively charged nanoparticles is attributed to the difference in the mobilities of these nanoparticles. Therefore, no significant charge preference is observed for the condensation of TFE vapor on the Mg nanoparticles.
Hidden geometric character of relativistic quantum mechanics
Authors: Almeida José B.
Published: January 2007

Geometry can be an unsuspected source of equations with physical relevance, as everybody is aware since Einstein formulated the general theory of relativity. However, efforts to extend a similar type of reasoning to other areas of physics, namely, electrodynamics, quantum mechanics, and particle physics, usually had very limited success; particularly in quantum mechanics the standard formalism is such that any possible relation to geometry is impossible to detect; other authors have previously trod the geometric path to quantum mechanics, some of that work being referred to in the text. In this presentation we will follow an alternate route to show that quantum mechanics has indeed a strong geometric character. The paper makes use of geometric algebra, also known as Clifford algebra, in five-dimensional space-time. The choice of this space is given the character of first principle, justified solely by the consequences that can be derived from such choice and their consistency with experimental results. Given a metric space of any dimension, one can define monogenic functions, the natural extension of analytic functions to higher dimensions; such functions have null vector derivative and have previously been shown by other authors to play a decisive role in lower dimensional spaces. All monogenic functions have null Laplacian by consequence; in a hyperbolic space this fact leads inevitably to a wave equation with planelike solutions. This is also true for five-dimensional space-time and we will explore those solutions, establishing a parallel with the solutions of the free particle Dirac equation. For this purpose we will invoke the isomorphism between the complex algebra of 4×4 matrices, also known as Dirac’s matrices. There is one problem with this isomorphism, because the solutions to Dirac’s equation are usually known as spinors (column matrices) that do not belong to the 4×4 matrix algebra and as such are excluded from the isomorphism. We will show that a solution in terms of Dirac spinors is equivalent to a plane wave solution. Just as one finds in the standard formulation, monogenic functions can be naturally split into positive∕negative energy together with left∕right ones. This split is provided by geometric projectors and we will show that there is a second set of projectors providing an alternate fourfold split. The possible implications of this alternate split are not yet fully understood and are presently the subject of profound research.
Negative compressibility and nonequivalence of two statistical ensembles in the escape transition of a polymer chain
Authors: Skvortsov A. M. , Klushin L. I. , Leermakers F. A. M.
Published: January 2007

An end-tethered polymer chain compressed between two pistons undergoes an abrupt transition from a confined coil state to an inhomogeneous flowerlike conformation partially escaped from the gap. This phase transition is first order in the thermodynamic limit of infinitely long chains. A rigorous analytical theory is presented for a Gaussian chain in two ensembles: (a) the H-ensemble, in which the distance H between the pistons plays the role of the independent control parameter, and (b) the conjugate f-ensemble, in which the external compression force f is the independent parameter. Details about the metastable chain configurations are analyzed by introducing the Landau free energy as a function of the chain stretching order parameter. The binodal and spinodal lines, as well as the barrier heights between the stable and metastable states in the free energy landscape, are presented in both ensembles. In the loop region for the average force with dependence on the distance H (i.e., in the H-ensemble) a negative compressibility exists, whereas in the f-ensemble the average distance as a function of the force is strictly monotonic. The average fraction of imprisoned segments and the lateral force, taken as functions of the distance H or the average H, respectively, have different behaviors in the two ensembles. These results demonstrate a clear counterexample of a main principle of statistical mechanics, stating that all ensembles are equivalent in the thermodynamic limit. The authors show that the negative compressibility in the escape transition is a purely equilibrium result and analyze in detail the origin of the nonequivalence of the ensembles. It is argued that it should be possible to employ the escape transition and its anomalous behavior in macroscopically homogeneous, but microscopically inhomogeneous, materials.
Coulomb explosion of K-shell ionized krypton clusters studied by multiple-ion coincidence momentum imaging
Authors: Iwayama H. , Nagaya K. , Murakami H. , Ohmasa Y. , Yao M.
Published: January 2007

The Coulomb explosion of K-shell ionized krypton clusters with an average size ⟨N⟩ of 160 has been studied by electron-multiple-ion-coincidence measurements in which the time-of-flight (TOF) of ions was measured by using a position sensitive detector. The authors have sorted the TOF spectra by the number of coincidence ion signals, Ncoin, and found that singly charged fragment ions such as Kr+, Kr2+, and Kr3+ are dominant for Ncoin⩾2, and that multiply charged ions are detected mainly for Ncoin=1. The Ncoin dependence of the peak widths in the TOF spectra reveals that the average momentum of the Kr+ ions increases with Ncoin, while those of Kr2+ and Kr3+ decrease. These results have been more directly confirmed by the momentum imaging measurements. The authors propose that the heavier ions are produced in the central part of clusters where the Coulomb interactions from the surrounding ions are more effectively canceled out due to the higher symmetry.
Strain nonuniformity in GaAs heteroepitaxial films on Si(001) studied by x-ray diffraction
Authors: Shalimov Artem , Bąk-Misiuk Jadwiga , Kaganer Vladimir M. , Calamiotou Maria , Georgakilas Alexandros
Published: January 2007

High-resolution x-ray diffraction measurements are used to fully characterize the strain state of relaxed highly mismatched GaAs films, grown on vicinal Si (001) substrates by molecular beam epitaxy. The nonuniformity of the misfit dislocation network at the GaAs∕Si (001) interface is studied by analyzing the profiles of x-ray diffraction peaks and the reciprocal space maps for different reflections. The detailed analysis of the peak positions shows a dependence of the relaxation on the crystallographic direction, with the relaxation being larger in the direction perpendicular to the α-dislocation lines. Based on analytical expressions for the full width at half maximum in the longitudinal and transverse sections, an advanced version of the Williamson-Hall plot [Acta Metall. 1, 22 (1953)] is proposed that takes into account the geometry of dislocation distribution and the scattering geometry. We show that this type of analysis can reveal both the type and density of misfit dislocations. The measured peak widths are attributed to random uncorrelated 60°-type misfit dislocations with density much smaller than the total dislocation density required for lattice-mismatch relaxation. The major part of the GaAs∕Si lattice mismatch is accommodated by periodic arrays of edge-type perfect dislocations that do not cause nonuniform strain in the film. The applied theoretical and experimental analysis is easily applicable on other zinc blende highly lattice-mismatched systems.
Investigation on the electrical properties and inhomogeneous distribution of ZnO:Al thin films prepared by dc magnetron sputtering at low deposition temperature
Authors: Zhang X. B. , Pei Z. L. , Gong J. , Sun C.
Published: January 2007

A study of the electrical properties and spatial distribution of the ZnO:Al (AZO) thin films prepared by dc magnetron sputtering at low deposition temperature was presented, with emphasis on the origin of the resistivity inhomogeneity across the substrate. Various growth conditions were obtained by manipulating the growth temperature TS, total pressure PT, and ion-to-neutral ratio Ji∕Jn. The plasma characteristics such as radial ion density and floating/plasma potential distribution over the substrate were measured by Langmuir probe, while the flux and energy distribution of energetic species were estimated through Monte Carlo simulations. The crystalline, stress and electrical properties of the films were found to be strongly dependent on TS and Ji∕Jn. Under the low Ji∕Jn (<0.3) conditions, the TS exerted a remarkable influence on film quality. The films prepared at 90°C were highly compressed, exhibiting poor electrical properties and significant spatial distribution. High quality films with low stress and resistivity were produced at higher TS (200°C). Similarly, at lower TS (90°C), higher Ji∕Jn (∼2) dramatically improved the film resistivity as well as its lateral distribution. Moreover, it indicated that the role of ion bombardment is dependent on the mechanism of dissipation of incident species. Ion bombardment is beneficial to the film growth if the energy of incident species Ei is below the penetration threshold Epet (∼33eV for ZnO); on the other hand, the energy subimplant mechanism would work, and the bombardment degrades the film quality when Ei is over the Epet. The energetic bombardment of negative oxygen ions rather than the positives dominated the resistivity distribution of AZO films, while the nonuniform distribution of active oxygen played a secondary role which was otherwise more notable under conditions of lower TS and Ji∕Jn.
Coexistence of critical and normal state magnetostrictions in type II superconductors: A model exploration
Authors: Çelebi S. , Inanir F. , LeBlanc M. A. R.
Published: January 2007

Exploiting the simple formula proposed by Ikuta et al. [Phy. Rev. Lett. 70, 2166 (1993)] to describe the magnetostriction of high TC superconductors and introducing a B2 dependent magnetic flux density component, as proposed by Koziol and Dunlap [J. Appl. Phys. 79, 4662 (1996)], we reproduce families of magnetostriction curves measured by Nabialek et al. [Physica B 319, 286 (2002)] and de Visser et al. [Phys. Rev. B 45, 2962 (1992)], using a simple expression for the dependence of the critical current density JC on the magnetic field in each analysis.
Transmission electron microscopy study on the polycrystalline CoFeB∕MgO∕CoFeB based magnetic tunnel junction showing a high tunneling magnetoresistance, predicted in single crystal magnetic tunnel junction
Authors: Choi Y. S. , Tsunekawa K. , Nagamine Y. , Djayaprawira D.
Published: January 2007

We carried out a detailed transmission electron microscopy study on the polycrystalline CoFeB∕MgO∕CoFeB based magnetic tunnel junction, which shows high magnetoresistance predicted theoretically only in single crystal magnetic tunnel junction. Previously it has been suggested that the crystallinity and degree of texture of MgO tunnel barrier play a crucial role in the polycrystalline system. Here we suggest, on top of the crystallinity issue of MgO, that a grain-to-grain epitaxy of CoFeB∕MgO∕CoFeB satisfies the prerequisite for the coherent tunneling for the giant tunneling magnetoresistance theoretically predicted.
Novel apparatus for joining of carbon-carbon composites
Authors: White Jeremiah D. E. , Mukasyan Alexander S. , La Forest Mark L. , Simpson Allen H.
Published: January 2007

A novel apparatus for joining carbon-carbon (C–C) composites is presented. This device was designed and built based on the concept of self-sustained oxygen-free high-temperature reactions. A layer of reactive mixture is contained between two disks of C–C composite that are to be joined. The stack is held in place between two electrodes, which are connected to a dc power supply. dc current is used to uniformly initiate the reaction in the reactive layer. The electrodes are also part of the pneumatic system, which applies a load to the stack. The designed hydraulic system is effective, lending to low cost and simplified, rapid, accurate operation. It provides a very short response time (∼10ms), which is important for the considered applications. All operational parameters such as initial and final loads, applied current, delay time between ignition and final load application, duration of Joule heating, and safety interlocks are controlled by a programable logic controller system. These features make it an efficient, user-friendly and safe machine to join refractory materials. The entire joining process takes place on the order of seconds, rather than hours as required for solid-state joining methods. The mechanical properties of the obtained joints are higher than those for the C–C composites.
Propagation of a cloud of hot electrons through a plasma in the presence of Langmuir scattering by ambient density fluctuations
Authors: Foroutan G. R. , Robinson P. A. , Sobhanian S. , Moslehi-Fard M. , Li B. , Cairns I. H.
Published: January 2007

Gas-dynamic theory is generalized to incorporate the effects of beam-driven Langmuir waves scattering off ambient density fluctuations, and the consequent effects on the propagation of a cloud of hot electrons in an inhomogeneous plasma. Assuming Langmuir scattering as the limit of nonlinear three-wave interactions with fluctuations that are weak, low-frequency, long-wavelength ion-sound waves, the net effect of scattering is equivalent to effective damping of the Langmuir waves. Under the assumption of self-similarity in the evolution of the beam and Langmuir wave distribution functions, gas-dynamic theory shows that the effects of Langmuir scattering on the beam distribution are equivalent to a perturbation in the injection profile of the beam. Analytical expressions are obtained for the height of the plateau of the beam distribution function, wave spectral number density, total wave and particle energy density, and the beam number density. The main results of gas-dynamic theory are then compared with simulation results from numerical solutions of quasilinear equations. The relaxation of the beam in velocity space is retarded in the presence of density fluctuations and the magnitude of the upper velocity boundary is less than that in the absence of fluctuations. There are four different regimes for the height of the plateau, corresponding to different stages of relaxation of the beam in velocity space. Moreover, Langmuir scattering results in transfer of electrons from moderate velocity to low velocity; this effect produces an enhancement in the beam number density at small distances near the injection site and a corresponding decrease at large distances. There are sharp decreases in the profiles of the beam and total wave energy densities, which are related to dissipation of energy at large phase velocities. Due to a slower velocity space diffusion of the beam distribution in the presence of scattering effects, the spatial width of the beam is reduced while its mean velocity of propagation increases slightly.
Generation of initial trajectories for transition path sampling of chemical reactions with ab initio molecular dynamics
Authors: Rowley Christopher N. , Woo Tom K.
Published: January 2007

Transition path sampling is an innovative method for focusing a molecular dynamics simulation on a reactive event. Although transition path sampling methods can generate an ensemble of reactive trajectories, an initial reactive trajectory must be generated by some other means. In this paper, the authors have evaluated three methods for generating initial reactive trajectories for transition path sampling with ab initio molecular dynamics. The authors have tested each of these methods on a set of chemical reactions involving the breaking and making of covalent bonds: the 1,2-hydrogen elimination in the borane-ammonia adduct, a tautomerization, and the Claisen rearrangement. The first method is to initiate trajectories from the potential energy transition state, which was effective for all reactions in the test set. Assigning atomic velocities found using normal mode analysis greatly improved the success of this method. The second method uses a high temperature molecular dynamics simulation and then iteratively reduces the total energy of the simulation until a low temperature reactive trajectory is found. This was effective in generating a low temperature trajectory from an initial trajectory run at 3000K of the tautomerization reaction, although it failed for the other two. The third uses an orbital based bias potential to find a reactive trajectory and uses this trajectory to initiate an unbiased trajectory. The authors found that a highest occupied molecular orbital–lowest unoccupied molecular orbital bias could be used to find a reactive trajectory for the Claisen rearrangement, although it failed for the other two reactions. These techniques will help make it practical to use transition path sampling to study chemical reaction mechanisms that involve bond breaking and forming.
Software defined photon counting system for time resolved x-ray experiments
Authors: Acremann Y. , Chembrolu V. , Strachan J. P. , Tyliszczak T. , Stöhr J.
Published: January 2007

The time structure of synchrotron radiation allows time resolved experiments with sub-100ps temporal resolution using a pump-probe approach. However, the relaxation time of the samples may require a lower repetition rate of the pump pulse compared to the full repetition rate of the x-ray pulses from the synchrotron. The use of only the x-ray pulse immediately following the pump pulse is not efficient and often requires special operation modes where only a few buckets of the storage ring are filled. We designed a novel software defined photon counting system that allows to implement a variety of pump-probe schemes at the full repetition rate. The high number of photon counters allows to detect the response of the sample at multiple time delays simultaneously, thus improving the efficiency of the experiment. The system has been successfully applied to time resolved scanning transmission x-ray microscopy. However, this technique is applicable more generally.
Trapping and storage of particles in electroactive microwells
Authors: Cordovez Bernardo , Psaltis Demetri , Erickson David
Published: January 2007

The authors describe electroactive microwells which exploit highly localized electrokinetic effects in order to actively concentrate, confine, store, and reject particles in well defined geometries. In this letter the authors present experimental results demonstrating repeatable trapping and repulsion of polystyrene particles in wells ranging in diameter from 6to20μm in the presence of a superimposed pressure driven flow. A comprehensive finite element model is developed to describe the transport physics involved in the attraction and repulsion processes. Immediate applications include active cell trapping, particle concentration and unlabeled sensing.
Silicon doping induced bending in aluminum nanowires
Authors: Chen Hung-Jen , Chen Yen-Yu , Hsieh Chin-Hua , Lin Su-Jien , Chou Li-Jen , Hsu Wen-Kuang
Published: January 2007

Bent aluminum nanowires are produced by heating equimolar mixture of aluminum and silicon, and bending is due to Al–Si formation. Calculation reveals that incorporation of Si into metal lattice induces cell stress, leading to nanowire growth deviation. An energy barrier is established at nanowire bends, similar to junction devices.
Doping-induced efficiency enhancement in organic photovoltaic devices
Authors: Chan M. Y. , Lai S. L. , Fung M. K. , Lee C. S. , Lee S. T.
Published: January 2007

Performance of organic photovoltaic (OPV) devices is dramatically enhanced by doping suitable fluorescent dyes into the donor and/or acceptor layers. By doping rubrene into standard CuPc∕C60 OPV cell, a high JSC of 30.1mA∕cm2, VOC of 0.58V, and an exceptionally high power conversion efficiency of 5.58% are achieved. The performance improvement is mainly attributed to efficient light absorption by rubrene in the range of 460–530nm where two hosts have low absorbance, leading to more effective exciton formation. Their findings motivate the use of fluorescent dyes for maximizing absorption spectral coverage as well as increasing photon harvesting.
Humicoccus flavidus gen. nov., sp. nov., isolated from soil
Authors: Yoon Jung-Hoon , Kang So-Jung , Jung Seo-Youn , Oh Tae-Kwang
Published: January 2007

A Gram-positive, non-motile, spherical, non-spore-forming bacterial strain, DS-52T, was isolated from soil from Dokdo, Korea, and its taxonomic position was investigated by using a polyphasic approach. It grew optimally at 25 °C and pH 6.0–7.0. Strain DS-52T had meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan, and galactose, mannose, xylose and rhamnose as whole-cell sugars. It contained MK-8(H4) and MK-9(H4) as the predominant menaquinones and anteiso-C15 : 0, iso-C15 : 0 and C17 : 0 as major fatty acids. Major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidyldimethylethanolamine. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain DS-52T is most closely related to the genus Nakamurella of the suborder Frankineae. Strain DS-52T exhibited 16S rRNA gene sequence similarity values of 96.5 % to Nakamurella multipartita JCM 9543T and 92.0–93.9 % to other members of the suborder Frankineae. The diagnostic diamino acid type and polar lipid profile of strain DS-52T were the same as those of the genus Nakamurella. However, strain DS-52T could be clearly distinguished from the genus Nakamurella by differences in predominant menaquinones, major fatty acids and cell-wall sugars. Accordingly, based on combined phenotypic, chemotaxonomic and phylogenetic data, strain DS-52T (=KCTC 19127T=CIP 108919T) is proposed as the type strain of a novel species in a new genus, Humicoccus flavidus gen. nov., sp. nov.
Agrococcus casei sp. nov., isolated from the surfaces of smear-ripened cheeses
Authors: Bora Nagamani , Vancanneyt Marc , Gelsomino Roberto , Swings Jean , Brennan Noelle , Cogan Timothy M. , Larpin Sandra , Desmasures Nathalie , Lechner Frieda Eliskases , Kroppenstedt Reiner M. , Ward Alan C. , Goodfellow Michael
Published: January 2007

Seven Gram-positive, coryneform bacteria with virtually identical whole-organism protein patterns were isolated from the surface of smear-ripened cheeses. Representatives of these strains were the subject of a polyphasic study designed to establish their taxonomic status. The organisms formed a distinct branch in theMicrobacteriaceae16S rRNA gene tree and were most closely related to members of the genusAgrococcus, sharing sequence similarities of 95.4–98.7 %. The chemotaxonomic profiles of the strains were consistent with their classification in the genusAgrococcus. The combined genotypic and phenotypic data show that the isolates should be classified in the genusAgrococcusas representatives of a novel species. The nameAgrococcus caseisp. nov. is proposed for this taxon. Isolate R-17892t2T(=DSM 18061T=LMG 22410T) is the type strain ofAgrococcus caseisp. nov.
Actinomadura rudentiformis sp. nov., isolated from soil
Authors: le Roes Marilize , Meyers Paul R.
Published: January 2007

As part of an antibiotic-screening programme, the actinomycete strain HMC1T was isolated from soil collected from the banks of the Gamka River in the Swartberg Nature Reserve, Western Cape Province, South Africa. The isolate produced branching vegetative mycelia, which entwined to form rope-like structures. It exhibited antibiosis against Enterococcus faecium VanA (a vancomycin-resistant clinical strain) and Mycobacterium aurum A+. Organic solvent extracts of the culture filtrate and mycelial mass of strain HMC1T exhibited moderate antibiosis against Mycobacterium aurum A+, Mycobacterium bovis BCG (Tokyo) and Mycobacterium tuberculosis H37RvT. The chemotaxonomic characteristics of strain HMC1T corresponded with those of members of the genus Actinomadura. Furthermore, phylogenetic analysis based on the 16S rRNA gene showed that the strain was closely related to members of the genus Actinomadura. Phenotypic and 16S rRNA gene sequence analyses indicated that strain HMC1T represents a novel species of the genus Actinomadura, for which the name Actinomadura rudentiformis sp. nov. is proposed. The type strain is HMC1T (=DSM 44962T=NRRL B-24458T).
Nocardioides furvisabuli sp. nov., isolated from black sand
Authors: Lee Soon Dong
Published: January 2007

A Gram-positive, rod-shaped, yellow-pigmented actinomycete, designated strain SBS-26T, was isolated from a sample of black sand from Samyang Beach on Jeju Island (Republic of Korea) and was subjected to polyphasic characterization to unravel its taxonomic status. Phylogenetic analyses based on 16S rRNA gene sequences revealed that the organism belongs to the genus Nocardioides but forms a distinct branch at the base of a Nocardioides ganghwensis–Nocardioides oleivorans cluster. The 16S rRNA gene sequence of strain SBS-26T showed the highest levels of similarity to those of N. ganghwensis JC2055T (97.7 %) and N. oleivorans DSM 16090T (97.6 %). The levels of 16S rRNA gene sequence similarity between strain SBS-26T and other members of the genera Nocardioides and Marmoricola were in the range 93.0–96.2 %. The following chemotaxonomic characteristics support the phylogenetic association of strain SBS-26T with members of the genus Nocardioides: ll-diaminopimelic acid as the principal diamino acid of the peptidoglycan, MK-8(H4) as the major menaquinone, iso-C16 : 0 as the predominant fatty acid and a DNA G+C content of 69.1 mol%. The polar lipids contained phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol and an unknown phospholipid. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, strain SBS-26T represents a novel species of the genus Nocardioides, for which the name Nocardioides furvisabuli sp. nov. is proposed. The type strain is strain SBS-26T (=JCM 13813T=NRRL B-24465T).
Sneathiella chinensis gen. nov., sp. nov., a novel marine alphaproteobacterium isolated from coastal sediment in Qingdao, China
Authors: Jordan Elizabeth Mary , Thompson Fabiano L. , Zhang Xiao-Hua , Li Yun , Vancanneyt Marc , Kroppenstedt Reiner M. , Priest Fergus G. , Austin Brian
Published: January 2007

The taxonomic position of strain LMG 23452T, which was isolated from coastal sediment from an aquaculture site near Qingdao, China, in 2000, was determined. Strain LMG 23452Tcomprised Gram-negative, non-spore-forming, motile rods and was found to be a halotolerant, aerobic, chemoheterotroph that produces catalase and oxidase. Comparative 16S rRNA gene sequence analysis revealed that strain LMG 23452Tshared approximately 89 % sequence similarity with members of the generaDevosia,Hyphomonas,EnsiferandChelatococcus, which belong to two different orders within theAlphaproteobacteria. Further phylogenetic analysis of the 16S rRNA gene sequence showed that strain LMG 23452Tformed a separate branch within the orderRhizobiales, falling between the generaDevosiaandEnsiferof the familiesHyphomicrobiaceaeandRhizobiaceae, respectively. Strain LMG 23452Tcould be differentiated from its closest phylogenetic neighbours on the basis of several phenotypic features, including hydrolysis of the substrates starch and casein and assimilation of the carbohydratesd-glucose,d-mannose, mannitol, maltose andl-arabinose, and chemotaxonomically by the presence of the fatty acids C14 : 03-OH, C16 : 1ω11c, C16 : 1ω5cand C18 : 1ω5c. The major fatty acids detected in strain LMG 23452Twere C18 : 1ω7c, C16 : 0, C19 : 0cycloω8c, C16 : 1ω7cand C17 : 1ω6cand the G+C content of the genomic DNA was 57.1 mol%. Therefore, the polyphasic data support the placement of strain LMG 23452Twithin a novel genus and species, for which the nameSneathiella chinensisgen. nov., sp. nov. is proposed. The type strain is LMG 23452T(=CBMAI 737T).
DNA–DNA hybridization values and their relationship to whole-genome sequence similarities
Authors: Goris Johan , Konstantinidis Konstantinos T. , Klappenbach Joel A. , Coenye Tom , Vandamme Peter , Tiedje James M.
Published: January 2007

DNA–DNA hybridization (DDH) values have been used by bacterial taxonomists since the 1960s to determine relatedness between strains and are still the most important criterion in the delineation of bacterial species. Since the extent of hybridization between a pair of strains is ultimately governed by their respective genomic sequences, we examined the quantitative relationship between DDH values and genome sequence-derived parameters, such as the average nucleotide identity (ANI) of common genes and the percentage of conserved DNA. A total of 124 DDH values were determined for 28 strains for which genome sequences were available. The strains belong to six important and diverse groups of bacteria for which the intra-group 16S rRNA gene sequence identity was greater than 94 %. The results revealed a close relationship between DDH values and ANI and between DNA–DNA hybridization and the percentage of conserved DNA for each pair of strains. The recommended cut-off point of 70 % DDH for species delineation corresponded to 95 % ANI and 69 % conserved DNA. When the analysis was restricted to the protein-coding portion of the genome, 70 % DDH corresponded to 85 % conserved genes for a pair of strains. These results reveal extensive gene diversity within the current concept of ‘species’. Examination of reciprocal values indicated that the level of experimental error associated with the DDH method is too high to reveal the subtle differences in genome size among the strains sampled. It is concluded that ANI can accurately replace DDH values for strains for which genome sequences are available.
Marinobacterium halophilum sp. nov., a marine bacterium isolated from the Yellow Sea
Authors: Chang Ho-Won , Nam Young-Do , Kwon Hyuk-Yong , Park Ja Ryeong , Lee Jung-Sook , Yoon Jung-Hoon , An Kwang-Guk , Bae Jin-Woo
Published: January 2007

A moderately halophilic, aerobic, Gram-negative bacterium was isolated from a tidal flat area of Dae-Chun, Chung-Nam, Korea. The strain, designated mano11T, comprised rod-shaped cells that were motile by means of polar flagella. It grew with 3–12 % NaCl and at 4–37 °C and pH 5.3–9.3. The predominant menaquinone present in this strain was MK-7 and diaminopimelic acid was not found in the cell-wall peptidoglycan. A phylogenetic analysis based on 16S rRNA gene sequences showed that strain mano11T belongs to the genus Marinobacterium. Strain mano11T exhibited 92.8–98.3 % 16S rRNA gene sequence similarity when compared with the type strains of three other species of the genus Marinobacterium. DNA–DNA hybridization between strain mano11T and Marinobacterium georgiense DSM 11526T, its closest relative in terms of 16S rRNA gene sequence similarity, was 13 %. On the basis of the phenotypic, genetic and phylogenetic data, strain mano11T represents a novel species of the genus Marinobacterium, for which the name Marinobacterium halophilum sp. nov. is proposed. The type strain is mano11T (=KCTC 12240T=DSM 17586T).