bluuebunny/crossref_metadata_2025 huggingface dataset:
Large-eddy simulation of particle-laden turbulent flows
Authors: BINI M. , JONES W. P.
Published: October 2008

A large-eddy-based methodology for the simulation of turbulent sprays is discussed. The transport equations for the spatially filtered gas phase variables, in which source terms accounting for the droplet effects are added, are solved together with a probabilistic description of the liquid phase. The probabilistic approach for the liquid phase is based on the transport equation for the spatially filtered joint probability density function of the variables required in order to describe the state of the liquid phase. In this equation, unclosed terms representing the filtered Lagrangian rates of change of the variables describing the spray are present. General modelling ideas for subgrid-scale (SGS) effects are proposed. The capabilities of the approach and the validity of the closure models, with particular with respect to the SGS dispersion, are investigated through application to a dilute particle-laden turbulent mixing layer. It is demonstrated that the formulation is able to reproduce very closely the measured properties of both the continuous and dispersed phases. The large-eddy simulation (LES) results are also found to be entirely consistent with the experimentally observed characteristics of droplet–gas turbulence interactions. Consistent with direct numerical simulation (DNS) studies of isotropic turbulence laden with particles where the entire turbulence spectrum is found to be modulated by the presence of particles, the present investigation, which comprises the effects of particle transport upon the large-scale vortical structures of a turbulent shear flow, highlights what appears to be a selective behaviour; few large-scale frequencies gain energy whereas the remaining modes are damped.
A new electrostatic mode in a dusty plasma due to dust charge fluctuation
Authors: MAMUN A. A.
Published: October 2008

A dusty plasma consisting of cold and hot electrons, cold ions, and charge fluctuating isolated cold dust has been considered. It has been shown by a normal mode analysis that in such a dusty plasma there exists a new type of electrostatic perturbation mode due to the charge fluctuation of the isolated dust. The basic features of this new electrostatic perturbation mode, which are different from those of the electron-acoustic waves, have also been analytically identified. The implications of these results in both the space and laboratory dusty plasma conditions are briefly discussed.
Mean Length of Utterance before words and grammar: Longitudinal trends and developmental implications of infant vocalizations
Authors: FAGAN MARY K.
Published: October 2008

This study measured longitudinal change in six parameters of infant utterances (i.e. number of sounds, CV syllables, supraglottal consonants, and repetitions per utterance, temporal duration, and seconds per sound), investigated previously unexplored characteristics of repetition (i.e. number of vowel and CV syllable repetitions per utterance) and analyzed change in vocalizations in relation to age and developmental milestones using multilevel models. Infants (N=18) were videotaped bimonthly during naturalistic and semi-structured activities between 0 ; 3 and the onset of word use (M=11·8 months). Results showed that infant utterances changed in predictable ways both in relation to age and in relation to language milestones (i.e. reduplicated babble onset, word comprehension and word production). Looking at change in relation to the milestones of language development led to new views of babbling, the transition from babbling to first words, and processes that may underlie these transitions.
Instabilities and mixing in stellar radiation zones
Authors: Zahn Jean-Paul
Published: October 2008

The standard model of stellar structure is unable to account for various observational facts, and there is now a large consensus that some ‘extra mixing’ must occur in the radiation zones. The possible causes for such mixing are briefly reviewed. The most efficient among them is probably the shear-turbulence generated by the differential rotation, which itself results from the transport of angular momentum that can be mediated through the large-scale circulation induced by structural adjustments or by the applied torques (stellar wind, accretion, tides). In solar-type stars this angular momentum transport is ensured mainly by internal gravity waves that are excited at the boundary with convection zones. Another cause of mixing manifests itself in the red giant phase, namely the thermohaline instability due to an inversion of the molecular weight gradient. The implementation of these processes in stellar evolution codes is giving rise to a new generation of stellar models, which are in much better agreement with the observational constraints.
Lithium Depletions in Late-type Dwarfs
Authors: Xiong D. R. , Deng L.
Published: October 2008

Using a self-consistant dynamic theory of non-local convection in chemically inhomogeneous stars, the lithium depletion in MS stars of masses 0.725–1.5 M⊙ are calculated. Both of the overshooting and microdiffusion are included in a consistent way. The comparisons of theretical reasults with the observed Li depletions in open clusters show that the general characters of Li depletions can be reproduced by theory. The overshooting mixing and microdiffusion induced by gravitational setting and radiative accelerations may be two main mechanisms of Li depletion.
Comparing the Nucleosynthesis Parameters of s+r Stars and Ba Stars
Authors: Cui Wen-Yuan , Cui Dong-Nuan , Zhang Bo
Published: October 2008

In this paper, we use a parametric model of the asymptotic giant branch (AGB) stars, in which the 13C neutron source is activated in radiative conditions during the interpulse periods, to calculate the nucleosynthesis in 29 very metal-poor double-enhanced stars (i.e. s+r stars) and 26 barium stars (i.e. Ba stars), respectively. Through a statistical analyzing on the corresponding parameters obtained for the above stars, we get the possible conditions which the s+r stars formed in. We find that the value of neutron exposures of most s+r stars is greater than that of Ba stars. In the very metal-poor stars, the Ba stars stars should belong to the binary systems with large initial orbital separation, by comparing the s-process-component coefficient (Cs) values with those of s+r stars. For s+r stars, there is strong correlation between their Cs and Cr (r-process-component coefficient) but no correlation for Ba stars. This strongly confirms the possibility that the s+r stars should form through the accretion-induced collapse (AIC) or type 1.5 supernova mechanism.
The spectral properties of a large sample of low surface brightness disk galaxies
Authors: Liang Y. C. , Zhong G. H. , Deng L. C. , Zhang B.
Published: October 2008

We present the spectral properties of a large sample of nearly face-on low surface brightness (LSB) disk galaxies selected from the SDSS-DR4 main galaxy sample. About 12,282 LSB galaxies have been selected from the photometry database with their B-band central surface brightness μ0(B) ranging from 22 to 24.5 mag arcsec−2. About 7000 of such LSBGs have measured emission lines ([OII]3727, [OIII]5007, Hβ, Hα, [NII]6583) with the S/N ratio greater than 5σ. Their spectral diagnostic diagram of [NII]/Hα vs. [OIII]/Hβ shows that ~89% of them are star-forming galaxies, and ~11% could be classified as AGNs. The relations of μ0(B) vs. 12+log(O/H) and μ0(B) vs. stellar masses M* of these star-forming LSB galaxies show that their O/H and M* increase following the increasing μ0(B). The majority of these LSBGs are on the higher branch of metallicity.
Hydrodynamical Simulations of Turbulent Convection in a Rotating Red Giant Star
Authors: Palacios A. , Brun A. S.
Published: October 2008

We present 3-D hydrodynamical simulations of the extended turbulent convective envelope of a low-mass red giant star. These simulations, computed with the ASH code, aim at understanding the redistribution of angular momentum and heat in extended turbulent convection zones of these giant stars. We focus our study on the effects of turbulence and of the rotation rate on the convective patterns and on the distribution of angular momentum within the inner 50% of the convective envelope of such stars.
Deathzones and exponents: A different approach to incorporating mass loss in stellar evolution calculations
Authors: Willson Lee Anne
Published: October 2008

Observations tend to select mass loss rates near the critical rate, Ṁcrit = M/L. There are two reasons for this. In some situations, such as near the tip of the AGB, the mass loss rate is very sensitive to stellar parameters. In this case, stars with Ṁ ≪ Ṁcrit have dust-free, hard-to-measure mass loss rates while stars with Ṁ ≫ Ṁcrit do not survive very long and thus make up a small fraction of any sample. Selection effects dominate the fitting of empirical formulae; observations of mass loss rates tell us more about which stars are losing mass than about how a star loses mass. In other situations, such as for some of the stars along the RGB, a steady state situation occurs where the loss of mass leads to a decrease in mass loss rate while the evolutionary changes lead to an increase; the result is a steady state with Ṁ = Ṁcrit. To determine the envelope mass and composition at the end of a phase of intensive mass loss requires stellar evolution models capable of responding on a time scale ~ tKH and thus, a new generation of stellar modeling codes.
Thermohaline mixing and fossil magnetic fields in red giant stars
Authors: Charbonnel Corinne , Zahn Jean-Paul
Published: October 2008

We discuss the occurence and consequences of thermohaline mixing in RGB stars, as well as the possible inhibition of this process by a fossil magnetic field in Ap star descendants.
“Hot Helium Flashers” – The Road to Extreme Horizontal Branch Stars
Authors: Yaron O. , Kovetz A. , Prialnik D.
Published: October 2008

Observational and theoretical investigations, performed especially over the last two decades, have strongly attributed the far-UV upturn phenomenon to low-mass, small-envelope, He-burning stars in Extreme Horizontal Branch (EHB) and subsequent evolutionary phases.

Using our new stellar evolution code – a code that follows through complete evolutionary tracks, Pre-MS to cooling WD – without any interruption or intervention, we are able to produce a wide array of EHB stars, lying at bluer (Teff ≥ 20,000 K) and less luminous positions on HRD, and also closely examine their post-HB evolution until the final cooling as White Dwarfs.

HB morphology is a complex multiple parameter problem. Two leading players, which seem to possess the ability to affect considerably positions of HB, are those of: 1.Helium abundance, and 2.mass-loss efficiency on the first giant branch. We focus here on the latter; thus, EHB stars are produced in our calculations by increasing the mass-loss rate on the RGB, to a state where prior to reaching core He flash conditions, only a very small H-rich envelope remains. The core flash takes place at hotter positions on the HRD, sometimes while already descending on the WD cooling curve. We show preliminary results for a range of initial masses (MZAMS = 0.8 − 1.1 M⊙) and for metallicities covering both populations I and II (Z = 0.01 − 0.001). The [M,Z] combinations have been chosen such that the masses would be above and close to typical MS turnoff masses (e.g. the estimation of MTO ≃ 0.85 for NGC 2808), and also so that the ages at HB are of order of 10 ± 5 Gyr.
The age-metallicity relation in the thin disk
Authors: Li Ji , Liang Bo , Fan Weishi
Published: October 2008

With two stellar sample A and B, the age-metallicity relation (AMR) in the Galactic thin disk is investigated. The results show two different AMRs: one is a nearly flat AMR from photometric analysis of sample A, the other is an obvious AMR derived from spectroscoipic analysis of sample B.
The influence of inhomogeneities on hot star wind model predictions
Authors: Krtička J. , Muijres L. , Puls J. , Kubát J. , de Koter A.
Published: October 2008

We study the effect of wind inhomogeneities (clumping) on O star wind model predictions. For this purpose we artificially include clumping into our stationary NLTE wind models. As a result of the inclusion of optically thin clumps the radiative line force is increased compared to corresponding unclumped models, with a similar effect on either the mass-loss rate or the terminal velocity. When the clumps are allowed to be optically thick in continuum, on the other hand, the radiative force and consequently the mass-loss rate decreases alternatively.
Close binary evolution and blue straggler formation
Authors: Lu. P. , Deng L.
Published: October 2008

In order to discuss the contribution of mass transfer in primordial close binaries to the blue straggler population in young clusters, we use Eggleton's stellar evolution code to simulate a grid of case A binary evolutionary models with the initial donor mass 2.0 – 8.0 M⊙ and mass ratio 0.1 – 0.9. The models cover the whole case A binaries that will experience mass transfer between 30.0 Myr to 1.0 Gyr. Based on such detailed models, we present a simulation to compare with the HST observation of young cluster NGC 1831 which can be fit with an isochrone of log(age) = 8.65. The results show very few blue stragglers could be produced by case A binary evolution. There must be some other mechanisms for blue straggler formation in young clusters.
The history of KZ Hya and its unseen companions
Authors: Jiang S. Y.
Published: October 2008

KZ Hya is a short-period high amplitude metal pool population II pulsating variable. Its spectral type is B9-A7 III/IV. Its average effective temperature is 7640K. But its mass is only 0.97 solar mass. From normal stellar evolution and H-R diagram, we can not get such a solar mass star at post main sequence stage with so high effective temperature and so early type spectra. We observe this star since 1984 till now, 23years past. Finally we prove it is inside a binary with at least 2 unseen companions. The most massive companion has mass larger than 0.76 solar mass, mostly may be 0.99 to 3.99 solar mass. That means this companion must be a massive white dwarf. The distance between tow companions is about 10 AU. If the companion is white dwarf, this binary are fairly inside the nebula. This system is very old, older than 7.59 billion years. The nebula should be already diluted to very low density so that we can see the nebula directly. As its spectra type is B9III/VI at some time of maximum light and the visual absolute magnitude is 2.78, about 2 magnitudes higher than our sun. We can image that at the end of AGB stage of the companion, the strong fast winds from hot central core push away the outer atmosphere of KZ Hya. Later KZ Hya absorbed a part of Helium rich material from the companion. This will cause hydrogen content X decrease from 0.75 to about 0.62. Then KZ Hya looks like a hot post main sequence star
A Spectroscopic Study of Barium Stars
Authors: Liu G. Q. , Liang Y. C. , Deng L.
Published: October 2008

We present an analysis of eight barium stars, providing their atmospheric parameters (Teff, log g, [Fe/H], ξt) and chemical abundances, based on the high signal-to-noise ratio and high resolution Echelle spectra. The s-process elements Y, Zr, Ba, La, Eu show obvious overabundance relative to the Sun. And Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Ni show comparable abundances to the Solar ones. The results of theoretical model of wind accretion for binary systems can explain the observed abundance patterns of the neutron capture process elements in these Ba stars, which means that their overabundant heavy-elements could be caused by accreting the ejecta of AGB stars, the progenitors of the present white dwarf companions in the binary systems.
The eclipsing binary IU Per and its intrinsic oscillations
Authors: Zhang X. B.
Published: October 2008

The results of a long-term time-series photometry of the short-period eclipsing binary IU Per are reported. The observation confirms the intrinsic δ Scuti-like pulsation of the star as discovered by previous authors. A photometric solution for the binary system was carried out with the new data. Based on which, the pure oscillation light variations from the mass-accreting primary component were extracted. A Fourier analysis reveals four pulsation modes. Combining with the photometric solution, a preliminary mode identification was given.
Hydrodynamic Processes in Massive Stars
Authors: Meakin Casey A.
Published: October 2008

The hydrodynamic processes operating within stellar interiors are far richer than represented by the best stellar evolution model available. Although it is now widely understood, through astrophysical simulation and relevant terrestrial experiment, that many of the basic assumptions which underlie our treatments of stellar evolution are flawed, we lack a suitable, comprehensive replacement. This is due to a deficiency in our fundamental understanding of the transport and mixing properties of a turbulent, reactive, magnetized plasma; a deficiency in knowledge which stems from the richness and variety of solutions which characterize the inherently non-linear set of governing equations. The exponential increase in availability of computing resources, however, is ushering in a new era of understanding complex hydrodynamic flows; and although this field is still in its formative stages, the sophistication already achieved is leading to a dramatic paradigm shift in how we model astrophysical fluid dynamics. We highlight here some recent results from a series of multi-dimensional stellar interior calculations which are part of a program designed to improve our one-dimensional treatment of massive star evolution and stellar evolution in general.
Analysing the Contributions in Moment Equations of Reynolds Stress Models of Convection with Numerical Simulations
Authors: Kupka F. , Muthsam H. J.
Published: October 2008

We discuss how 3D numerical simulations can be used to analyse the different contributions within dynamical equations of non-local Reynolds stress models of convection.
Two notions of conventions: an experimental analysis
Authors: MILLER LUIS M.
Published: October 2008

This paper aims at analyzing the interaction between both economic and sociological notions of convention. To this end, it starts by distinguishing conceptually between specific convention, i.e. an arbitrary but stable social regularity, and general convention, i.e. a principle of action prescribing how to behave in a certain class of situations. A game theoretical framework to represent the interrelation between both concepts is then introduced. Finally, this relation is studied experimentally. The main results of the experiment are: (1) general conventions have to be commonly known and adopted among subjects in order to work as guides to coordinate on specific conventions; (2) once subjects follow a general convention they are highly consistent with it in a repeated environment; (3) efficiency concerns are focal in the class of games studied in this paper.
Choice, Accountability, and Effortful Processing in Escalation Situations
Authors: Wolff Hans-Georg , Moser Klaus
Published: October 2008

Many studies on escalation of commitment observe only a single decision following negative feedback, although theoretical approaches to escalation behavior depict escalation as a progression over time. The present paper builds on Brockner and Rubin’s (1985 ) “tunnel vision” account that suggests a distinction between early and late stages of the escalation process. We used a dynamic paradigm, observing repeated decisions following negative feedback and manipulated choice and accountability in order to examine effects of justification on the progression of escalation behavior. Furthermore, reading times are used as a measure of effortful processing to investigate the mediating cognitive processes that lead to escalation behavior. Results show that the combination of choice with accountability leads to escalation behavior at later stages of the escalation process and that effortful processing mediates this interaction of choice, accountability, and escalation behavior.
Task Context Effects in Bilingual Nonword Processing
Authors: Lemhöfer Kristin , Radach Ralph
Published: October 2008

To investigate the language-specific or language-integrated nature of bilingual lexical processing in different task contexts, we studied how bilinguals process nonwords that differ in their relative resemblance to the bilinguals’ two languages in different versions of the lexical decision task. Unbalanced German-English bilinguals performed a pure-German, a pure-English, and a mixed lexical decision task on the same set of nonwords that were either very English-like or very German-like. Rejection latencies for these two nonword categories were reversed in the pure-English and pure-German conditions: Nonwords that were more similar to the current target language were rejected more slowly. In the mixed task, reaction times were generally slower, and nonwords resembling the participants’ subdominant language (English) were harder to reject. The results suggest that task context substantially alters the criteria for the word/nonword decision in bilinguals.
Are tropical forests near a high temperature threshold?
Authors: Doughty Christopher E. , Goulden Michael L.
Published: October 2008

We used leaf gas exchange, sap flow, and eddy covariance measurements to investigate whether high temperature substantially limits CO2 uptake at the LBA‐ECO (Large‐scale Biosphere‐Atmosphere) km‐83 tropical forest site in Brazil. Leaf‐level temperature‐photosynthesis curves, and comparisons of whole‐canopy net ecosystem CO2 exchange (NEE) with air temperature, showed that CO2 uptake declined sharply during warm periods. Observations of ambient leaf microclimate showed that leaves oscillate between two states: a cool, dimly lit stage and a hot, brightly illuminated stage where leaf temperatures are often greater than 35°C. The leaf‐level rates of photosynthesis decreased when shaded leaves (∼ambient air temperature and < 500 μmol m−2 s−1) were transferred into a prewarmed, brightly illuminated chamber (35° to 38°C and 1000 μmol m−2 s−1), coincident with increased leaf temperature, increased evaporative demand, and stomatal closure. The rates of whole‐canopy CO2 uptake calculated at 5‐min intervals increased initially at the onset of sunny periods that followed extended cloudy periods, but then decreased as the sunlight continued, leaf temperature and evaporative demand increased, and canopy conductance decreased. The forest at km‐83 appears to be close to a high temperature threshold, above which CO2 uptake drops sharply. This sensitivity results in part from the covariance between leaf temperature and leaf illumination; the brightly illuminated leaves that contribute disproportionately to canopy photosynthesis are warmed to the point that leaf gas exchange is curtailed.
Overview of observations from the RADAGAST experiment in Niamey, Niger: Meteorology and thermodynamic variables
Authors: Slingo A. , Bharmal N. A. , Robinson G. J. , Settle J. J. , Allan R. P. , White H. E. , Lamb P. J. , Lélé M. Issa , Turner D. D. , McFarlane S. , Kassianov E. , Barnard J. , Flynn C. , Miller M.
Published: October 2008

An overview is presented of the meteorological and thermodynamic data obtained during the Radiative Atmospheric Divergence using Atmospheric Radiation Measurement (ARM) Mobile Facility, Geostationary Earth Radiation Budget (GERB) data, and African Monsoon Multidisciplinary Analysis (AMMA) stations (RADAGAST) experiment in Niamey, Niger, in 2006. RADAGAST combined data from the ARM Program Mobile Facility (AMF) at Niamey airport with broadband satellite data from the GERB instrument on Meteosat‐8. The experiment was conducted in collaboration with the AMMA project. The focus in this paper is on the variations through the year of key surface and atmospheric variables. The seasonal advance and retreat of the Intertropical Front and the seasonal changes in near‐surface variables and precipitation in 2006 are discussed and contrasted with the behavior in 2005 and with long‐term averages. Observations from the AMF at Niamey airport are used to document the evolution of near‐surface variables and of the atmosphere above the site. There are large seasonal changes in these variables, from the arid and dusty conditions typical of the dry season to the much moister and more cloudy wet season accompanying the arrival and intensification of the West African monsoon. Back trajectories show the origin of the air sampled at Niamey and profiles for selected case studies from rawinsondes and from a micropulse lidar at the AMF site reveal details of typical atmospheric structures. Radiative fluxes and divergences are discussed in the second part of this overview, and the subsequent papers in this special section explore other aspects of the measurements and of the associated modeling.
Head‐to‐tail fusions of camelid antibodies can be expressed in planta and bind in rumen fluid
Authors: Winichayakul Somrutai , Pernthaner Anton , Scott Richard , Vlaming Ruth , Roberts Nick
Published: October 2008

We have compared the accumulation of recombinant variable heavy‐chain portions [VHH (variable heavy‐chain antibody from camelids)] of camelid antibodies in a variety of subcellular compartments produced in planta. The VHH coding sequences were optimized for expression in thale cress (Arabidopsis thaliana) and placed individually or as fused tandem heterodimers in synthetic plant‐organelle‐targeting cassettes designed to target the protein to either the cytoplasm, ER (endoplasmic reticulum), protein storage vacuole or chloroplast. Accumulation of individual VHHs was only detected in plants transformed with the ER‐targeting cassette, whereas accumulation of the tandem VHHs was detected for all cassettes and was the highest with the ER cassette [0.1–0.7% (w/w) of total soluble proteins]. The ability of the plant‐produced tandem VHH to reduce TNFα (tumour necrosis factor α) cytotoxicity was found to be comparable with previously characterized recombinant VHHs. In vitro antigen binding and functional stability in rumen fluid were determined on both prokaryotically expressed and plant‐expressed tandem VHHs. The plant‐produced VHH did not appear to be any more stable in rumen fluid than other soluble plant proteins; however, it was able to bind equally well to the antigen in the presence or absence of rumen fluid.
Disruption of the crossover helix impairs dihydrofolate reductase activity in the bifunctional enzyme TS–DHFR from Cryptosporidium hominis
Authors: Vargo Melissa A. , Martucci W. Edward , Anderson Karen S.
Published: October 2008

In contrast with most species, including humans, which have monofunctional forms of the folate biosynthetic enzymes TS (thymidylate synthase) and DHFR (dihydrofolate reductase), several pathogenic protozoal parasites, including Cryptosporidium hominis, contain a bifunctional form of the enzymes on a single polypeptide chain having both catalytic activities. The crystal structure of the bifunctional enzyme TS–DHFR C. hominis reveals a dimer with a ‘crossover helix’, a swap domain between DHFR domains, unique in that this helical region from one monomer makes extensive contacts with the DHFR active site of the other monomer. In the present study, we used site-directed mutagenesis to probe the role of this crossover helix in DHFR catalysis. Mutations were made to the crossover helix: an ‘alanine-face’ enzyme in which the residues on the face of the helix close to the DHFR active site of the other subunit were mutated to alanine, a ‘glycine-face’ enzyme in which the same residues were mutated to glycine, and an ‘all-alanine’ helix in which all residues of the helix were mutated to alanine. These mutant enzymes were studied using a rapid transient kinetic approach. The mutations caused a dramatic decrease in the DHFR activity. The DHFR catalytic activity of the alanine-face mutant enzyme was 30 s−1, the glycine-face mutant enzyme was 17 s−1, and the all-alanine helix enzyme was 16 s−1, all substantially impaired from the wild-type DHFR activity of 152 s−1. It is clear that loss of helix interactions results in a marked decrease in DHFR activity, supporting a role for this swap domain in DHFR catalysis. The crossover helix provides a unique structural feature of C. hominis bifunctional TS–DHFR that could be exploited as a target for species-specific non-active site inhibitors.
The structure, methyl rotation reflected in inelastic and quasielastic neutron scattering and vibrational spectra of 1,2,3,5-tetramethoxybenzene and its 2:1 complex with 1,2,4,5-tetracyanobenzene
Authors: Pawlukojć Andrzej , Prager Michael , Dobrowolska Wanda Sawka , Bator Grażyna , Sobczyk Lucjan , Ivanov Alexander , Rols Stéphane , Grech Eugeniusz , Nowicka-Scheibe Joanna , Unruh Tobias
Published: October 2008

X-ray diffraction studies show that molecules of the 1,2,3,5-tetramethoxybenzene (TMOB)2⋅1,2,4,5-tetracyanobenzene complex form ⋯CCDCCDCC⋯ columns with the short distances between molecular planes of C and D molecules equal to 3.186Å. The vibrational spectra recorded by using the inelastic neutron scattering, Raman, IR, and quasielastic neutron scattering (QENS) techniques aided by density functional theory calculations for the isolated molecules and the crystalline state enabled all four inequivalent librational modes, ascribed to the methoxy groups, to be analyzed. A rather good consistency was found between the experimental frequencies and those calculated for the crystal. The consistency was also achieved between the experimental structure of molecules and the theoretically reproduced one. A close similarity of the structures of the TMOB molecule isolated and in the complex is taken as a sign of dominating intramolecular interaction. The QENS spectra contain three Lorentzians of relative intensities of 1:1:2. Thus the two most strongly hindered of the four inequivalent methoxy groups in the crystalline lattice are characterized by rather similar barrier heights in good agreement with the packing analysis.
A bistable divacancylike defect in silicon damage cascades
Authors: Fleming R. M. , Seager C. H. , Lang D. V. , Bielejec E. , Campbell J. M.
Published: October 2008

Two deep level transient spectroscopy (DLTS) electron emission signatures, previously labeled E4 and E5, have been shown to be bistable with respect to minority carrier injection at room temperature. These result from two charge state transitions of the same defect. We have performed DLTS measurements as function of annealing between 350 and 680 K, using minority carrier injection after each annealing stage to make E4 and E5 visible. We show that the E4–E5 pair is associated with defect clusters which dominate after neutron or ion damage with annealing characteristics that closely parallel to those of silicon divacancies found in damage clusters. At annealing temperatures above 500 K, the E4–E5 pair ceases to be bistable and exists after anneals in thermal equilibrium. We show that the stable E4 peak appears to be the same emission signature previously labeled the L center. The transformation of the E4–E5 bistable pair into the stable L center and a stable E5 companion level occurs at the same temperature, where it has been suggested that the divacancy becomes mobile. The similarity of the annealing of the E4–E5 pair to that of the divacancy, the dependence of the density of these defects on degree of clustering, and the insensitivity to common impurities combine to suggest that the E4–E5 pair is associated with primary defects located in the defect cluster and closely related to the familiar divacancy.
Nine theorems on the unification of quantum mechanics and relativity
Authors: Kryukov A.
Published: October 2008

A mathematical framework that unifies the standard formalisms of special relativity and quantum mechanics is proposed. For this a Hilbert space H of functions of four variables x,t furnished with an additional indefinite inner product invariant under Poincaré transformations is introduced. For a class of functions in H that are well localized in the time variable, the usual formalism of nonrelativistic quantum mechanics is derived. In particular, the interference in time for these functions is suppressed; a motion in H becomes the usual Schrödinger evolution with t as a parameter. The relativistic invariance of the construction is proved. The usual theory of relativity on Minkowski space-time is shown to be “isometrically and equivariantly embedded” into H. That is, classical space-time is isometrically embedded into H, Poincaré transformations have unique extensions to isomorphisms of H, and the embedding commutes with Poincaré transformations.
Small-signal gain theory of a nonrelativistic planar magnetron
Authors: Zhou Jing , Chen Chiping
Published: October 2008

A small-signal theory of a nonrelativistic magnetron is developed using a planar model with a thin electron cloud. The theory includes both inertial effects and electromagnetic effects in a Floquet expansion. An analytical dispersion relation of such a planar magnetron is derived, and the growth rate is calculated analytically. The found instability involves the resonance between the electron cloud and the magnetron cavity vacuum slow waves. A good agreement is found between the theory and the self-consistent particle-in-cell MAGIC simulations.
Physical factors controlling the ductility of bulk metallic glasses
Authors: Liu Y. , Wu H. , Liu C. T. , Zhang Z. , Keppens V.
Published: October 2008

In order to identify key physical factor controlling the deformation and fracture behavior of bulk metallic glasses (BMGs), we compiled and analyzed the elastic moduli and compressive ductility for BMGs. In addition, new modulus data were generated in the critical ranges in order to facilitate the analysis. We have found that the intrinsic ductility of BMGs can be correlated with the bulk-to-shear modulus ratio B/G according to Pugh’s [Philos. Mag. 45, 823 (1954)] rule. In some individual BMG systems, for example, Fe based, the relationship seems to be very clear. The physical meaning of this correlation is discussed in terms of atomic bonding and connectivity.
Detection of adsorbed explosive molecules using thermal response of suspended microfabricated bridges
Authors: Yi Dechang , Greve Anders , Hales Jan H. , Senesac Larry R. , Davis Zachary J. , Nicholson Don M. , Boisen Anja , Thundat Thomas
Published: October 2008

Here we present a thermophysical technique that is capable of differentiating vapor phase adsorbed explosives from nonexplosives and is additionally capable of differentiating individual species of common explosive vapors. This technique utilizes pairs of suspended microfabricated silicon bridges that can be heated in a controlled fashion. The differential thermal response of the bridges with and without adsorbed explosive vapor shows unique and reproducible characteristics depending on the nature of the adsorbed explosives. The tunable heating rate method described here is capable of providing unique signals for subnanogram quantities of adsorbed explosives within 50 ms.
Sustained delivery of siRNAs targeting viral infection by cell-degradable multilayered polyelectrolyte films
Authors: Dimitrova Maria , Affolter Christine , Meyer Florent , Nguyen Isabelle , Richard Doriane G. , Schuster Catherine , Bartenschlager Ralf , Voegel Jean-Claude , Ogier Joëlle , Baumert Thomas F.
Published: October 2008

Gene silencing by RNA interference (RNAi) has been shown to represent a recently discovered approach for the treatment of human diseases, including viral infection. A major limitation for the success of therapeutic strategies based on RNAi has been the delivery and shortlasting action of synthetic RNA. Multilayered polyelectrolyte films (MPFs), consisting of alternate layer-by-layer deposition of polycations and polyanions, have been shown to represent an original approach for the efficient delivery of DNA and proteins to target cells. Using hepatitis C virus infection (HCV) as a model, we demonstrate that siRNAs targeting the viral genome are efficiently delivered by MPFs. This delivery method resulted in a marked, dose-dependent, specific, and sustained inhibition of HCV replication and infection in hepatocyte-derived cells. Comparative analysis demonstrated that delivery of siRNAs by MPFs was more sustained and durable than siRNA delivery by standard methods, including electroporation or liposomes. The antiviral effect of siRNA-MPFs was reversed by a hyaluronidase inhibitor, suggesting that active degradation of MPFs by cellular enzymes is required for siRNA delivery. In conclusion, our results demonstrate that cell-degradable MPFs represent an efficient and simple approach for sustained siRNA delivery targeting viral infection. Moreover, this MPF-based delivery system may represent a promising previously undescribed perspective for the use of RNAi as a therapeutic strategy for human diseases.
Identification of a new JNK inhibitor targeting the JNK-JIP interaction site
Authors: Stebbins John L. , De Surya K. , Machleidt Thomas , Becattini Barbara , Vazquez Jesus , Kuntzen Christian , Chen Li-Hsing , Cellitti Jason F. , Riel-Mehan Megan , Emdadi Aras , Solinas Giovanni , Karin Michael , Pellecchia Maurizio
Published: October 2008

JNK is a stress-activated protein kinase that modulates pathways implicated in a variety of disease states. JNK-interacting protein-1 (JIP1) is a scaffolding protein that enhances JNK signaling by creating a proximity effect between JNK and upstream kinases. A minimal peptide region derived from JIP1 is able to inhibit JNK activity both
in vitro
and in cell. We report here a series of small molecules JIP1 mimics that function as substrate competitive inhibitors of JNK. One such compound, BI-78D3, dose-dependently inhibits the phosphorylation of JNK substrates both
in vitro
and
in cell
. In animal studies, BI-78D3 not only blocks JNK dependent Con A-induced liver damage but also restores insulin sensitivity in mouse models of type 2 diabetes. Our findings open the way for the development of protein kinase inhibitors targeting substrate specific docking sites, rather than the highly conserved ATP binding sites. In view of its favorable inhibition profile, selectivity, and ability to function in the cellular milieu and
in vivo
, BI-78D3 represents not only a JNK inhibitor, but also a promising stepping stone toward the development of an innovative class of therapeutics.
Sequential development of synapses in dendritic domains during adult neurogenesis
Authors: Kelsch Wolfgang , Lin Chia-Wei , Lois Carlos
Published: October 2008

During the process of integration into brain circuits, new neurons develop both input and output synapses with their appropriate targets. The vast majority of neurons in the mammalian brain are generated before birth and integrate into immature circuits while these are being assembled. In contrast, adult-generated neurons face an additional challenge as they integrate into a mature, fully functional circuit. Here, we examined how synapses of a single neuronal type, the granule cell in the olfactory bulb, develop during their integration into the immature circuit of the newborn and the fully mature circuit of the adult rat. We used a genetic method to label pre and postsynaptic sites in granule neurons and observed a stereotypical development of synapses in specific dendritic domains. In adult-generated neurons, synapses appeared sequentially in different dendritic domains with glutamatergic input synapses that developed first at the proximal dendritic domain, followed several days later by the development of input-output synapses in the distal domain and additional input synapses in the basal domain. In contrast, for neurons generated in neonatal animals, input and input-output synapses appeared simultaneously in the proximal and distal domains, respectively, followed by the later appearance of input synapses to the basal domain. The sequential formation of synapses in adult-born neurons, with input synapses appearing before output synapses, may represent a cellular mechanism to minimize the disruption caused by the integration of new neurons into a mature circuit in the adult brain.
Annexin A8 Regulates Late Endosome Organization and Function
Authors: Goebeler Verena , Poeter Michaela , Zeuschner Dagmar , Gerke Volker , Rescher Ursula
Published: October 2008

Different classes of endosomes exhibit a characteristic intracellular steady-state distribution governed by interactions with the cytoskeleton. Late endosomes, organelles of the degradative lysosomal route, seem to require associated actin filaments for proper localization and function. We show here that the F-actin and phospholipid binding protein annexin A8 is associated specifically with late endosomes. Altering intracellular annexin A8 levels drastically affected the morphology and intracellular distribution of late endosomes. Trafficking through the degradative pathway was delayed in the absence of annexin A8, resulting in attenuated ligand-induced degradation of the epidermal growth factor receptor and prolonged epidermal growth factor-induced activation of mitogen-activated protein kinase. Depletion of annexin A8 reduced the association of late endosomal membranes with actin filaments. These results indicate that the defective cargo transport through the late endocytic pathway and the imbalanced signaling of activated receptors observed in the absence of annexin A8 results from the disturbed association of late endosomal membranes with the actin network, resulting in impaired actin-based late endosome motility.
Lipid Microdomains in Cell Nucleus
Authors: Cascianelli Giacomo , Villani Maristella , Tosti Marcello , Marini Francesca , Bartoccini Elisa , Viola Magni Mariapia , Albi Elisabetta
Published: October 2008

It is known that nuclear lipids play a role in proliferation, differentiation, and apoptotic process. Cellular nuclei contain high levels of phosphatidylcholine and sphingomyelin, which are partially linked with cholesterol and proteins to form lipid–protein complexes. These lipids are also associated with transcription factors and newly synthesized RNA but, up to date, their organization is still unknown. The aim of the present work was to study if these specific lipid–protein interactions could be nuclear membrane microdomains and to evaluate their possible role. The results obtained demonstrate for the first time the existence of nuclear microdomains characterized by a specific lipid composition similar to that of intranuclear lipid–protein complexes previously described. Nuclear microdomain lipid composition changes during cell proliferation when the content of newly synthesized RNA increases. Because previous data show a correlation between nuclear lipids and transcription process, the role of nuclear microdomains in cellular functions is discussed.
Comment on ‘A congruence index for testing topological similarity between trees’
Authors: Kupczok Anne , von Haeseler Arndt
Published: October 2008

Contact:  anne.kupczok@univie.ac.at
Atrial fibrillation in Mediterranean spotted fever
Authors: Colomba Claudia , Saporito Laura , Colletti Pietro , Mazzola Giovanni , Rubino Raffaella , Pampinella Diego , Titone Lucina
Published: October 2008

Mediterranean spotted fever (MSF) is a tick-borne acute febrile disease caused by Rickettsia conorii and characterized by fever, maculo-papular rash and a black eschar at the site of the tick bite (‘tache noir’). We describe the case of a 58-year-old man affected by MSF who developed atrial fibrillation. The patient presented himself to the hospital after 7 days of fever, malaise and severe headache. Cardiac auscultation revealed a chaotic heart rhythm and an electrocardiogram confirmed atrial fibrillation with a fast ventricular response. Diagnosis of MSF was made after the appearance of a maculo-papular skin rash, and treatment with oral doxycycline was started. An immunofluorescence antibody test confirmed R. conorii infection. The patient recovered after 7 days of treatment. Cardiac arrhythmia is a rare complication of MSF. Inflammation may play a role in the pathogenesis of atrial fibrillation. R. conorii is an intracellular bacterium which could trigger atrial fibrillation. Our patient was previously healthy and had no reported history of cardiac disease. This suggests that heart function should be monitored in MSF patients even in the absence of underlying risk factors.
Modification of the TUBEX typhoid test to detect antibodies directly from haemolytic serum and whole blood
Authors: Tam Frankie C. H. , Leung Danny T. M. , Ma C. H. , Lim Pak-Leong
Published: October 2008

The TUBEX test for typhoid fever detects serum antibodies in a simple and rapid assay system based on the inhibition of binding between two types of reagent particles — magnetic particles coated with an antigen (Salmonella O9 LPS) and coloured indicator particles coated with an anti-O9 mAb. A magnet is used to separate the colour indicator particles bound to the magnetic particles from the unbound indicator particles. Specific colour changes following magnetic separation are indicative of antibodies in the patient's serum; however, because results are interpreted based on changes in the colour red, haemolytic or icteric specimens cannot be used. This study describes a simple modification of the protocol to accommodate such specimens, including whole blood. This involves the addition of a quick and simple washing step after mixing the specimen with the antigen-bound magnetic particles. This modification has the advantage of allowing larger sample volumes to be used, thus enhancing the assay sensitivity, and also enables cases considered to be borderline positive by the original method to be re-assessed.
Closing the diarrhoea diagnostic gap in Indian children by the application of molecular techniques
Authors: Ajjampur S. S. R. , Rajendran P. , Ramani S. , Banerjee I. , Monica B. , Sankaran P. , Rosario V. , Arumugam R. , Sarkar R. , Ward H. , Kang G.
Published: October 2008

A large proportion of diarrhoeal illnesses in children in developing countries are ascribed to an unknown aetiology because the only available methods, such as microscopy and culture, have low sensitivity. This study was aimed at decreasing the diagnostic gap in diarrhoeal disease by the application of molecular techniques. Faecal samples from 158 children with and 99 children without diarrhoea in a hospital in South India were tested for enteric pathogens using conventional diagnostic methods (culture, microscopy and enzyme immunoassays) and molecular methods (six PCR-based assays). The additional use of molecular techniques increased identification to at least one aetiological agent in 76.5 % of diarrhoeal specimens, compared with 40.5 % using conventional methods. Rotavirus (43.3 %), enteropathogenicEscherichia coli(15.8 %), norovirus (15.8 %) andCryptosporidiumspp. (15.2 %) are currently the most common causes of diarrhoea in hospitalized children in Vellore, in contrast to a study conducted two decades earlier in the same hospital, where bacterial pathogens such asShigellaspp.,Campylobacterspp. and enterotoxigenicE. coliwere more prevalent. Molecular techniques significantly increased the detection rates of pathogens in children with diarrhoea, but a more intensive study, testing for a wider range of infectious agents and including more information on non-infectious causes of diarrhoea, is required to close the diagnostic gap in diarrhoeal disease.