The site conditions of the Guo Shou Jing Telescope

The weather at Xinglong Observing Station, where the Guo Shou Jing Telescope (GSJT) is located, is strongly affected by the monsoon climate in north-east China. The LAMOST survey strategy is constrained by these weather patterns. In this paper, we present a statistics on observing hours from 2004 to 2007, and the sky brightness, seeing, and sky transparency from 1995 to 2011 at the site. We investigate effects of the site conditions on the survey plan. Operable hours each month shows strong correlation with season: on average there are 8 operable hours per night available in December, but only 1-2 hours in July and August. The seeing and the sky transparency also vary with seasons. Although the seeing is worse in windy winters, and the atmospheric extinction is worse in the spring and summer, the site is adequate for the proposed scientific program of LAMOST survey. With a Monte Carlo simulation using historical data on the site condition, we find that the available observation hours constrain the survey footprint from 22h to 16h in right ascension; the sky brightness allows LAMOST to obtain the limit magnitude of V = 19.5mag with S/N = 10.Comment: 10 pages, 8 figures, accepted for publication in RA

Salmonella paratyphi C: Genetic Divergence from Salmonella choleraesuis and Pathogenic Convergence with Salmonella typhi

BACKGROUND: Although over 1400 Salmonella serovars cause usually self-limited gastroenteritis in humans, a few, e.g., Salmonella typhi and S. paratyphi C, cause typhoid, a potentially fatal systemic infection. It is not known whether the typhoid agents have evolved from a common ancestor (by divergent processes) or acquired similar pathogenic traits independently (by convergent processes). Comparison of different typhoid agents with non-typhoidal Salmonella lineages will provide excellent models for studies on how similar pathogens might have evolved. METHODOLOGIES/PRINCIPAL FINDINGS: We sequenced a strain of S. paratyphi C, RKS4594, and compared it with previously sequenced Salmonella strains. RKS4594 contains a chromosome of 4,833,080 bp and a plasmid of 55,414 bp. We predicted 4,640 intact coding sequences (4,578 in the chromosome and 62 in the plasmid) and 152 pseudogenes (149 in the chromosome and 3 in the plasmid). RKS4594 shares as many as 4346 of the 4,640 genes with a strain of S. choleraesuis, which is primarily a swine pathogen, but only 4008 genes with another human-adapted typhoid agent, S. typhi. Comparison of 3691 genes shared by all six sequenced Salmonella strains placed S. paratyphi C and S. choleraesuis together at one end, and S. typhi at the opposite end, of the phylogenetic tree, demonstrating separate ancestries of the human-adapted typhoid agents. S. paratyphi C seemed to have suffered enormous selection pressures during its adaptation to man as suggested by the differential nucleotide substitutions and different sets of pseudogenes, between S. paratyphi C and S. choleraesuis. CONCLUSIONS: S. paratyphi C does not share a common ancestor with other human-adapted typhoid agents, supporting the convergent evolution model of the typhoid agents. S. paratyphi C has diverged from a common ancestor with S. choleraesuis by accumulating genomic novelty during adaptation to man

Impaired Structural Connectivity of Socio-Emotional Circuits in Autism Spectrum Disorders: A Diffusion Tensor Imaging Study

Abnormal white matter development may disrupt integration within neural circuits, causing particular impairments in higher-order behaviours. In autism spectrum disorders (ASDs), white matter alterations may contribute to characteristic deficits in complex socio-emotional and communication domains. Here, we used diffusion tensor imaging (DTI) and tract based spatial statistics (TBSS) to evaluate white matter microstructure in ASD.DTI scans were acquired for 19 children and adolescents with ASD (∼8-18 years; mean 12.4±3.1) and 16 age and IQ matched controls (∼8-18 years; mean 12.3±3.6) on a 3T MRI system. DTI values for fractional anisotropy, mean diffusivity, radial diffusivity and axial diffusivity, were measured. Age by group interactions for global and voxel-wise white matter indices were examined. Voxel-wise analyses comparing ASD with controls in: (i) the full cohort (ii), children only (≤12 yrs.), and (iii) adolescents only (>12 yrs.) were performed, followed by tract-specific comparisons. Significant age-by-group interactions on global DTI indices were found for all three diffusivity measures, but not for fractional anisotropy. Voxel-wise analyses revealed prominent diffusion measure differences in ASD children but not adolescents, when compared to healthy controls. Widespread increases in mean and radial diffusivity in ASD children were prominent in frontal white matter voxels. Follow-up tract-specific analyses highlighted disruption to pathways integrating frontal, temporal, and occipital structures involved in socio-emotional processing.Our findings highlight disruption of neural circuitry in ASD, particularly in those white matter tracts that integrate the complex socio-emotional processing that is impaired in this disorder

Interactions of moving charged particles with triple-walled carbon nanotubes

We study plasmon excitations and channeling trajectories of charged particles in triple-walled carbon nanotubes (TWNTs) based on a semi-classical kinetic model combined with the Molecular Dynamics method. Numerical results show that the outer and inner tubes of a TWNT exert strong influence on the peak structures of the self-energy (or the image potential) and the stopping power curves for the channeling ion, resulting in one or two narrow peaks in the low speed region. In addition, the radial dependencies of the total potential, which includes the image potential due to dynamic polarization of the electron gas in nanotubes and a reactive empirical bond order potential for atomic interactions, are compared for single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs) and TWNTs. By comparing the ion channeling trajectories in those types of nanotubes, we conclude that the variation of the total energy of ions with their channeling distance along the nanotube axis is related to the types of channeling trajectories, exhibiting smooth helical shapes in TWNTs and a succession of sharp reflections off the wall in SWNTs and DWNTs