Spin-rotor Interpretation of Identical Bands and Quantized Alignment in Superdeformed A ≈\approx 190 Nuclei

The ``identical'' bands in superdeformed mercury, thallium, and lead nuclei are interpreted as examples of orbital angular momentum rotors with the weak spin-orbit coupling of pseudo-$SU(3)$ symmetries and supersymmetries.Comment: 15 pages, revtex 3.0, 7 figures available upon request from [email protected]

High-contrast spectroscopy of SCR J1845-6357 B

Spectral characterization of sub-stellar companions is essential to understand their composition and formation processes. However, the large contrast ratio of the brightness of each object to that of its parent star limits our ability to extract a clean spectrum, free from any significant contribution from the star. During the development of the long slit spectroscopy (LSS) mode of IRDIS, the dual-band imager and spectrograph of SPHERE, we proposed a data analysis method to estimate and remove the contributions of the stellar spectrum. This method has never been tested on real data because of the lack of instrumentation capable of combining adaptive optics (AO), coronagraphy, and LSS. Nonetheless, a similar attenuation of the star can be obtained using a particular observing configuration. Test data were acquired using the AO-assisted spectrograph VLT/NACO. We obtained new J- and H-band spectra of SCR J1845-6357 B, a T6 companion to a nearby (3.85\pm0.02 pc) M8 star. This system is a well-suited benchmark as it is relatively wide (~1.0") with a modest contrast ratio (~4 mag), and a previously published JHK spectrum is available for reference. We demonstrate that (1) our method is efficient at estimating and removing the stellar contribution, (2) it allows to properly recover the spectral shape of the companion, and (3) it is essential to obtain an unbiased estimation of physical parameters. We also show that the slit configuration associated with this method allows us to use long exposure times with high throughput producing high signal-to-noise ratio data. However, the signal of the companion gets over-subtracted, particularly in our J-band data, compelling us to use a fake companion spectrum to estimate and compensate for the loss of flux. Finally, we report a new astrometric measurement of the position of the companion (sep = 0.817", PA = 227.92 deg).Comment: 11 pages, 8 figures, 4 tables. Accepted for publication in A&

Microbial and metabolic succession on common building materials under high humidity conditions.

Despite considerable efforts to characterize the microbial ecology of the built environment, the metabolic mechanisms underpinning microbial colonization and successional dynamics remain unclear, particularly at high moisture conditions. Here, we applied bacterial/viral particle counting, qPCR, amplicon sequencing of the genes encoding 16S and ITS rRNA, and metabolomics to longitudinally characterize the ecological dynamics of four common building materials maintained at high humidity. We varied the natural inoculum provided to each material and wet half of the samples to simulate a potable water leak. Wetted materials had higher growth rates and lower alpha diversity compared to non-wetted materials, and wetting described the majority of the variance in bacterial, fungal, and metabolite structure. Inoculation location was weakly associated with bacterial and fungal beta diversity. Material type influenced bacterial and viral particle abundance and bacterial and metabolic (but not fungal) diversity. Metabolites indicative of microbial activity were identified, and they too differed by material

Superdeformation in 198^{198}Po

The $^{174}$Yb($^{29}$Si,5n) reaction at 148 MeV with thin targets was used to populate high-angular momentum states in $^{198}$Po. Resulting $\gamma$ rays were observed with Gammasphere. A weakly-populated superdeformed band of 10 $\gamma$-ray transitions was found and has been assigned to $^{198}$Po. This is the first observation of a SD band in the $A \approx 190$ region in a nucleus with $Z > 83$. The ${\cal J}^{(2)}$ of the new band is very similar to those of the yrast SD bands in $^{194}$Hg and $^{196}$Pb. The intensity profile suggests that this band is populated through states close to where the SD band crosses the yrast line and the angular momentum at which the fission process dominates.Comment: 10 pages, revtex, 2 figs. available on request, submitted to Phys. Rev. C. (Rapid Communications

T cell receptor Vbeta gene usage in Thai children with dengue virus infection

T lymphocyte activation during dengue is thought to contribute to the pathogenesis of dengue hemorrhagic fever (DHF). We examined the T cell receptor Vbeta gene usage by a reverse transcriptase-polymerase chain reaction assay during infection and after recovery in 13 children with DHF and 13 children with dengue fever (DF). There was no deletion of specific Vbeta gene families. We detected significant expansions in usage of single Vbeta families in six subjects with DHF and three subjects with DF over the course of infection, but these did not show an association with clinical diagnosis, viral serotype, or HLA alleles. Differences in Vbeta gene usage between subjects with DHF and subjects with DF were of borderline significance. These data suggest that the differences in T cell activation in DHF and DF are quantitative rather than qualitative and that T cells are activated by conventional antigen(s) and not a viral superantigen

The metallicity gradient of M 33: chemical abundances of HII regions

We present spectroscopic observations of a sample of 72 emission-line objects, including mainly HII regions, in the spiral galaxy M 33. Spectra were obtained with the multi-object, wide field spectrograph AF2/WYFFOS at the 4.2m WHT telescope. Line intensities, extinction, and electron density were determined for the whole sample of objects. The aim of the present work was to derive chemical and physical parameters of a set of HII regions, and from them the metallicity gradient. Electron temperatures and chemical abundances were derived for the 14 HII regions where both [OII] and [OIII] emission line fluxes were measured, including the electron temperature sensitive emission line [OIII] 436.3 nm and in a few cases [NII] 575.5 nm. The ionization correction factor (ICF) method was used to derive the total chemical abundances. The presence of abundance gradients was inferred from the radial behaviour of several emission-line ratios, and accurately measured from chemical abundances directly derived in 14 HII regions. The oxygen abundances of our HII regions, located in the radial region from ~2 to ~7.2 kpc, gave an oxygen gradient -0.054+/-0.011 dex/kpc The overall oxygen gradient for M 33 obtained using ours and previous oxygen determinations in a large number of HII regions with direct electron temperature determination as well as abundance in young stars presented a two slope shape: -0.19 dex/kpc for the central regions (R<3kpc), and -0.038dex/kpc for the outer regions (R>=3kpc).Comment: 16 pages, 14 figures, A&A accepted 10/05/200

Cross-Reactivity and Expansion of Dengue-Specific T cells During Acute Primary and Secondary Infections in Humans

Serotype-cross-reactive memory T cells responding to secondary dengue virus (DENV) infection are thought to contribute to disease. However, epitope-specific T cell responses have not been thoroughly compared between subjects with primary versus secondary DENV infection. We studied CD8+ T cells specific for the HLA-A*1101-restricted NS3133 epitope in a cohort of A11+ DENV-infected patients throughout acute illness and convalescence. We compared the expansion, serotype-cross-reactivity, and activation of these cells in PBMC from patients experiencing primary or secondary infection and mild or severe disease by flow cytometry. Our results show expansion and activation of DENV-specific CD8+ T cells during acute infection, which are predominantly serotype-cross-reactive regardless of DENV infection history. These data confirm marked T cell activation and serotype-cross-reactivity during the febrile phase of dengue; however, A11-NS3133-specific responses did not correlate with prior antigenic exposure or current disease severity

Galactic chemical abundance evolution in the solar neighborhood up to the Iron peak

We have developed a detailed standard chemical evolution model to study the evolution of all the chemical elements up to the iron peak in the solar vicinity. We consider that the Galaxy was formed through two episodes of exponentially decreasing infall, out of extragalactic gas. In a first infall episode, with a duration of $\sim$ 1 Gyr, the halo and the thick disk were assembled out of primordial gas, while the thin disk formed in a second episode of infall of slightly enriched extragalactic gas, with much longer timescale. The model nicely reproduces the main observational constraints of the solar neighborhood, and the calculated elemental abundances at the time of the solar birth are in excellent agreement with the solar abundances. By the inclusion of metallicity dependent yields for the whole range of stellar masses we follow the evolution of 76 isotopes of all the chemical elements between hydrogen and zinc. Those results are confronted with a large and recent body of observational data, and we discuss in detail the implications for stellar nucleosynthesis.Comment: 19 pages, 14 figures, submitted to A&

15th Annual Environmental Law Institute

Materials from the 15th Annual Environmental Law Institute held by UK/CLE in March 1999