8,800 research outputs found
-optimal saturated designs: a simulation study
In this work we focus on saturated -optimal designs. Using recent results,
we identify -optimal designs with the solutions of an optimization problem
with linear constraints. We introduce new objective functions based on the
geometric structure of the design and we compare them with the classical
-efficiency criterion. We perform a simulation study. In all the test cases
we observe that designs with high values of -efficiency have also high
values of the new objective functions.Comment: 8 pages. Preliminary version submitted to the 7th IWS Proceeding
High-Resolution Spectroscopy from 3050 to 10000 A of the HDF-S QSO J2233-606 with UVES at the ESO VLT
We report on high-resolution observations () of the Hubble
Deep Field South QSO J2233-606 obtained with the VLT UV-Visual Echelle
Spectrograph (UVES). We present spectral data for the wavelength region \AA. The ratio of the final spectrum is about 50 per
resolution element at 4000 \AA, 90 at 5000 \AA, 80 at 6000 \AA, 40 at 8000 \AA.
Redshifts, column densities and Doppler widths of the absorption features have
been determined with Voigt-profile fitting. A total of 621 lines have been
measured. In particular 270 Ly-alpha lines, 41 Ly-beta and 24 systems
containing metal lines have been identified. Together with other data in the
literature, the present spectrum confirms that the evolution of the number
density of Ly-alpha lines with \huno has an upturn at .Comment: 34 pages Latex, with 3 PostScript figures. Astronomical Journal, in
press. A few revised upper limit
Phonon Properties of Knbo3 and Ktao3 from First-Principles Calculations
The frequencies of transverse-optical phonons in KNbO and
KTaO are calculated in the frozen-phonon scheme making use of the
full-potential linearized muffin-tin orbital method. The calculated frequencies
in the cubic phase of KNbO and in the tetragonal ferroelectric phase are in
good agreement with experimental data. For KTaO, the effect of lattice
volume was found to be substantial on the frequency of the soft mode, but
rather small on the relative displacement patterns of atoms in all three modes
of the symmetry. The TO frequencies in KTaO are found to be of the
order of, but somehow higher than, the corresponding frequencies in cubic
KNbO.Comment: 8 pages + 1 LaTeX figure, Revtex 3.0, SISSA-CM-94-00
New distinguished classes of spectral spaces: a survey
In the present survey paper, we present several new classes of Hochster's
spectral spaces "occurring in nature", actually in multiplicative ideal theory,
and not linked to or realized in an explicit way by prime spectra of rings. The
general setting is the space of the semistar operations (of finite type),
endowed with a Zariski-like topology, which turns out to be a natural
topological extension of the space of the overrings of an integral domain,
endowed with a topology introduced by Zariski. One of the key tool is a recent
characterization of spectral spaces, based on the ultrafilter topology, given
in a paper by C. Finocchiaro in Comm. Algebra 2014. Several applications are
also discussed
Twist1 Is a TNF-Inducible Inhibitor of Clock Mediated Activation of Period Genes.
BACKGROUND: Activation of the immune system affects the circadian clock. Tumor necrosis factor (TNF) and Interleukin (IL)-1β inhibit the expression of clock genes including Period (Per) genes and the PAR-bZip clock-controlled gene D-site albumin promoter-binding protein (Dbp). These effects are due to cytokine-induced interference of E-box mediated transcription of clock genes. In the present study we have assessed the two E-box binding transcriptional regulators Twist1 and Twist2 for their role in cytokine induced inhibition of clock genes.
METHODS: The expression of the clock genes Per1, Per2, Per3 and of Dbp was assessed in NIH-3T3 mouse fibroblasts and the mouse hippocampal neuronal cell line HT22. Cells were treated for 4h with TNF and IL-1β. The functional role of Twist1 and Twist2 was assessed by siRNAs against the Twist genes and by overexpression of TWIST proteins. In luciferase (luc) assays NIH-3T3 cells were transfected with reporter gene constructs, which contain a 3xPer1 E-box or a Dbp E-box. Quantitative chromatin immunoprecipitation (ChIP) was performed using antibodies to TWIST1 and CLOCK, and the E-box consensus sequences of Dbp (CATGTG) and Per1 E-box (CACGTG).
RESULTS: We report here that siRNA against Twist1 protects NIH-3T3 cells and HT22 cells from down-regulation of Period and Dbp by TNF and IL-1β. Overexpression of Twist1, but not of Twist2, mimics the effect of the cytokines. TNF down-regulates the activation of Per1-3xE-box-luc, the effect being prevented by siRNA against Twist1. Overexpression of Twist1, but not of Twist2, inhibits Per1-3xE-box-luc or Dbp-E-Box-luc activity. ChIP experiments show TWIST1 induction by TNF to compete with CLOCK binding to the E-box of Period genes and Dbp.
CONCLUSION: Twist1 plays a pivotal role in the TNF mediated suppression of E-box dependent transactivation of Period genes and Dbp. Thereby Twist1 may provide a link between the immune system and the circadian timing system
UV slope of z3 bright () Lyman-break galaxies in the COSMOS field
We analyse a unique sample of 517 bright () LBGs at redshift
z3 in order to characterise the distribution of their UV slopes
and infer their dust extinction under standard assumptions. We exploited
multi-band observations over 750 arcmin of the COSMOS field that were
acquired with three different ground-based facilities: the Large Binocular
Camera (LBC) on the Large Binocular Telescope (LBT), the Suprime-Cam on the
SUBARU telescope, and the VIRCAM on the VISTA telescope (ULTRAVISTA DR2). Our
multi-band photometric catalogue is based on a new method that is designed to
maximise the signal-to-noise ratio in the estimate of accurate galaxy colours
from images with different point spread functions (PSF). We adopted an improved
selection criterion based on deep Y-band data to isolate a sample of galaxies
at to minimise selection biases. We measured the UV slopes ()
of the objects in our sample and then recovered the intrinsic probability
density function of values (PDF()), taking into account the
effect of observational uncertainties through detailed simulations. The
galaxies in our sample are characterised by mildly red UV slopes with
throughout the enitre luminosity range that is probed by
our data (). The resulting dust-corrected
star formation rate density (SFRD) is , corresponding to a contribution of about 25% to the
total SFRD at z3 under standard assumptions. Ultra-bright LBGs at match the known trends, with UV slopes being redder at decreasing redshifts,
and brighter galaxies being more highly dust extinct and more frequently
star-forming than fainter galaxies. [abridged]Comment: Matched to journal version. 11 pages, 13 figures, Astronomy &
Astrophysics in pres
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