4,621 research outputs found
On invariance of plurigenera for foliations on surfaces
We show that if is a family of foliations with reduced singularities on a smooth family of surfaces, then invariance of plurigenera holds for sufficiently large . On the other hand, we provide examples on which the result fails, for small values of
The Evaluation of When English Rings a Bell (Revised Edition): Teachers' Perspectives
This study was done to find out the teachers` opinions regarding the coursebook, When English Rings A Bell (revised edition), in terms of (1) the coursebook`s language content, (2) the presentation of English skills in the coursebook, and (3) the coursebook`s topic, subject content, and social values. The data of this study was the teachers` written and/or oral answers of the questions used as the evaluation guidelines as proposed by Cunningsworth (1995). The teachers stated that (a) the topics, (b) subjects content, and (c) social and cultural values presented in the coursebook were appropriate to the Indonesian people`s way of life by not differentiating in gender. In addition, although the book provided practices for all English skills, the book should include additional material to support them, for instance, recorded material on a cassette for listening practices. The book did not also include all language contents as proposed by Cuningsworth (1995)
Electronic, dynamical and superconducting properties of CaBeSi
We report first-principles calculations on the normal and superconducting
state of CaBe(x)Si(2-x) (x=1), in the framework of density functional theory
for superconductors (SCDFT). CaBeSi is isostructural and isoelectronic to MgB2
and this makes possible a direct comparison of the electronic and vibrational
properties and the electron-phonon interaction of the two materials. Despite
the many similarities with MgB2 (e.g. sigma bands at the Fermi level and a
larger Fermi surface nesting), according to our calculations CaBeSi has a very
low critical temperature (Tc ~ 0.4 K, consistent with the experiment). CaBeSi
exhibits a complex gap structure, with three gaps at Fermi level: besides the
two sigma and pi gaps, present also in MgB2, the appearance of a third gap is
related to the anisotropy of the Coulomb repulsion, acting in different way on
the bonding and antibonding electronic pi states.Comment: 6 pages, 5 figure
Deep Learning for Galaxy Mergers in the Galaxy Main Sequence
Starburst galaxies are often found to be the result of galaxy mergers. As a
result, galaxy mergers are often believed to lie above the galaxy main
sequence: the tight correlation between stellar mass and star formation rate.
Here, we aim to test this claim. Deep learning techniques are applied to images
from the Sloan Digital Sky Survey to provide visual-like classifications for
over 340 000 objects between redshifts of 0.005 and 0.1. The aim of this
classification is to split the galaxy population into merger and non-merger
systems and we are currently achieving an accuracy of 91.5%. Stellar masses and
star formation rates are also estimated using panchromatic data for the entire
galaxy population. With these preliminary data, the mergers are placed onto the
full galaxy main sequence, where we find that merging systems lie across the
entire star formation rate - stellar mass plane.Comment: 4 pages, 1 figure. For Proceedings IAU Symposium No. 34
Emergence of quasiparticle Bloch states in artificial crystals crafted atom-by-atom
The interaction of electrons with a periodic potential of atoms in
crystalline solids gives rise to band structure. The band structure of existing
materials can be measured by photoemission spectroscopy and accurately
understood in terms of the tight-binding model, however not many experimental
approaches exist that allow to tailor artificial crystal lattices using a
bottom-up approach. The ability to engineer and study atomically crafted
designer materials by scanning tunnelling microscopy and spectroscopy (STM/STS)
helps to understand the emergence of material properties. Here, we use atom
manipulation of individual vacancies in a chlorine monolayer on Cu(100) to
construct one- and two-dimensional structures of various densities and sizes.
Local STS measurements reveal the emergence of quasiparticle bands, evidenced
by standing Bloch waves, with tuneable dispersion. The experimental data are
understood in terms of a tight-binding model combined with an additional
broadening term that allows an estimation of the coupling to the underlying
substrate.Comment: 7 figures, 12 pages, main text and supplementary materia
The Horn, Kink and Step, Dale: from few GeV to few TeV
Rich experimental data have been collected in heavy-ion collisions at high
energies to study the properties of strongly interacting matter. As the theory
of strong interactions, QCD, predicts asymptotic freedom, the created matter at
sufficiently high temperature and density will be dominated by a state of
quasi-free quarks and gluons referred to as the Quark-Qluon Plasma (QGP).
Experimental signals for the onset of the QGP creation (the onset of the
deconfinement) have been predicted within the statistical model for the early
stage of nucleus-nucleus collisions. In this model the existence of two
different phases is assumed: confined mater and the QGP, as well as a first
order phase transition between them. Until recently, these predictions were
confirmed only by the NA49 experiment at the CERN SPS. In this report recent
results from STAR at RHIC/BNL and from ALICE at LHC/CERN, related to the onset
of deconfinement, will be compared to published results from NA49
Hierarchical fragmentation and differential star formation in the Galactic "Snake": infrared dark cloud G11.11-0.12
We present Submillimeter Array (SMA) 0.88 and 1.3 mm broad band
observations, and the Jansky Very Large Array (VLA) observations in
up to , and maser lines toward
the two most massive molecular clumps in infrared dark cloud (IRDC)
G11.11-0.12. Sensitive high-resolution images reveal hierarchical fragmentation
in dense molecular gas from the pc clump scale down to pc
condensation scale. At each scale, the mass of the fragments is orders of
magnitude larger than the Jeans mass. This is common to all four IRDC clumps we
studied, suggesting that turbulence plays an important role in the early stages
of clustered star formation. Masers, shock heated gas, and outflows
indicate intense ongoing star formation in some cores while no such signatures
are found in others. Furthermore, chemical differentiation may reflect the
difference in evolutionary stages among these star formation seeds. We find
ortho/para ratios of , , and
associated with three outflows, and the ratio tends to increase along the
outflows downstream. Our combined SMA and VLA observations of several IRDC
clumps present the most in depth view so far of the early stages prior to the
hot core phase, revealing snapshots of physical and chemical properties at
various stages along an apparent evolutionary sequence.Comment: 21 pages, 11 figures, 8 tables, accepted to MNRAS; this version
includes minor typo corrections from proo
Detection of interstellar H_2D^+ emission
We report the detection of the 1_{10}-1_{11} ground state transition of
ortho-H_2D^+ at 372.421 GHz in emission from the young stellar object NGC 1333
IRAS 4A. Detailed excitation models with a power-law temperature and density
structure yield a beam-averaged H_2D^+ abundance of 3 x 10^{-12} with an
uncertainty of a factor of two. The line was not detected toward W 33A, GL
2591, and NGC 2264 IRS, in the latter source at a level which is 3-8 times
lower than previous observations. The H_2D^+ data provide direct evidence in
support of low-temperature chemical models in which H_2D^+ is enhanced by the
reaction of H_3^+ and HD. The H_2D^+ enhancement toward NGC 1333 IRAS 4A is
also reflected in the high DCO^+/HCO^+ abundance ratio. Simultaneous
observations of the N_2H^+ 4-3 line show that its abundance is about 50-100
times lower in NGC 1333 IRAS 4A than in the other sources, suggesting
significant depletion of N_2. The N_2H^+ data provide independent lower limits
on the H_3^+ abundance which are consistent with the abundances derived from
H_2D^+. The corresponding limits on the H_3^+$ column density agree with recent
near-infrared absorption measurements of H_3^+ toward W 33A and GL 2591.Comment: Standard AAS LaTeX format (15 pages + 2 figures
Probing the QGP Phase Boundary with Thermal Properties of Mesons
A novel attempt has been made to probe the QCD phase boundary by using the
experimental data for transverse momenta of {\phi} mesons produced in nuclear
collisions at AGS, SPS and RHIC energies. The data are confronted with simple
thermodynamic expectations and lattice QCD results. The experimental data
indicate a first-order phase transition, with a mixed phase stretching the
energy density between \sim1 and 3.2 GeV/fm3 corresponding to SPS energies.Comment: 8-pages, 3-figs, Replaced with the published versio
Expression analysis of HLA-E and NKG2A and NKG2C receptors points at a role for natural killer function in ankylosing spondylitis
Background. Ankylosing Spondylitis (AS) is a complex chronic inflammatory disease strongly associated with the majority of HLA-B27 alleles. HLA-E are non-classical MHC class I molecules that specifically interact with the natural killer receptors NKG2A (inhibitory) and NKG2C (activating), and have been recently proposed to be involved in AS pathogenesis. Objectives: To analyze the expression of HLA-E and the CD94/NKG2 pair of receptors in HLA-B27 positive AS patients and healthy controls (HC) bearing the AS-associated, B*2705 and the non-AS-associated, B*2709 allele. Methods: The level of surface expression of HLA-E molecules on CD14 positive peripheral blood mononuclear cell was evaluated in 21 HLA-B*2705 patients with AS, 12 HLA-B*2705 HC, 12 HLA-B*2709 HC and 6 HLA-B27 negative HC, using the monoclonal antibody MEM-E/08 by quantitative cytofluorimetric analysis. The percentage and density of expression of HLA-E ligands NKG2A and NKG2C were also measured on CD3-CD56+ NK cells. Results. HLA-E expression in CD14 positive cells was significantly higher in AS patients (587.0 IQR 424-830) compared to B*2705 HC (389 IQR 251.3-440.5, p=0.0007), B*2709 HC (294.5 IQR 209.5-422, p=0.0004) and HLA-B27 negative HC (380 IQR 197.3-515.0, p=0.01). A higher number of NK cells expressing NKG2A compared to NKG2C was found in all cohort analysed as well as a higher cell surface density. Conclusion: The higher surface level of HLA-E molecules in AS patients compared to HC, concurrently with a prevalent expression of NKG2A, suggests that the crosstalk between these two molecules might play a role in AS pathogenesis accounting for the previously reported association between HLA-E and AS
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