488 research outputs found
Validation by Measurements of a IC Modeling Approach for SiP Applications
The growing importance of signal integrity (SI) analysis in integrated circuits (ICs), revealed by modern systemin-package methods, is demanding for new models for the IC sub-systems which are both accurate, efficient and extractable by simple measurement procedures. This paper presents the contribution for the establishment of an integrated IC modeling approach whose performance is assessed by direct comparison with the signals measured in laboratory of two distinct memory IC devices. Based on the identification of the main blocks of a typical IC device, the modeling approach consists of a network of system-level sub-models, some of which with already demonstrated accuracy, which simulated the IC interfacing behavior. Emphasis is given to the procedures that were developed to validate by means of laboratory measurements (and not by comparison with circuit-level simulations) the model performance, which is a novel and important aspect that should be considered in the design of IC models that are useful for SI analysi
Xylella fastidiosa comparative genomic database is an information resource to explore the annotation, genomic features, and biology of different strains
The Xylella fastidiosa comparative genomic database is a scientific resource with the aim to provide a user-friendly interface for accessing high-quality manually curated genomic annotation and comparative sequence analysis, as well as for identifying and mapping prophage-like elements, a marked feature of Xylella genomes. Here we describe a database and tools for exploring the biology of this important plant pathogen. The hallmarks of this database are the high quality genomic annotation, the functional and comparative genomic analysis and the identification and mapping of prophage-like elements. It is available from web site http://www.xylella.lncc.br
De Sitter Gravity and Liouville Theory
We show that the spectrum of conical defects in three-dimensional de Sitter
space is in one-to-one correspondence with the spectrum of vertex operators in
Liouville conformal field theory. The classical conformal dimensions of vertex
operators are equal to the masses of the classical point particles in dS_3 that
cause the conical defect. The quantum dimensions instead are shown to coincide
with the mass of the Kerr-dS_3 solution computed with the Brown-York stress
tensor. Therefore classical de Sitter gravity encodes the quantum properties of
Liouville theory. The equality of the gravitational and the Liouville stress
tensor provides a further check of this correspondence. The Seiberg bound for
vertex operators translates on the bulk side into an upper mass bound for
classical point particles. Bulk solutions with cosmological event horizons
correspond to microscopic Liouville states, whereas those without horizons
correspond to macroscopic (normalizable) states. We also comment on recent
criticism by Dyson, Lindesay and Susskind, and point out that the
contradictions found by these authors may be resolved if the dual CFT is not
able to capture the thermal nature of de Sitter space. Indeed we find that on
the CFT side, de Sitter entropy is merely Liouville momentum, and thus has no
statistical interpretation in this approach.Comment: 22 pages, LateX2e; added references for section 1 and section 2;
corrected typos; improved discussion in section
Prospects for asteroseismology
The observational basis for asteroseismology is being dramatically
strengthened, through more than two years of data from the CoRoT satellite, the
flood of data coming from the Kepler mission and, in the slightly longer term,
from dedicated ground-based facilities. Our ability to utilize these data
depends on further development of techniques for basic data analysis, as well
as on an improved understanding of the relation between the observed
frequencies and the underlying properties of the stars. Also, stellar modelling
must be further developed, to match the increasing diagnostic potential of the
data. Here we discuss some aspects of data interpretation and modelling,
focussing on the important case of stars with solar-like oscillations.Comment: Proc. HELAS Workshop on 'Synergies between solar and stellar
modelling', eds M. Marconi, D. Cardini & M. P. Di Mauro, Astrophys. Space
Sci., in the press Revision: correcting abscissa labels on Figs 1 and
Resolving the ISM at the Peak of Cosmic Star Formation with ALMA: The Distribution of CO and Dust Continuum in z ⌠2.5 Submillimeter Galaxies
We use Atacama Large Millimeter Array (ALMA) observations of four submillimeter galaxies (SMGs) at z ~ 2â3 to investigate the spatially resolved properties of the interstellar medium (ISM) at scales of 1â5 kpc (0farcs1â0farcs6). The velocity fields of our sources, traced by the 12CO(J = 3â2) emission, are consistent with disk rotation to the first order, implying average dynamical masses of ~3 Ă 1011 within two half-light radii. Through a Bayesian approach we investigate the uncertainties inherent to dynamically constraining total gas masses. We explore the covariance between the stellar mass-to-light ratio and CO-to-H2 conversion factor, α CO, finding values of for dark matter fractions of 15%. We show that the resolved spatial distribution of the gas and dust continuum can be uncorrelated to the stellar emission, challenging energy balance assumptions in global SED fitting. Through a stacking analysis of the resolved radial profiles of the CO(3â2), stellar, and dust continuum emission in SMG samples, we find that the cool molecular gas emission in these sources (radii ~5â14 kpc) is clearly more extended than the rest-frame ~250 ÎŒm dust continuum by a factor >2. We propose that assuming a constant dust-to-gas ratio, this apparent difference in sizes can be explained by temperature and optical depth gradients alone. Our results suggest that caution must be exercised when extrapolating morphological properties of dust continuum observations to conclusions about the molecular gas phase of the interstellar medium (ISM)
Dwelling on de Sitter
A careful reduction of the three-dimensional gravity to the Liouville
description is performed, where all gauge fixing and on-shell conditions come
from the definition of asymptotic de Sitter spaces. The roles of both past and
future infinities are discussed and the conditions space-time evolution imposes
on both Liouville fields are explicited. Space-times which correspond to
non-equivalent profiles of the Liouville field at past and future infinities
are shown to exist. The qualitative implications of this for any tentative dual
theory are presented.Comment: RevTeX 4, 8 pages, v3: Small clarifications on sections III and IV
and references added/corrected, v4: typo
- âŠ