683 research outputs found
Monte Carlo transient phonons transport in silicon and germanium at nanoscales
Heat transport at nanoscales in semiconductors is investigated with a
statistical method. The Boltzmann Transport Equation (BTE) which characterize
phonons motion and interaction within the crystal lattice has been simulated
with a Monte Carlo technique. Our model takes into account media frequency
properties through the dispersion curves for longitudinal and transverse
acoustic branches. The BTE collisional term involving phonons scattering
processes is simulated with the Relaxation Times Approximation theory. A new
distribution function accounting for the collisional processes has been
developed in order to respect energy conservation during phonons scattering
events. This non deterministic approach provides satisfactory results in what
concerns phonons transport in both ballistic and diffusion regimes. The
simulation code has been tested with silicon and germanium thin films;
temperature propagation within samples is presented and compared to analytical
solutions (in the diffusion regime). The two materials bulk thermal
conductivity is retrieved for temperature ranging between 100 K and 500 K. Heat
transfer within a plane wall with a large thermal gradient (250 K-500 K) is
proposed in order to expose the model ability to simulate conductivity thermal
dependence on heat exchange at nanoscales. Finally, size effects and validity
of heat conduction law are investigated for several slab thicknesses
Campagnes de 1810 en Portugal, [18]11, 12, 13 Espagne, [18]14 France, 1815 Belgique ou Souvenirs militaires
Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 200
The Nearby Supernova Factory
The Nearby Supernova Factory (SNfactory) is an ambitious project to find and
study in detail approximately 300 nearby Type Ia supernovae (SNe~Ia) at
redshifts 0.03<z<0.08. This program will provide an exceptional data set of
well-studied SNe in the nearby smooth Hubble flow that can be used as
calibration for the current and future programs designed to use SNe to measure
the cosmological parameters. The first key ingredient for this program is a
reliable supply of Hubble-flow SNe systematically discovered in unprecedented
numbers using the same techniques as those used in distant SNe searches. In
2002, 35 SNe were found using our test-bed pipeline for automated SN search and
discovery. The pipeline uses images from the asteroid search conducted by the
Near Earth Asteroid Tracking group at JPL. Improvements in our subtraction
techniques and analysis have allowed us to increase our effective SN discovery
rate to ~12 SNe/month in 2003.Comment: 7 pages, 3 figures to be published in New Astronomy Review
Potential role of PC-1 expression and pyrophosphate elaboration in the molecular etiology of the FGFR-associated craniosynostosis syndromes
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73652/1/j.1601-6343.2007.00387.x.pd
Building block libraries and structural considerations in the self-assembly of polyoxometalate and polyoxothiometalate systems
Inorganic metal-oxide clusters form a class of compounds that are unique in their topological and electronic versatility and are becoming increasingly more important in a variety of applications. Namely, Polyoxometalates (POMs) have shown an unmatched range of physical properties and the ability to form structures that can bridge several length scales. The formation of these molecular clusters is often ambiguous and is governed by self-assembly processes that limit our ability to rationally design such molecules. However, recent years have shown that by considering new building block principles the design and discovery of novel complex clusters is aiding our understanding of this process. Now with current progress in thiometalate chemistry, specifically polyoxothiometalates (POTM), the field of inorganic molecular clusters has further diversified allowing for the targeted development of molecules with specific functionality. This chapter discusses the main differences between POM and POTM systems and how this affects synthetic methodologies and reactivities. We will illustrate how careful structural considerations can lead to the generation of novel building blocks and further deepen our understanding of complex systems
Hermite matrix in Lagrange basis for scaling static output feedback polynomial matrix inequalities
Evidence that cycloleucine affects the high-affinity systems of amino acid uptake in cultured human fibroblasts
Host genotype and amoxicillin administration affect the incidence of diarrhoea and faecal microbiota of weaned piglets during a natural multiresistant ETEC infection
RNA fusions involving CD28 are rare in peripheral T-cell lymphomas and concentrate mainly in those derived from follicular helper T cells.
Research lette
The Still Bay points of Apollo 11 Rock Shelter, Namibia : an inter-regional perspective
Abstract: Dating to roughly 80,000 to 70,000 years ago, components of the Still Bay technocomplex of southern Africa and their potential behavioural implications have been widely discussed. Stone points with invasive retouch, as defined over 90 years ago by Goodwin and van Riet Lowe, serve as markers for Still Bay assemblages, yet many Still Bay sites remain undated and comprehensive, comparable sets of data for their point assemblages remain unpublished. Much of the Middle Stone Age at the site of Apollo 11 in Namibia was undated until 2010, when a potential Still Bay component was announced. Although a Still Bay assemblage at Apollo 11 would represent the most northwesterly and inland expression of this technocomplex, its points have never been fully analysed. This paper presents their morphometric data and an interpretation of point-production strategies. These results are then compared with data obtained for two South African sites: Hollow Rock Shelter in the Western Cape and Umhlatuzana in KwaZulu-Natal. This comparison demonstrates that whereas there are no statistically significant differences in the morphometric data sets between the three sites, there are both similarities and differences in point-production strategies, cross-section shapes and the use of raw materials for knapping. It is suggested that these similarities and variations represent aspects of how knowledge-transfer systems and knapping conventions were followed on both intra-regional and inter-regional scales
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