18,298 research outputs found
Deep gamma ray penetration in thick shields
Appropriate importance function and sampling scheme facilitates the application of the Monte Carlo method to problems involving the deep penetration of radiation
Bayesian inference of nanoparticle-broadened x-ray line profiles
A single and self-contained method for determining the crystallite-size
distribution and shape from experimental x-ray line profile data is presented.
We have shown that the crystallite-size distribution can be determined without
assuming a functional form for the size distribution, determining instead the
size distribution with the least assumptions by applying the Bayesian/MaxEnt
method. The Bayesian/MaxEnt method is tested using both simulated and
experimental CeO data. The results demonstrate that the proposed method
can determine size distributions, while making the least number of assumptions.
The comparison of the Bayesian/MaxEnt results from experimental CeO with
TEM results is favorableComment: 43 pages, 13 Figures, 5 Table
Widening the prostacyclin paradigm: tissue fibroblasts are a critical site of production and 2 anti-thrombotic protection
Prostacyclin is a fundamental signaling pathway traditionally associated with the cardiovascular system and protection against thrombosis but which also has regulatory functions in fibrosis, proliferation, and immunity. Prevailing dogma states that prostacyclin is principally derived from vascular endothelium, although it is known that other cells can also synthesize it. However, the role of nonendothelial sources in prostacyclin production has not been systematically evaluated resulting in an underappreciation of their importance relative to better characterized endothelial sources..
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Teaching schools evaluation. Research Brief
This Research Brief reports the findings from a two-year study (2013-15) in to the work of teaching schools and their alliances commissioned by the National College for Teaching and Leadership (NCTL). The broad aim of the study was to investigate the effectiveness and impact of teaching schools on improvement, and identify the quality and scope of external support that are required to enhance these . This was achieved through combining qualitative and quantitative data collection and analysis derived from three research activities: case studies of 26 teaching schools alliances (TSAs), a national survey of the first three cohorts of 345 TSAs, and secondary research and analysis of national performance and inspection results
Role of Boron p-Electrons and Holes in Superconducting MgB2, and other Diborides: A Fully-Relaxed, Full-Potential Electronic Structure Study
We present the results of fully-relaxed, full-potential electronic structure
calculations for the new superconductor MgB2, and BeB2, NaB2, and AlB2, using
density-functional-based methods. Our results described in terms of (i) density
of states (DOS), (ii) band-structure, and (iii) the DOS and the charge density
around the Fermi energy EF, clearly show the importance of B p-band for
superconductivity. In particular, we show that around EF, the charge density in
MgB2, BeB2 and NaB2 is planar and is associated with the B plane. For BeB2 and
NaB2, our results indicate qualitative similarities but significant
quantitative differences in their electronic structure due to different lattice
constants a and c.Comment: 4 pages, 4 figures, Submitted to Phys Rev. Lett. on March 6, 2001;
resubmission on April 2
Algebraic Aspects of Abelian Sandpile Models
The abelian sandpile models feature a finite abelian group G generated by the
operators corresponding to particle addition at various sites. We study the
canonical decomposition of G as a product of cyclic groups G = Z_{d_1} X
Z_{d_2} X Z_{d_3}...X Z_{d_g}, where g is the least number of generators of G,
and d_i is a multiple of d_{i+1}. The structure of G is determined in terms of
toppling matrix. We construct scalar functions, linear in height variables of
the pile, that are invariant toppling at any site. These invariants provide
convenient coordinates to label the recurrent configurations of the sandpile.
For an L X L square lattice, we show that g = L. In this case, we observe that
the system has nontrivial symmetries coming from the action of the cyclotomic
Galois group of the (2L+2)th roots of unity which operates on the set of
eigenvalues of the toppling matrix. These eigenvalues are algebraic integers,
whose product is the order |G|. With the help of this Galois group, we obtain
an explicit factorizaration of |G|. We also use it to define other simpler,
though under-complete, sets of toppling invariants.Comment: 39 pages, TIFR/TH/94-3
Resource Control for Synchronous Cooperative Threads
We develop new methods to statically bound the resources needed for the
execution of systems of concurrent, interactive threads. Our study is concerned
with a \emph{synchronous} model of interaction based on cooperative threads
whose execution proceeds in synchronous rounds called instants. Our
contribution is a system of compositional static analyses to guarantee that
each instant terminates and to bound the size of the values computed by the
system as a function of the size of its parameters at the beginning of the
instant. Our method generalises an approach designed for first-order functional
languages that relies on a combination of standard termination techniques for
term rewriting systems and an analysis of the size of the computed values based
on the notion of quasi-interpretation. We show that these two methods can be
combined to obtain an explicit polynomial bound on the resources needed for the
execution of the system during an instant. As a second contribution, we
introduce a virtual machine and a related bytecode thus producing a precise
description of the resources needed for the execution of a system. In this
context, we present a suitable control flow analysis that allows to formulte
the static analyses for resource control at byte code level
Book Reviews
It is refreshing to find among the myriad of volumes on trial practice published in recent years one which neither assumes that cases are tried in an emotional vacuum, where nothing but concrete facts and abstract propositions of law can influence the jury, nor deteriorates into a personal reminiscence on the part of the author of past court-room victories with the simple instruction to the reader to go and do likewise. Obviously a widely experienced courtroom practitioner, Mr.Gazan seldom utilizes that background directly for purposes of illustration; rather he draws from it general propositions applicable to courtroom procedure, which he then buttresses where necessary with citations to reported decisions. And to this he adds another ingredient found all too seldom in books of this type--a simple, straightforward,readable style which is easily understood and easily remembered
Synthesis and characterization of biodegradable lignin nanoparticles with tunable surface properties
Lignin nanoparticles can serve as biodegradable carriers of biocidal actives with minimal environmental footprint. Here we describe the colloidal synthesis and interfacial design of nanoparticles with tunable surface properties using two different lignin precursors, Kraft (Indulin AT) lignin and Organosolv (high-purity lignin). The green synthesis process is based on flash precipitation of dissolved lignin polymer, which enabled the formation of nanoparticles in the size range of 45–250 nm. The size evolution of the two types of lignin particles is fitted on the basis of modified diffusive growth kinetics and mass balance dependencies. The surface properties of the nanoparticles are fine-tuned by coating them with a cationic polyelectrolyte, poly(diallyldimethylammonium chloride). We analyze how the colloidal stability and dispersion properties of these two types of nanoparticles vary as a function of pH and salinities. The data show that the properties of the nanoparticles are governed by the type of lignin used and the presence of polyelectrolyte surface coating. The coating allows the control of the nanoparticles’ surface charge and the extension of their stability into strongly basic regimes, facilitating their potential application at extreme pH conditions
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