Theoretical Evaluation (theoretical + evaluation)

Distribution by Scientific Domains


Selected Abstracts


Theoretical Evaluation of the Interface Modification for Aluminium Nitride Growth on Si

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003
P. Masri
Abstract In this work, we propose a strategy for the optimization of the SiC/Si structure as a subsequent substrate to grow aluminium nitride (AlN) layers on Si. Several routes are investigated within the framework of a theoretical approach which we recently developed and which has proved itself to be very useful in many aspects of the physics of heteroepitaxy. In this paper, we investigate one useful task of using Si as substrate with SiC buffer layer which may be grown by carbonization (C) of the Si surface. Germanium (Ge) incorporation is also modelled. The AlN/SiC/Si structure is theoretically optimized by determining the composition out of C and Ge of the buffer layer. [source]


Metal/Fluorocarbon Pyrolants: V. Theoretical Evaluation of the Combustion Performance of Metal/Fluorocarbon Pyrolants based on Strained Fluorocarbons

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 1 2004
Ernst-Christian Koch
Abstract The potential of strained fluorocarbons, which can act as oxidizers in metal-based pyrolant systems, is investigated. The oxidizing performance of fluorocarbons is evaluated by the enthalpy of combustion ,cH(298K) and the fractional electron transfer ,N. ,cH(298K) can be related to hybridisation, molar C/F ratio and strain of the parent carbon skeleton of the fluorocarbon. Considered fluorocarbons are tetrafluorotetrahedrane (CF)4 (3), tetrakis(trifluoromethyl)tetrahedrane C4(CF3)4 (4), hexafluoro[3]prismane (CF)6 (5), hexakis(trifluoromethyl)[3]prismane C6(CF3)6 (6), octafluorocubane (CF)8 (7), octakis(trifluoromethyl)cubane C8(CF3)8 (8), eicosafluorododecahedrane (CF)20 (9), eicosakis(trifluoromethyl)dodecahedrane C20(CF3)20 (10), C60F48 (11) and perfluorofullerane (CF)60 (12). Powerful oxidisers in terms of exothermicity are those possessing both tertiary CF-units and strained carbon skeletons. Nevertheless the reactivity, which is estimated on basis of ,N, the fraction of electrons transferred according to Pearson, has been found to be high with the corresponding perfluoromethyl derivatives and maximum with the fluorofulleranes. For part IV see Ref. 17. [source]


The Heat of Formation of the Uranyl Dication: Theoretical Evaluation Based on Relativistic Density Functional Calculations.

CHEMINFORM, Issue 13 2006
Lyudmila V. Moskaleva
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


Ignoring Distant Genealogic Loops Leads to False-positives in Homozygosity Mapping

ANNALS OF HUMAN GENETICS, Issue 6 2006
F. Liu
Summary Distant consanguineous loops are often unknown or ignored during homozygosity mapping analysis. This may potentially lead to an increased rate of false-positive linkage results. We show that failure to take into account the distant loops may seriously underestimate the degree of consanguinity, especially for people from genetically isolated populations; in 6 Alzheimer's disease (AD) patients the distant loops accounted for 57.7 % of inbreeding on average. Theoretical evaluation showed that ignoring distant loops, which account for 18-75% of inbreeding, inflates the frequency of false positive conclusions substantially in 2-point linkage analysis, up to several hundred times. In multipoint linkage analysis of the 6 AD patients a chromosome-wide "empirical" significance of 5% corresponded to a true false positive rate of 11.1%. We show that converting multiple loops to a hypothetical loop capturing all inbreeding may be a convenient solution to avoid false positive results. When extended genealogic data are not available a hypothetical loop may still be constructed based on genomic data. [source]


Theoretical evaluation of magnetoreception of power-frequency fields

BIOELECTROMAGNETICS, Issue 5 2010
Jacques Vanderstraeten
Abstract Several effects of power-frequency (50/60,Hz) magnetic fields (PF-MF) of weak intensity have been hypothesized in animals and humans. No valid mechanism, however, has been proposed for an interaction between PF-MF and biological tissues and living beings at intensities relevant to animal and human exposure. Here we proposed to consider PF-MF as disrupters of the natural magnetic signal. Under exposure to these fields, an oscillating field exists that results from the vectorial summation of both the PF-MF and the geomagnetic field. At a PF-MF intensity (rms) of 0.5,µT, the peak-to-peak amplitude of the axis and/or intensity variations of this resulting field exceeds the related discrimination threshold of magnetoreception (MR) in migrating animals. From our evaluation of the 50/60,Hz responsiveness of the putative mechanisms of MR, single domain particles (Kirschvink's model) appear unable to transduce that oscillating signal. On the contrary, radical pair reactions are able to, as well as interacting multidomain iron,mineral platelets and clusters of superparamagnetic particles (Fleissner/Solov'yov's model). It is, however, not yet known whether the reception of 50/60,Hz oscillations of the natural magnetic signal might be of consequence or not. Bioelectromagnetics 31:371,379, 2010. © 2010 Wiley-Liss, Inc. [source]


Helium fine structure: Unsolved many-body-QED Problem

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2006
Ingvar LindgrenArticle first published online: 12 JUL 200
Abstract Theoretical and experimental results for the fine-structure separation of the lowest 3P state of the helium atom disagree significantly. The experiment is well checked and the disagreement is most likely due to deficiency in the theoretical evaluation, which is based upon power expansion of the Bethe-Salpeter equation. A new numerical technique is introduced for combining QED and electron-correlation calculations, which in the future might contribute to resolving the issue. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source]


Density functional study of the relative reactivity in the concerted 1,3-dipolar cycloaddition of nitrile ylide to disubstituted ethylenes

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2001
Hsin-Yi Liao
Abstract Density functional theory was used to perform a theoretical evaluation of (E)-1,2-disubstituted ethylenes as dipolarophiles for the 1,3-dipolar cycloaddition reaction. The reactivities of electron-withdrawing and -donating substituted ethylenes were examined by estimating their activation energies. The calculated activation energies predicted that the most reactive species is (E)-1,2-C2H2(NO)2, whereas the least reactive is (E)-2-butene. Namely, it was demonstrated that 16-electron 1,3-dipole reactants with more electropositive substituents in terminal positions and ethylenes that possess more strongly electron-withdrawing substituents facilitate 1,3-dipolar cycloaddition reactions. All of the theoretical results can be rationalized using the configuration mixing model. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 318,323, 2001 [source]


On the Possibility of "International Community"

INTERNATIONAL STUDIES REVIEW, Issue 1 2009
David C. Ellis
The term "international community" has recently become commonplace in leaders' and academics' discourse and the subject of some analysis. While scholars have begun to explore its usage, there has not yet been a modern theoretical evaluation of the prerequisites for creating an international community. This article conducts a theoretical analysis on the types of international communities that can be generated in international politics and the structural factors necessary for their manifestation. It continues by investigating the possibility of forming a unitary actor, called the "International Community," tasked with resolving global commons issues through an international organization, such as the United Nations. The article concludes by arguing that the conditions do not yet exist for a meaningful "International Community." [source]


Drug release properties of polymer coated ion-exchange resin complexes: Experimental and theoretical evaluation

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2007
Seong Hoon Jeong
Abstract Although ion-exchange resins have been used widely as drug delivery systems, their exact release kinetics has not been reported yet. Usually only the rate-limiting step has been taken into account and the rest of the steps have been ignored as instantaneous processes. To investigate the exact release kinetics of polymer-coated drug/ion-exchange resin complexes for sustained drug delivery, the results of new mathematical modeling were compared with experimental results. Drug/resin complexes with a model drug, dextromethorphan, were prepared and used as cores for fluid-bed coating. An aqueous colloidal dispersion of poly(vinyl acetate) was applied for the coating. A comprehensive mathematical model was developed using a mechanistic approach by considering diffusion, swelling, and ion-exchange processes solved by numerical techniques. The rate-limiting factor of the uncoated resin particles was diffusion through the core matrix. Similarly, in the coated particles the rate-limiting factor was diffusion through the coating membrane. The mathematical model has captured the phenomena observed during experimental evaluations and the release dynamics from uncoated and coated (at different coat levels) particles were predicted accurately (maximum RMSE 2.4%). The mathematical model is a useful tool to theoretically evaluate the drug release properties from coated ion-exchange complexes thus can be used for design purposes. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci [source]


Economics and Asia-Pacific Region Territorial and Maritime Disputes: Understanding the Political Limits to Economic Solutions

ASIAN POLITICS AND POLICY, Issue 4 2009
Jean-Marc F. Blanchard
Territorial and maritime disputes are a visible part of the tapestry of Asia-Pacific Region (APR) international relations. They have provoked frictions between states, militarized conflict, and even war. Some believe interstate economic ties or economic inducements have the potential to mitigate and resolve the APR's territorial and maritime controversies. In this article, I analyze, in two primary ways, the potential for economics to calm or resolve the APR's territorial and maritime disputes. One is a theoretical evaluation, while the other is an empirical examination. As for the latter, this article analyzes two specific quarrels: the China-Japan controversy over the East China Sea and Diaoyu/Senkaku Islands and the Japanese-Soviet/Russian conflict over the Northern Territories. In both cases, the economic optimist case is proved wanting. This article shows that researchers must pay attention to political factors, domestic and international, to identify the factors that facilitate/hinder a settlement of territorial and maritime disputes. [source]