Unknown Properties (unknown + property)

Distribution by Scientific Domains

Selected Abstracts

An investigation of liquid film thickness during solutal Marangoni condensation using a laser absorption method: Absorption property and examination of measuring method

Yoshio Utaka
Abstract The objective of the study is to establish a method for measuring the thickness of thin condensates of liquid mixtures using a laser light absorption method during the process of water,ethanol Marangoni dropwise condensation. First, the extinction property of the test material, with unknown properties related to infrared laser light having a wavelength of 3.39µm, was measured. Next, measurements were made of the variations in condensate film thickness after the sweeping of the heat transfer surface by departing drops in the Marangoni dropwise condensation cycle. The precision of this method was investigated on the basis of the extinction coefficient of the test material and the thickness of the liquid film. Results showed that this method provides good precision and is applicable to the measurement of other similar materials. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 700,711, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10124 [source]

Notes on quantitative structure-properties relationships (QSPR) (1): A discussion on a QSPR dimensionality paradox (QSPR DP) and its quantum resolution

Ramon Carbó-Dorca
Abstract Classical quantitative structure-properties relationship (QSPR) statistical techniques unavoidably present an inherent paradoxical computational context. They rely on the definition of a Gram matrix in descriptor spaces, which is used afterwards to reduce the original dimension via several possible kinds of algebraic manipulations. From there, effective models for the computation of unknown properties of known molecular structures are obtained. However, the reduced descriptor dimension causes linear dependence within the set of discrete vector molecular representations, leading to positive semi-definite Gram matrices in molecular spaces. To resolve this QSPR dimensionality paradox (QSPR DP) here is proposed to adopt as starting point the quantum QSPR (QQSPR) computational framework perspective, where density functions act as infinite dimensional descriptors. The fundamental QQSPR equation, deduced from employing quantum expectation value numerical evaluation, can be approximately solved in order to obtain models exempt of the QSPR DP. The substitution of the quantum similarity matrix by an empirical Gram matrix in molecular spaces, build up with the original non manipulated discrete molecular descriptor vectors, permits to obtain classical QSPR models with the same characteristics as in QQSPR, that is: possessing a certain degree of causality and explicitly independent of the descriptor dimension. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009 [source]

An optimal memory-reduced procedure for calculating adjoints of the instationary Navier-Stokes equations

Michael Hinze
Abstract This paper discusses approximation schemes for adjoints in control of the instationary Navier,Stokes system. It tackles the storage problem arising in the numerical calculation of the appearing adjoint equations by proposing a low-storage approach which utilizes optimal checkpointing. For this purpose, a new proof of optimality is given. This new approach gives so far unknown properties of the optimal checkpointing strategies and thus provides new insights. The optimal checkpointing allows a remarkable memory reduction by accepting a slight increase in run-time caused by repeated forward integrations as illustrated by means of the Navier,Stokes equations. In particular, a memory reduction of two orders of magnitude causes only a slow down factor of 2,3 in run-time. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Mg-related acceptors in GaN

B. Monemar
Abstract Photoluminescence spectra of c -plane Mg doped GaN samples grown by MOVPE on bulk GaN templates reveal previously unknown properties, like the presence of several Mg-related acceptors. The use of unstrained samples allows a study of both bound exciton (BE) and donor-acceptor pair (DAP) spectra. Two main acceptors A1 and A2 are observed strongly in BE spectra as well as in DAP spectra, they have similar binding energies, i.e. about 220 meV. The common assignment of the deeper blue PL emission at 2.8,3.0 eV to a deep donor-shallow acceptor transition is questioned, and discussed in connection with the compensation problem in p-GaN. It seems like the Fermi level in p-GaN is controlled by a set of Mg-related acceptors at energies 0.2,0.6 eV from the valence band top. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Nonsteroidal antiinflammatory drugs as therapeutic agents for Alzheimer's disease

Todd E. Golde
One feature of the end-stage pathology of Alzheimer's disease (AD) is the presence of numerous inflammatory markers associated with the amyloid , protein (A,) deposits in the brain. Experimental data strongly suggests that A, aggregates can incite an inflammatory response, but there are also data suggesting that inflammation can promote A, production and deposition. Thus, antiinflammatory drugs may have some role in AD therapy. This idea is supported by epidemiologic data, which shows that long-term use of nonsteroidal antiinflammatory drugs (NSAIDs) confers protection from the development of AD. Significantly, oral salicylates have not been consistently shown to confer protection. Such studies have raised questions regarding the target or targets of NSAIDs that account for their apparent protection from AD. We have recently found that some NSAIDs have a novel mechanism of action, namely, selective lowering of the pathogenic A,42 peptide, that could contribute to their efficacy in AD. Further study will be needed to determine if the classic antiinflammatory properties of NSAIDs, the A,42-lowering property, another known or unknown property, or a combination of these contributes to NSAIDs apparent ability to protect individuals from the development of AD. Drug Dev. Res. 56:415,420, 2002. © Wiley-Liss, Inc. [source]