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Theoretical Point (theoretical + point)
Selected AbstractsReaction of Bare VO+ and FeO+ with Ammonia: A Theoretical Point of ViewCHEMINFORM, Issue 8 2004Sandro Chiodo Abstract For Abstract see ChemInform Abstract in Full Text. [source] Newly qualified teachers' learning related to their use of information and communication technology: a Swedish perspectiveBRITISH JOURNAL OF EDUCATIONAL TECHNOLOGY, Issue 5 2006Sven B. Andersson This qualitative study focuses on newly qualified teachers' use of information and communication technology (ICT) as a tool for meeting the challenges of their everyday work. The overarching aim is to investigate whether they can contribute to new knowledge about learning in ICT contexts. Theoretical points of departure concern the changeable nature of learning in situations where ways of communicating knowledge and skills are changed. The study draws upon interviews and observations. The findings show intersections picturing the new technique as partly changing the circumstances for teaching, learning and collaboration between colleagues. The new teachers' utterances show that ICT utilisation is extensive and exhibits great variation both among female and among male participants. Boundary-crossing changes become visible in the collaboration between more experienced teachers and those who are newly qualified, especially when they work on a common development project. However, there are relatively few teachers who bring up active ICT use in connection with pupils' learning. Changed roles because of ICT competence raise questions about the importance of systematic ICT features within teacher education. Many of the newly qualified teachers wish they had more knowledge about ICT and related techniques. Another question is whether newly qualified teachers who show interest in using the technique can take on the role as agents of change in their active and creative use of ICT. [source] Control of muscle blood flow during exercise: local factors and integrative mechanismsACTA PHYSIOLOGICA, Issue 4 2010I. Sarelius Abstract Understanding the control mechanisms of blood flow within the vasculature of skeletal muscle is clearly fascinating from a theoretical point of view due to the extremely tight coupling of tissue oxygen demands and blood flow. It also has practical implications as impairment of muscle blood flow and its prevention/reversal by exercise training has a major impact on widespread diseases such as hypertension and diabetes. Here we analyse the role of mediators generated by skeletal muscle activity on smooth muscle relaxation in resistance vessels in vitro and in vivo. We summarize their cellular mechanisms of action and their relative roles in exercise hyperaemia with regard to early and late responses. We also discuss the consequences of interactions among mediators with regard to identifying their functional significance. We focus on (potential) mechanisms integrating the action of the mediators and their effects among the cells of the intact arteriolar wall. This integration occurs both locally, partly due to myoendothelial communication, and axially along the vascular tree, thus enabling the local responses to be manifest along an entire functional vessel path. Though the concept of signal integration is intriguing, its specific role on the control of exercise hyperaemia and the consequences of its modulation under physiological and pathophysiological conditions still await additional analysis. [source] Whither causal models in the neuroscience of ADHD?DEVELOPMENTAL SCIENCE, Issue 2 2005Dave Coghill In this paper we examine the current status of the science of ADHD from a theoretical point of view. While the field has reached the point at which a number of causal models have been proposed, it remains some distance away from demonstrating the viability of such models empirically. We identify a number of existing barriers and make proposals as to the best way for these to be overcome in future studies. These include the need to work across multiple levels of analysis in multidisciplinary teams; the need to recognize the existence of, and then model, causal heterogeneity; the need to integrate environmental and social processes into models of genetic and neurobiological influence; and the need to model developmental processes in a dynamic fashion. Such a model of science, although difficult to achieve, has the potential to provide the sort of framework for programmatic model-based research required if the power and sophistication of new neuroscience technologies are to be effectively exploited. [source] Resource allocation with minimum rates for OFDM broadcast channels,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2007Carolin Huppert Downlink transmissions with minimum rate requirements over orthogonal frequency division multiplexing (OFDM) channels are commonly done by means of scheduling algorithms. However, regarding it from an information theoretical point of view, this is not optimal since broadcast techniques can achieve higher rates. The drawbacks of the optimum broadcast algorithm are that the signalling overhead is larger than for scheduling and also the computational complexity is much higher. In this paper we propose an algorithm which overcomes these points. This algorithm is a hybrid algorithm combining scheduling and broadcast approaches. Thus, it combines advantages of both methods. Furthermore, we present modifications to this algorithm to avoid irresolvable decoding dependencies. We show by means of simulation results that the proposed algorithm operates close to the optimum performance and that it outperforms a pure scheduling approach. Copyright © 2007 John Wiley & Sons, Ltd. [source] Functional interaction of intestinal CYP3A4 and P-glycoproteinFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 6 2004Kari T. Kivistö Abstract Intestinal CYP3A4-mediated biotransformation and active efflux of absorbed drug by P-glycoprotein are major determinants of bioavailability of orally administered drugs. The hypothesis that CYP3A4 and P-glycoprotein may act in concert to limit oral drug bioavailability is attractive from a theoretical point of view. Evidence in support of such an interplay between CYP3A4 and P-glycoprotein comes mainly from a limited number of in vitro and animal studies. Obviously, it is a challenging task to demonstrate in vivo in humans that the function of CYP3A4 and P-glycoprotein in enterocytes is complementary, and results to directly support this concept remain elusive. However, CYP3A4 and P-glycoprotein are clearly an integral part of an intestinal defence system to protect the body against harmful xenobiotics, and drugs that are substrates of both proteins often have a low bioavailability after oral administration. The functional interaction of intestinal CYP3A4 and P-glycoprotein warrants additional study. Further understanding this interplay would be potentially useful during drug development to solve bioavailability problems of new drug entities. [source] Nutrient fluxes at the river basin scale.HYDROLOGICAL PROCESSES, Issue 5 2001II: the balance between data availability, model complexity Abstract In order to model complex environmental systems, one needs to find a balance between the model complexity and the quality of the data available needed to run and validate the model. This paper describes a method to find this balance. Four models of different complexity were applied to describe the transfer of nitrogen and phosphorus from pollution sources to river outlets in two large European river basins (Rhine and Elbe). A comparison of the predictive capability of these four models tells us something about the added value of the added model complexity. We also quantified the errors in the data that were used to run and validate the models and analysed to what extent the model validation errors could be attributed to data errors, and to what extent to shortcomings of the model. We conclude that although the addition of more process description is interesting from a theoretical point of view, it does not necessarily improve the predictive capability. Although our analysis is based on an extensive pollution-sources,river-load database it appeared that the information content of this database was sufficient only to support models of a limited complexity. Our analysis also illustrates that for a proper justification of a model's degree of complexity one should compare the model to simplified versions of the model. Copyright © 2001 John Wiley & Sons, Ltd. [source] The evolution of mathematical immunologyIMMUNOLOGICAL REVIEWS, Issue 1 2007Yoram Louzoun Summary:, The types of mathematical models used in immunology and their scope have changed drastically in the past 10 years. Classical models were based on ordinary differential equations (ODEs), difference equations, and cellular automata. These models focused on the ,simple' dynamics obtained between a small number of reagent types (e.g. one type of receptor and one type of antigen or two T-cell populations). With the advent of high-throughput methods, genomic data, and unlimited computing power, immunological modeling shifted toward the informatics side. Many current applications of mathematical models in immunology are now focused around the concepts of high-throughput measurements and system immunology (immunomics), as well as the bioinformatics analysis of molecular immunology. The types of models have shifted from mainly ODEs of simple systems to the extensive use of Monte Carlo simulations. The transition to a more molecular and more computer-based attitude is similar to the one occurring over all the fields of complex systems analysis. An interesting additional aspect in theoretical immunology is the transition from an extreme focus on the adaptive immune system (that was considered more interesting from a theoretical point of view) to a more balanced focus taking into account the innate immune system also. We here review the origin and evolution of mathematical modeling in immunology and the contribution of such models to many important immunological concepts. [source] Spatial foundation structures over no tension soilINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2005A. Baratta Abstract The problem of the stress distribution induced in the soil by a single circular foundation structure is approached in a three-dimensional analysis. Since the soil is typically made by not-cohesive materials, its behaviour is modelled by means of the not resisting tension (NRT) hypothesis, thus assuming that its very low resistance to tensile stresses can be completely neglected and that it keeps linearly elastic under pure compression. After developing the problem from a theoretical point of view on the basis of an energetic approach, a numerical application,which is able to reproduce the stress distribution induced by a circular foundation on the soil,is performed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Individual influences on knowledge acquisition in a call center training context in GermanyINTERNATIONAL JOURNAL OF TRAINING AND DEVELOPMENT, Issue 1 2007Jens Rowold From both a practical and a theoretical point of view, it is important to identify factors that foster knowledge acquisition in organizational training programs. Recent models of training effectiveness have proposed relationships between trainees' characteristics and subsequent learning. The present study tested the impact of trainees' pretraining expectations, post-training reaction to training, expectation fulfillment and commitment on declarative knowledge acquisition, while controlling for education and motivation to learn. Participants were call center agents (N = 84), working in 10 call centers in Germany. Results showed that, in addition to education and motivation to learn, only expectation fulfillment significantly predicted learning. Implications for practice and future research were discussed. [source] Interesting properties of Thomas,Fermi kinetic and Parr electron,electron-repulsion DFT energy functional generated compact one-electron density approximation for ground-state electronic energy of molecular systemsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2009Sandor Kristyan Abstract The reduction of the electronic Schrodinger equation or its calculating algorithm from 4N -dimensions to a (nonlinear, approximate) density functional of three spatial dimension one-electron density for an N -electron system, which is tractable in the practice, is a long desired goal in electronic structure calculation. If the Thomas-Fermi kinetic energy (,,,5/3dr1) and Parr electron,electron repulsion energy (,,,4/3dr1) main-term functionals are accepted, and they should, the later described, compact one-electron density approximation for calculating ground state electronic energy from the 2nd Hohenberg,Kohn theorem is also noticeable, because it is a certain consequence of the aforementioned two basic functionals. Its two parameters have been fitted to neutral and ionic atoms, which are transferable to molecules when one uses it for estimating ground-state electronic energy. The convergence is proportional to the number of nuclei (M) needing low disc space usage and numerical integration. Its properties are discussed and compared with known ab initio methods, and for energy differences (here atomic ionization potentials) it is comparable or sometimes gives better result than those. It does not reach the chemical accuracy for total electronic energy, but beside its amusing simplicity, it is interesting in theoretical point of view, and can serve as generator function for more accurate one-electron density models. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009 [source] Staff attitudes towards aggression in health care: a review of the literatureJOURNAL OF PSYCHIATRIC & MENTAL HEALTH NURSING, Issue 1 2005G. J. JANSEN rn mnsc The aim of this literature review was to explore the attitudes of health care workers towards inpatient aggression and to analyse the extent to which attitudes, as defined from a theoretical point of view, were addressed in the selected studies. Databases from 1980 up to the present were searched, and a content analysis was done on the items of the selected studies. The concepts ,cognition' and ,attitude' from the framework of ,The Theory of Reasoned Action' served as categories. The self-report questionnaire was the most common instrument used and three instruments specifically designed to measure attitudes were found. These instruments lacked profound validity testing. From a total of 74 items, two thirds focussed on cognitions and only a quarter really addressed attitudes towards aggression. Research was particularly concerned with the cognitions that nurses had about aggression, and attitudes were studied only to a limited extent. Researchers used different instruments, which makes it difficult to compare results across settings. [source] HALS in polyamide 6 polymerizationMACROMOLECULAR SYMPOSIA, Issue 1 2003Roberto Filippini Fantoni Abstract The use of Hindered Amine Light Stabilizers (HALS) directly in polyamide 6 polymerization can cause some problems. The following two problems were the focus of our project: 1) We investigated, from a theoretical point of view, the results of introducing directly one of the precursors of HALS into polyamide 6 polymerization. For the investigation, 4 amino-2,2,6,6-tetramethylpiperidine (triaceton-diamine or TAD) was chosen. We considered the TAD chain-ending effects and their influence on the total amount of amino chain-endings that can be titrated, a parameter of primary importance in the fibre field. 2) We examined the amide interchange reaction in the case of an HALS containing two amide groups, using a product available on the market, N,N,-bis(tetramethyl-4-piperidyl)isophtalamide. In this case we were able to generate a couple of equations that allows one to calculate the quantity of amide interchanged HALS. This was done by comparing the results (molecular weight and chain-endings analysis) of polymerization with and without HALS. [source] Gravitational lensing by cosmic strings: what we learn from the CSL-1 caseMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007M. V. Sazhin ABSTRACT Cosmic strings were postulated by Kibble in 1976 and, from a theoretical point of view, their existence finds support in modern superstring theories, both in compactification models and in theories with extended additional dimensions. Their eventual discovery would lead to significant advances in both cosmology and fundamental physics. One of the most effective ways to detect cosmic strings is through their lensing signatures which appear to be significantly different from those introduced by standard lenses (i.e. compact clumps of matter). In 2003, the discovery of the peculiar object CSL-1 raised the interest of the physics community since its morphology and spectral features strongly argued in favour of it being the first case of gravitational lensing by a cosmic string. In this paper we provide a detailed description of the expected observational effects of a cosmic string and show, by means of simulations, the lensing signatures produced on background galaxies. While high angular resolution images obtained with Hubble Space Telescope, revealed that CSL-1 is a pair of interacting ellipticals at redshift 0.46, it represents a useful lesson to plan future surveys. [source] Combination of Jacobi,Davidson and conjugate gradients for the partial symmetric eigenproblemNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 1 2002Y. Notay Abstract To compute the smallest eigenvalues and associated eigenvectors of a real symmetric matrix, we consider the Jacobi,Davidson method with inner preconditioned conjugate gradient iterations for the arising linear systems. We show that the coefficient matrix of these systems is indeed positive definite with the smallest eigenvalue bounded away from zero. We also establish a relation between the residual norm reduction in these inner linear systems and the convergence of the outer process towards the desired eigenpair. From a theoretical point of view, this allows to prove the optimality of the method, in the sense that solving the eigenproblem implies only a moderate overhead compared with solving a linear system. From a practical point of view, this allows to set up a stopping strategy for the inner iterations that minimizes this overhead by exiting precisely at the moment where further progress would be useless with respect to the convergence of the outer process. These results are numerically illustrated on some model example. Direct comparison with some other eigensolvers is also provided. Copyright © 2001 John Wiley & Sons, Ltd. [source] The New Economic Sociology of Prices: An Analysis Inspired by the Austrian School of EconomicsAMERICAN JOURNAL OF ECONOMICS AND SOCIOLOGY, Issue 2 2010Renaud Fillieule The new economic sociology includes some reference studies on the sociology of prices. They have not until now been studied by economists, and this article attempts to fill that gap by offering a detailed analysis, inspired by the Austrian School of Economics, of their object and approach. We first show that, from a theoretical point of view, the explanations advanced by these sociologists are based implicitly on basic models of economics, such as the "law of supply and demand" and the "law of costs," and that they cannot therefore replace economic explanations of prices. Secondly, from a methodological point of view, these studies are based on field surveys that provide concrete information on certain markets but they lose sight of an aspect that is fundamental to the Austrian School, the interdependence of prices in different markets. And when this interdependence is taken into account, namely, in the case of the relationship between cost and price, the causal link postulated by sociologists goes from cost to price when Austrian economists argue that it goes in the opposite direction. [source] Optical properties tailoring for new devices engineering in high-gap oxidesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2010Pier Carlo Ricci Abstract Monocrystal matrices of high-gap oxides are finding increasing applications as hosts of luminescent ions, typically rare earths (RE)s. Currently, RE-doped oxyorthosilicates, aluminum perovskites, and garnets (RE2SiO5,REAlO3,RE3Al5O12) are widely used as highly efficient and fast scintillators for ,-ray detection. On the other hand, shallow or deep intragap energy levels, due to stoichiometric deviation or impurities unintentionally added in the crystals, play a counteractive role giving rise to slower scintillation decay time, reduced light yield and afterglow. The aim of this work is to show how it is possible to tailor these unwelcome outcomes and RE-ion interactions for engineering new devices for optical memory storage. In this sense, experimental results of thermo- and radio-luminescence are presented. The role of the bandgap and the location in energy of the levels due to the RE dopants and to the defects is discussed from a theoretical point of view. The feasibility in the near future of new promising transparent displays is also discussed. [source] Theory of quantum transport in carbon nanotubes: Perfect conductance, dynamical conductivity, and inter-wall interactionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007Tsuneya Ando Abstract A brief review is given on transport properties of carbon nanotubes mainly from a theoretical point of view. The topics include an effective-mass description of electronic states, the absence of backward scattering except for scatterers with a potential range smaller than the lattice constant, the presence of a perfectly conducting channel, and effects of symmetry breaking perturbations. The dynamical conductivity in the presence of a perfect channel and inter-wall interactions in double-wall nanotubes are also discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Bent and Linear Forms of the (,-Oxo)bis[trichloroferrate(III)] Dianion: An Intermolecular Effect , Structural, Electronic and Magnetic PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2003Agustí Lledós Abstract We have analyzed the great diversity of Fe,O,Fe angles, 140,180°, found in the X-ray structures of the (,-oxo)bis[trichloroferrate(III)] dianion [Cl3FeOFeCl3]2, from both experimental and theoretical points of view. Theoretical calculations show that only the linear isomer is found as a minimum on the potential energy surface. Detailed analysis of the crystal packing indicates that the angular form is due to attractive intermolecular interactions. Analysis of a selected reduced set of the 45 crystal structures retrieved from the Cambridge Structural Database allowed us to classify the bending of the [Cl3FeOFeCl3]2, dianion in three categories, depending on the balance and strength of the intermolecular O···H,X contacts. A crystal diffraction study on the bis(benzyltrimethylammonium) salt has shown both bent (144.6°) and linear (180°) forms of the (,-oxo)bis[trichloroferrate(III)] dianion. The magnetic susceptibility of this compound has been fitted by assuming two equally weighted contributions (Jang and Jlin) of the two forms, considering Jang , Jlin estimated by theoretical calculations. The obtained Jang and Jlin of ,117 and ,133 cm,1 respectively, agree well with B3LYP results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] New Directions in Natural Resource Management The Offer of Actor-Network TheoryIDS BULLETIN, Issue 4 2001Nathalie A. Steins Summaries The article offers theoretical insights from Actor-Network Theory (ANT) as to how natural resource management (NRM) perspectives might be enhanced. ANT asks us to abolish the conventional sociological practice of studying phenomena in terms of predefined categories and principles, as they hinder our analysis of how the stakeholders involved construct resource management processes and the way these constructions are used. In this analytical process, any (uncertain) outcome of NRM is regarded as an effect of the interplay amongst the different stakes in the resource and the way stakeholders continuously mobilise social and material resources in order to achieve their goals. Only by analysing how certain outcomes have been achieved can we develop our understanding of the dynamics and uncertainties involved in NRM. The article uses empirical examples from coastal management scenarios to illustrate these theoretical points. [source] Emotional awareness in substance-dependent patients,JOURNAL OF CLINICAL PSYCHOLOGY, Issue 6 2010Solange Carton Abstract We explored emotional awareness in substance-dependent patients and its relationships to self-reported alexithymia. Sixty-four outpatients with drug dependence or alcohol dependence were evaluated before the beginning of treatment with the Hamilton Depressive Scale and the Covi Anxiety Scale, and they completed the Toronto Alexithymia Scale (TAS-20) and the Levels of Emotional Awareness Scale (LEAS). Subjects exhibited low levels of emotional awareness and TAS-20 scores were high. Both measures were not related to depressive and anxious symptomatology. This research is the first to provide LEAS results with substance-dependent patients and highlights their deficits in emotions' differentiation and complexity. The lack of a relationship between LEAS and TAS-20 is discussed from the methodological and theoretical points of view. © 2010 Wiley Periodicals, Inc. J Clin Psychol 66:1,12, 2010. [source] | ||||||||||||||||||||||||||||