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Transfer Models (transfer + models)
Selected AbstractsCovalently crosslinked complexes of bovine adrenodoxin with adrenodoxin reductase and cytochrome P450sccFEBS JOURNAL, Issue 6 2001Edman degradation of complexes of the steroidogenic hydroxylase system, Mass spectrometry NADPH-dependent adrenodoxin reductase, adrenodoxin and several diverse cytochromes P450 constitute the mitochondrial steroid hydroxylase system of vertebrates. During the reaction cycle, adrenodoxin transfers electrons from the FAD of adrenodoxin reductase to the heme iron of the catalytically active cytochrome P450 (P450scc). A shuttle model for adrenodoxin or an organized cluster model of all three components has been discussed to explain electron transfer from adrenodoxin reductase to P450. Here, we characterize new covalent, zero-length crosslinks mediated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide between bovine adrenodoxin and adrenodoxin reductase, and between adrenodoxin and P450scc, respectively, which allow to discriminate between the electron transfer models. Using Edman degradation, mass spectrometry and X-ray crystallography a crosslink between adrenodoxin reductase Lys27 and adrenodoxin Asp39 was detected, establishing a secondary polar interaction site between both molecules. No crosslink exists in the primary polar interaction site around the acidic residues Asp76 to Asp79 of adrenodoxin. However, in a covalent complex of adrenodoxin and P450scc, adrenodoxin Asp79 is involved in a crosslink to Lys403 of P450scc. No steroidogenic hydroxylase activity could be detected in an adrenodoxin ,P450scc complex/adrenodoxin reductase test system. Because the acidic residues Asp76 and Asp79 belong to the binding site of adrenodoxin to adrenodoxin reductase, as well as to the P450scc, the covalent bond within the adrenodoxin,P450scc complex prevents electron transfer by a putative shuttle mechanism. Thus, chemical crosslinking provides evidence favoring the shuttle model over the cluster model for the steroid hydroxylase system. [source] Effective thermal actions and thermal properties of timber members in natural firesFIRE AND MATERIALS, Issue 1 2006Jürgen KönigArticle first published online: 28 JUL 200 Abstract For the thermal analysis of structural or non-structural timber members, using conventional simplified heat transfer models, thermal conductivity values of timber are normally calibrated to test results such that they implicitly take into account influences such as mass transport that are not included in the model. Various researchers and designers have used such effective thermal conductivity values, originally determined for standard fire exposure, to evaluate other fire scenarios such as natural fires. This paper discusses in qualitative terms some parameters that govern the burning of wood and their influence on effective conductivity values. Reviewing fire tests of timber slabs under natural fire conditions, the study explains why effective conductivity values, giving correct results for the ISO 834 standard fire scenario, should not be used in other fire scenarios. For this reason, the thermal properties of timber given in EN 1995-1-2 are limited to standard fire exposure. As shown by heat transfer calculations, the effective thermal conductivity of the char layer is strongly dependent on the charring rate and therefore varies during a natural fire scenario. It has also been shown that char oxidation during the decay phase in a natural fire has a significant influence on the temperature development in the timber member, since char surface temperatures exceed the gas temperature in the compartment or furnace. Using increased effective gas temperature as thermal action during the decay phase, and varying conductivity values for the char layer, fairly good agreement could be obtained regarding the temperature development in the timber member and the char depth. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effect of micro mass transfer through phase interface on numerical simulation of solidification processHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2004Yanhui Feng Abstract Existing models for the solute redistribution during solidification have been reviewed. Some typical models are applied for the numerical simulation of heat and mass transfer with phase change under experimental condition of inverse casting. The results show that the effect of micro mass transfer models on the formation of the new phase cannot be omitted. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(6): 393,401, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20024 [source] A study of best practices in training transfer and proposed model of transferHUMAN RESOURCE DEVELOPMENT QUARTERLY, Issue 2 2008Lisa A. Burke Data were gathered from a sample of training professionals of an American Society of Training and Development (ASTD) chapter in the southern United States regarding best practices for supporting training transfer. Content analysis techniques, based on a rigorous methodology proposed by Insch, Moore, & Murphy (1997), were used to analyze the rich data. Findings suggest that interventions for bolstering training transfer are best carried out in the work context and design and delivery phase, take place after training or during, and involve trainers and supervisors. Activities garnering top attention from trainers as best practices include (starting with most frequently reported) supervisory support activities, coaching, opportunities to perform, interactive training activities, transfer measurement, and job-relevant training. Several new transfer variables also emerged from the data, indicating existing transfer models can be further refined. Ultimately, we propose a refined model of transfer to extend human resource development (HRD) theory in the area of transfer. [source] MONTE CARLO SIMULATION OF FAR INFRARED RADIATION HEAT TRANSFER: THEORETICAL APPROACHJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2006F. TANAKA ABSTRACT We developed radiation heat transfer models with the combination of the Monte Carlo (MC) method and computational fluid dynamic approach and two-dimensional heat transfer models based on the fundamental quantum physics of radiation and fluid dynamics. We investigated far infrared radiation (FIR) heating in laminar and buoyancy airflow. A simple prediction model in laminar airflow was tested with an analytical solution and commercial software (CFX 4). The adequate number of photon tracks for MC simulation was established. As for the complex designs model, the predicted results agreed well with the experimental data with root mean square error of 3.8 K. Because food safety public concerns are increasing, we applied this model to the prediction of the thermal inactivation level by coupling with the microbial kinetics model. Under buoyancy airflow condition, uniformity of FIR heating was improved by selecting adequate wall temperature and emissivity. [source] Overall efficiency evaluation of commercial distillation columns with valve and dualflow traysAICHE JOURNAL, Issue 9 2010T. L. Domingues Abstract The main objective of this work is to establish appropriated ways for estimating the overall efficiencies of industrial distillation columns with valve trays with downcomer and dualflow trays. The knowledge of efficiencies has fundamental importance in the design and performance evaluation of distillation columns. Searching in the literature, a tree of alternatives was identified to compose the tray efficiency model, depending on the mass transfer models, the liquid distribution and vapor flow models on the tray, the liquid entrainment model, the multicomponent mixture equilibrium model, the physical properties models, the height of froth on the tray model and the efficiency definition. In this work, different methods to predict the overall efficiency of distillation columns with valve and dualflow trays were composed and compared with data from three commercial distillation columns under different operating conditions. The models were inserted in the Aspen Plus 12.1 simulator, in Fortran language, together with tray geometrical data, fluid properties and operating data of the distillation columns. For each column, the best thermodynamic package was chosen by checking the temperature profile and overhead and bottom compositions obtained via simulation against the corresponding actual data of industrial columns. A modification in the fraction of holes evaluation that is jetting parameter of the Garcia's hydraulic model of dispersion above the tray was proposed. This modification produced better results than the original model to predict the fraction of holes that are jetting and in the efficiency of dualflow trays and similar results to Garcia model in the efficiency evaluation of valve trays. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] A simple device for the evaluation of the UV radiation indexMETEOROLOGICAL APPLICATIONS, Issue 2 2003Giuseppe Rocco Casale The solar ultraviolet radiation (UV) flux density at the earth's surface depends on the incoming solar energy and the transmission properties of the atmosphere. UV radiation is strongly absorbed by ozone in the spectral range 200,310 nm, while the attenuation is increasingly weaker at longer wavelengths. Following the discovery of the Antarctic ozone hole in 1985, the risk of a possible UV increase at ground level, due to the observed stratospheric ozone depletion, has heightened the interest within the scientific community given the potentially harmful effects on terrestrial and aquatic ecosystems. Spectroradiometers, broad-band meters and dosimeters may be used for measurements of solar UV. In addition, radiation transfer models can be used to quantify UV irradiances at various times and locations, provided that the extraterrestrial solar radiation and the state of the atmosphere are known. Information about UV radiation at the earth's surface is given by the ultraviolet index ,UVI', which is defined as the effective integrated irradiance (280,400 nm) weighted by the erythemal action spectrum. The UV Index is widely used by many international weather services as an indicator of UV levels at the earth's surface providing public awareness of the effects of prolonged exposure to the sun's rays. The aim of this paper is to present a device capable of estimating the UV Index. This device is a compact disc, used as a sundial, and is based on modelled UV irradiances derived from the STAR radiative transfer model (System for Transfer of Atmospheric Radiation). The device was tested in an urban setting under clear sky conditions. Copyright © 2003 Royal Meteorological Society [source] Dust mass-loss rates from asymptotic giant branch stars in the Fornax and Sagittarius dwarf spheroidal galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008Eric Lagadec ABSTRACT To study the effect of metallicity on the mass-loss rate of asymptotic giant branch (AGB) stars, we have conducted mid-infrared photometric measurements of such stars in the Sagittarius and Fornax dwarf spheroidal galaxies with the 10-,m camera VISIR at the Very Large Telescope. We derive mass-loss rates for 29 AGB stars in Sgr dSph and two in Fornax. The dust mass-loss rates are estimated from the K,[9] and K,[11] colours. Radiative transfer models are used to check the consistency of the method. Published IRAS and Spitzer data confirm that the same tight correlation between K,[12] colour and dust mass-loss rates is observed for AGB stars from galaxies with different metallicities, i.e., the Galaxy, the Large Magellanic Clouds and the Small Magellanic Clouds. The derived dust mass-loss rates are in the range 5 × 10,10 to 3 × 10,8 M, yr,1 for the observed AGB stars in Sgr dSph and around 5 × 10,9 M, yr,1 for those in Fornax; while values obtained with the two different methods are of the same order of magnitude. The mass-loss rates for these stars are higher than the nuclear burning rates, so they will terminate their AGB phase by the depletion of their stellar mantles before their core can grow significantly. Some observed stars have lower mass-loss rates than the minimum value predicted by theoretical models. [source] Mouse Strain and Injection Site are Crucial for Detecting Linked Suppression in Transplant Recipients by Trans-Vivo DTH AssayAMERICAN JOURNAL OF TRANSPLANTATION, Issue 2 2007W.J. Burlingham Chemokine-driven accumulation of lymphocytes, mononuclear and polymorphonuclear proinflammatory cells in antigenic tissue sites is a key feature of several types of T-cell-dependent autoimmunity and transplant rejection pathology. It is now clear that the immune system expends considerable energy to control this process, exemplified by the sequential layers of regulatory cell input, both innate and adaptive, designed to prevent a classical Type IV or ,delayed-type' hypersensitivity (DTH) reaction from occurring in the visual field of the eye. Yet, despite an abundance of in vitro assays currently available to the human T-cell immunologist, none of them adequately models the human DTH response and its various control features. The theme of this article is that it is relatively easy to model the effector side of the human DTH response with xenogeneic adoptive transfer models. However, we show that in order to detect inhibition of a recall DTH in response to colocalized donor antigen (linked suppression),a characteristic feature of peripheral tolerance to an organ transplant,both the challenge site and the immunocompetence of the mouse adoptive host are critical factors limiting the sensitivity of the trans-vivo DTH test. [source] Deletion of either CD55 or CD97 ameliorates arthritis in mouse modelsARTHRITIS & RHEUMATISM, Issue 4 2010Robert M. Hoek Objective CD55 (decay-accelerating factor) is best known for its role in the negative regulation of the complement system. Indeed, lack of this molecule leads to disease aggravation in many autoimmune disease models. However, CD55 is abundantly present on fibroblast-like synoviocytes and is also a ligand of the adhesion-class heptahelical receptor CD97, which is expressed by infiltrating macrophages. Treatment with antibodies to CD97 ameliorates the collagen-induced model of rheumatoid arthritis (RA) in DBA/1 mice, but the net contribution of CD55 is unknown. This study was undertaken to investigate the role of CD55 in experimental RA. Methods Arthritis was induced in wild-type, CD55,/,, and CD97,/, mice using collagen-induced and K/BxN serum,transfer models. Incidence of arthritis was monitored over time, and disease activity was assessed by clinical and immunohistochemical evaluation. Results In contrast to observations in many inflammatory disease models, lack of CD55 resulted in decreased arthritis in experimental models of RA. Consistent with the previously reported effects of anti-CD97 antibody treatment, CD97,/, mice had reduced arthritis activity compared with wild-type controls. Conclusion Our findings indicate that the lack of CD55 or CD97 in 2 different models of arthritis increases resistance to the disease. These findings provide insight into a role for CD55 interaction with CD97 in the pathogenesis of RA and suggest that therapeutic strategies that disrupt CD55/CD97 may be clinically beneficial. [source] Dynamic simulation of kinetics, heat and mass transfer during hydrogen sorption by LaNi5ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010Dr Tarek Moustafa Abstract A two-dimensional transient heat and mass transfer models have been developed to investigate the dynamic phenomena of hydrogen absorption and desorption in metal hydride bed. LaNi5 has been chosen as the alloy used for hydrogen storage. The numerical simulation has been conducted to simulate the time,space evolution of temperature, fractional conversion, hydrogen pressure and velocity, in addition to metal density. A correlation for the volumetric reaction rate has been deduced. Also, comparisons have been done between various bed geometries and their influence on the average hydrogen desorbed mass. The simulation results showed that heat transfer controls the overall rate of absorption and desorption processes, and because the driving force for the hydrogen flow is the axial pressure difference; the challenge to get optimum bed geometry is in compromising between heat transfer and pressure drop limitations. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||||||||