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Model Supports (model + support)
Selected AbstractsColorimetric investigation of the reaction between p -phenylendiamine and meta -substituted derivatives of benzene on a model supportINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 3 2010M. Scalzo J. Cosmet. Sci., 60, 429,436 (July/August 2009) Synopsis The aim of this work was the employment of colorimetric techniques in the analysis of the color formed, on a proteic substrate, by the reaction between p -phenylendiamine and some meta -substituted benzene derivatives in the presence of hydrogen peroxide and in media at different pH values. In particular we investigated the chromatic variations that take place on the substrate in dependence on different reaction conditions. The obtained results show that for each couple of reagents the colorimetric data, namely the reflectance of the formed color, change considerably with the pH of the reaction medium and demonstrate how this parameter can be considered a good descriptor of the composition of the formed pigment. [source] Quantifying the heterogeneous heat response of Escherichia coli under dynamic temperaturesJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2010E. Van Derlinden Abstract Aims:, Non-sigmoid growth curves of Escherichia coli obtained at constant temperatures near the maximum growth temperature (Tmax) were previously explained by the coexistence of two subpopulations, i.e. a stress-sensitive and a stress-resistant subpopulation. Mathematical simulations with a heterogeneous model support this hypothesis for static experiments at 45°C. In this article, the behaviour of E. coli, when subjected to a linearly increasing temperature crossing Tmax, is studied. Methods and Results:, Subpopulation dynamics are studied by culturing E. coli K12 MG1655 in brain heart infusion broth in a bioreactor. The slowly increasing temperature (°C h,1) starting from 42°C results in growth up to 60°C, a temperature significantly higher than the known Tmax. Given some additional presumptions, mathematical simulations with the heterogeneous model can describe the dynamic experiments rather well. Conclusions:, This study further confirms the existence of a stress-resistant subpopulation and reveals the unexpected growth of E. coli at temperatures significantly higher than Tmax. Significance and Impact of the Study:, The growth of the small stress-resistant subpopulation at unexpectedly high temperatures asks for a revision of currently applied models in food safety and food quality strategies. [source] Solution-State 15N NMR Spectroscopic Study of ,-C-Phycocyanin: Implications for the Structure of the Chromophore-Binding Pocket of the Cyanobacterial Phytochrome Cph1CHEMBIOCHEM, Issue 18 2007Janina Hahn Abstract The detailed structure of the chromophore-binding pocket in phytochrome proteins and the structural changes associated with its photocycle are still matters of debate. Insight into the structure and dynamics of the binding pocket has been gained through the comparison of a 15N NMR spectrum of ,-C-phycocyanin, which is often used as a model system for the study of phytochromes, with the previously described 15N NMR spectrum of the cyanobacterial phytochrome Cph1. The former spectrum supports the hypothesis that all four nitrogen atoms of the ,-C-phycocyanin chromophore are protonated, in analogy with the proposed protonation state for the Pr and Pfr forms of Cph1. The spectra show that the chromophores in both proteins exhibit a distinct dynamic behavior, as also indicated by a NOESY spectrum of Cph1. Finally, stereochemical arguments and a Cph1 homology model support the hypothesis that the chromophore in Cph1 is most likely in the ZZZssa conformation in the Pr form of the protein. [source] CASE STUDIES AND MATHEMATICAL MODELS OF ECOLOGICAL SPECIATION.EVOLUTION, Issue 10 2009We build a spatial individual-based multilocus model of homoploid hybrid speciation tailored for a tentative case of hybrid origin of Heliconius heurippa from H. melpomene and H. cydno in South America. Our model attempts to account for empirical patterns and data on genetic incompatibility, mating preferences and selection by predation (both based on coloration patterns), habitat preference, and local adaptation for all three Heliconius species. Using this model, we study the likelihood of recombinational speciation and identify the effects of various ecological and genetic parameters on the dynamics, patterns, and consequences of hybrid ecological speciation. Overall, our model supports the possibility of hybrid origin of H. heurippa under certain conditions. The most plausible scenario would include hybridization between H. melpomene and H. cydno in an area geographically isolated from the rest of both parental species with subsequent long-lasting geographic isolation of the new hybrid species, followed by changes in the species ranges, the secondary contact, and disappearance of H. melpomene -type ecomorph in the hybrid species. However, much more work (both empirical and theoretical) is necessary to be able to make more definite conclusions on the importance of homoploid hybrid speciation in animals. [source] Social and trauma-related pathways leading to psychological distress and functional limitations four years after the humanitarian emergency in Timor-LesteJOURNAL OF TRAUMATIC STRESS, Issue 1 2010D. Silove There is growing acknowledgment that research in the postconflict field needs to include a focus on social conditions. The authors applied structural equation modeling to epidemiologic data obtained from postconflict Timor-Leste, to examine for links involving potentially traumatic events and sociodemographic factors (age, gender, educational levels, and unemployment) with psychological symptoms and functioning. Exposure to trauma and lack of education emerged as most relevant with psychological distress impacting on education in the urban area. Age and gender exerted influences at different points in the model consistent with the known history of Timor. Although based on cross-sectional data, the model supports the relevance of past trauma, posttraumatic distress, and postconflict social conditions to functioning in societies such as Timor-Leste. [source] The motivating opportunities model for performance SUCCESS: Design, development, and instructional implicationsPERFORMANCE IMPROVEMENT QUARTERLY, Issue 1 2009Patricia L. Hardré This article develops the motivating opportunities model from its previous conceptual framework to its design, development, and instructional implications. It includes building the utility of the model for implementation around the acronym SUCCESS, representing a systematic approach to analyzing and designing motivation for situational, utilization, competence, content, emotional, social, and systemic factors. Furthermore, it details the considerations and questions included in each of the seven components of a process of analysis and design using SUCCESS as a tool and procedural guide. Accompanying each component are specific strategies that support implementation by generating the motivating opportunities that the model supports using, with examples to illustrate cases of use. Following the development and strategies of the model are research questions that may illuminate motivation in instructional design and human performance technology, and the utilization of the model. [source] Project management priorities and the link with performance management systemsPROJECT MANAGEMENT JOURNAL, Issue 4 2007David J. Bryde Abstract This paper reports the results of a project management practices study in the U.K. social housing sector. A five-factor model of project priorities is established, comprising traditional measures of project cost, time, and quality, in combination with a need to focus on stakeholders and to develop a customer and project team orientation. This model supports and integrates previously fragmented notions of project performance measurement. The relationship between these five project management criteria and the effectiveness and use of a performance management system (PMS) is then explored, with some limited evidence found that PMS effectiveness is an antecedent to practices that focus on the customer, the project team members, and other stakeholders [source] Radiative upper-boundary conditions for a non-hydrostatic atmosphereTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 582 2002R. James Purser Abstract A non-hydrostatic compressible model supports vertically propagating acoustic modes in addition to the modes of meteorological significance, such as the quasi-geostrophically balanced, and gravity modes. The acoustic modes are stimulated inadvertently, either by initial conditions incompatibly balanced for the model discretization, or by physical processes injecting abrupt impulses of heat or motion into the model during the integration. A standard method for removing unwanted acoustic energy is through the inclusion in the model of three-dimensional divergence damping. However, an alternative approach is to employ an upper-boundary condition designed to radiate acoustic waves, at least partially, as they impinge on the model top. This note explores this latter option through the use of an upper-boundary condition that incorporates a time filter to facilitate the selective absorption of both gravity and acoustic waves at the top. Copyright © 2002 Royal Meteorological Society [source] Population pharmacokinetics of valproate in Mexican children with epilepsyBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 9 2008Tania Correa Abstract Background. The aim of this study was to determine the factors that influence valproate clearance (CL) in Mexican epileptic pediatric patients using a mixed-effect model and sparse data of serum concentrations of valproic acid (VPA) collected during routine clinical care of patients. Methods. The number of patients included in the study was 110. The population CL was calculated by using the NONMEM program. The following covariates were tested by their influence on CL: total body weight (TBW), height, age, body surface area, daily dose (DD), sex of the patient and comedication with phenobarbital (PB) or carbamazepine. Results. The final regression model for valproic CL found best to describe the data was: CL/F=(0.0466+0.00363 TBW+0.000282 DD) * (1+0.236 PB). This model allows a reduction of 50% of the interindividual variability and of 31% of the residual variability described by the basic model that does not include covariables. Conclusions. Total body weight, daily dose of valproate and concomitant therapy with PB are factors that significantly influence VPA kinetic disposition and they should be considered in programming dosage regimens for this antiepileptic drug in the pediatric population. The validation of the model supports its acceptability for clinical purposes. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||