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System Variables (system + variable)
Selected AbstractsSpatial and temporal evolution of the photo initiation rate for thick polymer systems illuminated on both sidesPOLYMER INTERNATIONAL, Issue 10 2005Nicole Stephenson Abstract Photopolymerizations of thick systems are inherently non-uniform and much more complex than polymerizations of films and coatings. This contribution presents a mathematical description of the evolution of the photoinitiation rate profile for a thick photopolymerization system illuminated on two sides. Simulation results revealed that when two lamps of equal intensity are used, the spatial and temporal evolution of the photoinitiation rate profile follows a characteristic progression from a bimodal distribution to a unimodal shape with a maximum in the center of the sample. The addition of a second light source can lead to an initiation profile that is more uniform throughout the sample. System variables such as the initiator concentration, molar absorptivity and monomer absorptivity determine how the photoinitiation rate profile evolves. For example, increasing initiator concentration results in sharper initiation fronts which move through the sample more slowly. A reflective boundary condition, a special case of two-sided illumination using only one lamp, was found to enhance the initiation rate and uniformity for some reaction systems. This model provides the fundamental understanding needed to ensure proper selection of reaction components for effective photoinitiation in thick systems, including the possibility of a second light source as an additional design variable. Copyright © 2005 Society of Chemical Industry [source] Aeolian fetch distance and secondary airflow effects: the influence of micro-scale variables on meso-scale foredune developmentEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2008Kevin Lynch Abstract Unsuccessful attempts to use process-scale models to predict long-term aeolian sediment transport patterns have long been a feature of aeolian research. It has been proposed that one approach to overcome these problems is to identify micro-scale variables that are important at longer timescales. This paper assesses the contribution of two system variables (secondary airflow patterns and fetch distance) to medium-term (months to years) dune development. The micro-scale importance of these variables had been established during previous work at the site (Magilligan Strand, Northern Ireland). Three methods were employed. First, sand drift potentials were calculated using 2 years of regional wind data and a sediment transport model. Second, wind data and large trench traps (2 m length × 1 m width × 1·5 m depth) were used to assess the actual sediment transport patterns over a 2-month period. Third, a remote-sensing technique for the identification of fetch distance, a saltation impact sensor (Safire) and wind data were utilized to gauge, qualitatively, sediment transport patterns over a 1-month period. Secondary airflow effects were found to play a major role in the sediment flux patterns at these timescales, with measured and predicted rates matching closely during the trench trap study. The results suggest that fetch distance is an unimportant variable at this site. Copyright © 2007 John Wiley & Sons, Ltd. [source] Variation of intraparticle diffusion parameter during adsorption of p -chlorophenol onto activated carbon made from apricot stonesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2003B Koumanova Abstract The adsorption of para -chlorophenol onto an active carbon made from waste apricot stones has been studied. The batch kinetic adsorption processes have been measured for a range of system variables including agitation rate, initial concentration of para -chlorophenol, mass of carbon and particle size of carbon. The extent of adsorption is reported as plots of solid phase concentration against the square root of time. An intraparticle diffusion parameter is used to describe the mass transfer within the adsorbent. This parameter varies with the square root of time and can be related to the type of structure which occurs within an activated carbon. A correlation is proposed relating the process variable with the intraparticle diffusion parameter in each of the three mass transfer regions. Copyright © 2003 Society of Chemical Industry [source] Preparation and HPLC applications of rigid macroporous organic polymer monolithsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10-11 2004Frantisek Svec Abstract Rigid porous polymer monoliths are a new class of materials that emerged in the early 1990s. These monolithic materials are typically prepared using a simple molding process carried out within the confines of a closed mold. For example, polymerization of a mixture comprising monomers, free-radical initiator, and porogenic solvent affords macroporous materials with large through-pores that enable applications in a rapid flow-through mode. The versatility of the preparation technique is demonstrated by its use with hydrophobic, hydrophilic, ionizable, and zwitterionic monomers. Several system variables can be used to control the porous properties of the monolith over a broad range and to mediate the hydrodynamic properties of the monolithic devices. A variety of methods such as direct copolymerization of functional monomers, chemical modification of reactive groups, and grafting of pore surface with selected polymer chains is available for the control of surface chemistry. Since all the mobile phase must flow through the monolith, the convection considerably accelerates mass transport within the molded material, and the monolithic devices perform well, even at very high flow rates. The applications of polymeric monolithic materials are demonstrated mostly on the separations in the HPLC mode, although CEC, gas chromatography, enzyme immobilization, molecular recognition, advanced detection systems, and microfluidic devices are also mentioned. [source] Development of a bulgur-like product using extrusion cookingJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 7 2003Hamit Köksel Abstract In this study we (1) developed a new bulgur-like foodstuff using a durum wheat cultivar and an extrusion technique, (2) investigated the physicochemical properties of the extrudates produced and (3) sensorially evaluated the end-product after cooking. Durum wheat was processed in a laboratory-scale co-rotating twin-screw extruder with different levels of moisture content of the feed (367, 417 and 455,g,kg,1), screw speed (150 and 200,rpm) and feed rate (2.4 and 2.9,kg,h,1) to develop the bulgur-like product. The effects of extrusion conditions on system variables (die pressure and specific mechanical energy (SME)), physical properties (die swell and bulk density), pasting properties (peak, trough and final viscosities) and cooking and sensory properties of the bulgur-like products were determined. The results indicated that increased feed moisture content resulted in significant decreases in the die pressure and SME values of the extruded durum wheat products. As the moisture content and screw speed increased, the changes in die swell values were not significant. The lowest die swell and highest bulk density values were obtained at the highest feed moisture content. The extrusion variables also affected the pasting properties of the extrudates. Significant increases in each of the pasting properties occurred when the moisture content of the feed was increased. Some of the sensory properties (bulkiness, firmness, stickiness and taste,aroma) improved significantly as the feed moisture content increased, indicating better quality. Increased feed moisture content significantly improved cooking quality as determined by a decrease in colorimetric test results. Extrusion seems to be promising for the production of dry, relatively inexpensive bulgur-like products with acceptable sensory properties. © 2003 Society of Chemical Industry [source] Optimal control of innate immune responseOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 2 2002Robert F. Stengel Abstract Treatment of a pathogenic disease process is interpreted as the optimal control of a dynamic system. Evolution of the disease is characterized by a non-linear, fourth-order ordinary differential equation that describes concentrations of pathogens, plasma cells, and antibodies, as well as a numerical indication of patient health. Without control, the dynamic model evidences sub-clinical or clinical decay, chronic stabilization, or unrestrained lethal growth of the pathogen, depending on the initial conditions for the infection. The dynamic equations are controlled by therapeutic agents that affect the rate of change of system variables. Control histories that minimize a quadratic cost function are generated by numerical optimization over a fixed time interval, given otherwise lethal initial conditions. Tradeoffs between cost function weighting of pathogens, organ health, and use of therapeutics are evaluated. Optimal control solutions that defeat the pathogen and preserve organ health are demonstrated for four different approaches to therapy. It is shown that control theory can point the way toward new protocols for treatment and remediation of human diseases. Copyright © 2002 John Wiley & Sons, Ltd. [source] Child-rearing Anxiety and Its Correlates Among Japanese Mothers Screened at 18-Month Infant Health CheckupsPUBLIC HEALTH NURSING, Issue 2 2007Azusa Arimoto ABSTRACT Objective: To examine the level of child-rearing anxiety and to explore the variables correlated with child-rearing anxiety in a city in Japan. Design: Cross-sectional study. Sample: From July to September 2003, 371 mothers who visited community health centers in a city in Tokyo Metropolis for their child's 18-month health checkups. Measurements: Child-rearing anxiety was measured by the child-rearing anxiety scale. Questions in a self-reported questionnaire were on maternal variables, including maternal background information, child variables, and family system variables such as the presence of social support, and utilization of parenting support services. Also included within the questionnaire was the General Health Questionnaire-12. Results: Hierarchical multiple linear regression analysis revealed that mothers with higher child-rearing anxiety had less childcare satisfaction, more depressive symptoms, more worries about the child, less support from the husband, and less social support. Conclusion: To identify mothers with high child-rearing anxiety in Japan, the infant health checkups should be utilized as an opportunity for screening, focusing on variables regarding mothers. Public health nurses can provide the necessary support after gaining an understanding of issues confronting mothers to prevent child-rearing anxiety and child abuse. [source] Body condition does not predict immunocompetence of western pond turtles in altered versus natural habitatsANIMAL CONSERVATION, Issue 3 2010N. Polo-Cavia Abstract Many authors have addressed the relationship between body condition and ecological parameters in a wide range of studies, suggesting a better fitness in those individuals with higher values of body condition. However, body size and body condition of individuals can vary significantly at the intraspecific level between geographic locations, which is usually explained by phenotypic plasticity or local adaptation. We suggest that a higher body condition per se might not be a good indicator of physiological health status, particularly when comparing populations inhabiting places with different levels of habitat alteration. We examined two populations of the western pond turtle Emys marmorata in the northern part of California's Central Valley, and found that individuals inhabiting a water pollution control plant located on the valley floor had significantly larger body size and higher body condition than those inhabiting an unaltered natural habitat in the foothills. However, turtles from the water pollution control plant did not show a better health status, estimated by comparisons between two immune system variables: T-cell-mediated immune response and heterophil/lymphocyte ratio. Parameters such as body size and body condition might be misleading indicators of health condition, particularly when they are used to estimate health status of populations from habitats with different levels of alteration. We emphasize the importance of using physiological methods in assessing the conservation state of wildlife populations, rather than relying on biometric indices that might miss important effects of alteration. [source] Constraints to expanding access to health interventions: an empirical analysis and country typologyJOURNAL OF INTERNATIONAL DEVELOPMENT, Issue 1 2003M. Kent Ranson This paper adopts three approaches to classifying countries by level of constraint, in order to inform the choice of strategies for expanding access to health interventions in different contexts. We find substantial heterogeneity across the 84 low-income and (all) sub-Saharan African countries analysed. Poor sub-Saharan African countries are the most highly constrained; Asian countries, in general, less constrained; and the two Asian giants, China and India, consistently fall above the median. Former Soviet Union countries rank low in terms of governance, but high for health systems variables. Only 10 per cent of the total population of the countries included lives in countries with the greatest constraints. The potential applications of the analysis are discussed, as are the limitations of the cross-sectional, macro level approach. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||