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Search Results: 1 - 10 of 340447 matches for " Mark S. Prokop "
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Design of the SNS Normal Conducting Linac RF Control System
Amy Regan,Sung-il Kwon,Tony S. Rohlev,Yi-Ming Wang,Mark S. Prokop,David W. Thomson
Physics , 2000,
Abstract: The Spallation Neutron Source (SNS) is being designed for operation in 2004. The SNS is a 1 GeV machine consisting of a combination normal-conducting and super-conducting linac as well as a ring and target area. The linac front end is a 402.5 MHz RFQ being developed by Lawrence Berkeley Lab. The DTL (at 402.5 MHz) and the CCL (at 805 MHz) stages are being developed by Los Alamos National Laboratory. The expected output energy of the DTL is 87 MeV and that of the CCL is 185 MeV. The RF control system under development for the linac is based on the Low Energy Demonstration Accelerator (LEDA) control system with some new features. This paper will discuss the new design approach and its benefits. Block diagrams and circuit specifics will be addressed. The normal conducting RF control system will be described in detail with references to the super-conducting control system where appropriate.
Developing an objective function to characterize the tradeoffs in salting out and the foam and droplet fractionation processes
Cherry J.,Ko S.,Grainger R.,Prokop A.
Brazilian Journal of Chemical Engineering , 2000,
Abstract: There are many methods for separating and purifying proteins from dilute solutions, such as salting out/precipitation, adsorption/chromatography, foam fractionation, and droplet fractionation. In order to determine the optimal condition for a selected separation and purification process, an objective function is developed. The objective function consists of three parameters, which are the protein mass recovery, the separation ratio, and the enzymatic activity ratio. In this paper the objective function is determined as a function of the pH of the bulk solution for egg albumin, cellulase, and sporamin (for foam fractionation) and invertase ( for droplet fractionation). It is found that the optimal pH for all the systems except for cellulase is near their isoelectric point.
Differential Mechanisms of Activation of the Ang Peptide Receptors AT1, AT2, and MAS: Using In Silico Techniques to Differentiate the Three Receptors
Jeremy W. Prokop, Robson A. S. Santos, Amy Milsted
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0065307
Abstract: The renin-angiotensin system is involved in multiple conditions ranging from cardiovascular disorders to cancer. Components of the pathway, including ACE, renin and angiotensin receptors are targets for disease treatment. This study addresses three receptors of the pathway: AT1, AT2, and MAS and how the receptors are similar and differ in activation by angiotensin peptides. Combining biochemical and amino acid variation data with multiple species sequence alignments, structural models, and docking site predictions allows for visualization of how angiotensin peptides may bind and activate the receptors; allowing identification of conserved and variant mechanisms in the receptors. MAS differs from AT1 favoring Ang-(1–7) and not Ang II binding, while AT2 recently has been suggested to preferentially bind Ang III. A new model of Ang peptide binding to AT1 and AT2 is proposed that correlates data from site directed mutagenesis and photolabled experiments that were previously considered conflicting. Ang II binds AT1 and AT2 through a conserved initial binding mode involving amino acids 111 (consensus 325) of AT1 (Asn) interacting with Tyr (4) of Ang II and 199 and 256 (consensus 512 and 621, a Lys and His respectively) interacting with Phe (8) of Ang II. In MAS these sites are not conserved, leading to differential binding and activation by Ang-(1–7). In both AT1 and AT2, the Ang II peptide may internalize through Phe (8) of Ang II propagating through the receptors’ conserved aromatic amino acids to the final photolabled positioning relative to either AT1 (amino acid 294, Asn, consensus 725) or AT2 (138, Leu, consensus 336). Understanding receptor activation provides valuable information for drug design and identification of other receptors that can potentially bind Ang peptides.
SNS Superconducting Cavity Modeling -Iterative Learning Control
Sung-il Kwon,Yi-Ming Wang,Amy Regan,Tony Rohlev,Mark Prokop,Dave Thomson
Physics , 2000,
Abstract: The SNS SRF system is operated with a pulsed beam. For the SRF system to track the repetitive reference trajectory, a feedback and a feedforward controllers has been proposed. The feedback controller is to guarantee the closed loop system stability and the feedforward controller is to improve the tracking performance for the repetitive reference trajectory and to suppress the repetitive disturbance. As the iteration number increases, the error decreases.
Antifungal Activity of Homoaconitate and Homoisocitrate Analogs
Maria J. Milewska,Marta Prokop,Iwona Gabriel,Marek Wojciechowski,S?awomir Milewski
Molecules , 2012, DOI: 10.3390/molecules171214022
Abstract: Thirteen structural analogs of two initial intermediates of the L-a-aminoadipate pathway of L-lysine biosynthesis in fungi have been designed and synthesized, including fluoro- and epoxy-derivatives of homoaconitate and homoisocitrate. Some of the obtained compounds exhibited at milimolar range moderate enzyme inhibitory properties against homoaconitase and/or homoisocitrate dehydrogenase of Candida albicans. The structural basis for homoisocitrate dehydrogenase inhibition was revealed by molecular modeling of the enzyme-inhibitor complex. On the other hand, the trimethyl ester forms of some of the novel compounds exhibited antifungal effects. The highest antifungal activity was found for trimethyl trans-homoaconitate, which inhibited growth of some human pathogenic yeasts with minimal inhibitory concentration (MIC) values of 16–32 mg/mL.
Drosophila as a genetic and cellular model for studies on axonal growth
Natalia Sánchez-Soriano, Guy Tear, Paul Whitington, Andreas Prokop
Neural Development , 2007, DOI: 10.1186/1749-8104-2-9
Abstract: The function of a nervous system depends on the proper arrangement of its cellular elements, that is, neurons and glia cells. Amongst these, neurons bear axonal processes that establish synaptic contacts with other cells (neurons, muscles or gland cells) that can be a significant distance away. The transfer of information between these cells is the key feature of nervous system function and is usually mediated by action potentials that propagate along axons and are passed on to other cells at synapses. The wiring of such a system has to be precise and reproducible from individual to individual, as was first highlighted by Ramón y Cajal for the nervous systems of humans, other vertebrates, and also invertebrates [1]. Such precision is achieved during development through the guided growth of axons along specific paths, a process clearly governed by genetic mechanisms [2,3].Essential work contributing to our current understanding of axonal growth has been carried out in vertebrates and invertebrates alike, in many instances demonstrating the conservation of principal mechanisms across the animal kingdom. One strategy towards improving molecular insights into axonal growth is the use of genetically tractable invertebrate model organisms, such as the worm Caenorhabditis elegans or the fruit fly Drosophila melanogaster. The strength of these species lies in their amenability to genetic manipulation (see below) and the fact that their nervous systems are composed of relatively low numbers of cellular elements. Whereas specific neuronal connections in vertebrates are usually formed by larger groups of neurons that develop and act in parallel, these connections are mostly represented by unique, individually recognisable neurons in invertebrates. Studies capitalising on such identifiable neurons, for example in insects, have helped to unravel principles of neuronal circuit formation. For example, the initial observation of guidepost cells as stepping stones for axonal growth
Developing an objective function to characterize the tradeoffs in salting out and the foam and droplet fractionation processes
Cherry, J.;Ko, S.;Grainger, R.;Prokop, A.;Tanner, R. D.;
Brazilian Journal of Chemical Engineering , 2000, DOI: 10.1590/S0104-66322000000200011
Abstract: there are many methods for separating and purifying proteins from dilute solutions, such as salting out/precipitation, adsorption/chromatography, foam fractionation, and droplet fractionation. in order to determine the optimal condition for a selected separation and purification process, an objective function is developed. the objective function consists of three parameters, which are the protein mass recovery, the separation ratio, and the enzymatic activity ratio. in this paper the objective function is determined as a function of the ph of the bulk solution for egg albumin, cellulase, and sporamin (for foam fractionation) and invertase ( for droplet fractionation). it is found that the optimal ph for all the systems except for cellulase is near their isoelectric point.
Swimming Upstream: Faculty and Staff Members From Urban Middle Schools in Low-Income Communities Describe Their Experience Implementing Nutrition and Physical Activity Initiatives
Katherine W. Bauer, SM,Aarti Patel,Lisa A. Prokop,S. Bryn Austin, ScD
Preventing Chronic Disease , 2006,
Abstract: Introduction Addressing childhood overweight has become a top priority in the United States. Modification of school policies and practices has been used in an attempt to address the overweight epidemic among children and adolescents. Culturally diverse urban schools in low-income communities attempting to improve nutrition and increase physical activity may face unique challenges in the school environment. A better understanding is needed about school environments and how they may affect the implementation, efficacy, and sustainability of initiatives designed to improve nutrition and physical activity. Methods We carried out a qualitative study in five urban middle schools in low-income communities that had recently implemented Planet Health, a nutrition and physical activity intervention, to assess which aspects of the schools’ physical, social, and policy environments were facilitating or impeding the implementation of health promotion initiatives. Thirty-five faculty and staff members participated. We conducted one focus group per school, with an average of seven participants per group. We analyzed focus group transcripts using the thematic analysis technique to identify key concepts, categories, and themes. Results Teachers and staff members in our study identified many school-related environmental barriers to successful implementation of nutrition and physical activity initiatives in their schools. School personnel recommended that classroom-based nutrition interventions such as Planet Health be coordinated with school food services so that the healthy messages taught in the classroom are reinforced by the availability of healthy, culturally appropriate cafeteria food. They identified household food insufficiency and overly restrictive eligibility criteria of the federally subsidized meal program as critical barriers to healthy nutritional behaviors. They also identified weight-related teasing and bullying and unhealthy weight-control behaviors as challenges to promotion of healthy nutrition and physical activity. Conclusion To maximize intervention efforts, researchers and practitioners must consider the effects of school environments on nutrition and physical activity initiatives.
Screening High School Students for Eating Disorders: Results of a National Initiative
S. Bryn Austin, ScD,Najat J. Ziyadeh, MPH,Sara Forman, MD,Lisa A. Prokop, BA
Preventing Chronic Disease , 2008,
Abstract: IntroductionEarly identification and treatment of disordered eating and weight control behaviors may prevent progression and reduce the risk of chronic health consequences.MethodsThe National Eating Disorders Screening Program coordinated the first-ever nationwide eating disorders screening initiative for high schools in the United States in 2000. Students completed a self-report screening questionnaire that included the Eating Attitudes Test (EAT-26) and items on vomiting or exercising to control weight, binge eating, and history of treatment for eating disorders. Multivariate regression analyses examined sex and racial/ethnic differences.ResultsAlmost 15% of girls and 4% of boys scored at or above the threshold of 20 on the EAT-26, which indicated a possible eating disorder. Among girls, we observed few significant differences between ethnic groups in eating disorder symptoms, whereas among boys, more African American, American Indian, Asian/Pacific Islander, and Latino boys reported symptoms than did white boys. Overall, 25% of girls and 11% of boys reported disordered eating and weight control symptoms severe enough to warrant clinical evaluation. Of these symptomatic students, few reported that they had ever received treatment.ConclusionPopulation screening for eating disorders in high schools may identify at-risk students who would benefit from early intervention, which could prevent acute and long-term complications of disordered eating and weight control behaviors.
Reducing of CO2 emissions and its depositing into underground
Jaroslava Koudelková,Pavel Prokop
Acta Montanistica Slovaca , 2005,
Abstract: Increasing CO2 emissions caused especially by the combustion of fossil fuels rises a question of how this can be problem solved in the long term. There is several solutions which differ technically and financially. This paper deals with the CO2 capture from combustion processes or power plant processes, (CO2 can be captured from the flue gas, after combustion in oxygen and recirculated flue gas or from a synthesis gas before combustion). This paper presents possibilities of CO2 storagex captured in this way into underground (deep ocean, oil and gas fields, coal bed, aquifers).
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