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Search Results: 1 - 10 of 206718 matches for " Nelson P.; "
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The Outcome of Surgery versus Medical Management in the Treatment of Vesicoureteral Reflux
Caleb P. Nelson
Advances in Urology , 2008, DOI: 10.1155/2008/437560
Abstract: Evaluation of the relative merits of medical versus surgical management of vesicoureteral reflux (VUR) has been limited by the few prospective studies comparing these strategies. Among those trials that have been reported, the only consistent positive finding has been that incidence of febrile UTI is lower among children undergoing surgical treatment in comparison with medical treatment. Studies have not found significant differences in overall incidence of UTI, or in rates of new renal scarring or progression of existing scarring. It is likely that there is a subset of children with VUR who do benefit from aggressive treatment of their VUR, but we are not yet able to fully determine which children these are. It is hoped that future research will further clarify which treatments are useful in which children.
What is Learned from Longitudinal Studies of Advertising and Youth Drinking and Smoking? A Critical Assessment
Jon P. Nelson
International Journal of Environmental Research and Public Health , 2010, DOI: 10.3390/ijerph7030870
Abstract: This paper assesses the methodology employed in longitudinal studies of advertising and youth drinking and smoking behaviors. These studies often are given a causal interpretation in the psychology and public health literatures. Four issues are examined from the perspective of econometrics. First, specification and validation of empirical models. Second, empirical issues associated with measures of advertising receptivity and exposure. Third, potential endogeneity of receptivity and exposure variables. Fourth, sample selection bias in baseline and follow-up surveys. Longitudinal studies reviewed include 20 studies of youth drinking and 26 studies of youth smoking. Substantial shortcomings are found in the studies, which preclude a causal interpretation.
A Review on Some Chemical Engineering and Microbiological Aspects Considered in the Production of Highly Concentrated Probiotic Cultures and Bacteriocins by Lactococci and Lactobacilli
Nelson Pérez Guerra
ISRN Chemical Engineering , 2012, DOI: 10.5402/2012/836381
Abstract: The main purpose of this work is to give an overview on the chemical engineering aspects related with the production of probiotic cultures and bacteriocins. Firstly, some evidence of the potential of different Lactococci and Lactobacilli strains for prevention or treatment of different human diseases, or as growth promoters in farm animals is given. In addition, examples of different commercial dietary supplements containing probiotic lactoccocci and lactobacilli in combination or not with other probiotic bacteria are presented. Secondly, the main factors (cultivation method, culture media, and media composition) affecting the production of bacteriocins by lactoccocci and lactobacilli strains are showed. Examples of modelling procedures developed to describe the production of higher concentrations of biomass and bacteriocins in fed-batch cultures subjected or not to successive alkalizations are summarized. Finally, the corresponding mass balance equations performed in the latter cultures are presented to calculate the volumes of feeding substrates and the concentrations of nutrients (lactose, glucose, proteins, nitrogen, and phosphorous) added to the fermentation medium, as well as the concentrations of biomass and products in the fermentor just after each feeding. 1. Main Characteristics of Probiotics Probiotics are viable microorganisms that, once ingested in sufficient amounts, exert health-promoting effects in humans and animals by assisting in the establishment of an intestinal population which is beneficial to the host entity and antagonistic to harmful bacteria [1–4]. This beneficial effect is commonly related with the elimination of pathogens by stimulating the immune system, by colonizing the gut in large numbers (competitive exclusion), and/or by the production of antimicrobial substances, including organic acids and bacteriocins [5, 6]. Thus, since the extensive use of antimicrobials (e.g., antibiotics and silver sulphadiazine) could produce adverse reactions and side effects [7, 8], the interest has been focussed on the use of probiotics for preventing or treating different human diseases [1, 4] and for improving the performance parameters of farm animals. These probiotics can play an important role in immunological, digestive, and respiratory functions in humans [9] and can improve the body weight gain and feed conversion in farm animals [2, 3]. The probiotic strains must be: (i) safe, noninvasive, nonpathogenic, nontoxic, and noncarcinogenic; (ii) resistant to gastric acidity and bile toxicity, which is an important characteristic for
Renormalization of Chiral Couplings in Tilted Bilayer Membranes
P. Nelson,T. Powers
Physics , 1993,
Abstract: We study the effects of chiral constituent molecules on the macroscopic shapes attained by lipid bilayer membranes. Such fluid membranes are beautiful examples of statistical ensembles of random shapes, sometimes coupled to in-plane order. We analyze them with methods of continuum elasticity theory, generalizing the well-known Canham-Helfrich model, and in particular incorporate the effects of thermal fluctuations. The condition that coordinate choice be immaterial greatly constrains the possible forms of the statistical weights in these systems, leading to very few independent couplings and hence physically simple models. Thermal fluctuations effectively reduce the chirality of a membrane at long scales, leading to an anomalous scaling relation for the radius of bilayer tubules and helices as a function of chirality. En route to this conclusion we develop a perturbative calculation scheme, paying particular attention to the functional measure needed to describe fluctuations covariantly. %% [In the new version some TeX problems are fixed. This file was prepared with uufiles. To print it, clip out everything after the line of #'s below and put it in an executable file. If your mailer puts a spurious blank line at the end of part one, be sure to kill it. Then execute it to create a TeX file and four .eps files. The latter will be automatically included using epsf.tex. If this doesn't work, please contact the authors.]
Minimizing postulation in a senior undergraduate course in electromagnetism
Nelson P. Andion
Physics , 1998,
Abstract: An approach to the teaching of electromagnetism to senior undergraduate students, designed for overcoming the fragmentation of the theory is described. As usual it starts from the static case, but it is strictly based on Helmholtz theorem of uniqueness of vector fields, on primary experimental observations upon the sources of electric and magnetic fields, on Lenz's law and on principles of superposition and reciprocity of interactions. Thereafter, without further postulation, all laws and rules arise in a procedure where electricity and magnetism parallel one another. Maxwell's equations are built up on a step-by-step basis, showing that electromagnetic field can be considered but a twofold linear vector field obeying the simplest principles of physical theories. It is shown that every system of units fits this formalism, provided suitable values are assigned to some constants arising therein from superposition principle.
A definition of the coupled-product for multivariate coupled-exponentials
Kenric P. Nelson
Physics , 2014, DOI: 10.1016/j.physa.2014.12.023
Abstract: The coupled-product and coupled-exponential of the generalized calculus of nonextensive statistical mechanics are defined for multivariate functions. The nonlinear statistical coupling is indexed such that k_d = k/(1+dk), where d is the dimensions of the argument of the multivariate coupled-exponential. The coupled-Gaussian distribution is defined such that the argument of the coupled-exponential depends on the coupled-moments but not the coupling parameter. The multivariate version of the coupled-product is defined such that the output dimensions are the sum of the input dimensions. This enables construction of the multivariate coupled-Gaussian from univariate coupled-Gaussians. The resulting construction forms a model of coupling between distributions, generalizing the product of independent Gaussians.
Reducing Nitrogen Loss in Subsurface Tile Drainage Water with Managed Drainage and Polymer-Coated Urea in a River Bottom Soil  [PDF]
Patrick R. Nash, Kelly A. Nelson, Peter P. Motavalli
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.611093
Abstract:

Poorly-drained, river bottom soils can be high corn (Zea mays L.) yielding environments, but saturated soil conditions often reduce corn yields. Wabash soils located in river bottoms in Northeast Missouri have not been traditionally tile drained due to high clay content which requires narrow tile drain spacings. Increased land prices in the region have increased interest in tile draining poorly-drained bottom land soils to increase corn yields which could have a deleterious effect on water quality. The objectives of the three-year study were to determine whether use of managed subsurface drainage (MD) in combination with a controlled release N fertilizer could reduce the annual amount of NO3--N loss through tile drainage water compared to free subsurface drainage (FD) with a non-coated urea application. Annual NO3--N loss through tile drainage water with FD ranged from 28.3 to 90.1 kg·N·ha-1. Nitrogen fertilizer source did not affect NO3--N loss through tile drainage water, which was likely due to limited corn uptake over the three-year study due to adverse weather conditions. Averaged over three years, MD reduced tile water drained 52% and NO3--N loss 29% compared to FD. Reduction in NO3--N loss through tile drainage water with MD compared to FD was due to reduced tile flow during the non-cropping period. Annual flow-weighted mean concentration of NO3--N in the tile water was 5.8 mg·N·L-1 with FD and 8.1 mg·N·L-1 with MD. Tile draining river bottom soils at this location for continuous corn production may not pose a health risk over the evaluated duration.

Teletrabalho: que oportunidade de trabalho para o cidad?o incapacitado?
Santana,Silvina; Rocha,Nelson P.;
Análise Psicológica , 2002,
Abstract: the nature of work, as it has been understood, is undergoing a fundamental redefinition. teleworking and computerized remote work constitute the most important manifestations of that redefinition. as a result of the ict evolution, many of the tasks previously accomplished in the factory or in the office can now be done from home, from telecenters or from any place where the worker can have access to the necessary tools. disable citizens have being considered as potential beneficiares of teleworking. however, the subject raises several questions. specifically, it is important to determine companies' willingness to adopt this new work modality, the activities they will consider to pass to external entities and the more appropriated model to adopt, when talking about teleworkers with special needs. on the other hand, it is necessary to determine and analyse perceptions and expectations, in order to manage eventual resistances and provide solutions liable to being adopted and udes efficiently. this work reports the results of a study designed to find answers to these questions. it also allowed finding out the competences potential teleworkers need to have, enabling the progress of training actions and the development of insertion strategies adapted to the teleworkers and to the needs and expectations of employing companies.
Soporte computacional para administración integrada de redes y servicios
Pérez Castillo José Nelson
Ingeniería e Investigación , 1996,
Abstract: Este artículo contextualiza la problemática actual de la administración de redes de comunicaciones considerando las profundas repercusiones, tanto de la internacionalización de la economía como del ritmo impetuoso del avance tecnológico sobre el sector teleinformático y la calidad en la prestación de los servicios de comunicaciones. Rese a someramente las actividades de los distintos frentes de estandarización; en particular la ISO, la ITU- T y la Internet. Se muestran, entonces, las características del soporte computacional para el desarrollo de aplicaciones, se alando los servicios de comunicaciones, interfaz gráfica y bases de datos teniendo en cuenta la naturaleza distribuida de la administración de redes. Finalmente, se muestran los atributos generales de las herramientas de desarrollo disponibles en la actualidad.
Ensayo de insecticidas en la lucha contra el estado adulto de Pachnaeus litus(Germar)en condiciones de laboratorio y de campo.
Felipe Pérez,Nelson Medina
Avanzada Científica , 2010,
Abstract: Se ensayaron los insecticidas Carbaryl 85% PH, Volaton 50% EC, Hostation 50 % EC, Tokutlion 50 % EC y Lebaycid 50% EC,contra el estado adulto de P. litus. En condiciones de laboratorio se emplearon dos métodos (papel de filtro impregnado con las soluciones tóxicas y jaulas de malla plástica con postura de cítricos en el interior).En condiciones de campo se cubrieron las ramas de las plantas seleccionadas con mallas plásticas.La efectividad de los insecticidas empleados se determina mediante la fórmula de Abbout. El Tokutlion presenta mejor efecto biológico que los demás productos ensayados.
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