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On the misuse of Prigogine's Global Formulation of the Second Law and the Prediction of Negative Entropy Production in Macroscopic Irreversible Processes
Pedro J. Colmenares
Avances en Química , 2008,
Abstract: This article presents thermodynamic and statistical mechanics arguments to proof the impossibility of a proposal1 in which the interplay of production and destruction entropy processes would explain why it is possible to do work more efficiently in an irreversible process than in a reversible one between the same initial and final states. We clarify all the thermodynamic misleading and, provide theoretical and experimental evidence2 that, a macroscopic level of description, the proposal has no chance of being observed phenomenologically because of the restrictions imposed by the second law of thermodynamics.
On the Scaling of Langevin and Molecular Dynamics Persistence Times of Non-Homogeneous Fluids
Wilmer Olivares-Rivas,Pedro J. Colmenares
Physics , 2011, DOI: 10.1103/PhysRevE.85.011117
Abstract: The solution of the Langevin equation of an anisotropic fluid [Colmenares P. J; L\'opez F. and Olivares-Rivas W., Phys. Rev E. 2009, 80061123] allowed the evaluation of the position dependent perpendicular and parallel diffusion coefficients, using Molecular Dynamics data. However, the time scale of the Langevin Dynamics and Molecular Dynamics are different and an anzat for the persistence probability relaxation time was needed. Here we show how the solution for the average persistence probability obtained from the Smoluchowski-Fokker-Planck equation (SE), associated to the Langevin Dynamics, scales with the corresponding Molecular Dynamics quantity. Our SE perpendicular persistence time is evaluated in terms of simple integrals over the equilibrium local density. When properly scaled by the perpendicular diffusion coefficient, it gives a good match with that obtained from Molecular Dynamics.
The generalized Langevin equation revisited: Analytical expressions for the persistence dynamics of a viscous fluid under a time dependent external force
Wilmer Olivares-Rivas,Pedro J. Colmenares
Physics , 2015,
Abstract: The non--static generalized Langevin equation and its corresponding Fokker--Planck equation for the position of a viscous fluid particle was solved in closed form for a time dependent external force. Its solution for a constant external force was obtained analytically. The non--Markovian stochastic differential equation, associated to the dynamics of the position under a colored noise, was then applied to the description of the dynamics and persistence time of particles constrained within absorbing barriers. Comparisons with molecular dynamics were very satisfactory.
SEROPREVALENCIA DE HEPATITIS B EN EL TOCUYO ESTADO LARA: NUEVA ZONA DE RIESGO?
Vizcaya Teodoro,González Floreima,Colmenares Pedro,Gutiérrez Oscar
Salud, Arte y Cuidado , 2011,
Abstract: The Hepatitis B virus (HBV) is one of the DNA Hepadnaviridae family. The mechanisms of transmission are sexual, perinatal and parenteral ones. The subjects suffering from the infection at an early age remain asymptomatic during the acute phase; but they have an increased risk of becoming chronic carriers of the disease. The objective of this study was determine the prevalence of seropositivity for Hepatitis B of donors attending voluntarily the blood bank at the Hospital “Dr. Egidio Montesinos” from El Tocuyo, discriminated against by age, gender and origin. A sample of 9344 serums were studied to detect antibodies against the surface antigen (antiHBsAg) and core antigen (antiHBcAg) of HBV. They were analyzed in the laboratory of the aforementioned Hospital, through an inmunoassay method of microparticles of third generation. The percentage prevalence for serumpositive cases was calculated and was stratified by age, sex and origin of the positive donor. The most common causes for rejection or deferral as a donor were also calculated. A seroprevalence of 7,87 was obtained. The rate by gender 10/9 prevailing the male. The rate for seropositive men was 9.8 greater than women and an age group with higher seropositivity for the 36 to 40 age group. Conclusion: the results of this study suggest a high prevalence of Hepatitis B among donors who attended to this service, which is catalogued as high or risk. This situation is atypical for the region which equated it to other endemic areas of the country.
Approach of RSOR Algorithm Using HSV Color Model for Nude Detection in Digital Images
Pedro Ivan Tello Flores,Luis Enrique Colmenares Guillén,Omar Ariosto Ni?o Prieto
Computer and Information Science , 2011, DOI: 10.5539/cis.v4n4p29
Abstract: This paper analyzes the application of pixel segmentation techniques, the recognition and selection of image regions, as well as the performing of operations on the regions found within the digital images in order to detect nudity. The research aims to develop a software tool capable of nudity detection on digital images. The segmentation in the HSV color model (Hue, Saturation, and Value) to locate and remove the pixels corresponding to human skin is used. The algorithm in Recognition, Selection and Operations in Regions (RSOR), to recognize and separate the region with the highest number of skin pixels within the segmented image (largest region), is proposed. Once selected the largest region, the RSOR algorithm calculates the percentage on the segmented image taken from the original one, and then it calculates the percentage on the largest region, in order to identify whether there is a nude in the image. The criteria for appraising if an image depicts a nude is the following: If the percentage of skin pixels in the segmented image, in comparison to the original image, is less than 25% it is not considered a nude, but if it exceeds this percentage, then, the image is a nude. However, when the percentage of the largest region has been estimated and it amounts to less than 35%, the image is definitely not a nude. The final result is a message that informs the user whether or not the image is a nude. The RSOR algorithm obtains a 4.7% false positive, compared to other systems, and it has shown to possess optimum performance for nudity detection.
Factores críticos de éxito para implantar sistemas empresariales en peque?as y medianas empresas en Venezuela
Colmenares,Leopoldo;
Universidad, Ciencia y Tecnología , 2008,
Abstract: the main objective of this study was to determine the critical success factor for the implementation of planning systems for enterprise resources in the small and medium venezuelan company. a panel of eight operational consultants was formed of two organizations engaged in the sale and support of such systems who identified fifteen contributing factors to success in the implementation of planning systems of the company?s resources. the factors so identified were classified according to their degree of importance using a likert scale of seven points. the study finds that there is a mixture of technical and managerial factors that have an impact on the success of the project. examples are: establish the goals of the project, implant the system with minimum modifications, the level of technical knowledge of the users, the training offered to the users, and the support of the high management of the company to the project.
Risk factors related to infectious complications in hysterectomized patients: case and control study
Claudia Colmenares
Revista Ciencias de la Salud , 2003,
Abstract: Objectives: To establish the risk factors associatedwith infectious complications after vaginalor abdominal planned hysterectomy. Methodology:Study of cases and controls Place:Gynaecology Department and Septic Unit,Clinica San Pedro Claver, Bogotá, Colombia.SAMPLE: 565 patients (115 cases and 450 controls)who had planned hysterectomy for anybenign or pre-malign cause. The cases weredefined as patients who enter the septic service with diagnosis of any septic condition. Results:Among the analysed risk factors that werestatistically meaningful are the diagnosis ofdiabetes mellitus (OR 6.01 CI: 2.03-18.15),more than 3 deliveries (OR1.73 CI: 1.10-2.73),IUT use(OR3.94 CI: 2.42-6.43), vaginaldischarge (OR 5.13 CI: 3.16-8.33) or presenceof swelling previous to the surgery (OR 3.76IC: 2.37-5.97), and use of prophylactic anticoagulation(OR 3.37 CI: 2.15-5.28) Conclusion:The presence of vaginal discharge and swellingin vaginal cytology are the important predictorsof infectious morbidity that can be correctedprior to the surgery.
Entrevista a Gerardo Ardila Profesor e investigador del Departamento de Antropología y del Centro de Estudios Sociales de la Universidad Nacional de Colombia
Colmenares Rafael
Maguaré , 2002,
Abstract: N.A
An Exploratory Study on the Critical Success Factors in the Implementation of Enterprise Resource Planning Systems in Venezuela
Leopoldo Colmenares
JISTEM - Journal of Information Systems and Technology Management , 2005,
Abstract: This paper reports on an exploratory study, carried out in seven Venezuelan organizations who have successfully implemented an enterprise resource planning (ERP) system. The data were collected by means of both a questionnaire and of conducted interviews to the seven project managers of the project of implementation of ERP systems in these enterprises. The purpose of the study was to know the perceptions the project managers, on aspects and activities of the process of implementing an ERP system and that are strongly correlated with the Critical Success Factors (FCE’s) for this kind of projects. The FCE’s were identified in a deep revision of the literature. The questionnaire included, among others, questions on the top management support to the project, the process of selection of the system, team work implementation and the participation and training of the users. Additionally were identified the problems that organizations confronted during the implementation process. The study concludes that organizations must take care the elements that indicate the FCE’s, because them hit positively the project, additionally describe aspects, which must take into account the enterprises who are in the process to adopt an ERP system to facilitate its implementation.
Tiroidectomía casi total sin lugol en la enfermedad de Graves-Basedow
Colmenares Arreaza,Guillermo; Colmenares Guerra,Guillermo;
Gaceta Médica de Caracas , 2002,
Abstract: the authors analyze a modified surgical treatment of the traditional surgery of graves-basedow hyperthyroidism that started in 1984 and finished in 1994. these changes consisted in not using the iodine preparation lugol as a preoperative medication, it shortened the time of hospitalization making it easier and economical. complications were the same as the traditional method. the second change was a near total thyroidectomy, since it is easier to visualize the laryngeal nerves, parathyroid glands and is bloodless. a small quantity of thyroid gland was left over implying less recurrent hyperthyroidism. the results were: a. laryngeal bilateral paresia (1 case), b. transitory hypoparathyroidism (2 cases), c. hypothyroidism (5 cases), d. recurrent hyperthyroidism none, e. weight of operated gland 55 g. f. exophthalmos? improvement (subjective and objective), g- euthyroidism (11 cases). we concluded that near total thyroidectomy without previous iodine preparation is an alternative in the surgical treatment of graves-basedow disease
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