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Search Results: 1 - 10 of 327473 matches for " Jesús Estévez "
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Active Learning and Dynamic Pricing Policies  [PDF]
María-Jesús Vázquez-Gallo, Macarena Estévez, Santiago Egido
American Journal of Operations Research (AJOR) , 2014, DOI: 10.4236/ajor.2014.42009
Abstract:

In this paper, we address the problem of dynamic pricing to optimize the revenue coming from the sales of a limited inventory in a finite time-horizon. A priori, the demand is assumed to be unknown. The seller must learn on the fly. We first deal with the simplest case, involving only one class of product for sale. Furthermore the general situation is considered with a finite number of product classes for sale. In particular, a case in point is the sale of tickets for events related to culture and leisure; in this case, typically the tickets are sold months before the event, thus, uncertainty over actual demand levels is a very a common occurrence. We propose a heuristic strategy of adaptive dynamic pricing, based on experience gained from the past, taking into account, for each time period, the available inventory, the time remaining to reach the horizon, and the profit made in previous periods. In the computational simulations performed, the demand is updated dynamically based on the prices being offered, as well as on the remaining time and inventory. The simulations show a significant profit over the fixed-price strategy, confirming the practical usefulness of the proposed strategy. We develop a tool allowing us to test different dynamic pricing strategies designed to fit market conditions and seller's objectives, which will facilitate data analysis and decision-making in the face of the problem of dynamic pricing.

Tendencias de cooperación en sectores maduros: El caso del sector agroalimentario espa ol
Pedro Jiménez Estévez,Jesús David Sánchez
Ecos de Economía , 2005,
Abstract: Los acuerdos de cooperación se han convertido en una de las prácticas empresariales más utilizadas como consecuencia de los procesos de reestructuración que se están produciendo en un amplio número de sectores. La cooperación empresarial ha sido objeto de estudio en múltiples sectores tecnológicos, sin embargo, no ha sido abordada en los sectores maduros. De este modo, el objetivo de nuestro trabajo es hacer una revisión de la literatura en torno al tema, analizando el concepto de cooperación, sus factores condicionantes, distintas clasificaciones, al mismo tiempo que definiremos la situación estructural del sector agroalimentario espa ol y recogeremos los casos de cooperación en dicho sector aparecidos en dos periódicos económicos espa oles: Cinco Días y Expansión; para mostrar la relevancia actual del tema objeto de estudio
Alteraciones Hepáticas en Pacientes con Dengue Hepatic Alterations in Patients with Dengue
Yraima Larreal,Nereida Valero,Jesús Estévez,Ivette Reyes
Investigación Clínica , 2005,
Abstract: La caracterización clínica del Dengue es muy variable debido a las múltiples alteraciones inducidas por el virus en el organismo. Se ha reportado incremento en los niveles de transaminasas similares a los producidos por el virus de Hepatitis en pacientes con Dengue de zonas hiperendémicas de Asia. Los objetivos del trabajo fueron determinar alteraciones en las pruebas de funcionalismo hepático en pacientes con Dengue y relacionar clínica y serológicamente la infección viral. A 62 casos con confirmación serológica para Dengue, se les realizó historia clínica, hematología completa, Tiempo de Protrombina (TP) y Tiempo Parcial de Tromboplastina (TPT), cuantificación de transaminasas (ALT y AST) y bilirrubina en suero. En relación a las características clínicas el 38,7% de los pacientes con Dengue Clásico (DC) y Fiebre Hemorrágica por Dengue (FHD) refirieron dolor abdominal y 2 con FHD presentaron hepatomegalia e ictericia. En los resultados de laboratorio se observó leucopenia (72,5%) en ambas formas de Dengue y en pacientes con FHD, trombocitopenia severa (<50.000×mm3) y TP y TPT alargados en 70,9%, 23,0% y 42,3%, respectivamente. El valor de transaminasas resultó hasta cinco veces más elevado que el valor normal (p<0,005) en 36,8% de los pacientes con DC y en 74,4% con FHD, con predominio de AST en ambos grupos. Los resultados sugieren da o hepático durante el curso del Dengue. Esto permite afirmar que la infección por virus Dengue puede causar disfunción hepática aguda y debe ser considerada en el diagnóstico diferencial con otras infecciones virales con disfunción hepática. Clinical features of Dengue are very variable due to multiple alterations induced by the virus in the organism. Increased levels of transaminases similar to those produced by the Hepatitis virus have been reported in patients with Dengue from hiperendemic zones in Asia. The objectives of this study were to determine alterations in the liver tests in patients with Dengue and to relate them to the disease, clinically and serologically. Clinical history, hemathological tests serum transaminases (ALT y AST) and bilirubin assays were performed in 62 patients with clinical and serological diagnosis of Dengue. According to clinical features 38.7% of the patients with classical (CD) and hemorrhagic (DHF) forms of Dengue reffered abdominal pain and 2 patients with DHF had ictericia and hepatomegaly. Laboratory test findings showed leucopenia in 72.5% in both forms of Dengue and of patients with DHF severe thrombocytopenia (< 50.000 platelets × mm3), long PT and PPT in 70.9%, 23.0% and 42.3%,
Evaluación de la cooperación empresarial como estrategia competitiva en el sector agroalimentario: El caso espa ol
Jesús David Sánchez de Pablo González del Campo,Pedro Jiménez Estévez
Ecos de Economía , 2008,
Abstract: La necesidad de las empresas de aumentar su dimensión para ser competitivas ante la alta volatilidad del entorno ha provocado la generalización de la cooperación empresarial en los últimos a os. Como consecuencia existen numerosos estudios relativos a dicha estrategia, donde los aspectos más analizados han sido los factores claves de éxito y las ventajas de la cooperación empresarial, destacando los análisis empíricos realizados en sectores intensivos en tecnología. Sin embargo, la cooperación también tiene importantes riesgos asociados, por lo que, nuestro objetivo será realizar un estudio exploratorio donde se analice de forma conjunta los motivos que llevan a las empresas a cooperar y, por tanto, las ventajas que se derivan de la cooperación, y sus riesgos asociados. Frente a los análisis centrados en la cooperación basada en la innovación tecnológica, consideramos necesario aportar información sobre los acuerdos cooperativos en sectores de baja intensidad tecnológica, claves en el empleo y la economía tanto en Espa a, Colombia y demás países con un sector agroalimentario importante.
Prevalence of human toxoplasmosis in san carlos island, venezuela
Chacín-Bonilla,Leonor; Sánchez-Chávez,Yulaicy; Estévez,Jesús; Larreal,Yraima; Molero,Emelyn;
Interciencia , 2003,
Abstract: a survey of 335 individuals, 1-65 years of age (mean ±sd of 20.8 ±15.7), in 6 communities from the san carlos island, western venezuela, was conducted to study the prevalence of serum antibody to toxoplasma gondii. the indirect hemagglutination test showed an overall infection rate of 49.8% (167 of 335) that ranged 23-64.8% according to the locality. no association between antibody status and age or risk factors was detected. higher antibody rates were found in a windward coast community, and lower rates in a rural sector when compared to 3 other localities. higher geometric mean titers were found in the communities with higher antibody rates. toxoplasmosis is prevalent and widely spread in the area. infection by oocysts from cat feces appears to be the predominant mode of transmission and contaminated drinking water seems to play a role in the transmission.
Autescala de Zung para depresión como predictor de la respuesta sensorial y autonómica al dolor
Pi?erúa-Shuhaibar,Lorena; Estévez,Jesús; Suárez-Roca,Heberto;
Investigación Clínica , 2007,
Abstract: clinical and experimental evidence support a relationship between susceptibility to chronic pain and a subjacent depression. nevertheless, it?s not clear if the currently available clinical evaluation instruments for depression allow for linking both disorders. thus, we evaluated a zung?s autoscale for depression and its different categories: affective, physiological, motor and psychological, as possible predictors of sensorial and autonomic alterations and vulnerability to clinical chronic pain. in 32 healthy controls and 11 subjects with minor depression and free of treatment, ischemic pain was first induced by applying a tourniquet on the dominant arm, and then followed by paresthesias during the reperfusion of arm as the tourniquet is released. ischemic muscular pain, post-ischemic paresthesias and associated cardiovascular responses were recorded throughout the experimental procedure. the affective category?s score was correlated linearly in individual form with the greatest number of variables and it was adjusted to a model of multiple regressions that almost explained the variance in 100% with a contribution of the sensorial and autonomic variables of a 70% and 30%, respectively. in addition, the affective category was 50% greater in subjects with persistent clinical pain. the zung?s index and the other categories had a smaller number of individual linear correlations and models of multiple correlations that only explained between 30-70% of the variance, with a more predominant contribution of the autonomic variables (20-50%), especially in the psychological category. this suggests that the affective category predicts cutaneous-muscular sensorial alterations with greater effectiveness than the zung?s total index.
A Cuban perspective on management of persistent vegetative state
Calixto Machado,Mario Estévez,Rafael Rodríguez,Jesús Pérez-Nellar
MEDICC Review , 2012,
Abstract: The Cuban Group for Study of Disorders of Consciousness is developing several research protocols to search for possible preservation of residual brain and autonomic functions in cases of persistent vegetative and minimally conscious states. We present examples showing the importance of 3D anatomic reconstruction of brain structures and MRI tractography for assessing white matter connectivity. We also present results of use of proton magnetic resonance spectroscopy technique to follow up cognitive recovery in persistent vegetative state patients transitioning to minimally conscious state. We have demonstrated recognition of a mother's voice with emotional content after zolpidem administration, indicating high-level residual linguistic processing and brain activation despite the patient's apparent inability to communicate. Hence we differ with current thinking that, by definition, subjects in persistent vegetative state are isolated from the outside world and cannot experience pain and suffering. We also consider "vegetative state" a pejorative term that should be replaced.
Niveles séricos de la molécula CD30 soluble en la infección por el virus de hepatitis B Serum levels of soluble CD30 molecule in hepatitis B virus infection
Francisca Monsalve C,Tania Romero-A,Jesús Estévez M,Luciana Costa L
Revista médica de Chile , 2001,
Abstract: Background: The release of CD30 molecule in the soluble form (sCD30) is considered a feature of Th2 activation and proliferation of the cellular phenotype Th2. Aim: To analyze the immunoregulatory role of sCD30 in the evolution of hepatitis B virus (HBV) infection. Patients and methods: Three study groups were formed: 15 patients with acute infection by HBV who remitted toward the resolution of the infection; 15 patients who evolved to the carrier state and 15 subjects without clinical history of infection by this or other viruses. The determination of serological markers for the HBV was done by the Microparticles Enzymatic Immunoanalysis techniques (MEIA). The method of double antibody by ELISA was used For sCD30 determination. Results: A significant sCD30 increase (p < 0.05) was observed in patients with acute infection, during the acute phase (135.7 ± 36.7). These values decreased to 16.2 ± 2.5 during the convalescent phase. Patients that evolved to the carrier state, did not experience a rise in sCD30 values (40.2 ± 6.7, 38 ± 9.2 and 36.1 ± 8.3 during the acute phase, at 120 and 240 days respectively). The value in the control group was 34.8 ± 6.7. Conclusions: The group that evolved towards remission experienced a higher activation of the Th2 cellular phenotype, promoting humoral immune response. An inactivity of sCD30 values was observed in the group that evolved to the carrier state (Rev Méd Chile 2001; 129: 1248-52).
Diagnóstico etiológico de pacientes con exantemas o cuadros febriles atendidos en 1998: Estado Zulia, Venezuela Laboratory diagnosis of patients with exanthematic or febrile syndromes occurring in the Zulia state, Venezuela, during 1998
Luciana Costa de León,Jesús Estévez,Francisca Monsalve de Castillo,Diana Callejas
Revista médica de Chile , 2004,
Abstract: Background: Exanthematic diseases are a group of syndromes mainly caused by acute viral infections. Aim: To obtain information about the viruses that cause exanthematic diseases in our region. Patients and methods: During 1998, 267 serum samples from patients with an acute rash or patients presenting a febrile syndrome accompanied by enlarged lymph nodes, headache and other symptoms, were collected. Specific antibody of the IgM class (anti-IgM) against Rubella, Measles, Dengue types 1-4 and Cytomegalovirus (CMV) were measured by immunoenzymatic assay (EIA). Epstein-Barr virus (EBV) antibodies were measured by immunofluorescence. Results: An etiologic agent was detected in 208 cases (77.9%). Cases due to Dengue (40,6%) and Rubella (21%) viruses predominated, but the frequency of other agents was also high in specific age groups. The agreement between the clinical suspicion and the laboratory findings varied broadly, from a 100% for suspected Dengue to just a 14,8% for cases of suspected CMV infection. Conclusions: Dengue was the most common viral exanthematic disease in the Zulia State during 1998 (Rev Méd Chile 2004; 132: 1078-84
Seroepidemiología del virus Herpes simplex 2 en una población indígena Yukpa. Estado Zulia. Venezuela Seroepidemiology of Herpes simplex virus type 2 in the Amerindian Yukpa population of Zulia state, Venezuela
Francisca Monsalve C,Jesús Estévez,Luciana Costa L,María Salas A
Revista médica de Chile , 2001,
Abstract: Background: Yukpa aborigines start early in life their sexual activity and promiscuity with native and foreign individuals is common among women. This behavior allows the installation and propagation of Herpes simplex virus type 2 (HSV-2). Aim: To determine the presence of antibodies to HSV-2 in a Yukpa Amerindian community at Zulia State, Venezuela. Subjects and methods: We studied 96 natives, between 13 and 49 years old (62.3% of the whole population, 100% of individuals in fertile age). Control population consisted of 76 individuals, with similar sex and age range distribution, of the urban population from Maracaibo, Zulia State, Venezuela. HSV-2 serologic status was determined by an indirect fluorescent antibody test. Results: Antibodies to HSV-2 were detected in 53.1% of Yukpa population and 21.1% of urban population. Aboriginal women aged 21 to 40 years old had a prevalence of antibodies against HSV-2 of 66.7%. Among pregnant native women, the prevalence of antibodies against HSV-2 was 54.6%. Conclusions: There is a high prevalence of antibodies against HSV-2 among Yukpa natives in Venezuela. (Rev Méd Chile 2001; 129: 247-52).
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