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Search Results: 1 - 10 of 71350 matches for " Jorge X. Velasco-Hernández "
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A model for the A(H1N1) epidemic in Mexico, including social isolation
Velasco-Hernández,Jorge X; Leite,Maria Conceicao A;
Salud Pública de México , 2011, DOI: 10.1590/S0036-36342011000100007
Abstract: objective: we present a model for the 2009 influenza epidemic in mexico to describe the observed pattern of the epidemic from march through the end of august (before the onset of the expected winter epidemic) in terms of the reproduction number and social isolation measures. material and methods: the model uses a system of ordinary differential equations. computer simulations are performed to optimize trajectories as a function of parameters. results: we report on the theoretical consequences of social isolation using published estimates of the basic reproduction number. the comparison with actual data provides a reasonable good fit. conclusions: the pattern of the epidemic outbreak in mexico is characterized by two peaks resulting from the application of very drastic social isolation measures and other prophylactic measures that lasted for about two weeks. our model is capable of reproducing the observed pattern.
Towards Uncertainty Quantification and Inference in the stochastic SIR Epidemic Model
Marcos A. Capistrán,J. Andrés Christen,Jorge X. Velasco-Hernández
Statistics , 2011,
Abstract: In this paper we introduce a novel method to conduct inference with models defined through a continuous-time Markov process, and we apply these results to a classical stochastic SIR model as a case study. Using the inverse-size expansion of van Kampen we obtain approximations for first and second moments for the state variables. These approximate moments are in turn matched to the moments of an inputed generic discrete distribution aimed at generating an approximate likelihood that is valid both for low count or high count data. We conduct a full Bayesian inference to estimate epidemic parameters using informative priors. Excellent estimations and predictions are obtained both in a synthetic data scenario and in two Dengue fever case studies.
Intraguild Predation on the Whitefly Parasitoid Eretmocerus eremicus by the Generalist Predator Geocoris punctipes: A Behavioral Approach
María Concepción Velasco-Hernández, Ricardo Ramirez-Romero, Lizette Cicero, Claudia Michel-Rios, Nicolas Desneux
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080679
Abstract: Intraguild predation (IGP) takes place when natural enemies that use similar resources attack each other. The impact of IGP on biological control can be significant if the survival of natural enemy species is disrupted. In the present study, we assessed whether Geocoris punctipes (Hemiptera: Lygaeidae) engages in IGP on Eretmocerus eremicus (Hymenoptera: Aphelinidae) while developing on whitefly nymphs of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). In choice and non-choice tests, we exposed G. punctipes to parasitized and non-parasitized whitefly nymphs. We found that G. punctipes does practice IGP on E. eremicus. However, choice tests assessing G. punctipes consumption revealed a significant preference for non-parasitized T. vaporariorum nymphs. Subsequently, we investigated whether E. eremicus females modify their foraging behavior when exposed to conditions involving IGP risk. To assess this, we analyzed wasp foraging behavior under the following treatments: i) whitefly nymphs only (control = C), ii) whitefly nymphs previously exposed to a predator ( = PEP) and, iii) whitefly nymphs and presence of a predator ( = PP). In non-choice tests we found that E. eremicus did not significantly modify its number of attacks, attack duration, oviposition duration, or behavior sequences. However, E. eremicus oviposited significantly more eggs in the PEP treatment. In the PP treatment, G. punctipes also preyed upon adult E. eremicus wasps, significantly reducing their number of ovipositions and residence time. When the wasps were studied under choice tests, in which they were exposed simultaneously to all three treatments, the number of attacks and frequency of selection were similar under all treatments. These results indicate that under IGP risk, E. eremicus maintains several behavioral traits, but can also increase its number of ovipositions in the presence of IG-predator cues. We discuss these findings in the context of population dynamics and biological control.
Actividad del interferón proveniente de linfocitos esplénicos de pollo de engorda durante la infección experimental primaria con Eimeria tenella
Marco Antonio Juárez Estrada,Xóchitl Hernández Velasco,Guillermo Téllez Isaías
Veterinaria México , 1999,
Abstract: Con la finalidad de evaluar el interferón (IFN) secretado durante la infección experimental primaria con Eimeria tenella se realizaron dos estudios. En el primero se evaluó la respuesta primaria en linfocitos T (LT ) esplénicos de 40 pollos de engorda (Hubbard x Hubbard) de 20 días de edad, desafiados con 1 x 104 ooquistes esporulados de E. tenella. Los LT se aislaron a partir de cuatro bazos en dos mezclas celulares con la técnica de columnas de fibra de nailón a los días 1, 3, 5, 7 y 9 posinoculación (pi). En el segundo experimento de respuesta primaria, el aislamiento de los LT se efectuó con la técnica de Ficoll Hypaque con cultivos celulares esplénicos individuales provenientes de 30 aves. En cada uno de los dos experimentos se utilizó la mitad de aves del grupo desafiado como aves testigo sin desafiar. Para evidenciar el IFN presente cada día pi se empleó un ensayo antiviral con el virus de la enfermedad de Newcastle y la infección de la bolsa de Fabricio. En el primer experimento se observó que el IFN del grupo desafiado alcanzó un pico al día 5 pi que difirió (P<0.05) del grupo testigo, bajó ligeramente al día 7 pi (P<0.05) y se incrementó al día 9 pi (P<0.05). En el segundo experimento, se determinó un comportamiento similar al primero, pero con títulos más altos. El patrón de liberación de IFN de los LT estimulados in vitro después del desafío con E. tenella es diferente al patrón de liberación de los LT estimulados in vitro pero sin el desafío con E. tenella. Los ensayos antivirales utilizados detectaron cualitativa y cuantitativamente el IFN aviar secretado por LT estimulados in vitro. Los patrones de liberación de IFN detectado con las dos técnicas de aislamiento de LT después de la infección primaria con E. tenella se comportaron de manera semejante.
Enfermedad de Marek
Victor M. Petrone García,Xóchitl Hernández Velasco,Guillermo Téllez Isaías
Veterinaria México , 2000,
Abstract:
Hallazgo de Eimeria tenella en células epiteliales de la bolsa de Fabricio
Xóchitl Hernández Velasco,Marco A. Juárez Estrada,Norma Calderón Apodaca,Guillermo Téllez Isaías
Veterinaria México , 1999,
Abstract: En el presente trabajo se describen observaciones realizadas durante un experimento dise ado para estudiar el comportamiento de los leucocitos polimorfonucleares en infecciones con E. tenella en pollos tratados con 5-FU como agente granulocitopénico. Ciento veinte pollitos de engorda fueron asignados en 4 grupos con 30 pollitos cada uno: 1) testigo blanco, 2) tratado con 200 mg/kg de peso de 5-fluorouracilo (5-FU), 3) infectado oralmente con 5 000 ooquistes esporulados de Eimeria tenella y 4) infectado con E. tenella después del tratamiento con 5-FU. Se administró E. tenella a 5 pollos de cada grupo a los días: 2, 4, 6, 8, 10 y 12 días posinoculación con 5-FU (17 días de edad). Siete días posinfección con E. tenella se tomaron muestras de tejidos de varios órganos, para su estudio histológico. Se observaron coccidias en diferentes estados de desarrollo en 25 y 24 pollos en los grupos 3 y 4 respectivamente. Se observó hiperplasia epitelial moderada a severa, infiltrado mononuclear en el subepitelio, y algunos quistes intraepiteliales, que fueron asociados con la presencia del parásito. Este hallazgo muestra que bajo ciertas circunstancias E. tenella es capaz no sólo de invadir el epitelio de la bolsa de Fabricio, sino también de desarrollarse en él.
Nivel de proteína, fibra y cultivo de levadura Saccharomyces cerevisiae en dietas a base de trigo para cerdos
Reynoso-González, Ezequiel;Cervantes-Ramírez, Miguel;Figueroa-Velasco, J. Luis;Morales-Trejo, Adriana;Araiza-Pi?a, Alfonso;Yá?ez-Hernández, Jorge;
Agrociencia , 2010,
Abstract: the reduction in protein content and inclusion of wheat bran in the diet improves the amino-acids (aa) profile, but increases the fiber content. to this respect, yeasts can increase the digestion of fiber. three experiments were carried out to evaluate the effect of yeast culture (yc) on diets with a standard (scpd) or low level of crude protein (lcpd), with or without free aa, for growing-finishing pigs (landrace-hampshire-duroc). in the three experiments the design was randomized complete blocks and data were analyzed with glm procedure of sas. in experiment 1, 28 growing pigs (25.2±4.7 kg) were used and there was a factorial arrangement 2 (cp, 11.0 and 18.8 %) x 2 (yc, 0 and 0.75 %) of treatments. the yc did not change (p>0.33) the productive response; the cp level did not influence weight gain (adg) nor feed intake (fi; p>0.14), but the conversion (ca) was better (p=0.01) with scpd. experiment 2 was conducted with 40 finishing pigs (60.2±8.3 kg) and the treatments (t) were: tl) base diet, wheat-soybean-wheat-bran meal; t2) t1 + 0.75 % of yc; t3) tl + 1.5 % of yc; t4) control diet wheat-soybean meal; and t5) diet low in cp + free aa. the yc did not change the performance nor the characteristics of the carcass; when it was compared with the lcpd, the area of the longissimus dorsi muscle (p=0.08) and the back fat (p=0.02) were better in pigs fed diets with yc cl, but yield (p=0.02), adg (p=0.04) and fi (p=0.05) were higher in the lcpd. experiment 3 was conducted with 32 finishing pigs (67.1 ±10.3 kg); and there was a factorial arrangement 2 (pc, 13.0 and 16.0%) x 2 (yc, 0 and 0.75 %) of treatments. the yc (p>0.70) and the cp level (p≥0.43) did not affect the response of the pigs. it can be concluded that the inclusion of yc in wheat-based diets does not influence the productive response of growing to finishing pigs.
Detección y seguimiento con inspección visual del cérvix para la prevención del cáncer cervicouterino en las zonas rurales de México
Pérez-Cruz,Eduardo; Winkler,Jennifer L; Velasco-Mondragón,Eduardo; Salmerón-Castro,Jorge; García,Francisco; Davis-Tsu,Vivien; Escandón-Romero,Celia; Hernández-Avila,Mauricio;
Salud Pública de México , 2005, DOI: 10.1590/S0036-36342005000100007
Abstract: objective: to compare the standard cervical cancer screening procedure -the papanicolaou test or pap smear- with detection through visual inspection using acetic acid (via), and visual inspection with acetic acid assisted by aviscope (viam). material and methods: the study was conducted between october 1998 and december 2000, in two mixteca regions in oaxaca, mexico. a field trial design was used to randomize the two regions to either of the two inspection methods. in one region 2,240 women received via; in the other, 2,542 women received viam. women positive to visual inspection and a subsample of women with negative results were referred for colposcopy and, if necessary, cervical biopsy. statistical data analysis consisted of descriptive statistics and comparison of groups using chi-squared tests. diagnostic values were obtained for via and viam, using as gold standards colposcopy and biopsy. results:viam identified a higher proportion of women with a cervical abnormality (16.3%) than via (3.4%), as well as normal women (58.5% vs. 53.8%). via identified a higher proportion of women with benign changes (41.2%) than viam (19.6%). viam had a greater sensitivity (p>0.05) but lower specificity (p<0.05) than via, using as gold standards colposcopy and biopsy. conclusions: the two study groups were comparable for age, parity and cytological results; however, visual inspection results were different between the groups: viam identified more lesions confirmed by biopsy. the diagnostic utility of viam and via was lower than expected. training of clinical personnel in visual inspection is critical to improve the effectiveness of these screening methods.
Desarrollo y Situación Actual de la Bioética en México. Desarrollo y Situación Actual de la Bioética en México
Jorge Hernández Arriaga
Acta Universitaria , 2012,
Abstract: An overview on bioethics and the development of institutions devoted to the study of bioethics in Mexico, is presented, in particular the Centro de Investigaciones en Bioética de la Universidad de Guanajuato (CIBUG). Also, academic activities that support this topic are summarized, such as teaching of bioethics, biomedical research, National and International Congresses, Journals and Books that have contributed to the development of bioethics in Mexico. Se presenta una panorámica de la bioética y el desarrollo de las instituciones que la estudian en México, en particular el Centro de Investigaciones en Bioética de la Universidad de Guanajuato (CIBUG). Asimismo, se revisan las actividades académicas que se realizan como ense anza de la bioética, investigación biomédica y la realización de productos y eventos académicos, tales como Congresos, Revistas y Libros, que han contribuído al desarrollo de la bioética en México.
Trihalomethanes in Comerio Drinking Water and Their Reduction by Nanostructured Materials  [PDF]
Jorge Hernández Bourdon, Francisco Márquez Linares
Soft Nanoscience Letters (SNL) , 2014, DOI: 10.4236/snl.2014.42005
Abstract: The formation of disinfection by-products (DBPs) during chlorination of drinking water is an issue which has drawn significant scientific attention due to the possible adverse effects that these compounds have on human health and the formation of another DBPs. Factors that affect the formation of DBPs include: chlorine dose and residue, contact time, temperature, pH and natural organic matter (NOM). The most frequently detected DBPs in drinking water are trihalomethanes (THMs) and haloacetic acids (HAAs). The MCLs are standards established by the United States Environmental Protection Agency (USEPA) for drinking water quality established in Stage 1, Disinfectants and Disinfection Byproducts Rule (DBPR), and they limit the amount of potentially hazardous substances that are allowed in drinking water. The water quality data for THMs were evaluated in the Puerto Rico Aqueduct and Sewer Authority (PRASA). During this evaluation, the THMs exceeded the maximum contamination limit (MCLs) for the Comerio Water Treatment Plant (CWTP). USEPA classified the THMs as Group B2 carcinogens (shown to cause cancer in laboratory animals). This research evaluated the THMs concentrations in the following sampling sites: CWTP, Río Hondo and Pinas Abajo schools, Comerio Health Center (CDT), and the Vázquez Ortiz family, in the municipality of Comerio Puerto Rcio. The results show that the factors affecting the formation of THMs occur in different concentrations across the distribution line. There are not specific ranges to determine the formation of THMs in drinking water when the chemical and physical parameters were evaluated. Three different nanostructured materials (graphene, mordenite (MOR) and multiwalled carbon nanotubes (MWCNTs)) were used in this research, to reduce the THMs formation by adsorption in specific contact times. The results showed that graphene is the best nanomaterial to reduce THMs in drinking water. Graphene can reduce 80 parts per billion (ppb) of THMs in about 2 hours. In addition mordenite can reduce approximately 80 ppb of THMs and MWCNTs adsorbs 71 ppb of THMs in the same period of time respectively. In order to complement the adsorption results previously obtained, total organic carbon (TOC) analyses were measured, after different contact times with the nanomaterials. During the first 30 minutes, graphene C/Co was reduced to c.a. 0.9, in presence of each THMs solution. MWCNTs and MOR show similar adsorptions trends in comparison with graphene.
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