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Induced fractional valley number in graphene with topological defects
Angel E. Obispo,Marcelo Hott
Physics , 2014, DOI: 10.1103/PhysRevB.91.035404
Abstract: We report on the possibility of valley number fractionalization in graphene with a topological defect that is accounted for in Dirac equation by a pseudomagnetic field. The valley number fractionalization is attributable to an imbalance on the number of one particle states in one of the two Dirac points with respect to the other and it is related to the flux of the pseudomagnetic field. We also discuss the analog effect the topological defect might lead in the induced spin polarization of the charge carriers in graphene.
Composición química y degradabilidad ruminal de los frutos de algunas especies forrajeras le?osas de un bosque seco tropical
Cecconello C,Gerardo; Benezra S,Miguel; Obispo,Nestor E;
Zootecnia Tropical , 2003,
Abstract: in a tropical dry forest, in the south area of the aragua state in venezuela and during the dry season, the native woody leguminous fruits, chloroleucon manguense, pithecellobium saman, enterolobium cyclocarpum, acacia macracantha, senna atomaria, caesalpinia granadillo and caesalpinia coriaria, commodnly consumed by the ruminants were evaluated. to know their chemical and structural composition, and mineral contents, these fruits were divided up in entire fruit, seed and fruit without seed. furthermore, ruminal degradability of the dry matter of different fractions was evaluated by means of the nylon bag technique. there was observed a great variation among species for pc and eln contents in the entire fruits. c. manguense showed the higher pc (21%) value, while c. coriaria and c. granadillo the lowest (4%). pc contents of the seeds were located in a range between 16 and 29%, with the higher value for c. manguense. similarly, values for fdn and fda ranged from18 to 62%, and 13 to 41%, respectively. in both cases, the lowest values of these fractions were observed for c. coriaria fruit and the highest to s. atomaria. in all cases, the entire fruits showed higher degradabilidad than the fruits without seed, with the higher values for p. saman (62%) and e. cyclocarpum (81%) fruits. ca. p mg, cu, and s contents on these fruits seem to be important to complement ruminant diets.
El dise?o cruzado: un dise?o para la experimentación con vacas lecheras
Obispo,Nestor E; Espinoza,Yusmary; Gil,José Luis;
Zootecnia Tropical , 2004,
Abstract: an arrangement in sequences of latin squares was demonstrated to be statistically efficient to detect the presence of residual effects in the experimentation with milk cows. with this purpose, the milk production of five cows was simulated in the application of three treatments during three periods of 15 days each. a program was generated to estimate the residual effects, and other three to be executed by the proc glm of sas: one for a complete model where all the present sources of variation were included, other to detect at least a period with residual effect, and finally a model similar to a classic latin square without taking into account the residual effects. the sequence of latin squares allowed to detect the residual effects of treatments and the calculation of the least squares means corrected by this effect.
Selección de especies le?osas por vacunos en silvopastoreo de un bosque semicaducifolio en Venezuela
Ojeda,A.; Obispo,N.; Canelones,C.E.; Mu?oz,D.;
Archivos de Zootecnia , 2012, DOI: 10.4321/S0004-05922012000300004
Abstract: the woody plant palatability for cattle in a silvopastoral system on a semi-deciduous tropical forest (sdtf) was evaluated. epidermal fragments in fecal samples from 14 male cattle brahman x holstein (390.4 ± 18.0 kg live weight) grazing during 91 days in 81 ha located in portuguesa state, venezuela were evaluated. sdtf was present in 50 ha; the rest of grassland, was mainly composed by cynodon nlemfuensis, sporobolus indicus, cyperus sp. and axonopus sp. using the point quarter method on transects, 22 woody plant species were identified they were grouped into 11 botanical families, with 40.9% of species belonging to the fabaceae family. guazuma ulmifolia had the greater relative dominancy (60.4%), and together with pithecellobium lanceolatum and samanea saman reached the 81.1%. these same species showed the higher importance value index (162.6, 24.8 and 26.5 respectively). poaceae had the higher relative frequency (49.6%) for epidermal fragments in feces; total woody plants reached 46.2% (fabaceae: 80.7%). the most selected species were inga laurina, machaerium humboldtianum, s. saman and sida acuta, (ivlev index= 0.60 ± 0.09). the chemical composition of woody plants foliage suggest a selectivity profile adjusted to the nutrient profile offered by each species. these findings highlight the strategic value of sdtf in silvopastoral systems in tropical environments.
Efecto de la sustitución parcial de la proteína de la dieta por urea sobre el consumo voluntario de materia seca y respuesta productiva de corderos
Zapata,Carlos; Obispo,Nestor E.; Díaz,Yris; Palma,José; Gil,José L;
Zootecnia Tropical , 2004,
Abstract: to evaluate the effect of the partial substitution of the feed protein by urea (u) on dry matter intake (dmi) and on daily weight gain (dwg) in lambs, two experiments were undertaken in the ovine unit in the ceniap-inia, venezuela. in the first, twenty west african lambs (av. wt. 21±1.5 kg) were assigned to five diets, where urea replaced part of the protein from fishmeal (fm). in the second, twenty west african lambs (av. wt. 14±0.48 kg) were assigned to five diets where urea replaced the protein from soybean meal (sbm). in both experiments, urea was included at the levels of 0, 1, 1.5, 2 and 3% of the supplement. the daily ration of lambs was 300 g of supplement plus chopped hay of bermuda grass (cynodon dactylon) offered ad libitum. in the first experiment with fm, the daily intake of ms was the same among treatments, averaging 904.2±43 g/d. dwg was found to be different among treatments (p<0,05), with the higher value for 1,5, 2 and 3% u (60.0, 67,5 and 3% u (61.0). the 1% u (32.5) was similar to the control (40.0). similarly, feed conversion was improved (p<0.05) for the treatments with 1.5, 2 and 3% u, with values of 16, 15.5 and 14.8, respectively, which were lower than control (21.0) and 1% u (27.5) treatments. in the second experiment with sbm, there were observed differences (p<0.05) in dmi between control (0% u) and 1% u treatments (763.07 vs. 631.82 g/d). higher levels of u showed intermediate values (654.77, 688.41 and 717.72 g/d, for 1.5, 2 and 3% u levels, respectively). dwg was significantly different among treatments, with the highest gain for the treatment with 1% u (98.75 g/d). this value for 1.5% u (75.42 g/d) was similar to control (75.00 g/d). higher levels of substitution showed intermediate gains (87.92 and 88.75 g/d for the 2 and 3% u treatments, respectively). in this experiment, feed conversions were similar among treatments, with an overall value of 8.27. independently of the protein source, in this experience, urea replaced the protein o
Efecto del sombreado sobre la producción y calidad del pasto guinea (Panicum maximun) en un sistema silvopastoril
Obispo,Néstor E; Espinoza,Yusmary; Gil,Jose L; Ovalles,Francisco; Rodríguez,Maria F;
Zootecnia Tropical , 2008,
Abstract: in a cattle farm in the yaracuy state, venezuela, a research was carried out to evaluate the effect of shade density on biomass yield and on the quality of the guinea grass (panicum maximun). with the aid of satellite images and the analysis of cartographic charts, in four grassland areas, it was determined the canopy surface of the trees and their respective densities of shade. in these densities of shade (high, >30%; medium, between 20-30%; low <10% and without shade), considered as treatment, 15 points of sampling were set to harvest the contained guinean grass in a 0.25 m2 square frame, to determine the amount biomass kg/ha, the crude protein (pc), detergent fibers, neutral (ndf) and acid (adf), contents, and the in vitro digestibility. the greater yields (p<0.05) were observed for the low (14,045.9) and without shade (14,318.8) densities, with intermediate values in the medium shaded area (10,065.3), and the lowest for the high shaded (8,859.6). the pc contents were similar in all the densities, with an average value of 13.2 ± 0.36%, with a numerical tendency to be higher with the increases in the shaded. ndf content diminished (p<0.05) with the increases in the density of shaded, with values of 71.7, 69.9, 73.2 and 76.3%, for the high, medium, low and without shade treatments, respectively. adf contents were uniform in the shaded areas with an average value of 33.7%, but smaller for the forages in quite sunny area (42.6%). the digestibility of the forage was higher (p<0.05) for the forages in the high and medium shaded areas with values of 62.6 and 65.9, respectively, and lower in the low and without shade areas (59.4 and 59.4, respectively).
Efecto de la alimentación animal sobre la calidad microbiológicade estiércoles usados como fertilizantes
Espinoza,Yusmary; Hernández Z,Marcos J; Barrera Ch,Teresa V; Obispo,Néstor E;
Zootecnia Tropical , 2009,
Abstract: to evaluate the relationship between type of diet and microbiology quality of cow, hen, and pig manure used as fertilizers, we collected samples of each manure (m) from farms located in aragua, carabobo, and yaracuy states, venezuela. on the basis of a completely randomized experimental design with four repetitions, the following treatments were compared: bovine (b), poultry (g), and pork (c) manures, in combination with two different types of diets (d1 and d2) provided to the animals, for six treatments. samples were processed and analyzed for total bacteria and fungi contents, and total and fecal coliform bacteria. there was not a specific effect of the type of diet on the number of bacteria and fungi among the manures. the higher content of bacteria and fungi was observed in bovine and poultry manures, respectively. in general, the amount of fecal coliforms found in the manures ranked between 2 x 106 to 7 x 107 mpn/g. these values exceed those values internationally allowed for these pathogens in the manures used as fertilizers. manures were grouped on the basis of their similarities of microbial loads, pathogens or fertilizer conditions, in three well defined groups: i: bd1 and bd2, ii: gd1, gd2 and cd1, and iii: cd2. group i, with less stable conditions, was associated to the mineralization and higher number of bacteria. the second was more stable as organic fertilizer with lesser capacity to immobilize the n, but with a high risk for the public health due to its high load of pathogens. the third group had the highest risk for public health that compromises its use as organic fertilizer.
Efectos de la ractopamina y el nivel de lisina sobre la respuesta productiva de cerdos magros en la fase de engorde
Pérez,Aníbal; Obispo,Néstor E; Palma,José; Chicco,Claudio F;
Zootecnia Tropical , 2005,
Abstract: genetically improved leaning pigs (gilts and barrows) in the finishing phase were used to investigate the effect of two levels of ractopamine (rac: 0 and 100 ppm) and three levels of lysine (lys: 0.95, 1.05, and 1.15%) on the average daily gain (adg), hot (hw) and cold (cw: 24 and 48 h) weights, dressing percentage (dp), and drip losses at 24 (dl24) and 48 hours (dl48). there was an interaction between sex and rac which allowed gilts adg were similar than those observed for barrows. adg was higher (p<0.001) for those pigs on lys 1.15%, with increases of 8.2 and 11.03% for the treatments lys 0.95 and 1.05%, respectively. hw was higher (p<0.01) for lys 095% than lys 1.05 and 1.15% by 4.9 and 3.5 kg, respectively. dp, cw 24 and 48h were not affected by the level of this amino acid in the diet. lys at 1.05% showed higher (p<0.001) drip losses at 24 and 48h, with values of 2.61 and 1.80 kg, respectively. the lower drip losses were observed for lys 1.15% (1.92 and 1.23 kg, for 24 and 48 h, respectively). rac10 was 5.85 kg higher (p<0.001) in hw than control. similarly, adding rac showed higher (0.9 percentage units) than rac0 (p<0.05). cw at 24 and 48 h were much higher rac10 with increases of 5.863 and 5.13 kg, respectively, as compared to rac0. dl 24 were similar between treatments, however dl48 was higher (p<0.001) by 0.709 kg for rac10 as compared to rac0.
Sustitución total del maíz por el germen desgrasado y afrecho de maíz en la dieta de vacas lecheras
Cárdenas,María? A; Godoy,Susmira?; Obispo,Néstor? E; Chico,Claudio F;
Zootecnia Tropical , 2002,
Abstract: the agro industrial byproducts thick (tg) and fine (tf) cakes, that contain the bran and free-fat corn gluten meal, originate from processing whole corm to elaborate the precooked flour, are two physically and chemically different feedstuffs which were nutritionally evaluated by feeding medium production dairy cows. twelve cows (3/4 holstein x 1/4zebu) in middle stage of lactation were assigned to three suplementación treatments, where corn (m) was substituted for the corn byproducts tg and tf cakes. in a crossover experimental design, it was measured the daily production and quality of milk. from the results, it comes off that substituting corn for these energy sources did not affect the evaluated variables. the averages values (kg) for daily production of milk were: 10.95, 10.68, and 10.23 kg for the treatments m, tg, and tf, respectively. the contents (% dm) of total solids, protein, and fat were: 29.16, 11.60, and 25.15 for m, 29.19, 11.56, and 23.44 for tg, and 29.29, 11.60, and 21.74 for tf, respectively. based on this research, it was concluded that these byproducts could substitute completely corn in the concentrated foods for cows of medium production without affecting milk quality.
Composición fitoquímica y nutricional de harina de pijiguao (Bactris gassipaes Kunth en H.B.K)
Pizzani,Pablo; Blanco,María; Malaver,Thamaris; Godoy,Susmira; Matute,Irana; Palma,José; Obispo,Nestor E;
Zootecnia Tropical , 2008,
Abstract: to evaluate the phytochemical and nutritional composition of the whole meal of pijuguao (bactris gassipaes) fruits (wmp), it was determined by phytochemistry screening the presence of fourteen secondary total metabolites: total phenols, flavonoids, tannins to precipitate the proteins, condensed tannins, steroids, quinons, cumarins, non-proteins amino acids, alkaloids, saponins, triterpens and proanthocyanidins, catechins, reducing sugars and mucilage, ndf, adf, pc, macro and micro minerals, and ash. the phytochemical study indicated the presence of non-protein amino acids, triterpens, reducing sugars and catechins; the rest of secondary metabolites did not showed positive reaction. the various components of the mineral and chemical analysis gave a crude protein of: 6.58%, 12.58% fat, ash: 1.98%, ca 0.08%, p 0.11%, mg 0.05%, k 0.39%, and 20, 22, 4 y 3 ppm para fe, zn, cu y mn, respectively. the estimated metabolizable energy content of the wmp was 12.41 mj / kg. the fiber content, expressed as ndf and adf were 21.16 and 10.44 %, respectively. the values of degradability in vitro dry matter was 80%.accordingly, we conclude that the wmp represents an alternative energy source to feed ruminants because with low secondary metabolites contents and high in vitro degradability values.
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