977 resultados para temperature-dependent sex determination


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Matematica Aplicada e Computacional - FCT

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Models of daily energy requirement can help to establish better and more profitable feeding programs for poultry. Studies have been conducted at UNESP-Jaboticabal-Brazil with the aim of studying energy utilization in broiler breeders, laying hens, and broilers, and to establish metabolisable energy requirement models. The factorial approach was used to partition the energy requirements into maintenance, growth, and production components. The resulting models consider body weight, weight gain, egg production, and environmental temperature for the determination of the energy requirements of poultry. These models were evaluated in performance trials and provided good estimates. Therefore, they can be used to establish nutritional programs. The aim of this chapter is to describe the development of these models and to outline the results of our studies at UNESP.

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To assess the possibility of shifting the sex ratio at birth, since this can contribute to enhancing the genetic gain and producity in cattle, this work is aimed at raising the factors that may influence sex determination of creates. This study is based on research conducted in the area of reproduction and production of beef and dairy cattle, some quotes in humans, mouse, dogs and a study in pigs. This was due to back of data and studies in the bovine species. It was noted that stress during pregnancy, intake of vitamin C or others substances and the time of artificial insemination are the factors that may influence the determination of the type of product. Human studies, concluded that woman more stressed are more likely to produce female children of the quietest. Furthermore, sows that received ascorbic a ad orally for seven days and were inseminated during this period, produce more female then those who did not receive the vitamin. These studies may suggest that cows can also suffer influence of stress and food for the determination of sex of calf. There are also studies suggesting that cows inseminated at the earliest time of ovulation ted to produce more male calves than those inseminated a few hours before that time. Some scholars considers the hypothesis... (Complete abstract click electronic access below)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The probiotic potential of Leuconostoc mesenteroides subsp. mesenteroides SJRP55 isolated from water buffalo mozzarella cheese was evaluated. The microorganism presented resistance to stressful conditions that simulated the gastrointestinal tract, and to the best of our knowledge Leuconostoc mesenteroides SJRP55 was the first of this species with the ability to deconjugate bile salts. Tolerance to NaCl was temperature dependent, as well the results obtained by aggregation capacity. The strain presented good adhesion properties, β galactosidase activity, viability in fermented milk during storage, non-active against Streptococcus thermophilus and sensible to most of the tested antibiotics. Some analgesic medications inhibited the growth of the strain. Leuconostoc mesenteroides SJRP55 exhibited in vitro probiotic potential, and it can be better characterized through future in vivo tests. This bacterium presents higher functional properties compared to other studied strains, and therefore it is a potential candidate for the application as a probiotic strain, which could be used by industries in the manufacture of functional milk-based products.

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A renormalization-group calculation of the temperature-dependent nuclear spin relaxation rate for a magnetic impurity in a metallic host is reported. The calculation follows a simplified procedure, which produces accurate rates in the low-temperature Fermi-liquid regime, although yielding only qualitatively reliable results at higher temperatures. In all cases considered, as the temperature T diminishes, the rates peak before decaying linearly to zero in the Fermi-liquid range. For T → 0, the results agree very well with Shiba's expression relating the low-temperature coefficient of the relaxation rate to the squared zero-temperature susceptibility. In the Kondo limit, the enhanced susceptibility associated with the Kondo resonance produces a very sharp peak in the relaxation rate near the Kondo temperature. © 1991.

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IR-visible upconversion fluorescence spectroscopy and thermal effects in pr(3+)/Yb3+-codoped Ga2O3:La2S3 chalcogenide glasses excited at 1.064 mum is reported. Intense visible upconversion emission in the wavelength region of 480-680 nm peaked around 500, 550, 620 and 660 nm is observed. Upconversion excitation of the Pr3+ excited-state visible emitting levels is achieved by st combination of phonon-assisted absorption, energy-transfer and phonon-assisted excited-state absorption processes. A threefold upconversion emission enhancement induced by thermal effects when the codoped sample was heated in the temperature range of 20-200 degreesC is demonstrated. The thermal-induced enhancement is attributed to a multiphonon-assisted anti-Stokes process which takes place in the excitation of the ytterbium and excited-state absorption of the praseodymium. The thermal effect is modelled by conventional rate equations considering temperature-dependent effective absorption cross-sections for the F-2(7/2)-F-2(5/2) ytterbium transition and (1)G(4)-P-3(0) praseadymium excited-state absorption, and it is shown to agree very well with experimental results. Frequency upconversion in singly Pr3+-doped samples pumped at 836 nm and 1.064 mum in a two-beam configuration is also examined.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The growth parameters and the mortality rates of the Scomber japonicus peruanus (Chub mackerel) were studied based on monthly data of frequency of fork length classes obtained from commercial landings off the Peruvian coast from 1996 to 1998. The asymptotic body length and growth rate values obtained by the ELEFAN I (Electronic Length Frequency Analysis) ranged from 40.20 cm to 42.20 cm and from 0.38 to 0.39, respectively. The oscillation amplitude was 0.60; the Winter point values varied from 0.50 to 0.60 and the performance index from 2.79 to 2.84. The total mortality rate of the Chub mackerel obtained by the linearized catch curve oscillated between 1.68 and 3.35. The rate of fishing mortality varied from 1.16 to 2.78 and the exploitation rate from 0.68 to 0.84. The annual rate of natural mortality estimated by the Pauly`s method ranged from 0.52 to 0.53. The results obtained allow us to conclude that the longevity of the Chub mackerel was slightly over seven years.

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Males, queens and workers of stingless bees show differences in external morphology, behaviour and roles within a colony. In addition, each individual has a cuticular chemical signature responsible for mutual communication that is essential for maintaining the integrity of the colony. In this paper we characterize the cuticular hydrocarbon composition of newly emerged diploid and haploid males, workers and virgin queens of Melipona quadrifasciata by gas chromatography-mass spectrometry (GC/MS) analysis. This is the first time that the cuticular profile of diploid males in a species of stingless bee has been characterized. We found differences in the cuticular hydrocarbon composition among males, workers and virgin queens, recording both qualitative and quantitative differences among individuals of different phenotypes. However, no compound was found exclusively in diploid males. The cuticular chemical profiles of haploid and diploid males were very similar to those of workers. Moreover, the cuticular lipids of males and workers were significantly different from those of queens. Tricosane, pentacosene-2 and 7-methyl-heptacosane were the compounds responsible for this significant separation. This result correlates with the behavioural and morphological differences among these phenotypes.