The objective of this study was to describe the trend of reproductive performance of primiparous and multiparous cows that grazed rice crop residues located in a Dry Tropical Forest of Colombia, taking into account th...The objective of this study was to describe the trend of reproductive performance of primiparous and multiparous cows that grazed rice crop residues located in a Dry Tropical Forest of Colombia, taking into account the rainfall pattern of the place. In this study, 89 primiparous and 309 multiparous Cebu cattle records were analyzed. Mean, mean standard deviation for age at first calving and open days of primipar-ous Cebu cattle were 41.05± 1.85 months and 269.7±36.25 days respectively. Confidence intervals (95%) for both reproductive parameters were 36.8-45.3 months and 202.7-336.6 days respectively. For multiparous Cebu cattle, the mean and mean standard deviation for open days and calving interval were 245.6±36.8 days and 17.5±0.9 months respectively. Confidence intervals 207.1-366.9 days and 13.9-20.7 months respectively. The mean rainfall since 1999 until 2012 was1202 mmper year. The reproduc-tive trend of the primiparous cattle showed an increasing behavior of age at first calving since 1999 until 2012, that can possibly be explained due to the decreasing behavior of the rainfall throughout the years, that can affect the nutritional value and offer of the grass that can grow in the borders of the crop, such as Guinea and Star grass, and eventually affect the body condition and weight necessary to be ready for the first estrous. An inverse behavior of open days occurred, showing a decreased trend along the last years of research. This fact could have happened due to the intensive use of the enriched rice straw with urea and molasses lately. Regarding to the reproductive trend of the multiparous cattle, there is no an evident pat-tern of it. Factors such as rainfall, temperature, nutrition and management should have affected it. Further research on this topic is needed.展开更多
CeB6 powders were prepared by high-temperature self-propagating synthesis （SHS） in which CeO2, B203 and Mg were taken as reactants. The adiabatic temperature and dynamics of SHS reactions were investigated. The SHS ...CeB6 powders were prepared by high-temperature self-propagating synthesis （SHS） in which CeO2, B203 and Mg were taken as reactants. The adiabatic temperature and dynamics of SHS reactions were investigated. The SHS reaction products and leached products were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indicated that the adiabatic temperature of Mg-B2Oa-CeO2 reaction system was rather higher than 1800 K to make the reaction propagate by itself, and the apparent activation energy （Ea） and reaction order （n） of exothermic peak on Mg-BzO3-CeO2 differential scanning calorimetry （DSC） curve were 23.03 kJ/mol and 1.31, respectively. The apparent activation energy was lower, so the reaction occurred easily. The SHS products consisted of MgO, CeB6 and little MgaB2O6. The leached products consisted of single CeB6 phase and its purity was higher than 99.0%, and the average particle sizes of CeB6 were smaller than 150 nm.展开更多
We presented a field electron emission measurement of single crystalline CeB6 nanowires.The nanowires exhibited a low turn-on electric field(7.6 V/μm at 10 μA/cm2),and the deviation of Fowler-Nordheim(F-N) plots fro...We presented a field electron emission measurement of single crystalline CeB6 nanowires.The nanowires exhibited a low turn-on electric field(7.6 V/μm at 10 μA/cm2),and the deviation of Fowler-Nordheim(F-N) plots from straight line was observed in field electron emission measurements.The field enhancement factors were obtained by separate straight line fitting.The nonlinearity in the F-N plots may be attributed to the non-uniform field electron emission of CeB6 nanowires.The field emission properties of the ...展开更多
文摘The objective of this study was to describe the trend of reproductive performance of primiparous and multiparous cows that grazed rice crop residues located in a Dry Tropical Forest of Colombia, taking into account the rainfall pattern of the place. In this study, 89 primiparous and 309 multiparous Cebu cattle records were analyzed. Mean, mean standard deviation for age at first calving and open days of primipar-ous Cebu cattle were 41.05± 1.85 months and 269.7±36.25 days respectively. Confidence intervals (95%) for both reproductive parameters were 36.8-45.3 months and 202.7-336.6 days respectively. For multiparous Cebu cattle, the mean and mean standard deviation for open days and calving interval were 245.6±36.8 days and 17.5±0.9 months respectively. Confidence intervals 207.1-366.9 days and 13.9-20.7 months respectively. The mean rainfall since 1999 until 2012 was1202 mmper year. The reproduc-tive trend of the primiparous cattle showed an increasing behavior of age at first calving since 1999 until 2012, that can possibly be explained due to the decreasing behavior of the rainfall throughout the years, that can affect the nutritional value and offer of the grass that can grow in the borders of the crop, such as Guinea and Star grass, and eventually affect the body condition and weight necessary to be ready for the first estrous. An inverse behavior of open days occurred, showing a decreased trend along the last years of research. This fact could have happened due to the intensive use of the enriched rice straw with urea and molasses lately. Regarding to the reproductive trend of the multiparous cattle, there is no an evident pat-tern of it. Factors such as rainfall, temperature, nutrition and management should have affected it. Further research on this topic is needed.
基金supported by National Natural Science Foundation of China(51002025,50644016,50874027)
文摘CeB6 powders were prepared by high-temperature self-propagating synthesis （SHS） in which CeO2, B203 and Mg were taken as reactants. The adiabatic temperature and dynamics of SHS reactions were investigated. The SHS reaction products and leached products were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indicated that the adiabatic temperature of Mg-B2Oa-CeO2 reaction system was rather higher than 1800 K to make the reaction propagate by itself, and the apparent activation energy （Ea） and reaction order （n） of exothermic peak on Mg-BzO3-CeO2 differential scanning calorimetry （DSC） curve were 23.03 kJ/mol and 1.31, respectively. The apparent activation energy was lower, so the reaction occurred easily. The SHS products consisted of MgO, CeB6 and little MgaB2O6. The leached products consisted of single CeB6 phase and its purity was higher than 99.0%, and the average particle sizes of CeB6 were smaller than 150 nm.
基金supported by the NSFC Grant (50972046) supported through NSFC Committee of ChinaScience and Technology Foundation supported through the Science and Technology Bureau of Guangdong Government
文摘We presented a field electron emission measurement of single crystalline CeB6 nanowires.The nanowires exhibited a low turn-on electric field(7.6 V/μm at 10 μA/cm2),and the deviation of Fowler-Nordheim(F-N) plots from straight line was observed in field electron emission measurements.The field enhancement factors were obtained by separate straight line fitting.The nonlinearity in the F-N plots may be attributed to the non-uniform field electron emission of CeB6 nanowires.The field emission properties of the ...
