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61.
Accuracy of culture for diagnosis of Tritrichomonas foetus was investigated in 2832 naturally exposed range beef bulls from 124 herds. Preputial fluid samples were inoculated into the culture medium, incubated at 37 degrees C, and daily examined. Diagnostic test was evaluated using Bayesian techniques to estimate sensitivity and specificity without a gold standard. Median posterior test sensitivity was 72.04% (95% probability interval: 58.07-86.38%) and specificity was 95.37% (95% probability interval: 94.07-96.65%). Low diagnostic test accuracy may have resulted from host and/or diagnostic test procedure related factors. Under natural range conditions, more accurate methods for T. foetus diagnostic and repeated preputial samplings of bulls may be necessary on trichomonosis control programs. 相似文献
62.
Braunschweig H Dewhurst RD Hammond K Mies J Radacki K Vargas A 《Science (New York, N.Y.)》2012,336(6087):1420-1422
Homoatomic triple bonds between main-group elements have been restricted to alkynes, dinitrogen, and a handful of reactive compounds featuring trans-bent heavier elements of groups 13 and 14. Previous attempts to prepare a compound with a boron-boron triple bond that is stable at ambient temperature have been unsuccessful, despite numerous computational studies predicting their viability. We found that reduction of a bis(N-heterocyclic carbene)-stabilized tetrabromodiborane with either two or four equivalents of sodium naphthalenide, a one-electron reducing agent, yields isolable diborene and diboryne compounds. Crystallographic and spectroscopic characterization confirm that the latter is a halide-free linear system containing a boron-boron triple bond. 相似文献
63.
Consuelo Riva Andrea Binelli Marco Parolini Alfredo Provini 《Water, air, and soil pollution》2010,210(1-4):75-86
In 1996, dichlorodiphenyltrichloroethane (DDT) pollution of industrial origin was discovered in Lake Maggiore. It was caused by industrial effluents on a tributary of the River Toce, one of the major affluents of the lake in correspondence of Pallanza Bay. This event is the worst case of environmental pollution that has occurred in Western countries in the last 25 years, not due to agricultural use of DDT, but because of an accidental industrial discharge. Heavy polychlorinated biphenyls (PCBs) pollution was also noticed in 2002, with concentration levels three to seven times higher than those measured in other Italian subalpine lakes. In this study, the current DDT and PCBs contamination levels were assessed according to their presence in zebra mussel (Dreissena polymorpha) specimens sampled in the last 5 years (2003–2008) in eight sampling stations of Lake Maggiore, chosen to cover the entire perimeter of the basin. Moreover, for two stations (Baveno and Pallanza-Villa Taranto) located inside and outside Pallanza Bay, respectively, it is possible to make comparisons starting from 1996. The results obtained show how Lake Maggiore is still an ecosystem with a severe environmental risk, more than 10 years after the original insecticide discharge. DDT contamination continues to evolve, and natural events, like lake overturn, floods, and heavy rains, can have a great influence on the insecticide levels in the lake. By contrast, PCB contamination is absolutely negligible, even if the peak of pollution revealed in 2002 seems to indicate that these pollutants are still present in large quantities in the Lake Maggiore watershed. 相似文献
64.
To determine the optimum selection environment for barley (Hordeum vulgare L.) targeted at low-input, stress environment,
barley lines were selected for high yield under stress (YS), high yield under non-stress (YNS), or average yield in stress
and non-stress conditions (YA) during three breeding cycles (cohorts) of three years each. The lines were then tested in a
total of 21 year-location combinations with average grain yields ranging from 0.35 to 4.86 t ha-1. Yield under stress of the YS lines was between 27% and 54% higher than that of the YNS lines, with the top YS lines yielding
under stress between 16% and 30% more than the top YNS lines. Realized heritability was between 0.35 and 0.67 when selection
was conducted under stress and was significant in all three cohorts. By contrast, selection under non-stress gave a significant
response in only one cohort, and its efficiency in improving yield under stress was significantly lower than selection under
stress. The best YNS line ranked only 19th for yield under stress. The highest-yielding lines under stress were not only selected
under stress, but were also landraces collected in very dry areas (< 250 mm total annual rainfall). This confirms earlier
findings and supports the idea that the most effective way to improve productivity of crops grown in less-favored areas is
to use locally adapted germplasm and select in the target environment(s).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
65.
Alfredo Gallardo‐Collí Manuel Prez‐Fuentes Carlos Ivn Prez‐Rostro Martha Patricia Hernndez‐Vergara 《Aquaculture Research》2020,51(5):1813-1823
The compensatory growth, productive performance, proximal composition and somatic indices of Nile tilapia (Oreochromis niloticus) cultivated in biofloc were evaluated during a 144‐day period under five cyclic regimes of feed restriction and feeding. Five treatment groups, in which the frequency of feed restriction (R) and feeding (F) varied by periods (days) as follows: R1:F3, R3:F9, R6:F18, R8:F24 and R12:F36; each treatment was evaluated in triplicate. The cycles were repeated throughout the culture period. The control group received feed daily. Fish were cultivated in 18 circular tanks (3 m3) at a density of 50 fish/m3 per tank. At the end of the study, the survival of Nile tilapia was greater than 90% in all the treatments. Complete compensation in growth was achieved in R6:F18 and R12:F36. At the end of the feed restriction period, both crude protein and total lipid content of the tilapia muscle tissue taken from fish of the treatment groups were similar to samples of muscle tissue derived from fish of the control group; however, a reduction of more than 40% in somatic indices compared with the control was observed, but these recovered by the end of the feeding phase. The results indicate that cyclic feeding based on 12 days of feed restriction and 36 days of feeding (R12:F36) induced a complete compensation in weight and restoration of energy reserves, with similar measures of productive performance observed when compared to the control treatment during the culture of Nile tilapia in biofloc, and food reduction did not affect proximal composition. 相似文献
66.
Nallely Estrada‐Perez Javier M. J. Ruiz‐Velazco Francisco J. Magallon‐Barajas Angel I. Campa‐Cordova Alfredo Hernndez‐Llamas 《Aquaculture Research》2020,51(1):242-254
The production of Litopenaeus vannamei was analysed when affected by the acute hepatopancreatic necrosis disease using a dynamic stock model and primary data of seven production cycles from a shrimp farm in Mexico from 2013 to 2016. Significant results (p < .05) of the correlation analysis indicated that during those years mortalities by the disease were more severe when water salinity was high and productivity was low. Significant results from ANOVA showed that throughout the period, disease severity and salinity diminished while pond productivity initially declined but subsequently improved. Significant results from regression analyses conducted for each production cycle also indicated the importance of salinity and productivity on disease severity and showed that early mortality by the disease occurred in ponds with warmer water. Within the observed range of water quality parameters, increases of 1 cm in water transparency and 1 g/L in salinity resulted in increments within 0.17%–0.25% and 1.7%–3.1% in shrimp mortality by the disease. When increases of 1°C in water temperature were recorded, outbreaks occurred 0.2–1.57 weeks earlier. In conclusion, the disease strongly determines the dynamics of shrimp production, and the role of salinity, productivity and temperature is worthy of further delving. 相似文献
67.
68.
López A Montaño A García P Garrido A 《Journal of agricultural and food chemistry》2006,54(18):6747-6753
The fatty acid composition of 67 commercial presentations of table olives was determined. The most abundant fatty acids, in decreasing order of presence, were C18:1, C16:0, C18:2 n-6, and C18:0. The ranges, expressed as grams of fatty acids per 100 g of edible portion, for the different nutritional fractions were as follows: saturated fatty acids, 2.07-5.99; monounsaturated fatty acids, 5.67-19.42; polyunsaturated fatty acids, 0.52-3.87; and trans-fatty acids, 0.08-0.44. Principal component analysis of the matrix of the fatty acid composition led to the deduction of new factors. The first accounted for 55.10% of the total variance and was mainly related to C16:10, C18:0, C20:0, C22:0, C24:0, C18:1, C18:1t, and C20:1. The second factor accounted for 10.33% of variance and was related to C16:1 and C18:2 n-6. They did not permit differentiation among elaboration types or cultivars. However, discriminant analysis was successfully applied for this objective. The fatty acids that most contributed to discriminate among elaboration styles were C17:1, C18:1, C16:0, C17:0, and C18:0 (function 1) and C17:0, C17:1, C20:0, C16:0, C18:1, and C24:0 (function 2). In the case of cultivars, they were C20:0, C18:1, C17:1, C18:2 n-6, C18:1t, and C18:2t (function 1); C18:2 n-6, C18:1, C16:0, C20:0, C18:0, and C18:2t (function 2); and C17:0, C18:3 n-3, and C17:1 (function 3). Results from this study have shown differences among the fatty acid composition and fat content of the diverse commercial presentations of table olives, which can be applied in predictive and classification discriminant analysis. 相似文献
69.
Jose Alfredo Gutierrez-Reyes ;Estela Flores-Velazquez ;Guillermo Agustin Reyes-Escalona ;Joaquin BraulioDelgadillo-Alvarez ;Marcela Amalia Mercado-Pezzat ;Eli Tonatiuh Selva-Hernandez ;Alejandro Perera-Ortiz ;Jose Alberto Ordufia-Sumaran ;Cecilia Romero-Torres ;Luis Antonio Jimenez-Zamudio ;Ethel AwildaGarcfa-Latorre Citlatepetl Salinas-Lara 《农业科学与技术》2014,(4):277-290
Mexico is considered by different international organizations as a country where the bovine tuberculosis is an endemic problem. However, there are important and consistent improvements in eradicating the disease by the implementation of government policies and with the livestock organization support. The current situation of the program shows good results regarding decreasing the prevalence, and as a consequence, the risk of this disease for public health and animal health, as well as the improvement in animal production and international and national trade. Today, the bovine tuberculosis distribution is almost known in Mexico. In addition, a series of controls and indicators have been established, which allow maintain consistency and reliability in the data that are managed and analyzed. 相似文献
70.
Rodríguez-Muñoz R Ojanguren AF Tregenza T 《Science (New York, N.Y.)》2008,319(5866):1042; author reply 1042
Donald et al. (Reports, 10 August 2007, p. 810) assessed the impact of the European Union's Birds Directive, a conservation policy enacted in 1979, and reported evidence for positive population changes in targeted species. We argue that their conclusions are overstatements based on unsuitable data and inappropriate analyses. 相似文献