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排序方式: 共有754条查询结果,搜索用时 15 毫秒
41.
H. Clayton I. P. McTaggart J. Parker L. Swan K. A. Smith 《Biology and Fertility of Soils》1997,25(3):252-260
The aim was to investigate the effects of different N fertilisers on nitrous oxide (N2O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N2O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam
grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry
supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N2O flux and soil and environmental variables. The loss of N2O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from
AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower
than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled
pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total
annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2,
1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd
year gave an average emission factor of 0.8% – lower than from application of either individual fertiliser. We suggest that
similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed
to minimise N2O emissions from agricultural land.
Received: 30 August 1996 相似文献
42.
Evaluation of two commercial test kits for detection of occult blood in feces of dogs 总被引:1,自引:0,他引:1
To evaluate the sensitivity and specificity of 2 commercial test kits for detection of occult blood in canine feces, various volumes of blood were administered to 6 dogs via orogastric tube. Blood volumes tested were chosen on the basis of hemoglobin quantities of 5, 10, 20, 200, 350, and 500 mg of hemoglobin/kg of body weight. Fecal specimens were collected twice daily and analyzed separately by 2 observers for the presence of occult blood by use of modified guaiac and orthotolodine tablet tests, and for melena by visual inspection. Five dogs given blood at the rate of 500 mg of hemoglobin/kg and 1 dog given blood at the rate of 350 mg of hemoglobin/kg developed melena. Results of both occult blood tests were positive in 2 of 6 dogs given blood at the rate of 5 mg of hemoglobin/kg. Five of 6, and 4 of 6 dogs given blood at the rate of 10 mg hemoglobin/kg had positive test results by modified guaiac and orthotolodine methods, respectively. Results of both methods were positive in all dogs given blood at the rate of 20 mg of hemoglobin/kg. There was 86% agreement between the 2 observers' results for the modified guaiac method, and 78% agreement for the orthotolodine method. There was 77% agreement of results between the 2 test methods. Gastrointestinal transit time decreased with increasing volumes of blood. Occult blood testing was found to be useful for detection of blood in feces at volumes 20 to 50 times less than that required to cause melena. 相似文献
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44.
J W Tyler J S Cullor M C Thurmond V L Douglas K M Parker 《American journal of veterinary research》1990,51(9):1400-1406
Logistic regression was used to develop models predicting preweaning survival in 334 neonatal swine. Measured risk factors included birth weight, litter size (live born), dam parity, serum IgG concentration, serum ELISA titers recognizing common gram-negative core antigens, and serum concentrations of the third component of complement. Larger birth weights were associated with increased probability of preweaning survival. The highest mortality was observed in litters with more than 12 pigs. Pigs with serum concentration of the third component of complement (C3) in the lowest stratum, less than 20% adult pooled C3 standard (APC3), had reduced mortality, compared with high (greater than 38% APC3) and middle (20 to 38% APC3) groups. Associations between all other variables, including total serum IgG concentration and preweaning survival were not significant. Few pigs had hypogammaglobulinemia, less than 3% of the study population had serum IgG concentrations less than 1 g/dl. Of all measured variables, only birth weight and dam parity were significant predictors of preweaning gain. Larger pigs and pigs born to third or greater parity dams had more preweaning gain than other pigs. 相似文献
45.
46.
Parker JS 《Journal of the American Veterinary Medical Association》2007,230(5):657; author reply 657-657; author reply 658
47.
The NeuroScope, a specific and sensitive indicator of cardiac vagal tone, was used to look for differences in autonomic tone between 25 dogs with naturally occurring diabetes mellitus and 23 healthy control dogs, to determine whether there was any correlation between the dogs' cardiac vagal tone, the duration of diabetes and the adequacy of glycaemic control. The cardiac index of parasympathetic activity (cipa) was determined for each dog over a period of 2600 heartbeats. The mean, median and modal cipa values were significantly lower in the diabetic dogs than in the healthy dogs. There was no significant relationship between the cipa values and the duration of disease or the adequacy of recent glycaemic control in the diabetic dogs, but there was a significant inverse relationship between the cipa values and the bodyweight of the diabetic dogs that was not evident in the normal dogs. The conclusions were based on a 500-heartbeat interval selected from the 2600 heartbeats recorded. 相似文献
48.
Adams RL Mottram DS Parker JK Brown HM 《Journal of agricultural and food chemistry》2001,49(9):4333-4336
The irreversible binding of selected sulfur-containing flavor compounds to proteins was investigated in aqueous solutions containing ovalbumin and a mixture of disulfides (diethyl, dipropyl, dibutyl, diallyl, and 2-furfuryl methyl) using solid-phase micro-extraction (SPME). In systems which had not been heated, the recovery of disulfides from the headspace above the protein at the native pH (6.7) was similar to that from an aqueous blank. However, significant losses were observed when the pH of the solution was increased to 8.0. When the protein was denatured by heating, much greater losses were observed and some free thiols were produced. In similar heat-denatured systems at pH 2.0, no losses of disulfides were observed. Disulfides containing allyl or furfuryl groups were more reactive than saturated alkyl disulfides. Interchange reactions between protein sulfhydryl groups and the disulfides are believed to be responsible for the loss of the disulfides. 相似文献
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