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61.
Data from two Lunar Orbiter spacecraft have been used to test the significance of corrections to the lunar ephemeris. Range residuals of up to 1700 meters were reduced by an order of magnitude by application of the corrections, with most of the residuals reduced to less than 100 meters. Removal of gross errors in the ephemeris reveals residual patterns that may indicate errors in location of observing stations, as well as the expected effects of Lunar nonsphericity. 相似文献
62.
63.
Animal welfare is expected to increase in importance as a political and marketing issue. There is a vigorous debate about what, besides the absence of physical pain, is necessary for acceptable animal welfare. This paper focuses on the present state of animal welfare policy at the national level. 相似文献
64.
Lunar laser range measures covering the period 1969 to 1976 have been used to determine the anomalous secular acceleration in the mean longitude of the moon, commonly attributed to the effect of tidal friction in the earth. The acceleration determined is -24.6 +/- 1.6 arc seconds per century squared, against an atomic time scale, where the uncertainty is the formal standard deviation of the solution. The realistic uncertainty is surely larger, as evidenced by the ensemble of solutions performed with various models and observation sets. The determined value is in good agreement with the conventional value and with several recent determinations by other methods. An attempt to determine the rate of change of the mean distance, essential for separating the tidal effect from a time variation of the gravitational constant, yielded no significant result, because the observations still span too short a time. 相似文献
65.
66.
Susan D. Wharam Vincent Mulholland George P. C. Salmond 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(1):1-13
Recent research has revealed the emergence of common themes in the molecular mechanisms of virulence in bacterial pathogens of plants and animals. In particular, the systems used for the global control of virulence factor synthesis and for the secretion of virulence determinants in diverse bacterial pathogens show strong conservation, implying evolutionary relatedness. Global control of virulence factor synthesis can be affected by a variety of environmental factors, bacterial hormones and programmed genetic rearrangements.Protein secretion in Gram-negative bacteria occurs via a number of targeting pathways. Type I and type III secretion systems mediate translocation across both the inner and outer membrane in a single step, while type II secretion proceeds via a periplasmic intermediate. Type II and type III secretion systems have been shown to target virulence determinants in both plant and animal bacterial pathogens.Abbreviations Cel
cellulase
- EPS
extracellular polysaccharide
- HL
homoserine lactone
- OHHL
N-(3-oxohexanoyl)-l-homoserine lactone
- PC
phenotypic conversion
- Pel
pectate lyase
- pv.
pathovar
- spp.
species 相似文献
67.
RA McKenzie AM Carmichael ML Schibrowski SA Duigan JA Gibson JD Taylor 《Australian veterinary journal》2009,87(1-2):27-32
Polioencephalomalacia was diagnosed histologically in cattle from two herds on the Darling Downs, Queensland, during July–August 2007. In the first incident, 8 of 20 18-month-old Aberdeen Angus steers died while grazing pastures comprising 60% Sisymbrium irio (London rocket) and 40% Capsella bursapastoris (shepherd's purse). In the second incident, 2 of 150 mixed-breed adult cattle died, and another was successfully treated with thiamine, while grazing a pasture comprising almost 100% Raphanus raphanistrum (wild radish). Affected cattle were either found dead or comatose or were seen apparently blind and head-pressing in some cases. For both incidents, plant and water assays were used to calculate the total dietary sulfur content in dry matter as 0.62% and 1.01% respectively, both exceeding the recommended 0.5% for cattle eating more than 40% forage. Blood and tissue assays for lead were negative in both cases. No access to thiaminase, concentrated sodium ion or extrinsic hydrogen sulfide sources were identified in either incident. Below-median late summer and autumn rainfall followed by above-median unseasonal winter rainfall promoted weed growth at the expense of wholesome pasture species before these incidents. 相似文献
68.
A study was conducted to evaluate the effects of postpartum prostaglandin treatment on reproduction in 3 seasonal calving dairy herds. Recently calved lactating dairy cows were paired on herd, age, calving date and previous production index. One cow in each of the 196 pairs received a single intramuscular injection of 25 mg of the prostaglandin analogue, dinoprost, between 14 and 28 days after calving. Subsequent reproduction was monitored. Within each herd and overall, there was no significant effect of treatment on the intervals from calving to first service, mating start date to first service, calving to conception, mating start date to conception and first service to conception. Treatment also had no significant effect on 21-day submission and pregnancy rates, on the proportion of each group not pregnant at the end of mating, and on first service pregnancy rates. Responses to treatment did not vary between cows calving within 50 days of mating start date and earlier calving cows or between cows aged less than 5 years and older cows. 相似文献
69.
Two-year toxicity and carcinogenicity study of methyleugenol in F344/N rats and B6C3F(1) mice 总被引:2,自引:0,他引:2
Johnson JD Ryan MJ Toft JD II Graves SW Hejtmancik MR Cunningham ML Herbert R Abdo KM 《Journal of agricultural and food chemistry》2000,48(8):3620-3632
Methyleugenol (MEG) was tested for toxicity/carcinogenicity in a 2-yr carcinogenesis bioassay because of its widespread use in a variety of foods, beverages, and cosmetics as well as its structural resemblance to the known carcinogen safrole. F344/N rats and B6C3F(1) mice (50 animals/sex/dose group) were given MEG suspended in 0.5% methylcellulose by gavage at doses of 37, 75, or 150 mg/kg/day for 2 yr. Control groups (60 rats/sex and 50 mice/sex) received only the vehicle. A stop-exposure group of 60 rats/sex received 300 mg/kg/day by gavage for 53 weeks followed by the vehicle only for the remaining 52 weeks of the study. A special study group (10 animals/sex/species/dose group) were used for toxicokinetic studies. All male rats given 150 and 300 mg/kg/day died before the end of the study; survival of female rats given 150 mg/kg/day and all treated female mice was decreased. Mean body weights of treated male and female rats and mice were decreased when compared to control. Area under the curve results indicated that greater than dose proportional increases in plasma MEG occurred for male 150 and 300 mg/kg/day group rats (6 and 12 month) and male 150 mg/kg/day mice (12 month). Target organs included the liver, glandular stomach, forestomach (female rats) and kidney, mammary gland, and subcutaneous tissue (male rats). Liver neoplasms occurred in all dose groups of rats and mice and included hepatoadenoma, hepatocarcinoma, hepatocholangioma (rats only), hepatocholangiocarcinoma, and hepatoblastoma (mice only). Nonneoplastic liver lesions included eosinophilic and mixed cell foci (rats only), hypertrophy, oval cell hyperplasia, cystic degeneration (rats only), and bile duct hyperplasia. Mice also exhibited necrosis, hematopoietic cell proliferation, and hemosiderin pigmentation. Glandular stomach lesions in rats and mice included benign and malignant neuroendocrine tumors, neuroendocrine cell hyperplasia, and atrophy and in mice included glandular ectasia/chronic active inflammation. In female rats, the forestomach showed a positive trend in the incidences of squamous cell papilloma or carcinoma (combined). Male rats also exhibited kidney (renal tubule hyperplasia, nephropathy, and adenomacarcinoma), mammary gland (fibroadenoma), and subcutaneous tissue (fibroma, fibrosarcoma) lesions. Male rats also exhibited malignant mesotheliomas and splenic fibrosis. These data demonstrate that MEG is a multisite, multispecies carcinogen. 相似文献
70.
Compressibility, Phase Transitions, and Oxygen Migration in Zirconium Tungstate, ZrW2O8 总被引:1,自引:0,他引:1
JSO Evans Z Hu JD Jorgensen DN Argyriou S Short AW Sleight 《Science (New York, N.Y.)》1997,275(5296):61-65
In situ neutron diffraction experiments show that at pressures above 2 kilobars, cubic zirconium tungstate (ZrW2O8) undergoes a quenchable phase transition to an orthorhombic phase, the structure of which has been solved from powder diffraction data. This phase transition can be reversed by heating at 393 kelvin and 1 atmosphere and involves the migration of oxygen atoms in the lattice. The high-pressure phase shows negative thermal expansion from 20 to 300 kelvin. The relative thermal expansion and compressibilities of the cubic and orthorhombic forms can be explained in terms of the "cross-bracing" between polyhedra that occurs as a result of the phase transition. 相似文献