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排序方式: 共有203条查询结果,搜索用时 15 毫秒
31.
32.
WC Feldman BL Barraclough S Maurice RC Elphic DJ Lawrence DR Thomsen AB Binder 《Science (New York, N.Y.)》1998,281(5382):1489-1493
Global maps of thermal and fast neutron fluxes from the moon suggest three end-member compositional units. A high thermal and low fast neutron flux unit correlates with the lunar highlands and is consistent with feldspathic rocks. The South Pole-Aitken basin and a strip that surrounds the nearside maria have intermediate thermal and fast neutron flux levels, consistent with more mafic rocks. There appears to be a smooth transition between the most mafic and feldspathic compositions, which correspond to low and high surface altitudes, respectively. The maria show low thermal and high fast neutron fluxes, consistent with basaltic rocks. 相似文献
33.
RA Periana DJ Taube S Gamble H Taube T Satoh H Fujii 《Science (New York, N.Y.)》1998,280(5363):560-564
Platinum catalysts are reported for the direct, low-temperature, oxidative conversion of methane to a methanol derivative at greater than 70 percent one-pass yield based on methane. The catalysts are platinum complexes derived from the bidiazine ligand family that are stable, active, and selective for the oxidation of a carbon-hydrogen bond of methane to produce methyl esters. Mechanistic studies show that platinum(II) is the most active oxidation state of platinum for reaction with methane, and are consistent with reaction proceeding through carbon-hydrogen bond activation of methane to generate a platinum-methyl intermediate that is oxidized to generate the methyl ester product. 相似文献
34.
RC Elphic DJ Lawrence WC Feldman BL Barraclough S Maurice AB Binder PG Lucey 《Science (New York, N.Y.)》1998,281(5382):1493-1496
The Lunar Prospector neutron spectrometer data correlate well with iron and titanium abundances obtained through analysis of Clementine spectral reflectance data. With the iron and titanium dependence removed, the neutron spectrometer data also reveal regions with enhanced amounts of gadolinium and samarium, incompatible rare earth elements that are enriched in the final phases of magma crystallization. These regions are found mainly around the ramparts of the Imbrium impact basin but not around the other basins, including the much larger and deeper South Pole-Aitken basin. This result confirms the compositional uniqueness of the surface and interior of the Imbrium region. 相似文献
35.
36.
GT Bleck MB Wheeler LB Hansen H Chester-Jones DJ Miller 《Reproduction in domestic animals》2009,44(2):241-247
It is believed that milk production is determined by the number and activity of mammary secretory cells. Secretory activity, as assessed by milk volume, depends on secretion of the major osmole in milk, lactose, which is produced by lactose synthase. The amount of either of the two proteins in lactose synthase may regulate milk production. The objective of this study was to determine whether the concentrations in milk of the two components of lactose synthase, α‐lactalbumin (α‐LA) and β1,4‐galactosyltransferase (B4GALT), were related to genetic background, stage of lactation, breed or parity of dairy cows. α‐Lactalbumin and B4GALT concentrations were measured by ELISA and by enzyme assays, respectively, from single milk samples. Two herds with a total of 279 cows were used in the analysis. One herd contained Ayrshire, Brown Swiss, Holstein and Jersey cows; the second herd contained two groups of cows; Holsteins selected for high milk production and Holsteins with 1960s genetics. The α‐LA concentration in milk was greater in Jerseys and Ayrshires than in Holsteins and Brown Swiss. However, no difference in α‐LA concentration was observed in milk from high and low genetic merit cows in the Minnesota herd or among different genetic backgrounds in the Illinois herd. β1,4‐Galactosyltransferase concentrations were similar for all groups that were analyzed. α‐Lactalbumin concentrations were positively correlated with milk protein concentration, milk fat concentration and lactose concentration. β1,4‐Galactosyltransferase concentration in milk exhibited a strong positive correlation with number of days in milk. Although the concentration of B4GALT increased as lactation progressed, the values did not show any correlation with persistency of lactation or late lactation milk production. In conclusion, this survey shows that the two components of lactose synthase are each correlated to protein concentration and individually correlated to the concentration of other milk components and stage of lactation. 相似文献
37.
Objective Part 1: compare the use of a Metricheck™ device (a stainless steel probe with a semi-spherical rubber cup attached at one end) to sample the contents of the anterior vagina with a vaginal speculum examination for the diagnosis of pus in the vagina of postpartum dairy cows and to investigate the association of that pus with reproductive performance. Part 2: assess the effect of a single intrauterine infusion of 500 mg cephapirin in cows diagnosed with vaginal purulent or mucopurulent discharge 7 to 28 days after calving on reproductive performance.
Procedure Six herds were visited fortnightly to examine cows that had calved between 7 and 28 days (n = 423) with both the Metricheck device and a vaginal speculum to score, by each method, the vaginal discharge from 0 (clear or absent) to 3 (purulent) for each animal included in the study. Half of the cows that had a positive discharge score (1 to 3 by either examination method) were then treated with an intrauterine infusion of 500 mg of cephapirin. The relationship between Metricheck score, vaginoscopy score, treatment and reproductive performance was assessed.
Results There was a substantial measure of agreement between each method when scores were analysed by status. Cows that were positive with either method had inferior reproductive performance compared with cows with a score of zero. Treatment of cows diagnosed with a purulent or mucopurulent discharge with intrauterine cephapirin improved reproductive performance in both the vaginoscopy and Metricheck groups. 相似文献
Procedure Six herds were visited fortnightly to examine cows that had calved between 7 and 28 days (n = 423) with both the Metricheck device and a vaginal speculum to score, by each method, the vaginal discharge from 0 (clear or absent) to 3 (purulent) for each animal included in the study. Half of the cows that had a positive discharge score (1 to 3 by either examination method) were then treated with an intrauterine infusion of 500 mg of cephapirin. The relationship between Metricheck score, vaginoscopy score, treatment and reproductive performance was assessed.
Results There was a substantial measure of agreement between each method when scores were analysed by status. Cows that were positive with either method had inferior reproductive performance compared with cows with a score of zero. Treatment of cows diagnosed with a purulent or mucopurulent discharge with intrauterine cephapirin improved reproductive performance in both the vaginoscopy and Metricheck groups. 相似文献
38.
Equine amnionitis and fetal loss: The case definition for an unrecognised cause of abortion in mares
KH Todhunter NR Perkins RM Wylie C Chicken AJ Blishen DJ Racklyeft G Muscatello MC Wilson PL Adams JR Gilkerson WL Bryden AP Begg 《Australian veterinary journal》2009,87(1-2):35-38
A series of abortions occurred in mares in New South Wales during 2004 that involved similar and unusual findings on post mortem examination of aborted fetuses and fetal membranes. The term Equine Amnionitis and Fetal Loss (EAFL) was developed to describe the condition. This form of abortion had not been previously recognised in Australia. The pathology alone is not specific for EAFL and diagnosis requires demonstration of a combination of certain pathological and bacteriological features. The purpose of this paper is to describe patterns considered consistent with EAFL cases as a working case definition for use by veterinarians and veterinary pathologists in identifying future cases of EAFL. More detailed papers are in preparation to fully describe the epidemiological, histopathological, and microbiological aspects of EAFL. 相似文献
39.
AJ Korzekwa TJ Acosta M Miklewicz K Okuda SH Lee DJ Skarzynski 《Reproduction in domestic animals》2010,45(6):e288-e296
The aim of this study was to determine which cells are the source of production and target for leukotriene (LTs) action within the bovine ovary. Luteal (CL, days 14–16 of the oestrous cycle), steroidogenic cells (LSC) and endothelial cells (LEC) of the bovine corpus luteum (CL), and granulosa cells (GC) were isolated enzymatically, cultured in a monolayer and incubated with LTC4, LTB4, Azelastine (an antagonist of LTC4) or Dapsone (an antagonist of LTB4). Then cells were collected for determination of mRNA expression for LT receptors (LTRs) and 5‐lipoxygenase (5‐LO) by real time RT‐PCR, and media were collected for determination of prostaglandin (PG)E2, F2α, progesterone (P4; LSC only), endothelin‐1 (ET‐1; LEC only) and 17‐β oestradiol (E2; GC only). The greatest mRNA expression for LTR‐II and 5‐LO were found in LEC, whereas LTR‐I mRNA expression did not differ among cell types. The level of PGE2 increased after LTs treatment in each type of ovarian cell, excluding LTC4 treatment in LEC. The secretion of PGF2α was also increased by LTs, but decreased after LTB4 treatment of LSC. In GC cultures, both LTs stimulated E2 secretion; in LEC cultures, LTB4 stimulated whereas LTC4 inhibited P4 secretion; in LEC cultures, LTC4 stimulated but LTB4 inhibited ET‐1 secretion. The results show that LTs are produced locally and are involved in PGs production/secretion in all examined cells (LSC, LEC and GC) of bovine ovary. Leukotriene treatment modulate secretion of E2, by GC, P4 by LSC and ET‐1 by LEC, which indicates that LTs are involved in regulation of ovarian secretory functions. 相似文献
40.
DJ STEWART JA VAUGHAN TC ELLEMAN† PA HOYNE† KJ BURNS JH DUFTY 《Australian veterinary journal》1991,68(2):50-53
The relationship between the serological classification system for serogroup B and for serogroup H of Bacteroides nodosus and cross-protection between subgroups within these serogroups was examined. Protection against ovine footrot following vaccination was achieved against other subgroup strains provided sufficient cross-reactive antibody was induced by shared pilus antigens. Within serogroup B, better cross-protection against one subgroup was obtained with a pili vaccine than a whole cell vaccine which correlated with higher pilus antibody titres induced by the former. For serogroup H, a lack of cross-protection and serological reactivity between subgroups was demonstrated, which indicates that the prototype strain of subgroup H2 should be designated a new serogroup. 相似文献