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Measurements of electrical conductivity at high pressure and temperature were taken on the lower mantle phase magnesiowustite with varying Fe3+ content. Although previous measurements at atmospheric pressure suggest Fe2+-Fe3+ hopping (small polaron) as the dominant conductivity mechanism, the present experiments show a change in charge transport mechanism with temperature. The lower temperature measurements are consistent with small polaron conduction, but at higher temperatures, which are more applicable to the lower mantle, a large polaron mechanism is suggested. Because these mechanisms have different temperature and compositional dependencies, this transition has important implications for extrapolation to mantle conditions. 相似文献
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Carroll JA Burdick NC Chase CC Coleman SW Spiers DE 《Domestic animal endocrinology》2012,43(2):146-153
Although livestock experience many stressors throughout their life, one of the most commonly experienced, and most difficult to control, is stress caused by fluctuations in environmental temperatures that extend beyond the thermoneutral (TN) zone for an animal. In swine, cold stress has long been recognized as a main cause of neonatal morbidity and mortality. A possible explanation for this increased morbidity and mortality may be related to their inability to generate a febrile response. Previously, we reported that the acute phase immune response, including the generation of fever, after exposure to lipopolysaccharide (LPS; Escherichia coli O111: B4; Sigma-Aldrich, St Louis, MO, USA) is substantially altered in neonatal pigs maintained in a cold environment (ie, 18°C). Neonatal pigs that were maintained in a cold environment and administered LPS experienced a period of hypothermia coupled with altered endocrine and proinflammatory cytokine responses that could prove detrimental. In cattle, we previously reported differences in the acute phase immune response of two diverse breeds of Bos taurus cattle (Angus and Romosinuano) when maintained under TN conditions and exposed to LPS. More recently we have reported that differences in the stress and immune responses of Angus and Romosinuano heifers varies, depending on whether the cattle were housed at either TN or heat stress air temperatures. Our data clearly show that even intermittent periods of heat stress similar to that experienced in production environments can have significant effects on the stress and innate immune responses of cattle. Understanding the effect of thermal stress on livestock is critical to developing and implementing alternative management practices to improve their overall health and well-being. 相似文献
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SJ Glaser T Schulte-Herbruggen M Sieveking O Schedletzky NC Nielsen OW Sorensen C Griesinger 《Science (New York, N.Y.)》1998,280(5362):421-424
Experiments in coherent magnetic resonance, microwave, and optical spectroscopy control quantum-mechanical ensembles by guiding them from initial states toward target states by unitary transformation. Often, the coherences detected as signals are represented by a non-Hermitian operator. Hence, spectroscopic experiments, such as those used in nuclear magnetic resonance, correspond to unitary transformations between operators that in general are not Hermitian. A gradient-based systematic procedure for optimizing these transformations is described that finds the largest projection of a transformed initial operator onto the target operator and, thus, the maximum spectroscopic signal. This method can also be used in applied mathematics and control theory. 相似文献
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M Aksoy H Erdem F Hatipolu NC Lehimciolu O Akman K Özkan 《Reproduction in domestic animals》2009,44(1):156-160
This study was performed to describe a practical technique for ultrasound examination of the scrotal content of the rabbit. The scrotal content of normal rabbits and those with induced lesions (i.e. needle biopsy of the testis and epididymal ligation) were viewed using a portable scanner connected to a 5 or 7.5 MHz real time, B-mode linear array transducer. The effect of frequency (5 and 7.5 MHz), pad material placed under the testicle (rubber, plastic and carton) and the presence of a water sack between the probe and organ were examined to optimize the technique. The best image quality was obtained using a 5-MHz probe when the testicle was fixed on a rubber pad and covered by a water sack. Testicular parenchyma was imaged as homogeneous and moderately echoic. Caput and cauda epididymis were identified as homogeneous and less echoic compared with the testis parenchyma. Variations in the testicular echotexture that occur secondarily to epididymal ligation and testis biopsy could be screened readily. In conclusion, real-time ultrasonography, performed as described in this study, may provide a valuable tool to screen scrotal contents and to identify certain pathological conditions that affect fertility in the rabbit. 相似文献
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Carroll JA Burdick NC Reuter RR Chase CC Spiers DE Arthington JD Coleman SW 《Domestic animal endocrinology》2011,41(4):163-173
Our primary objective of this experiment was to evaluate potential genetic differences between two diverse Bos taurus breeds [Angus (AG) and Romosinuano (RO)] in response to an endotoxin challenge. Eighteen steers (n = 9 steers/breed; 299.4 ± 5.2 kg BW) were acclimated to environmentally controlled chambers maintained at thermoneutrality (19.7 °C) and then fitted with indwelling jugular catheters and rectal temperature (RT) recording devices 1 d before the endotoxin challenge. The next day, blood samples were collected at 30-min intervals from −2 to 8 h, and RT was measured continuously at 1-min intervals throughout the study. At time 0, all steers received an intravenous bolus injection of lipopolysaccharide (LPS; 2.5 μg/kg BW). Serum samples were stored at −80 °C until analyzed for cortisol, proinflammatory cytokines [tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and interferon gamma (IFN-γ)], and acute phase proteins (serum amyloid A, acid soluble protein, ceruloplasmin, and α-acid glycoprotein). Rectal temperatures increased in both breeds within 1 h after LPS, with RO producing a greater increase in RT than AG steers (P < 0.001). Serum cortisol and TNF-α increased (P < 0.01) in both breeds within 1 h after the LPS challenge. For cortisol, an overall breed effect (P < 0.02) was detected, such that AG steers had a higher cortisol response than RO steers. A breed × time interaction (P < 0.01) was observed for TNF-α, such that the response was delayed and extended in the RO steers compared with the AG steers. At 2 and 2.5 h after LPS, TNF-α concentrations were greater (P < 0.03) in RO steers than in AG steers. For IL-1β, a breed × time interaction (P < 0.04) was also observed. At 3 h after LPS, IL-1β concentrations were greater (P < 0.01) in RO steers than in AG steers. Serum IL-6 and IFN-γ increased (P < 0.01) in a similar manner in both groups after the LPS challenge. These data show differences in the innate immune response between two diverse Bos taurus breeds which may provide insight about differences observed in productivity, heat tolerance, disease resistance, and longevity among cattle breeds. 相似文献
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May JJ Sorensen JA Burdick PA Earle-Richardson GB Jenkins PL 《Journal of agricultural safety and health》2006,12(3):199-213
Tractor overturns contribute significantly to fatalities in New York State agriculture. On-site inspections a decade ago indicated that approximately 60% of tractors were without effective rollover protection. Our objectives were: to describe the current prevalence and distribution of rollover protective structures (ROPS) on New York farm tractors, to identify characteristics associated with the absence of ROPS, to explore segmenting the New York farm community on readiness for ROPS retrofitting, and to identify demographic characteristics that might assist in this segmenting. A random selection of 644 livestock, dairy, fruit, cash crop, vegetable, and organic farms were contacted for a telephone survey. Of 562 farms (87%) participating, 102 (18.1%) had all tractors equipped with ROPS and 138 (24.6%) had none. A disproportionate number of livestock, cash crop, and organic operations had no ROPS. Rates of ROPS-equipped tractors correlated directly with farm size and annual hours of tractor operation. Older farmers had a lower proportion of ROPS tractors. The presence of a child operator did not affect the proportion of ROPS tractors. After weighting the sample, the total number of non-ROPS tractors in New York is estimated at more than 80,000. In addition to providing key farm demographics, the survey enabled placement of farmers on a "stage of change" continuum related to readiness for retrofitting. Three-quarters of New York farmers are in the "precontemplation" stage of change relative to ROPS retrofitting, and this varies little by size of operation, age of farmer, or the presence of child tractor operators. Stage of change may relate to hours of tractor operation (p = 0.05) and does relate to commodity (p = 0.003) due primarily to the higher proportion of crop farmers in the earliest stage of change. The goal of retrofitting all New York farm tractors with ROPS appears nearly as daunting as it did a decade ago. 相似文献