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51.
52.
Two depth profiles of the osmium concentration and the 187Os/186Os isotopic ratio in the Indian Ocean showed that the osmium concentration seems to be unaltered by chemical or biological processes occuring in seawater; accordingly, osmium is conservative. These data were obtained from an experimental method that eliminated the problems related to osmium preconcentration. This method led to a new evaluation of the concentration of osmium in seawater; the mean concentration of osmium and the 187Os/186Os ratio are equal to 10.86 +/- 0.07 picograms per kilogram and 8.80 +/- 0.07, respectively. The results suggest the existence of an organocomplex that dominates the speciation of osmium in seawater. 相似文献
53.
Unconditional quantum teleportation 总被引:5,自引:0,他引:5
A Furusawa JL Sorensen SL Braunstein CA Fuchs HJ Kimble ES Polzik 《Science (New York, N.Y.)》1998,282(5389):706-709
Quantum teleportation of optical coherent states was demonstrated experimentally using squeezed-state entanglement. The quantum nature of the achieved teleportation was verified by the experimentally determined fidelity Fexp = 0.58 +/- 0.02, which describes the match between input and output states. A fidelity greater than 0.5 is not possible for coherent states without the use of entanglement. This is the first realization of unconditional quantum teleportation where every state entering the device is actually teleported. 相似文献
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55.
RL Westemeier JD Brawn SA Simpson TL Esker RW Jansen JW Walk EL Kershner JL Bouzat KN Paige 《Science (New York, N.Y.)》1998,282(5394):1695-1698
Effects of small population size and reduced genetic variation on the viability of wild animal populations remain controversial. During a 35-year study of a remnant population of greater prairie chickens, population size decreased from 2000 individuals in 1962 to fewer than 50 by 1994. Concurrently, both fitness, as measured by fertility and hatching rates of eggs, and genetic diversity declined significantly. Conservation measures initiated in 1992 with translocations of birds from large, genetically diverse populations restored egg viability. Thus, sufficient genetic resources appear to be critical for maintaining populations of greater prairie chickens. 相似文献
56.
Anne B. Alerding Matthew R. Waalkes Emily S. Hill Richard A. Rowe Garrett Parsons 《Journal of Crop Improvement》2018,32(2):156-174
In soybean (Glycine max (L.) Merr.), stems remain a competitive carbon resource sink during reproduction. Radial stem expansion after termination of axial stem growth requires resources to produce secondary cell walls in secondary vascular tissues. The impact of both the timing and extent of secondary growth in stems on fruit production in soybean is unknown. We hypothesized that cultivars gaining higher amounts of secondary vascular tissues during seed filling would experience lower reproductive output. Four determinate cultivars were grown in a greenhouse and harvested at the beginning and ending of seed filling for biomass determination and tissue composition measurement (ImageJ-Fiji). Cultivar ‘Hanover’ entered seed filling with the lowest amount of secondary phloem. It produced the largest increase in radial stem expansion, largest seeds, and fewest undeveloped (aborted) fruits. The physiological role of active secondary phloem production in stems for seed production in soybean reproduction is unclear. We reject our initial hypothesis and propose that high fitness may require the concomitant growth of vegetative and reproductive organs. 相似文献
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Diagnosis of laryngeal dysplasia in five horses using magnetic resonance imaging and ultrasonography
K. S. Garrett J. B. Woodie R. M. Embertson A. P. Pease 《Equine veterinary journal》2009,41(8):766-771
Reasons for performing study: Laryngeal dysplasia due to suspected maldevelopment of the fourth branchial arch has been reported previously in the horse and has been associated with rostral displacement of the palatopharyngeal arch and/or right laryngeal dysfunction. These studies all described the endoscopic and/or anatomical post mortem identification of the disease, but ultrasonography or magnetic resonance imaging (MRI) of this disease have not been described. Hypothesis: MRI and ultrasound findings accurately reflect the anatomical features of presumptive fourth branchial arch abnormality and allow accurate ante mortem diagnosis of this condition and, therefore, appropriate management. Methods: Between February 2008 and January 2009, all horses examined at Rood and Riddle Equine Hospital diagnosed with rostral displacement of the palatopharyngeal arch and/or right laryngeal dysfunction using upper airway endoscopy (n = 5) underwent ultrasonography and MRI of the laryngeal region. Results: All 5 horses that met the inclusion criteria were identified and all underwent laryngeal MRI and ultrasound examinations. Features consistent with laryngeal dysplasia, including lack of the cricothyroid articulation, dorsal extension of the thyroid cartilage lamina, and absence or hypoplasia of the cricopharyngeus muscle, were seen in all cases using both types of imaging. Conclusions and potential relevance: MRI and ultrasonography permit definitive premortem diagnosis of laryngeal dysplasia. Upper airway abnormalities identified using endoscopy can be more fully characterised using MRI and ultrasonography allowing more appropriate recommendations to be made. Preoperative imaging may also prevent inappropriate surgical intervention. 相似文献
59.
B Serrano F López-Gatius P Santolaria S Almería I García-Ispierto G Bech-Sabat J Sulon NM de Sousa JF Beckers JL Yániz 《Reproduction in domestic animals》2009,44(4):600-605
This study was designed to establish the factors, if any, which could affect plasma pregnancy-associated glycoprotein-1 (PAG-1) expression in a study population of 87 pregnant, high-producing dairy cows. The factors examined were: semen providing breed (Holstein-Friesian vs Limousin), outcome of gestation (male vs female newborn, and singleton vs twin pregnancies), lactation number, milk production at pregnancy diagnosis, plasma progesterone concentration, season of gestation (warm period, March–November vs cool period, December–February), and day of gestation (40, 90, 120, 150, 180 and 210). Pregnancy was diagnosed by transrectal ultrasound on day 40 post-insemination and by palpation per rectum on days 90, 120, 150, 180 and 210. Blood samples were collected from each animal immediately before each pregnancy diagnosis. The relative contributions of the different factors on PAG-1 concentrations were evaluated by GLM repeated measures analysis of variance. No significant effects of the herd, foetal sex, milk production, lactation number and plasma progesterone concentrations were observed. In contrast, twin pregnancy, the use of Limousin semen and conception during the cool period were correlated with significantly increased plasma PAG-1 concentrations throughout gestation. Our data indicate that both cow well-being during early placental development, determined in our conditions by reduced heat stress when conception occurred in the cool season, and crossbreed pregnancies lead to improved PAG-1 production throughout the gestation period. 相似文献
60.
AEF Silva P Rodriguez LF Cavalcante BA Rodrigues JL Rodrigues 《Reproduction in domestic animals》2009,44(S2):259-262
High in vitro oxygen (O2 ) tensions are associated with enhanced levels of reactive oxygen species and cumulus oocyte complex (COC) apoptosis. The objective of this study was to determine the influence of O2 tension on cumulus cell (CC) viability from canine oocytes. Cumulus oocyte complexes were distributed into three groups (CG, T20 and T5) and two O2 tension levels (20% and 5%). The control group (CG) was matured in vitro in a humidified atmosphere with 5% CO2 in air in TCM199 with 26.19 m m sodium bicarbonate, 10% (v/v) foetal calf serum (FCS), 0.10 m m gentamicin, 0.20 m m pyruvic acid, 20 μg/ml oestradiol, 0.5 μg/ml follicle-stimulating hormone, 0.03 IU/ml human chorionic gonadotropin, and 1.0 μg/ml human somatotropin. Groups T20 and T5 were matured under 20% or 5% O2 tensions respectively in a high-glucose medium, without FCS. T20 and T5 were as CG, and supplemented with 0.1% Polyvinyl Alcohol, and 5.5 m m glucose. After 48 h of IVM, CCs from COCs were stained with propidium iodide (1.50 m m ). The results showed that viability of CCs (cytoplasmic features and nuclear morphological integrity) was different for the three groups. Rates of apoptosis were at 57.9% (521/900) for CG, 54.4% (490/900) for T20 and 38.9% (350/900) for T5 (p < 0.001). Predominant features in apoptotic cells (n = 1361) were DNA nuclear fragments (94.0%). It was concluded that CCs of canine COCs cultured in high-glucose medium showed significantly less apoptosis than those cultured in medium with FCS. Low O2 tension was efficient in reducing apoptosis in canine CCs. 相似文献