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排序方式: 共有207条查询结果,搜索用时 15 毫秒
71.
Chernobyl: a radiobiological perspective 总被引:1,自引:0,他引:1
M Goldman 《Science (New York, N.Y.)》1987,238(4827):622-623
72.
Among vegetable plants, red beet contains a relatively high level of the B vitamin folic acid. Although many leafy green vegetables
contain high levels of folic acid, red beet is consumed primarily as a root vegetable. Folic acid levels have been quantified
in various vegetable plants, but little information exists regarding the accumulation and distribution of this vitamin in
plant tissues. The objective of this study was to characterize free folic acid content (FFAC) in shoot and root tissue during
growth of two red beet inbreds. Experiments were conducted in a greenhouse during 1993, 1994 and 1995. Two inbreds, W384 and
W357, were planted in randomized complete blocks and shoot and root tissues were separately harvested at 60, 80, and 100 days
after planting (DAP). Significant differences between years, tissue portions, and among harvest dates were detected, however,
similar patterns in FFAC accumulation and distribution were observed between inbreds and years. FFAC in shoot tissue was significantly
greater than root tissue for both inbreds. Accumulation of FFAC was linear for both inbreds across harvest dates for root
tissue but not for shoot tissue. FFAC accumulation in shoot tissue increased sharply from 60 to 80 DAP but decreased sharply
from 80 to 100 DAP. These results demonstrate that FFAC accumulates differentially in root and shoot tissue in a red beet
plant. Maximum folic acid levels in shoot tissue are achieved prior to those in root tissue. 相似文献
73.
Thermodilution (TD) is the standard method for cardiac output (CO) monitoring in human medicine. Although called the ‘gold standard’, TD is related to numerous complications and data misinterpretations. Recently, a noninvasive, continuous, ultrasound‐based technique for CO measurement has been developed (Hemosonic 100, Arrow Intl). This study compared transesophageal Doppler ultrasonography (TED) for measuring CO with TD in anesthetized dogs. In this study, ten dogs were used to simultaneously measure CO by TED and TD. All dogs were pre‐medicated with acepromazine at 0.1 mg kg?1 IM, induced with thiopental at 10 mg kg?1 IV, and maintained on isoflurane at end‐tidal concentrations of 1.3%. Baseline and four different levels of CO were used for comparison. Low CO levels were induced by caudal vena cava occlusion. High CO levels were induced by the constant IV infusion of dopamine, dobutamine, or norepinephrine. Each level of CO allowed one comparison between TED and TD. Forty‐nine paired comparisons of CO were determined ranging from 0.73 to 10.9 L minute?1. Simple linear regression was used to determine the correlation between the two techniques. Correlation coefficient (r2) was 0.53. Bland and Altman statistical method was used for assessing agreement between the two methods. The difference between the TD and TED when all data were included was 0.82 (bias) ± 1.63 L minute?1 (mean ± SD). At low CO levels (baseline and caudal vena cava occlusion), the correlation coefficient was 0.77, bias was 0.35 ± 0.64 L minute?1. At high CO levels (dopamine, dobutamine, or norepinephrine), the correlation coefficient was 0.39. It was concluded that TED was not a reliable monitoring method in determining CO when positive inotropes were used. TED might have importance in situations of low CO values; however, further investigation is warranted. 相似文献
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Pinpointing erosional ‘hot spots’ or sediment source areas within a watershed can be difficult because of the highly non-linear and episodic nature of effective runoff and sediment transport. Continuous monitoring of stream networks can provide insight into sediment source areas not possible from routine sampling by capturing episodic events and integrating entire storm events. This paper presents the results of a three-year study of spring snowmelt runoff in watersheds of Lake Tahoe, California, USA, using a network of nine nephelometric turbidometers. We estimate that montane badlands, comprising 1.2% of the Ward Creek watershed (25 km2), contributed 10–39% of snowmelt-derived suspended sediment load. The badlands are comprised of poorly-vegetated and deeply-incised gullies formed in parent material of Miocene volcanic mudflow breccia. The larger (29.5 km2) Blackwood Creek watershed also showed high relative erosion rates from volcanic terrain. Tributaries draining forested granitic and metasedimentary headwater regions had minimal sediment loads. Monitoring networks indicated that temporary main channel storage regulated release of fine sediment eroded from steep headwater slopes. This lag between erosion and delivery may lead to underestimation of gully erosion contribution to sediment budgets. 相似文献
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KR Arrigo DH Robinson DL Worthen RB Dunbar GR DiTullio M VanWoert MP Lizotte 《Science (New York, N.Y.)》1999,283(5400):365-367
Data from recent oceanographic cruises show that phytoplankton community structure in the Ross Sea is related to mixed layer depth. Diatoms dominate in highly stratified waters, whereas Phaeocystis antarctica assemblages dominate where waters are more deeply mixed. The drawdown of both carbon dioxide (CO2) and nitrate per mole of phosphate and the rate of new production by diatoms are much lower than that measured for P. antarctica. Consequently, the capacity of the biological community to draw down atmospheric CO2 and transport it to the deep ocean could diminish dramatically if predicted increases in upper ocean stratification due to climate warming should occur. 相似文献
80.
Echocardiographic values in the Greyhound 总被引:1,自引:0,他引:1
SUMMARY Serial B- and M-mode echocardiography was performed on Greyhounds to determine normal cardiac values for this breed. These were generally of greater magnitude than predicted from previous echocardiographic research on other breeds and crossbreeds. In particular, left ventricular posterior wall thickness, measured at both systole and diastole, was consistently greater. 相似文献