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21.
Farideh Z. Bischoff PhD Dorothy E. Lewis Joe Leigh Simpson Dianne D. Nguyen Jeffrey Scott Wendy Schober Sarah Murrell Sherman Elias 《黑龙江环境通报》1995,15(12):1182-1184
Recovering and analysing fetal erythrocytes from maternal blood is being pursued for non-invasive prenatal genetic diagnosis. We report the observation of 46, XY/47, XXY mosaicism in fetal cells from a woman whose first-trimester chorionic villus sampling (CVS) initially showed only 46, XY. Only after exhaustive (500 cells) analysis were four XXY cells found in cultured villi. 相似文献
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23.
David Jeffrey Gray D.O. Haynes B. Robinson James Malone Richard B. Thomson Jr 《黑龙江环境通报》1992,12(2):111-117
Infections in pregnancy with Ureaplasma urealyticum have been associated with a wide range of adverse outcomes, such as early abortion, stillbirth, prematurity, and neonatal morbidity and mortality. Causality has been difficult to demonstrate secondary to the high prevalence of asymptomatic lower genital tract (LGT) colonization and culture data from inaccessible or potentially contaminated sites. Between 1985 and 1989, 2461 second-trimester genetic amniocenteses were evaluated at the cytogenetics section of the Children's Hospital Medical Center of Akron. All were cultured for the genital mycoplasmas: Mycoplasma hominis and Ureaplasma urealyticum. A total of nine patients were positive, all for Ureaplasma urealyticum, with one patient excluded because of subsequent therapeutic abortion. In addition, complete follow-up data, such as indication for amniocentesis, serum alpha-fetoprotein levels, gestational age at parturition, and out- come of pregnancy, were available on 86 Ureaplasma-negative (U –) patients during an approximate 2-year span within the time-frame of the study. This was in part due to physician response to a questionnaire sent after amniocentesis. Of the eight positive cultures, 100 per cent were associated with an adverse outcome, defined as fetal loss or premature delivery. This was significant compared with the U–group (p<0.001) with a more than eight times greater risk of adverse outcome. Six (75 per cent) resulted in spontaneous miscarriage within 4 weeks of amniocentesis and at less than 21 weeks' gestation. Two (25 per cent) delivered prematurely, with one (12.5 per cent) neonatal death at 24+ weeks. Histological examination of all eight placentae and the seven fetuses revealed a 100 per cent incidence of chorioamnionitis and pneumonia, respectively. In addition, in four of the five cases (80 per cent), cultures were positive for Ureaplasma urealyticum in pure culture from either placenta, fetal lung, or both tissues. The remaining case (20 per cent) was negative for aerobes, anaerobes, and mycoplasmas. The study demonstrates a significant association and supports a causal relationship between isolation of Ureaplasma from mid-trimester amniotic fluid with fetal wastage and premature birth. 相似文献
24.
Jeffrey I. Zink 《Die Naturwissenschaften》1981,68(10):507-512
Triboluminescence is the light emitted when mechanical energy is applied to a crystal. Many common substances such as sugar and copper sulfate are triboluminescent. The origin of the light and the mechanical, chemical, and crystallographic requirements of the phenomenon are described in this paper. 相似文献
25.
Scott Murtishaw Jayant Sathaye Christina Galitsky Kristel Dorion 《Mitigation and Adaptation Strategies for Global Change》2006,11(3):645-665
The Lawrence Berkeley National Laboratory (Berkeley Lab) and the Center for Sustainable Development in the Americas (CSDA)
conducted technical studies and organized two training workshops to develop capacity in Central America for the evaluation
of climate change projects. This paper describes the results of two baseline case studies conducted for these workshops, one
for the power sector and one for the cement industry, that were devised to illustrate certain approaches to baseline setting.
Multiproject baseline emission rates (BERs) for the main Guatemalan electricity grid were calculated from 2001 data. In recent
years, the Guatemalan power sector has experienced rapid growth; thus, a sufficient number of new plants have been built to
estimate viable BERs. We found that BERs for baseload plants offsetting additional baseload capacity ranged from 0.702 kgCO2/kWh
(using a weighted average stringency) to 0.507 kgCO2/kWh (using a 10th percentile stringency), while the baseline for plants
offsetting load-following capacity is lower at 0.567 kgCO2/kWh. For power displaced from existing load-following plants, the
rate is higher, 0.735 kgCO2/kWh, as a result of the age of some plants used for meeting peak loads and the infrequency of
their use. The approved consolidated methodology for the Clean Development Mechanism yields a single rate of 0.753 kgCO2/kWh.
Due to the relatively small number of cement plants in the region and the regional nature of the cement market, all of Central
America was chosen as the geographic boundary for setting cement industry BERs. Unfortunately, actual operations and output
data were unobtainable for most of the plants in the region, and many data were estimated. Cement industry BERs ranged from
205 kgCO2 to 225 kgCO2 per metric ton of cement. 相似文献
26.
Summary This study investigated whether reduced male aid in defending offspring potentially reduces the fitness of females choosing already-mated males in the house wren (Troglodytes aedon), a small, territorial songbird. Frozen snakes were placed at 23 nests of monogamously mated males and 12 secondary nests of bigamously mated males. All presentations were made during incubation stages of females attending focal nests. Snakes were placed at nests of secondary females when nests of their primary counterparts contained young 5–9 days old. Males are most attentive to primary nests during this period and should therefore be relatively inattentive to secondary mates and nests. Nevertheless, an equal proportion of monogamous and bigamous males discovered snakes within 15 min, and mean time to discovery, when discovery occurred, did not differ with nest status. Monogamous and bigamous males were also equally likely to attack snakes physically once discovered. Monogamous males appeared no more likely to discover snakes than bigamous males for two main reasons. First, although monogamous males were near focal nests (i.e., < 10 m) more often than bigamous males, monogamous males tended to stay out of view of nests for long periods. In contrast, bigamous males always went immediately to focal nests upon arriving in their vicinity. Second, about one-third of monogamous males in this study spent much of their time during trials at the far edges of their territories advertising for secondary mates. Our experiment suggests that reduced male aid in defending nests against small, diurnal predators probably does not contribute to the cost of polygyny in house wrens.
Correspondence to: L.S. Johnson 相似文献
27.
28.
Marty D. Matlock Kevin Ray Kasprzak G. Scott Osborn 《Journal of the American Water Resources Association》2003,39(2):267-275
ABSTRACT: The lower reaches of the Arroyo Colorado have historically failed to meet their use under subsection 303(b) of the U.S. Clean Water Act due to fecal coliform bacteria and low dissolved oxygen (DO). Fish kills, especially at the tidal confluence at the Port of Harlingen, Texas, have been reported. Oxygen demand from sediment (SOD) for a river typically has two states‐diffusion limited SOD (SOD) and potential SOD (pSOD), expressed when sediment is resuspended through increased flow or other disturbances. The objective of this research was to measure SOD in the Arroyo Colorado River in situ, estimate pSOD ex situ, and evaluate the relationship between SOD and the depositional environment. We measured SOD and pSOD in the Arroyo Colorado River at up to eight sites over three sampling events. We identified the sample sites based on a modified Rosgen geomorphic index for streambed stabilization. Sites with high sediment deposition potential had high SOD. The average values of SOD between sites were 0.62 g/m2/day (standard deviation 0.38 g/m2/day) and ranged from 0.13 to 1.2 g/m2/day. Potential SOD values ranged from as low as 19.2 to as high as 2,779 g/m3 sediment/ day. Potential SOD can serve as an indicator of the possible impact of SOD from resuspended sediment in stream systems. 相似文献
29.
L. Jeffrey Lefkoff Donald R. Kendall 《Journal of the American Water Resources Association》1996,32(3):451-463
ABSTRACT: A non-linear optimization model is applied to the California State Water Project (SWP) and portions of the Central Valley Project (CVP). The model accounts for the major hydrologic, regulatory, and operational features of both projects. The model maximizes long-term SWP yields over a 70-year period, using a quarterly time step. The potential for increased yield associated with a proposed facility improvement is evaluated with the model. The proposed facility is an extension of the Folsom-South Canal, which would allow water to be conveyed from the American River below Folsom Reservoir into New Melones Reservoir on the Stanislaus River or into the California Aqueduct. Model results indicate that extension of the Folsom-South Canal has the potential to increase SWP yields by 13 percent. 相似文献
30.
Jeffrey H. Kahn Kimberly T. Schneider Theresa M. Jenkins‐Henkelman Laura L. Moyle 《组织行为杂志》2006,27(6):793-807
The authors investigated whether the relationship between the contents of emotional social support and job burnout among high‐school teachers is spurious because of the role of dispositional positive and negative affectivity. A national sample of 339 teachers was surveyed via a web‐based procedure. Hierarchical regression analyses did not support spuriousness; emotional social support was uniquely predictive of three dimensions of burnout controlling for affectivity. As positive emotional social support increased, emotional exhaustion and cynicism decreased, and professional efficacy increased. As negative emotional social support increased, emotional exhaustion and cynicism also increased. Commonality analyses based on the present data and data reported by K. L. Zellars and P. L. Perrewé (2001; Journal of Applied Psychology, 86, 459–467) provided additional support for the unique role of emotional social support on burnout, but these analyses suggest a greater role of affectivity than emotional social support. These findings have implications for research on burnout as well as the prevention of burnout among teachers. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献