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101.
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A case of in utero closure of the ductus arteriosus was detected by Doppler echocardio-graphy at 31 weeks of gestation. It presented as a non-hydropic distressed fetus with ultrasound detection of tricuspid regurgitation. Pulsed Doppler ultrasound showed markedly decreased blood flow through the tricuspid and pulmonary valves and absent blood flow at the ductus arteriosus. These, as well as the resultant increased right-to-left shunting across the foramen ovale, were reaffirmed by colour flow mapping. 相似文献
104.
The Use of Low-Level Jets by Migrating Birds 总被引:1,自引:0,他引:1
Birds flying at high altitudes have occasionally been observed above mountain areas and the open sea. For the first time
the regular occurrence of migrating birds flying within a low-level jet at heights of 5000 to almost 9000 m asl. have now
been verified by radar above the Negev desert in southern Israel. Tracks of rather large birds with wing-beat frequencies
of 5–6 Hz were measured to have horizontal flight speeds up to 50 m/s. Visual observations, seasonal occurrence, and wing-beat
frequencies allowed to associate them with small species of the order Ciconiiformes (mainly Ardeidae) and possibly with members
of the Laro-Limicolae group. These wading birds seem prone to continuing nocturnal migration into daytime under favorable
conditions and to make use of high wind speeds at sometimes extreme altitudes.
Received: 21 June 1999 / Accepted in revised form: 26 August 1999 相似文献
105.
Fourteen (2.5 per cent) of 568 chromosome preparations after CVS showed discrepancies between the placental and fetal karyotype, mainly due to placental mosaicism. The presence of a second cell line within the placenta was confirmed in all but one case, in which cytogenetic reinvestigations were carried out. Our clinical data indicate that severe developmental retardation in the newborn is not to be expected if only the placenta carries the chromosomally abnormal cell line. 相似文献
106.
107.
The gas phase atmospheric degradation of diazinon has been investigated at the large outdoor European Photoreactor (EUPHORE) in Valencia, Spain. The rate constant for reaction of diazinon with OH radicals was measured using a conventional relative rate method with di-n-buthylether as reference compound being k = (3.5 ± 1.2) × 10−11 cm3 molecule−1 s−1 at 302 ± 10 K and atmospheric pressure. The available evidence indicates that tropospheric degradation of diazinon is mainly controlled by reaction with OH radicals, and that the tropospheric lifetime with respect to the OH reaction is estimated to be around 4 h whereas its lifetime with respect to the photolysis is higher than 1 d under our conditions. Significant aerosol formation was observed following the reaction of diazinon with OH radicals, and the main carbon-containing products detected in the particle phase were hydroxydiazinon, hydroxydiazoxon and 2-isopropyl-6-methyl-pyrimidinyl-4-ol. 相似文献
108.
Petersen IL Tomasi G Sørensen H Boll ES Hansen HC Christensen JH 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):3071-3077
Metabolic profiling in plants can be used to differentiate between treatments and to search for biomarkers for exposure. A methodology for processing Ultra-High-Performance Liquid Chromatography-Diode-Array-Detection data is devised. This methodology includes a scheme for selecting informative wavelengths, baseline removal, retention time alignment, selection of relevant retention times, and principal component analysis (PCA). Plant crude extracts from rapeseed seedling exposed to sublethal concentrations of glyphosate are used as a study case. Through this approach, plants exposed to concentrations down to 5 μM could be distinguished from the controls. The compounds responsible for this differentiation were partially identified and were different from those specific for high exposure samples, which suggests that two different responses to glyphosate are elicited in rapeseed depending on the level of exposure. The PCA loadings indicate that a combination of other metabolites could be more sensitive than the response of shikimate to detect glyphosate exposure. 相似文献
109.
Caliz J Vila X Martí E Sierra J Nordgren J Lindgren PE Bañeras L Montserrat G 《Chemosphere》2011,83(2):104-116
To highlight the effects of a variety of chlorophenols (CP) in relation to the response of an indigenous bacterial community, an agricultural Mediterranean calcareous soil has been studied in microcosms incubated under controlled laboratory conditions. Soil samples were artificially polluted with 2-monochlorophenol (MCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP), at concentrations ranging from 0.1 up to 5000 mg kg−1. Both activity and composition of the microbial community were assessed during several weeks, respectively, by respirometric methods and PCR-DGGE analysis of extracted DNA and RNA. Significant decreases in soil respirometric values and changes in the bacterial community composition were observed at concentrations above 1000 mg kg−1 MCP and TCP, and above 100 mg kg−1 PCP. However, the persistence of several active bacterial populations in soil microcosms contaminated with high concentration of CP, as indicated by DGGE fingerprints, suggested the capacity of these native bacteria to survive in the presence of the pollutants, even without a previous adaptation or contact with them.The isolation of potential CP degraders was attempted by culture plating from microcosms incubated with high CP concentrations. Twenty-three different isolates were screened for their resistance to TCP and PCP. The most resistant isolates were identified as Kocuria palustris, Lysobacter gummosus, Bacillus sp. and Pseudomonas putida, according to 16S rRNA gene homology. In addition, these four isolates also showed the capacity to reduce the concentration of TCP and PCP from 15% to 30% after 5 d of incubation in laboratory assays (initial pollutant concentration of 50 mg L−1). Isolate ITP29, which could be a novel species of Bacillus, has been revealed as the first known member in this bacterial group with potential for CP bioremediation applications, usually wide-spread in the soil natural communities, which has not been reported to date as a CP degrader. 相似文献
110.
Esther Richards Reza Rizvi Andrew Chow Hani Naguib 《Journal of Polymers and the Environment》2008,16(4):258-266
One key strategy for increasing the application potential for biodegradable plastics lies in improving the physical and mechanical
characteristics, which can be attained by inducing a cellular morphology in the pure polymer with the aid of a blowing agent,
as well as by blending two or more polymers with the desirable properties. This paper examines the effect that blending two
biodegradable polymers has on the thermal properties and morphology of the resultant foams blown with carbon dioxide (CO2). Polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV) and blends of both were foamed and characterized in terms
of thermal characteristics, relative density, cell size, and foam morphology. The results indicate that although PLA and PHBV
are immiscible, the presence of small quantities of PHBV (25 wt%) could lead to low density foams with finer, more uniform
cells. Furthermore, the crystallinity of PHBV was found to be unaffected by the presence of PLA in the composite, which supports
the immiscibility of PLA and PHBV. 相似文献