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41.
We compared the nesting success of a disturbance-dependent species, the Indigo Bunting ( Passerina cyanea), on different kinds of habitat edges in five sites (225 total nests) in southern Illinois from 1989 to 1993. Nest predation rates along agricultural and abrupt, permanent edges (e.g., wildlife openings, campgrounds) were nearly twice as high as rates along more gradual edges where plant succession was allowed to occur (e.g., treefalls, streamsides, gaps created by selective logging ). Levels of brood parasitism by Brown-headed Cowbirds ( Molothrus ater) varied significantly among sites and years, but not among edge types. Clutch sizes, however, were significantly smaller at agricultural edges where nest predation rates were also high, which suggests either decreased food availability or a population dominated by younger and/or lower-quality ( poor condition) birds. The results of this study illustrate the need to reevaluate management practices (e.g., wildlife openings) that are designed to promote populations of disturbance-dependent wildlife. 相似文献
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Frances Sharples Fred J. Brenner Bruce Piasecki Arthur J. Stewart Helga Van Miegroet 《Environmental management》1990,14(2):279-285
Frances Sharples is a terrestrial ecologist in the Environmental Science Division of the Oak Ridge National Laboratory in
Oak Ridge, Tennessee, operated by Martin Marietta Energy Systems, Inc., under Contract No. DE-AC05-840R21400 with the US Department
of Energy. Publication No. 3413, Environmental Sciences Division, ORNL. 相似文献
45.
Oppenländer T Walddörfer C Burgbacher J Kiermeier M Lachner K Weinschrott H 《Chemosphere》2005,60(3):302-309
Xenon excimer (Xe2*) lamps can be used for the oxidation and mineralization of organic compounds in aqueous solution. This vacuum-ultraviolet (VUV) photochemical method is mainly based on the photochemically initiated homolysis of water that produces hydrogen atoms and hydroxyl radicals. The efficiency of substrate oxidation and mineralization is limited markedly due to the high absorbance of water at the emission maximum of the Xe2* lamp (lambda(max)=172 nm). This photochemical condition generates an extreme heterogeneity between the irradiated volume V(irr) and the non-irradiated ("dark") bulk solution. During VUV-initiated photomineralization of organic substrates, the fast scavenging of hydrogen atoms and of carbon-centered radicals by dissolved molecular oxygen produces a permanent oxygen deficit within V(irr) and adjacent compartments. Hence, at a constant photon flux the concentration of dissolved molecular oxygen within the zones of photo and thermal radical reactions limits the rate of mineralization, i.e. the rate of TOC diminution. Thus, a simple and convenient technique is presented that overcomes this limitation by injection of molecular oxygen (or air) into the irradiated volume by use of a ceramic oxygenator (aerator). The tube oxygenator was centered axially within the xenon excimer flow-through lamp. Consequently, the oxygen or air bubbles enhanced the transfer of dissolved molecular oxygen into the VUV-irradiated volume leading to an increased rate of mineralization of organic model compounds, e.g. 1-heptanol, benzoic acid and potassium hydrogen phthalate. 相似文献
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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
49.
Hernan Mauricio Pérez Katherina B. Brokordt Gloria Martínez Helga Guderley 《Marine Biology》2009,156(8):1585-1593
The energetic cost of spawning and the endogenous factors that modulate spawning could modify escape response performance,
leading to a conflict between the requirements of two fundamental components of fitness: reproduction and survival. We examined
whether spawning changed force production during escape responses by the functionally hermaphroditic scallop, Argopecten purpuratus, and whether the response of smooth (tonic) and striated (phasic) muscles differed. Force production during escape responses
by mature scallops was compared before induction of spawning, during spawning and after completion of spawning. Maximum tonic
force and the area under the force curve (total force recorded) were diminished during gamete release, whereas phasic force
production (maximum and mean force) increased after spawning was completed. The number and frequency of phasic contractions
did not change during the spawning process, suggesting that spawning did not limit fuel availability for phasic contractions.
The decrease in tonic force during spawning and the increased phasic force production after spawning may reflect changes in
monoamine levels during gamete release. Whereas the spawning process modified force production during escape responses, the
changes would, if anything, enhance escape performance during an initial encounter between a scallop and a predatory sea star. 相似文献
50.
Cappiello A Famiglini G Palma P Pierini E Trufelli H Maggi C Manfra L Mannozzi M 《Chemosphere》2007,69(4):554-560
Diethylene glycol (DEG) is extensively used on offshore gas platforms to prevent the hydrate formation during the gas-water separation process and to inhibit corrosion events. This chemical might enter in the marine environment via the produced formation water (PFW) discharge. In this study, a new approach was applied to the investigation of the DEG content in PFW discharges and seawater samples from four gas installation platforms in the Adriatic Sea (Italy). The method includes an off-line solid-phase extraction/pre-concentration technique, followed by a nanoscale flow injection/direct-electron ionization (EI) mass spectrometric analysis. Direct-EI is a novel and miniaturized interface for directly coupling a liquid chromatograph with an electron ionization mass spectrometer. The capability to acquire EI spectra, and to operate in selected ion monitoring mode during actual sample analyses, allowed a precise quantification of DEG with a method limit of detection of 31microg/l. In addition, a careful evaluation of the matrix effect showed that, as opposed to electrospray ionization, the response of the Direct-EI interface was not affected by sample interferences. 相似文献