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951.
Theoretical signaling models predict that to be honest, begging vocalizations must be costly. To test this hypothesis, oxygen consumption was measured during resting and begging (i.e., vocalizing) activities in pups of the subterranean rodent Ctenomys talarum by means of open-flow respirometry. No statistical differences in individual oxygen consumption between resting and calling pups ranging in age from day 2 to day 20 were found. Given these data, begging calls of C. talarum could not be considered as honest advertisements of offspring need, contrary to what suggested by the behavioral observations of the mother and pups during the nestling period. 相似文献
952.
Cairns Michael A. Winjum Jack K. Phillips Donald L. Kolchugina Tatyana P. Vinson Ted S. 《Mitigation and Adaptation Strategies for Global Change》1997,1(4):363-383
This research assessed land-use impacts on C flux at a national level in four countries: former Soviet Union, United States,
Mexico and Brazil, including biotic processes in terrestrial ecosystems (closed forests, woodlands, and croplands), harvest
of trees for wood and paper products, and direct C emission from fires. The terrestrial ecosystems of the four countries contain
approximately 40% of the world's terrestrial biosphere C pool, with the FSU alone having 27% of the global total. Average
phytomass C densities decreased from south to north while average soil C densities in all three vegetation types generally
increased from south to north. The C flux from land cover conversion was divided into a biotic component and a land-use component.
We estimate that the total net biotic flux (Tg/yr) was positive (= uptake) in the FSU (631) and the U.S. (332), but negative
in Mexico (−37) and Brazil (−16). In contrast, total flux from land use was negative (= emissions) in all four countries (TgC/yr):
FSU −343; U.S. −243; Mexico −35; and Brazil −235. The total net effect of the biotic and land-use factors was a C sink in
the FSU and the U.S. and a C source in both Brazil and Mexico.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
953.
Eric Jauniaux Catherine Donner Christine Thomas Jacques Francotte Frédéric Rodesch Freddy E. Avni 《黑龙江环境通报》1988,8(8):557-563
Prenatal diagnosis of cord defects by means of ultrasound examination is possible and highly accurate. Although this is a rare pathological finding, we report two cases in which umbilical cord pseudocysts were associated with trisomy 18. These observations underscore the need of umbilical blood sampling for establishing the karyotype in fetuses with such umbilical cord anomalies and the importance of careful examination of placentas and infants born with such defects. 相似文献
954.
Dyke GJ Dortangs RW Jagt JW Mulder EW Schulp AS Chiappe LM 《Die Naturwissenschaften》2002,89(9):408-411
Birds known from more than isolated skeletal elements are rare in the fossil record, especially from the European Mesozoic. This paucity has hindered interpretations of avian evolution immediately prior to, and in the aftermath of, the Cretaceous-Tertiary (K-T) extinction event. We report on a specimen of a large ornithurine bird (closely related to Ichthyornis) from the uppermost Cretaceous (Maastricht Formation) of Belgium. This is the first record of a bird from these historic strata and the only phylogenetically informative ornithurine to be recovered from the Mesozoic of Europe. Because this new specimen was collected from 40 m below the K-T boundary (approximate age of 65.8 Ma), it is also the youngest non-neornithine (=non-modern) bird known from anywhere in the world. 相似文献
955.
Lee P. Shulman MD Joe Leigh Simpson Richard E. Felker Donald S. Emerson Carole M. Meyers Owen P. Phillips Sherman Elias 《黑龙江环境通报》1992,12(3):229-234
Transvaginal chorionic villus sampling (CVS) using concurrent transabdominal ultrasound guidance was performed in six women who desired CVS but could not be offered transcervical or transabdominal approaches because of uterine position and placental location. Satisfactory amounts of chorionic villi were obtained in all six cases with no maternal discomfort, an occurrence that contrasts with our experience in transvaginal CVS using endovaginal ultrasound guidance. We believe that transvaginal CVS using concurrent transabdominal ultrasound guidance warrants consideration as an alternative technique for first-trimester CVS in selected patients. 相似文献
956.
Theodore A. Endreny Eric F. Wood 《Journal of the American Water Resources Association》2003,39(1):165-181
ABSTRACT: The Export Coefficient model (ECM) is capable of generating reasonable estimates of annual phosphorous loading simply from a watershed's land cover data and export coefficient values (ECVs). In its current form, the ECM assumes that ECVs are homogeneous within each land cover type, yet basic nutrient runoff and hydrological theory suggests that runoff rates have spatial patterns controlled by loading and filtering along the flow paths from the upslope contributing area and downslope dispersal area. Using a geographic information system (GIS) raster, or pixel, modeling format, these contributing area and dispersal area (CADA) controls were derived from the perspective of each individual watershed pixel to weight the otherwise homogeneous ECVs for phosphorous. Although the CADA‐ECM predicts export coefficient spatial variation for a single land use type, the lumped basin load is unaffected by weighting. After CADA weighting, a map of the new ECVs addressed the three fundamental criteria for targeting critical pollutant loading areas: (1) the presence of the pollutant, (2) the likelihood for runoff to carry the pollutant offsite, and (3) the likelihood that buffers will trap nutrients prior to their runoff into the receiving water body. These spatially distributed maps of the most important pollutant management areas were used within New York's West Branch Delaware River watershed to demonstrate how the CADA‐ECM could be applied in targeting phosphorous critical loading areas. 相似文献
957.
Michael A. Kilgore Paul V. Ellefson Michael J. Phillips 《Water, Air, & Soil Pollution: Focus》2004,4(1):119-130
An important aspect of a best management practices (BMP) program is providing credible information on the extent to which BMPs are being applied within the state. This paper, summarizing the responses of a survey to states about their BMP monitoring program, indicates nearly three of four states in the eastern U.S. have monitoring programs to determine if voluntary or mandatory forest practices are being applied. BMP compliance monitoring programs vary extensively among states in such areas as: the agency(s) responsible for undertaking the monitoring, the types of practices monitored, reasons for establishing the monitoring program, and the frequency and costs of compliance monitoring implementation. The survey found that information from compliance monitoring is used to modify forest practice rules or guidelines, redirect education and training programs, and inform policy makers and the general public of forest practice application rates. Major issues associated with implementing compliance monitoring programs as indicated by the survey include: specifying the types of information to be gathered, selecting harvest sites, accessing private property, determining monitoring responsibility, and reporting and using the information collected. 相似文献
958.
Edward Franzblau Carl J. Popp Eric W. Prestbo Nancy A. Marley Jeffrey S. Gaffney 《Environmental monitoring and assessment》1993,24(3):231-242
Remote measurements of nitrogen dioxide (NO2) were recorded in the brown cloud over Albuquerque, NM, using absorption spectroscopy in the winter of 1987-88 and summer of 1989. The NO2 burdens (optical densities) measured in this manner were found to be in excess of 100 ppm-m. These long pathlength measurements correspond to total concentrations of approximately 5–10 ppb over the integrated observation pathlengths, which ranged from 10–20 km. These concentrations compare well with single location, independent NO
x
analyses. Using two correlation (absorption) spectrometers simultaneously, it was shown that the NO2 distribution is not uniform over the city and can change on the order of minutes in the boundary layer late in the day, demonstrating the advantages of NO2 optical measurements for assessing the location and extent of urban nitrogen dioxide levels in the boundary layer. 相似文献
959.
Host-plant green-leaf volatiles synergize the synthetic sex pheromones of the corn earworm and codling moth (Lepidoptera) 总被引:8,自引:0,他引:8
Douglas M. Light Robert A. Flath Ronald G. Buttery Frank G. Zalom Richard E. Rice Joseph C. Dickens Eric B. Jang 《Chemoecology》1993,4(3-4):145-152
Summary The capture of adult male moths in female sex pheromone traps of two key agricultural pests, the corn earworm (Helicoverpa zea) and the codling moth (Cydia pomonella), is enhanced or synergized by a certain group of host-plant volatiles, the green-leaf volatiles (GLVs). Since female adults of both species call and release their sex pheromones while perched upon the leaves of their host-plants, the volatile constituents from the leaves of a number of host-plants were compared. Sex pheromone traps containing one of the prominent leaf volatiles of certainH. zea hosts, (Z)-3-hexenyl acetate, not only significantly increased the capture ofH. zea males but were preferred over traps baited only with sex pheromone. Similarly, traps baited with synthetic sex pheromome ofC. pomonella plus a blend of GLVs captured significantly more males than traps baited only with sex pheromone. Since male moths are not captured in traps baited only with these GLVs, it appears that these GLVs act as pheromone synergists which increase or enhance the attraction or arrestment of male moths in pheromone traps. 相似文献
960.