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121.
122.
Chaturvedi P Insana MF 《Computer methods in biomechanics and biomedical engineering》2000,3(2):109-118
The finite-difference time-domain (FDTD) method provides a numerical technique for solving acoustic forward problems. The FDTD is particularly useful in geometries that encompass heterogeneities. Plane-wave modeling permits the simulation of many practical bioacoustic problems because the phase front in the focal zone of many acoustic transducers is nearly planar. The formulation presented in this paper provides a technique for solving half-space problems under local plane-wave illumination. 相似文献
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124.
1. Completion of a large interbasin water transfer system in northern Texas (U.S.A.) provided the opportunity to test the effects of pre-planned, experimental increases (≈×30) in flow on the fish fauna of a small, low-gradient, natural stream that was included as part of the conveyance system. Water from Lake Texoma (Red River basin) was pumped via a 16-km pipeline to the headwaters of Sister Grove Creek (Trinity River basin), which then carried the donor water 50 km downstream to Lake Lavon.
2. Baseline (pre-transfer) data on the composition of fish assemblages at seven stations on the creek or at its confluence with the receiving reservoir were collected monthly for 3 years, and similar data were collected for 2 years during and after trial flows of Lake Texoma water to Sister Grove Creek. We also documented fish abundance at five creek stations immediately before and after three trial flow periods of 10–14 days each in summer and autumn.
3. Multivariate analysis of all routine monthly samples over the 5-year pre- and post-transfer period showed moderate changes in the fish fauna of the creek after initiation of the trial flows. Samples taken within a week before and after the artificial high flows showed little overall change in abundance of individual fish species, but at some stations the quantitative or qualitative change in composition of the local assemblage was substantial.
4. The trial flows lasted 2 weeks or less. Long-term effects of water transfer on the fish fauna of Sister Grove Creek can only be determined after the conveyance system goes into normal operation, with periods of artificial flow of longer duration. 相似文献
2. Baseline (pre-transfer) data on the composition of fish assemblages at seven stations on the creek or at its confluence with the receiving reservoir were collected monthly for 3 years, and similar data were collected for 2 years during and after trial flows of Lake Texoma water to Sister Grove Creek. We also documented fish abundance at five creek stations immediately before and after three trial flow periods of 10–14 days each in summer and autumn.
3. Multivariate analysis of all routine monthly samples over the 5-year pre- and post-transfer period showed moderate changes in the fish fauna of the creek after initiation of the trial flows. Samples taken within a week before and after the artificial high flows showed little overall change in abundance of individual fish species, but at some stations the quantitative or qualitative change in composition of the local assemblage was substantial.
4. The trial flows lasted 2 weeks or less. Long-term effects of water transfer on the fish fauna of Sister Grove Creek can only be determined after the conveyance system goes into normal operation, with periods of artificial flow of longer duration. 相似文献
125.
126.
GABRIELA A. PINTO‐JUMA JOSÉ A. QUARTAU MICHAEL W. BRUFORD 《Zoological Journal of the Linnean Society》2009,155(2):266-288
Cicadas are widely distributed in the Mediterranean area and are mainly distinguished by male acoustic signals, which act as specific mate recognition systems. Within the genus Cicada L. several species have diverged in their calling songs without showing external morphological differences, so acoustic recordings and genetic studies are particularly useful for systematic, biogeography and evolutionary studies. This study assesses sequence variation in closely related species of Cicada from the Mediterranean area, using domain III of the 12S rRNA mitochondrial gene in order to determine the phylogenetic relationships and the evolutionary history of this group, as well as the population structure of the two most common species, C. orni and C. barbara. Five distinct haplogroups were identified, C. orni, C. barbara, C. mordoganensis, C. cretensis and C. lodosi, each corresponding to a distinct evolutionary group. C. barbara was the most divergent species within this group, while C. orni and C. mordoganensis were the most similar. The population structure and demographic parameters of the species were not completely resolved. However, there is evidence for the separation of the C. orni Greek populations from the rest of Europe and also for demographic expansions probably related to Pleistocene climate changes. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 266–288. 相似文献
127.
MICHAEL ANTHONY CARTER JEREMY MILES 《Biological journal of the Linnean Society. Linnean Society of London》1989,36(1-2):129-155
Sexual Actinia equina have been maintained in the laboratory. Monthly biopsies show that these animals have annual gametogenic cycles. Regular samples from several natural populations suggest that animals in the wild show similar gametogenic periodicity. In the laboratory, males release sperm, but females brood young, at least for a few weeks. Members of these broods are released sporadically, usually after a water change. Males and non-sexual adults kept in isolation for over a year release a few juveniles during and at the end of that time. These young are likely to be asexually reproduced. There appears to be geographical variation of anemone size and in the frequency of sexual individuals in populations round the British Coast, so that modes of reproduction may vary. 相似文献
128.
129.
The rate of oxygen consumption increased in maturing Xenopus oocytes within 2 hr after progesterone addition, well before GVBD. This suggested an early requirement for energy metabolism during maturation, similar to the situation in sea urchin eggs during fertilization. Yet, the absence of similar increases in glucose-6-phosphate levels, glucose-6-phosphate dehydrogenase activity, glucose conversion to CO2, and the conversion of NAD(H) to NADP(H), indicated that carbohydrate metabolism was not being stimulated in Xenopus oocytes during maturation. The oxidation of other energy yielding substrates is discussed which might account for the finding that, within 5 min of progesterone addition, both reduced forms of the pyridine nucleotides increased 20% over control levels. This was later followed by a drop in NADH levels and a rise in NAD relative to controls. The significance of these changes in pyridine nucleotide levels and their relationship to a number of maturation events are discussed. 相似文献
130.