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排序方式: 共有313条查询结果,搜索用时 15 毫秒
241.
242.
Evaluating Genetic Diversity Associated with Propagation-Assisted Restoration of American Shad 总被引:3,自引:0,他引:3
B. L. Brown § T. P. Gunter † J. M. Waters ‡ and J. M. Epifanio 《Conservation biology》2000,14(1):294-303
Abstract: We investigated the conservation of genetic diversity during a restoration program for American shad ( Alosa sapidissima ) in Virginia ( U.S.A.). Restoration entailed capture of wild Pamunkey River shad broodstock followed by production and release of hatchery-reared fry to supplement the nearly extinct James River shad population. To assess the baseline genetic diversity of donor and recipient populations, we used five tri- and tetra-nucleotide microsatellite loci to test for genetic heterogeneity among yearly subsamples from both rivers and between early- and late-spawning shad from the donor population. Tests for allelic heterogeneity between James River and Pamunkey shad subsamples yielded no significant genetic differentiation (χ 2 = 14.72, p = 0.132 and χ 2 = 10.24, p = 0.440, respectively). We detected no significant genetic divergence between early- and late-spawning adults in Pamunkey River spawning aggregations in either year. The donor and recipient populations exhibited significant genetic differentiation (χ 2 = 27.4, p = 0.003), however, indicating that the stocking program carries a risk of outbreeding depression. Because the two river populations are genetically divergent, replenishment of the James population with Pamunkey fry may be detectable in the future as heterozygote deficits and linkage disequilibria in the James River population. In an analysis of broodstock and their hatchery-reared progeny, microsatellites proved efficient for family analysis, unambiguously determining the parentage of 100% of the hatchery-reared fry studied. Genetic analysis indicated that breeding procedures may result in high levels of reproductive variance. 相似文献
243.
Klaus Jung Karin Kaletta Helmut Segner Gerrit Schüürmann 《Environmental science and pollution research international》1999,6(2):72-76
A stable isotope15N-nitrogen test (ESIMA = Ecotoxicological Stable Isotope Metabolic Assay) was developed to assess biological effects and the
potential toxicological hazard of chemicals and contaminated environmental samples on plant metabolism. The assay measures
the effect of toxicants on the incorporation of a15N labelled tracer into the total nitrogen fraction (both the nonprotein and protein fraction) of plants. Segments ofPisum arvense epicotyls are used as test substrates because of their high metabolic activity. The plant material is incubated under standardised
conditions for two hours; subsequently15N incorporation is analysed by determining the15N abundance (15N atom-%) in the epicotyl segments.
The effects of toxicants are evaluated by comparing the15N incorporation rates of control tissue and epicotyl segments exposed to individual chemicals or complex environmental samples.
The specificity and sensitivity of effects as indicated by ESIMA were compared with effects as measured by two established
ecotoxicological bioassays, the pollen tube growth test using pollen ofNicotiana sylvestris and the bacterial luminescence inhibition test using pollen ofPhotobacterium phosphoreum. The results of the study clearly indicate the suitability of ESIMA for assessing toxic impacts on plant nitrogen metabolism.
Prof. Dr. habil. Hans Faust dedicated to his 70th birthday. 相似文献
244.
Manfred Ayasse Wolf Engels Gunter Lübke Timo Taghizadeh Wittko Francke 《Behavioral ecology and sociobiology》1999,45(2):95-106
The present paper reports on behavioral experiments and gas chromatographic analysis of chemical communication in the mating
biology of the primitively eusocial sweat bee Lasioglossum (Evylaeus) malachurum. In a dual-choice experiment, a female made odorless was significantly less attractive than an untreated one. Attraction in
L. (Evylaeus) malachurum is therefore mediated by a female-produced sex pheromone. Further bioassays showed that unmated gynes are more attractive
to males than mated ones. Males are able to differentiate between the two groups of females as little as 3 h after mating.
Biotests with different samples obtained from attractive gynes showed surface extracts to be most attractive. Behavioral tests
with synthetic copies of the compounds identified as cuticular constituents of virgin gynes were highly attractive to males;
the volatile bouquets consisting of n-alkanes, n-alkenes and iso- pentenyl esters of unsaturated fatty acids were the most
attractive samples. Isopentenyl esters of unsaturated fatty acids were the key compounds in inducing male inspections as well
as stimulating pounces and copulatory attempts. Virgin and nesting gynes differed clearly in the relative and absolute amounts
of the volatiles on the cuticle. The total amount of volatiles was significantly higher in virgin gynes and decreased in breeding
queens. Hydrocarbons were the dominant group of compounds in both groups of females. The relative amounts of the wax-type
ester, hexadecyl oleate, iso- pentenyl esters, and a hitherto unidentified steroid were higher in attractive virgin gynes,
while the relative proportions of hydrocarbons and lactones dominated in nesting queens. The site of sex pheromone production
in attractive young L. (Evylaeus) malachurum gynes remains unknown. Head glands or Dufour's gland secretions may be involved. Another possible source of the `active principle'
found among the cuticular lipids could be glandular cells of the epidermis. The significance of modulation of female sex pheromone
composition is discussed in terms of a reduction in mating expenditures.
Received: 30 April 1998 / Accepted after revision: 24 July 1998 相似文献
245.
246.
Evaluation of the dioxin removal efficiency of the air pollution control device (APCD) at an existing municipal waste incinerator (MWI) located in Taiwan is conducted via stack sampling and analysis. The MWI investigated is equipped with cyclones, dry lime scrubbing systems and fabric filters as APCDs. Results indicate that the patterns of dioxin isomers at APCDs' inlet and stack are similar. During the first year of carbon injection, the concentrations of emitted dioxin decreased greatly. The dioxin removal efficiency increased from 26.9% to 96.6% after injecting 115 kg/day activated carbon (AC). At the second year, the dioxin removal efficiency reaches 98.7% after injecting the same rate of AC continuously. The lower efficiency achieved with activated carbon injection (ACI) during the first year can be attributed to the memory effect, i.e. the dioxin or precursor desorbs slowly to the flue gas and increases the dioxin concentration at stack, resulting in a lower dioxin removal efficiency than expected. 相似文献
247.
Jung Wan Lee 《国际发展与全球生态学杂志》2019,26(5):398-405
The study aims to examine lagged causal effect of economic development policies on the carbon footprint of Southeast Asia. This study employs unit root test, cointegration test and panel data analysis methods to examine endogeneity concerns in observational data. The study applies panel data analysis methods to address unobserved country effect in the model. The balanced panel data includes a total of 240 observations with five cross sections of five nations in Southeast Asia and with 48 time-specific periods of 1970–2017. The results indicate that (1) exports, industrialization, urbanization and economic growth have lagged negative effect on the carbon footprint of the region in the short-run, and (2) there exists a long-run equilibrium relationship among exports, industrialization, urbanization, economic growth and carbon footprint in the region. The findings suggest that the economic growth, exports, industrialization and urbanization of the developing countries in Southeast Asia have been achieved at the cost of increasing the carbon footprint of the region. The findings imply that the environmental policy of the export-led growth countries never have been effective so far since the nations have achieved their economic growth at the high cost of harming the environment of the nations. 相似文献
248.
Chavidi Venkata Prasad Bala Yerri Swamy Chanda Lakshmi Narayana Reddy Kokkarachedu Vara Prasad Posa Sudhakara MCS Subha Song Jung Il Kashay Chowdoji Rao 《Journal of Polymers and the Environment》2012,20(2):344-352
Novel type of highly swollen beads were prepared by grafting 2-hydroxyethylacrylate onto biodegradable Sodium alginate (SA) via free-radical polymerization using potassium persulphate as an initiator and Triprolidine hydrochloride as a model drug. Evidence of grafting was obtained by fourier transform infrared spectroscopic technique. Morphological properties of the beads were studied by SEM analysis. Thermal properties and crystallinity of the beads were characterized using differential scanning calorimetry and thermogravimetric analysis and X-ray diffraction techniques, respectively. Dissolution experiments were performed to study the release profiles at 37?°C in phosphate buffer solution (pH-7.4). Effect of monomer content, crosslinking agent and drug/polymer ratio on swelling properties and release profiles were also comparatively studied. A dissolution result concludes that drug release decreases with increasing crosslinker content. The highest release (96%) was obtained for the beads prepared with 0.5?mL crosslinking agent. Equilibrium swelling degree also supports the drug release profiles confirming SA-g-HEA beads showed better release profiles compare to plain SA beads. 相似文献
249.
Ji-Eun Jung Simona Liguori Adam D. Jew Gordon E. Brown Jr. 《Journal of the Air & Waste Management Association (1995)》2018,68(1):39-53
One of the biggest environmental concerns caused by coal-fired power plants is the emission of mercury (Hg), which is toxic metal. To control the emission of Hg from coal-derived flue gas, it is important to understand the behavior and speciation of Hg as well as the interaction between Hg and solid materials in the flue gas stream. In this study, atomic-scale theoretical investigations using density functional theory (DFT) were carried out in conjunction with laboratory-scale experimental studies to investigate the adsorption behavior of Hg on hematite (α-Fe2O3). According to the DFT simulation, the adsorption energy calculation proposes that Hg physisorbs to the α-Fe2O3(0001) surface with an adsorption energy of ?0.278 eV, and the subsequent Bader charge analysis confirms that Hg is slightly oxidized. In addition, Cl introduced to the Hg-adsorbed surface strengthens the Hg stability on the α-Fe2O3(0001) surface, as evidenced by a shortened Hg-surface equilibrium distance. The projected density of states (PDOS) analysis also suggests that Cl enhances the chemical bonding between the surface and the adsorbate, thereby increasing the adsorption strength. In summary, α-Fe2O3 has the ability to adsorb and oxidize Hg, and this reactivity is enhanced in the presence of Cl. For the laboratory-scale experiments, three types of α-Fe2O3 nanoparticles were prepared using the precursors Fe(NO3)3, Fe(ClO4)3, and FeCl3, respectively. The particle shapes varied from diamond to irregular stepped and subrounded, and particle size ranged from 20 to 500 nm depending on the precursor used. The nanoparticles had the highest surface area (84.5 m2/g) due to their highly stepped surface morphology. Packed-bed reactor Hg exposure experiments resulted in this nanoparticles adsorbing more than 300 μg Hg/g. The Hg LIII-edge extended X-ray absorption fine structure spectroscopy also indicated that HgCl2 physisorbed onto the α-Fe2O3 nanoparticles.Implications: Atomic-scale theoretical simulations proposes that Hg physisorbs to the α-Fe2O3(0001) surface with an adsorption energy of ?0.278 eV, and the subsequent Bader charge analysis confirms that Hg is slightly oxidized. In addition, Cl introduced to the Hg-adsorbed surface strengthens the Hg stability on the α-Fe2O3(0001) surface, as evidenced by a shortened Hg-surface equilibrium distance. The PDOS analysis also suggests that Cl enhances the chemical bonding between the surface and the adsorbate, thereby increasing the adsorption strength. Following laboratory-scale experiment of Hg sorption also shows that HgCl2 physisorbs onto α-Fe2O3 nanoparticles which have highly stepped structure. 相似文献