Effects of persistent organic pollutants on the thyroid function of the European sea bass (Dicentrarchus labrax) from the Aegean sea, is it an endocrine disruption?     

Schnitzler JG  Koutrakis E  Siebert U  Thomé JP  Das K 《Marine pollution bulletin》2008,56(10):1755-1764

We evaluated the alterations of organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) on the thyroid in wild and cultured sea bass (Dicentrarchus labrax) at environmental concentrations. These compounds influence the endocrine system of many fish species and are qualified as endocrine disruptors. The thyroid seems to be a target organ. Two alteration endpoints: the thyroid histology and the muscular thyroid hormone concentrations, were used simultaneously.High concentrations in PCBs and DDT were detected in muscles, supporting the idea that the Mediterranean fauna could be more polluted than the Atlantic fauna. The high abundance of DDE indicates a progressive degradation of remnant DDT load and the absence of new inputs in this area. Aquaculture sea bass shows a significant higher amount of pollutants on fresh weight basis (especially PCBs) in their muscles compared to the wild sea bass. Those differences may be related mainly to the contaminations of diet.Thyroid parameters vary between wild and aquaculture sea bass, wild sea bass were characterized by higher follicle diameters, epithelial cell heights and muscular T₄ concentrations. A significant relationship between persistent organic pollutants (muscular PCBs and DDT concentration) and the different thyroid parameters (diameters of follicles, epithelial cell heights and muscular T₄ levels) could be observed, which support the hypothesis that these compounds have an adverse impact on thyroid morphometry and function.  相似文献   

The Meteoritical Society and Meteoritics and Planetary Science: Past and future     

Ursula B. Marvin 《Meteoritics & planetary science》2000,35(1):4-4

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Assessing the Transport of Pharmaceutical Compounds in a Layered Aquifer Discharging to a Stream     

Nicola Balbarini  Majken Frederiksen  Vinni Rønde  Ingelise Møller  Anne T. Sonne  Ursula S. McKnight  Jørn K. Pedersen  Philip J. Binning  Poul L. Bjerg 《Ground water》2020,58(2):208-223

A groundwater plume containing high concentrations of pharmaceutical compounds, mainly sulfonamides, barbiturates, and ethyl urethane, in addition to chlorinated ethenes and benzene was investigated. The contamination originating from a former pharmaceutical industry discharges into a multilayered aquifer system and a downgradient stream. In this study, geological and hydrogeological data were integrated into a numerical flow model to examine identified trends using statistical approaches, including principal component analysis and hierarchal cluster analysis. A joint interpretation of the groundwater flow paths and contaminant concentrations in the different compartments (i.e., groundwater and hyporheic zone) provided insight on the transport processes of the different contaminant plumes to the stream. The analysis of historical groundwater concentrations of pharmaceutical compounds at the site suggested these compounds are slowly degrading. The pharmaceutical compounds migrate in both a deep semiconfined aquifer, as well as in the shallow unconfined aquifer, and enter the stream along a 2-km stretch. This contrasted with the chlorinated ethenes, which mainly discharge to the stream as a focused plume from the unconfined aquifer. The integrated approach developed here, combining groundwater flow modeling and statistical analyses of the contaminant concentration data collected in groundwater and the hyporheic zone, lead to an improved understanding of the observed distribution of contaminants in the unconfined and semiconfined aquifers, and thus to their discharge to the stream. This approach is particularly relevant for large and long-lasting contaminant sources and plumes, such as abandoned landfills and industrial production sites, where field investigations may be very expensive.  相似文献   

Paleoecology of mangroves along the Sibun River, Belize     

Natalie M. Monacci  Ursula Meier-Grünhagen  Bruce P. Finney  Hermann Behling  Matthew J. Wooller 《Quaternary Research》2011,76(2):220-228

This study examines a sediment core (SR-63) from a mangrove ecosystem along the Sibun River in Belize, which is subject to both changes in sea-level and in the characteristics of the river's drainage basin. Radiocarbon dates from the core show a decreased sedimentation rate from ~ 6 ka to 1 cal ka BP and a marked change in lithology from primarily mangrove peat to fluvial-derived material at ~ 2.5 cal ka BP. Changes in the sedimentation rates observed in mangrove ecosystems offshore have previously been attributed to changes in relative sea-level and the rate of sea-level rise. Pollen analyses show a decreased abundance of Rhizophora (red mangrove) pollen and an increased abundance of Avicennia (black mangrove) pollen and non-mangrove pollen coeval with the decreased sedimentation rates. Elemental ratios ([N:C]_a) and stable isotope analyses (δ¹⁵N and δ¹³C) show that changes in the composition of the organic material are also coeval with the change in lithology. The decrease in sedimentation rate at the site of core SR-63 and at offshore sites supports the idea that regional changes in hydrology occurred during the Holocene in Belize, influencing both mainland and offshore mangrove ecosystems.  相似文献   

Tunnel stability analysis during construction using a neuro‐fuzzy system     

Jos Luis Rangel  Ursula Iturrarn‐Viveros  A. Gustavo Ayala  Francisco Cervantes 《国际地质力学数值与分析法杂志》2005,29(15):1433-1456

This paper presents an alternative strategy to evaluate the stability of tunnels during the design and construction stages based on a hybrid system, composed by neural, neuro‐fuzzy and analytical solutions. A prototype of this system is designed using a database formed by 261 cases, 45 real and the rest synthetic. This system is capable of reproducing the displacements induced at the periphery of the tunnel before and after support installation. The stability of the excavation process is evaluated using a criterion that considers dimensionless parameters based on the shear strength of the media, the induced deformation level in the ground, the plastic radii and the advance of excavation without support. The efficiency and validity of the prototype is verified with two examples of actual tunnels, one included in the database used to train the system and the other not included. The results of both examples show a better approximation than other commonly used techniques. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

软性海洋沉积物中水含量对XRF测试的影响     

Rik Tjallingii  Ursula R 《海洋地质前沿》2008,24(3):24-26

Avaatech型X荧光扫描仪是由计算机控制的柱状样扫描装置，可以从剖开样品表面直接获得沉积物的化学组成，无需破坏样品的整体性。能够实现几乎连续的测试，快速地得到从Al到u的所有元素的相对含量。XRF扫描仪已经成功地应用于高分辨率、不同时间序列和时间尺度的地层对比以及沉积相和古气候重建。  相似文献   

Domenico Troili (1766): “The true cause of the fall of a stone in Albereto is a subterranean explosion that hurled the stone skyward”     

Ursula B. Marvin  Mario L. Cosmo 《Meteoritics & planetary science》2002,37(12):1857-1864

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AN UNPUBLISHED MEMOIR ON METEORITES BY LYMAN SPALDING, 1810     

Ursula B. Marvin 《Meteoritics & planetary science》1979,14(2):197-205

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Basalts from Mare Crisium     

Graham Ryder  Harry Y. Mcsween Jr.  Ursula B. Marvin 《Earth, Moon, and Planets》1977,17(3):263-287

The stratified core sample returned from Mare Crisium by the Luna 24 unmanned space probe is composed primarily of a new variety of subophitic to ophitic basalt with very low contents of TiO₂ and MgO. This consists of clinopyroxene, calcic plagioclase, olivine, and minor amounts of silica, chromite, ulvöspinel, ilmenite, troilite, apatite, and Fe-metal. Granular metabasalts have the same bulk composition, but mineral phases exhibit less compositional variation. Fine-grained impact melts have similar compositions and are apparently derived from these basalts. We conclude that the basalts, which are chemically distinct from the very-low-titanium basalts found elsewhere on the Moon, represent the local surface flows of Mare Crisium.Sparse fragments of an olivine vitrophyre that is low in TiO₂ but high in MgO and approaches the composition of the Apollo 15 green glasses may be derived from patches of dark mantling materials 20 km from the landing site.Now at Department of Geology, University of California at Davis, Davis, Calif., U.S.A.Now at Department of Geological Sciences, The University of Tennessee, Knoxville, Tenn., U.S.A.  相似文献   

Scattering and diffraction of SH waves by a finite crack: an analytical solution   总被引：1，自引：0，他引：1  

Francisco J. Sánchez&#;Sesma  Ursula Iturrarán&#;Viveros 《Geophysical Journal International》2001,145(3):749-758

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