Trace metal-binding proteins in marine molluscs and crustaceans   总被引：1，自引：0，他引：1  

David W. Engel  Marius Brouwer 《Marine environmental research》1984,13(3):177-194

Some marine invertebrates, such as the American oyster, Crassostrea virginica, the blue crab, callinectes sapidus and the American lobster, Homarusamericanus, concentrate trace metals in their tissues. The occurrence of metallothionein, a low molecular weight, sulfur-containing metal-binding protein, has been correlated with elevated levels of trace metals in these organisms. It is our hypothesis that, whilst metallothioneins are involved in the sequestration of elevated levels of trace metals, they primarily function in regulating normal metal metabolism. In this paper we describe recent field and laboratory experiments designed to examine how oysters, blue crabs and lobsters manage accumulated cadmium, copper and zinc. The possible rôles of metallothionein, as well as the tissue distribution of metals, are emphasized. Metallothioneins were found in all animals we examined; concentrations of metallothioneins and the the amount of bound trace metals are related to time of exposure. We have also demonstrated that the laboratory developed metallothionein models for blue crabs and lobsters may be useful in predicting the partitioning of trace metals in animals living in environments polluted with trace metals.  相似文献   

Cadmium accumulation by the blue crab, callinectes sapidus: Involvement of hemocyanin and characterization of cadmium-binding proteins     

Marius Brouwer  Thea Brouwer-Hoexum  David W. Engel 《Marine environmental research》1984,14(1-4)

The accumulation of cadmium from seawater by the blue crab, Callinectes sapidus, was studied as a function of metal concentration and exposure time, with special emphasis on cadmium-binding proteins. Cadmium was found, in decreasing order of magnitude, in gills, digestive gland and hemolymph. When exposed to 0·5 ppm cadmium for 2–24h, virtually all of the cadmium in the cytosolic fraction of the gill was associated with a low molecular weight (LMW) cadmium-binding protein (MW 8000). However, after 48h of exposure only 50% of the cadmium in the cytosol was bound to this protein. The rest wasfound to be associated with proteins of a molecular weight of 300 000 and 60 000. This pattern of cadmium distribution did not change over a 12-day depuration period. Similar results were obtained upon exposure to 0·1 ppm cadmium. The pattern of cadmium accumulation in the cytosolic fraction of the digestive gland was in marked contrast to that observed for the gill. Initially, the cadmium was distributed over three low molecular weight fractions. During depuration the distribution of cadmium changed and all of the metal became bound to a low molecular weight protein (MW 9000). The cadmium concentrations in the gill and digestive gland remained essentially constant during depuration (12 days). The LMW cadmium-binding proteins were purified by a combination of gelpermeation and ion-exchange chromatography. Their molecular weight, spectral properties and amino acid composition are characteristic of the vertebrate metallothioneins. During exposure to cadmium the metal rapidly appeared in the hemolymph, mainly associated with hemocyanin. During depuration cadmium was transferred from the hemolymph to the digestive gland, demonstrating that hemocyanin acts as a carrier in trace metal transport.  相似文献   

Quantitative 3D imaging of partially saturated granular materials under uniaxial compression     

Milatz  Marius  Hüsener  Nicole  Andò  Edward  Viggiani  Gioacchino  Grabe  Jürgen 《Acta Geotechnica》2021,16(11):3573-3600

Acta Geotechnica - Gauging the mechanical effect of partial saturation in granular materials is experimentally challenging due to the very low suctions resulting from large pores. To this end, a...  相似文献   

Planetons: An example of large amplitude solitary waves     

William K. Dewar 《地球物理与天体物理流体动力学》2013,107(1-4):53-85

Abstract

The term ‘‘solitary wave'’ is usually used to denote a steadily propagating permanent form solution of a nonlinear wave equation, with the permanency arising from a balance between steepening and dispersive tendencies. It is known that large-scale thermal anomalies in the ocean are subject to a steepening mechanism driven by the beta effect, while at the smaller deformation scale, such phenomena are highly dispersive. It is shown here that the evolution of a physical system subject to both effects is governed by the ‘‘frontal semi-geostrophic equation'’ (FSGE), which is valid for large amplitude thermocline disturbances. Solitary wave solutions of the FSGE (here named planetons) are calculated and their properties are described with a view towards examining the behavior of finite amplitude solitary waves. In contrast, most known solitary wave solutions belong to weakly nonlinear wave equations (e.g., the Korteweg—deVries (KdV) equation).

The FSGE is shown to reduce to the KdV equation at small amplitudes. Classical sech² solitons thus represent a limiting class of solutions to the FSGE. The primary new effect on planetons at finite amplitudes is nonlinear dispersion. It is argued that due to this effect the propagation rates of finite amplitude planetons differ significantly from the ‘‘weak planeton'', or KdV, dispersion relation. Planeton structure is found to be simple and reminiscent of KdV solitons. Numerical evidence is presented which suggests that collisions between finite amplitude solitary waves are weakly inelastic, indicating the loss of true soliton behavior of the FSGE at moderate amplitudes. Lastly, the sensitivity of solitary waves to the existence of a nontrivial far field is demonstrated and the role of this analysis in the interpretation of lab experiments and the evolution of the thermocline is discussed.  相似文献   

Numerical studies of two-dimensional saturated/ unsaturated drainage models     

Marius Todsen 《Journal of Hydrology》1973,20(4):311-326

The partial differential equation which governs the seepage of water in unsaturated and saturated porous media is solved numerically by a generalized Newton iteration technique for two models, one ditch drainage model and one earth dam model. For each model, which is two-dimensional, a few hypothetical soils with different moisture retention curves are considered. In both models only drainage from an initially saturated soil occurs; thus, the problem of hysteresis is avoided. The results of the computations are compared with those of corresponding saturated (pure groundwater) models; solutions obtained earlier by this author and others.

Computational instability phenomena appear when the slope of the retention curves is made steep, i.e., for poorly-graded soils.  相似文献   

Spatial variability in specific discharge and streamwater chemistry during low flows: Results from snapshot sampling campaigns in eleven Swiss catchments     

Marius G. Floriancic  Benjamin M. C. Fischer  Peter Molnar  James W. Kirchner  Ilja H.J. van Meerveld 《水文研究》2019,33(22):2847-2866

Catchments consist of distinct landforms that affect the storage and release of subsurface water. Certain landforms may be the main contributors to streamflow during extended dry periods, and these may vary for different catchments in a given region. We present a unique dataset from snapshot field campaigns during low‐flow conditions in 11 catchments across Switzerland to illustrate this. The catchments differed in size (10 to 110 km²), varied from predominantly agricultural lowlands to Alpine areas, and covered a range of physical characteristics. During each snapshot campaign, we jointly measured streamflow and collected water samples for the analysis of major ions and stable water isotopes. For every sampling location (basin), we determined several landscape characteristics from national geo‐datasets, including drainage area, elevation, slope, flowpath length, dominant land use, and geological and geomorphological characteristics, such as the lithology and fraction of quaternary deposits. The results demonstrate very large spatial variability in specific low‐flow discharge and water chemistry: Neighboring sampling locations could differ significantly in their specific discharge, isotopic composition, and ion concentrations, indicating that different sources contribute to streamflow during extended dry periods. However, none of the landscape characteristics that we analysed could explain the spatial variability in specific discharge or streamwater chemistry in multiple catchments. This suggests that local features determine the spatial differences in discharge and water chemistry during low‐flow conditions and that this variability cannot be assessed a priori from available geodata and statistical relations to landscape characteristics. The results furthermore suggest that measurements at the catchment outlet during low‐flow conditions do not reflect the heterogeneity of the different source areas in the catchment that contribute to streamflow.  相似文献   

Subglacial emplacement of tills and meltwater deposits at the base of overdeepened bedrock troughs          下载免费PDF全文

Marius W. Buechi  Stephan M. Frank  Hans Rudolf Graf  John Menzies  Flavio S. Anselmetti 《Sedimentology》2017,64(3):658-685

The sedimentary infills of subglacially eroded bedrock troughs in the Alps are underexplored archives for the timing, extent and character of Pleistocene glaciations but may contain excellent records of the Quaternary landscape evolution over several glacial–interglacial cycles. The onset of sedimentation in these bedrock troughs is often reflected by diamicts and gravels directly overlying bedrock in the deepest basin segments. Subglacial or proglacial depositional environments have been proposed for these coarse‐grained basal units but their characteristics and origin remain controversial. This article presents results from drill cores that recovered a coarse‐grained basal unit in a major buried bedrock‐trough system in the Lower Glatt Valley, northern Switzerland. The excellent core recovery allowed a detailed study combining macroscopic, microscopic and geochemical methods and gives unprecedented insights into the transition from erosion to deposition in overdeepened bedrock troughs. These results show that the basal infill comprises diamicts, interpreted as subglacial tills, separated by thin sorted interbeds, originating from subglacial cavity deposition. The stacking of these units is interpreted to represent repeated switching between a coupled and decoupled ice–bed‐interface indicating an ever‐transforming mosaic of subglacial bed conditions. Decoupling in response to high basal water pressures is probably promoted by the confined subglacial hydraulic conditions resulting from the bedrock acting as aquitards, the narrow reverse sloping outlet and a large catchment area. While stratigraphic and lithological evidence suggests that erosion and the onset of basal sedimentation occurred during the same glaciation, different scenarios for the relative timing of infilling in relation to formation and glaciation of the bedrock trough are discussed. Overlying deltaic and glaciolacustrine sediments suggest deposition during subsequent deglaciation of the bedrock trough. The basal sediment characteristics are in agreement with previous reports in hydrogeological and seismic exploration and suggest the occurrence of similar basal successions in other subglacially overdeepened basins in the Alps and elsewhere.  相似文献   

US tornado fatalities in motor vehicles (1991–2015)     

Marius?J.?PaulikasEmail author  Thomas?W.?Schmidlin 《Natural Hazards》2017,87(1):121-143

Motor vehicles historically have been dangerous locations to shelter in during tornado events. Throughout the twentieth century, motor vehicle design has become safer while tornado forecasting has become better understood. Despite such advances, tornado fatalities in motor vehicles still occur today, and some events periodically result in high numbers of deaths (e.g., ten motor vehicle occupants were killed by a single tornado in Garland, Texas, in 2015). We seek to examine all US tornado-induced motor vehicle fatalities documented between 1991 and 2015. Our findings indicate that motor vehicle fatalities have not significantly changed during this study period. We attribute annual fatality totals to persons lacking awareness of impending dangers coupled with numbers of significant tornado events for a given year. We find most fatalities result when vehicles are lofted or passengers are ejected, and this most typically occurs at the EF3–EF5 intensity thresholds. Fatalities that occur at weaker tornado winds (EF0–EF2) are most often attributed to collapsing debris (mostly trees) on vehicles. Spatially, motor vehicle fatalities are greatest in the Deep South and southern Great Plains regions where overall tornado and nighttime tornado frequencies are greatest. Some of the largest motor vehicle fatality events have resulted from tornadoes not being distinctly visible to motorists; such events have been characterized by tornadoes occurring at night or by tornadoes not appearing as “classic funnels.”  相似文献   

New approach to measure the stability of the solar radiative regime     

Marius Paulescu  Viorel Badescu 《Theoretical and Applied Climatology》2011,103(3-4):459-470

This paper focuses on different ways of characterizing the solar radiative regime of a day and the stability of this regime. The days may be stratified in classes of cloud shade, observed total cloud cover amount, daily averaged clearness index, and fractal dimension of the solar global irradiance signal. A new Boolean parameter related to solar irradiance fluctuation is defined, namely the sunshine stability number. The time averaged value of the sunshine stability number is used for the characterization of the radiative regime stability during a given time interval. Ranking the days from the view-point of the stability of their radiative regime is performed by using the daily average value of the sunshine stability number and appropriately defined values of disorder and complexity, respectively. Measurements performed in the Romanian town of Timisoara (latitude 45°46?? N, longitude 21°25?? E and 85?m altitude above mean sea level) are used here. They refer to time series of global and diffuse solar irradiance recorded at 15-s time interval between sunrise and sunset during all the days in 2009.  相似文献   

Changes in mitochondrial gene and protein expression in grass shrimp, Palaemonetes pugio, exposed to chronic hypoxia     

Brouwer M  Brown-Peterson NJ  Hoexum-Brouwer T  Manning S  Denslow N 《Marine environmental research》2008,66(1):143-145

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