绿色杜氏藻被膜泡囊的超微结构研究   总被引：3，自引：0，他引：3  

黄晓航  张小庆  吴超元  Alfsen Annette 《海洋与湖沼》1998,29(6):565-569

于１９９０年５月－１９９１年５月,运用透射电镜观察绿色杜氏藻,对该氏藻被膜泡囊的形态结构及其在细胞内的分布和形成过程进行研究。观察表明,绿色杜氏藻细胞的高尔基体和细胞膜有许多大小不等的被膜泡囊;这些被膜泡囊由泡囊及其表面的网状结构构成,其直径在４５－１２０ｎｍ之间;在细胞膜附近的被膜泡囊直径较大;在高尔基体和细胞膜上还观察到被膜泡囊的形成过程。  相似文献   

Tsunami detection by high-frequency radar in British Columbia: performance assessment of the time-correlation algorithm for synthetic and real events     

Charles-Antoine Guérin  Stéphan T. Grilli  Patrick Moran  Annette R. Grilli  Tania L. Insua 《Ocean Dynamics》2018,68(4-5):423-438

The authors recently proposed a new method for detecting tsunamis using high-frequency (HF) radar observations, referred to as “time-correlation algorithm” (TCA; Grilli et al. Pure Appl Geophys 173(12):3895–3934, 2016a, 174(1): 3003–3028, 2017). Unlike standard algorithms that detect surface current patterns, the TCA is based on analyzing space-time correlations of radar signal time series in pairs of radar cells, which does not require inverting radial surface currents. This was done by calculating a contrast function, which quantifies the change in pattern of the mean correlation between pairs of neighboring cells upon tsunami arrival, with respect to a reference correlation computed in the recent past. In earlier work, the TCA was successfully validated based on realistic numerical simulations of both the radar signal and tsunami wave trains. Here, this algorithm is adapted to apply to actual data from a HF radar installed in Tofino, BC, for three test cases: (1) a simulated far-field tsunami generated in the Semidi Subduction Zone in the Aleutian Arc; (2) a simulated near-field tsunami from a submarine mass failure on the continental slope off of Tofino; and (3) an event believed to be a meteotsunami, which occurred on October 14th, 2016, off of the Pacific West Coast and was measured by the radar. In the first two cases, the synthetic tsunami signal is superimposed onto the radar signal by way of a current memory term; in the third case, the tsunami signature is present within the radar data. In light of these test cases, we develop a detection methodology based on the TCA, using a correlation contrast function, and show that in all three cases the algorithm is able to trigger a timely early warning.  相似文献   

Efficient Representation of Laguerre Mosaics with an Application to Microstructure Simulation of Complex Ore     

Menzel  Peter  Teichmann  Jakob  van den Boogaart  Karl Gerald 《Mathematical Geosciences》2020,52(6):731-757

Mathematical Geosciences - Laguerre mosaics have been an important modeling approach in astronomy, physics, crystallography, geology and mathematics for several decades. In materials science, they...  相似文献   

Invertebrate p53-like mRNA isoforms are differentially expressed in mussel haemic neoplasia     

Muttray AF  Schulte PM  Baldwin SA 《Marine environmental research》2008,66(4):412-421

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Velocity interpolation and streamline tracing on irregular geometries     

Runhild A. Klausen  Atgeirr F. Rasmussen  Annette F. Stephansen 《Computational Geosciences》2012,16(2):261-276

Streamline tracing on irregular grids requires reliable interpolation of velocity fields. We propose a new method for direct streamline tracing on polygon and polytope cells. While some numerical methods provide a basis function that can be used for interpolation, other methods provide only the fluxes at the faces of the elements. We introduce the concept of full- and raw-field methods. Full-field methods have built-in interpolation but are often not defined on general grids such as polygonal and polyhedral grids which we examine here. Also, reliability issues may arise on non-simplicial meshes in terms of not being able to reproduce constant velocity fields. We propose an interpolation in H(div) and H(curl) valid on general grids that is based on barycentric coordinates and that reproduces uniform flow. The interpolation can be used to compute the streamline directly on the complex cell geometry. The method generalizes to convex polytopes in 3D, with a restriction on the polytope topology near corners that is shown to be satisfied by several popular grid types. Numerical results confirm that the method is applicable to general grids and preserves uniform flow.  相似文献   

Semi-analytical solutions for stream–aquifer interactions under triangular stream-stage variations and its application to study urbanization impacts in an ungaged watershed of south Texas     

E. Annette Hernandez  Venkatesh Uddameri 《Environmental Earth Sciences》2014,71(6):2547-2557

Simple yet physically based models to evaluate stream–aquifer interactions during a flooding event subject to triangular stream stage variation were developed in this study. The results from the developed models were compared with other analytical and numerical solutions and noted to be very accurate. The study fills an important gap with regard to available analytical and semi-analytical solutions for modeling stream–aquifer interactions, which can be used for evaluating numerical codes. In particular, the developed models are very useful to obtain preliminary insights with regard to bank storage in ungaged watersheds as required for watershed management and planning studies in rapidly urbanizing watersheds. The utility of the model is illustrated by applying it to study the effects of urbanization on stream–aquifer interactions in the Arroyo Colorado River Watershed along the US–Mexico border region. The results indicate that increased urbanization reduces the amount of influx into the banks. The reduction in flood passage time was noted to have a greater impact than the associated rise in stage. The presence of a semi-permeable barrier was seen to mask the effects of urbanization. The model results also implicitly highlight the importance of how water quality variations caused due to urbanization can affect stream–aquifer interactions.  相似文献   

Assessment of groundwater water quality in central and southern Gulf Coast aquifer,TX using principal component analysis     

Venkatesh Uddameri  Vivekanand Honnungar  E. Annette Hernandez 《Environmental Earth Sciences》2014,71(6):2653-2671

Principal component analysis has been applied for source identification and to assess factors affecting concentration variations. In particular, this study utilizes principal component analysis (PCA) to understand groundwater geochemical characteristics in the central and southern portions of the Gulf Coast aquifer in Texas. PCA, along with exploratory data analysis and correlation analysis is applied to a spatially extensive multivariate dataset in an exploratory mode to conceptualize the geochemical evolution of groundwater. A general trend was observed in all formations of the target aquifers with over 75 % of the observed variance explained by the first four factors identified by the PCA. The first factor consisted of older water subjected to weathering reactions and was named the ionic strength index. The second factor, named the alkalinity index explained greater variance in the younger formations rather than in the older formations. The third group represented younger waters entering the aquifers from the land surface and was labeled the recharge index. The fourth group which varied between aquifers was either the hardness index or the acidity index depending on whether it represented the influences of carbonate minerals or parameters affecting the dissolution of fluoride minerals, respectively. The PCA approach was also extended to the well scale to determine and identify the geographic influences on geochemical evolution. It was found that wells located in outcrop areas and near rivers and streams had a larger influence on the factors suggesting the importance of surface water–groundwater interactions.  相似文献   

Identifying influencing wells for gradient estimation in the confined portion of the Gulf Coast aquifer near Kingsville,TX     

Venkatesh Uddameri  Sreeram Singaraju  E. Annette Hernandez 《Environmental Earth Sciences》2014,71(6):2629-2640

Hydraulic gradient is a fundamental aquifer characteristic required to estimate groundwater flow and quantify advective fluxes of pollutants. Graphical and local estimation schemes using potentiometric head information from three or four wells are used to compute hydraulic gradients but suffer from imprecision and subjectivity. The use of linear regression is recommended when hydraulic head data from a groundwater monitoring network consisting of several wells are available. In such cases, statistical influence analysis can be carried out to evaluate how each well within the network impacts the gradient estimate. A suite of five metrics, namely—(1) the hat-values, (2) studentized residuals, (3) Cook’s distance, (4) DFBETAs and (5) Covariance ratio (COVRATIO) are used in this study to identify influential wells within a regional groundwater monitoring network in Kleberg County, TX. The hat-values indicated that the groundwater network was reasonably well balanced and no well exerted an undue influence on the regression. The studentized residuals and Cook’s distance indicated the wells with the highest influence on the regression predictions were those that were close to high groundwater production centers or affected by coastal-aquifer interactions. However, the wells in the proximity of the production centers had the highest impact on the estimated gradient values as ascertained using DFBETAs. The covariance ratio which indicates the sensitivity of a monitoring well on the estimated standard error of regression was noted to be significant at most wells within the network. Therefore, networks seeking to address changes in groundwater gradients due to climate and anthropogenic influences need to be denser than those used to ascertain synoptic gradient estimates alone. The magnitude of the groundwater velocity was greatly underestimated when the influential wells were excluded from the network. The direction of flow was affected to a lesser extent, but a complete gradient reversal was noted when the network consisted of only four peripheral wells. The influence analysis therefore provides a valuable tool to assess the importance of individual wells within a monitoring network and can therefore be useful when existing networks are to be pruned due to fiscal constraints.  相似文献   

Impacts of sea-level rise and urbanization on groundwater availability and sustainability of coastal communities in semi-arid South Texas     

Venkatesh Uddameri  Sreeram Singaraju  E. Annette Hernandez 《Environmental Earth Sciences》2014,71(6):2503-2515

The sea levels along the semi-arid South Texas coast are noted to have risen by 3–5 mm/year over the last five decades. Data from General Circulation Models (GCMs) indicate that this trend will continue in the 21st century with projected sea level rise in the order of 1.8–5.9 mm/year due to the melting of glaciers and thermal ocean expansion. Furthermore, the temperature in South Texas is projected to increase by as much as 4 °C by the end of the 21st century creating a greater stress on scarce water resources of the region. Increased groundwater use hinterland due to urbanization as well as rising sea levels due to climate change impact the freshwater-saltwater interface in coastal aquifers and threaten the sustainability of coastal communities that primarily rely on groundwater resources. The primary goal of this study was to develop an integrated decision support framework to assist land and water planners in coastal communities to assess the impacts of climate change and urbanization. More specifically, the developed system was used to address whether coastal side (primarily controlled by climate change) or landward side processes (controlled by both climate change and urbanization) had a greater control on the saltwater intrusion phenomenon. The decision support system integrates a sharp-interface model with information from GCMs and observed data and couples them to statistical and information-theoretic uncertainty analysis techniques. The developed decision support system is applied to study saltwater intrusion characteristics at a small coastal community near Corpus Christi, TX. The intrusion characteristics under various plausible climate and urbanization scenarios were evaluated with consideration given to uncertainty and variability of hydrogeologic parameters. The results of the study indicate that low levels of climate change have a greater impact on the freshwater-saltwater interface when the level of urbanization is low. However, the rate of inward intrusion of the saltwater wedge is controlled more so by urbanization effects than climate change. On a local (near coast) scale, the freshwater-saltwater interface was affected by groundwater production locations more so than the volume produced by the community. On a regional-scale, the sea level rise at the coast was noted to have limited impact on saltwater intrusion which was primarily controlled by freshwater influx from the hinterlands towards the coast. These results indicate that coastal communities must work proactively with planners from the up-dip areas to ensure adequate freshwater flows to the coast. Field monitoring of this parameter is clearly warranted. The concordance analysis indicated that input parameter sensitivity did not change across modeled scenarios indicating that future data collection and groundwater monitoring efforts should not be hampered by noted divergences in projected climate and urbanization patterns.  相似文献   

Marine pollution network euromar-mermaid: Results of the experimental operation     

H. -D. Knauth  F. Schroeder  R. Menzel  E. Gebhart  S. Marx  D. Kohnke  F. Holzkamm  H. Nies  N. Theobald 《Ocean Dynamics》1997,49(2-3):385-407

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