Search results for: cores
#32473425 2020/05/16 To Up
Trace metal variability controlled by hydrodynamic processes in a polluted inner shelf environment (Besòs prodelta, NW Mediterranean).Trace metal pollution of coastal sediment is monitored in many countries to control its evolution and the effectiveness of preventive and corrective measures. However, temporal variability of trace metal pollution is not always due to changes in pollution management, as natural processes can induce a significant variability in the trace metal content of sediment and particulate matter, especially in strongly polluted coastal areas. To study this variability, time series of trace metals in particulate matter and bottom sediments were recorded along with hydrographic and hydrodynamic parameters in the most highly polluted zone of the Besòs River prodelta. Two benthic tripods equipped with current meters, turbidimeters and sediment traps were deployed at 20 and 30 m water depth from late-September to mid-June and sediment cores were taken four times at each site during the deployment period. Trace metal content in the trapped particulate matter and the surface sediment increased during storm events, which can resuspend and erode several cm of subsurface sediments with higher pollution levels from earlier industrial times. After the storms, significant accumulation of less polluted sediment began, and near-bottom currents redistributed it, decreasing trace metal contents in surface sediments and trapped particulate matter. Therefore, energy conditions previous to monitoring sampling must be considered in order to evaluate the evolution of trace metals in inner shelf polluted sediments.
Albert Palanques, Laura López, Jorge Guillén, Pere Puig
1415 related Products with: Trace metal variability controlled by hydrodynamic processes in a polluted inner shelf environment (Besòs prodelta, NW Mediterranean).100.00 ug96T1000 100ug1 Set100ug Lyophilized1 Set100ug1 mg100ug Lyophilized
#32473000 2020/05/30 To Up
Halogenated flavones and isoflavones: a state-of-art on their synthesis.Flavonoid is a family of compounds present in the everyday consumption plants and fruits, contributing to a balanced diet and having health effects. Being a scaffold for new drugs and presenting a wide range of applicability in illness treatment gives them also an impact in medicine. Among the several types of flavonoids, flavone and isoflavone derivatives can be highlighted due to their prevalence in nature and biological activities already established. The standard synthetic route to obtain both halogenated flavones and isoflavones is through the use of already halogenated starting materials. Halogenation of the flavone and isoflavone core is less common because it is more complicated and involves some selectivity issues.
Ricardo A L S Santos, Diana C G A Pinto, M Clara F Magalhães, Artur M S Silva
2544 related Products with: Halogenated flavones and isoflavones: a state-of-art on their synthesis.500 MG1000 tests100ug Lyophilized100ul50 ug 100ug0.1 mg100 mg100ug Lyophilized100ug Lyophilized1.00 flask
#32472586 2020/05/29 To Up
The Impact of Aggregation on the Photophysics of Spiro-bridged Heterotriangulenes.We report on the impact of the central heteroatom on structural, electronic, and spectroscopic properties in a series of heterotriangulenes including a spirofluorene-bridged triphenylamine, -phosphine, and -phosphine oxide and provide a detailed study on their aggregates. The in-depth analysis of their molecular structure by NMR spectroscopy and X-ray crystallography was complemented by density functional theory calculations to shed light on the electronic structure. This analysis was particularly helpful to deconvolute the complex fluorescence spectra with contributions from the peripheral fluorenes and the respective heteroaromatic cores. Going beyond the molecular scale, we examined the aggregation behavior of these heterotriangulenes in THF/H 2 O mixtures and analyzed the amount as well as the size of the aggregates by static and dynamic light scattering. The excited-state interactions within the aggregates at high water contents were found to be similar to those found in the solid state. In addition, a plethora of morphologies and superstructures were detected by scanning electron microscopy when the dispersions were drop-casted and dried.
Milan Kivala, Marcel Krug, Maximilian Wagner, Tobias A Schaub, Wen-Shan Zhang, Christoph M Schüßlbauer, Johannes D R Ascherl, Peter W Münich, Rasmus R Schröder, Franziska Gröhn, Pavlo O Dral, Mario Barbatti, Dirk M Guldi
2944 related Products with: The Impact of Aggregation on the Photophysics of Spiro-bridged Heterotriangulenes.5 G2000 IU100.00 ul1500 Units10
#32470909 2020/05/26 To Up
GEANT4 Monte Carlo simulations for virtual clinical trials in breast X-ray imaging: Proof of concept.Virtual clinical trials (VCT) are in-silico reproductions of medical examinations, which adopt digital models of patients and simulated devices. They are intended to produce clinically equivalent outcome data avoiding long execution times, ethical issues related to radiation induced risks and huge costs related to real clinical trials with a patient population. In this work, we present a platform for VCT in 2D and 3D X-ray breast imaging. The VCT platform uses Monte Carlo simulations based on the Geant4 toolkit and patient breast models derived from a cohort of high resolution dedicated breast CT (BCT) volume data sets. Projection images of the breast and three-dimensional glandular dose maps are generated for a given breast model, by simulating both 2D full-field digital mammography (DM) and 3D BCT examinations. Uncompressed voxelized breast models were derived from segmented patient images. Compressed versions of the digital breast phantoms for DM were generated using a previously published digital compression algorithm. The Monte Carlo simulation framework has the capability of generating and tracking ~10 photons/s using a server equipped with 16-cores and 3.0 GHz clock speed. The VCT platform will provide a framework for scanner design optimization, comparison between different scanner designs and between different modalities or protocols on computational breast models, without the need for scanning actual patients as in conventional clinical trials.
F di Franco, A Sarno, G Mettivier, A M Hernandez, K Bliznakova, J M Boone, P Russo
1202 related Products with: GEANT4 Monte Carlo simulations for virtual clinical trials in breast X-ray imaging: Proof of concept.
#32469769 2020/04/28 To Up
Determination of background geochemistry of an Amazon estuary: The Cuñaní Estuary - Amapá.This study aims to determinate the background geochemistry values for 23 chemical elements on the Amapá coastline. To do so, 8 cores were sampled (≤70 cm) along the Cuñaní Estuary. The metal concentrations were measured by means of inductively coupled plasma mass spectrometry. In mg.kg-1, the background values for Ba, Sr, Y, Sc, V, CrO, Co, Ni, Cu, Zn, Ga, As, Rb, Nb, Sn, Cs, Ta, W, Hg, Pb, Bi, Th, and U were, respectively, 392.41, 133.29, 29.22, 12.80, 109.13, 0.008, 13.82, 22.69, 19.73, 75.09, 19.50, 14.77, 94.81, 15.62, 3.38, 6.59, 1.05, 1.82, 0.04, 19.02, 0.27, 13.25, and 3.57. The background geochemistry values for the region are an important tool for monitoring the metal concentrations and serve as a baseline for comparison with possible incidents of contamination with these elements on the Amapá coast.
Diego de Arruda Xavier, Valdenira Ferreira Dos Santos, Artur Gustavo Oliveira de Miranda, José Francisco Berrêdo
2240 related Products with: Determination of background geochemistry of an Amazon estuary: The Cuñaní Estuary - Amapá.1 x 96100.00 ul100.00 ul1 ml 5 G0.1 mg
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#32469760 2020/04/20 To Up
Test deformation and chemistry of foraminifera as response to anthropogenic heavy metal input.Benthic foraminifera are sensitive to environmental changes and widely used as tools to monitor pollution. Rising numbers of deformed tests are often used as indicator for elevated levels of heavy metals, but little is known about the relation between heavy metal incorporation into foraminiferal tests and the formation of test deformities. Here, two sediment cores from the south-eastern North Sea are compared, regarding the occurrence of deformed foraminiferal tests, foraminiferal test chemistry (ICP-MS) and bulk sediment Pb content (XRF). The total abundance of deformed foraminiferal tests seems not to align temporarily with historical heavy metal pollution. Therefore, we suggest that foraminifera react with test deformation to other environmental stressors than the studied heavy metals. Test chemistry reflects historical increased bulk sediment heavy metal content, despite a slight temporal offset. We propose that Pb (and Cd) are only incorporated into foraminiferal tests above a yet to be defined threshold of pollution.
S Boehnert, A R Birkelund, G Schmiedl, H Kuhnert, G Kuhn, H C Hass, D Hebbeln
1944 related Products with: Test deformation and chemistry of foraminifera as response to anthropogenic heavy metal input.430 tests300 tests540 tests500 tests100tests600 Tests / Kit100 tests1 kit(96 Wells)24 tests100tests100 assays384 tests
#32469754 2020/05/03 To Up
Distribution and diagenesis of trace metals in marine sediments of a coastal Mediterranean area: St Georges Bay (Lebanon).St Georges Bay of Lebanon's coast is an open bay to the Mediterranean Sea. It is exposed to numerous anthropogenic activities such as industrial effluent, untreated wastewater discharge and maritime activities resulting in increasing chemical contamination, especially with trace metals. Contamination with trace metals (Cu, Cd, Co, Pb, As, Ag and Hg) and the influence of early diagenesis on their distribution were studied on both sediments and waters. For this purpose, sediment cores were collected, then treated under inert atmosphere to retrieve pore waters and solid fraction. The area appears to be seriously impacted by the materials transported by the Beirut River and/or by direct inputs, and recent land reclamation using dumpsite material. The sediments showed a significant level of contamination. Element mobility was studied by selective extraction on sediments. The mobility of trace elements from solid fraction to pore waters is controlled by the Fe/Mn cycle and organic matter.
Amonda El Houssainy, Carine Abi-Ghanem, Duc Huy Dang, Céline Mahfouz, Dario Omanović, Gaby Khalaf, Stéphane Mounier, Cédric Garnier
1277 related Products with: Distribution and diagenesis of trace metals in marine sediments of a coastal Mediterranean area: St Georges Bay (Lebanon).1
#32469741 2020/05/29 To Up
Analysis of environmental and microbiological changes in Onagawa Bay immediately after the tsunami of the Great East Japan Earthquake based on sediment cores.We investigated two sediment cores to understand whether a tsunami in Onagawa Bay, Japan caused environmental changes. The value of δC ranged from -21.9‰ to -24.3‰ and of δN ranged from 5.1 to 5.9‰. We conclude that the source of the sediment in the present study area was mainly oceanic and not terrestrial. The chlorophyll concentration ranged from 1.8 to 4.0 μg/g ww, and did not vary greatly between surface and bottom layers. We inferred that all layers were deposited after the tsunami. The major phytoplankton taxa in sediments were diatoms from DNA sequencing. The presence of harmful dinoflagellates was minor. The concentrations of several heavy metals decreased slightly after the tsunami. We inferred that heavy metals in sediments were diluted by the tsunami disturbance. The land in Onagawa suffered serious damage, but disturbance of the seabed was much less evident.
Yutaka Okumura, Kenji Kaneko, Hiroto Ota, Hiromitsu Nagasaka, Motoyuki Hara
2411 related Products with: Analysis of environmental and microbiological changes in Onagawa Bay immediately after the tsunami of the Great East Japan Earthquake based on sediment cores.1
#32467955 2020/05/29 To Up
Iodine activation: a general method for catalytic enhancement of thiolate monolayer-protected metal clusters.To enhance catalytic activity, the present study details a general approach for partial thiolate ligand removal from monolayer-protected clusters (MPCs) by straightforward in situ addition of iodine. Two model reactions are examined to illustrate the effects on the catalytic activity of glutathione (SG)-capped Au MPCs serving as a catalyst for the NaBH4 reduction of 4-nitrophenol to 4-aminophenol and SG-capped Pd MPCs serving as a catalyst for the hydrogenation/isomerization of allyl alcohol. Iodine addition promoted partial thiolate ligand removal from both MPCs and improved the catalytic properties, presumably due to greater surface exposure of the metal cores as a result of ligand dissociation. The rate of 4-nitrophenol reduction increased from 0.066 min-1 in the absence of I2 to 0.505 min-1 in the presence of 2.0 equivalents I2 (equivalents based on total ligated glutathione). The reaction of allyl alcohol to produce 1-propanol and propanal was similarly accelerated as indicated by the increase in turnover frequency from 131 to 230 moles products per moles catalyst per h by addition of 0.2 equivalents I2. In both reactions, as the amount of I2 added increases the catalyst recyclability decreases due to catalyst instability. Low equivalents of I2 are optimal when considering both reaction rate and catalyst recyclability.
Tirtha R Sibakoti, Jacek B Jasinski, Michael H Nantz, Francis P Zamborini
2963 related Products with: Iodine activation: a general method for catalytic enhancement of thiolate monolayer-protected metal clusters.100μg100μg100μg100μg100μg100Tests100μg100μg100μg100μg100ug0.2 mg
#32461700 // To Up
Determination of Cr(III) solids formed by reduction of Cr(VI) in a contaminated fractured bedrock aquifer: Evidence for natural attenuation of Cr(VI).Hexavalent chromium Cr(VI) is toxic and can be highly mobile in many aquifer systems. Redox reactions with naturally occurring minerals and organic compounds can reduce Cr(VI) to Cr(III), forming labile Cr(III) oxyhydroxide precipitates, which is a natural attenuation process. In fractured bedrock aquifers, reduction of Cr(VI) in the rock matrix can enhance attenuation beyond that from matrix diffusion only, and potentially reduce back diffusion if concentrations in fractures decline following source reduction via natural processes or engineered remediation. In this study, we develop an extraction method for labile Cr(III) precipitates from Cr(VI) reduction using 5% hydrogen peroxide (HO). Combining Cr(III) extractions with an established sodium hydroxide (NaOH) method for determination of Cr(VI) concentrations in rock porewater, a measure of the labile Cr(III) and Cr(VI) fractions in geologic samples is achieved. The methods were applied to cores from a contaminated groundwater system in fractured porous bedrock in order to assess the effectiveness of natural attenuation and whether Cr(VI) mass that diffused into the bedrock matrix was undergoing reduction. Detailed vertical distributions display two depth intervals with corresponding elevated concentrations of Cr(VI) in the porewater and extractable total Cr. The correspondence of Cr(VI) and labile Cr(III) provides evidence for reduction of Cr(VI) contamination in the bedrock matrix. Mineralogical analysis suggests that Fe(II)-bearing minerals, chlorite and biotite are the most likely candidates for natural reductants. This study provides evidence for the natural attenuation of anthropogenic Cr(VI) contamination in the porewater of a fractured bedrock aquifer, and it outlines a quantitative method for evaluating the effectiveness of natural attenuation in groundwater systems.
Jiujiang Zhao, Tom Al, Steven W Chapman, Beth L Parker, Katherine R Mishkin, Diana Cutt, Richard T Wilkin
1960 related Products with: Determination of Cr(III) solids formed by reduction of Cr(VI) in a contaminated fractured bedrock aquifer: Evidence for natural attenuation of Cr(VI).100Tests400Tests 5 G100ug Lyophilized24 tests1 Set100ug Lyophilized
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