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11.
A fiber-optic-based system for remote measurement of time-resolved fluorescence emission spectra is described and characterized. A pulsed nitrogen laser is used to induce fluorescence and a time-gated, one-dimensional photodiode array is used to measure the decay of the fluorescence emission spectra. The results compare favorably with reported values for well characterized compounds having fluorescence decay times in the range 4–50 ns. The potential of using time-resolved fluorimetry (TRF) over fiber-optic cables as a means of improving the specificity of remote fluorescence determinations of spectrally similar polycyclic aromatic hydrocarbons in sea water is demonstrated. 相似文献
12.
Heat capacities of concentrated multicomponent aqueous electrolyte solutions at various temperatures
Boris S. Krumgalz Ilan A. Malester Irving J. Ostrich Frank J. Millero 《Journal of solution chemistry》1992,21(7):635-649
The specific heat capacities of the aqueous multicomponent system NaCl +KCl+MgCl2+CaCl2 with ionic strength between 8.3 and 9.6 (resembling Dead Sea waters) were measured between 15°C and 45°C. The obtained data were fitted to an empirical equation as a function of concentration and temperature. The thermodynamic functions of the studied multicomponent system were found to be strongly influenced by changes in MgCl2 concentrations. The application of Young's rule to such concentrated systems was checked at 25°C. The calculated (by Young's rule) specific heat capacitiesC
p and apparent molar heat capacities Cp, of these multicomponent electrolyte solutions were in reasonable agreement with the measured values (–0.008 J-g–1-K–1 and –2.6 J-mol–1-K–1, respectively). 相似文献
13.
Inductively coupled plasma mass spectrometry (ICP-MS) was used in an isotope dilution mode to assay small-volume (0.25 ml) sediment pore waters for their uranium contents, using 236U as the spike. The only pretreatment required was a simple dilution by a factor of 20, which gave sufficient volume for three replicate analyses per sample. Rapid and accurate results were obtained for a variety of samples and standards, ranging in concentration from 0.05 to 10 ng U ml?1. A suite of 30 samples can be analysed in less than 6 h by this method. The relative standard deviation was better than 1.9%, with a detection limit, based on 3σ background, of 2 pg U ml?1 in solution (40 pg ml?1 in samples). Sea water is a difficult matrix for ICP-MS and thus the method is generally suitable for uranium determinations in many other sample solutions. 相似文献
14.
Pantelis Bampoulis Kai Sotthewes Edwin Dollekamp Bene Poelsema 《Surface Science Reports》2018,73(6):233-264
The behavior of water in close proximity to other materials under ambient conditions is of great significance due to its importance in a broad range of daily applications and scientific research. The structure and dynamics of water at an interface or in a nanopore are often significantly different from those of its bulk counterpart. Until recently, experimental access to these interfacial water structures was difficult to realize. The advent of two-dimensional materials, especially graphene, and the availability of various scanning probe microscopies were instrumental to visualize, characterize and provide fundamental knowledge of confined water. This review article summarizes the recent experimental and theoretical progress in a better understanding of water confined between layered Van der Waals materials. These results reveal that the structure and stability of the hydrogen bonded networks are determined by the elegant balance between water-surface and water-water interactions. The water-surface interactions often lead to structures that differ significantly from the conventional bilayer model of natural ice. Here, we review the current knowledge of water adsorption in different environments and intercalation within various confinements. In addition, we extend this review to cover the influence of interfacial water on the two-dimensional material cover and summarize the use of these systems in potential novel applications. Finally, we discuss emerged issues and identify some flaws in the present understanding. 相似文献
15.
We present the results of a re-analysis of a previously published carbon isotope data-set related to coralline sponges in the Caribbean Sea. The original interpretation led to the discrimination between a pre-industrial period, with a signal controlled by solar-induced climatic variations, followed by the industrial era, characterized by a progressive δ13C negative shift due to the massive anthropogenic carbon emissions. Our re-analysis allowed to extract from the raw isotopic data evidence of a solar forcing still visible during the industrial era, with a particular reference to the 88-year Gleissberg periods. These signals are related to slope changes in both the δ13C versus time and the δ13C versus carbon emission curves. 相似文献
16.
Andrea Gambaro Ivo Moret Rossano Piazza Carlo Andreoli Eleonora Da Rin Gabriele Capodaglio 《International journal of environmental analytical chemistry》2013,93(6-7):401-412
The temporal evolution of concentrations of dimethylsulphide (DMS), its precursor dimethylsulphoniopropionate (DMSP) and chlorophyll a is surveyed weekly in the water column and in a landfast ice core at a coastal station of Gerlache Inlet (Terra Nova Bay, Antarctica) from 27 November 2000 to 14 February 2001. The DMS and DMSP profile concentrations in the water column are similar and show a clear temporal trend, with minimum values (<0.7?nM) at all depths occurring on 27 November 2000 and maximum values (4.8 × 102?nM for DMS and 1.8 × 102?nM for DMSP) in surface water on 27 December 2000 for DMS and on 19 December 2000 for DMSP. When the sea-ice cover is present, the temporal evolution of DMSP closely follows that of chlorophyll a in the water column, supporting the idea that DMSP, and therefore DMS, has a phytoplanktonic origin. However, when the ice cover breaks up during the late austral summer, a second phytoplankton bloom occurs, while the DMSP concentration in the sea-water column remains very low. In the ice core, the results show higher concentrations of DMSP than those of the underlying sea water, highlighting the important role of sea ice in the sulphur cycle of the Antarctic ecosystem. 相似文献
17.
P. Garrigues C. Raoux P. Lemaire A. Mathieu D. Ribera J. F. Narbonne 《International journal of environmental analytical chemistry》2013,93(3):379-387
Abstract Biochemical indices based on enzymatic activities have been determined in fish and mussels sampled in various different coastal locations in the Mediterranean Sea. Preliminary results show a good agreement between biochemical measurements in marine organisms and chemical analyses of polycyclic aromatic hydrocarbons present in sediments. The results obtained suggest the use of biochemical indices for application in chemical contaminant biomonitoring. 相似文献
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