Cloud point extraction of napropamide and thiabendazole from water and soil

The micellar extraction and enrichment of napropamide and thiabendazole using Genapol X 80 is described. Combined with their quantification by fluorescence, detection limits below 0.2 g/l with recovery rates of up to 95% were achieved. The recovery could be improved by lowering the extraction temperature and purificaton of the surfactants. This extraction method has been applied to the isolation and preconcentration of napropamide from standard soils. Experimental parameters affecting the recovery rates were examined.     

Determination of mercury in soils and sediments by graphite furnace atomic absorption spectrometry with slurry sampling

A graphite furnace atomic absorption spectrometric procedure for the determination of mercury is presented, in which the samples are suspended in a solution containing hydrofluoric and nitric acids. Silver nitrate (4% m/v) and potassium permanganate (3%) are incorporated, in the order specified, and aliquots are directly introduced into the graphite furnace. A fast heating programme with no conventional pyrolysis step is used. The detection limit for mercury in a 125 mg ml⁻¹ suspension is 0.1 μg g⁻¹. Calibration is performed by using aqueous standards. The reliability of the procedure is proved by analysing certified reference materials.     

Semi-micro solvent extraction as a rapid and efficient preconcentration technique for the determination of n-alkanes in oil-contaiminated water and soil samples by capillary gas chromatography

Summary In this study, a rapid and efficient semi-micro extraction procedure is presented for the extraction of some higher n-alkanes from water and soil samples. In the case of water samples n-hexane was used as the organic phase in a phase volume ratio (volume of aqueous phase/volume of organic phase) higher than 285, while in the case of soil samples, extraction with n-hexane was carried out in the presence of an excess of 2 M NaCl solution. The extraction rate from soil samples is very high and is better than Soxhlet extraction, comparable with supercritical fluid extraction. High preconcentration factor in water samples allows the limits of detection to be in the ng.mL⁻¹ level with the use of gas chromatographic analysis. Flame ionization detector was used for monitoring the analytes. The obtained recoveries of all studied compounds from both water and soil samples are higher than 90%. This method was successfully used to determine some n-alkanes in municipal wastewater and contaminated soil.     

Neutral loss of amino acid residues from protonated peptides in collision-induced dissociation generates N- or C-terminal sequence ladders

The widespread occurrence of the neutral loss of one to six amino acid residues as neutral fragments from doubly protonated tryptic peptides is documented for 23 peptides with individual sequences. Neutral loss of amino acids from the N-terminus of doubly charged tryptic peptides results in doubly charged y-ions, forming a ladder-like series with the ions [M + 2H](2+) = y(max) (2+), y(max - 1) (2+), y(max - 2) (2+), etc. An internal residue such as histidine, proline, lysine or arginine appears to favor this type of fragmentation, although it was sometimes also observed for peptides without this structure. For doubly protonated non-tryptic peptides with one of these residues at or near the N-terminus, we observed neutral loss from the C-terminus, resulting in a doubly charged b-type ion ladder. The analyses were performed by Q-TOF tandem mass spectrometry, facilitating the recognition of neutral loss ladders by their 2+ charge state and the conversion of the observed mass differences into reliable sequence information. It is shown that the neutral loss of amino acid residues requires low collision offset values, a simple mechanistic explanation based on established fragmentation rules is proposed and the utility of this neutral loss fragmentation pathway as an additional source for dependable peptide sequence information is documented.     

Robust risk-taking under a sustainable constraint

We consider a model in which the representative investor makes optimal portfolio and consumption choices robust to ambiguity with a sustainable constraint. We find that the influences of ambiguity on risk-taking are two ways. Those are gambling when the risk-free interest rate is less than a critical value, but derisk when the risk-free interest rate is greater than the critical value. Moreover, the erosion of ambiguity on consumption is more substantial in constrained cases, and ambiguity will magnify welfare losses.     

Second-order properties of the loss probability inM/M/s/s +c systems

The Erlang loss function, which gives the steady state loss probability in anM/M/s/s system, has been extensively studied in the literature. In this paper, we look at the similar loss probability inM/M/s/s + c systems and an extension of it to nonintegral number of servers and queue capacity. We study its monotonicity properties. We show that the loss probability is convex in the queue capacity, and that it is convex in the traffic intensity if is below some ^* and concave if is greater that ^*, for a broad range of number of servers and queue capacities. We prove that the one-server loss system is the onlyM/M/s/s +c system for which the loss probability is concave in the traffic intensity in all its range.Research supported by Grant BD/645/90-RM from Junta Nacional de Investigação Científica e Tecnológica.On leave from: Departamento de Matemática, Instituto Superior Técnico, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal.     

Correlation Analysis of the Runoff of the Rivers and the Seisms in China

In recent hundred years the annual discharge variations of the Changjiang River (represented by the Yichang station) and the Huanghe River (represented by Shanxian and Tangnaihe, respectively) have closely related to the geographical distribution of the earthquakes coming about in China in the same year, Both the occurrence of the destructive seism or seismic swarm in the river basins and the disappearance of the shocks in the east and south of the basins are the conditions that the Changjiang and Huanghe Rivers are the high flow while that the strong earthquake of magnitude 7 or more occurred in North China is the condition for the Changjiang low flow year and that of 6 or more in the Qilian Mountains area is for the Huanghe River. In the latter part of this paper, a 2-year sample is given to explain that the conditions of the 2 rivers being high flow years are that the north-south seismic belt is active and in the meanwhile no seism occurred in South China, and those of the low flow year are that the     

A new Co(II) complex with N,O-donor Schiff base: Synthesis, structure and characterization

A new Co(II) complex with tridentate Schiff base ligand with a N,N,O donor set has been synthesized and characterized by single X-ray technique and spectroscopic techniques. The thermochemical properties have been studied. X-ray structure analysis of the title compound Co(II)L₂ [HL = 2-methyl-6-(2′-hydroxybenzylideneamino) pyridine] shows that the polyhedron around Co(II) is a distorted tetrahedron, and the self-assembly via intermolecular π-π interactions leads to a three-dimensional network. Crystal data for the title complex C₂₆H₂₂CoN₄O₂: Monoclinic, space group Ia, a = 11.741(7) Å, b = 8.149(5) Å, c = 22.764(16) Å, β = 98.530(12)°, V = 2154(2) ų, Z = 4.     

Unraveling the mystery of efficacy in Chinese medicine formula: New approaches and technologies for research on pharmacodynamic substances

Traditional Chinese medicine (TCM) is the key to unlock treasures of Chinese civilization. TCM and its compound play a beneficial role in medical activities to cure diseases, especially in major public health events such as novel coronavirus epidemics across the globe. The chemical composition in Chinese medicine formula is complex and diverse, but their effective substances resemble “mystery boxes”. Revealing their active ingredients and their mechanisms of action has become focal point and difficulty of research for herbalists. Although the existing research methods are numerous and constantly updated iteratively, there is remain a lack of prospective reviews. Hence, this paper provides a comprehensive account of existing new approaches and technologies based on previous studies with an in vitro to in vivo perspective. In addition, the bottlenecks of studies on Chinese medicine formula effective substances are also revealed. Especially, we look ahead to new perspectives, technologies and applications for its future development. This work reviews based on new perspectives to open horizons for the future research. Consequently, herbal compounding pharmaceutical substances study should carry on the essence of TCM while pursuing innovations in the field.     

Dielectric properties of beryllia ceramics in the near-millimeter wavelength range

We report the refractive indices and absorption coefficients for four beryllia (BeO) ceramic samples. These dielectric properties have been measured over the range from 4 to 18 cm^–1 by use of a Michelson interferometer. The index n, follows the linear relationship n=0.6517 cm³/g×+0.7130 with density, , over the range 2.8<<3.0 g/cm³.