两自由度周转轮系机械效率分析公式的评议

本文采用Radzimovsky原始推荐的分式严格讨论后,证明用于计算两自由度周转轮系机械效率的不同方法的数值等效,本文还包括用某些公式的数据要求过多方面的讨论.     

Landscape-level approach to assess aquatic exposure via spray drift for pesticides: a case study in a Mediterranean area

The development of methods to extract information from landscape analysis to refine risk assessment is becoming increasingly important. This paper presents results from a pesticide surface water exposure assessment at the watershed scale, based on a combination of edge of field studies, large-scale monitoring studies, and modeling activities with GIS-based landscape analysis methodologies covering an area of approximately 3200 ha surrounding the Simeto River in Sicily (Italy). The dynamic behavior of the pesticide chlorpyrifos-methyl was modeled in two different steps: calculation of the fraction of the application rate that is deposited beyond the field edge and simulation of the fate and persistence of the pesticide in the aquatic environment. Drift loads showed high spatial variability. Considering spray drift deposition as a fraction of the pesticide application rate, 60% of the results were < or = 0.02 (equal to 0.04 mg/m2). Only 8.5% of the results were above 0.5. The highly variability of the landscape factors was reflected in the results. More than 60% of the predicted pesticide concentrations were less than the limit of quantification (0.05 microg/L), affecting about 75% of the total length of the river tract analyzed. Predicted pesticide concentrations were higher than 0.1 microg/L in 23% of cases, but this corresponded to an insignificant portion of the river (1.2% of the total length). These results suggest that management options, such as increased no-spray zones, could provide further protection for surface water. These could be modeled to illustrate their overall impact. As an alternative, the introduction of a 20-m no-spray zone clearly reduced potential exposure, and 92% of the water body was protected. Estimated data are in agreement with data collected during a field monitoring study.     

Enantioselective hydrolysis of some 2-aryloxyalkanoic acid methyl esters and isosteric analogues using a penicillin G acylase-based HPLC monolithic silica column

A technique based on liquid chromatography has been developed to facilitate studies of enantioselectivity in penicillin G acylase (PGA)-catalyzed hydrolysis of some 2-aryloxyalkanoic acid methyl esters and isosteric analogues. PGA was covalently immobilized on an aminopropyl monolithic silica support to create an immobilized HPLC-enzyme reactor. Two sets of experimental data were drawn to calculate the enantioselectivity (E) of the kinetically controlled enantiomer-differentiating reaction, the degree of substrate conversion and the enantiomeric excess of the product. The developed enzymatic reactor was coupled through a switching valve to an achiral analytical column for separation and quantitation of the hydrolysis products. The enantiomeric excess was determined off-line on a PGA-chiral stationary phase. In this way, highly precise E values were determined. A computational study related to the hydrolysis of the considered racemic esters was also carried out in order to unambiguously clarify both the substrate specificity and the enantioselectivity displayed by PGA.     

Rapid depletion of marbofloxacin residues in rabbit after therapeutic treatment

Although rabbit meat production represents a very small percentage of the world meat market, this percentage has been growing continuously during the last 30 years. Rabbit is considered a minor food species, and therefore no drugs are specifically registered for this animal. This situation encourages rabbit farmers to make off-label use of antibacterial drugs authorized for food-producing animal species other than rabbits. In the present study, the distribution and elimination of the fluoroquinolone antibacterial agent marbofloxacin in rabbit muscle, liver, and kidney was investigated. Marbofloxacin was chosen as a representative of a new generation of antibacterial drugs active against most gram-positive and gram-negative bacteria and mycoplasms; it is well tolerated and has short elimination times in bovine and swine species. Rabbits were treated with marbofloxacin at 2 mg kg of body weight(-1) for 5 days. Residual concentrations in liver, kidney, and muscle tissues were determined posttreatment with high-performance liquid chromatography and fluorescence detection. Marbofloxacin was rapidly distributed and eliminated from rabbit tissues. Concentrations were higher in the liver and kidney than in muscle. However, 48 h after the end of treatment, marbofloxacin concentrations dropped below the maximum residue level fixed for this antibacterial drug in cattle and pigs. Considering the efficacy of marbofloxacin for the treatment of the most common rabbit diseases, its tolerability, and its short elimination time as verified in the present study, use of this antibacterial drug could be extended to therapeutic treatment of rabbits.     

Nanopatterned platinum electrodes by focused ion beam in single palladium nanowire based devices

In this paper we present different devices, working as hydrogen sensors, based on single palladium nanowire and realized combining focused ion beam and dielectrophoresis techniques. The combination of these two techniques consists in the employ of focused ion beam for electrode patterning onto silicon/silicon dioxide substrates, followed by the assembly of a single palladium nanowire applying between electrodes an electric field at fixed frequency (dielectrophoresis) to a palladium nanoparticles solution. The nanowire morphology can be branched or not, depending on the applied frequency value. The devices are characterized in hydrogen environment at room temperature and their responses are compared.     

Looking for Efficient G‐Quadruplex Ligands: Evidence for Selective Stabilizing Properties and Telomere Damage by Drug‐Like Molecules

There is currently significant interest in the development of G‐quadruplex‐interactive compounds, given the relationship between the ability to stabilize these non‐canonical DNA structures and anticancer activity. In this study, a set of biophysical assays was applied to evaluate the binding of six drug‐like ligands to DNA G‐quadruplexes with different folding topologies. Interestingly, two of the investigated ligands showed selective G‐quadruplex‐stabilizing properties and biological activity. These compounds may represent useful leads for the development of more potent and selective ligands.     

A survey of ochratoxin A contamination in feeds and sera from organic and standard swine farms in northwest Italy

BACKGROUND: A survey was carried out on conventional (n = 11) and organic (n = 4) swine farms in northwest Italy in order to investigate the occurrence of ochratoxin A (OTA) in feed and serum samples collected from September 2006 to March 2009. Each farm was sampled twice and a total of 30 feed samples and 285 serum samples were collected. OTA levels were determined through extraction, immunoaffinity column purification and high‐performance liquid chromatography analysis coupled with fluorimetric detection. RESULTS: All feed samples resulted to be contaminated with OTA at levels ranging from 0.22 to 38.4 µg kg^?1. The OTA concentrations found in organic feed samples were significantly higher (P < 0.05) than those found in conventional feed samples. All serum samples resulted to be contaminated with OTA at levels ranging from 0.03 to 6.24 ng mL^?1. The OTA concentrations found in organic serum samples were significantly higher (P < 0.001) than those found in conventional serum samples. CONCLUSION: None of the feed samples contained more than the maximum level (50 µg OTA kg^?1, considering a feed moisture content of 120 g kg^?1) recommended by the European Commission for OTA in complementary and complete swine feedstuffs. The OTA contamination of organic feed and serum samples was found to be significantly higher than that of conventional feed and serum samples. Copyright © 2010 Society of Chemical Industry     

Identification and measurement of illicit drugs and their metabolites in urban wastewater by liquid chromatography-tandem mass spectrometry

Residues of illicit drugs and their metabolites that are excreted by humans may flow into and through wastewater treatment plants. The aim of this study was to develop a method for the determination of cocaine, amphetamines, morphine, cannabinoids, methadone, and some of their metabolites in wastewater. Composite 24-h samples from urban treatment plants were enriched with deuterated internal standards before solid-phase extraction. High-pressure liquid chromatography tandem mass spectrometry with multiple reaction monitoring was used for quantitation. Recoveries were generally higher than 80%, and limits of quantifications were in the low nanograms-per-liter range for untreated and treated wastewater. The overall variability of the method was lower than 10% for untreated and 5% for treated wastewater. The method was applied to wastewater samples coming from two treatment plants in Italy and Switzerland. Quantification ranges were found to be 0.2-1 microg/L for cocaine and its metabolite benzoylecgonine, 80-200 ng/L for morphine, 10 ng/L for 6-acetylmorphine, 60-90 ng/L for 11-nor-9-carboxy-Delta9-tetrahydrocannabinol, 10-90 ng/L for methadone and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine, and lower than 20 ng/L for amphetamines. As previously reported for cocaine, this method could be useful to estimate and monitor drug consumption in the population in real time, helping social scientists and authorities to combat drug abuse.     

Optimal power flow application issues in the Pool paradigm

This paper focuses on the application of the Optimal Power Flow (OPF) to competitive markets. Since the OPF is a central decision-making tool its application to the more decentralized decision-making in the competitive electricity markets requires considerable care. There are some intrinsic challenges associated with the effective OPF application in the competitive environment due to the inherent characteristics of the OPF formulation. Two such characteristics are the flatness of the optimum surface and the consequent continuum associated with the optimum. In addition to these OPF structural characteristics, the level of authority vested in the central decision-making entity has major ramifications. These factors have wide ranging economic impacts, whose implications are very pronounced due to the fact that, unlike in the old vertically integrated utility environment, various market players are affected differently. The effects include price volatility, financial health of various players and the integrity of the market itself. We apply appropriate metrics to evaluate market efficiency and how the various players fare. We study the impacts of OPF applications in the Pool paradigm, with both supply and demand side explicitly modeled, and provide extensive numerical results on systems based on IEEE 30-bus and 118-bus networks. The results show the variability of nodal prices and the skew possible in different ‘optimal’ allocations among competing suppliers. Such variability in the results may lead to serious disputes among the players and the central decision-making authority. Directions for future research are discussed.