Finitely cotilting modules

Over an arbitrary ring, we consider cotilting modules endowed with some finiteness conditions. We show that they correspond to pairs of dualities between certain cat-egories consisting of finitely presented modules. This extends the Cotilting Theorem proved by Colby for the noetherian case. The relationship with the cotilting modules studied by Colpi, D'Este, Tonolo and Trlifaj is also discuss.d.     

Simple Analytical Method for the Determination of Paclitaxel (Taxol ® ) Levels in Human Plasma

Paclitaxel has been widely used for tumor chemotherapy in recent years and it would be useful to assess occupational exposure to the drug, if only to confirm that the procedures and measures for prevention and protection applied in health care structures are effective against this kind of risk. This study is to establish a simple, robust analytical method for routine use in biological monitoring of health workers exposed to taxanes, and extendable to patients receiving these drugs. HPLC equipped with a diode array detector was used. The assay was validated. Intra- and inter-day accuracy and reproducibility were good. Recovery of paclitaxel spiked in drug-free plasma was higher than 87% with SPE using extract-clean normal phase cyanopropyl silica cartridges for plasma clean-up. The calibration curve was linear in the range 10–500 ng mL^?1. The method was applied to plasma samples of nurses occupationally exposed to paclitaxel. The experimental analytical method performed well, detecting paclitaxel in plasma at a concentrations down to 10 ng mL^?1. This straightforward method for analytical determination of paclitaxel in human plasma is rapid and can measure up to 36 plasma samples per day. It uses more economical equipment than other methods proposed in the literature and its validation parameters are highly satisfactory.     

Electrodeposition of nickel/SiC composites in the presence of cetyltrimethylammonium bromide

Electrodeposition of SiC particles with nickel matrix in the presence of cetyltrimethylammonium bromide (CTAB) at two current densities was carried out. Surface chemistry (amount of acidic and basic superficial groups, surface charge, Ni²⁺ and Br⁻ adsorption) of the SiC powder in the presence of various CTAB amounts (0-1.1 mM) was studied. Cationic surfactant inhibited adsorption of cations and enhanced adsorption of anions on the positive charged carbide surface, but Br⁻/Ni²⁺ molar ratios for adsorbed ions were higher than in the bath. It was attributed to the CTAB adsorption realized predominantly by hydrophobic interactions between aliphatic chain of the molecule and SiC surface with the positive head group of CTA⁺ pointed toward the bulk solution. Increased SiC incorporation to the composite coating with CTAB addition was observed. Correlation between current efficiency and Br⁻/Ni²⁺ molar ratios for ions adsorbed on SiC was found. The influence of CTAB concentration on the cathodic polarization curves was also determined. Structure of the composite coatings was studied by microscopic observations. Microhardness of the fine-grained metal matrix composites was also determined.     

4,6-Dinitrobenzo[c]isothiazole: synthesis and 1,3-dipolar cycloaddition to azomethine ylide

1,3-Dipolar cycloaddition of 4,6-dinitrobenzo[c]isothiazole to (N-methyl-N-methylideneammonio)methanide (2 equiv.) gives 5,8-dimethyl-3b,6b-dinitrodecahydroisothiazolo[3,4-e]pyrrolo[3,4-g]isoindole, whose structure was confirmed by X-ray diffraction analysis.     

LC Determination of the Skin Exposure to Oxamyl on Greenhouse Workers and Comparison Between DAD and MS–MS Detection

An LC–DAD method was developed to determine residues of oxamyl on greenhouse workers’ skin. The wipe test was used to obtain samples from hands, forearms, neck and gloves of workers taking cactus cuttings 48 h after pesticide treatment. It was validated in a concentration range 50–5,000 ng mL^?1. The results on six workers and ten office employees indicated significant differences particularly in the hand samples. To avoid the overestimation owing to an interfering substance we proceeded to confirm these findings with LC–MS–MS, which found the pesticide only on the surface of the workers’ gloves, proving that there was indeed some UV interference.     

Pesticide extraction from table grapes and plums using ionic liquid based dispersive liquid–liquid microextraction

Room temperature ionic liquids (RTILs) have been used as extraction solvents in dispersive liquid–liquid microextraction (DLLME) for the determination of eight multi-class pesticides (i.e. thiophanate-methyl, carbofuran, carbaryl, tebuconazole, iprodione, oxyfluorfen, hexythiazox, and fenazaquin) in table grapes and plums. The developed method involves the combination of DLLME and high-performance liquid chromatography with diode array detection. Samples were first homogenized and extracted with acetonitrile. After evaporation and reconstitution of the extract in water containing sodium chloride, a quick DLLME procedure that used the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) and methanol was developed. The RTIL dissolved in a very small volume of acetonitrile was directed injected in the chromatographic system. The comparison between the calibration curves obtained from standards and from spiked sample extracts (matrix-matched calibration) showed the existence of a strong matrix effect for most of the analyzed pesticides. A recovery study was also developed with five consecutive extractions of the two types of fruits spiked at three concentration levels. Mean recovery values were in the range of 72–100% for table grapes and 66–105% for plum samples (except for thiophanate-methyl and carbofuran, which were 64–75% and 58–66%, respectively). Limits of detection (LODs) were in the range 0.651–5.44 μg/kg for table grapes and 0.902–6.33 μg/kg for plums, representing LODs below the maximum residue limits (MRLs) established by the European Union in these fruits. The potential of the method was demonstrated by analyzing 12 commercial fruit samples (six of each type).     

Gold nanoclusters protected by conformationally constrained peptides

The preparation and properties of a series of gold nanoclusters protected by thiolated peptides based on the alpha-aminoisobutyric acid (Aib) unit are described. The peptides were devised to form 0-3 C=O...H-N intramolecular hydrogen bonds, as required by their 3(10)-helical structure. The monolayer-protected clusters (MPCs) were prepared, using a modified version of the two-phase Brust-Schiffrin preparation, and fully characterized with (1)H NMR spectrometry, IR and UV-vis absorption spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The MPCs were obtained with core diameters in the range of 1.1-2.3 nm, depending on the reaction conditions. Structured peptides formed smaller clusters. The smallest MPC obtained is in agreement with the average formula Au(38)Pep(18). The results showed that the chemical integrity of the peptide is maintained upon monolayer formation and that the average number of peptide ligands per gold cluster is typically 75-85% the value calculated for alkanethiolate MPCs of similar sizes. The IR and NMR spectra indicated that in the monolayer the peptides are involved in both intra- and interligand C=O...H-N hydrogen bonds.     

Pesticides analysis by liquid chromatography and capillary electrophoresis

Nowadays, a wide range of pesticides are used in agricultural production, and their monitoring in samples of environmental and alimentary interest is of extreme importance to ensure, among others, the safety of consumption of foods. The aim of this work is to provide updated information about the major developments in CE and HPLC in pesticide analysis, covering relevant publications between 2004 and early 2006. The use of different sample pretreatment steps to provide a suitable extraction of these compounds from the different matrices as well as to increase the sensitivity of the determination is also discussed.