Preparation and characterization of thin films of NbO2

Thin films of NbO₂, with thicknesses ranging from 1000 to 20 000 Å, were prepared by r.f. sputtering powder targets of NbO₂ in a reducing atmosphere of 90vol.%Ar–10vol.%H. Transmission electron microscopy and X-ray diffraction studies of self-supported films indicate that the as-deposited material was amorphous. Compositional analysis, derived from interpretation of Rutherford back-scattering spectra and neutron activation analysis of films deposited onto vitreous carbon substrates, indicates a high degree of stoichiometry. The variation in the electrical conductivity with the rate of deposition is reported, and also a comparison is made between the electrical conductivity of the amorphous and crystalline phases of films of NbO₂.     

Environmental exposure assessment of fluoroquinolone antibacterial agents from sewage to soil

The behavior of fluoroquinolone antibacterial agents (FQs) during mechanical-biological wastewater treatment was studied by mass flow analysis. In addition, the fate of FQs in agricultural soils after sludge application was investigated. Concentrations of FQs in filtered wastewater (raw sewage, primary, secondary, and tertiary effluents) were determined using solid-phase extraction with mixed phase cation exchange disk cartridges and reversed-phase liquid chromatography with fluorescence detection. FQs in suspended solids, sewage sludge (raw, excess, and anaerobically digested sludge), and sludge-treated soils were determined as described for the aqueous samples but preceded by accelerated solvent extraction. Wastewater treatment resulted in a reduction of the FQ mass flow of 88-92%, mainly due to sorption on sewage sludge. A sludge-wastewater partition coefficient (log Kd approximately 4) was calculated in the activated sludge reactors with a hydraulic residence time of about 8 h. No significant removal of FQs occurred under methanogenic conditions of the sludge digesters. These results suggest sewage sludge as the main reservoir of FQ residues and outline the importance of sludge management strategies to determine whether most of the human-excreted FQs enter the environment. Field experiments of sludge-application to agricultural land confirmed the long-term persistence of trace amounts of FQs in sludge-treated soils and indicated a limited mobility of FQs into the subsoil.     

Structures and stabilities of small DNA dumbbells with Watson-Crick and Hoogsteen base pairs

The structures and stabilities of cyclic DNA octamers of different sequences have been studied by NMR and CD spectroscopy and by restrained molecular dynamics. At low oligonucleotide concentrations, some of these molecules form stable monomeric structures consisting of a short stem of two base pairs connected by two mini-loops of two residues. To our knowledge, these dumbbell-like structures are the smallest observed to date. The relative stabilities of these cyclic dumbbells have been established by studying their melting transitions. Dumbbells made up purely of GC stems are more stable than those consisting purely of AT base pairs. The order of the base pairs closing the loops also has an important effect on the stabilities of these structures. The NMR data indicate that there are significant differences between the solution structures of dumbbells with G-C base pairs in the stem compared to those with A-T base pairs. In the case of dumbbells with G-C base pairs, the residues in the stem form a short segment of a BDNA helix stabilized by two Watson-Crick base pairs. In contrast, in the case of d, the stem is formed by two A-T base pairs with the glycosidic angles of the adenine bases in a syn conformation, most probably forming Hoogsteen base pairs. Although the conformations of the loop residues are not very well defined, the thymine residues at the first position of the loop are observed to fold back into the minor groove of the stem.     

Comparison of three coupled gas chromatographic detectors (MS, MIP-AES, ICP-TOFMS) for organolead speciation analysis

An automatic unit for the screening of rainwater is used for the determination of organolead compounds using different detectors coupled to a gas chromatograph. A systematic overview is given of the advantages and disadvantages of several detectors (electron ionization mass spectrometry, EI-MS; microwave induced plasma atomic emission spectrometry, MIP-AES; and inductively coupled plasma time-of-flight mass spectrometry, ICP-TOFMS, for the speciation of organolead compounds on the basis of sensitivity, selectivity and reliability. C60 fullerene and RP-C18 were used as sorbent materials for these compounds. The primary assets of the fullerene sorbent, as compared to C18 sorbent, are high sensitivity and selectivity resulting from efficient adsorption due to large surface area and interstitial volume. Among the detection systems, GC/ ICP-TOFMS is the most sensitive, with absolute detection limits of approximately 15 fg of organolead compounds (as lead) using 5-mL sample volumes. Except for diethyllead, similar sensitivities were obtained by MIP-AES. GC/MS is intrinsically the most specific option, because the species are detected directly from molecular information. The precision is similar for all detectors. The screening of rainwater from different locations showed that samples collected in countries in which leaded gasolines are now banned contain organolead species at concentrations below 2 pg/ mL, levels that can be detected only for sample volumes of 25 mL and using MIP-AES or ICP-TOFMS as detectors, their determination being impossible by GC/MS.     

Targeting RNA with small-molecule drugs: therapeutic promise and chemical challenges

Researchers' increasing awareness of the essential role played by RNA in many biological processes and in the progression of disease makes the discovery of new RNA targets an emerging field in drug discovery. Since most existing pharmacologically active compounds bind proteins, RNA provides nearly untapped opportunities for pharmacological development. The elucidation of the structure of the ribosome and other cellular and viral RNA motifs creates the opportunity for discovering new drug-like compounds that inhibit RNA function. However, further advances in understanding the chemistry and structure of RNA recognition are needed before these promises are fulfilled.     

Chemoenzymatic synthesis of biotinylated nucleotide sugars as substrates for glycosyltransferases

The enzymatic oxidation of uridine 5'-diphospho-alpha-D-galactose (UDP-Gal) and uridine 5'-diphospho-N-acetyl-alpha-D-galactosamine (UDP-GalNAc) with galactose oxidase was combined with a chemical biotinylation step involving biotin-epsilon-amidocaproylhydrazide in a one-pot synthesis. The novel nucleotide sugar derivatives uridine 5'-diphospho-6-biotin-epsilon-amidocaproylhydrazino-alpha-D-galactose (UDP-6-biotinyl-Gal) and uridine 5'-diphospho-6-biotin-epsilon-amidocaproylhydrazino-N-acetyl-alpha-D-galactosamine (UDP-6-biotinyl-GalNAc) were synthesized on a 100-mg scale and characterized by mass spectrometry (fast atom bombardment and matrix-assisted laser desorption/ionization time of flight) and one/two dimensional NMR spectroscopy. It could be demonstrated for the first time, by use of UDP-6-biotinyl-Gal as a donor substrate, that the human recombinant galactosyltransferases beta3Gal-T5, beta4Gal-T1, and beta4Gal-T4 mediate biotinylation of the neoglycoconjugate bovine serum albumin-p-aminophenyl N-acetyl-beta-D-glucosaminide (BSA-(GlcNAc)17) and ovalbumin. The detection of the biotin tag transferred by beta3Gal-T5 onto BSA-(GlcNAc)17 with streptavidin-enzyme conjugates gave detection limits of 150 pmol of tagged GlcNAc in a Western blot analysis and 1 pmol of tagged GlcNAc in a microtiter plate assay. The degree of Gal-biotin tag transfer onto agalactosylated hybrid N-glycans present at the single glycosylation site of ovalbumin was dependent on the Gal-T used (either beta3Gal-T5, beta4Gal-T4, or beta4Gal-T1), which indicates that the acceptor specificity may direct the transfer of the Gal-biotin tag. The potential of this biotinylated UDP-Gal as a novel donor substrate for human galactosyltransferases lies in the targeting of distinct acceptor structures, for example, under-galactosylated glycoconjugates, which are related to diseases, or in the quality control of glycosylation of recombinant and native glycoproteins.     

Chemical-Enhanced Washing for Remediation of Soils Contaminated with Marine Diesel Fuel in the Presence/Absence of Pb

The effects of the operating conditions, the initial concentrations of marine diesel fuel (MDF) and the coexisting Pb in the soil, and the ethylene diamine tetra acetic salt (EDTA) in solution on MDF removal by sodium dodecyl sulfate (SDS) washing were extensively investigated with the aim of optimizing the process parameters and determining the MDF removal efficiency by SDS under different contamination conditions. The experimental results from batch tests indicated that the majority of MDF was removed by SDS in the first 2?h, and its optimal pH was nearly neutral. Increasing the SDS concentration linearly increased the MDF removal efficiency. At a given SDS concentration, the removal efficiency was dependent on the existing forms of MDF in soils, and the free phase of MDF was found to be more easily removed than the adsorbed phase. MDF removal by SDS was significantly reduced by the coexisting Pb in soils, which likely forms a complexation with SDS and thereby enhances the partitioning of MDF in the soil by the re-adsorption of released MDF onto the hydrophobic tails of the adsorbed SDS. EDTA alone, or with SDS, could remove MDF, but the remaining MDF in the contaminated soil after EDTA washing became more difficult to be removed by SDS. Therefore, the EDTA washing followed by SDS washing is not recommended for MDF removal.     

The efficiency of sampling very high resolution images for area estimation in the European Union

Very high resolution (VHR) images are a valuable information source to estimate land cover area and land cover change. When full coverage of a region with VHR images is not affordable, a sample of images can be considered. Square grids provide a practical sampling frame for VHR images. When using a land cover map as pseudo-truth, the sampling variance is easily assessed but may be overestimated if the land cover map has a coarse resolution. To estimate the potential sampling variance of a cluster sampling scheme, we propose a method based on intra-cluster correlation (ICC) computed from a correlogram. The ‘equivalent number of points’ is a useful indicator to quantify cost-efficiency of sites of a given size. We obtained poor efficiency results for area estimation of major land cover types in the European Union (EU) with a sample of 10 km?×?10 km sites, but results are more encouraging for classes with a more scattered layout or for land cover change.     

Vocal learning in the grey parrot (Psittacus erithacus): Effects of species identity and number of trainers.

Grey parrots (Psittacus erithacus) learn referential English labels when they view and interact with 2 humans who model vocal labeling and who demonstrate referentiality and functionality of a label (I. M. Pepperberg, 1990a). To test if both trainers are necessary, the authors contrasted 2-trainer modeling with training by 1 human who presented targeted labels to a bird in concert with appropriate items, who asked questions, and who would reward attempts at the label with the item. The bird was also tutored by either 1 or 2 interactive humans in conjunction with a conspecific who already used referential labels. Referential labels were learned from multiple live tutors but not a single trainer. Presence of a conspecific enhanced learning compared with single-trainer sessions but did not affect acquisition in 2-human sessions. Specific aspects of paired tutoring seem critical for acquiring referential vocal labels. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measuring university–industry collaboration in a regional innovation system

Studies of university–industry collaboration remain subject to important limitations due to the shortage of empirical data and a lack of consistency in that obtained to date. This article puts into practice a set of universities Third Mission indicators in a regional innovation system. Selected indicators previously compiled from literature were reorganized and pre-tested. We have undertaken two face-to-face surveys of 737 firms and 765 heads of research teams, respectively. The results test the validation of indicators and provide a complex map of university–industry linkages as well as some observations on the flexibility needed to address this issue.