Effect of the sulfide group on photopolymerization kinetics of di(meth)acrylates

Summary The photopolymerization of four analogous monomers: 2,2-thiobisethanol diacrylate and its dimethacrylate plus 2,2-oxybisethanol diacrylate and its dimethacrylate has been studied by isothermal differential scanning calorimetry (DSC) over a range of incident light intensities. The results obtained prove that the sulfide group accelerates polymerization both in the presence and absence of oxygen and enhances the conversion. The light intensity exponents for each monomer were determined and the mechanism of termination was discussed. The intensity exponents of sulfur-containing monomers are lower than their corresponding oxygen analogues, pointing to a greater participation of the bimolecular termination during their polymerization.     

Structural Insights into Conformation Differences between DNA/TNA and RNA/TNA Chimeric Duplexes

Threose nucleic acid (TNA) is an artificial genetic polymer capable of heredity and evolution, and is studied in the context of RNA chemical etiology. It has a four‐carbon threose backbone in place of the five‐carbon ribose of natural nucleic acids, yet forms stable antiparallel complementary Watson–Crick homoduplexes and heteroduplexes with DNA and RNA. TNA base‐pairs more favorably with RNA than with DNA but the reason is unknown. Here, we employed NMR, ITC, UV, and CD to probe the structural and dynamic properties of heteroduplexes of RNA/TNA and DNA/TNA. The results indicate that TNA templates the structure of heteroduplexes, thereby forcing an A‐like helical geometry. NMR measurement of kinetic and thermodynamic parameters for individual base pair opening events reveal unexpected asymmetric “breathing” fluctuations of the DNA/TNA helix. The results suggest that DNA is unable to fully adapt to the conformational constraints of the rigid TNA backbone and that nucleic acid breathing dynamics are determined from both backbone and base contributions.     

Does an expert-based evaluation allow us to go beyond the Impact Factor? Experiences from building a ranking of national journals in Poland

The article discusses the process of textually mediated communication in science and proposes an approach that complements citation analysis. Namely, it addresses the question of how the author’s text is read by the reader and whether the reader interprets the text in the same manner as the author. Fifty-seven scholarly contributions (articles, book chapters and book reviews), written by three social scientists, were content analyzed with the help of the QDA Miner and WordStat computer programs. The outcomes of the qualitative coding were compared with the outcomes of the analysis of word co-occurrences and the outcomes of the analysis on the basis of a dictionary based on substitution. Our findings suggest that texts have plural interpretations. Depending on the reading context, either the author’s or the reader’s perspective prevails. Also, both the author and the reader may read the text in a either deep or perfunctory manner. Deep reading necessitates spending significant time and cognitive resources.     

Gold Nanoparticles Thin Films with Thermo‐ and Photoresponsive Plasmonic Properties Realized with Liquid‐Crystalline Ligands

Robust synthesis of large‐scale self‐assembled nanostructures with long‐range organization and a prominent response to external stimuli is critical to their application in functional plasmonics. Here, the first example of a material made of liquid crystalline nanoparticles which exhibits UV‐light responsive surface plasmon resonance in a condensed state is presented. To obtain the material, metal cores are grafted with two types of organic ligands. A promesogenic derivative softens the system and induces rich liquid crystal phase polymorphism. Second, an azobenzene derivative endows nanoparticles with photoresponsive properties. It is shown that nanoparticles covered with a mixture of these ligands assemble into long‐range ordered structures which exhibit a novel dual‐responsivity. The structure and plasmonic properties of the assemblies can be controlled by a change in temperature as well as by UV‐light irradiation. These results present an efficient way to obtain bulk quantities of self‐assembled nanostructured materials with stability that is unattainable by alternative methods such as matrix‐assisted or DNA‐mediated organization.     

The influence of the initial acidity of HFER on the status of Co species and catalytic performance of CoFER and InCoFER in CH4-SCR-NO

The role of the initial acidity of ferrierite type zeolite on the status of cobalt and the catalytic activity of CoFER and InCoFER was investigated. Two FER zeolites were used: NH₄FER without any pretreatment (FER-1) and the same zeolite, dehydroxylated at 825 K (FER-2). Dehydroxylation removed most of the Si–OH–Al groups, therefore the resulting zeolite revealed practically no ion exchange capacity. The status of cobalt was followed by IR spectroscopy with probe molecules: CO (a probe for Co²⁺) and NO (a probe for Co³⁺). The introduction of cobalt by solid-state ion exchange produced divalent cobalt in exchange positions and in the form of oxide-like clusters, their respective concentration was determined by quantitative IR experiments of CO sorption. The amount of Co³⁺, present in CoFER-1 and InCoFER-1, was also determined. All these forms of cobalt were practically absent from CoFER-2 and InCoFER-2. The NO conversion and selectivity to N₂ of CoFER-2 in CH₄-SCR-NO was poor, indicating the essential role of the initial acidity of the ferrierite matrix on the formation of catalytically active Co species. The introduction of indium into CoFER only slightly increased the NO conversion and shifted the reaction path from NO₂ towards N₂ formation for FER-1, while greatly improved the catalytic performance of the FER-2 series.     

Inner-tube chirality determination for double-walled carbon nanotubes by scanning tunneling microscopy

Evidence for modified electronic structure in double-walled carbon nanotubes with respect to their individual inner and outer constituent single-walled nanotubes is provided by scanning tunneling microscopy and spectroscopy experiments. The contribution originating from the inner tube to the local density of states of the double-walled system was identified in agreement with previous theoretical calculations. Consequently, the chiral index for the inner tube was extracted based on the additional van Hove singularities present in the experimental tunneling spectra.     

Atmospheric correction for NO2 absorption in retrieving water-leaving reflectances from the SeaWiFS and MODIS measurements

The absorption by atmospheric nitrogen dioxide (NO2) gas in the visible has been traditionally neglected in the retrieval of oceanic parameters from satellite measurements. Recent measurements of NO2 from spaceborne sensors show that over the Eastern United States the NO2 column amount often exceeds 1 Dobson Unit (approximately 2.69x10(16) molecules/cm2). Our radiative transfer sensitivity calculations show that under high NO2 conditions (approximately 1x10(16) molecules/cm2) the error in top-of-atmosphere (TOA) reflectance in the blue channels of the sea-viewing wide field-of-view sensor (SeaWiFS) and moderate-resolution imaging spectroradiometer (MODIS) sensors is approximately 1%. This translates into approximately 10% error in water-leaving radiance for clear waters and to higher values (>20%) in the coastal areas. We have developed an atmospheric-correction algorithm that allows an accurate retrieval of normalized water-leaving radiances (nLws) in the presence of NO2 in the atmosphere. The application of the algorithm to 52 MODIS scenes over the Chesapeake Bay area show a decrease in the frequency of negative nLw estimates in the 412 nm band and an increase in the value of nLws in the same band. For the particular scene reported in this paper, the mean value of nLws in the 412 nm band increased by 17%, which is significant, because for the MODIS sensor the error in nLws attributable to the digitization error in the observed TOA reflectance over case 2 waters is approximately 2.5%.     

Influence of inorganic ions on MTBE degradation by Fenton's reagent

The effect of selected inorganic anions on the effectiveness of the Fenton advanced oxidative treatment of waters contaminated with methyl t-butyl ether (MTBE) was examined. With respect to the chloride or phosphate ions used, inhibition of oxidation was clearly in evidence, whereas addition of sulfates or perchlorates influenced these rates to a much smaller extent. Anions suppress MTBE decomposition in the following sequence: ClO4- 相似文献   

Dissecting the role of dolichol in cell wall assembly in the yeast mutants impaired in early glycosylation reactions

Evidence is presented that temperature-sensitive Saccharomyces cerevisiae mutants, impaired in dolichol kinase (Sec59p) or dolichyl phosphate mannose synthase (Dpm1p) activity have an aberrant cell wall composition and ultrastructure. The mutants were oversensitive to Calcofluor white, an agent interacting with the cell wall chitin. In accordance with this, chemical analysis of the cell wall alkali-insoluble fraction indicated an increased amount of chitin and changes in the quantity of beta1,6- and beta1,3-glucan in sec59-1 and dpm1-6 mutants. In order to unravel the link between the formation of dolichyl phosphate and dolichyl phosphate mannose and the cell wall assembly, we screened a yeast genomic library for a multicopy suppressors of the thermosensitive phenotype. The RER2 and SRT1 genes, encoding cis-prenyltransferases, were isolated. In addition, the ROT1 gene, encoding protein involved in beta1,6-glucan synthesis (Machi et al., 2004) and protein folding (Takeuchi et al., 2006) acted as a multicopy suppressor of the temperature-sensitive phenotype of the sec59-1 mutant. The cell wall of the mutants and of mutants bearing the multicopy suppressors was analysed for carbohydrate and mannoprotein content. We also examined the glycosylation status of the plasma membrane protein Gas1p, a beta1,3-glucan elongase, and the degree of phosphorylation of the Mpk1/Slt2 protein, involved in the cell wall integrity pathway.