Porous SiOC monoliths with catalytic activity by in situ formation of Ni nanoparticles in solution-based freeze casting

Micro- and macroporous monoliths with in situ formed nickel nanoparticles were prepared for the first time by the combination of solution-based freeze casting and preceramic polymers (methyl polysiloxane). This one-step process results in macroporous monoliths composed of microporous and catalytic active nickel-containing polymer-derived ceramic. Four different complexing and cross-linking siloxanes with amino functionality were screened for their ability to create small nickel particles. TEM analysis confirmed 3-aminopropyltriethoxysilane being most efficient. High BET-specific surface areas of 344-461 m² g⁻¹ were achieved. Increased ratio of complexing groups to nickel improves the dispersion of nickel to (3.61 ± 1.49) nm. The nickel size dependence of conversion (maximum 0.49) and CH₄ selectivity (maximum 0.74) in CO₂ methanation emphasizes the importance of controlling the nickel size. The hydrophobic surface characteristic is hypothesized to be the main reason polymer-derived catalysts having better catalytic activity compared with nickel-impregnated silica. The promising catalytic activity combined with the versatile freeze casting process can prospectively address heat- and mass-transfer considerations in heterogeneous monolith catalysis.     

Measuring automatic retrieval.

A variety of procedures have been used to assess automatic retrieval effects on memory, including implicit memory tests and the process dissociation approach. Theoretical concerns with each are summarized prior to describing a procedure for evaluating automatic retrieval that is based on retrieval speed. Specifically, in a speeded implicit task, participants were encouraged to complete word stems using strictly automatic retrieval by presenting several practice test trials that did not allow responding based on previously studied items, and by encouraging speed of responding. This speeded implicit task was compared with a condition in which conscious retrieval of studied information was not possible and a condition in which conscious retrieval was required, providing converging evidence to support the hypothesis that the speeded implicit procedure can yield pure estimates of automatic retrieval. Furthermore, evidence from a standard implicit memory task yielded comparable data that suggests that participants engaged automatic retrieval processes on this task also. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Binding of metal cations to chemically modified wool and antimicrobial properties of the wool–metal complexes

Wool was modified by treatment with tannic acid (TA) or by acylation with ethylenediaminetetraacetic (EDTA) dianhydride. Kinetics of modification with TA and acylation with EDTA–dianhydride was investigated as a function of the reaction time. Wool displayed a higher breaking load and lower elongation at break as the degree of acylation increased. The absorption of metal cations (Ag⁺, Cu²⁺) by untreated and chemically modified wool was studied as a function of the kind of modifying agent, weight gain, and pH of the metal solution. Absorption of Ag⁺ and Cu²⁺ at alkaline pH increased with increasing weight gain of both TA and EDTA–dianhydride. The absorption of metal cations by untreated and TA‐treated wool below pH 7 was negligible. Acylation with EDTA–dianhydride enabled wool to absorb and bind significant amounts of metal cations at acidic and neutral pHs. The wool–Ag complexes exhibited low levels of metal desorption at acidic pH, irrespective of chemical modification. Higher levels of metal desorption were shown by wool–Cu and wool–EDTA–Cu complexes. Wool–Ag complexes exhibited prominent antimicrobial activity against Cornebacterium and E. coli. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3513–3519, 2001     

Synthesis and Evaluation of N‐Phenylpyrrolamides as DNA Gyrase B Inhibitors

ATP‐competitive inhibitors of DNA gyrase and topoisomerase IV are among the most interesting classes of antibacterial drugs that are unrepresented in the antibacterial pipeline. We developed 32 new N‐phenylpyrrolamides and evaluated them against DNA gyrase and topoisomerase IV from E. coli and Staphylococcus aureus. Antibacterial activities were studied against Gram‐positive and Gram‐negative bacterial strains. The most potent compound displayed an IC₅₀ of 47 nm against E. coli DNA gyrase, and a minimum inhibitory concentration (MIC) of 12.5 μm against the Gram‐positive Enterococcus faecalis. Some compounds displayed good antibacterial activities against an efflux‐pump‐deficient E. coli strain (MIC=6.25 μm ) and against wild‐type E. coli in the presence of efflux pump inhibitor PAβN (MIC=3.13 μm ). Here we describe new findings regarding the structure–activity relationships of N‐phenylpyrrolamide DNA gyrase B inhibitors and investigate the factors that are important for the antibacterial activity of this class of compounds.     

Chemical Modification of Terephthalate Polyesters by Reaction with Bis(hydroxyethyl ether) of Bisphenol A

Summary: Copolyesters of terephthalic acid with bis(hydroxyethyl ether) of bisphenol A (BHEEB) in different molar ratios have been synthesized by reactive blending from terephthalate polyesters and by melt polycondensation from the monomers. By this way, bisphenol A groups were inserted in the polyester chains with the aim to obtain polyesters with improved mechanical properties. The insertion of the BHEEB into the polyester backbone is quantitative and does not give rise to side reactions. These copolyesters can be obtained by the chemical recycling of commercial polymers; indeed BHEEB can be synthesized by chemical recycling of bisphenol A polycarbonate and may be incorporated in the polyester by reactive blending with recycled terephthalate polyesters. A new method for BHEEB synthesis by chemical recycling of PC is also presented.

Glass transition temperature (T_g) as function of BHEEB content for copolyesters prepared by reactive blending BHEEB with terephthalate polyesters.     

Synthesis and characterization of imidazolium telechelic poly(butylene terephthalate) for antimicrobial applications

Poly(butylene terephthalate) ionomers with imidazolium groups selectively located as end-groups (telechelic) have been prepared by melt polycondensation adding a hydroxyl derivatized imidazolium salt at the beginning of the polymerization process. The design of the chemical structure of the imidazolium salt is of fundamental importance in order to achieve the synthesis of ionomers with good thermo-mechanical properties. The final ionomers present high molecular weight, good color, transparency and thermal stability. Imidazolium ionomers present good antimicrobial (AM) properties comparable with those of commercial AM agents. The incorporation of the ionic groups in the polymer chain prevents their migration during use and therefore the antimicrobial activity can be preserved for longer time.     

New graphic representation of structural parameters of proteins

A computer program is described that is designed to make the visual inspection of classical plots of protein properties (e.g. hydrophobicity, volume, etc.) as a function of sequence easier. An algorithm written in BASIC language has been used in order to generate a pseudo-tridimensional representation of the desired protein property. The data utilized by the program are arithmetic averages of the selected parameter obtained by using a five-residue window as a shuttle along the given amino acid sequence.     

Mercury adsorption by montmorillonite and vermiculite: a combined XRD, TG-MS, and EXAFS study

Synchrotron-based extended X-ray absorption fine structure spectroscopy (EXAFS), X-ray diffraction at room and high temperature, thermal analyses combined with mass spectrometry of evolved gas, and chemical analyses contributed to assess the influence of mercury on montmorillonite and vermiculite layers.The adsorbed Hg amount was higher for montmorillonite (Hg=37.7 meq/100 g) than for vermiculite (Hg=28.0 meq/100 g). The basal spacing for the Hg treated samples was 15.2 (montmorillonite) and 14.5 Å (vermiculite). Thermal and evolved gas spectrometry analyses suggest that Hg was released at T230 °C and at 600 °C for montmorillonite, but at 550, 800 and 860 °C for vermiculite.The effect of temperature on Hg release is also apparent when the basal spacing at 230 °C for montmorillonite (d₀₀₁=10.3 Å) is compared to that for vermiculite (d₀₀₁=11.8 Å).EXAFS analyses provide qualitative evidence that oxygen atoms occupy the first coordination shell of Hg in both clay minerals. The best fit between observed and calculated spectra is obtained when montroydite is assumed as a reference model compound.     

Identification of a beta-lactoglobulin lactosylation site

In various animal models of cerebral hypoxia-ischemia, it is not clear whether neuronal apoptosis results from hypoxia alone or whether other factors mediate this process. We hypothesized that (1) hypoxia alone can induce neuronal apoptosis, (2) hypoxic severity alters the time course of neuronal apoptosis, (3) hypoxia increases neuronal p53, and this increase in p53 is critical for neuronal apoptosis. Embryonic neocortical neurons cultured for 7-10 days were placed in an incubator with levels set at 0.1%, 1%, and 3% O2 and were removed at 24-h intervals for study. Under all hypoxic conditions, observed changes in cellular morphology and DNA fragmentation, detected by the TUNEL method and gel electrophoresis, were consistent with apoptosis. These alterations were seen after a shorter period with increasing hypoxic severity. Immunoblot analysis revealed an increase in p53 protein in hypoxia-exposed neurons. Analysis of immunofluorescence-stained neurons revealed increases in p53 with increased duration and severity of hypoxia. Antisense oligonucleotides for p53 significantly increased the number of surviving neurons during hypoxic exposure. We conclude that hypoxia-induced neuronal apoptosis is, in part, a p53-dependent process whose time course is influenced by hypoxic severity and duration.