Photo-vulcanization using thiol-ene chemistry: Film formation,morphology and network characteristics of UV crosslinked rubber latices

The photo-vulcanization with versatile thiol-ene chemistry represents an innovative approach to crosslink diene-rubber materials both in latex and in solid film state. In this work, the structure of elastomer-based thiol-ene networks and the morphology after film formation are studied in detail using electron microscopic techniques, atomic force microscopy and multiple-quantum solid-state NMR spectroscopy. Additionally, film formation properties and corresponding macroscopic properties of photo-vulcanized natural rubber (NR) latex and its synthetic counterpart, isoprene rubber (IR) latex, are determined in dependence on the curing procedure (pre- and post-vulcanization). The results reveal that thiol-ene cured elastomers comprise homogenously distributed crosslinks with a low amount of short chain defects. Whilst photochemically pre-cured NR latex particles provide coherent films, the film formation and mechanical properties of IR are strongly governed by the crosslink density of the latex particles. In film state, photo-vulcanization promotes narrow crosslink distributions and excellent tensile properties of both NR and IR.     

连二硫酸金属盐和连二硫酸在电镀和金属精饰领域的应用

在电镀溶液中使用连二硫酸和连二硫酸金属盐作为可溶性金属离子和电解质的来源具有潜在的应用。为有助于具有创新精神的配方研究者考虑采用诸如连二硫酸这种新型电解质,文章总结了连二硫酸盐电镀液近期的发展,用实例说明了连二硫酸盐在电镀液中的应用。众所周知,连二硫酸在强酸溶液中发生歧化反应,但这并不妨碍在适宜的条件下使用连二硫酸盐以及连二硫酸。(由于篇幅限制,有关连二硫酸及连二硫酸金属盐的化学性质、稳定性、制备方法等补充材料及学术综述、研究报告所涉及的参考文献均在本刊网站上详细全文发表,见http:／／www．plating．org／web／20060901．mht。)     

Gemini and Bicephalous Surfactants: A Review on Their Synthesis,Micelle Formation,and Uses

The use of surfactants in polymerization reactions is particularly important, mainly in emulsion polymerizations. Further, micelles from biocompatible surfactants find use in pharmaceutical dosage forms. This paper reviews recent developments in the synthesis of novel gemini and bicephalous surfactants, micelle formation, and their applications in polymer and nanoparticle synthesis, oil recovery, catalysis, corrosion, protein binding, and biomedical area, particularly in drug delivery.     

Bifunctional Opioid/Melanocortin Peptidomimetics for Use in Neuropathic Pain: Variation in the Type and Length of the Linker Connecting the Two Pharmacophores

Based on the mechanism of neuropathic pain induction, a new type of bifunctional hybrid peptidomimetics was obtained for potential use in this type of pain. Hybrids consist of two types of pharmacophores that are connected by different types of linkers. The first pharmacophore is an opioid agonist, and the second pharmacophore is an antagonist of the pronociceptive system, i.e., an antagonist of the melanocortin-4 receptor. The results of tests in acute and neuropathic pain models of the obtained compounds have shown that the type of linker used to connect pharmacophores had an effect on antinociceptive activity. Peptidomimetics containing longer flexible linkers were very effective at low doses in the neuropathic pain model. To elucidate the effect of linker lengths, two hybrids showing very high activity and two hybrids with lower activity were further tested for affinity for opioid (mu, delta) and melanocortin-4 receptors. Their complexes with the target receptors were also studied by molecular modelling. Our results do not show a simple relationship between linker length and affinity for particular receptor types but suggest that activity in neuropathic pain is related to a proper balance of receptor affinity rather than maximum binding to any or all of the target receptors.     

The Urinary Level of Injury Biomarkers Is Not Univocally Reflective of the Extent of Toxic Renal Tubular Injury in Rats

Nephrotoxicity is a major cause of intrinsic acute kidney injury (AKI). Because renal tissue damage may occur independently of a reduction in glomerular filtration rate and of elevations in plasma creatinine concentration, so-called injury biomarkers have been proposed to form part of diagnostic criteria as reflective of tubular damage independently of renal function status. We studied whether the urinary level of NGAL, KIM-1, GM2AP, t-gelsolin, and REGIIIb informed on the extent of tubular damage in rat models of nephrotoxicity, regardless of the etiology, moment of observation, and underlying pathophysiology. At a time of overt AKI, urinary biomarkers were measured by Western blot or ELISA, and tubular necrosis was scored from histological specimens stained with hematoxylin and eosin. Correlation and regression studies revealed that only weak relations existed between biomarkers and tubular damage. Due to high interindividual variability in the extent of damage for any given biomarker level, urinary injury biomarkers did not necessarily reflect the extent of the underlying tissue injury in individual rats. We contended, in this work, that further pathophysiological contextualization is necessary to understand the diagnostic significance of injury biomarkers before they can be used for renal tubular damage severity stratification in the context of nephrotoxic and, in general, intrinsic AKI.     

Individual cell lag time distributions of Cronobacter (Enterobacter sakazakii) and impact of pooling samples on its detection in powdered infant formula

Cells of six strains of Cronobacter were subjected to dry stress and stored for 2.5 months at ambient temperature. The individual cell lag time distributions of recovered cells were characterized at 25 °C and 37 °C in non-selective broth. The individual cell lag times were deduced from the times taken by cultures from individual cells to reach an optical density threshold. In parallel, growth curves for each strain at high contamination levels were determined in the same growth conditions. In general, the extreme value type II distribution with a shape parameter fixed to 5 (EVIIb) was the most effective at describing the 12 observed distributions of individual cell lag times. Recently, a model for characterizing individual cell lag time distribution from population growth parameters was developed for other food-borne pathogenic bacteria such as Listeria monocytogenes. We confirmed this model’s applicability to Cronobacter by comparing the mean and the standard deviation of individual cell lag times to populational lag times observed with high initial concentration experiments. We also validated the model in realistic conditions by studying growth in powdered infant formula decimally diluted in Buffered Peptone Water, which represents the first enrichment step of the standard detection method for Cronobacter. Individual lag times and the pooling of samples significantly affect detection performances.     

Determination of epoxidized soy bean oil (ESBO) in oily foods by GC–FID or GC–MS analysis of the methyl diepoxy linoleate

A simplified method is presented for determining epoxidized soy bean oil (ESBO) in food or food simulants, such as olive oil. ESBO is transesterified with methoxide/methanol directly in the homogenated food, i.e. without prior extraction, and analyzed on a cyanopropyl or phenyl polysiloxane stationary phase without formation of dioxolanes. For most foods, flame ionization detection (FID) was appropriate, but for samples with interfering components, GC–MS was needed. Chemical ionization (CI) with ammonia is more sensitive and more selective than electron impact ionization (EI). In CI, positive and negative ion monitoring (PCI and NCI) are similar in sensitivity, but different in selectivity, i.e. the combination of the two is well suited for confirmation. Results are shown to be in agreement with on-line LC–GC–FID.     

The effect of the structure of native banana starch from two varieties on its acid hydrolysis

Two banana starches were studied to analyze the effect of the acid hydrolysis on their molecular structure, and the impact in their physicochemical features. The native banana starches exhibit differences in the amylose content, molar mass, gelatinization parameters, X-ray diffraction pattern, and pasting profile. These results suggested that different acid hydrolysis mechanisms may be operative in these two starches. The kinetic hydrolysis is different in both banana starches that are related to the crystalline packing of the starch molecules. This was confirmed by the amylose content, the X-ray diffraction pattern, and the thermal study in the acid hydrolyzed starches at different times. The acid-treated Roatan starch showed higher retrogradation than Macho starch, a phenomenon that increases in the sample hydrolyzed for the longer time. This pattern is related to the amylose/amylopectin ratio, the reduction in the molar mass and the gyration radius. The acid hydrolysis of banana starches, although they have some similarities, they are different.