Calcium carbonate decomposition

Calcium carbonate decomposes under well-defined conditions giving CaO (solid) and CO₂ (gas). The process kinetics are known to be strongly influenced by the CO₂ partial pressure and temperature. In dynamic conditions, as in thermogravimetric analysis (TG) and differential thermal analysis (DTA), kinetics influence the observed heat effect and mass losses, as was shown in semi-static studies by Hyatt et al. (J Am Ceram Soc 41:70–74, 1). However, differing DTA and TG curve shapes are reported in the literature even under supposedly comparable conditions. The differences are attributed in part to the design of the equipment and in part to differing crystalline states of the precursor calcium carbonate. To resolve these uncertainties, the TG has been performed at different heating rates and at different but controlled partial pressures of CO₂. The results are reported and critically evaluated in the light of the data obtained, and the kinetic parameters as reported by Hyatt et al. (J Am Ceram Soc 41:70–74, 1) are re-evaluated.     

Adsorption of polyelectrolyte-nanoparticle systems on silica: influence of ionic strength

In this work the effect of ionic strength on the adsorption behavior of cationic polyelectrolyte (acrylamide-acrylamidopropyltrimethylammonium chloride) and negatively charged silica particles has been studied by means of ellipsometry. The adsorption of the polyelectrolyte was observed to increase with increasing salt concentration, a behavior typical for polyelectrolytes with a screening-reduced solvency and a nonelectrostatic affinity for the surface. A similar dependence on the ionic strength was observed when studying the electrolyte effect on the nanoparticle adsorption to the preadsorbed polyelectrolyte film, suggesting that the polyelectrolyte surface conformations largely govern the binding capacity of the particles to the surface.     

Fluorescence contrast and threshold limit: implications for photodynamic diagnosis of basal cell carcinoma

This study was designed to evaluate what application time of delta-5-aminolaevulinic acid (ALA) results in highest contrast between tumour and normal skin, in the interval 1-4 h, when using photodynamic diagnosis (PDD) of basal cell carcinomas (BCC) located on the face. Moreover, a value of the demarcation limit has been derived based on the fluorescence variation in normal skin adjacent to the tumour. Forty patients were included in the study, randomly allocated to four different groups with varying ALA application time in the range 1-4 h. The contrast, defined as the ratio between the fluorescence intensity in ALA-treated tumour tissue and normal skin, was calculated for each patient, and the mean values in each group were evaluated as a function of ALA application time. In addition, the fluorescence intensity variation in ALA-treated normal skin adjacent to the tumour was assessed. The results from this study show a peak of the mean contrast values after 3 h ALA application, but due to large interpatient variation, the mean contrast did not differ significantly in the interval 2-4 h. After 2 h ALA application, the fluorescence intensity variation in the normal ALA-treated skin was found to be at a maximum, which suggests that 2 h ALA application is not preferable when using PDD. Based on data of the fluorescence variation in ALA-treated normal skin after 3 and 4 h ALA application, a tolerance interval was calculated implying that values above 1.4 times the mean normal fluorescence indicate an abnormal condition. This tolerance limit agrees well with results obtained in a former study.     

Functional off‐stoichiometry thiol‐ene‐epoxy thermosets featuring temporally controlled curing stages via an UV/UV dual cure process

We present a facile two‐stage UV/UV activation method for the polymerization of off‐stoichiometry thiol‐ene‐epoxy, OSTE+, networks. We show that the handling and processing of these epoxy‐based resins is made easier by introducing a material with a controlled curing technique based on two steps, where the first step offers excellent processing capabilities, and the second step yields a polymer with suitable end‐properties. We investigate the sequential thiol‐ene and thiol‐epoxy reactions during these steps by studying the mechanical properties, functional group conversion, water absorption, hydrolytic stability, and thermal stability in several different thiol‐ene‐epoxy formulations. Finally, we conclude that the curing stages can be separated for up to 24 h, which is promising for the usefulness of this technique in industrial applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2604‐2615     

Interfacial behavior of cubic liquid crystalline nanoparticles at hydrophilic and hydrophobic surfaces

The adsorption behavior of self-assembled lipid liquid crystalline nanoparticles at different model surfaces was investigated in situ by use of ellipsometry. The technique allows time-resolved monitoring of the adsorbed amount and layer thickness under transient and steady-state conditions. The system under study was cubic-phase nanoparticle (CPNP) dispersions of glycerol monooleate stabilized by a nonionic block copolymer, Pluronic F-127. Depending on the surface properties and presence of electrolytes, different adsorption scenarios were discerned: At hydrophilic silica thick surface layers of CPNPs are generated by particle adsorption from dispersions containing added electrolyte, but no adsorption is observed in pure water. Adsorption at the hydrophobic surface involves extensive structural relaxation and formation, which is not electrolyte sensitive, of a classic monolayer structure. The different observations are rationalized in terms of differences in interactions among the CPNP aggregates, their unimer constituents, and the surface and show a strong influence of interfacial interactions on structure formation. Surface self-assembly structures with properties similar to those of the corresponding bulk aggregates appear exclusively in the weak interaction limit. This observation is in agreement with observations for surfactant self-assembly systems, and our findings indicate that this behavior is applicable also to complex self-assembly structures such as the CPNP structures discussed herein.     

Monobenzofused 1,4‐Azaborines: Synthesis,Characterization, and Discovery of a Unique Coordination Mode

We report the first general synthesis of boron‐substituted monobenzofused 1,4‐azaborines using ring‐closing metathesis of an enamine‐containing diene as a key synthetic strategy. As part of our investigations, we discovered that the B‐C3 moiety in a 1,4‐azaborine can serve uniquely as a η²‐L‐type ligand. This functionality is exemplified by two κ²‐N‐η²‐BC Pt complexes of a boron‐pyridyl‐substituted monobenzofused‐1,4‐azaborine. Single‐crystal X‐ray diffraction analysis of the Pt complexes shows a strong structural contribution from the iminium resonance form of the monobenzofused‐1,4‐azaborine ligand. We also demonstrate that a palladium(0) complex supported by a 1,4‐azaborine‐based phosphine ligand can catalyze hydroboration of 1‐buten‐3‐yne with unique selectivity. In view of the importance of arene–metal π‐interactions in catalytic applications, this work should open new opportunities for ligand design involving the 1,4‐azaborine motif as an arene substitute.     

Inhibition of Insulin-Regulated Aminopeptidase (IRAP) by Arylsulfonamides

The inhibition of insulin-regulated aminopeptidase (IRAP, EC 3.4.11.3) by angiotenesin IV is known to improve memory and learning in rats. Screening 10 500 low-molecular-weight compounds in an enzyme inhibition assay with IRAP from Chinese Hamster Ovary (CHO) cells provided an arylsulfonamide (N-(3-(1H-tetrazol-5-yl)phenyl)-4-bromo-5-chlorothiophene-2-sulfonamide), comprising a tetrazole in the meta position of the aromatic ring, as a hit. Analogues of this hit were synthesized, and their inhibitory capacities were determined. A small structure–activity relationship study revealed that the sulfonamide function and the tetrazole ring are crucial for IRAP inhibition. The inhibitors exhibited a moderate inhibitory potency with an IC₅₀=1.1±0.5 μm for the best inhibitor in the series. Further optimization of this new class of IRAP inhibitors is required to make them attractive as research tools and as potential cognitive enhancers.     

SPE and HPLC/UV of resin acids in colophonium-containing products

A new method, involving SPE and HPLC/UV diode-array detection (DAD), was developed for the quantification of colophonium components in different consumer products, such as cosmetics. Colophonium is a common cause of contact dermatitis since its components can oxidize into allergens on exposure to air. Three different resin acids were used as markers for native and oxidized colophonium, abietic acid (AbA), dehydroabietic acid (DeA), and 7-oxodehydroabietic acid (7-O-DeA). The SPE method, utilizing a mixed-mode hydrophobic and anion exchange retention mechanism, was shown to yield very clean extracts. The use of a urea-embedded C(12) HPLC stationary phase improved the separation of the resin acids compared to common C(18). Concentrations higher than 2 mg/g of both AbA and DeA were detected in wax strips. In this product also 7-O-DeA, a marker for oxidized colophonium, was detected at a level of 28 microg/g. The LODs were in the range of 7-19 microg/g and the LOQs 22-56 microg/g. The method is simple to use and can be applied on many types of technical products, not only cosmetics. For the first time, a method for technical products was developed, which separates AbA from pimaric acid.     

Directed assembly of gold nanoparticles

As a complement to common “top–down” lithography techniques, “bottom–up” assembly techniques are emerging as promising tools to build nanoscale structures in a predictable way. Gold nanoparticles that are stable and relatively easy to synthesize are important building blocks in many such structures due to their useful optical and electronic properties. Programmed assembly of gold nanoparticles in one, two, and three dimensions is therefore of large interest. This review focuses on the progress from the last three years in the field of directed gold nanoparticle and nanorod assembly using, for example, DNA or specific chemical interactions as template.