Thermal stability of hybrid materials based on epoxy functional (poly)siloxanes

Epoxy functional (poly)siloxanes are one of the most important classes of modified silicones. Due to high reactivity of epoxy group and specific features of siloxane chain, they can make an excellent raw material for synthesis of hybrid materials. Results obtained in this study have shown that both the modification of epoxy resins with epoxy functional disiloxanes as well as the application of polysiloxanes with long polysiloxane chains and a specified content of epoxy groups makes it possible to produce hybrid materials of very good thermal stability. Crosslinking reactions were carried out with use of four diamines of which the best one appeared to be 4,4??-diaminodiphenylmethane. The highest thermal stability was found in the case of hybrid materials obtained from epoxy functional polysiloxanes.     

Disulfide proteomics for identification of extracellular or secreted proteins

The combination of SDS-PAGE and MS is one of the most powerful and perhaps most frequently used gel-based proteomics approaches in protein identification. However, one drawback of this method is that separation takes place under denaturing and reducing (R) conditions and as a consequence, all proteins with identical apparent molecular mass (Mr) will run together. Therefore, low-abundant proteins may not be easily identified. Another way of investigating proteins by proteomics is by analyzing subproteomes from a total proteome such as phosphoproteomics, glycoproteomics, or disulfide proteomics. Here, we took advantage of the property of secreted proteins to form disulfide bridges and investigated disulfide-linked proteins, using SDS-PAGE under nonreducing (NR) conditions. We separated sera from normal subjects and from patients with various diseases by SDS-PAGE (NR) and (R) conditions, followed by LC-MS/MS analysis. Although we did not see any detectable difference between the sera separated by SDS-PAGE(R), we could easily identify the disulfide-linked proteins separated by SDS-PAGE (NR). LC-MS/MS analysis of the disulfide-linked proteins correctly identified haptoglobin (Hp), a disulfide-linked protein usually found as a heterotetramer or as a disulfide-linked heteropolymer. Western blotting under NR and R conditions using anti-Hp antibodies confirmed the LC-MS/MS experiments and further confirmed that upon reduction, the disulfide-linked Hp heterotetramers and polymers were no longer disulfide-linked polymers. These data suggest that simply by separating samples on SDS-PAGEunder NR conditions, a different, new proteomics subset can be revealed and then identified.     

UV-Vis Investigation on the Hydrocarbon Length Effect on the α-Tocopherol Solubility in an AOT/n-Alkane/Water System

The influence of n-alkane hydrocarbon chain length on both binding and distribution constants of α-tocopherol and Aerosol-OT [sodium bis(2-ethylhexyl) sulfosuccinate] reversed micelles were studied with the UV-vis method using n-heptane and n-decane as solvents. The amount of water in the system was determined by R defined as the ratio of water to surfactant molalities ( $R=[\hbox{H$_{2}$O}]/[\hbox{AOT}]$ ). No significant water influence on distribution and binding constants was observed. This finding is consistent with earlier results, which indicated that the location of α-tocopherol molecules in the AOT reversed micelles is the palisade layer. The results obtained indicate that the longer hydrocarbon chain length makes surroundings of micelles more ordered and causes some limitations in α-tocopherol access to its palisade layer. This implies a weaker connection to the micellar structure and an increase of α-tocopherol freedom of motion in the space of hydrocarbon tails around polar core.     

A new pricing scheme for a multi-period pool-based electricity auction

A new pricing scheme is proposed for determining the social welfare distribution in a centralized pool-based auction in the context of solving the unit commitment problems under competition. A significant contribution of this paper over previous publications on this subject is the inclusion of the price-responsive demand side for the multi-period auctions with dynamic commitment characteristics. The model allows every thermal unit and every consumer to obtain individual maximum profits, and at the same time it gives the market coordinator an adequate tool for solving the ensuing technologically constrained unit commitment problem with fair market clearing. The pricing model is in the form of a mixed linear programming model that minimizes the sum of the compensation costs. The accompanying case study illustrates the approach proposed.     

Three-parametric equation in evaluation of thermal dissociation of reference compound

Further considerations concerning thermal decomposition of reference material — CaCO₃, described by three-parametric equation in version (3), have been presented. It was established that in linear relationship between coefficients of Eq. (3) a ₂ is the argument of a ₁, which reaches minimal value of thermodynamic character (δH/vR) when a ₂=0 (equilibrium relationship). During thermal decomposition connection between system atmosphere — rich in CO₂ or vacuum, caused by fast evacuation of gaseous products — and activation energy value, as well as maximal temperature of reaction process. Conditions of this kind may be explained by Zawadzki-Bretsznajder law.     

Structure, conformation and hydrogen bonding of two amino-cycloalkanespiro-5-hydantoins

The crystal structures of 3-amino-cycloheptanespiro-4′-imidazolidine-2′,5′-dione (I) {systematic name: 3-amino-1,3-diazaspiro[4.6] undecane-2,4-dione} and 3-amino-cyclooctanespiro-4′-imidazolidine-2′,5′-dione (II) {systematic name: 3-amino-1,3-diazaspiro[4.7] dodecane-2,4-dione}, have been determined. In both compounds the polar hydantoin groups cause molecules to aggregate via N-H...O and N-H...N interactions, forming a layer structure, in which the cycloalkane rings project outwards from the central, more polar, region. The observed molecular structure is compared with that calculated by density functional theory methods.      

New Coordination Compounds Based on a Pyrazine Derivative: Design,Characterization, and Biological Study

New coordination compounds of Mn(II), Fe(III), Co(II), and Ni(II) and the biologically active ligand L (N′-benzylidenepyrazine-2-carbohydrazonamide) were synthesized and characterized by appropriate analytical techniques: elemental analysis (EA), thermogravimetric analysis (TG–DTG), infrared spectroscopy (FTIR), and flame-atomic absorption spectrometry (F-AAS). The biological activity of the obtained compounds was then comprehensively investigated. Rational use of these compounds as potential drugs was proven by ADME analysis. All obtained compounds were screened in vitro for antibacterial, antifungal, and anticancer activities. Some of the studied complexes exhibited significantly higher activity than the ligand alone.     

ChemInform Abstract: Influence of Nickel Substitution on the Cation Distribution and Magnetic Properties of ZnCr2Se4.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Polarity identification of GaN bulk single crystals (0001) surface by Auger electron spectroscopy

An attempt to identify the polarity of (0001) polar surface of GaN bulk single crystals grown by high nitrogen pressure solution method has been made using Auger electron spectroscopy (AES). AES concentration depth profiles of the top layer in (0001) direction starting from both (0001) faces of the sample have been measured. Distinct difference in the Ga concentration at the sample surface of both faces has been observed. The dependence of Ga eoncentration on depth is also different for both faces of the sample.