Polymerization of hydroxyacetylenes by ruthenium alkylidene complexes

Polymerization of a series of acetylenes with a hydroxy functional group was investigated by using modified 2nd generation Grubbs (A) and Grubbs–Hoveyda (B) initiators. Owing to excellent tolerance for polar functional groups, catalysts A and B polymerized 3-butyn-2-ol (1), 2-methyl-3-butyn-2-ol (2) and 3-butyn-1-ol (3). The catalytic activities of catalyst B were greater than those of initiator A for these polymerizations. The steric bulk and the position of hydroxyl group of the monomer had an influence on the rate of polymerization. In order to investigate the role of hydroxyl group of monomers in the polymerization, the reaction between hydroxyacetylenes and the ruthenium complexes were monitored by ¹H NMR spectroscopy. The results revealed the formation of new alkylidene species via α-insertion. The calculated relative energies of propagating species formed in the reaction of A with monomer 1 suggested the formation of oxygen-chelated species. The structures of resulting polymers were characterized by various methods such as NMR, IR and UV–Vis spectroscopies. The ruthenium initiators gave polymers with different geometric structure of main chain than conventional catalysts.     

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.     

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.     

Light activation of a cysteine protease inhibitor: caging of a peptidomimetic nitrile with Ru(II)(bpy)2

A novel method for caging protease inhibitors is described. The complex [Ru(II)(bpy)(2)(1)(2)](PF(6))(2) (2) was prepared from the nitrile-based peptidomimetic inhibitor Ac-Phe-NHCH(2)CN (1). (1)H NMR, UV-vis, and IR spectroscopic and mass spectrometric data confirmed that 2 equiv of inhibitor 1 bind to Ru(II) through the nitrile functional group. Complex 2 shows excellent stability in aqueous solution in the dark and fast release of 1 upon irradiation with visible light. As a result of binding to the Ru(II) center, the nitriles of complex 2 are caged, and 2 does not act as a potent enzyme inhibitor. However, when 2 is irradiated, it releases 1, which inhibits the cysteine proteases papain and cathepsins B, K and L up to 2 times more potently than 1 alone. Ratios of the IC(50) values in the dark versus in the light ranged from 6:1 to 33:1 for inhibition by 2 against isolated enzymes and in human cell lysates, confirming that a high level of photoinduced enzyme inhibition can be obtained using this method.     

Preparation of graphene/tetrathiafulvalene nanocomposite switchable surfaces

A one step process for simultaneous reduction and functionalization of graphene oxide using tetrathiafulvalene (TTF) is described. Chemical oxidation of TTF to TTF(2+) using an aqueous solution of Fe(ClO(4))(3) expels the charged molecule from the graphene nanosheets, while subsequent immersion in neutral TTF solution allows the capture of the TTF molecules.     

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.     

Three Modes of Proton Transfer in One Chromophore: Photoinduced Tautomerization in 2‐(1H‐Pyrazol‐5‐yl)Pyridines,Their Dimers and Alcohol Complexes

Studies of 2‐(1H‐pyrazol‐5‐yl)pyridine (PPP) and its derivatives 2‐(4‐methyl‐1H‐pyrazol‐5‐yl)pyridine (MPP) and 2‐(3‐bromo‐1H‐pyrazol‐5‐yl)pyridine (BPP) by stationary and time‐resolved UV/Vis spectroscopic methods, and quantum chemical computations show that this class of compounds provides a rare example of molecules that exhibit three types of photoreactions: 1) excited‐state intramolecular proton transfer (ESIPT) in the syn form of MPP, 2) excited‐state intermolecular double‐proton transfer (ESDPT) in the dimers of PPP in nonpolar media, as well as 3) solvent‐assisted double‐proton transfer in hydrogen‐bonded 1:1 complexes of PPP and MPP with alcoholic partners. The excited‐state processes are manifested by the appearance of a dual luminescence and a bimodal irreversible kinetic coupling of the two fluorescence bands. Ground‐state syn–anti equilibria are detected and discussed. The fraction of the higher‐energy anti form varies for different derivatives and is strongly dependent on the solvent polarity and hydrogen‐bond donor or acceptor abilities.     

Finite groups with some NR-subgroups or {\mathcal{H}}-subgroups

Berkovich investigated the following concept: a subgroup H of a finite group G is called an NR-subgroup (Normal Restriction) if whenever ${K \trianglelefteq H}$ , then ${K^G \cap H = K}$ , where K ^G is the normal closure of K in G. Bianchi, Gillio Berta Mauri, Herzog and Verardi proved a characterization of soluble T-groups by means of ${\mathcal{H}}$ -subgroups: a subgroup H of G is said to be an ${\mathcal{H}}$ -subgroup of G if ${H^g \cap N_G(H) \leq H}$ for all ${g \in G}$ . In this article we give new characterizations of finite soluble PST-groups in terms of NR-subgroups or ${\mathcal{H}}$ -subgroups. We will show that they are different from the ones given by Ballester-Bolinches, Esteban-Romero and Pedraza-Aguilera. Robinson established the structure of minimal non-PST-groups. We give the classification of groups all of whose second maximal subgroups (of even order) are soluble PST-groups.     

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.     

3D analysis of the morphology and spatial distribution of nitrogen in nitrogen-doped carbon nanotubes by energy-filtered transmission electron microscopy tomography

We present here the application of the energy-filtered transmission electron microscopy (EFTEM) in the tomographic mode to determine the precise 3D distribution of nitrogen within nitrogen-doped carbon nanotubes (N-CNTs). Several tilt series of energy-filtered images were acquired on the K ionization edges of carbon and nitrogen on a multiwalled N-CNT containing a high amount of nitrogen. Two tilt series of carbon and nitrogen 2D maps were then calculated from the corresponding energy-filtered images by using a proper extraction procedure of the chemical signals. Applying iterative reconstruction algorithms provided two spatially correlated C and N elemental-selective volumes, which were then simultaneously analyzed with the shape-sensitive reconstruction deduced from Zero-Loss recordings. With respect to the previous findings, crucial information obtained by analyzing the 3D chemical maps was that, among the two different kind of arches formed in these nanotubes (transversal or rounded ones depending on their morphology), the transversal arches contain more nitrogen than do the round ones. In addition, a detailed analysis of the shape-sensitive volume allowed the observation of an unexpected change in morphology along the tube axis: close to the round arches (with less N), the tube is roughly cylindrical, whereas near the transversal ones (with more N), its shape changes to a prism. This relatively new technique is very powerful in the material science because it combines the ability of the classical electron tomography to solve 3D structures and the chemical selectivity of the EFTEM imaging.