A fine-tuned molybdenum hexacarbonyl/phenol initiator for alkyne metathesis

A new, highly potent activator for molybdenum hexacarbonyl and 2-fluorophenol is described. An "instant"catalyst formed in situ from molybdenum hexacarbonyl and 2-fluorophenol shows high activity for cross- and ring-closing alkyne metathesis reaction. The use of 2-fluorophenol can be combined with other activation methods to allow alkyne metathesis at relatively low temperature (80 degrees C).     

Identification of proteases employed by dendritic cells in the processing of protein purified derivative (PPD)

Dendritic cells (DC) are known to present exogenous protein Ag effectively to T cells. In this study we sought to identify the proteases that DC employ during antigen processing. The murine epidermal-derived DC line Xs52, when pulsed with PPD, optimally activated the PPD-reactive Th1 clone LNC.2F1 as well as the Th2 clone LNC.4k1, and this activation was completely blocked by chloroquine pretreatment. These results validate the capacity of XS52 DC to digest PPD into immunogenic peptides inducing antigen specific T cell immune responses. XS52 DC, as well as splenic DC and DCs derived from bone marrow degraded standard substrates for cathepsins B, C, D/E, H, J, and L, tryptase, and chymases, indicating that DC express a variety of protease activities. Treatment of XS52 DC with pepstatin A, an inhibitor of aspartic acid proteases, completely abrogated their capacity to present native PPD, but not trypsin-digested PPD fragments to Th1 and Th2 cell clones. Pepstatin A also inhibited cathepsin D/E activity selectively among the XS52 DC-associated protease activities. On the other hand, inhibitors of serine proteases (dichloroisocoumarin, DCI) or of cystein proteases (E-64) did not impair XS52 DC presentation of PPD, nor did they inhibit cathepsin D/E activity. Finally, all tested DC populations (XS52 DC, splenic DC, and bone marrow-derived DC) constitutively expressed cathepsin D mRNA. These results suggest that DC primarily employ cathepsin D (and perhaps E) to digest PPD into antigenic peptides.     

Stabilization effect of potential antioxidants on the thermooxidative stability of styrene–butadiene rubber

Effects of several heterocyclic compounds containing nitrogen, trisubstituted amines and diamines and molecules based on N,N,N′,N′,N′′,N′′-substituted-[1,3,5]triazine-2,4,6-triamine in preventing thermooxidative degradation of styrene–butadiene rubber (SBR) have been studied using non-isothermal DSC measurements. The aim of this study was to determine and compare the stabilizing effect of individual compounds and to select the structures with the best antioxidative properties. In order to compare the stabilizing effect of the compounds, induction periods and protection factors have been calculated. The treatment of the experimental data was carried out using a method based on a non-Arrhenian temperature function. The results show that better antioxidative properties can be assigned to heterocyclic compounds. On the other hand, molecules containing triazine structures exhibited only negligible stabilizing effect on SBR at lower temperatures and even destabilizing effect at higher temperatures.     

Study of radon exhalation from the soil

The influence of meteorological parameters on radon exhalation rate was analyzed. The analyses show a significant influence of precipitation on radon exhalation rate. The highest exhalation rate was found during dry periods and the lowest during the periods of strong precipitation. We also tested two different types of detectors for the measurement of radon exhalation rate—the ionization chamber (AlphaGUARD) and the scintillation chamber of Lucas type. The exhalation rates measured by these detectors were in a good agreement. Likewise, there was an agreement in radon exhalation rates determined from short term and long term increases in radon activity concentration.     

Aqueous olefin metathesis

According to popular belief, oxygen and water are the natural enemies of organometallic reactions and therefore must be excluded rigorously from the reaction vessel. This belief is founded in the case of the highly reactive nucleophilic metal alkylidene complexes that were used in early catalytic olefin metathesis. However, owing to the high stability of the ruthenium carbene complexes introduced by Grubbs, metathesis in water has become reality.     

On functions having Cauchy differences in some prescribed sets

Summary AssumeE is a real topological vector space,F is a real Banach space,K is a discrete subgroup ofF andC is a symmetric, convex and compact subset ofF such thatK (6C) = {0}. If a functionh:E F is continuous at at least one point andh(x + y) – h(x) – h(y) K + C for allx, y E, then there exists a continuous linear functiona:E F such thath(x) – a(x) K + C for everyx E.     

Implementation of the multireference Brillouin-Wigner and Mukherjee's coupled cluster methods with non-iterative triple excitations utilizing reference-level parallelism

In this paper we discuss the performance of the non-iterative state-specific multireference coupled cluster (SS-MRCC) methods accounting for the effect of triply excited cluster amplitudes. The corrections to the Brillouin-Wigner and Mukherjee's MRCC models based on the manifold of singly and doubly excited cluster amplitudes (BW-MRCCSD and Mk-MRCCSD, respectively) are tested and compared with exact full configuration interaction results for small systems (H(2)O, N(2), and Be(3)). For the larger systems (naphthyne isomers) the BW-MRCC and Mk-MRCC methods with iterative singles, doubles, and non-iterative triples (BW-MRCCSD(T) and Mk-MRCCSD(T)) are compared against the results obtained with single reference coupled cluster methods. We also report on the parallel performance of the non-iterative implementations based on the use of processor groups.     

13C shielding scale for MAS NMR spectroscopy

We have performed the direct measurements of ¹³C magnetic shielding for pure liquid TMS, solution of 1% TMS in CDCl₃ and solid fullerene. The measurements were carried out in spherical ampoules exploring the relation between the resonance frequencies, shielding constants and magnetic moments of ¹³C and ³He nuclei. Next the ¹³C shielding constants of glycine, hexamethylbenzene and adamantane were established on the basis of appropriate chemical shifts measured in the solid state. All the new results are free from susceptibility effects and can be recommended as the reference standards of ¹³C shielding scale in the magic angle spinning NMR experiments. Copyright © 2011 John Wiley & Sons, Ltd.     

DSC study of stabilizing effect of antioxidant mixtures in styrene-butadiene rubber

The type of cooperation between antioxidants in the binary mixtures of four substituted diphenylamines and phenotiazine in the stabilization of styrene-butadiene rubber has been tested. Thermooxidation of the samples has been studied by differential scanning calorimetry under non-isothermal conditions. The protection factors of the individual stabilizers and their mixtures were determined. The synergy factors were applied to asses the type of cooperation of antioxidants in the mixtures. From their values it can be concluded that the type of cooperation depends on temperature. The highest synergistic effect has been observed for the mixture of phenotiazine and [4-(1-methyl-1-phenyl-ethyl)-phenyl]-phenylamine.