Rate constant for the reaction Br + O3 → BrO + O2 from 248 to 418 K: Kinetics and mechanism

The rate constant for the Br + O₃ → BrO + O₂ reaction was measured by the discharge flow technique, employing resonance fluorescence detection of Br. Over the temperature range 248 to 418 K, in 1 to 3 torr of He, decays of Br in excess O₃ yield the value k₁ = (3.28 ± 0.40) × 10^?11 e^[?944±30]/T cm³ molecule^?1 s^?1. Cited uncertainties are at the 95% confidence level and include an estimate of the systematic errors. The rate constants for the reactions of O₃ with Br, Cl, F, OH, O, and N correlate with the electron affinities of the radicals suggesting that the reactions proceed through early transition states dominated by transfer of electron density from the highest occupied molecular orbital of ozone to the singly occupied radical MO. The implications of this new measurement of k₁ for stratospheric chemistry are discussed.     

Mitochondrial activities in human cultured skin fibroblasts contaminated by <Emphasis Type="Italic">Mycoplasma hyorhinis</Emphasis>

Background  

Mycoplasma contaminations are a recurrent problem in the use of cultured cells, including human cells, especially as it has been shown to impede cell cycle, triggering cell death under various conditions. More specific consequences on cell metabolism are poorly known.     

Activity Coefficients of HCl + GdCl3 + H2O System from 5 to 55°C. Application of Pitzer Formalism

The emf of the cell

Polarization coherent anti‐stokes Raman scattering using noisy light

Several polarization studies on the noisy light version of coherent anti‐Stokes Raman scattering (CARS) exist in the literature. However, the full advantages of polarization CARS (P‐CARS), which are so useful in conventional and short‐pulse CARS methods, have not yet been exploited in the noisy light version. This work presents experimental realization of fully functional P‐CARS using noisy light. Several examples demonstrate the advantages brought by P‐CARS. This includes the ‘classic’ example of benzene in carbon tetrachloride. Also presented are the carbon–carbon double bond stretches in acrylonitrile and 1‐hexene. An interesting, and not fully understood, detection polarization angle dependence is discussed. Applications to an m‐xylene/benzene mixture and an alkaline solution of the amino acid phenylalanine are presented. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of a versatile 2 (1H)-pyrazinone core for the preparation of Tissue Factor-Factor VIIa inhibitors

A new, general synthetic route to 2(1H)-pyrazinones 11 is described. The four-step synthesis is accomplished utilizing a regioselective hydrolysis and N-alkylation. These compounds efficiently undergo metal-catalyzed cross-coupling reactions to install P2 diversity groups in the 6-position, which can be used to refine the SAR of the S2 pocket of the Tissue Factor/Factor VIIa (TF/VIIa) complex.     

Noetherian Connected Graded Algebras of Global Dimension 3

Let A be a noetherian connected graded algebra of global dimension 3. We show that A is regular in the sense of Artin and Schelter if one of the following conditions holds: (1) A is generated by two elements; (2) the graded simple module has a standard resolution; (3) the degrees of minimal relations are the same (this includes the quadratic case). Some general properties of A are studied without assuming regularity.     

Monte-Carlo simulation of ternary blends of block copolymers and homopolymers

We perform a theoretically informed coarse grain Monte-Carlo simulation in the nPT-ensemble and the Gibbs ensemble on symmetric ternary mixtures of AB-diblock copolymers with the corresponding homopolymers. We study the lamellar period by varying the length and amount of homopolymers. The homopolymer distribution within the lamellar morphology is determined as is the maximum amount of homopolymer within the lamellae. Gibbs ensemble simulations are used to locate the three-phase coexistence between two homopolymer-rich phases and a lamellar phase.     

Design and synthesis of an “ultrachelating” ligand based on an 18-membered ring hexaaza macrocycle

Abstract

A new ultrachelating ligand, H₄PYTA (3,6,14,17,23,24-hexaazatricyclo[17.3.1.1^(8.12)]tetracosa-1(23),8,10,12(24),19,21-hexaene-3,6,14,17-tetraacetic acid), has been synthesized by tetracar-boxymethylation of the parent ligand PYAN (3,6,14,17,23,24-hexaazatricyclo[17.3.1.1^(8.12)]tetracosa-1(23),8,10,12(24),19,21-hexaene). Both of these ligands are based upon the [18]aneN₆ macrocyclic framework in which two trans dimethylamino groups are replaced by 2,6-substituted pyridine. The metal binding constants for PYTA^4- (log K^ML) were measured for sixteen metals and were found to be comparable to those for DTPA^5- and DOTA^4-. PYTA^4- binds well to an extraordinarily large range of metal ions from small Ga³⁺ to large Pb²⁺. This behavior is attributable to the flexible wrapping of the PYAN framework and the ability of PYTA^4- to be six-coordinate with small metals and ten-coordinate with large metals.