An invariance principle for reversible Markov processes. Applications to random motions in random environments

We present an invariance principle for antisymmetric functions of a reversible Markov process which immediately implies convergence to Brownian motion for a wide class of random motions in random environments. We apply it to establish convergence to Brownian motion (i) for a walker moving in the infinite cluster of the two-dimensional bond percolation model, (ii) for ad-dimensional walker moving in a symmetric random environment under very mild assumptions on the distribution of the environment, (iii) for a tagged particle in ad-dimensional symmetric lattice gas which allows interchanges, (iv) for a tagged particle in ad-dimensional system of interacting Brownian particles. Our formulation also leads naturally to bounds on the diffusion constant.     

Fock space on C∞ and Bose-Fock space

In this paper, we introduce the Fock space on ${\mathbb{C}}^{\infty }$ and obtain an isomorphism between the Fock space on ${\mathbb{C}}^{\infty }$ and Bose-Fock space. Based on this isomorphism, we obtain representations of some operators on the Bose-Fock space and answer a question in [2]. As a physical application, we study the Gibbs state.     

Schmelzreaktionen mit Aluminiumchlorid 3. Mitteilung [1] Zur Kenntnis der Pyridinio-anthrachinon-Derivate aus der Pyridin-Aluminiumchloridschmelze von Aminoanthrachinonen

In continuation of previous work, the behaviour of amino-anthraquinones on fusion in pyridine - aluminium chloride in the presence of oxidants is studied. Instead of dimerisation the reaction leads to salts of pyridinio-aminoanthraquinones and further to condensed “anthraimidazopyridine” derivatives.     

Temperature dependence of hydrogen bonding: an investigation of the retention of primary and secondary alcohols in gas-liquid chromatography

Configurational-bias Monte Carlo simulations in the Gibbs Ensemble were carried out to investigate the analyte partitioning of n-pentane, n-hexane, n-heptane, 1-propanol, and 2-propanol into a dioctyl ether retentive (stationary) phase used in gas-liquid chromatography. The united-atom version of the TraPPE (transferable potentials for phase equilibria) force field was used to model all analytes and the solvent. The analyte partition coefficients, Gibbs free energies of transfer, and Kovats retention indexes were calculated at four different temperatures ranging from 303.15 to 348.15 K. Although hydrogen bonding is a major contributor to the retention of the alcohol analytes over the entire temperature range, its importance for the separation factor between the primary and secondary alcohol decreases substantially with increasing temperature. The enthalpies and entropies for hydrogen bond formation were also estimated from the temperature dependence of the corresponding equilibrium constants. In agreement with experimental measurements, it is observed that the hydrogen bond involving 1-propanol is enthalpically favored, but entropically disfavored compared to 2-propanol.     

A new method of microvolume back-extraction procedure for enrichment of Pb and Cd and determination by flame atomic absorption spectrometry

The need for highly reliable methods for the determination of trace elements has been recognised in analytical chemistry and environmental science. A method for the trace analysis of Pb and Cd in natural waters is described. In a preconcentration step, 500 ml of an aqueous sample containing lead and cadmium were extracted into 3.5 ml of a solution containing a complexing agent (dithizone) in xylene. Subsequently, the dithizonate complexes were back-extracted into 600 mul of nitric acid solution for direct determination by flame atomic absorption spectrometry. Important microextraction parameters were optimised using spiked deionised water. The 3sigma detection limits, relative standard deviations and linear calibration graphs were, respectively, 0.39 mugl(-1), 6.3% and 1.0-20.0 mugl(-1) for lead and 8.2 ngl(-1), 4.0% and 0.05-1.0 mugl(-1) for cadmium for solvent microextraction times of 4 min and microvolume back-extraction times of 1 min. The preconcentration factors were 543- and 331-fold for lead and cadmium, respectively.     

Reductive elimination/oxidative addition of carbon-hydrogen bonds at Pt(IV)/Pt(II) centers: mechanistic studies of the solution thermolyses of Tp(Me2)Pt(CH3)2H

Reductive elimination of methane occurs upon solution thermolysis of kappa(3)-Tp(Me)2Pt(IV)(CH(3))(2)H (1, Tp(Me)2 = hydridotris(3,5-dimethylpyrazolyl)borate). The platinum product of this reaction is determined by the solvent. C-D bond activation occurs after methane elimination in benzene-d(6), to yield kappa(3)-Tp(Me)2Pt(IV)(CH(3))(C(6)D(5))D (2-d(6)), which undergoes a second reductive elimination/oxidative addition reaction to yield isotopically labeled methane and kappa(3)-Tp(Me)2Pt(IV)(C(6)D(5))(2)D (3-d(11)). In contrast, kappa(2)-Tp(Me)2Pt(II)(CH(3))(NCCD(3)) (4) was obtained in the presence of acetonitrile-d(3), after elimination of methane from 1. Reductive elimination of methane from these Pt(IV) complexes follows first-order kinetics, and the observed reaction rates are nearly independent of solvent. Virtually identical activation parameters (DeltaH(++)(obs) = 35.0 +/- 1.1 kcal/mol, DeltaS(++)(obs) = 13 +/- 3 eu) were measured for the reductive elimination of methane from 1 in both benzene-d(6) and toluene-d(8). A lower energy process (DeltaH(++)(scr) = 26 +/- 1 kcal/mol, DeltaS(++)(scr) = 1 +/- 4 eu) scrambles hydrogen atoms of 1 between the methyl and hydride positions, as confirmed by monitoring the equilibration of kappa(3)-Tp(Me)()2Pt(IV)(CH(3))(2)D (1-d(1)()) with its scrambled isotopomer, kappa(3)-Tp(Me)2Pt(IV)(CH(3))(CH(2)D)H (1-d(1'). The sigma-methane complex kappa(2)-Tp(Me)2Pt(II)(CH(3))(CH(4)) is proposed as a common intermediate in both the scrambling and reductive elimination processes. Kinetic results are consistent with rate-determining dissociative loss of methane from this intermediate to produce the coordinatively unsaturated intermediate [Tp(Me)2Pt(II)(CH(3))], which reacts rapidly with solvent. The difference in activation enthalpies for the H/D scrambling and C-H reductive elimination provides a lower limit for the binding enthalpy of methane to [Tp(Me)2Pt(II)(CH(3))] of 9 +/- 2 kcal/mol.     

Chemiluminescent Carbapenem-Based Molecular Probe for Detection of Carbapenemase Activity in Live Bacteria

Carbapenemase-producing organisms (CPOs) pose a severe threat to antibacterial treatment due to the acquisition of antibiotic resistance. This resistance can be largely attributed to the antibiotic-hydrolyzing enzymes that the bacteria produce. Current carbapenem “wonder drugs”, such as doripenem, ertapenem, meropenem, imipenem, and so on, are resistant to regular β-lactamases, but susceptible to carbapenemases. Even worse, extended exposure of bacteria to these drugs accelerates the spread of resistance genes. In order to preserve the clinical efficacy of antibacterial treatment, carbapenem drugs should be carefully regulated and deployed only in cases of a CPO infection. Early diagnosis is therefore of paramount importance. Herein, we report the design, synthesis, and activity of the first carbapenemase-sensitive chemiluminescent probe, CPCL , which may be used to monitor CPO activity. The design of our probe enables enzymatic cleavage of the carbapenem core, which is followed by a facile 1,8-elimination process and the emission of green light through rapid chemical excitation. We have demonstrated the ability of the probe to detect a number of clinically relevant carbapenemases and the successful identification of CPO present in bacterial cultures, such as those used for clinical diagnosis. We believe that our use of “turn-on” chemiluminescence activation will find significant application in future diagnostic assays and improve antibacterial treatment.     

Investigating pressure effects on structural and dynamical properties of liquid methanol with many-body interactions

Molecular-dynamics simulations utilizing a many-body potential was used to study the pressure dependence of structural and dynamical properties for liquid methanol. The liquid density as a function of pressure agreed well with experiment, and a combination of radial and angular distribution functions were used to analyze molecular structure. From these distribution functions, it was observed that hydrogen bond strength increased with increasing pressure. This observation coincided with an increase in the molecular dipole as a function of pressure, having a significant effect on the observed increased hydrogen bond strength. Also, methanols were found to more strongly favor exactly two hydrogen bonds, with fewer methanols of zero, one, or three hydrogen bonds present at higher pressures. Furthermore, a majority of the compression with increased pressure was found to occur in regions perpendicular to the methanol hydrogen-oxygen bond vector. This was the case despite hydrogen-oxygen nonbonded distances between hydrogen bonding species being shorter, but their stiffer oxygen-hydrogen-(nonbonded) oxygen angle offsets this, resulting in their oxygen-oxygen distances being relatively unaffected. The methanol translational diffusion decreased significantly with increased pressure, while the rotational diffusion decreased at a similar magnitude around the oxygen-hydrogen and oxygen-carbon bond vectors, despite having very different overall diffusion. Finally, the hydrogen bond lifetime increased significantly with pressure, owing to the increased hydrogen bond strength, and the slower translational and rotational dynamics.