Photodissociation of cyclobutyl bromide at 234 nm studied using velocity map imaging

This study investigates the 234 nm photodissociation dynamics of cyclobutyl bromide using a two-dimensional photofragment velocity imaging technique. The spin-orbit ground- and excited-state Br(2P) atoms are state-selectively detected via [2+1] resonance enhanced multiphoton ionization (REMPI), whereas the cyclobutyl radicals are ionized using 157 nm laser light. The Br(2P(3/2)) and the Br(2P(1/2)) atoms and their c-C4H7 radical cofragments evidence a single-peaked, Gaussian-shaped translational energy distribution ranging from approximately 14 to approximately 39 kcal/mol and angular distributions with significant parallel character. The Br(2P(1/2))/ Br(2P(3/2)) spin-orbit branching ratio is determined to be 0.11 +/- 0.07 by momentum match between the Br(2P) photofragments and the recoiling c-C4H7 fragments, assuming a uniform photoionization probability of the c-C4H7 radicals with an internal energy range of 10-35 kcal/mol. The REMPI line strength ratio for the detection of Br(2P(3/2)) and Br(2P(1/2)) atoms at 233.681 and 234.021 nm, respectively, is therefore derived to be 0.10 +/- 0.07. The measured recoil kinetic energies of the c-C4H7 radicals, and the resulting distribution of internal energies, indicates some of the radicals are formed with total internal energies above the barrier to isomerization and subsequent dissociation, but our analysis indicates they may be stable due to the substantial fraction of the internal energy which is partitioned to rotational energy of the radicals.     

Physical mechanisms behind the SERS enhancement of pyramidal pit substrates

In this paper we theoretically consider the physical mechanisms behind the surface‐enhanced Raman scattering (SERS) enhancement produced by commercially available Klarite substrates, which consist of rectangular arrays of micrometre‐sized pyramidal pits in silicon with a thin gold coating. Full three‐dimensional numerical simulations of the pits are conducted for both a real gold metal coating and a perfect electrical conductor (PEC) to determine whether the SERS enhancement is due to diffraction or plasmon effects. The pit apex angle and metal coating thickness are also varied to determine whether it is possible to further enhance the SERS signal by optimising the structural parameters of these substrates. By decreasing the film thickness and adjusting the apex angle, it is possible to achieve an enhancement almost double that of a standard Klarite substrate. Copyright © 2010 John Wiley & Sons, Ltd.     

Diethyl-2,2′-bipyridyl-palladium(II), a case for the study of combination vs. disproportionation products.

Diethyl-2,2′-bipyridyl-palladium(II) is synthesized and its decomposition reactions in absence and presence of methyl acrylate are compared with those of the corresponding nickel and platinum complexes. Depending on the reaction conditions either CC-coupling or disproportionation can be induced.     

Constrained stochastic controllability of infinite-dimensional linear systems

The main purpose of this article is to investigate the problem of (ε, δ)-stochastic controllability for linear systems of evolution type in infinite-dimensional spaces, wherein the controls are subjected to norm-bounded constrained sets. Some basic prerequisites of infinite-dimensional measures, in particular, Gaussian distributed type, are discussed. Corresponding to this measure, various properties of (ε, δ)-stochastic attainable sets in Hilbert spaces are studied. Necessary and sufficient conditions for (ε, δ)-stochastic controllability with respect to Hilbert space valued linear systems are obtained. Relationships with the deterministic counterpoint are noted. Pursuit game problems are also considered. Examples on systems governed by stochastic linear partial differential equations and stochastic differential delay equations are given for illustration.     

Differential scanning calorimetry—thin layer chromatography study of ribonucleosides

Thermal mutagenesis has been associated with cleavage of the glycosidic bond and modification of the base structure. Using deoxynucleosides as models, thermal analysis has been utilized to determine the influence of structure on relative ease of these thermolysis reactions. Differential enthalpic analyses of series of crystalline ribonucleosides indicate that they are more resistent to glycosidic cleavage than are the corresponding 2′—deoxyribonucleosides. This difference in thermal stability is attributed to the retarding influence of the 2′-hydroxyl group on the initiation of ion pair formation in the proposed cyclic transition state. Cytosine exhibits a unique behavior insofar as partial deamination of the base occurs, subsequent to cleavage from the sugar, to yield uracil as indicated by a combined DSC-TLC analysis.     

Oxidation of aromatic bis-amides by thallium (III) trifluoroacetate

Aromatic 1,2-bisamides undergo thallium (III) promoted oxidative intramolecular cyclization to generate new 5-membered heterocyclic rings. Formation of $\text{para}$-quinone was shown to be a minor pathway in one case.     

Trivalent cobalt in nickel-zinc ferrites—I. chemical problems

By using special preparation techniques the amounts of trivalent cobalt present in irondeficient Ni-Zn-Co ferrites have been varied.Co³⁺ concentrations have been measured very accurately by careful chemical analyses. It has been shown that under normal sintering conditions, e.g. 1200°C in oxygen, the amount of Co³⁺ just compensates the iron deficiency. The cation vacancy concentration is low. Cation vacancies are formed at lower temperatures near pores and grain boundaries.     

The stereospecific synthesis of leukotriene A4 (LTA4), 5-epi-LTA4, 6-epi-LTA4 and 5-epi,6-epi-LTA4

The stereospecific syntheses of the four isomers of 6-formyl-5,6-epoxy hexanoic acid methyl ester $\text{8}$, $\text{15}$, $\text{23}$ and $\text{30}$ from Z-deoxy-D-ribose have allowed the preparation of methyl esters of LTA₄, $\text{1}$, and its three unnatural isomers.     

Subconvexity bounds for Rankin–Selberg L-functions for congruence subgroups

Estimation of shifted sums of Fourier coefficients of cusp forms plays crucial roles in analytic number theory. Its known region of holomorphy and bounds, however, depend on bounds toward the general Ramanujan conjecture. In this article, we extended such a shifted sum meromorphically to a larger half plane Res>1/2 and proved a better bound. As an application, we then proved a subconvexity bound for Rankin–Selberg L-functions which does not rely on bounds toward the Ramanujan conjecture: Let f be either a holomorphic cusp form of weight k, or a Maass cusp form with Laplace eigenvalue 1/4+k², for . Let g be a fixed holomorphic or Maass cusp form. What we obtained is the following bound for the L-function L(s,fg) in the k aspect:

L(1/2+it,fg)k^{1−1/(8+4θ)+ε},