The effect of vacuum polarisation in the calculation of internal conversion coefficients

The effect of vacuum polarisation on internal conversion coefficients is investigated for the nuclear charge numbersZ=26 andZ=80; it contributes less than one percent to the conversion rate.     

Sample optimization and identification of signal patterns of amino acid side chains in 2D RFDR spectra of the alpha-spectrin SH3 domain

Future structural investigations of proteins by solid-state CPMAS NMR will rely on uniformly labeled protein samples showing spectra with an excellent resolution. NMR samples of the solid alpha-spectrin SH3 domain were generated in four different ways, and their (13)C CPMAS spectra were compared. The spectrum of a [u-(13)C, (15)N]-labeled sample generated by precipitation shows very narrow (13)C signals and resolved scalar carbon-carbon couplings. Linewidths of 16-19 Hz were found for the three alanine C(beta )signals of a selectively labeled [70% 3-(13)C]alanine-enriched SH3 sample. The signal pattern of the isoleucine, of all prolines, valines, alanines, and serines, and of three of the four threonines were identified in 2D (13)C-(13)C RFDR spectra of the [u-(13)C, (15)N]-labeled SH3 sample. A comparison of the (13)C chemical shifts of the found signal patterns with the (13)C assignment obtained in solution shows an intriguing match.     

Counter-current chromatography based analysis of synergy in an anti-tuberculosis ethnobotanical

The crude extract of an Alaskan ethnobotanical plant, Oplopanax horridus, was subjected to counter-current chromatography (CCC), and the selected active regions were evaluated for their synergistic effects with an in vitro model of anti-tubercular efficacy. CCC as a support-free high-resolution separation method was employed to preclude potential irreversible absorption to a solid stationary phase. The microplate Alamar blue assay and the isobole method were used to measure the biological activity and eliminate dose-response dependent errors, respectively. Using the combination of CCC, bioassay and isobole method, significant synergistic effects were observed. Among the entire polarity range, fractions with distribution constant between 0.44 and 0.81 showed the most synergistic enhancement with an increase in potency by 108% for the recombined fractions.     

Aluminum speciation and thermal evolution of aluminas resulting from modified Yoldas sols

Aluminas resulting from sols prepared via a modified Yoldas procedure were studied with differential thermal analysis (DTA), differential thermal gravimetrie (DTG), ²⁷Al nuclear magnetic resonance (²⁷Al MAS NMR) and X-ray diffraction (XRD) concerning their thermal properties, aluminum speciation and phase content.Hydrolysis of aluminum-sec-butoxide in aluminum nitrate solutions allowed to prepare stable sols with varying molar ratios, solids contents and pH values. Resulting sols contained different aluminum species including also Al₁₃ polycations. Sol preparation conditions also determined aluminum speciation in solid products obtained after thermal treatments of gels obtained from these sols. Al₁₃ polycations and AlO₅ species were found to play an important role for thermally induced transformation from amorphous products via eta-Al₂O₃ to alpha-Al₂O₃. Intermediately formed eta-Al₂O₃ promotes the phase transformation to alpha-Al₂O₃.     

A Note on Design of Fiber-Nets for Maximum Stiffness

For a specific fiber-net, the design variables are relative fiber density and fiber orientations. With a given amount of fibers, our objective is to maximize the stiffness (minimize the compliance) for a continuum subjected to a given load situation. Analytical optimality criteria are derived, and numerical optimization procedures are presented. Applications to a wedge problem from the literature, Royer-Carfagni (2000), and to a skew plate problem are shown, and the study includes the influence of a basic material to be reinforced. The procedure described can be combined with localized optimal design for density, orientation, and shape, “pointwise” or for design regions.     

Syntheses and reactions of some fluorinated dienes,cyclobutenes and furans

There are many reports¹ of the pyrolysis of fluorinated organic compounds, including the defluorination of cyclic fluorocarbons over iron to give aromatic compounds. Extending this technique we have investigated the flow pyrolysis of some readily accessible unsaturated fluorocarbons, such as I, II, and III, and found these to be synthetically

useful routes to fluorinated dienes, cyclobutenes, and furans. Pyrolyses were carried out using a nitrogen flow over platinum, iron or caesium fluoride heated at 430–700°. The various products can all be rationalized in terms of intermediate allylic radicals, and the solid substrate influences which allylic radicals are formed.We are also investigating the chemistry of those now accessible compounds, such as IV, V, and VI, and some of the preliminary results are described.

For example the fluoride ion induced dimerisation of IV gave two major products VII and VIII via a particular interesting mechanism.

     

A simple approach to the nuclear dynamics

We propose an approach to the nuclear dynamics which enables us to understand the relations between the time-dependent Hartree-Fock method and the quantumstatistical approach to the heavy ion reactions. The same formalism allows us to generalize the random phase approximation in order to include the spreading width of collective states.     

Discretized light cone quantization in a 3+1 dimensional valence model for quarkonium

Led by successes of the nonperturbative method of discretized light cone quantization (DLCQ) in 1+1-dimensional toy models, we study the feasibility of extending it to 3+1 dimensional theories. Within aSU(N _c ) nonabelian gauge theory, DLCQ is applied to a quarkonium system, where the Fock space has been truncated to the valence quark and antiquark only. In the light cone gauge the valenceq \(\bar q\) -model Hamiltonian matrix has an interesting structure which enables us to reduce the problem of diagonalization of some extremely large matrices to an amount of numerical labor already coped with in 1+1 dimensions. The model spectrum and the eigenfunctions are calculated independent of the order of the nonabelian gauge group, in special cases even analytically. The type of spectrum which appears after the calculation has been regularized covariantly may be interpreted as a sign that the quarks are confined in this model.