Rapid crack growth in a thermoelastic solid under mixed-mode thermomechanical loading

A two-dimensional steady-sate analysis of semi-infinite brittlecrack growth at a constant subcritical rate in an unboundedfully-coupled thermoelastic solid under mixed-mode thermomechanicalloading is made. The loading consists of normal and shear tractionsand heat fluxes applied as point sources (line loads in theout-of-plane direction). A related problem is solved exactly in an integral transformspace, and robust asymptotic forms used to reduce the originalproblem to a set of integral equations. The equations are partiallycoupled and exhibit operators of both Cauchy and Abel types,yet can be solved analytically. The temperature change field at a distance from the moving crackedge is then constructed, and its dominant term is found tobe controlled by the imposed heat fluxes. The role of this termis, indeed, enhanced if the heat fluxes serve to render thecrack as a net heat source/sink for the solid, as opposed tobeing a transmitter of heat across its plane. More generally,the influence of the thermoelastic coupling on this field, aswell as other functions, is found to increase with crack speed.     

A long-wavelength biolabeling reagent based on the oxonol fluorophore

A red fluorescent dye of the oxonol class, bis-[1-(carboxymethyl)barbituric acid-(5)]-pentamethinoxonol, has been synthesized and, in the form of the succinimidyl active ester, has been applied to antibody labeling for application to flow cytometry and to imaging of tissue sections. The new dye, named CMOX (for carboxymethyloxonol), shows maximum excitation at 583 nm and emission at 611 nm, with a quantum yield of 0.2 in aqueous buffer and methanol. Antibodies labeled with the new dye show favorable brightness, photostability, and low levels of nonspecific binding.     

Compounds in the pyrrolo[3,4-d]pyrimidine series. derivatives with 6-aryl substituents

Methods are described for the synthesis of 6,7-dihydro-5H-pyrrolo[3,4-d]pyrimidines having an aryl substituent in the 6-position. 4-Hydroxy-, 4-amino, 2-amino-4-hydroxy and 2,4-diamino derivatives were obtained. The synthetic route involved the preparation of 1-aryl-4-cyano- or 4-carboalkoxy-3-pyrrolidinones and 1-aryl-4-cyano- or 4-carboalkoxy-3-amino-3-pyrrolines as key intermediates.     

Preparation of monoacylpyrazines

Homolytic acylation of pyrazine and alkylpyrazines by aldehydes, as a source of an acyl radical, gives mainly monoacylation products. The reactions proceed in reasonable yields and provide a new route to pyrazine ketones.     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.     

Dynamical behavior of xanthan polysaccharide in solution

Dilute-solution hydrodynamic data for xanthan biopolymer in water suggest a rodlike molecule of dimensions 15,000 × 20 Å, and molecular weight 2.2 × 10⁶ g/mol. Upon addition of NaCl to this system, the xanthan molecules self-associate to form stable aggregates. The native xanthan conformation can be thermally denatured to a disordered coil which can be stabilized at room temperature in 4M urea. The transition to semidilute solutions is manifested by discrete changes in the concentration dependence of diffusion coefficient and zero-shear viscosity at c ≈ 2.0 × 10^?4 g/mL. At higher concentrations c ≥ 1.0 × 10^?3 g/mL, the light-scattering and shear-viscosity data are qualitatively but not quantitatively consistent with predictions of the dynamical theory of Doi and Edwards for an isotropic entangled solution of rigid-rod molecules. Measurements of latex sphere diffusion in xanthan-water solution show a sudden retardation at c ≈ 1.0 × 10^?3 g/mL, consistent with the cooperative formation of a motionally restricted network of long, thin, rigid fibers. At high shear rates, flow birefringence experiments indicate enhanced ordering of the xanthan chains in the semidilute regime.     

Synthesis of antifols related to 2,4-diamino-6,7-dihydro-5H-pyrrolo[3,4-d] pyrimidine. Enhancement of antiparasitic selectivity by nitrogen-linked mono- and dichlorobenzoyl groups or the 3,4–dichlorophenylthiocarbamoyl group

Improved procedures have been developed for the synthesis of 2,4-diamino-6,7-dihydro-5H-pyrrolo[3,4-d]pyrimidine ( 2a ), its 7-mcthyl derivative ( 2b ), and 6-(chloro-substituted phenyl) derivatives of 2,4-diamino-6,7-dihydro-5H-pyrrolo[3,4-d]pyritnidine ( 4 ). Direct acylation of compounds 2a or 2b with acid chlorides or mixed anhydrides derived from chloro-substituted benzoic or cinnamic acids gave 6-(chloro-substituted benzoyl or cinnamoyl) derivatives. Lithium aluminum hydride reduction of 6-(chloro-substituted benzoyl) derivatives under controlled conditions permitted preparation of 6-(chloro-substituted benzyl) derivatives (3). Compound 2a also reacted with aryl isothiocyanates to yield 6-arylthiocarbamoyl derivatives. Antimalarial assays for in vivo activity against murine malaria (P. berghei) and avian malaria (P. gallinaceum) revealed that a somewhat enhanced in vivo antiparasitic effect above that of parent compound 2a without any evident increase in host toxicity was conferred by introduction of certain of the 6-chloro-substituted benzoyl groups or the 6-(3,4-dichlorophenylthiocarbamoyl) group. Corresponding 6-(chloro-substituted benzyl) derivatives more frequently displayed host toxicity.