Raman spectroscopic determination of inosine nucleoside in nucleotides

Raman spectroscopy has been applied to the analytical determination of inosine nucleoside in nucleotides. Spectral characteristics of aqueous solutions of lithium, potassium and magnesium salts of inosine 5'-monophosphoric acid are described. Two characteristic bands located at 1553 and 1593 cm(-1) whose frequencies are not sensitive either to the nucleotide concentration or to alkaline cations present in the medium, have been used for this purpose. The concentration ranges over which the method was applicable were 2.5-80 and 11.5-80 mg ml(-1) of inosine using the 1553 and 1593 cm(-1) bands, respectively, with relative standard deviations of 2.5 and 4.0% and detection limits of 0.25 and 1.16% (w/w). As the above bands are not generated by the standard nucleobases, this method can be applied to the quantitative determination of inosine in transfer ribonucleic acids.     

Quasi-equilibrium volume changes of polyaniline films upon redox switching. Formal potential distribution and configurational modeling

The quasi-equilibrium electrochemomechanical behavior of relatively thick polyaniline films in sulfuric acid is investigated through experimental measurements and theoretical modeling. The leucoemeraldine (LE)-emeraldine (EM) conversion, or redox switching, is studied. The dependence of film volume and electrochemical charge is determined as a function of applied potential. It is observed that the film volume follows the charge, showing an expansion during the second half of the LE-EM oxidation. The model postulates the existence of a stable intermediate, protoemeraldine (PE), with a formal potential distribution for the PE-EM reaction. The volume change is modeled statistically considering contributions from mixing, polymer deformation, and electrostatic charge. The model shows very good agreement with the experiments, indicating that, in the conditions studied, the deformation contribution dominates the volume changes as a result of the conformational modifications undergone by the polymer in the PE-EM oxidation.     

Edge-enhanced imaging with polyvinyl alcohol/acrylamide photopolymer gratings

We demonstrate edge-enhanced imaging produced by volume phase gratings recorded on a polyvinyl alcohol/acrylamide photopolymer. Bragg diffraction, exhibited by volume gratings, modifies the impulse response of the imaging system, facilitating spatial filtering operations with no need for a physical Fourier plane. We demonstrate that Kogelnik's coupled-wave theory can be used to calculate the transfer function for the transmitted and the diffracted orders. The experimental and simulated results agree, and they demonstrate the feasibility of our proposal.     

Study of the action of flavonoids on xanthine-oxidase by molecular topology

A study was performed on xanthine-oxidase inhibition by 22 flavonoids, including flavones, flavonols, flavanones, and chalcones, using UV spectroscopy for experimental data and molecular topology to establish the structure-activity relationship (SAR) model. The flavonoids were classified into four groups according to their activity on xanthine-oxidase (inactive, low, significant, or high), and linear discriminant analysis was used to classify each compound within a group. The results led to a very good model, which was able to classify correctly as xanthine oxidase inhibitors, along with a test set of molecules including a variety of different compounds such as allopurinol, caffeic acid, esculetin, and alloxantin.     

Synthesis of (Z)-3-Deoxy-3-(1,2,3,6-Tetradeoxy-3,6-Imino-L-Arabino-Hexitol-1-C-Ylidene)-D-Xylo-Hexose Derivatives. First Examples Of Homo-(1→3)-C-Linked Iminodisaccharides.

ABSTRACT

Cross-aldolisation of 3,6-[(tert-butoxy)carbonyl]imino-2,3,6-trideoxy-4,5-O-isopropylidene-L-arabino-hexose (10) with 1,6-anhydro-2-O-benzyl-3-deoxy-β-D-erythro-hexopyrano-4-ulose (6) generates, after water elimination, a single enone 11 that is reduced selectively into an allylic alcohol 12, deprotection of which affords methyl (Z)-3-deoxy-3-(1,2,3,6-tetradeoxy-3,6-imino-L-arabino-hexitol-1-C-ylidene)-β-D-xylo-hexofuranoside (1) and (Z)-1,6-anhydro-3-deoxy-3-(1,2,3,6-tetradeoxy-3,6-imino-L-arabino-hexitol-1-C-ylidene)-β-D-xylo-hexopyranose (14).     

Mathematical modeling of extension of an inhomogeneous elastic cloth

We propose mathematical models for a knitted fabric in tension that can be used to calculate the strain of the cloth thread from the properties of the cloth and the loads applied to the cloth. Under simplifying assumptions, the problem is reduced to consideration of an elementary cell of the cloth that contains a thread loop. The loop is first modeled by a thread oval with point forces and then by a plate with a hole under distributed loads. In strength analysis, this allows one to use methods of elasticity theory. A number of hypotheses are used to establish the relation between the stress state of the thread oval and the corresponding state of the plate, which makes it possible to model the mechanical behavior of a thread in the material in a variety of forms. The theoretical relationships obtained are compared to the experimental data available in the literature. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 5, pp. 227–238, September–October, 1999.     

Algebras of quotients of path algebras

Leavitt path algebras are shown to be algebras of right quotients of their corresponding path algebras. Using this fact we obtain maximal algebras of right quotients from those (Leavitt) path algebras whose associated graph satisfies that every vertex connects to a line point (equivalently, the Leavitt path algebra has essential socle). We also introduce and characterize the algebraic counterpart of Toeplitz algebras.