Search for physiologically active compounds

A number of 3-(3-pyridyl) coumarins with and without 4-methyl substituent have been prepared following Oglialoro and modified Perkin reactions. These compounds have been tested against fish and bacteria. Of all the compounds tested, 7-bromo-4-methyl-3-(3-pyridyl) coumarin exhibited maximum activity. A few have also shown bacteriostatic activity.     

Synthesis of some chromono (6, 7) oxazoles and their physiological activity

The synthesis of a few chromono (6, 7) oxazoles has been carried out by condensing 6-amino-8-bromo-7-hydroxy-2-methyl chromone with various aromatic aldehydes in nitrobenzene medium. The ultraviolet and infrared spectral characteristics of these compounds have been described. A study of antibacterial and antifungal activities of these compounds has revealed that 2-m-hydroxyphenyl-7-methyl-9-bromo-chromono (6, 7) oxazole and 2-p-Anisyl-7-methyl-9-bromo-chromono (6, 7) oxazole possess antifungal activity.     

Search for physiologically active compounds

7-Hydroxy-3-methyl 4-phenylcoumarin andα-methyl dihydrofurano,α andγ-pyrono ring systems have been built on 7, 8-position of 4-phenylcoumarin. The bacteriostatic activity of these compounds as well as that of mammeisin and mesuol isolated fromMesua ferrea seeds has been evaluated. Structure-activity relationship among these compounds is discussed.     

The shapes of the LIII X-ray absorption discontinuity of rhenium in compounds

The X-ray L_III absorption edge of rhenium in the pure metal and in two compounds, namely, K₂ReCl₆ and KReO₄ has been studied using a Cauchois type bent crystal spectrograph of 40 cm diameter. The splitting of the main absorption discontinuity has been observed for the first time in the compounds. This splitting and the edge structure of the Re L_III discontinuity in the compounds have been interpreted on the basis of molecular orbital diagrams. The crystal field splitting, Δ, has been determined experimentally in both the compounds in the solid state.     

Microcomputed tomography analysis of ferrofluids used as drug carriers for cancer treatment

Two new approaches, Magnetic Drug Targeting (MDT) and Magnetic Hyperthermia, are being investigated in order to reduce side effects generated by common ways of cancer treatment. MDT and MHT are based on the use of magnetic nanoparticles: for MDT the nanoparticles are used as drug carriers and for MHT the nanoparticles are used to induce local heat transfer within the tumour. The success of these therapeutic approaches depends among other things on the correct distribution of the magnetic nanoparticles within the tumour tissue. Computed tomography analysis has been performed on tumour tissue after MDT in order to examine this distribution. The measurements have been performed in two different laboratories, one based on a synchrotron radiation, and another one on a cone X–ray source. First results show that the drug carriers are contained in the vessel system of the tumour as well as concentrated in the surrounding area of the veins. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies on the relation between chemical constitution and ultraviolet absorption spectra of optically active and racemic compounds

The ultraviolet absorption spectra of camphor-β-sulphonyl-phenyl, (o-, m- andp-) tolyl, (α- and β-) naphthylamides have been determined in methyl alcohol, ethyl alcohol, and chloroform. The absorption spectra of all the compounds show two absorption bands: one varying from 267 to 284 mμ, the longer absorption maximum (λ_max) due to selective absorption of the keto group, and the other shorter one, ranging from 226 to 230 mμ, due to general absorption of the saturated molecules. The values of the characteristic wavelengths, λ₀₈ obtained from Drude’s one-term equation, have been compared with the absorption maxima, λ_max obtained by direct measurements. There are marked discrepancies in the values of λ₀ and λ_max. An explanation of the discrepancies is given. The nature of racemic modifications of the compounds has also been discussed.     

Proton magnetic resonance studies of the association of amino methyl pyridines

Proton magnetic resonance studies of the solutions of (a) 2-amino, 3-methyl pyridine and (b) 2-amino, 6-methyl pyridine in carbontetrachloride show that in these molecules there is an equilibrium between monomers and hydrogen-bonded dimers. The equilibrium constants for the two cases have been obtained. Evidence has also been obtained to show that chloroform forms hydrogen bond with the ring nitrogen of these compounds. These NMR results have been compared with those obtained earlier from infra-red studies.     

Studies in the formation of heterocyclic rings containing nitrogen

Eight representative aromatic aldehydes with hydroxy, methoxy, nitro and chloro substituents have been condensed withs-diphenyl urea and ammonium acetate resulting in 2-keto-1, 3, 4, 6-tetra-aryl-hexahydro-s-triazines. The condensation of phenyl urea with five aldehydes and ammonium acetate, however, gave 1-phenyl-1:3-bis-(α-hydroxy aryl) ureas. The ultra-violet and infra-red spectra of these two types of compounds have been recorded.     

Uniformly convergent scheme for two‐parameter singularly perturbed problems with non‐smooth data

A numerical scheme is constructed for the problems in which the diffusion and convection parameters (?₁ and ?₂ , respectively) both are small, and the convection and source terms have a jump discontinuity in the domain of consideration. Depending on the magnitude of the ratios , and two different cases have been considered separately. Through rigorous analysis, the theoretical error bounds on the singular and regular components of the solution are obtained separately, which shows that in both cases the method is convergent uniformly irrespective of the size of the parameters ?₁, ?₂ . Two test problems are included to validate the theoretical results.     

The 2-(9, 4, 3) and 3-(10, 5, 3) designs

It is shown that there is a unique 2-(9, 4, 3) design with three different extensions to a 3-(10, 5, 3) design. Two of the extensions are isomorphic and have a further extension to the unique 4-(11, 6, 3) design. There is another 2-(9, 4, 3) design with just two extensions to a 3-design. There are 11 2-(9, 4, 3) designs in all, as announced by van Lint, et al. and Stanton et al. There are seven 3-(10, 5, 3) designs of which one is triply transitive, another transitive, and the rest are not transitive but are self-complementary. The transitive 3-designs each have one restriction to a 2-design. Of the non-transitive 3-designs 4 each have two restrictions and the fifth has three.     

Synthesis,spectra and physiological activity of pyrono (2, 3-e) benzoxazoles

A few 2-aryl and 2-heterocyclic substituted pyrono (2, 3-e) benzoxazoles have been synthesized by condensing 8-amino-7-hydroxy-2-methyl chromone with aromatic or heterocyclic carboxylic acids employing polyphosphoric acid as the condensing agent. The ultraviolet, infrared, NMR and mass spectra of these compounds have been presented. Antibacterial evaluation revealed that the 2-naphthyl and 2-(3-coumarinyl) derivatives exhibit considerable activity.     

Isoxazolo (7,8 -d) flavones

A few isoxazolo (7, 8-d) flavones have been synthesised from 7-hydroxy-8-carbonyl flavones by preparing the oximes and cyclising them with sulphuric acid. The ultraviolet, infrared and mass spectra of some of these compounds have been recorded. The antibacterial activity of these derivatives has also been evaluated.     

X-ray spectroscopic study of chemical bonding in NiSe and NiSe2

The K absorption spectra of nickel and selenium have been recorded photographically in the pure metals and the compounds NiSe and NiSe₂. It has been observed that the Ni discontinuity shifts toward the high energy side with respect to that in the pure metal by about 5.0 eV for NiSe and about 6.7 eV for NiSe₂. The Se edge in both these compounds is found to shift by about 2.6 eV toward the low energy side with respect to that in pure selenium. From these results it is possible to obtain the bonding pictures for the compounds. The compound NiSe appears to have resonating p³ type of bonding. For NiSe₂ the orbitals involved in the bonding are d²sp³ for the metal atom and sp³ for the metalloid atom. The electrical behaviour of the compounds has been explained on the basis of these bonding pictures.     

Bootstrap percolation with inhibition

We study a variant of the classical bootstrap percolation process on Erd?s Rényi random graphs. The graphs we consider have inhibitory vertices obstructing the diffusion of activity and excitatory vertices facilitating it. We study both a synchronous and an asynchronous version of the process. Both begin with a small initial set of active vertices, and the activation spreads to all vertices for which the number of excitatory active neighbors exceeds the number of inhibitory active neighbors by a certain amount. We show that in the synchronous process, inhibitory vertices may cause unstable behavior: tiny changes in the size of the starting set can dramatically influence the size of the final active set. We further show that in the asynchronous model the process becomes stable and stops with an active set containing a nontrivial deterministic constant fraction of all vertices. Moreover, we show that percolation occurs significantly faster asynchronously than synchronously.     

New results in equal sums of like powers

This paper reports on new results for the equation

i.e., equal sums of like powers. Since the 1967 Lander, Parkin and Selfridge survey paper [4], few other numeric results have been published (see Elkies [6] and Ekl [3]). The present paper reports on several new smallest primitive solutions. Further, search limits have been extended in many cases, and tables of solutions are presented. Additionally, new solutions to the same class of problems in distinct integers have been discovered.

     

Primitive higher order embeddings of abelian surfaces

In recent years several concepts of higher order embeddings have been studied: -spannedness, -very ampleness and -jet ampleness. In the present note we consider primitive line bundles on abelian surfaces and give numerical criteria which allow to check whether a given ample line bundle satisfies these properties.

     

On a class of weak Tchebycheff systems

In this paper we study the approximation power, the existence of a normalized B-basis and the structure of a degree-raising process for spaces of the formrequiring suitable assumptions on the functions u and v. The results about degree raising are detailed for special spaces of this form which have been recently introduced in the area of CAGD.     

A Fast algorithm to compute cubic fields

We present a very fast algorithm to build up tables of cubic fields. Real cubic fields with discriminant up to and complex cubic fields down to have been computed.

     

Heats of combustion of some symmetrical dialkyl ureas and their corresponding alkyl carbamates

The standard heats of combustion of the disubstituted ureas, N, N′-diheptyl urea, N, N′-dioctyl urea and N, N′-didecyl urea and the carbamates,n-heptyl ammoniumn-heptyl carbamate,n-octylammoniumn-octyl carbamate andn-decyl ammoniumn-decyl carbamate have been determined. The values found are 2353±1·3, 2658·4±1·1, 3268·5±1·7, 2349·8±1·6, 2654·4±1·2, 3264·6±1·8, K.cals. mole^?1 respectively. The heats of formation of these compounds have been calculated.