The characterization of modified silica-alumina catalysts active in the synthesis of picolines

The SiO₂–Al₂O₃ catalyst is modified by promoters like Pb, Cr, Cu. The SiO₂–Al₂O₃ catalyst is also modified using two elements by a simultaneous or stepwise impregnation method. The catalysts are characterized by XRD, IR and ESR techniques, and are useful in the synthesis of picolines.IICT Communication No. 3514, decicated to Dr. A.V. Rama Rao on his 60th birthday.     

Paradigms and Paradoxes: Resonance Stabilization in Diazophenoxides (Quinone Diazides)

Diazophenoxides (quinone diazides) constitute an interesting class of compounds that are seemingly high-energy species on the nonaromatic/aromatic interface. With appropriate substitution and/or annelation, they have found use in the fields of explosives, medicine, and photolithography. Thermochemical information about them is sparse. To aid further understanding of these important chemical species, the current paper discusses a few extant enthalpies of formation from which we tentatively derive a resonance energy of ca. 15 kJ-mol^–1 for the parent, p-species, 4-diazo-2,5-cyclohexadiene-1-one. Interestingly, this value is nearly identical to that recently found for the likewise conjugated diazo compound, ethyl diazoacetate.     

Microstructure of polycarbonate seen by positrons as an in-situ probe

Positron Annihilation Lifetime Spectroscopy (PALS) is used to probe the micro-structural changes in the polymer polycarbonate in terms of the changes in free volume hole size and their content as a function of temperature. The measured spectra are best fitted to three lifetime component analysis. The average hole size in the amorphous regions is determined from the measured Ortho Positronium (O-Ps) lifetime ₃ by following the treatment of Nakanishi et al. On the other hand, information about defects in the crystalline regions is revealed by trapped positrons lifetime ₂. In this polymer the average hole radius varies from 2.71 Å to 2.77 Å. The present study indicates that this polymer has a glass transition temperature of 152°C. Further, we have calculated the trapping rates in the ordered and disordered regions of the polymer based on Goldanskii's kinetic equations and an attempt is made for the first time to estimate the activation energy in the amorphous and crystalline regions separately.     

6-amino-1H-pyrrolo[3,2-c]pyridin-4(5H)-one (3,7-dideazaguanine)

The synthesis of 6-amino-1H-pyrrolo[3,2-c]pyridin-4(5H)-one (3,7-dideazaguanine) from the ammonium chloride promoted reaction of 3-(ethoxycarbonyl)pyrrole-2-acetonitrile and ammonia is reported. Several preliminary reactions which led to this synthetic route are also described.     

Raman Spectroscopy and Fluorescence Photon Migration for Breast Cancer Diagnosis and Imaging

We are developing optical methods based on near infra-red Raman spectroscopy and fluorescence photon migration for diagnosis and localization of breast cancer. We demonstrate the ability of Raman spectroscopy to classify accurately normal, benign and malignant breast tissues, an important step in developing Raman spectroscopic needle probes as a tool for improving the accuracy of needle biopsy. We also show that photon migration imaging can be used to localize accurately small fluorescent objects imbedded in a thick turbid medium with realistic optical properties, thus demonstrating the potential of this technique for optical imaging.     

Effective and noneffective results on certain arithmetical functions

Some Ω results are proved in this paper. It suffices to state a particular result. Write D(n) for the number of square free divisors of n. Next put

$\text{∑}\text{n=1}\text{N}\text{D(n)?}\text{x}\text{ζ(2)}\text{×}\text{log}\text{x +}\text{2y ? 1 ?}\text{2ζ(2)}\text{ζ(2)}\text{= E(x)}$

, where N is the integral part of x. Given any ? > 0 we define explicitly a sequence of intervals in each of which max $\text{|E(x)|x}{}^{\mathrm{<mtext>?1</mtext><mtext>4</mtext><mtext>+?</mtext>}}\text{> 1}$.     

Oxidative coupling of methane in porous Vycor membrane reactors

Porous Vycor membrane tubes were used in shell-and-tube type membrane reactors to study the effect on the oxidative coupling of methane of metering the oxygen into the catalyst bed. Experimental studies showed that under conditions of complete oxygen conversion, Vycor membrane reactors packed with Sm₂O₃ catalyst exhibited enhanced hydrocarbon (C₂) selectivity. C₂ yields were comparable to those of the conventional co-feed packed bed reactors operated under the same conditions. The higher C₂ selectivity in the membrane reactors indicated that, for methane coupling, regulating the supply of oxygen along the length of the packed bed may be beneficial to C₂ formation.     

Some Results of the Finite Deflection Analysis of Clamped Skew Sandwich Plates

The suitability of Galerkin's method for the solution of the problem of the finite deflection analysis of clamped skew sandwich plates is studied. The five coupled nonlinear governing differential equations for sandwich plates are transformed into nonlinear algebraic equations by using Galerkin's method of error minimization. These equations are then solved using an iterative algorithm suggested by Brown. Comparisons of the results of the present analysis with available solutions show good agreement. Numerical results are presented for skew sandwich plates for a wide range of values of the core modulus for different skew angles and aspect ratios. Simplicity in formulation and computation is the advantage of the method as compared with other methods of nonlinear analysis. Computing time and memory requirements in a digital computer are relatively very small, which makes the method attractive.