A New Method of Making Titania Gels and Their Microstructure

The reaction of H₂O₂ with alkoxides results in aerohydro gels of titania. These gels appear to form by a complex polymerization process involving peroxy species. The gels are porous and appear to have a fibrillar microstructure.     

Nonlinear Variation of Refractive Index of Vitreous Silica with Pressure to 7 Kbars

The variation of refractive index of vitreous silica with purely hydrostatic pressure to 7 kbars was determined from the shift of the localized interference fringes across the specimen kept in an optical pressure bomb. Allowance for the change in the thickness of the specimen was made with the help of Murnaghan's finite-strain theory and the recently determined third-order elastic constants. The refractive index for λ 5893 A increases linearly with pressure with a slope of 9.2 × 10⁻⁴/kbar up to 4 kbars; thereafter it increases nonlinearly. The increase in the refractive index, however, is linear with respect to the Lagrangian strain in the range investigated, except for a slight tendency for departure from linearity at the highest pressures. No hysteresis effects caused by permanent densification were noted. The results are interpreted in the light of Mueller's theory of photoelasticity of amorphous solids.     

Low-Temperature Equilibria Among ZrO2, Tho2, and UO2

Studies made on low-hafnium-content ZrO₂, show that the monoclinic-tetragonal inversion temperature is 1170°C., and it is raised to approximately 1190°C. in the "natural" ZrO², which contains approximately 2% HfO₂. No explanation could be found for the knownmarked hysteresis during cooling, when the reverse polymorphic transformation takes dace at 1040°C. In the system ZrO₂-ThO₂ the monoclinic-tetragonal ZrO₂, inversion temperature is lowered to 1000°C., although the maximum solid solution extent of ZrO₂, in Thon and vice versa is approximately only 2% at this temperature. Below about 400°C. under hydrothermal conditions it was possible to prepare a continuous, although metastable series of solid solutions with the fluorite structurewith compositions varying from ThO₂, to nearly pure ZrO₂. Contrary to earlier work only 8 mole ZrO₂, dissolves in UO₂ and less than 4 mole of UO, in ZrO₂ at temperatures up to 13OO0C. A continuous series of solid solutions could be made between Th₂ and UO₂ at 13OO°C., and extensive defect fluorite solid solutions could be prepared between Tho₂ and U₃O₈; there is some evidence for exsolution into uranium-rich and thorium-rich members at low temperatures.     

Synthesis and characterization of stable aqueous dispersions of graphene

A stable aqueous dispersion (5 mg ml^?1) of graphene was synthesized by a simple protocol based on three-step reduction of graphene oxide (GO) dispersion synthesized using the modified version of Hummers and Offeman method. Reduction of GO was carried out using sodium borohydride, hydrazine hydrate and dimethyl hydrazine as reducing agents. The chemically synthesized graphene was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible absorption spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopy, thermogravimetric analysis (TGA), optical microscopy. The stability of aqueous dispersions of graphene was confirmed through zeta potential measurements and the negative zeta potentials of 55–60 mV were obtained indicating the high stability of aqueous graphene dispersions.     

Fuzzy set theoretic approach of assigning weights to objectives in multieriteria decision making

A rational procedure is developed for ranking the multiobjectives of a vector maximum problem, thereby leading to proper assignment of weights to the objectives. To achieve this, we determine the range of each decision variable from the constraints set and transform them into the unit interval. After scaling the decision variables, we scale down the objectives also into the unit interval. Following Yager (1981), an ordering function of the objectives is determined. This ordering function value is nothing but the strength of preference inherent in the objectives. Accepting the strength of preference, we obtain the weights for the respective objectives. A numerical example is given to illustrate the procedure.     

Modelling and simulation of combinational digital circuits using Petri nets

The P-model approach of modeling a combinational digital network using Petri nets is introduced. In this model a given logic circuit its represented by a graph With only two types of nodes, places and transitions. A logic 1 value in any line of the circuit corresponds to the presence of a so-called token, and a logic 0 corresponds to the absence of tokens, in the corresponding place of the P-model. The operation of the circuit is reflected in the execution of the P-model resulting from the firing of transitions. Several minimizing transformations in the P-model domain are discussed, which reduces the number of places and transitions by an order of magnitude. Based on this P-model representation of a logic circuit, a logic simulation algorithm is outlined. The method is faster and also simpler to implement than conventional simulation techniques.     

Changes in wild ass (Equus hemionus khur) habitat conditions in Little Rann of Kutch,Gujarat from a remote sensing perspective

The Rann of Kutch, Gujarat is the only habitat for one of the endangered sub-species of the Asiatic wild ass (Equus hemionus khur) and most of the population survives in the Wild Ass Sanctuary in Little Rann of Kutch. The area is a saline desert with extremely sparse cover of vegetation. In the past, the habitat supported a thriving population of wild asses. However, due to extensive changes in the land-use around the Rann of Kutch, there has been an increase in the conflict of interests between man and the wild ass. The present paper seeks to analyse the situation with respect to changes in land-use, vegetation cover and salt cultivation to plan proper habitat management inside the sanctuary to mitigate the problem of crop predation by the wild ass through the use of high resolution satellite data.

The Survey of India (SOI) topographic maps of 1960 vintage were used to estimate the past habitat, land-use, vegetal cover and salt fields. The SOI topographic maps and false colour composites provided a limited number of land-use classes for a meaningful comparison of land-use changes. This data has been compared with digitally classified SPOT MLA on SIPS (Satellite Image Processing System, Hyderabad). Various techniques such as principal component analysis, normalized difference vegetation index, unsupervised and supervised classifications were carried to classify various features. Of these techniques, supervised classification provided very useful results for an effective interpretation. It was observed that there has been an increase in irrigated crop fields. This has resulted in enhanced crop predation by wild asses thereby triggering human-wild ass conflicts. The digital interpretation provided crucial information on a number of classes of land-use relevant to the habitat of wild ass. An operational basis of deriving such information for formulating effective conservation strategies is presented.     

Tropical forest typo mapping and monitoring using remote sensing

Abstract

The Andaman Nicobar group of islands in the Andaman Sea are blessed with luxuriant tropical vegetation. During recent years, vegetation in these islands has been under tremendous pressure due to increased settlement and commercial extraction, Landsat TM data of the Baratang forest division of the Andaman group of islands has been used to prepare forest type maps using visual and digital methods. Digital enhancement techniques have been evaluated to discriminate forest types in a typical environmental set-up. The mapping techniques have been compared with respect to classification and accuracy levels. Finally, the land transformation in the forest division has been studied using past aerial photographs. The study highlights the appropriate methodology required to map forest types.     

Translational aspects of the modern genetics in head and neck cancers

Oral Cancer (OC) is one of the most recurrent cancers in the head and neck squamous cancer (SCCHN) category. Recently, the genome-wide association studies (GWAS) have gained growing interest in the scientific community. GWAS have identified several pathways involved in the interactions among general risk factors and genomic variants affecting SCCHN. This systematic overview aims to critically evaluate the latest data reported within the scientific literature. The aim was to investigate the impact of genetic aspects on SCCHN onset and prognosis, involving other clinical and systemic co-factors. PubMed, Google Scholar, and Cancer Genetics Web databases have been systematically investigated for original articles published in the last two years, reporting studies on the main queries addressed in this work. This review also comparatively describes the impact of environmental and pathological co-factors in different types of cancers, clarifying and updating the role of genetic factors in SCCHN onset and development. The main outcomes reported may be helpful to drive clinicians towards their clinical evaluations for the most appropriate therapeutic approach in SCCHN.     

Rare-Earth Polymorphism and Phase Equilibria in Rare-Earth Oxide-Water Systems

A high-water-pressure high-temperature study has been conducted of the systems Y₂O₃-H₂O, Sm₂O₃-H₂O, Nd₂O₃-H₂O, and La₂O₃-H₂O. The trihydroxides La(OH)₃, Nd(OH)₃, and Sm(OH)₃ are isomorphous, but Y(OH)₃ does not belong to this group. On the other hand, the oxyhydroxides YOOH, SmOOH, and NdOOH are isomorphous; LaOOH, if it exists, cannot be stable in the presence of water at room temperature. Pressure-temperature curves for the equilibrium between the trihydroxide, oxyhydroxide, and a new hydroxy compound have been determined for each of the three smaller ions. The reversibility of the transition between the A-, B-, and C-type rare earths has been established, and new X-ray data on the B structure are listed. The relations between the polymorphs as a function of ionic size are changed from those given by Goldschmidt. The very marked difference in stability in air between the A- and C-type structures suggests the obvious desirability of converting rare-earth oxide ceramics into the C structure with proper compositional variation and thermal treatment.