Overview of neurocomputers

This paper presents an introduction to neurocomputers and an overview of the history of neurocomputers. Direct implementation methods of neurocomputers using techniques from microelectronics and photonics are discussed. Emulation methods using special-purpose hardware are highlighted. The role of parallel computing systems for improved performance is introduced. Some commercially available neurocomputers and performance issues of such systems are also presented.

Oxidation of substituted benzylic hydrocarbons and naphthalenes by peroxydisulphate in the presence of metal ions

Oxidations of various substituted benzylic hydrocarbons with peroxydisulphate in the presence of metal ion catalysts like iron, nickel, copper, cobalt, silver and cerium were examined. Among the metal ions copper (II) catalysed reaction gives products in excellent yield, whereas oxidation of naphthalene and substituted naphthalenes gives low to moderate yield of the products with peroxydisulphate- copper (II).

Secretion of endocrine signals by the primate embryo during the peri-implantation period

Development of preimplantation embryos and blastocyst implantation are critical early events in the establishment of pregnancy. In primates, embryonic signals, secreted during the peri-implantation period, are believed to play a major role in the regulation of embryonic differentiation and implantation. However, only limited progress has been made in the molecular and functional characterization of embryonic signals, partly due to severe paucity of primate embryos and the lack of optimal culture conditions to obtain viable embryo development. Two embryonic (endocrine) secretions, i.e. chorionic gonadotrophin (CG) and gonadotrophin releasing hormone (GnRH) are being studied. This article reviews the current status of knowledge on the recovery and culture of embryos, their secretion of CG, GnRH and other potential endocrine signals and their regulation and physiological role(s) during the peri-implantation period in primates, including humans.

Some aspects of information processing in biological vision

An attempt is made to present some challenging problems (mainly to the technically minded researchers) in the development of computational models for certain (visual) processes which are executed with, apparently, deceptive ease by the human visual system. However, in the interest of simplicity (and with a nonmathematical audience in mind), the presentation is almost completely devoid of mathematical formalism. Some of the findings in biological vision are presented in order to provoke some approaches to their computational models, The development of ideas is not complete, and the vast literature on biological and computational vision cannot be reviewed here. A related but rather specific aspect of computational vision (namely, detection of edges) has been discussed by Zucker, who brings out some of the difficulties experienced in the classical approaches.Space limitations here preclude any detailed analysis of even the elementary aspects of information processing in biological vision, However, the main purpose of the present paper is to highlight some of the fascinating problems in the frontier area of modelling mathematically the human vision system.

Spatial gradients of calcium in the slug of Dictyostelium discoideum

Starved amoebae of D. discoideum aggregate and give rise to a long and thin multicellular structure called the slug. The cells within the slug eventually differentiate according to a simple anterior/posterior dichotomy. This motivates a search for gradients of putative morphogens along its axis. Calcium may be one such morphogen. On the basis of observations made by using the calcium-sensitive fluorescent dyes fura-2 and chlortetracyline, we report that there are spatial gradients in cytoplasmic and sequestered calcium in the slug. Anteriorly located and genetically defined prestalk cells (ecmA/pstA, ecmB/pstAB) contain significantly higher levels of calcium than the prespore cells in the posterior. However, the proportion of 'calcium-rich' cells in the slug is greater than that of the subset of prestalk cells defined by the expression of the ecmA or ecmB genes.

Structural and Dielectric-Properties Of A Novel BI2O3-(1-X)WO3-XCUO Solid-Solution

A novel solid solution in the system Bi-W-Cu-O has been synthesized and its structural and dielectric properties studied. The solid solution Bi2O3-(1-x)WO3-xCuO exists up to x = 0.7; the solid solutions up to x = 0.65 are orthorhombic but stabilize in tetragonal structure in a narrow range around x = 0.7. The solid solutions are non-centrosymmetric and exhibit ferroelectric behaviour similar to their parent phase Bi2WO6. The Curie point of the solid solution is found to decrease with increase in x.

Synthesis and properties of rare earth doped lamp phosphors

Red, blue and green emitting lamp phosphors such as EU(3+) doped Y2O3 (red phosphor), EU(2+) doped Ba0.64Al12O18.64, BaMgAl10O17 and BaMg2Al16O27 (blue phosphors) and Ce0.67Tb0.33MgAl11O19 and Eu2+, Mn2+ doped BaMgAl10O17 (green phosphors) have been prepared by the combustion of the corresponding metal nitrates (oxidizer) and oxalyl dihydrazide/urea/carbohydrazide (fuel) mixtures at 400 degrees-500 degrees C within 5 min. The formation of these phosphors has been confirmed by their characteristic powder X-ray diffraction patterns and fluorescence spectra. The phosphors showed characteristic emission bands at 611 nm (red emission), 430-450 nm (blue emission) and 515-540 nm (green emission). The fine-particle nature of the combustion derived phosphors has been investigated using powder density, particle size and BET surface area measurements.

The chemistry of a non-natural product: Troger's base

Troger's base was the first amine to be resolved where the chirality was solely due to very high inversion barrier around nitrogen atom(s). Though the molecule was known over a century, work done during the past one decade has shown that Troger's base and its analogues could be used as chiral solvating agents, DNA-binding ligands and for the construction of biomimetic molecular receptors and clathrate hosts, Asymmetric synthesis of Troger's base analogues has also been achieved recently, Because of the rigid, 'V'-shaped chiral nature of this molecule, there is a growing interest for use of this unit in the design of potential host systems, This review article focuses on the chemistry of Troger's base along with the possible future utilities.

The goals of cognitive science

In this paper cognitive science is defined as the study of intelligence as a computational process. The several disciplines which contribute to the study of cognitive science are briefly described so as to glean a birds-eye view of the subject of cognitive science.

Thermal expansion studies of substituted CTP derivatives

Several new Na, Y and Zr substituted derivatives of Ca-0.5 Ti-2(PO4)(3) (CTP) have been synthesized. These derivatives retain the hexagonal structure of the parent (CTP) compound with minor changes in lattice parameters. Linear thermal expansion coefficients (alpha) have been obtained using a high sensitivity dilatometer.