Critical phenomena in FINEMET alloy

The Fe_73.5Cu₁Nb₃Si_13.5B₉ FINEMET alloy has been prepared by the rapid solidification technique. The critical behaviour of this alloy in the amorphous as well as in its nanocrystalline states has been studied near their respective Curie temperatures. From the values of the critical exponents one can conclude that the alloy behaves like a 3D Heisenberg ferromagnet in the amorphous and nanocrystalline states. But there exists a slight increase in the value of β for the alloy annealed at 823 K (the nanocrystalline state) as observed in most of the amorphous alloys.     

PIV studies of large scale structures in the near field of small aspect ratio elliptic Jets

The near flow field of small aspect ratio elliptic turbulent free jets (issuing from nozzle and orifice) was experimentally studied using a 2D PIV Two point velocity correla tions in these jets revealed the extent and orientation of the large scale structures in th e major and minor planes. The spatial filtering of the instantaneous velocity field using Gaussian convolution kernel shows that while a single large vortex ring circumscribing the jet seems to be present at the exit of nozzle, the orifice jet exhibited a number of smaller vortex ring pairs close to jet exit. The smaller length scale observed in the case of the orifice jet is rep resentative of the smaller azimuthal vor tex rings that generate axial vortex field as they are convected. This results in the axis-switching in th e case of orifice jet and may have a mechanism differ ent from the self induction process as observed in the case of contoured nozzle jet flow.     

Working group report: Flavor physics and model building

This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently.     

Subtilisin catalysis of substrate anchored in cyclodextrin

The N-benzoyl-l-tyrosine ethyl ester (BTEE) anchored in cyclodextrin (β and β-methyl CD) serves as an excellent substrate for subtilisin Carlsberg catalysis. The rate of hydrolysis was found to be approximately twofold higher than that of the methanolic substrate. The K_mapp and V_max values for the CD anchored substrates were significantly higher than the methanol-solubilized BTEE.     

Substituted m-phenylene bridges as strong ferromagnetic couplers for Cu(II)-bridge-Cu(II) magnetic interactions: new perspectives

Based on a combined theoretical-experimental study, we propose that substituted m-phenylene ligands (m-N-Phi-N) can act as tuneable strong ferromagnetic couplers connecting Cu(II) ions; a new complex presenting that bridge with J close to +15 cm(-1) has been suggested and synthesized.     

Transport of excitation energy in a doped molecular aggregate. III. numerical investigation of exciton hopping with various exciton-depleting processes

A brute-force numerical investigation has been carried out on the hopping of excitons in a three-dimensional molecular aggregate. Possibilities of vibronic decay, rapid chemical reactions of saturated species, radiative decay of overpopulated molecules, and cooperative chemical reactions involving saturated exciton populations on traps of two different types have been considered. Investigation have been performed with two types of initial distribution of excitons—facial and random—and for 10,000 or, sometimes, for 20,000 time steps each of duration 1ps. Several interesting observations have been made from this computer experiment: (1) The total number of occurrences of fast reactions depends upon the initial distribution of excitons. (2) It decreases if other exciton depleting processes are at work. (3) It also depends on the pattern of placement of traps. (4) The location of impurities also affects the rate of occurrence of these reactions. Thus, more reactions occur when the excitons are initially concentrated on one face and traps are suitably located on the path of flow of these excitons. A random initial distribution tends to equilibrate the excitons quickly over all the lattice points, thus giving rise to fewer reactions. (5) The number of reactions need not necessarily increase with the number of reaction centers; in fact, it decreases as more centers are added when the supply of excitons is severely limited. (6) A Complicated dynamics results when different types of additional processes, viz., enhanced fluorescence, radiative emissions, and cooperative chemical reactions are simultaneously allowed. The cooperative process has been clearly found to dominate. A first-order rate constant of about 10⁸ s-¹ has been calculated for the occurrence of the cooperative process. This rate is affected when other nonconserving processes are switched on. Observations (1), (4), and (5) are the most important conclusions of our work. They lie outside the scope of traditional models such as the random walk model, the diffusion model, and the lattice model for the migration of excitons in a molecular aggregate. © 1993 John Wiley & Sons, Inc.     

Reductive nitrosylation of tetraoxometallates—XVII. Molybdate-hydroxylamine-cyanide reaction, and synthesis and characterization of K2[Mo(NO)(CN)5] and (NMe4)2[Mo(NO)(CN)4]

A reaction condition is established which determines the nature of the products in the molybdate-hydroxylamine-cyanide reaction. With hydroxylamine always used in excess, it is the hydroxyl ion concentration of the reaction mixture which plays a vital role in determining whether K₄[Mo(NO)(CN)₅] or K₂[Mo(NO)(CN)₅] is obtained exclusively. The latter product is hereby reported for the first time. Its powder diffractogram being typical of a cubic system, a gross structural characterization has been made possible. The former under aqueous, aerobic conditions yields a new product, (NMe₄)₂[Mo(NO)(CN)₄].     

A general microcantilever surface modification method using a multilayer for biospecific recognition

The key to microcantilever surface modification technology is to selectively modify one side of a microcantilever surface with molecular recognition layers. In this paper, we report a general microcantilever modification method using a multilayer film.     

Extracellular pH influences the mode of cell death in human colon adenocarcinoma cells subjected to photodynamic treatment with chlorin p6

Effect of varying extracellular pH on mode of cell death induced by photodynamic action of chlorin p6 was investigated in human colon carcinoma (Colo-205) cells. At an extracellular pH of 7.4, compared to cells treated with chlorin p6 in dark, the photodynamically treated cells showed reduction in mitochondrial membrane potential, an increase in ADP/ATP ratio (1:2) and a large percentage of cells with chromatin condensation. In contrast, when photodynamic treatment and post irradiation incubation was carried out in acidic medium (pH 6.5), total loss of mitochondrial membrane potential, a marked increase in ADP/ATP ratio (1:33) and increased damage to plasma membrane were observed. Further, cells subjected to photodynamic treatment in a medium of pH 7.4 showed twofold increase in caspase-3 activity as compared to photodynamic treatment at pH 6.5. These results suggest that chlorin p6 mediated photodynamic action induces apoptotic cell death when extracellular pH is 7.4 whereas necrosis is more predominant under condition when extracellular pH is 6.5.     

Extraction of uranium(VI) and plutonium(IV) with dihexylbutyramide and dihexylisobutyramide from nitric acid medium

The extraction of uranium(VI) and plutonium(IV) was carried out with two isomeric monoamides, dihexylbutyramide (DHBA) and dihexylisobutyramide (DHIBA) from nitric acid medium, usingn-dodecane as diluent. The possibility of separation of the two metal ions from each other without valency adjustment was attempted. U(VI) was extracted as its disolvate, while Pu(IV) was extracted as its trisolvate. From the variation of distribution ratio with temperature, it was shown that the extraction reaction was enthalpy controlled in all the cases.