Enhanced superconductivity and lattice instability in Nb-Rh alloys

Superconductivity with transition temperature above 10 °K has been observed in a new Nb-Rh intermediate phase. The new metastable phase is obtained by liquid quenching the binary alloy or by the addition of a small percentage of carbon to form a stable ternary alloy

Bulk and wetting phenomena in a colloidal mixture of hard spheres and platelets

Density functional theory is used to study binary colloidal fluids consisting of hard spheres and thin platelets in their bulk and near a planar hard wall. This system exhibits liquid-liquid coexistence of a phase that is rich in spheres (poor in platelets) and a phase that is poor in spheres (rich in platelets). For the mixture near a planar hard wall, we find that the phase rich in spheres wets the wall completely upon approaching the liquid demixing binodal from the sphere-poor phase, provided the concentration of the platelets is smaller than a threshold value which marks a first-order wetting transition at coexistence. No layering transitions are found in contrast to recent studies on binary mixtures of spheres and non-adsorbing polymers or thin hard rods.Comment: 6 pages, 4 figure

Role of Metastable States in Phase Ordering Dynamics

We show that the rate of separation of two phases of different densities (e.g. gas and solid) can be radically altered by the presence of a metastable intermediate phase (e.g. liquid). Within a Cahn-Hilliard theory we study the growth in one dimension of a solid droplet from a supersaturated gas. A moving interface between solid and gas phases (say) can, for sufficient (transient) supersaturation, unbind into two interfaces separated by a slab of metastable liquid phase. We investigate the criteria for unbinding, and show that it may strongly impede the growth of the solid phase.Comment: 4 pages, Latex, Revtex, epsf. Updated two reference

Colloidal gelation and non-ergodicity transitions

Within the framework of the mode coupling theory (MCT) of structural relaxation, mechanisms and properties of non-ergodicity transitions in rather dilute suspensions of colloidal particles characterized by strong short-ranged attractions are studied. Results building on the virial expansion for particles with hard cores and interacting via an attractive square well potential are presented, and their relevance to colloidal gelation is discussed.Comment: 10 pages, 4 figures; Talk at the Conference: "Unifying Concepts in Glass Physics" ICTP Trieste, September 1999; to be published in J. Phys.: Condens. Matte

Diffusive Evolution of Stable and Metastable Phases II: Theory of Non-Equilibrium Behaviour in Colloid-Polymer Mixtures

By analytically solving some simple models of phase-ordering kinetics, we suggest a mechanism for the onset of non-equilibrium behaviour in colloid-polymer mixtures. These mixtures can function as models of atomic systems; their physics therefore impinges on many areas of thermodynamics and phase-ordering. An exact solution is found for the motion of a single, planar interface separating a growing phase of uniform high density from a supersaturated low density phase, whose diffusive depletion drives the interfacial motion. In addition, an approximate solution is found for the one-dimensional evolution of two interfaces, separated by a slab of a metastable phase at intermediate density. The theory predicts a critical supersaturation of the low-density phase, above which the two interfaces become unbound and the metastable phase grows ad infinitum. The growth of the stable phase is suppressed in this regime.Comment: 27 pages, Latex, eps

Comparison of antiemetic efficacy of granisetron and ondansetron in Oriental patients: a randomized crossover study.

A double-blind randomized crossover trial was performed to compare the antiemetic efficacy of two 5-HT3 receptor antagonists, granisetron and ondansetron, in Chinese patients receiving adjuvant chemotherapy (cyclophosphamide, methotrexate and 5-fluorouracil) for breast cancer. Twenty patients were randomized to receive chemotherapy with either granisetron on day 1 and ondansetron on day 8 of the first cycle followed by the reverse order in the second cycle, or vice versa. The number of vomiting episodes and the severity of nausea in the first 24 h (acute vomiting/nausea) and the following 7 days (delayed vomiting/nausea) were studied. Acute vomiting was completely prevented in 29 (72.5%) cycles with granisetron and 27 (67.5%) cycles with ondansetron, and treatment failure (>5 vomiting episodes) occurred in two (5%) cycles with each agent (P = NS). Acute nausea was completely controlled in 15 (37.5%) cycles with granisetron and 14 (35%) cycles with ondansetron, whereas severe acute nausea occurred in four (10%) cycles with each agent (P = NS). However, complete response for delayed vomiting was observed in only 21 (52.5%) cycles with granisetron and 22 (55%) cycles with ondansetron (P = NS), and delayed nausea was completely controlled in only 11 (27.5%) and ten (25%) cycles respectively (P = NS). In conclusion, both granisetron and ondansetron are effective in controlling acute nausea and vomiting in Chinese patients, with equivalent antiemetic efficacy. Control of delayed nausea and vomiting is less satisfactory

Glasses in hard spheres with short-range attraction

We report a detailed experimental study of the structure and dynamics of glassy states in hard spheres with short-range attraction. The system is a suspension of nearly-hard-sphere colloidal particles and non-adsorbing linear polymer which induces a depletion attraction between the particles. Observation of crystallization reveals a re-entrant glass transition. Static light scattering shows a continuous change in the static structure factors upon increasing attraction. Dynamic light scattering results, which cover 11 orders of magnitude in time, are consistent with the existence of two distinct kinds of glasses, those dominated by inter-particle repulsion and caging, and those dominated by attraction. Samples close to the `A3 point' predicted by mode coupling theory for such systems show very slow, logarithmic dynamics.Comment: 22 pages, 18 figure