The Relation of Constraints on Particle Statistics for Different Species of Particles

Quons are particles characterized by the parameter q, which permits smooth interpolation between Bose and Fermi statistics; q = 1 gives bosons, q = -1 gives fermions. In this paper we give a heuristic argument for an extension of conservation of statistics to quons with trilinear couplings of the form ffb, where f is fermion-like and b is boson-like. We show that q _f ² = q_b. In particular, we relate the bound on q for photons to the bound on q_e for electrons, allowing the very precise bound for electrons to be carried over to photons. An extension of this argument suggests that all particles are fermions or bosons to a high precision.     

Theory of the time and frequency dependence of near-resonant raman scattering and quantum beats

A calculation of the time dependence of light scattering from an atom or molecules yields a continuous transition from fast Raman scattering to resonance fluorescence in agreement with recent experiments. If the resonant excited state has two or more nearby levels, “quantum beats” may be observed. These quantum beats are present even if the incident light is tuned off resonance.     

Hollow-cathode sputtering source for the production of gas-phase metal atoms of the refractory elements

A simple, versatile hollow-cathode sputtering system for the production of gas-phase metal atoms has been developed. The source has been used to produce gas-phase metal-containing diatomic and polyatomic molecules. Chemiluminscence and laser-induced fluorescence studied have been used to characterize the source and show that it produces high densities (10¹⁴/cm³) of atoms at a low temperature (340 K).     

Fluorescent labeling of a narrow polydispersity high molecular weight polystyrene

Narrow polydispersity polystyrene with a molecular weight of 1.03×10⁶ has been functionalized with anthracene groups using the metallocene technique. Side reactions such as chain coupling and bond scission can be limited by working in THF at –75°C. Gel permeation chromatography combined with on‐line viscometric, refractive index and fluorescence detection allows us to verify that degradation did not exceed 1 bond scission/180 000 monomer units. The degree of grafting increases with the reaction time but remains modest (< 5% after 7 h) at low temperature.     

Converting the SLOWPOKE reactor to low-enrichment uranium fuel

SLOWPOKE-2 is a 20 kW pool-type research reactor, producing a thermal neutron flux of 10¹² n·cm^–2·s^–1 at five sample sites in the beryllium reflector. Because of its inherent safety, it is the only reactor in the world licensed for unattended operation. The present core contains approximately 900 g highly-enriched uranium (93 wt.% U-235 in U), which could be viewed as a potential source of nuclear weapons material. To overcome proliferation concerns, Atomic Energy of Canada Limited (AECL) has developed a low enrichment fuel containing less than 20 wt.% U-235 in U. The first low enrichment uranium core will be installed in a new SLOWPOKE-2 reactor at the Royal Military College, Kingston, Ontario.     

Phosphoryl choline introduces dual activity in biomimetic ionomers

Dual activity of phosphoryl choline (PC) functional poly(trimethylene carbonate) (PTMC) was found which induces the zwitterionic biomimetic PC group to form physical cross-links with ionomers in the bulk, and at the same time enrich at the surface of cast films. The formation of zwitterionic domains from a bifunctional PC-PTMC-PC (ionomer) provided firm films with a low elastic modulus in contrast to the tacky PTMC starting material (Mn approximately 3900 g/mol) with poor mechanical performance. In addition, the ionomer possessed improved hemocompatible properties that was explained by the enrichment of PC at the surface, suggesting a way to tailor the mechanical performance of biodegradable PTMC-based ionomers while providing its bioactivity. Tailored elasticity while maintaining hemocompatibility of a biodegradable ionomer should be of particular interest for a variety of in vivo applications.     

Gold nanoparticle synthesis in graft copolymer micelles

 An amphiphilic poly(acrylic acid)/polystyrene graft copolymer (PAA-g-PS) has been used to form “nanoreactors” for the synthesis of gold clusters. Such copolymers tend to form stable micelles in non-polar organic solvents where the poly(acrylic acid) chains constitute the core, and the polystyrene chains, the shell. In the present study, the micellar structure of PAA-g-PS in toluene has been demonstrated by dynamic light scattering and transmission electron microscopy (TEM). The subsequent preparation of gold-graft copolymer composites involved the introduction of gold chloride (AuCl₃), either in powder form or previously dissolved in ether, into the micellar cores of the PAA-g-PS in toluene. The gold salt was then reduced by ultraviolet (UV) irradiation of the emulsion, or of dried cast films. TEM and ultraviolet-visible (UV/Vis) spectroscopy were used to characterize the resulting composites. Gold particles of less than 5 nm in diameter were observed in all cases, but the size distribution and the spatial arrangement of the clusters in the cast films were modified when diethyl ether was used to introduce AuCl₃ into the PAA-g-PS micellar cores. This was thought to be due to enhanced nucleation of the gold particles and partial disruption of the micellar cores in the presence of diethyl ether. Received: 21 January 1998 Accepted: 11 June 1998     

Pore size modification of macroporous crosslinked poly(dicyclopentadiene)

This article describes the pore size modification and in situ surface functionalization of macroporous crosslinked poly(dicyclopentadiene), produced by chemically induced phase separation, with norbornene‐functionalized poly(ethylene glycol) telechelic oligomers. The microstructure of the open porosity materials produced with this technique consisted of agglomerated particles. The incorporation of these telechelic oligomers allowed a substantial decrease in the pore size and a related increase in the internal surface area. These functionalized oligomers acted as stabilizers around the primary particles produced by phase separation and blocked their growth so that the materials resulting from the agglomeration of these smaller particles showed finer microstructures. The resulting porous materials were characterized by scanning electron microscopy, density measurements, nitrogen adsorption, and mercury porosimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2036–2046, 2003