Photochemically doped polypyrrole
Chemically prepared polypyrrole was treated with diphenyliodonium hexafluoroarsenate and upon u.v. irradiation a conductivity of 3 × 10–3Ω–1 cm–1 was attained.
Materials Literature
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Helium trapping at dislocations, precipitates and grain boundaries
Helium bubble formation was observed in austenitic stainless steels by transmission electron microscopy following implantation of 30 to 1000 appm helium at room temperature and annealing at 700 to 800°C. Helium bubble distributions at dislocations and at various grain boundaries and precipitates were studied. It was f…
Transport phenomena at metal surfaces
Previous theoretical treatments of the scattering of conduction electrons at surfaces are reviewed and it is found that a more complete theory is necessary if the effects of surface scattering in transport phenomena are to be adequately understood. The boundary condition for the distribution function is derived and an…
Two new mesophases in a chiral compound
Microscopical, miscibility and X-ray studies establish the existence of two new mesophases in the two enantiomers of 1 (methyl)-heptyl terephthalidene bis amino cinnamate. In one of this two mesophases the two enantiomers do not exhibit a total miscibility range; while for the second the untwisted form observed with t…
Collapse of branched polymers
Exact calculations using transfer matrices on finite strips are performed to study the two-dimensional problem of one lattice animal with an attractive nearest neighbour interaction. Thermodynamic quantities such as specific heat, compressibility, thermal expansion are calculated. Finite size scaling with two strips o…
Propriétés statiques d'une chaîne isotrope alternée de spins quantiques 1/2 et de spins classiques
Les propriétés magnétiques statiques d'une chaîne isotrope formée en un ordre alterné de spins quantiques 1/2 et de spins classiques sont déterminées analytiquement en toute rigueur. La susceptibilité théorique est un bon accord avec les mesures de Verdaguer sur le composé CuMn(S2C2O 2)2(H2O)7,5.
Hydrides and delayed hydrogen cracking in zirconium and its alloys
A critical review is presented of published data on hydrogen, hydrides, and delayed hydrogen cracking (or hydrogen-induced delayed cracking, HIDC) in zirconium and its alloys. It is shown that factors such as solution temperature, cooling rate, and applied or residual stresses greatly affect the hydride morphology and…
THE SPREADING OF A THIN DROP BY GRAVITY AND CAPILLARITY
Solutions are given for the spreading of a thin drop using lubrication theory. The relative importance of gravity to capillarity in the spreading is measured by the Bond number and all values of this number are covered. As usual when a moving contact line is present, a slip boundary condition is applied. For moderate…
Reduced forms of LaNiO 3 perovskite. Part 1.—Evidence for new phases: La 2 Ni 2 O 5 and LaNiO 2
Low-temperature reduction of LaNiO3 under hydrogen leads to new compounds such as La2Ni2O5 and LaNiO2 before total reduction. Hydrogen consumption, X-ray diffraction and XANES demonstrate the presence of these new phases. Ni3+ in LaNiO3 becomes Ni2+ in La2Ni2O5, and a pure monovalent nickel phase is obtained in LaNiO2…
The Impact of Compressible Liquids
Consideration is given to liquid impact in the supersonic regime in order to characterize pressure loading and other mechanisms which could damage a solid target such as a jet in flight. The liquid ...
Dry Etch Resistance of Organic Materials
The dry etch resistance of metal‐free organic materials, mainly resist materials, has been studied. Etch rates have been measured under argon ion‐beam, oxygen ion‐beam, and oxygen plasma etching conditions. It is found that the etch rate under ion bombardment has a linear dependence on the of the etched materials, whe…
Chloramphenicol Acetyltransferase: Enzymology and Molecular Biology
Naturally occurring chloramphenicol resistance in bacteria is normally due to the presence of the antibiotic inactivating enzyme chloramphenicol acetyltransferase (CAT) which catalyzes the acetyl-S-CoA-dependent acetylation of chloramphenicol at the 3-hydroxyl group. The product 3-acetoxy chloramphenicol does not bind…
Wave Propagation in the Split Hopkinson Pressure Bar
Elastic wave propagation in the split Hopkinson pressure bar (SHPB) is discussed with an emphasis on the origin and nature of the oscillations that often trail the leading edge of the pressure wave. We show that in the conditions of the SHPB test the pressure bars vibrate in the fundamental mode and that elastic wave…
Evaluation of Collagen Crosslinking Techniques
The properties of collagen films crosslinked by physical and chemical techniques were compared to the properties of films crosslinked with glutaraldehyde (GTA). Physical techniques studied include exposure to short wave (254 nm) u.v. irradiation and severe dehydration. Chemical techniques studied include immersion of…
The optical properties of thallium-like impurities in alkali-halide crystals
Per me si va nella citt`a dolente Per me si va nell'eterno dolore Per me si va tra la perduta gente Dante, Inferno, III, 1–3 Experimental and theoretical investigations of optical absorption and emission spectra of alkali-halides doped with Tl+-like impurities are reviewed. The Jahn—Teller effect plays an important ro…
Energetics and formation kinetics of helium bubbles in metals
Recent theoretical work on the energetics and formation kinetics of helium bubbles in metals is reviewed. The energetics are discussed in particular for bubbles with radii between 10 and 1000 Å containing helium under very high pressures (nonideal gas bubbles). For this size range, the bubble formation free energy is…
Colloidal crystals
The so-called colloidal crystals are monodisperse colloids in which colloidal particles organize themselves in long-range-ordered crystals. First, the monodispersity of colloidal particles and their interactions, essential for crystallization phenomenon, are discussed and illustrated using examples of natural and synt…
Structural destabilization induced by lithium intercalation in MoS2 and related compounds
2H-MoS 2 is a semiconductor with a hexagonal layered structure. Each Mo atom is prismatically coordinated by six S atoms. Our in situ X-ray diffraction results indicate that, upon intercalation, the MoS 2 host lattice undergoes a first order phase transition in which the Mo coordination changes from trigonal prismatic…
Studies on the Relationship Between Water‐satured State and Crystallinity by the Diffraction Method for Moistened Potato Starch
Abstract Crystallinity was measured by X‐ray diffraction method and water‐saturated state was determined by means of the moisture contents calculated from the crystallinity for moistened cellulose and potato starch. In the X‐ray diffractograms the upper areas which were separated by the straight line joined the points…
Microfibrillated cellulose, a new cellulose product: properties, uses, and commercial potential
A new form of cellulose, which is expanded to a smooth gel when dispersed in polar liquids, is produced by a unique, rapid, physical treatment of wood cellulose pulps. A 2% suspension of microfibrillated cellulose (MFC) in water has thixotropic viscosity properties and is a stable gel on storage, or when subjected to…