Detection of autocatalytic decomposition behavior of energetic materials using APTAC

Characterization of autocatalytic decomposition reactions is important for the safe handling and storage of energetic materials. Isothermal differential scanning calorimetry (DSC) has been widely used to detect autocatalytic decomposition of energetic materials. However, isothermal DSC tests are time consuming and the choice of experimental temperature is crucial. This paper shows that an automatic pressure tracking calorimeter (APTAC) can be a reliable and efficient screening tool for the identification of autocatalytic decomposition behavior of energetic materials. Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine family. High concentrations of HAN are used as liquid propellants, and low concentrations of HAN are used primarily in the nuclear industry for decontamination of equipment. Because of its instability and autocatalytic decomposition behavior, HAN has been involved in several incidents.     

Extremally disconnected spaces, subspaces and retracts

A characterization of compact subspaces of extremally disconnected spaces is given which is similar to Gleason's characterization that the extremally disconnected spaces are projective for the class of compact spaces. An equivalence is established between the questions of whether every basically disconnected space is embeddable into an extremally disconnected space and the Borel lifting problems for the category algebras of generalized Cantor cubes. We study an inductive method of strengthening the product topology on the Cantor cubes to extremally disconnected topologies and use this to establish, from CH, that every compact F-space of weight c⁺ embeds into an extremally disconnected space.     

The behaviour of some functionally substituted α-allenic alcohol derivatives toward organocopper(I) species

Trimethylsilyl ethers of 2,3-hexadien-5-yn-1-ols (1) undergo carbocupration at the terminal triple bond, and this reaction has been used to prepare, among other species, the trimethylsilyl ethers of 8-trimethylsilyl-2,3,5-octatrien-7-yn-1-ols(6a and 7a). When the terminal triple bond of 1 is protected with a trimethylsilyl group S_N2′-like displacements take place upon addition of RCu, with predominant formation of E-dienynes in which H is present instead of R, especially when s-BuCu is used. Only when R is methyl is the R group transferred. On the other hand, smooth formation of dienynes bearing the R group are observed upon reaction of methanesulfinates with RCu; in this case, however, the configuration of the dienynes is mainly Z. A mechanistic rationalization of the results is proposed.     

Adsorption of Immunoglobulin G on Core-Shell Latex Particles Precoated with Chaps

The aim of this work is to investigate the adsorption behavior of a monoclonal antibody (immunoglobulin G, IgG) on latex particles, possessing reactive chloromethyl groups, precoated with 3-([3-cholamidopropyl]dimethylammonio-1-propanesulfonate (Chaps). The amount and reactivity of the surface chloromethyl groups were monitored by the nucleophilic attack of glycinate to the functional groups as a function of time at 22 and 36 degrees C. The extent of displacement of Chaps by IgG and the enthalpy of the process were determined under two different conditions of precoating the latex particles with Chaps, at 22 and 36 degrees C. The adsorption of IgG takes place in two steps; the first one involves physical interaction between IgG and the surface. This step is relatively fast (in the range of minutes) and independent of temperature. In the second step covalent bonding between the protein and the active surface groups occurs. This reaction is improved by raising the temperature because Chaps desorption, which exposes the reactive chloromethyl groups on the latex particles, is kinetically and thermodynamically favored at 36 degrees C and the covalent bonding of IgG is faster at 36 degrees C. Copyright 2000 Academic Press.     

Ultrafast magneto-optics in nickel: magnetism or optics?

Several magnetic and optical processes contribute to the magneto-optical response of nickel thin films after excitation by a femtosecond laser pulse. We achieved a first complete identification by explicitly measuring the time-resolved Kerr ellipticity and rotation, as well as its temperature and magnetic field dependence in epitaxially grown (111) and (001) oriented Cu/Ni/Cu wedges. The first hundreds of femtoseconds the response is dominated by state filling effects. The true demagnetization takes approximately 0.5-1 ps. At the longer (sub-ns) time scales the spins are found to precess in their anisotropy field. Simple and transparent models are introduced to substantiate our interpretation.