Structure in metastable peaks arising from reactions in which[C3H3]+ ions are produced

The metastable peak resulting from the fragmentation of [C₇H₇]²⁺? ions fram a variety of sources shows structure due to the presence of two reactions releasing different amounts of translational energy. The translational energy differences has been measured as 0.52 ± 0.04eV and is thought to be due to the formation of product ions of different structure via competing reactions from a single transition state. The possible structures of these ions are discussed, and it is proposed that the effect observed is due to the formation of [C₃H₃]⁺ ions in two forms, cyclopropenyl and proparg1. The metastable singly charged ions which also lead to product ions of formula [C₃H, ₃]⁺.     

Electro-optic scattering from nitrocellulose solutions

Measurements have been made of the light intensity scattered from dilute solutions of a sample of nitrocellulose ($\text{M}{}_{\mathrm{w}}\text{= 460,000}$) in acetone, both in the absence and presence of a.c. and d.c. electric fields. In an earlier study, owing to a mathematical slip and a false interpretation of an experimental parameter, other workers [5] interpreted similar measurements in terms of a freely rotating polar chain model. It is shown herein that this cannot be so and that the molecules of nitrocellulose of this order of molecular weight and in this type of solvent are better regarded as extremely stiff and extended.     

Development of fast atom bombardment mass spectral methods for the identification of carcinogen-nucleoside adducts

An analytical strategy using fast atom bombardment (FAB) ionization and tandem mass spectrometry has been developed to determine the molecular weight and major fragment ions, and to provide limited structural characterization of low picomole levels of carcinogen-nucleoside adducts. This strategy consists of three main components: (1) the sensitivity for analysis by FAB combined with mass spectrometry is increased via chemical derivatization; (2) the nucleoside adducts are selectively detected by using constant neutral loss scans; and (3) structurally characteristic fragments are obtained by using daughter ion scans. Trimethylsilyl derivatized arylamine-nucleoside adducts have been detected at levels as low as a few picomoles by using this approach. After experimental determination of the mass of the BH ₂ ⁺ fragment ion, daughter ion spectra have been used to probe the structure specificity associated with collision-activated decomposition of this fragment. With model C-8 substituted arylamine adducts [N-(deoxyguanosin-8-yl)-4-aminobiphenyl, N-(deoxyadenosin--yl)-4-aminobiphenyl, and N-(deoxyguanosin-8-yl)-2-aminofluorene], nucleoside-specific and carcinogen-specific fragmentation have been observed in daughter ion spectra.     

Varieties of quasigroups arising from 2-perfect m-cycle systems

For m = 6 and for all odd composite integers m, as well as for all even integers m 10 that satisfy certain conditions, 2-perfect m-cycle systems are constructed whose quasigroups have a homomorphism onto quasigroups which do not correspond to a 2-perfect m-cycle systems. Thus it is shown that for these values of m the class of quasigroups arising from all 2-perfect m-cycle systems does not form a variety.     

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Synthesis of High χ–Low N Diblock Copolymers by Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) enables the scalable synthesis of functional block copolymer nanoparticles with various morphologies. Herein we exploit this versatile technique to produce so-called “high χ–low N” diblock copolymers that undergo nanoscale phase separation in the solid state to produce sub-10 nm surface features. By varying the degree of polymerization of the stabilizer and core-forming blocks, PISA provides rapid access to a wide range of diblock copolymers, and enables fundamental thermodynamic parameters to be determined. In addition, the pre-organization of copolymer chains within sterically-stabilized nanoparticles that occurs during PISA leads to enhanced phase separation relative to that achieved using solution-cast molecularly-dissolved copolymer chains.     

Computations of relativistic LEED intensities and spin-polarisations for tungsten (001)

The effects of relativistic corrections in low-energy electron diffraction intensity calculations are assessed by reference to relativistic and non-relativistic computations for tungsten (001). Small changes are observed in the calculated intensities and band structures and a significant degree of spin-polarisation is predicted for the diffracted beams. The spin-polarisation profiles are more complicated than those observed in gas-phase experiments because of the influence of multiple scattering. The results suggest that LEED could provide a strong source of polarised electrons for use in scattering experiments. It is suggested that in future LEED experiments both spin-polarisation and intensity measurements should be performed on the diffracted electron beams.