AFM observations of latent fission tracks on surfaces: amorphous SiO2 and quartz

Preliminary results of a systematic AFM experimental investigation of the surface ‘track’ effects produced by the passage of fission fragments from a californium (²⁵²Cf) source into amorphous SiO₂ and quartz are described. Fission fragments from the source were collimated using a 10 μm thick aluminum foil and comprised fragments with the usual binary distribution of energies—light and heavy—79.4 and 103.8 MeV. Irradiations and AFM measurements were carried out in air at normal room temperature and pressure. Remarkably high sputtering yields/fragment were discovered, and in the case of crystalline quartz the ejecta was found to be arranged in an ordered manner. A brief discussion is given of a part likely to be played by electronic energy loss induced Coulomb explosion of target atoms for each point of fragment entry.     

On the elimination of the t-explicit divergence in the calculation of transport coefficients

Through an analysis of the expression of the autocorrelation function of the velocities in the matrix representation, an identification is made of all the matrix elements which lead to the so-called t or ? explicit divergence. The terms in the expansion can be easily summed and as a result the divergence is eliminated. A comparison with the procedure recently developed by Bartis and Oppenheim is made.     

Design of Steel-Composite Multirim Cylindrical Flywheels Manufactured by Winding with High Tensioning and in situ Curing. 2. Numerical Analysis

The possibility of using forced winding coupled with in situ curing to increase the energy storage capacity of hybrid steel-composite cylindrical flywheels is estimated and analyzed. Stress states for given loading conditions in two- and three-layered compound cylinders made from steel and four different types of unidirectional composites are calculated. For each of these combinations, optimum dimensions and the energy storage capacity of the flywheels are found.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 3, pp. 351–372, May–June, 2005.     

Domain wall dynamics studied by impedanciometry

The knowledge of the basic phenomena governing the magnetoimpedance (skin-depth effect) allows the use of the impedance spectrum to study the dynamic magnetization processes in magnetic materials. By modeling the frequency dependence of the impedance spectrum, the corresponding permeability spectrum can be obtained, from which it is possible to obtain several important parameters concerning the dynamics of the domain walls, namely: domain wall critical speed, wall mobility, domain wall energy and thickness. In this work the technique is outlined and applied to (1 1 0)[0 0 1]FeSi_3%, a very well-known sharp textured magnetic material. The results compare favorably to those known from the literature.     

Batocanone,a new naphthoquinonylnapththoquinone epoxide

Batocanone is the second naphthoquinonyl-naphthoquinone epoxide to be isolated from higher plants, its structure corresponding to isodiospyrin 2′,3′-epoxide.     

Polypropylene reactor mixture obtained with homogeneous and supported catalysts

Propylene polymerizations were performed with homogeneous ?₂C(Flu)(Cp)ZrCl₂ and SiMe₂(Ind)₂ZrCl₂ catalyst mixtures and with mixtures supported on the zeolite acid mordenite. The polymerizations were performed in toluene and hexane/triisobutylaluminum at different temperatures and Al(MAO)/Zr concentration ratios. The effects of these variables on the catalyst activity were investigated with statistical experimental planning. The average molecular weights, molecular weight distributions, melting temperatures, and crystallinities of the obtained polymers were examined. The results showed lower activities for the homogeneous catalyst mixture than for the isolated systems. On the other hand, high activities were obtained for the syndiospecific heterogeneous system, but very low values were obtained for the supported isospecific metallocene, although both catalysts were prepared under the same conditions. The supported binary system showed intermediary catalyst activity in comparison with the syndiospecific and isospecific supported catalysts. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 263–272, 2005     

Synthesis and mesomorphic properties of a new chiral series with a heterocycle in the molecular core

We report a number of different homologous series with a heterocycle incorporated in the molecular core near the chiral chain. Two of these series differ in the type of chiral chain, -CH*(CH 3 )C 6 H 13 or -CH*(CH 3 )-CO 2 -C 4 H 9 . Their properties are compared and found to show completely different polymorphism. The first series exhibits only SmC* and SmA phases whereas the second possesses TGB, N* and BP phases. The mesomorphic properties were studied by optical microscopy, DSC and electro-optical measurements. The effect of substitution of the phenyl ring near the chiral chain by a heterocycle is discussed.     

Picosecond duration laser pulse generation by simultaneous active-passive mode-locking in Ar+ ion and dye lasers

We use a rate equation model to analyse a technique for the generation of picosecond duration laser pulses in argon pumped dye lasers. The system is based on passive mode-locking of the Ar⁺ laser by saturable absorption of the dye which is inserted in the Ar⁺ laser cavity. Simultaneously, the dye is forced to oscillate in a regime of synchronously pumped mode-locking. The system is relatively simple, does not require the use of an acousto-optical light modulator and can be easily implemented in commercially available lasers. Pulses shorter than 100 ps and having an average power of 20 mW were obtained at a repetition rate of 110 MHz. Good agreement between the model and experimental results was also obtained.