MoSi{sub 2} matrix composites have been recognized lately as potential materials for structural applications at elevated temperatures. Specifically, MoSi{sub 2} composites may exhibit useful properties at temperatures to 1400{degrees}C. Previous work improved the yield strength of MoSi{sub 2} at 1400{degrees}C by a factor of five through SiC whisker reinforcement. Current research is directed towards increasing the fracture toughness of MoSi{sub 2} through the addition of ductile phase reinforcements such as niobium and tantalum. The reaction between Nb and MoSi{sub 2} to form (Mo,Nb){sub 5}Si{sub 3} proceeds with faster kinetics at hot isostatic press temperatures as low as 1100{degrees}C when compared to the reaction between Ta and MoSi{sub 2} to form (Mo,Ta){sub 5}Si{sub 3}. This reaction product exhibits very poor properties, as evidenced by crack propagation through this layer during fracture. The feasibility of hot working these composites to produce tailored microstructures is examined. 11 refs., 10 figs.

The gauge hierarchy problem is reviewed and a class of effective field theories obtained from superstrings is described. These are characterized by a classical symmetry, related to the space-time duality of string theory, that is responsible for the suppression of observable supersymmetry breaking effects. At the quantum level, the symmetry is broken by anomalies that provide the seed of observable supersymmetry breaking, and an acceptably large gauge hierarchy may be generated. 39 refs.

The Compact Torus (Spheromak-type) is a near ideal plasma confinement configuration for acceleration. The fields are mostly generated by internal plasma currents, plasma confinement is toroidal, and the compact torus exhibits resiliency and stability in virtue of the ``rugged`` helicity invariant. Based on these considerations we are developing a coaxial rail-gun type Compact Torus Accelerator (CTA). In the CTA, the CT ring is formed between coaxial electrodes using a magnetized Marshall gun, it is quasistatically ``precompressed`` in a conical electrode section for inductive energy storage, it is accelerated in a straight-coaxial electrode section as in a conventional rail-gun, and it is focused to small size and high energy and power density in a final ``focus`` cone section. The dynamics of slow precompression and acceleration have been demonstrated experimentally in the RACE device with results in good agreement with 2-D MHD code calculations. CT plasma rings with 100 {micro}gms mass have been accelerated to 40 Kj kinetic energy at 20% efficiency with final velocity = 1 X 10{sup 8} cm/s (= 5 KeV/H{sup +}). Preliminary focus tests exhibi dynamics of radius compression, deceleration, and bouncing. Compression ratios of 2-3 have been achieved. A scaled-up 10-100 MJ CTA is predicted to achieve …

Palladium deposited on kieselguhr (Pd/K) will be used for several applications in the Replacement Tritium Facility (RTF). The Pd/K procured for the RTF consists of three batches. All three batches meet the specified particle size distribution that 80 weight percent be between 30 and 50 mesh. One batch contains 53.6% palladium which is less than the specified minimum of 55%. Another batch has a chlorine content of 311 ppm which is slightly in excess of the specified maximum of 250 ppm. These nonconformances are not considered significant since batches will be blended to yield Pd/K for the RTF that meets the chlorine specification and has acceptable palladium content. Some of the Pd/K procured for the RTF will be heat treated to strengthen the particles against breakdown during use. Heat treating parameters must be determined that will preserve the desired absorption/desorption behavior of the Pd/K. 8 refs., 7 figs., 2 tabs.

Palladium deposited on kieselguhr (Pd/K) will be used for several applications in the Replacement Tritium Facility (RTF). The Pd/K procured for the RTF consists of three batches. All three batches meet the specified particle size distribution that 80 weight percent be between 30 and 50 mesh. One batch contains 53.6% palladium which is less than the specified minimum of 55%. Another batch has a chlorine content of 311 ppm which is slightly in excess of the specified maximum of 250 ppm. These nonconformances are not considered significant since batches will be blended to yield Pd/K for the RTF that meets the chlorine specification and has acceptable palladium content. Some of the Pd/K procured for the RTF will be heat treated to strengthen the particles against breakdown during use. Heat treating parameters must be determined that will preserve the desired absorption/desorption behavior of the Pd/K. 8 refs., 7 figs., 2 tabs.

The x-ray holography program at the Lawrence Livermore National Laboratory has two principal goals: (1) the development of x-ray diffraction techniques for DNA sequence analysis and (2) the development of x-ray laser holography for structural analysis of intact biological cells and organelles. DNA sequence analysis will be accomplished by applying x-ray diffraction techniques to determine the ensemble average of the sequence of labels along the individual elements of crystalline DNA. X-ray laser holographic imaging will be accomplished by applying three dimensional x-ray holography to elucidate the structure of few hundred angstrom objects such as 300 {Angstrom} chromatin fibers, nuclear pores and nucleic acid replication complexes in living cells. Existing laboratory x-ray lasers will be utilized to produce flash x-ray holograms of the biological structures.