Dual-frequency optical pumping for spin-polarizing a lithium atomic beam

A lithium-6 atomic beam is spin-polarized by means of optical pumping with a single-mode dye laser operating on the resonance transition. Simultaneous pumping of both hyperfine substates is achieved by frequency-splitting the laser light with an acousto-optic modulator. A polarization dependent signal, obtained by probing the optical activity of the beam with linearly polarized light, is utilized in a microprocessor-controlled laser stabilization scheme. The polarization is analyzed with a sextupole magnet and its overall value is 0.70 for an intensity of 1×10¹⁴ atms s⁻¹. By reversing the sense of circular polarization of the pumping light the atomic beam polarization is easily reversed in direction.     

Thermally stable polymers based on acetylene-terminated adamantanes

1,3-Diethynyl-5,7-dimethyladamantane, 1,3-diethynyl-5-phenyladamantane, 1,3,5-triethynyladamantane, and 3,3′-diethynyl-1,1′-biadamantane, were synthesized and polymerized thermally at 210°C. The thermoset resins obtained were post-cured at 300°C for 16 h to give materials that exhibited onsets of degradation (TGA) in air at 460–477°C and in helium at 460–485°C. The fully cured materials did not exhibit any detectable DSC transitions between 25 and 400°C. An attempt to thermally polymerize 1-ethynyl-3-phenyladamantane was unsuccessful. © 1992 John Wiley & Sons, Inc.     

Effective and safe laser action in the surface fusion of a ternary medium while preserving the functionality of the easily fusible component

The manufacturing of biochips by heating a multicomponent layer of polymeric microparticles that contain sensitive elements is simulated. Heating is performed up to the stage of polymer shell melting without damage to the sensitive elements. The corresponding thresholds of laser parameters (radiation power density) are detected. The preservation of biological complex functionality under these parameters is experimentally shown.     

Parallel Spinors and Holonomy Groups on Pseudo-Riemannian Spin Manifolds

We describe the possible holonomy groups of simply connected irreducible non-locally symmetric pseudo-Riemannian spin manifolds which admit parallel spinors.     

Synthesis of heterocycles via ligand-free palladium catalyzed reductive Heck cyclization

Synthesis of five and six membered heterocycles, indolines, 2,3-dihydrobenzofurans, chromans, isochromans, 1,2,3,4-tetrahydroquinolines, and 1,2,3,4-tetrahydroisoquinolines, in 70-99% yield by a ligand-free palladium catalyzed reductive Heck cyclization of phenyl bromides and chlorides, under mild conditions, is reported. Water was found to be essential for these reactions.     

Eigenvalue estimates for Dirac operators coupled to instantons

We prove a sharp lower bound for the first positive eigenvalue of Dirac operators coupled to instantons and discuss the limit case.     

Periodic Cyclic Homology of Iwahori–Hecke Algebras

We determine the periodic cyclic homology of the Iwahori–Hecke algebras H _q , for q * not a proper root of unity. (In this paper, by a proper root of unity we shall mean a root of unity other than 1.) Our method is based on a general result on periodic cyclic homology, which states that a weakly spectrum preserving morphism of finite type algebras induces an isomorphism in periodic cyclic homology. The concept of a weakly spectrum preserving morphism is defined in this paper, and most of our work is devoted to understanding this class of morphisms. Results of Kazhdan and Lusztig and Lusztig show that, for the indicated values of q, there exists a weakly spectrum preserving morphism _q : H _q J, to a fixed finite type algebra J. This proves that _q induces an isomorphism in periodic cyclic homology and, in particular, that all algebras H _q have the same periodic cyclic homology, for the indicated values of q. The periodic cyclic homology groups of the algebra H ₁ can then be determined directly, using results of Karoubi and Burghelea, because it is the group algebra of an extended affine Weyl group.