Cycloalkenyl Halide Substitution Reactions of Enantiopure Arene cis-Tetrahydrodiols with Boron, Nitrogen and Phosphorus Nucleophiles

Enantiopure arene cis-tetrahydrodiols of bromobenzene and iodobenzene have been obtained in good yields, from chemoselective hydrogenation (rhodium-graphite) of the corresponding cis-dihydrodiol metabolites. Palladium-catalysed substitution of the halogen, by hydrogen, boron, nitrogen and phosphorus nucleophiles, in the acetonide derivatives, has yielded highly functionalised products for application in synthesis with potential as scaffolds for chiral ligands.

Spectroscopic characterization of prepulsed x-ray laser plasmas

Through the use of time-integrated space-resolved keV spectroscopy, we investigate line plasmas showing gain in Ne-like nickel, copper, and zinc for irradiation using the prepulse technique. The experiments were conducted at 1.06 mu m with the prepulse to main pulse intensity contrast ranging from 10(-6) to 10(-2). The effect of the prepulses on the plasma conditions is inferred through spectroscopic line ratio diagnostics for the electron temperature, the Ne-like ground-state density, and the lateral size of the Ne-like region. It is observed that neither the value of the electronic temperature nor its spatially resolved profile along the linear focus axis varies significantly with the prepulse level, contrary to the lateral width and the density of the Ne-like region in the plasma, which are seen to increase. These results explain, at least in part, why prepulsed x-ray lasers show such high gain and brightness.

Characteristics of rapidly recombining plasmas suitable for high-gain X-ray laser action

Recombining plasmas produced by picosecond laser pulses are characterized by measuring ratio of intensities of resonance lines of H- and He-like ions in the plasmas. It is found that the rapidly recombining plasmas produced by picosecond laser pulses are suitable for high-gain operation.

Development of XUV lasers at the RAL central laser facility

Recent progress in the development of XUV lasers by research teams using high-power and ultrashort-pulse Nd:glass and KrF laser facilities at the Rutherford Appleton Laboratory is reviewed. Injector-amplifier operation and prepulse enhanced output of the Ge XXIII collisional laser driven by a kilojoule glass laser, enhanced gain in CVI recombination with picosecond CPA drive pulses from a glass laser, and optical field ionization and XUV harmonic generation with a KrF CPA laser are described.

Using low and high prepulses to enhance the J=0-1 transition at 19.6 nm in the Ne-like germanium XUV laser

We report a study of the effect of prepulses on XUV lasing of Ne-like germanium for an irradiation geometry where approximate to 20 mm long germanium slab targets were irradiated at approximate to 1.6 x 10(13) W cm(-2) using approximate to 0.7 ns (1.06 mu m) pulses from the VULCAN glass laser. Prepulses were generated at fractional power levels of approximate to 2 x 10(-4) (low) and approximate to 2 x 10(-2) (high) and arrived on target 5 and 3.2 ns respectively in advance of the main heating pulse, For both the low and high prepulses the output of the 3p-3s, J = 0-1, line at 19.6 nm was enhanced such that the peak radiant density (J/st) for this line became greater than that for the normally stronger J = 2-1 lines at 23.2 and 23.6 nm. The J = 0-1 line, whose FWHM duration was reduced from approximate to 450 ps to approximate to 100 ps, delivered approximate to 6 x more power (W) than the average for the combined J = 2-1 lines, whose FWHM duration was approximate to 500 ps for both levels of prepulse, The higher prepulse was more effective, yielding approximate to 2 x more radiant density and approximate to 7 x more power on both the J = 0-1 and J = 2-1 transitions compared to the low prepulse case, The most dramatic observation overall was the approximate to 40 x increase of power in the J = 0-1 line for the high prepulse (approximate to 2%) case compared with the zero prepulse case. These observations, coupled with measurements of beam divergence and beam deviation through refractive bending, as well as general agreement with modelling, lead us to conclude that, for germanium, the main influence of the prepulse is (a) to increase the energy absorbed from the main pulse, (b) to increase the volume of the gain zone and (c) to relax the plasma density gradients, particularly in the J = 0-1 gain zone.

EFFECT OF WEAK PREPULSES ON COLLISIONAL X-RAY LASER PLASMAS

Through the use of time-integrated space-resolved keV spectroscopy, we characterize line plasmas showing gain in Ne-like Zn with prepulsed irradiation to explain the enhanced performances of x-ray lasers using the prepulse technique. It is observed that the value of the electron temperature does not vary significantly with prepulse level, nor does its spatially resolved profile along the line. The lateral width and density of the Ne-like region in the plasma are seen to increase with the prepulse level. (C) 1995 Optical Society of America

PRELIMINARY STUDIES OF RADIATION COUPLING BETWEEN REMOTE SOFT-X-RAY LASER-AMPLIFIERS

Coupling of a soft X-ray laser beam with a relaying concave mirror in a sequentially pumped amplifier geometry using the Ne-like Ge system has been studied experimentally. Preliminary observations indicate an increase in the spatial coherence of the amplified relayed beam. In addition, near-field imaging of one of the amplifier plasmas shows a double-lobed intensity pattern of the emergent beam indicating refractive guiding of the amplified beam with components both normal and tangential to the target surface.

A COMPUTATIONAL INVESTIGATION OF THE NEON-LIKE GERMANIUM COLLISIONALLY PUMPED LASER

The complex problem of a collisionally pumped Ne-like geranium laser is examined through several detailed models. The central model is EHYBRID; a 1 1/2D fluid code which self consistently treats the plasma expansion with the atomic physics of the Ne-like ion for 124 excited levels through a collisional radiative treatment. The output of EHYBRID is used as data for ray-tracing and saturation codes which generate experimental observables. A detailed description of the models is given.

Evidence for the direct binding of phosphorylated p53 to sites of DNA breaks in vivo

Despite a clear link between ataxia-telangiectasia mutated (ATM)-dependent phosphorylation of p53 and cell cycle checkpoint control, the intracellular biology and subcellular localization of p53 phosphoforms during the initial sensing of DNA damage is poorly understood. Using GO-G, confluent primary human diploid fibroblast cultures, we show that endogenous p53, phosphorylated at Ser(15) (p53(Ser15)), accumulates as discrete, dose-dependent and chromatin-bound foci within 30 minutes following induction of DNA breaks or DNA base damage. This biologicafly distinct subpool of p53(Ser15) is ATM dependent and resistant to 26S-proteasomal degradation. p53(Ser15) colocalizes and coimmunoprecipitates with gamma-H2AX with kinetics similar to that of biochemical DNA double-strand break (DNA-dsb) rejoining. Subnuclear micro-beam irradiation studies confirm p53 S,,15 is recruited to sites of DNA damage containing gamma-H2AX, ATM(Ser1981), and DNA-PKcs(Thr2609) in vivo. Furthermore, studies using isogenic human and murine cells, which express Ser(15) or Ser(18) phosphomutant proteins, respectively, show defective nuclear foci formation, decreased induction of p21(WAF) decreased gamma-H2AX association, and altered DNA-dsb kinetics following DNA damage. Our results suggest a unique biology for this p53 phosphoform in the initial steps of DNA damage signaling and implicates ATM-p53 chromatin-based interactions as mediators of cell cycle checkpoint control and DNA repair to prevent carcinogenesis. (Cancer Res 2005; 65(23): 10810-21).