High transmission Ni compound refractive lens for high energy X-rays.

We present a new planar Ni compound refractive lens for high energy X-rays (116 keV). The lens is composed of identical plano-concave elements with longitudinal parabolic grooves manufactured by a punch technique. In order to increase the lens transmission, the thickness of the single lens at the parabolic groove vertex was reduced to less than 5 µm and the radius of curvature was reduced to about 20 µm. The small radius of curvature allowed us to reduce the number of single elements needed to get the focal length of 3 m to 54 single lenses. The gain parameter has been significantly improved compared to the previous lenses due to higher transmission, but the focused beam size and its gain are not as good as expected, mostly due to the aberrations caused by the lens shape imperfections.

Saturated ablation in metal hydrides and acceleration of protons and deuterons to keV energies with a soft-x-ray laser.

Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10(17) W/cm(2) were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10(16) W/cm(2). This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.

Isotope quantum effects in the electron momentum density of water.

The isotope quantum effects in the ground-state electron momentum density of water are studied at temperatures ranging from 5 to 90 degrees C by combining Compton scattering experiments utilizing synchrotron radiation and computational analysis within density functional theory. We observe clear differences in the momentum density between normal and heavy water at room temperature, which are interpreted as predominantly reflecting intramolecular structural differences. The changes in the momentum density upon increasing the temperature are found to be larger for heavy than for normal water, which is attributed primarily to temperature-induced intramolecular structural effects. Both model computations and an ab initio approach qualitatively reproduce the changes in the momentum density as a function of temperature.

Compton scattering study of water versus ice Ih: intra- and intermolecular structure.

The hydrogen-bond geometries in water and polycrystalline ice Ih are studied using synchrotron radiation-based Compton scattering data of unprecedented statistical accuracy and consistency. By combining the experimental data with model calculations utilizing density functional theory, we show that the technique provides unique and complementary information on hydrogen bonding in water. The comparison of water and ice indicates the necessity of including a local intra-intermolecular geometric correlation for water, relating the intramolecular O-H bond length to the corresponding hydrogen-bond geometry. By using the hydrogen-bond geometries obeying this correlation, we demonstrate a further constraint on the angular distortions of the hydrogen bonds in water.

Magnetic form factor of nickel determined by white beam x-ray diffraction.

The magnetic form factor of nickel has been measured, as a fraction of the charge form factor for {h00} and {hhh} reflections up to (10 00) and (666), by an x-ray energy dispersive white beam technique that uses elliptically polarized synchrotron radiation and single crystal samples. At low sin(θ)/λ the results are in good agreement with theory and with the values determined from neutron studies. The measurements extend beyond the current range of neutron data and indicate that significant magnetic diffraction effects are observable at sin(θ)/λ > 1.5 Å-1 if photons with energies above 26 keV can be used.

Pharmacology and toxicology of a seven-day infusion of 1-beta-D-arabinofuranosylcytosine plus uridine in dogs.

In vitro studies of certain lymphoid tumor cells show potentiation of 1-beta-D-arabinofuranosylcytosine (ara-C) effects by uridine because it elevates intracellular uridine triphosphate, resulting in increased ara-C triphosphate levels. Seven-day continuous i.v. infusions of uridine at 123 mg/kg/h (2.5 g/sq m/h) were studied in 5 male beagles. Steady state levels of uridine were reached within 4 to 6 h and ranged from 2 to 5 X 10(-4) M over the course of the infusion. Steady state uracil levels ranged from 4 to 10 X 10(-4) M. After the end of infusion, uridine and uracil levels fell with a half-life of approximately 15 and 18 min, respectively. Toxicity in 2 dogs treated at this dose was limited to minimal diarrhea and a transient rise of alkaline phosphatase to 2 to 3 times normal. No drug toxicity was evident at sacrifice on Days 7 or 72. Three dogs received a 7-day infusion of ara-C plus uridine followed approximately 4 weeks later by an infusion of ara-C alone (or the same drugs in the reverse sequence). Coinfusion of 2.5 or 5.0 mg/kg/day (50 or 100 mg/sq m/day) of ara-C had no significant effects on uridine plasma levels or postinfusion half-lives. Similarly, no consistent effect was seen of uridine on ara-C plasma levels. Uridine coinfusion with ara-C resulted in a definite potentiation of myelosuppression; at 5.0 mg/kg/day X 7 of ara-C white blood cell and platelet nadirs (X 10(3)/microliters) were 0.8 and 15 as compared to 3.6 and 66, respectively, with ara-C alone. One-third of the dogs developed reversibly elevated transaminases with the combination treatment. The results show that a minimally toxic dose of uridine enhances bone marrow and probably hepatic toxicity of coadministered ara-C.

Pharmacokinetics of vindesine given as an intravenous bolus and 24-hour infusion in humans.

The pharmacokinetics of vindesine was examined after the determination of serum drug levels by radioimmunoassay in patients who received the drug either as an i.v. bolus or a 24-hr infusion. After i.v. bolus, vindesine was eliminated from the serum by triphasic decay. The central compartment was approximately 6 times the serum volume. The peak serum level achieved by i.v. bolus was approximately 16 times that achieved by the 24-hr infusion. The post-24-hr-infusion serum decay followed biphasic decay. Pharmacokinetic modeling, assuming a prolonged infusion period, resulted in a triphasic decay curve, with an extremely short distribution phase which would not be clinically detectable. This was due to the incorporation of the distribution phase into the infusion period. This explains the experimental data of a biphasic decay curve observed after 24-hr infusion. Pharmacokinetic parameters for the two phases observed after 24-hr infusion were similar to values calculated from i.v. bolus data. The c X t for 24-hr infusion was identical to that after i.v. bolus; theoretically, the c X t appears constant regardless of infusion time. It is concluded that the rate of elimination and/or the c X t, rather than the peak serum level, played a role in the degree of hematological toxicity.