High-brightness injection-seeded soft-x-ray-laser amplifier using a solid target

We demonstrate the generation of an intense soft-x-ray-laser beam by saturated amplification of high harmonic seed pulses in a dense transient collisional soft-x-ray-laser plasma amplifier created by heating a titanium target. Amplification in the 32.6 nm line of Ne-like Ti generates laser pulses of subpicosecond duration that are measured to approach full spatial coherence. The peak spectral brightness is estimated to be approximately 2 x 10(26) photons/(s mm(2) mrad(2) 0.01% bandwidth). The scheme is scalable to produce extremely bright lasers at very short wavelengths with full temporal and spatial coherence.     

High resolution fluorescence spectroscopy by use of a CW dye laser

The hyperfine structure of the Na D₂-line was investigated in a fluorescence experiment involving a narrow band tunable dye laser and a highly collimated atomic beam. The observed linewidth was less than 16 MHz (natural line-width 10 MHz). All hyperfine components were resolved.     

Physical properties of organic particulate UV absorbers used in sunscreens II. UV-attenuating efficiency as function of particle size

In this study the UV-attenuating properties of microparticles consisting of a benzotriazole derivative were investigated, which are used as absorbers for UV radiation in cosmetic sunscreens. The particles were micronized in presence of a dispersing agent by means of a ball milling process. According to the energy input different particle sizes were produced in the range of 0.16 to 4 microm. In order to study even smaller particles, the sample with particle size 0.16 microm was fractionated further by centrifugation. Particle sizes were measured using fiberoptic quasi-elastic light scattering (FOQELS) and laser diffractometry. The UV-attenuating properties of the dispersions with different particle sizes were assessed using UV spectroscopy. With decreasing particle size the efficiency of the UV extinction of the dispersion increases up to a particle size of 80 nm. For particles smaller than 80 nm the UV extinction decreases again indicating an optimum at 80 nm. From reflection spectroscopic measurements it was found that scattering makes about 10%, and absorption 90%, of the UV-attenuating effect of the particles, which are obtained at the end of the milling process.     

Determination of stability constants for metal-ligand complexes using the voltammetric oxidation wave of the anion/ligand and the DeFord and Hume formalism

The voltammetric oxidation peaks for anions and other ligands that react at the Hg electrode can be used for the determination of stability constants of metal-ligand complexes using the DeFord and Hume formalism. Metal-ligand complexes with known stability constants that span the range of logbeta=2.9-5.9 were determined using the oxidation wave of the ligand as metal was varied. For the larger stability constants, it was possible to titrate concentrations of metal to ligand that are smaller than the ligand concentration and obtain reliable data (beta(j)C(x)(j) approaches 1 in this case) indicating that an excess of titrant is not required to obtain reliable beta values. Data reduction with different versions of the Solver tool (included with Microsoft Excel) is discussed and blind use of these programs without knowledge of the physical chemistry of the system is discouraged. The use of Solver gives beta values that are in agreement with previous work that used (non)linear regression to evaluate each F(n)(X) versus [X] function.     

Preparation of 3(5)-phenyl-1-hydroxypyrazole 2-oxide and 4-methyl-3(5)-phenyl-1-hydroxypyrazole 2-oxide

Nitrosation of acrylophenone oxime or of methacrylophenone oxime with n-butyl nitrite in the presence of pyridine and copper(II) sulfate gives the copper complexes of the title compounds. The free 1-hydroxypyrazole 2 -oxides are isolated by treating the copper complexes with dilute sodium hydroxide, filtration, and acidification of the basic filtrates. The title compounds are the first examples of 1-hydroxypyrazole 2 -oxides in which the C3(5) ring position is unsubstituted.     

Physical properties of organic particulate UV-absorbers used in sunscreens. I. Determination of particle size with fiber-optic quasi-elastic light scattering (FOQELS), disc centrifugation, and laser diffractometry

In this study microparticles consisting of a benzotriazole derivative, which are used as absorbers for UV radiation in cosmetic sunscreens, were investigated. The particles were micronized in presence of a dispersing agent by means of a ball milling process. According to the energy input different particle sizes were produced in the range of 0.16 to 4 microm. The particle sizes obtained after different stages of the micronization process were measured using fiber-optic quasi-elastic light scattering (FOQELS), disc centrifugation, and laser diffractometry. All methods showed satisfactory agreement over the whole range of sizes. With the FOQELS technique the particle size distribution could be resolved to sizes well below 0.1 microm.     

Reference materials for PAHs in foodstuffs: Results of the certification exercise of two coconut oil reference materials

This certification exercise was the final stage of a stepwise interlaboratory study approach, organized within the SMT-program of the EC, for the development of certified reference materials (CRMs) for the determination of PAHs in foodstuffs. The certification exercise was carried out by thirteen European laboratories using a variety of extraction and clean-up procedures and different analytical procedures. Two different coconut oil materials were certified for their mass fractions of six selected PAHs. Received: 25 May 1997 / Revised: 5 September 1997 / Accepted: 28 September 1997     

Equitably Colored Balanced Incomplete Block Designs

In this paper, we determine the necessary and sufficient conditions for the existence of an equitably ?‐colorable balanced incomplete block design for any positive integer . In particular, we present a method for constructing nontrivial equitably ?‐colorable BIBDs and prove that these examples are the only nontrivial examples that exist. We also observe that every equitable ?‐coloring of a BIBD yields both an equalized ?‐coloring and a proper 2‐coloring of the same BIBD.     

Experimental and modelling study of the recombination reaction H + O(2) (+M) --> HO(2) (+M) between 300 and 900 K, 1.5 and 950 bar, and in the bath gases M = He, Ar, and N(2)

The recombination reaction H + O(2) (+M) --> HO(2) (+M) was studied by laser flash photolysis in a high pressure flow cell, over the temperature range 300-900 K, the pressure range 1.5-950 bar and in the bath gases M = He and N(2). Earlier experiments by Hahn et al. (Phys. Chem. Chem. Phys. 2004, 6, 1997) in the bath gas M = Ar were also extended. The data were analyzed in terms of unimolecular rate theory employing new calculations of relevant molecular parameters. Improved energy transfer parameters for the bath gases M = He, Ar, N(2), and H(2)O could thus be obtained and complete falloff curves were constructed. In the case of water, the high pressure rates well connect with pulse radiolysis results obtained in supercritical water by Janik et al. (J. Phys. Chem. A 2007, 111, 79).