Ultraviolet protection factors for clothing: an intercomparison of measurement systems

In recent years the need to standardize measurement protocols for quantifying the degree of ultraviolet radiation (UVR) protection provided by clothing has led to the introduction of a number of standards around the world. To date, these standards have specified spectral measurements of UVR transmission by clothing and fabrics. Development of a standard test method has become an important part of the testing process, and this article presents results from an intercomparison involving 10 independent testing laboratories and 11 different UVR transmission measurement instruments. In addition to comparing the measured ultraviolet protection factors (UPF), this intercomparison also incorporates detailed scan results from all 10 laboratories and highlights differences in performance of the various instruments in different wavelength regions. Careful examination of these differences can indicate where changes to the systems could be made to allow improvements both in equipment performance and in agreement of the final results. The variability in the measurements of UPF in this study suggest that the protection categories in standards may need to be broadened.     

The Caenorhabditis elegans Y87G2A.14 Nudix hydrolase is a peroxisomal coenzyme A diphosphatase

Background  

The number of Nudix hydrolase family members varies widely among different organisms. In order to understand the reasons for the particular spectrum possessed by a given organism, the substrate specificity and function of different family members must be established.     

Kinetic equations for a quantum gas with bound states

The kinetic theory for dense gases is modified to take into account the existence of bound states. A molecular chaos condition is used which corresponds to the division of the two- and three-particle Hubert spaces into scattering and boundstate subspaces. A kinetic stage results from a long-time limit which converges to yield time-independent functionals for the two- and three-particle density matrices, as functionals of the density matrices for atoms and molecules. Coupled kinetic equations are obtained which describe the gas as a reacting mixture of atoms and diatomic molecules. These include the effects of scattering and rearrangement collisions between the atom and the molecule, and of molecular formation and dissociation.     

Selective Homogeneous Palladium(0)-Catalyzed Hydrogenation of Alkynes to (Z)-Alkenes

Zero-valent palladium precatalysts containing rigid bidentate bis(arylimino)acenaphthene ligands (shown schematically) facilitate the highly stereoselective homogeneous catalytic hydrogenation of alkynes to (Z)-alkenes. Internal, terminal, aryl-substituted, and cyclic alkynes are suitable substrates, as are some enynes, which are chemoselectively hydrogenated to dienes. E=CO(2)Me; R(1), R(2)=4-OCH(3), 4-CH(3), 2,6-(CH(3))(2).     

Ethynylgold(I) complexes

Reactions between R₃PAuCl, NaOEt, and HCCR′ under mild conditions produce R₃PAuCCR′ in excellent yield. When R′ = H, a second step leading to the formation of R₃PAuCCAuPR₃ can take place. Exchange reactions of ethynyl for chloride between the ethynylgold complexes and HgCl₂, cis-[PtCl₂L₂cis-[PtCl₂(CO)L], and R₂″PAuCl have been monitored, revealing R₃PAuCCR′ to be useful alkynylating agents. In the reaction with cis-[PtCl₂(CO)L], the first substitution step is non-specific.     

Reactions of coordinated trimethylphosphite with binary fluorides

Fluorination of free trimethylphosphite by phosphorus pentafluoride or tungsten hexafluoride involves complex formation followed by rapid F-for-OCH₃ exchange and Michaelis-Arbusov rearrangement reactions (D.W.A. Sharp et al., $\text{J. Chem. Soc. A}$, 1969, 872; J.M. Winfield et al., $\text{ibid}$, 1970, 501). Reactions between WF₆ or PF₅ and P(OCH₃)₃, coordinated to Fe^II (low spin d⁶-inert) or Cu^I (d¹⁰ -labile) cations in CH₃CN, counter anions PF₆^? or AsF₆^?, are very different as evidenced by an n.m.r. study.Reactions between Fe^IIP(OCH₃)₃ and WF₆ are very slow at room temperature; the major products are CH₃PF₄ and WOF₄.NCCH₃. Reactions between Cu^IP(OCH₃)₃ and WF₆ or PF₅ are rapid, even below room temperature, and depend on the stoicheiometry. The major products are W₂O₂F₉^? and a PF₅X^? species, or OPF₃, minor products include CH₃OPF₂, (CH₃O)₂PF, and PF₃. When the mole ratio coordinated P(OCH₃)₃:WF₆ is 1:1, additional W₂O₂F₉ and PF₅X n.m.r. signals are observed.The reactions involve fluorination of free P(OCH₃)₃ whose concentration in solution is limited by the metal cation, and in the reaction between PF₅ and Cu^IP(OCH₃)₃ PF₅.P(OCH₃)₃ has been identified as the initial product. Conventional Michaelis-Arbusov rearrangements are of minor importance as CH₃CN acts as a sink for CH₃⁺, but the final step in the formation of CH₃PF₄ is of this type.     

Photoelastic determination of stresses in multiple-pin connectors

The design, fabrication, and testing of photoelastic models of double-lap, multiple-pin connectors are discussed. Interest is in the stresses in the inner laps. These stresses are determined by constructing models with photoelastic inner laps and transparent-acrylic outer laps. The connectors have two pins, in tandem, parallel to the load direction. A photoelastic-isotropic point is shown to permit the evaluation of load sharing between the two pins. A numerical scheme, utilizing the isochromatic- and isoclinic-photoelastic data and a finite-difference representation of the planestress equilibrium equations, is used to compute the stresses around the two pins. Representative stress distributions and stress-concentration factors are shown.