Solvent effects in the kinetics of the enantioselective hydrogenation of ethyl pyruvate

The influence of solvent on the kinetics of enantioselective hydrogenation of ethyl pyruvate by Pt/Al₂O₃/dihydrocinchonidine is reported. In a non‐polar solvent, toluene, the reaction is approximately zero order in substrate at constant hydrogen pressure, while under the same conditions and at the same substrate concentration, in the polar solvents ethanol and propylene carbonate the reaction shows a first‐order substrate concentration dependence. Fits to a Michaelis–Menten rate expression show that these differences are the expression of the relative magnitudes of the adsorption term in the rate expression, which in turn reflects the influence of the solvent on the adsorption–desorption processes which take place at the catalyst surface. This revised version was published online in July 2006 with corrections to the Cover Date.     

Papillary cystic and solid tumor of the pancreas

The papillary cystic and solid tumor of the pancrease (PCSTP) is a primary pancreatic neoplasm of unknown etiology occurring most commonly in young women and regularly containing hemorrhagic areas. Clinical symptoms are non-specific. Although these tumors reach an average diameter of 10 cm, they are often discovered by accident. Because patients with surgically resected PCSTP have very good prognoses, it is important to distinguish these tumors from other growths in the pancreas, for example mucinous cystadenoma. Whereas, due to the variable proportion of fluid components, these tumors offer non-characteristic structure at ultrasonography, computed tomography (CT) possesses high specificity for PCSTP, particularly when calcifications are present. Angiography distinguishes these tumors from hypervascular neoplasms, such as the endocrinologically inactive islet cell tumor. Magnetic resonance tomography (MRT) is especially suited for imaging the hemorrhagic areas in solid tumor formations, as well as hemorrhagic debris in the fluid portions and layer phenomena are frequently observed.     

Evaluation of Chemical Treatments for a Mixed Contaminant Soil

Treatability tests were conducted on soil from the reservoir No. 2 burning ground at the former Plum Brook Ordnance Works in Sandusky, Ohio. This soil is contaminated with explosives 2,4,6-trinitrotolune (TNT) and 2,4/2,6-dinitrotoluene (DNT), polychlorinated biphenyls (PCB, Aroclor 1260), as well as lead. Lime treatment (alkaline hydrolysis) and persulfate oxidation were tested individually and in combination to treat explosives and PCBs. Lime treatment removed 98% of TNT, 75% of DNT, and 80% of PCBs. Similar removal levels were found for persulfate treatment as well as lime followed by persulfate. The percentage of contaminant removal was found to be independent of initial contaminant concentrations. Treatments of the most contaminated soil did not meet the preliminary remediation goals for explosives or PCBs but would allow for disposal in a nonhazardous waste landfill. Treatment of soil with lower initial concentrations easily met the residential (most stringent) preliminary remediation goals of 16, 61, and 0.22?mg?kg?1 for TNT, 2,6-DNT, and PCB (Aroclor 1260), respectively. Neither alkaline hydrolysis nor persulfate oxidation transferred more than 0.02% of the lead from the soil into the reaction waters. Lead was successfully stabilized via phosphate addition.     

Ionic conductivities and glass transition temperatures in poly(vinyl methyl ether)-salt mixtures

Summary The solubility of a number of salts in poly(vinyl methyl ether) (PVME) was tested, and several gave homogeneous solutions over a range of concentrations. When dissolution of the salts occurred, the glass transition temperature of the mixture tended to rise, reflecting the solvation of the cations by the ether oxygens which also leads to crosslinking. Ionic conductivities (/Scm^–1) were measured for some of the mixtures but the level at room temperature was low. A rise in with increase in temperature was observed reaching 10^–4 Scn^–1 at 430K for PVME/LiClO₄ mixtures at a [Li⁺]/[O] ratio of 0.25.     

Performance of low-upper-shelf material under pressurized-thermal-shock loading

The second pressurized-thermal-shock experiment (PTSE-2) of the Heavy-Section Steel Technology Program was conceived to investigate fracture behavior of steel with low ductile-tearing resistance. The experiment was performed in the pressurized-thermal-shock test facility at the Oak Ridge National Laboratory. PTSE-2 was designed primarily to reveal the interaction of ductile and brittle modes of fracture and secondarily to investigates the effects of warm prestressing, A test vessel was prepared by inserting a cracklike flaw of well-defined geometry on the outside surface of the vessel. The flaw was 1 m long by ≈ 15 mm deep. The instrumented vessel was placed in the test facility in which it was initially heated to a uniform temperature and was then concurrently cooled on the outside and pressurized on the inside. These actions produced an evolution of temperature, toughness, and stress gradients relative to the prepared flaw that was appropriate to the planned objectives. The experiment was conducted in twoseparate transients, each one starting with the vessel nearly isothermal. The first transient induced a warm-prestressed state, during which K_I, first exceeded K_Ic. This was followed by repressurization until a cleavage fracture propagated and arrested. The final transient was designed to produce and investigate a cleavage crack propagation followed by unstable tearing. During this transient, the fracture events occurred as had been planned.     

Spectroscopic evaluation of CaYA1O4 doped with trivalent Er, Tm, Yb and Ho for eyesafe laser applications

Spectroscopic properties of relevance for laser applications have been studied for rare earths in CaYA1O₄. Fitting of a theoretical model to observed energy levels yields crystal field parameters and unobserved levels. Structural disorder leads to broad linewidths,but cross sections are larger than in many common hosts. Tm-Tm cross relaxation rates are comparable to those in Tm: YAG, and Yb-Er transfer rates are comparable to those in Yb, Er:phosphate glass. Room temperature Yb-Er upconversion is stronger than in YAG, but modeling shows that neither unconversion nor population of Er⁴I_13/2 is very efficient upon pumping Yb. The host's yellow color intensifies upon annealing in air, a potential problem for visible laser operation. Tm or Ho 2 μm laser operation, or Er 1.5 μ operation upon direct excitation of Er⁴I_13/2, are more promising.