Highly enantioselective oxidations of ketene dithioacetals leading to trans bis-sulfoxides

Ketene dithioacetals undergo a Sharpless-type asymmetric oxidation using (+)-DET, Ti(O(i)()Pr)(4), and cumene hydroperoxide to give the trans bis-sulfoxides 4a-f with essentially complete control of enantioselectivity and diastereoselectivity. The high enantioselectivity is a consequence of carrying out two asymmetric processes on the same substrate. However, this should lead to the formation of a small amount of the meso isomer but none was isolated. From monitoring the enantioselectivity of the monoxide over time, it was concluded that small amounts of the meso isomer must be formed. The inability to isolate this compound could be because it acted as a ligand on titanium and remained tightly bound even upon workup.     

Evidence from d+Au measurements for final-state suppression of high-p(T) hadrons in Au+Au collisions at RHIC

We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high p(T)) in minimum bias and central d+Au collisions at sqrt[s(NN)]=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high p(T) previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.     

A μSR-study of UP and UTe

The materials crystallize in the NaCl structure. UP undergoes at 122 K a first order transition into a type I single-k antiferromagnetic state, followed by a second first order transition into a type I double-k-structure at 22 K. UTe is a ferromagnet withT _c =104 K. The two first order transitions of UP reveal themselves by abrupt changes of the transverse field damping rate. No spin rotation is observed in zero field for both antiferromagnetic spin structures which is in keeping with point dipolar lattice sums. In UTe we observe the characteristic critical behavior: a rapid increase of damping rate and paramagnetic frequency shift when approachingT _c from above. In the ferromagnetic regime the spin rotation in zero field damps out too rapidly to be observed. This work has been funded in part by the German Federal Minister for Research and Technology (BMFT) under contract Nr. 03-KA1-TUM-4.     

Charm production in 400 GeV/c proton-emulsion interactions: Bombay-Chandigarh-Delhi-Jammu Collaboration

5032 proton-emulsion interactions at 400 GeV/c momentum have been carefully scrutinized for production and decay of charged charm particles. In order to detect these decays, shower tracks from 3056 stars have been followed to a maximum length of 1 mm and those from 1976 stars up to 2 mm. A total of 23 three-prong charm-like candidates have been recorded in the forward cone. The background due to γ-overlap on a shower track, trident/pseudo-trident production and secondary interactions is estimated to be 15. Attributing the signal of 8 events to Λ_c⁺ and assuming the branching ratio of Λ_c⁺ → 3 prong to be 0.6 and τ_Λc to be 10^?13 sec we obtain the production cross section to be 106±39μb/nucleon. Out of these 8 events one example of semileptonic decay of Λ_c⁺ is seen.     

Removal of fission products from mixed solvents using zeolites

The solvents tributylphosphate (TBP) and odourless kerosene (OK) are widely used to extract plutonium(IV) and uranium(V) in nuclear processing plants. Although these solvents are chosen because of their low affinity for fission products it is, nevertheless, of value to study ways of removing the small quantities of fission products, such as isotopes of Cs, Sr and Ru, which can be present in the solvents. This paper describes simple distribution coefficients (K _d) measurements made to test the ability of the aluminosilicate zeolites to remove¹⁰⁶Ru from TBP, OK, and their mixtures.     

An algorithmic decomposition system for second order recurrence relations

A new technique of accurate stable computation of sequences satisfying non-homogeneous three term recurrence relations is presented. A decomposition system consisting of one non-linear and two linear first order recurrence relations is obtained. Forward or backward recursion directions of the linear relations provide additional flexibility in computation. This leads to an integrated system of three algorithms which can accurately compute the desired solution in each region of the solution set to the original second order relations. Applications are well known and numerical examples include Bessel functions of the second kind, Anger-Weber functions, and Lommel functions.     

Location and estimation of the defective area in a diaphragm: an a posteriori moiré method

A moiré method based on holographic interferometry is shown to be a powerful tool for non-destructive testing of diaphragms.     

Noncollinear phase-matched four-photon mixing of CO2 laser radiation in germanium

Noncollinear four photon mixing of two TEA CO₂ laser beams in germanium at room temperature has been used to obtain phase-matched generation of step tunable radiation in the 8.7 μm region which is of interest for the uranium isotope separation. Using an 8.3 cm long crystal of germanium, peak output power of ≈10kW (corresponding to 1 mJ per pulse) was obtained at 8.7 μm with 3 MW peak input power from each of the two CO₂ lasers operating at 9.6 μm and 10.6 μm.     

Phase knife-edge laser Schlieren diffraction interferometry with boundary diffraction wave theory

Within the framework of boundary diffraction wave theory it has been shown that the first bright fringe on either side of the central dark fringe of the phase knife-edge Fresnel diffraction pattern could be broadened to cover the whole field of view. Broadening of the first diffraction fringe, instead of conventionally modifying the spatial frequency spectrum, enhances the sensitivity of the Schlieren system. The use of phase knife-edge as viewing diaphragm in Schlieren diffraction interferometry not only enhances the fringe contrast but also avoids the loss in phase information as it lets through light from all parts of the test object and its thin interfacing makes the method suitable even for studying weak disturbances.