Laser isotope separation of 13C: A comparative study

IR laser chemistry of (CF₃Br/Cl₂) mixture and neat CF₂HCl are examined in the context of ¹³C enrichment. Decomposition extent, enrichment factor and energy absorbed are measured for both systems at their respective optimum conditions. A direct comparison is obtained by keeping extraneous factors such as laser, its pulse duration, cell, irradiation geometry etc. the same. The halogen scavenged CF₃Br MPD requires lower fluence compared to neat CF₂HCl irradiation. Overall throughput for a product with 60–65% ¹³C content in a single stage is the same for both systems requiring a similar amount of energy. However, at lower enrichment levels, CF₂HCl MPD is better than (CF₃Br/Cl₂) photolysis in terms of both product yield and energy absorption.     

Planckian Scattering from Kerr Black Holes: Eikonal and Beyond

Planckian scattering of particles with angular momenta is studied by describing them as sources of the Kerr metric. In the shock wave formalism, it is found that the angular momenta do not contribute to the scattering amplitude in the eikonal limit. This is confirmed by using the wave equation of the test particle in the Kerr background.     

A copositive Q-matrix which is notR 0

Jeter and Pye gave an example to show that Pang's conjecture, thatL ₁ ?Q ?R ₀, is false while Seetharama Gowda showed that the conjecture is true for symmetric matrices. It is known thatL ₁-symmetric matrices are copositive matrices. Jeter and Pye as well as Seetharama Gowda raised the following question: Is it trueC ₀ ?Q ?R ₀? In this note we present an example of a copositive Q-matrix which is notR ₀. The example is based on the following elementary proposition: LetA be a square matrix of ordern. SupposeR ₁ =R ₂ whereR _i stands for theith row ofA. Further supposeA ₁₁ andA ₂₂ are Q-matrices whereA _ii stands for the principal submatrix omitting theith row andith column fromA. ThenA is a Q-matrix.     

N-1 and C-2 substituted tryptophans as potential inhibitors of sickle cell hemoglobin gelation

A series of N-1 or C-2 phenylalkyl substituted tryptophans and C-1 phenylalkyl substituted 3,4-dihydro-β-carbolines were prepared from the apropriate aniline, 1b or 1e , or tryptophan, 8 or 11 , by ring closure methods. None of the compounds prepared were more potent than 5-bromotryptophan (11) as inhibitors of sickle cell hemoglobin gelation.     

Synthesis of a pyridinium bis[citrato(2-)]oxochromate(V) complex and its ligand-exchange reactions

The reaction of citric acid (caH(4)) with pyridinium dichromate (PDC) in anhydrous acetone yields pyridinium bis[citrato(2-)]oxochromate(V), pyH[CrO(caH(2))(2)], as a mixed salt with the Cr(III) product. The compound persists in the solid state for months, is highly soluble in water (pH 4.0), and gives a sharp electron paramagnetic resonance (EPR) signal in solution (g(iso) = 1.9781, A(iso)(Cr) = 17.1 x 10(-4) cm(-1)), which is characteristic of d(1) Cr(V). The presence of [Cr(V)O(caH(2))(2)](-) in the solid state was confirmed by electrospray mass spectroscopy, X-ray absorption near-edge structure (XANES), and EPR spectroscopy. Solid-state EPR spectroscopy, XANES, and a spectrophotometric assay showed that the solid is a mixture of [Cr(V)O(caH(2))(2)](-) and a Cr(III)-citrate complex. The structures of the [Cr(V)O(caH(2))(2)](-) and [Cr(III)(caH(2))(2)](-) components of the mixture were established by multiple-scattering MS analysis of the X-ray absorption fine structure data. The structure of [Cr(V)O(caH(2))(2)](-) is similar to that of other 2-hydroxy acid complexes with Cr=O, Cr-O(alcoholato), and Cr-O(carboxylato) bond lengths of 1.59, 1.81, and 1.90 A, respectively. The Cr(III) complex has bond lengths typical for ligands with deprotonated carboxylate and protonated alcohol donors with distances of 1.90 and 1.99 A, respectively, for the Cr-O(carboxylato) and Cr-O(alcohol) bond lengths. In aqueous solution, [CrO(caH(2))(2)](-) is short lived, but it is a convenient starting material for ligand-exchange reactions. It has been used to generate short-lived mixed-ligand Cr(V) complexes with citrate and picolinate, iminodiacetate, 2,2'-bipyridine, or 1,10-phenanthroline, which were characterized by EPR spectroscopy. The g values are between 1.971 and 1.974. For the picolinate, 2,2'-bipyridine, and 1,10-phenanthroline mixed-ligand complexes, there is hyperfine coupling (2.2 x 10(-4) to 2.4 x 10(-4) cm(-1)) to a single proton of the citrate ligand.     

Cohomology of power sets with applications in quantum probability

Square integrable Wiener functionals may be represented as sums of multiple Itô integrals. This leads to an identification of such functionals with square integrable functions on the symmetric measure space of the Lebesgue spaceR ₊. When the pointwise product of Wiener functionals is thus carried over, the product takes a pleasing form (cf. Wick's theorem) and various non-commutative perturbations of this Wiener product have been considered. Here we employ cohomological arguments to analyse deformations of an abstract Wiener product. This leads to the construction of Lévy fields which are neither bosonic nor fermionic, and also gives rise to homotopies between quasi-free boson and fermion fields. Finally we unify existence and uniqueness results for quantum stochastic differential equations by treating mixed noise differential equations.Address from September 1988; Department of Mathematics, King's College, London WC2R2LS, UK