Coloring Quasicrystals with Prescribed Symmetries and Frequencies

We show how to color the tiles in a heirarchical tiling system so that the resulting system is not only repetitive (i.e., has the local isomorphism property) but has prescribed color symmetries as well. Received March 9, 1998, and in revised form August 3, 1998.     

Deformations of Algebras Constructed using Quantum Stochastic Calculus

Deformations of associative algebras in which time is the deformation parameter are constructed using quantum stochastic flows in which the usual multiplicativity requirement is replaced by multiplicativity with respect to the deformed multiplication. The theory is restricted by a commutativity requirement on the structure maps of the flow, but examples which can be constructed in this way include the noncommutative torus and the Weyl–Moyal deformation.     

IR and visible luminescence studies in the infrared multiphoton dissociation of 1,2-dibromo-1,1-difluoroethane

The infrared multiphoton dissociation of 1,2-dibromo-1,1-difluoroethane gives rise to IR and visible luminescence. Vibrationally excited parent molecules dissociate via two primary channels yielding bromine and vibrationally excited HBr. The strong visible emission observed between 350 to 750 nm has been assigned to electronically excited carbene CF₂Br H.     

Nuclear orientation following muon capture by spin zero nuclei

It is shown that in the proposed experimental set-up of the Louvain-Saclay collaboration, the nuclei recoiling into the forward (or backward) hemisphere in the reaction $\text{μ}{}^{\mathrm{?}}\text{+ A(J}{}_{\mathrm{<mtext>i</mtext>}}\text{= 0) → B(J}{}_{\mathrm{<mtext>f</mtext>}}\text{≧ 1) + ν}{}_{\mathrm{\mu }}$ will not only be polarized but also aligned. A general expression for the alignment of the recoiling nucleus is derived in terms of the other observables and it is shown to be independent of nuclear structure and the dynamics of the muon capture interaction. Numerical results are presented for muon capture by ¹²C and ¹⁶O.     

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.