Kaon interferometry in heavy-ion collisions at the CERN SPS

K⁺K⁺ and K^–K^– correlations from S+Pb collisions at 200 GeV/c per nucleon and K⁺K⁺ correlations from p+Pb collisions at 450 GeV/c per nucleon, are presented as measured by the focusing spectrometer of the NA44 experiment at CERN. Multidimensional fits are performed in order to characterize the kaon-emission volume, which is found to be smaller than the pion-emission volume.     

Critical behavior in the relaminarization of localized turbulence in pipe flow

The statistics of the relaminarization of localized turbulence in a pipe are examined by direct numerical simulation. As in recent experimental data [J. Peixinho and T. Mullin, Phys. Rev. Lett. 96, 094501 (2006)10.1103/PhysRevLett.96.094501], the half-life for the decaying turbulence is consistent with the scaling (Rec-Re) -1, indicating a boundary crisis of the localized turbulent state familiar in low-dimensional dynamical systems. The crisis Reynolds number is estimated as Rec=1870, a value within 7% of the experimental value 1750. We argue that the frequently asked question, of which initial disturbances at a given Re trigger sustained turbulence in a pipe, is really two separate questions: the "local phase space" question (local to the laminar state) of what threshold disturbance at a given Re is needed to initially trigger turbulence, followed by the "global phase space" question of whether Re exceeds Rec at which point the turbulent state becomes an attractor.     

A new representation for the dynamic green's tensor of an elastic half-space or layered medium

A method for inverting the transforms of the terms in generalized ray series representations for disturbances in layered media is presented. It differs from the Cagniard reduction in that the solution of algebraic equations depending upon position x and time t is not required. This step is, in effect, replaced by contour integration of relatively simple functions. The method is applicable to anisotropic layers but it simplifies when applied to isotropic layers, for which any term in the ray series is represented as a single contour integral, around a fixed contour, of the product of a function that embodies material properties and a simple explicit function of x and t. The ‘material function’ can be tabulated and used repeatedly when the integral is evaluated for a range of values of x and t, so that the procedure is computationally quite efficient. It is illustrated by a computation of Green's function for an isotropic half-space, either free or overlaid by a fluid. Wave-front singularities are obtained explicitly from the representation and are given in an appendix.     

Protecting group free syntheses of (±)-columbianetin and (±)-angelmarin

A five-step and protecting group free synthesis of (±)-columbianetin from cyclohexane-1,3-dione is reported. The former compound was converted into its p-hydroxycinnamate derivative, (±)-angelmarin, using Coster’s esterification procedure. Efforts to modify the synthesis so as to prepare angelmarin and columbianetin in an enantioselective manner are described.     

The total synthesis of the crinine alkaloid hamayne via a Pd[0]-catalyzed intramolecular alder-ene reaction

The racemic form of the title alkaloid, 1, has been prepared in 13 steps from the ring-fused gem-dibromocyclopropane 7. Key transformations include the thermally induced electrocyclic ring-opening of compound 7, the Pd[0]-catalyzed intramolecular Alder-ene (IMAE) reaction of the derived sulfonamide (±)-12, and the conversion of the ensuing C-3a-arylhexahydroindole (±)-16 into (±)-hamayne via a Pictet-Spengler reaction.     

Theoretical study of the stability and electronic structure of Al(BH4)n=1→4 and Al(BF4)n=1→4 and their hyperhalogen behavior

Using density functional theory (DFT), we have systematically calculated the equilibrium geometries, electronic structure, and electron detachment energies of Al(BH(4))(n=1→4) and Al(BF(4))(n=1→4) at the B3LYP/6-311+G(2d,p) level of theory. The electron affinities of Al(BH(4))(n) not only exhibit odd-even alternation, just as seen in (BH(4))(n), but also, for n = 3 and 4, show a remarkable behavior: whereas the electron affinities of BH(3) and BH(4) are, respectively, 0.06 and 3.17 eV, those of Al(BH(4))(3) and Al(BH(4))(4) are 0.71 and 5.56 eV. Results where H is replaced by F are also very different. The electron affinities of BF(3) and BF(4) are, respectively, -0.44 and +6.86 eV, and those of Al(BF(4))(3) and Al(BF(4))(4) are 1.82 and 8.86 eV. The results demonstrate not only marked difference when H is replaced by F but also substantially enhanced electron affinities by almost 2 eV when BH(4) and BF(4) units are allowed decorate a metal atom, confirming the recently observed hyperhalogen behavior of superhalogen building blocks.     

Ring fragmentation processes resulting from acid catalysed diazo ketone cyclisations

The initial products from the cyclisation of hexahydrophenanthryl diazo ketones with participation by either the alkene bonds or the aromatic ring (Ar_1,4) undergo rearrangement by 1,2 bond shifts or unexpected bond fission. Benzocyclo-octanyl ketones were formed from the latter process.     

Cost of power—the user's perspective

With the advent of fiber in the loop, transmission of power ceases to be through the traditional communications medium, and the objective of powering voice lines over fiber with the same reliability goals as plain old telephone service (POTS) raises several technological, regulatory, and business issues. In order to power the optical network unit (ONU) and provide backup power for it during commercial power outages, three strategies are identified: 1) providing loop powering from a -48 volt CO/CEV power plant; 2) providing power and backup power locally, from or near the end of the loop in proximity to the OW; and 3) providing power from the curb or a power node. This paper constructs economic models to determine the worth of a watt at the 5-volt logic level at an ONU for each of the powering strategies. By normalizing all costs to the worth of a watt, comparisons can be made and appropriate architectures can be selected for various applications.