Energy dependence of the freeze out eccentricity from the azimuthal dependence of HBT at STAR

Non-central heavy ion collisions create an out-of-plane-extended participant zone that expands toward a more round state as the system evolves. The recent RHIC Beam Energy Scan at sqrt{s_{NN}} of 7.7, 11.5, and 39 GeV provide an opportunity to explore the energy dependence of the freeze out eccentricity. The new low energy data from STAR complements high statistics data sets at sqrt{s_{NN}} of 62.4 and 200 GeV. Hanbury-Brown-Twiss (HBT) interferometry allows to determine the size of pion emitting source regions. The dependence of the HBT radius parameters on azimuthal angle relative to the reaction plane have been extracted. These dependencies can be related to the freeze out eccentricity. The new results from STAR are consistent with a monotonically decreasing freeze out eccentricity and constrain any minimum, suggested by previously available data, to lie in the range between 11.5 and 39 GeV. Of several models UrQMD appears to best predict the STAR and AGS data.Comment: 4 pages, 2 figures, Proceedings for the XXII International Conference on Ultra-relativistic Nucleus-Nucleus Collisions (Quark Matter 2011), 22-28 May 2011, Annecy, Franc

The Morphology of Reionization in a Dynamically Clumpy Universe

A recent measurement of the Lyman-limit mean free path at $z = 6$ suggests it may have been very short, motivating a better understanding of the role that ionizing photon sinks played in the reionization process. Accurately modeling the sinks in reionization simulations is challenging because of the large dynamic range required if gas structures on scales $\sim 10^4-10^8 M_{\odot}$ contributed significant opacity. As a result, there is no consensus on how important the sinks were in shaping reionization's morphology and its observables. We address this question with a recently developed radiative transfer code that includes a dynamical sub-grid model for the sinks based on radiative hydrodynamics simulations. Compared to assuming a fully pressure-smoothed IGM, our dynamical treatment reduces the predicted sizes of ionized bubbles by $10-20\%$ under typical assumptions about reionization's sources. Near the midpoint of reionization, the 21 cm power at $k \sim 0.1$ $h$Mpc$^{-1}$ is reduced by a similar factor. These effects are more modest than the $25-45\%$ power suppression resulting from the much higher recombination rate in models that neglect pressure smoothing entirely. Whether the sinks played a significant role in reionization's morphology depends on the nature of its sources. For example, if reionization was driven by bright ($M_{\rm UV} < -17$) galaxies, the sinks reduce the large-scale 21 cm power by at most $15\%$, even if pressure smoothing is neglected. Conveniently, when bright sources contribute significantly, the morphology in our dynamical treatment can be reproduced to high accuracy with a uniform sub-grid clumping factor that yields the same ionizing photon budget. By contrast, if $M_{\rm UV} \sim -13$ galaxies drove reionization, an accurate model of the sinks' dynamics is more important, with the uniform clumping model erring at the $20\%$ level.Comment: 17 pages, 12 figures, prepared for submission to MNRAS. Comments welcom

Synthesis and Supramolecular Structure of a (5-(3-(1H-tetrazol-5-yl)phenyl)-1H-tetrazole) Cobalt Complex

The reaction of CoCl2·6H2O with m-BDTH2 (1,3-benzeneditetrazol-5-yl) leads to [Co(C8H6N8)2(H2O)2(CH3CN)2]Cl2 (1). Both tetrazolic groups remain protonated existing in a 1H tautomeric form. A trifurcated chlorine atom and stacking interactions assemble compound 1 into a three-dimensional network

A nickel(II) complex with an unsymmetrical tetradentate chelating ligand derived from pyridine-2,6-dicarbaldehyde and 2-aminothiophenol

[(2-{[6-(1,3-Benzo­thia­zol-2-yl)pyridin-2-yl]carbonyl­aza­nid­yl}phen­yl)sulf­anido]nickel(II), [Ni(C$_{19}$H$_{11}$N$_3$OS$_2$)], crystallizes in the centrosymmetric monoclinic space group $P2_1/n$ with one mol­ecule in the asymmetric unit. The expected ligand, a bis-Schiff base derived from pyridine-2,6-dicarbaldehyde and 2-amino­thio­phenol, had modified in situ in a both unexpected and unsymmetrical fashion. One arm had cyclized to form a benzo[$d$]thia­zol-2-yl functionality, while the imine linkage of the second arm had oxidized to an amide group. The geometry about the central Ni$^{II}$ atom is distorted square-planar N$_3$S. The mol­ecules form supra­molecular face-to-face dimers via rather strong π–π stacking inter­actions, with these dimers then linked into chains via pairwise C—H$\cdot\cdot\cdot$O inter­actions

An undecanuclear ferrimagnetic Cu9Dy2 SMM achieved through ligand fine-tuning

We describe the concept of increasing the nuclearity of a previously reported high-spin Cu5Gd2 core using a “fine tuning” ligand approach. Thus two Cu9Ln2 coordination clusters, with Ln = Dy (1), Gd(2) were synthesized with the Gd compound having a ground spin state of 17/2 and the Dy analogue showing SMM behavior in zero field

Synthesis of N-(2,4-dinitrophenyl) derivatives of D-ribosylamines; unexpected reaction and hydrolysis products

Reaction of 2,3-O-isopropylidene-d-ribofuranosylamine with 2,4-dinitrofluorobenzene afforded the crystalline 2,3-O-isopropylidene-N-(2,4-dinitrophenyl)-β-d-ribofuranosylamine (3) and a 1:1 crystalline complex of 2,3-O-isopropylidene-N-(2,4-dinitrophenyl-α-d-ribofuranosylamine and 2,3-O-isopropylidene-β-d-ribofuranose; controlled acidic hydrolysis of 3 afforded N-(2,4-dinitrophenyl-α-d-ribopyranosylamine and not the expected β-d-furanosylamine derivative. The structures of the new compounds were confirmed by NMR spectroscopy and X-ray crystallography

Tetranuclear CuII2DyIII2 coordination cluster as Suzuki (C–C) coupling reaction promoter

The air stable and high yielding tetranuclear coordination cluster [CuII2DyIII2L4(NO3)2(CH3CN)2]·2(CH3CN) promotes the Suzuki coupling reaction of phenylboronic acid with substituted aryl halides in environmentally benign conditions

Synthesis, structure and electrochemical characterization of the isopolytungstate (W4O16) held by MnII anchors within a superlacunary crown heteropolyanion {P8W48}

An isopolyanion {W4O16} within archetypal {P8W48} heteropolyanion assembly [(P8W48O184)(W4O16)K10Li4Mn10Na(H2O)50Cl2] 15- (Mn10W4-P8W48) has been synthesized by the reaction of the cyclic superlacunary anion [H7P8W48O184] 33− and Mn(ClO4)2.6H2O in I M LiCl soultion medium at pH 8. The isolated compound has been characterized by single crystal X-ray crystallography, powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy, elemental analysis and thermogravimetric analysis. Electrochemical studies were also performed on Mn10W4-P8W48 confirmed the presence of Mn centres bonded to the tunsgtic framework. The novel polyanion [(P8W48O184)(W4O16)K10Li4Mn10Na(H2O)50Cl2] 15- is the first example of macrocyclic complex where an isopolyanion (W4O16) 8- is embedded within in the inner cavity of the {P8W48} and is placed in position by six MnII cations as anchors. Whereas, the exocyclic coordination of the four MnII atoms to {P8W48} yields extended structure by linking neighbouring polyanions through {W−O−Mn−O−W} bridges. Further, the polyanion Mn10W4-P8W48 is the first derivative of {P8W48} with six MnII ions (largest) coordinated to the inner side the crown ring as anchors

Systematic studies of hexanuclear {MIII4LnIII2} complexes (M = Fe, Ga; Ln = Er, Ho): structures, magnetic properties and SMM behavior

Four isostructural MIII4LnIII2 coordination clusters, [M4Ln2(μ3-OH)2(nbdea)4(C6H5COO)8]•MeCN (M = Fe, Ln = Er (1); M = Ga, Ln = Er (2); M = Fe, Ln = Ho (3); M = Ga, Ln = Ho (4)) have been synthesized and characterized. Single-crystal X-ray diffraction and X-ray powder diffraction studies revealed that all four compounds crystallize isomorphously to each other, and to the previously reported MIII4DyIII2 (M = Fe or Ga) and FeIII4YIII2 analogues. DC magnetic susceptibility measurements for compounds 1-4, taken in combination with those for the FeIII4YIII2 analogue, indicated that the interactions between ErIII ions are weakly ferromagnetic and the FeIII-ErIII interactions are very weakly antiferromagnetic, while the HoIII-HoIII and FeIII-HoIII interactions are both negligible. By comparison, for the FeIII4DyIII2 analogue, the DyIII-DyIII interactions are antiferromagnetic while the FeIII-DyIII are ferromagnetic. Both Er analogues 1 and 2 display single-molecule magnet (SMM) behavior with the effective energy barrier Ueff increasing from 12.8 K (for Fe4Er2 1) to 53.5 K (for Ga4Er2 2), indicating that the very weak 3d-4f interaction enhances the QTM effect