Centrality dependence of charged particle multiplicity in Au-Au collisions at square root of (s)NN = 130 GeV

We present results for the charged-particle multiplicity distribution at midrapidity in Au-Au collisions at square root of [s(NN)] = 130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find dN(ch)/d eta(vertical line eta = 0) = 622+/-1(stat)+/-41(syst). The results, analyzed as a function of centrality, show a steady rise of the particle density per participating nucleon with centrality.     

The Reaction of Coumalic Acid with Benzoquinone: Formation of a Spirobutenolide

Abstract

Although additions of α-pyrones to dienophiles have received extensive study,¹ there have been few reports of additions of α-pyrones to quinones.² In attempts to add benzoquinone (1) to coumalic acid (2), we have found that keeping these compounds in methanol and acetic acid in the presence of sodium acetate for 4 hours at 0°C followed by removal of the solvents under reduced pressure and purification by flash chromatography gave compound 3 ³ (22%⁴) mp 158–161°C raised to mp 160–162°C (benzene) UV (MeOH) λ;306 nm (ε 4700), 215 (12,500); IR (CHCl₃) v_max 3340, 1770 cm^?1; ¹H NMR ((CD₃)₂CO) δ 3.5 (s, 3H), 5.52 (s, 1H), 6.35 (d, J=5 Hz, 1H), 6.55 (m, 1H), 6.85 (m, 2H), 7.55 (d, J=5 Hz, 1H); ¹³C 171.5, 153.8, 153.4, 150.9, 122.3, 121.8, 119.6, 111.8, 110.8, 94.7, 56.9; mass specteum m/e (relative intensity) 234.0530 (54), 202.0267 (100), 174.0320 (34), 146.0367 (88), 98.0371 (47); m/e calcd for C₁₂H₁₀O₅.     

Application of Mössbauer Spectroscopy to the Study of Corrosion

Corrosion research, and the need to fully understand the effects that environmental conditions have on the performance of structural steels, is one area in which Mössbauer spectroscopy has become a required analytical technique. This is in part due to the need to identify and quantify the nanophase iron oxides that form on and protect certain structural steels, and that are nearly transparent to most other spectroscopic techniques. A review is given of the most recent Mössbauer characterization of rusts that have formed on structural steels exposed to different environments. Mössbauer spectroscopy is playing an important role in a new corrosion program in the United States in which steel bridges, old and new, are being evaluated for corrosion problems that may reduce their serviceable lifetimes. Mössbauer spectroscopy has been used to characterize the corrosion products that form the protective patina on weathering steel, as well those that form in adverse environments in which the oxide coating is not adherent or protective to the steel. Mössbauer spectroscopy has also become an important analytical technique for investigating the corrosion products that have formed on archeological artifacts, and it is providing guidance to aid in the removal of the oxides necessary for their preservation.     

Pi-donor/acceptor effect on Lindqvist type polyoxomolibdates because of various multiple-bonded nitrogenous ligands

The electronic structures of Lindqvist type functionalized polyoxometalates (POM) ([Mo6O18R]n- R=O, NO, NAr, NNAr, NNAr2; n=2, 3) have been investigated using density functional methods. We discuss the role of the replacement of terminal oxo ligands by pi-donor/acceptor multiple-bonded nitrogenous ligands on the basis of geometrical parameters, charge analyses, reactivity indexes, and vibrational spectra. The calculated reactivity indexes (chemical potential, electronegativity, hardness, and electrophilicity) indicate that the most reactive functionalized POMs are those substituted by pi-acceptor ligands. These pi-acceptor ligands induce a decrease in the hardness and an increase in the chemical potential and electrophilicity, thus increasing the reactivity. Our calculations are in reasonable agreement with reported experimental data.     

A new copper(I) coordination polymer from 2,6-bis(1H-benzotriazol-1-ylmethyl)pyridine: Synthesis,characterization, and use as additive in transparent submicron UV filters

The use of a new copper(I) coordination polymer (CP) as additive in transparent composite films of 190 nm of thickness for ultraviolet (UV) shielding is presented. The luminescent 1-D Cu(I) CP was easily synthesized through a self-assembly process between Cu(I) iodide and 2,6-bis(1H-benzotriazol-1-ylmethyl)pyridine (L). The CP, [Cu₂(μ ? I)₂(μ ? L)₂]_n, was structurally characterized by infrared, UV–visible diffuse reflectance and photoluminescence spectroscopy, elemental and thermogravimetric analyses, single-crystal and powder X-ray diffraction, and relativistic density functional theory calculations. The CP was dispersed and immobilized into a polymeric matrix in the presence of Sudan I, yielding a composite material that exhibits a reduction of 49% of the UV transmittance at 350 nm. Thus, the use of a new Cu(I) CP in polymeric composite films appears as a novel approach toward ultrathin and transparent UV shielding films, which have potential applications as protection layers of paints and coatings that tend to degrade when exposed to UV radiation.     

A short-chain dehydrogenase/reductase from Vibrio vulnificus with both blue fluorescence and oxidoreductase activity

A dual function blue fluorescent protein from Vibrio vulnificus is also an NADPH-dependent oxidoreductase, rendering it a useful tool for biophysical studies.     

Highly enantioselective synthesis of anti aryl β-hydroxy α-amino esters via DKR transfer hydrogenation

An efficient preparation of highly enantiomerically enriched aryl β-hydroxy α-amino esters via dynamic kinetic resolution (DKR), asymmetric transfer hydrogenation of α-amino β-keto esters is described. The anti β-hydroxyl α-amino esters were obtained both in high yields and high diasteroselectivity. The observed high anti selectivity is inconsistent with the previous results in literature. The absolute stereochemistry of the aryl β-hydroxy α-amino esters was unambiguously confirmed via chemical derivatization as well as Vibrational Circular Dichroism (VCD) techniques.     

Relativistic calculations of aminotroponiminate complexes containing group 15 (P, As, Sb, Bi) elements

The relativistic electronic structure calculations of N,N′-chelated pnictogenium cations containing aminotroponiminate units, (E = P(1), As(2), Sb(3), Bi(4)), have been investigated employing density functional (DF) methods, including spin-orbit relativistic corrections, via the two-component zeroth order regular approximation (ZORA) Hamiltonian. The role of replacement of the pnictogen atom when going down into the 15 group was discussed on the basis of geometrical parameters, Hirshfield charge analyses, DF reactivity indexes. The degree of electronic delocalization into the five- and seven membered rings was estimated via the electron localization function (ELF) and the nuclear independent chemical shifts (NICS) indexes.Our results show an existence of a lack of systems 2-4 to act as donor ligands for the metal complexation, compared with 1, due to the positive charge over the pnictogen atoms besides the lone-pair orbital of the pnictogen atom which lies at low energies from their corresponding reacting HOMO’s. It is also interesting to note some effects over the aromaticity when going down into the 15 group, i.e., the C₅ ring is affected by the change of the pnictogen atom, while the aromaticity on the C₇ ring is not affected, as suggested by the analysis of the ELF, NICS and geometrical parameters.     

Cannabisol, a novel Δ-THC dimer possessing a unique methylene bridge, isolated from Cannabis sativa

Cannabisol (1), a unique dimer of Δ⁹-tetrahydrocannabinol (Δ⁹-THC) with a methylene bridge, was isolated from Cannabis sativa. This is the first example of a C-bridged dimeric cannabinoid. The structure of 1 was unambiguously deduced by HRESIMS, GCMS, and NMR spectroscopy. A plausible biogenesis of 1 is described.