Strange baryon resonance production in sqrt s NN=200 GeV p+p and Au+Au collisions

We report the measurements of Sigma(1385) and Lambda(1520) production in p+p and Au+Au collisions at sqrt[s{NN}]=200 GeV from the STAR Collaboration. The yields and the p(T) spectra are presented and discussed in terms of chemical and thermal freeze-out conditions and compared to model predictions. Thermal and microscopic models do not adequately describe the yields of all the resonances produced in central Au+Au collisions. Our results indicate that there may be a time span between chemical and thermal freeze-out during which elastic hadronic interactions occur.     

Determination of ultratrace boron concentrations in uranium oxide by isotope dilution-thermal ionization mass spectrometry using a simplified separation procedure

Boron was determined at sub-ppm levels in uranium oxide by ID-TIMS. Following nitric acid dissolution, a solvent extraction method was adapted for extraction of boron by 5% 2-ethylhexane-1,3-diol in chloroform followed by evaporation of the extractant in presence of sodium carbonate and mannitol. This procedure allowed TIMS analysis of boron by monitoring the Na₂BO ₂ ⁺ ions formed from the sodium borate salt in the ion source. Reproducibility of about 1% was obtained for boron determination in the three different uranium oxide samples containing sub-ppm amounts of boron.     

2D Porphyrinic Metal-Organic Frameworks Featuring Rod-Shaped Secondary Building Units

Metal-organic frameworks (MOFs) encompass a rapidly expanding class of materials with diverse potential applications including gas storage, molecular separation, sensing and catalysis. So-called ‘rod MOFs’, which comprise infinitely extended 1D secondary building units (SBUs), represent an underexplored subclass of MOF. Further, porphyrins are considered privileged ligands for MOF synthesis due to their tunable redox and photophysical properties. In this study, the Cu^II complex of 5,15-bis(4-carboxyphenyl)-10,20-diphenylporphyrin (H₂L-Cu^II, where H₂ refers to the ligand’s carboxyl H atoms) is used to prepare two new 2D porphyrinic rod MOFs PROD-1 and PROD-2. Single-crystal X-ray analysis reveals that these frameworks feature 1D Mn^II- or Co^II-based rod-like SBUs that are coordinated by labile solvent molecules and photoactive porphyrin moieties. Both materials were characterised using infrared (IR) spectroscopy, powder X-ray diffraction (PXRD) spectroscopy and thermogravimetric analysis (TGA). The structural attributes of PROD-1 and PROD-2 render them promising materials for future photocatalytic investigations.     

Correlation between pK(a) and reactivity of quinuclidine-based catalysts in the Baylis-Hillman reaction: discovery of quinuclidine as optimum catalyst leading to substantial enhancement of scope

The reactivity of a variety of quinuclidine-based catalysts in the Baylis-Hillman reaction has been examined, and a straightforward correlation between the basicity of the base and reactivity has been established, without exception. The following order of reactivity was established with pK(a)'s of the conjugate acids (measured in water) given in parentheses: quinuclidine (11.3), 3-hydroxyquinuclidine (9.9), DABCO (8.7), 3-acetoxyquinuclidine (9.3), 3-chloroquinuclidine (8.9), and quinuclidinone (7.2). The higher than expected reactivity of DABCO, based on its pK(a), was analyzed by comparing the relative basicity of DABCO and 3-acetoxyquinuclidine in DMSO. It was found that in aprotic solvent, DABCO was 0.6 pK(a) units more basic than 3-acetoxyquinuclidine, thus establishing a direct link between pK(a) of the amine and its reactivity. In contrast to previous literature work that reported the contrary, quinuclidine, which has the highest pK(a), was found to be the most active catalyst. The reaction profile with quinuclidine showed significant autocatalysis, which suggested that the presence of proton donors might further enhance rates. Thus, a series of additives bearing polar X-H bonds were investigated and it was found that methanol, triethanolamine, formamide, and water all provided additional acceleration. Methanol was found to be optimum, and the powerful combination of quinuclidine with methanol was tested with a host of aldehydes and Michael acceptors. Not only were the reactions more efficient and faster than previously reported, but now new substrates that were previously unreactive could be employed. Notable examples include the use of acetylenic aldehydes and the employment of vinyl sulfones, acrylamides, delta-lactones, and even alpha,beta-unsaturated esters bearing a beta-substituent.     

A catalytic antibody programmed for torsional activation of amide bond hydrolysis

Amidase antibody 312d6, obtained against the sulfonamide hapten 4 a that mimics the transition state for hydrolysis of a distorted amide, accelerates the hydrolysis of the corresponding amides 1 a-3 a by a factor of 10(3) at pH 8. The mechanisms of both the uncatalyzed and antibody-catalyzed reactions were studied. Between pH 8 and 12 the uncatalyzed hydrolysis of N-toluoylindoles 1 a and 3 a shows a simple first-order dependence on [OH(-)], while hydrolysis of 3 a is zeroth-order in [OH(-)] below pH 8. The pH profile for hydrolysis of the corresponding tryptophan amide 2 a is more complex due to the dissociation of the zwitterion into an anion with pK(a) 9.74; hydrolysis of the zwitterionic and the anionic form of 2 a both show simple first-order dependence on [OH(-)]. Absence of (18)O exchange between H(2) (18)O/(18)OH(-) and the substrate, a normal SKIE for both 1 a (k(H)/k(D)=1.12) and 3 a (k(H)/k(D)=1.24) and the value of the Hammett constant rho for hydrolysis of p-substituted amides 3 a-e are consistent with an ester-like mechanism in which formation of the tetrahedral intermediate is rate-determining and the amine departs as anion. The 312d6-catalyzed hydrolysis of 3 a was studied between pH 7.5 and 9, and its independence of pH in this range indicates that water is the reacting nucleophile. Hydrolysis of 3 a is only partially inhibited by the sulfonamide hapten, and this indicates that non-specific catalysis by the protein accompanies the specific process. Only the nonspecific process is observed in the hydrolysis of amides 3 with para substituents other than methyl. Binding studies on the corresponding series of p-substituted sulfonamides 5 a-e confirm the high specificity of antibody 312d6 for p-methyl substituted substrates.     

A simple, user-friendly process for the homologation of aldehydes using tosylhydrazone salts

Aldehydes can be homologated to ketones in moderate to good yields using aryldiazomethanes generated in situ from tosylhydrazones. Chiral aldehydes can be employed with almost complete retention of configuration. The tosylhydrazones can also be generated in situ from the corresponding aldehyde leading to a one-pot process for coupling two different carbonyl compounds to give ketones.     

Differential scanning calorimetry study of Ge1−xSnxSe2.5 glasses

The glass-forming tendency and specific heat in ice cold water-quenched Ge_1?xSn_xSe_2.5 glassy alloys with 0H _f, the heat ΔH _c associated with the crystallization of an amorphous phase and the glass transition temperatureT _g were deduced from the DSC curves. The composition dependence of glass forming ability,T _g and crystallization behavior has been discussed.     

Removal of fission products from mixed solvents using zeolites

The solvents tributylphosphate (TBP) and odourless kerosene (OK) are widely used to extract plutonium(IV) and uranium(V) in nuclear processing plants. Although these solvents are chosen because of their low affinity for fission products it is, nevertheless, of value to study ways of removing the small quantities of fission products, such as isotopes of Cs, Sr and Ru, which can be present in the solvents. This paper describes simple distribution coefficients (K _d) measurements made to test the ability of the aluminosilicate zeolites to remove¹⁰⁶Ru from TBP, OK, and their mixtures.     

Synthesis of mesoporous γ-alumina by sol–gel process and its characterization and application for sorption of Pu(IV)

Mesoporous γ-alumina samples were prepared by the sol–gel process from the boehmite sol having different template solutions. Copper doped material was also prepared from sol containing template solution along with copper nitrate. Studies were performed to understand the influence of templates on the morphology of the synthesized samples particularly with respect to specific surface area and porosity. Synthesized samples were used to study sorption of Pu(IV) from nitric acid–oxalic acid solutions. Distribution ratios (D) for Pu(IV) were determined using the γ-alumina samples with an objective to employ these for the recovery of Pu.     

Structural studies of nickel(II) complexes with 1-<Emphasis Type="Italic">tert</Emphasis>-butylimidazole-2-thione and 3-phenyl-5-methyl-pyrazole ligands

The nickel(II) complexes dichlorobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂Cl₂] (1), dinitratobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂(NO₃)₂] (2), dichloro-bis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)Cl₂] (3) and dinitratobis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)(NO₃)₂] (4) have been synthesized and studied. The single crystal X-ray diffraction analysis was carried out for 1 and 4 {Bruker Kappa Apex-II CCD diffractometer, MoK _α radiation}. Crystal data for 1: monoclinic C2/c, a = 16.949(2) Å, b = 8.6647(10) Å, c = 15.461(3) Å, β = 117.662(4)°, V = 2011.1(5) ų, Z = 4, D _calc = 1.460 g/cm³. Crystal data for 4: triclinic P-1, a = 9.9775(7) Å, b = 11.2254(8) Å, c = 14.8068(10) Å, α = 75.401(4)°, β = 87.422(4)°, γ = 74.874(4)°, V = 1548.86(19) ų, Z = 2, D _calc = 1.405 g/cm³. Coordination core of complex 1 adopts distorted tetrahedral geometry whereas core 4 has distorted octahedral geometry. The bonded nitrates are of two types coordinating as monodentate and bidentate ligands.