Transesterification of glyceryl tributyrate with methanol using strontium borate as the solid base catalyst

Four kinds of strontium borates were prepared and characterized by XRD, SEM, EDS, TG-DTA and Hammett titration method, and their catalytic activities were examined in the transesterification of glyceryl tributyrate with methanol for the first time. The separate effects of the molar ratio of methanol to oil, the reaction time, and reusability were investigated. In addition, the catalytic activities of Sr(OH)₂ and SrCO₃ were also examined for the comparison. The results showed that the basicity and catalytic activity of these catalysts were decreased as the following order: Sr(OH)₂ > SrB₂O₄·4H₂O > SrB₆O₁₀·5H₂O > SrB₂O₄ > SrB₆O₁₀ > SrCO₃, and the reusability decreases as the following order: anhydrous strontium borates (SrB₂O₄, SrB₆O₁₀) > hydrated strontium borates (SrB₂O₄·4H₂O, SrB₆O₁₀·5H₂O) > Sr(OH)₂. The results indicate that the SrB₂O₄·4H₂O with regular morphology, which was obtained at low temperature by a simple preparation method, might be as one kind of good potential alkaline earth salts catalyst for transesterification. Moreover, the possible reaction mechanism is proposed and analyzed.     

Progress of Jinping Underground laboratory for Nuclear Astrophysics (JUNA)

Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of~(25)Mg(p,γ)~(26)Al,~(19)F(p,α)~(16)O,~(13)C(α,n)~(16)O and ~(12)C(α,γ)~(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.     

Insight into herbicide resistance of W574L mutant Arabidopsis thaliana acetohydroxyacid synthase: molecular dynamics simulations and binding free energy calculations

Acetohydroxyacid synthase (AHAS) is the target enzyme of several classes of herbicides, such as sulfonylureas and imidazolinones. Now many mutant AHASs with herbicide resistance have emerged along with extensive use of herbicides, therefore it is imperative to understand the detailed interaction mechanism and resistance mechanism so as to develop new potent inhibitors for wild-type or resistant AHAS. With the aid of available crystal structures of the Arabidopsis thaliana (At) AHAS-inhibitor complex, molecular dynamics (MD) simulations were used to investigate the interaction and resistance mechanism directly and dynamically at the atomic level. Nanosecond-level MD simulations were performed on six systems consisting of wild-type or W574L mutant AtAHAS in the complex with three sulfonylurea inhibitors, separately, and binding free energy was calculated for each system using the MM-GBSA method. Comprehensive analyses from structural and energetic aspects confirmed the importance of residue W574, and also indicated that W574L mutation might alert the structural charactersistic of the substrate access channel and decrease the binding affinity of inhibitors, which cooperatively weaken the effective channel-blocked effect and finally result in weaker inhibitory effect of inhibitor and corresponding herbicide resistance of W574L mutant. To our knowledge, it is the first report about MD simulations study on the AHAS-related system, which will pave the way to study the interactions between herbicides and wild-type or mutant AHAS dynamically, and decipher the resistance mechanism at the atomic level for better designing new potent anti-resistance herbicides.     

Study of the primordial lithium abundance

Lithium isotopes have attracted an intense interest because the abundance of both 6Li and 6Li from big bang nucleosynthesis (BBN) is one of the puzzles in nuclear astrophysics. Many investigations of both astrophysical observation and nucleosynthesis calculation have been carried out to solve the puzzle, but it is not solved yet. Several nuclear reactions involving lithium have been indirectly measured at China Institute of Atomic Energy, Beijing. The Standard BBN (SBBN) network calculations are then perfo...     

Determination of the ~(12)C(p, γ)~(13)N reaction rates fromthe ~(12)C(~7Li,~6He)~(13)N reaction

The angular distribution of the 12C(7Li,6He)13N reaction at E(7Li) = 44.0 MeV was measured at the HI-13 tandem accelerator of Beijing, China. The asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be (1.64 ± 0.11) fm-1/2 through the distorted wave Born approximation (DWBA) analysis. The ANC was then used to deduce the astrophysical S (E) factors and reaction rates for the 12C(p,γ)13N direct capture reaction at energies of astrophysical relevance.     

Nuclear uncertainties in the s-process simulation

The heavy elements in the Universe are formed during the s- and r-processes mainly in AGB stars and supernovae, respectively. Simulation of s- and r-nucleosynthesis critically depends on the neutron capture and weak decay rates for all the nuclei on the reaction chain. The present work analyzes systematically the neutron capture rates (cross sections) for the s-process nuclei, including ～3000 rates on ～200 nuclei. The network calculations for the constant temperature s-process have been performed using the different data sets selected as the nuclear inputs to investigate the uncertainties in the predicted s-abundances. We show that the available cross sections of neutron capture on many s-process nuclei still carry large uncertainties, which lead to low accuracy in the determination of s-process isotope abundances. We analyze the neutron capture cross section data for the same unique isobar nucleus accorded by year from previous work. Such an analysis indicates that the s-process has been studied for more than fifty years and there exist two research stages around 1976 and 2002, respectively. The needs and opportunities for future experiments and theoretical tools are highlighted to remove the existing shortcomings in the neutron capture rates.     

Formation of super-concentrated hydrochloric acid in the third phase in tertiary amine N235-PtCl 6 2− -HCl system and its influences on the Pt microemulsion extraction

In this paper, we have investigated the formation of the third-phase in tertiary amine (N235)-PtCl ₆ ^2? -HCl system and the microscopic phase structural evolution of platinum-loaded organic phases before and after the occurrence of the third-phase. The third-phase is characterized by various spectroscopic techniques, and the small angle X-ray scattering (SAXS) experiments demonstrate the appearance of nano-aggregates, i.e., water-in-oil reversed micelles, in the third phase. The experimental results indicate that (1) formation of the third phase is related to the aggregation behaviors of nano-reversed micelles in which a super-concentrated hydrochloric acid formed with the H⁺ to H₂O molar ratio being much higher than that of the conventional 37 wt% saturated hydrochloric acid. (2) The occurrence of the super-concentrated HCl results in a great amount of H⁺ and Cl^? ions enriched and confined within the nano-water pools of W/O reversed micelles in third phase. Therefore, the coordination behaviors of platinum complex ions in that super-concentrated hydrochloric acid are very different from their corresponding behaviors in bulk aqueous solutions. It is possible that H⁺ ions participate in the formation of such complexes as H _m PtCl ₆ ^z+ in the super-concentrated hydrochloric acid. (3) The relative contents of various H _m PtCl ₆ ^z+ complexes are different corresponding to the H⁺ ion concentrations in confined nano-water pools. The association ability of the acidified tertiary amine N235 molecules (R₃NH⁺) with various H _m PtCl ₆ ^z+ complexes plays an important role in affecting the platinum extraction behaviors.     

Core-shell fibrous vascular grafts with the nitric oxide releasing property

Small-diameter vascular grafts with the nitric oxide(NO) releasing property were designed and prepared.Diazeniumdiolated N,N'-dibutyl-1,6-hexanediamine(DBHD/N2O2) was first synthesized as the NO donor and doped into the biocompatible polymer poly(ε-caprolactone)(PCL).The fibrous vascular grafts were fabricated by electrospinning.Despite the reduced platelet adhesion observed on the NO releasing grafts,the cytotoxicity and burst release were apparent,especially at a higher loading level of the NO donor.In or...     

Can the decay rate of ~(32)P be changed by mechanic motion?

The influence of mechanic motion on the decay rate of 32P was studied by means of liquid scintillation counting (LSC). The results indicate that, on the Northern Hemisphere, the half life of 32P in anticlockwise circular centrifuge rotation (radius 10 cm, 4000 r/min) equals the one in natural conditions within 0.6 percent uncertainty.     

BRIF and CARIF progress

China Institute of Atomic Energy (CIAE) is currently constructing Beijing rare ion beam facility (BRIF) and is proposing China advanced rare ion beam facility (CARIF). This paper is aiming at introducing the progress of BRIF project and the conceptual design CARIF. The ISOL type facility BRIF under construction is composed of a 100 MeV 300 μA proton cyclotron, an ISOL with mass resolution of 20000, and a super-conducting LINAC of 2 MeV/q, and will be commissioned in 2013. CARIF facility proposed is planned to use both ISOL and PF techniques. It is based on a China advanced research reactor CARR that was critical, with ISOL separation of fission fragment, post acceleration to 150 MeV/u, and fragmentation of neutron-rich fission fragment beam like ¹³²Sn. Such unique combination will allow CARIF to deliver beam intensity better than the best world facilities by more than one order of magnitude.