南极假丝酵母在纳米聚苯乙烯上的共价固载及其在微波辅助酯化反应中的应用（英文）

Nanopolystyrene was used as a solid support for the covalent immobilization of Candida antarctica lipase B(Cal B) using the photoreactive reagent 1‐fluoro‐2‐nitro‐4‐azido benzene(FNAB) as a cou‐pling reagent. The obtained derivative was then used as a biocatalyst in a microwave assisted ester‐ification experiment. Factors such as contact time, pH, and enzyme concentration were investigated during immobilization. The hydrolytic activity, thermal, and operational stability of immobi‐lized‐Cal B were determined. The maximum immobilized yield(218 μg/mg support) obtained at pH 6.8 exhibited optimum hydrolytic activity(4.42 × 103 mU p‐nitrophenol/min). The thermal stability of Cal B improved significantly when it was immobilized at pH 10, however, the immobilized yield was very low(93.6 μg/mg support). The immobilized‐Cal B prepared at pH 6.8 and pH 10 retained 50% of its initial activity after incubation periods of 14 and 16 h, respectively, at 60 °C. The opera‐tional stability was investigated for the microwave assisted esterification of oleic acid with metha‐nol. Immobilized‐Cal B retained 50% of its initial activity after 15 batch cycles in the micro‐wave‐assisted esterification. The esterification time was notably reduced under microwave irradia‐tion. The combined use of a biocatalyst and microwave heating is thus an alternative total green synthesis process.     

Dispersion of polymeric-coated–silica aerogel particles in unsaturated polyester composites: Effects on thermal-mechanical properties

The thermal-mechanical properties of unsaturated polyester (UP) composite were enhanced by the dispersion of silica aerogel (SA) with preserved pores. Low-cost SA was prepared from rice husk via the sol-gel process and ambient pressure drying. A new method was proposed to encapsulate the hydrophobic aerogel surface pores with hydrophilic polyvinyl alcohol (PVA) film using the fluidized-bed coating process. The dispersion of PVA-coated aerogel with preserved pores in the polyester matrix resulted in an increase of specific compressive strength (44.1?MPa?·?cm³?g^?1), thermal insulation (0.23?W?m^?1?K^?1), and thermal stability (T_onset?=?310°C), but decreased the glass transition temperature (T_g?=?260°C).     

γ-Hydroxypropyl-functionalised iron thiolate complexes: crystal and molecular structure of [{Fe2(CO)6(μ-SCH2CH2CH2OH)}2(μ4-S)]

The γ-hydroxypropyl-functionalised diiron dithiolate complex [Fe₂(CO)₆(μ-SCH₂CH₂CH₂OH)₂] is prepared upon thermolysis of Fe₃(CO)₁₂ and HO(CH₂)₃SH and further reaction with dppm (dppm = Ph₂PCH₂PPh₂) affords [Fe₂(CO)₄(μ-dppm)(μ-SCH₂CH₂CH₂OH)₂]. From the reaction of Fe₃(CO)₁₂ with dppm(S₂) a minor product is the tetrairon cluster, [{Fe₂(CO)₆(μ-SCH₂CH₂CH₂OH)}₂(μ⁴-S)], the mode of formation of which is unclear. It has been crystallographically characterised and adopts a μ⁴-S bridged double butterfly structure which is compared with other crystallographically characterised complexes of this type. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Numerical solutions of the Gardner equation by extended form of the cubic B-splines

The extended definition of the polynomial B-splines may give a chance to improve the results obtained by the classical cubic polynomial B-splines. The optimum value of the extension parameter can be determined by scanning some intervals containing zero. This study aims to solve some initial boundary value problems constructed for the Gardner equation by the extended cubic B-spline collocation method. The test problems are derived from some analytical studies to validate the efficiency and accuracy of the suggested method. The conservation laws are also determined to observe whether the test problems remain constant as expected from the theoretical aspect. The stability of the proposed method is investigated by the von Neumann analysis.     

Noncommutative Wormholes in f(R) Gravity with Lorentzian Distribution

In this paper, we derive some new exact solutions of static wormholes in f(R) gravity supported by the matter possesses Lorentzian density distribution of a particle-like gravitational source. We derive the wormhole’s solutions in two possible schemes for a given Lorentzian distribution: assuming an astrophysically viable F(R) function such as a power-law form and discuss several solutions corresponding to different values of the exponent (here $F =\frac{df}{dR}$ ). In the second scheme, we consider particular form of two shape functions and have reconstructed f(R) in both cases. We have discussed all the solutions with graphical point of view.     

Characterization of AZ91D Granules Covered with a Flux during In‐Situ Melting

Oxidation and melting behaviors of AZ91D granules throughout the in‐situ melting process using flux were investigated. The granules were heated under unprotected environment at four different temperatures between 650 and 800 °C, for the durations of 30 and 60 min. The products of heating process were characterized macroscopically and the oxides formed on the granules were examined using field emission scanning electron microscope, energy dispersive X‐ray spectroscopy and X‐ray diffraction analysis. Thermal analysis was used to reveal the response of the granules to heating during the in‐situ melting. The results showed that the granules experienced severe oxidation even in the presence of the flux, and significant amount of them changed to a powdered state due to oxidation and combustion, especially at 800 °C. It was discovered that the granules melted during heating; however, oxides formed on their surface encapsulated the molten metal and prevented the liquids from merging. The results also revealed that increasing heating temperature and time enhanced mold‐magnesium reaction resulted in the entrance of mold materials into the oxidation residues.     

Synthesis of α,β-unsaturated butenolides from allenic acids

The electrophile-initiated cyclisation of allenic acids and esters provides a general route for the synthesis of β-substituted α,β-unsaturated butenolides.     

Regioselective and reversible carbon-nitrogen bond formation: synthesis, structure and reactivity of ureato-bridged complexes [Mo2(NAr)2(mu-X){mu-ArNC(O)NAr}(S2CNR2)2](Ar = Ph, p-tol; X = S, NAr; R = Me, Et, Pr)

Reaction of ArNCO with syn-[MoO(mu-O)(S2CNR2)]2 or syn-[MoO(mu-NAr)(S2CNR2)]2 at 110 degrees C leads to the facile formation of bridging ureato complexes [Mo2(NAr)2(mu-NAr){mu-ArNC(O)NAr}(S2CNR2)2](Ar = Ph, p-tol; R = Me, Et, Pr), formed upon substitution of all oxo ligands and addition of a further equivalent of isocyanate across one of the bridging imido ligands. Related sulfido-bridged complexes [Mo2(NAr)2(mu-S){mu-ArNC(O)NAr}(S2CNR2)2] have been prepared from syn-[Mo2O2(mu-O)(mu-S)(S2CNR2)2]. When reactions with syn-[MoO(mu-NAr)(S2CNEt2)]2 were followed by NMR, intermediates were observed, being formulated as [Mo2O(NAr)(mu-NAr){mu-ArNC(O)NAr}(S2CNEt2)2], which at higher temperatures convert to the fully substituted products. A crystallographic study of [Mo2(N-p-tol)2(mu-S){mu-p-tolNC(O)N-p-tol}(S2CNPr2)2] reveals that the bridging ureato ligand is bound asymmetrically to the dimolybdenum centre-molybdenum-nitrogen bonds trans to the terminal imido ligands being significantly elongated with respect to those cis-a result of the trans-influence of the terminal imido ligands. This trans-influence also leads to a trans-effect, whereby the exchange of aryl isocyanates can occur in a regioselective manner. This is followed by NMR studies and confirmed by a crystallographic study of [Mo2(N-p-tol)2(mu-N-p-tol){mu-p-tolNC(O)NPh}(S2CNEt2)2]--the PhNCO occupying the site trans to the terminal imido ligands. Ureato complexes also react with PhNCS, initially forming [Mo2(NAr)2(mu-S){mu-ArNC(O)NAr}(S2CNR2)2], resulting from exchange of the bridging imido ligand for sulfur, together with small amounts of [Mo2(NAr)2(mu-S)(mu-S2)(S2CNEt2)2], containing bridging sulfide and disulfide ligands. The ureato complexes [Mo2(NAr)2(mu-S){mu-ArNC(O)NAr}(S2CNR2)2] react further with PhNCS to give [Mo2(NAr)2(mu-S)2(S2CNR2)2]n (n = 1, 2), which exist in a dimer-tetramer equilibrium. In order to confirm these results crystallographic studies have been carried out on [Mo2(N-p-tol)2(mu-S)(mu-S2)(S2CNEt2)2] and [Mo2(N-p-tol)2(mu-S)2(S2CNPr2)2]2.     

Molybdenum(VI) imido complexes: formation of [Mo(NPh)(S2CNR2)3]X and [Mo(NPh)(S2CNR2)2(μ-MoO4)]2 (R?=?Me, Et) from the reaction of [MoO2(S2CNR2)2] and PhNCO under aerobic conditions

Abstract  

Products from the thermolysis of PhNCO and [MoO₂(S₂CNR₂)₂] (R = Me, Et) are highly dependent upon the reaction conditions. When carried out in air, the major products are cations, [Mo(NPh)(S₂CNR₂)₃]⁺, as shown by a crystal structure of [Mo(NPh)(S₂CNEt₂)₃]₂[Mo₆O₁₉]. Under rigorously anaerobic conditions, reaction of two equivalents of PhNCO with [MoO₂(S₂CNR₂)₂] affords [Mo(NPh)₂(S₂CNR₂)₂] as the major product. However, chloroform solutions of the bis(imido) complexes hydrolyze in air to afford [Mo(NPh)(S₂CNR₂)₂(μ-MoO₄)]₂, in which molybdate groups bridge between molybdenum(VI) imido-bis(dithiocarbamate) centers. These results are placed in context of our earlier studies of these reactions that lead to the formation of oxo-disulfide [MoS₂(NPh)(S₂CNR₂)₂] and dimeric molybdenum(V) [MoO(μ-NPh)(S₂CNR₂)]₂ complexes, thus allowing a full picture of these transformations to be established.