Effects of cobalt-60 γ-ray irradiation on fresh-keeping and storage of kiwifruits

The boxes contained kiwifruits were irradiated with cobalt-60 γ-rays at different dosages (0.6 , 1.8 and 3.6 KGy) and stored in a room ventilated at night, the natural ambient air being used as cool source.The results showed that the treatment which fruits irradiated with 0.6 KGy was the best after 85 days. It gave the normal-fruit rate of 95.10%, fruit flesh hardness of 4.10 Kg · cm^-2, fresh and plump fruits, good quality and less Vc loss.     

四元缔合物体系薄层树脂相分离与光度法联用测定痕量钴

提出了在酸性条件下 (pH=5.0),利用阳离子交换树脂-丁二酮肟-碘-钴四元体系,通过薄层树脂相光度法测定钴的新方法。本法灵敏度高 (e454=1.7105L/molcm),比水相光度法提高14倍,精密度理想 (测定2.0礸/ml Co(II) 6次,RSD=1.3%),选择性好。实测药品VB12及天然水中钴,线性范围0.024~2.0礸/ml (定容50ml),检出限10.4ng/ml。     

原油溶胶-凝胶等温转变过程中的流变性研究

使用RS75流变仪，采用小振幅振荡剪切方法和稳态剪切方法对含蜡原油在溶胶 -凝胶等温转变过程中的流行了研究．结果表明，等温转变成的凝胶原油的结构在 很大程度上决定于预剪切速率，非牛顿含蜡原油在结构恢复过程中表现出不可逆的 触变特性．而凝胶原油在外力作用下向溶胶状态转变的过程中，要经历从线性粘弹 性变形，到非线性粘弹性变形，再到结构屈服的过程，且高剪切应力下的溶胶原油 结构与预剪切速率无关．     

An efficient procedure for the synthesis of coumarin derivatives using TiCl4 as catalyst under solvent-free conditions

The ability of titanium(IV) chloride as a catalyst to promote the Pechmann condensation reaction with a range of phenols and β-keto esters is described.The reaction was carried out by addition of TiCl₄ to a mixture of the phenol and the β-keto ester with thorough stirring in the absence of a solvent and represents an improvement on the classical Pechmann conditions. The yields of coumarins obtained via this novel protocol were significantly higher than those using the conventional method and the reaction duration was reduced to a few minutes or even a few seconds.     

Frequent analytical/experimental problems in lipase-mediated synthesis in solvent-free systems and how to avoid them

Compared with chemical catalysis, enzymatic catalysis is a relatively new topic. Experimental work involving lipases deserves careful attention and accurate procedures still need to be implemented. A rapid but careful survey of published data immediately demonstrates that experiments performed under similar conditions with similar reagents have led to very different results. The aim of this work is to point out the importance of accurate and systematic procedures in order to ensure the reproducibility of experimental data. We strongly believe that different results found by different labs are due to problems detected in the procedures used. Quantification of the immobilisation efficiency of lipase on several supports through UV/visible methods and sampling methods used to obtain correct enzymatic activity values are specifically analysed. After a brief review which demonstrates the big discrepancies found in the literature, original data from Candida rugosa lipase adsorption on polypropylene powder and its use in the solvent-free synthesis of ethyl oleate are introduced in order to exemplify the difficulties found in these kinds of systems. Several procedures described in the literature are assayed and the accuracy of the results obtained is carefully analysed. The aim of the whole analysis performed is that it would be useful for any powdered solid to be used as a support for a lipase in a solvent-free system for any synthesis reaction, especially for those involving a volatile reagent. Throughout this contribution, special emphasis is placed on how catalytic reaction results using enzymes (free and immobilised) are reported so as to allow comparison between published data, something which is usually difficult since very different units are used and often complementary data are not included.     

Ferroelectric phase transitions in Pb2xSn2(1-x)P2Se6 system

Heat capacities of the Pb_2xSn_2(1-x)P₂Se₆ crystals (x=0, 0.098, 0.251, 0.402 and 1.0) were measured using an adiabatic calorimeter at temperatures between 10 and 350 K. In the crystal of x=0, two heat capacity anomalies corresponding to the ferroelectric commensurate - intermediate incommensurate(C-IC) phase transition temperature T _i, and the incommensurate - paraelectric (IC-N) phase transition temperature T _c, were observed at 193.24±0.10 and 220.07±0.15 K, respectively. The phase transition temperatures decreased with an increase in Pb²⁺ concentration. The anomaly at Ti disappeared at x=0.251 in the mixed systems of the Pb_2xSn_2(1-x)P₂Se₆. In the crystal of Pb₂P₂Se₆ (x=1.0), no phase transition was observed. The normal heat capacities for the mixed crystals were determined by least squares fitting of the Debye and Einstein functions to the experimental data. The anomalous heat capacities gave the phase transition entropies of 8.5 and 1.5 J mol^-1 K^-1 for x=0. The large transition entropies are consistent with an order-disorder mechanism in the ferroelectric-paraelectric phase transitions in x=0. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diagramme de phases du systeme binaire LiNO3-NaNO3

Phase diagram of the binary system LiNO₃-NaNO₃ has been obtained by using direct and differential thermal analysis between 323 and 623 K. This system is characterized by an eutectic plateau at 467 K. The eutectic point is at 0.465 mole NaNO₃. A peritectic appears at 550 K. There is no miscibility in the solid state. These findings associated with some other thermodynamic results have been used to calculate the activities of the constituents along the liquids curve and the excess thermodynamic functions at 618 K. The constituents seem not to have a symmetrical influence on the thermodynamic quantities.

     

Synthesis of a new donor, BEDT-HBDST and crystal structures, electrical and magnetic properties of (BEDT-HBDST)2MX4 (M=Fe, Ga, X=Cl, Br), where BEDT-HBDST=2,5-bis(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-2,3,4,5-tetrahydrothiophene

A novel conjugation-elongated bis(ethylenedithio)tetraselenafulvalene (BETS) type donor, 2,5-bis(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-2,3,4,5-tetrahydrothiophene (BEDT-HBDST) and its magnetic and non-magnetic anion salts, (BEDT-HBDST)₂MX₄ (MX₄⁻=FeCl₄⁻, GaCl₄⁻, FeBr₄⁻ and GaBr₄⁻), were prepared. These four salts are isostructural and belong to the space group of P2/c. They showed semiconducting behavior with small activation energies (59-64 meV). The band structures of these salts are quasi one-dimensional and there is a midgap between the upper band and the lower band, since the degree of dimerization is significant in the stacking direction. The MX₄⁻ ions are located between the donor columns and near to the ethylenedithio moieties of the donor molecules. The magnetic susceptibilities of the FeCl₄⁻ and FeBr₄⁻ salts follow the Curie-Weiss law with Curie constants of 4.6 and 4.8 emu K mol⁻¹ (sum of the spins of S=5/2 and S=1/2) and negative Weiss temperatures of θ=−1.2 and −4.9 K, respectively, revealing a weak antiferromagnetic interaction of 3d spins of the FeCl₄⁻ and FeBr₄⁻ anions. The Fe?Fe (6.66-7.60 Å), Cl?Cl (4.81-4.82 Å) and Br?Br (4.74-4.77 Å) distances in the crystal structures of these salts are significantly long. Therefore, the direct magnetic interaction between the 3d spins of the nearest neighboring Fe³⁺ ions appears to be not readily accessible.     

Preparation and mechanical properties of thermal energy storage microcapsules

A series of heat energy storage microcapsules was prepared using melamine-formaldehyde resin as the shell material and the mechanical properties of the shell were investigated. A phase change material whose melting point was 24 °C was used as core and the quantity of heat involved in phase transition was 225.5 J/g. Average diameter of the microcapsules varied from 5 to 10 μm, and the globular surface was smooth and compact. The mechanical properties of the shell were evaluated by observing the surface morphological structure change after application of pressure by means of scanning electron microscopy. When the mass ratio of the core and shell material is 3:1, a yield point of about 1.1×10⁵ Pa was found and when the compression was increased beyond this point the microcapsules showed plastic behavior. This has been attributed to the cross-link density and to the high degree of reaction of the shell material. Different yield points subsequently reflected differences in the mechanical behavior. It was also found that the mechanical intensity of double-shell microcapsules was better than that of single shelled ones.     

集成滤波器在谱图信号除噪中的应用

本文提出了一种由神经元网络与线性自适应滤波器组成的集成滤波器的实现方法，用于谱图信号除噪处理。