A METHOD OF PREPARING SPHERICAL NANO-CRYSTAL CELLULOSE WITH MIXED CRYSTALLINE FORMS OF CELLULOSE Ⅰ AND Ⅱ

A new kind of nano-crysta cellulose (NCC) prepared from natural cotton fiber has been obtained by the method ofacid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our products are preparedfrom natural cotton fibers. The products are of spherical shape with mixed crystal forms of cellulose I and II. The preparationconditions determine the properties of the products. Prior treatment is a critical procedure. The properties of the products arealso strongly affected by such conditions as the kinds of acids used, the ratio of the acid mixture, the acid concentration, theultrasonic agitation time and hydrolysis temperature. The number average molecular weight of NCC is determined by gelpermeation chromatography (GPC). The particle size and shape were determined by transmission electron microscopy(TEM). X-ray diffraction was used to detect the crystallinity and average crystallite size of the panicle.     

The application of microchemical methods to radiochemical analysis : Part III. Solvent extraction of diethyldithiocarbamates and the radiochemical separation and purification of cobalt,nickel, palladium,silver and cadmium

The advantages of solvent extraction of diethyldithiocarbamatcs in radiochcmical separations are discussed. The development of a procedure for the separation and purification of cobalt and nickel from mixtures containing fission products is described; diethyldithiocarbamate extraction is used extensively. A scheme incorporating this procedure is also described whereby the fission products palladium, cadmium and silver are also determined on the same sample.     

Radiolysis of 2-acetylfuran in 2-propanol in absence of atmospheric oxygen

Gamma radiolysis of 2-acetylfuran (AF) in 2-propanol, in absence of atmospheric oxygen, has been investigated. The radiation yields of hydrogen, methane at different doses as well as radiolytic products in solution were determined. The radiolytic products were determined by gas chromatography coupled with mass spectrometry. The mechanisms for formation of detected radiolytic products and the effect of (AF) concentration on hydrogen and methane yields are discussed.     

Oxidation of sulphide minerals-III determination of sulphate and thiosulphate in oxidised sulphide minerals

A method has been developed to determine sulphate and thiosulphate in small amounts of the oxidation products of sulphide minerals. The sample is treated with ammonium sulphide solution to promote ion-exchange between sulphide ion and the sulphur-bearing anions of the oxidation products. Sulphate is determined alone and then all other sulphoxy anions are oxidized to sulphate and determined as such. The non-sulphate anions are reported as thiosulphate. The relative error is about 10% or less for 2 mg or more of sulphoxy anion. Although this method does not yield exact results with respect to sulphite or polythionates, a clearer understanding of the oxidation of sulphide minerals is now available.     

Cycloaddition isomerizations of adsorbed 1,3-cyclohexadiene on Si(100)-2x1 surface: first neighbor interactions

The initial and subsequent surface reaction mechanisms of 1,3-cyclohexadiene on the Si(100)-2x1 surface were theoretically explored, focusing on the possible first-neighbor interactions. Five different initial reaction channels leading to nine different surface products were identified, confirming previous experimental reports of inter-dimer structures. Among the nine identified products, five of these surface products are new species that have not previously been reported. Potential energy surface studies reveal that the net reaction barriers within a given channel are very small, indicating that the final product distributions within that channel are determined by thermodynamics. On the other hand, thermal isomerizations between different channels are not expected to occur easily. Therefore, the surface product distributions among the five different channels are more likely to be determined by kinetics. As a result, understanding the relationships among the available reaction channels both kinetically and thermodynamically is essential for properly interpreting the experimental results. The current study shows that the subsequent surface chemical reactions of unsaturated initial surface products are strongly coupled with the first-neighbor interactions.     

Gaussian expansions of orbital products for the evaluation of two-electron integrals

A method is described for evaluating multicenter integrals over contracted gaussian-type orbitals by the use of gaussian expansion of orbital products. The expansions are determined by the method of non-linear least squares with constraints. There is no restriction upon the symmetry of the orbital product and the method is applicable to all products arising from s, p and d-type orbitals. Results are given to indicate the accuracy of the method.     

Supersonic jet spectrometry of thermally decomposed products from polystyrene and polyalpha-methylstyrene

Polystyrene and polyalpha-methylstyrene are thermally decomposed, and the products are measured by fluorescence spectrometry and multiphoton ionization spectrometry. The monomers are found to be major products from both the polymers, but many other chemical species, including dimers and trimers, are also observed. The present instrument is applied to a mixture sample containing these two polymers, and the components included are selectively determined using this hyphenated technique.     

Halobenzenes and Ir(I): kinetic C-H oxidative addition and thermodynamic C-Hal oxidative addition

A (PNP)Ir fragment undergoes facile, room-temperature oxidative addition of C-H bonds in arenes and haloarenes in preference to aromatic carbon-halogen bonds. This preference, however, is determined to be kinetic in nature. Oxidative addition of C-Cl and C-Br is preferred thermodynamically. The products of the C-Cl or C-Br oxidative addition are separated from the C-H oxidative addition products by a high activation barrier and are only accessible at >100 degrees C. Of the C-H oxidative addition products of chlorobenzene, the isomer with the o-ClC6H4 ligand has the lowest energy.     

Influence of macroscopic factors on the composition of the products of cohydrolysis of triorganochlorosilanes

The composition of the products of heterogeneous cohydrolysis of trimethyl- and dimethylphenylchlorosilanes by excess aqueous ammonia (4–5% solution) is determined by the regime of heterofunctional condensation of the initial chlorosilanes with the products of their hydrolysis, triorganosilanols. In a diffusion regime, hexaorganodisiloxanes are formed because of the limited possibility of removing silanols from the reaction zone, while silanols are predominantly formed in a kinetic regime. The influence of the nature of the solvent and surfactant and the intensity of stirring of the reaction mixture on the composition of the final products of hydrolytic cocondensation of triorganochlorosilanes is considered.     

Synthesis and characterization of biodiesel fuel based of esters of tall oil fatty acids

Synthesis of esters from tall oil fatty acids and lower aliphatic alcohols is studied, and characteristics of the products as substitutes or components of diesel fuel are determined.     

Thermal decomposition products of polyethylene

Decomposition products of polymers have been determined by many investigators, but the results are often conflicting because of difficulties in analyzing a large number of products. A comprehensive analysis of the volatile thermal decomposition products of high-density polyethylene has been made with the latest techniques in gas chromatography. The formation of products is explained on the basis of free-radical mechanism. The predominant process in the formation of volatiles appears to be intramolecular transfer of radicals, in which isomerization by a coiling mechanism plays an important role in determining the relative quantities of each product.     

A study on radiation sterilization of medical devices in the South of China

In this paper, directing at the peculiarity of south China, the technique and quality control of Co-80 r radiation sterilization of medical devices have been studied. Radiation dose setting is determined by the AAMI method. Experiment shows that radiation treatment has no effect upon the attributes of the products. Under the same condition of packing and environment, storing time of radiation sterilization is 4 times than that of sterilization by heat. Clinical appliances of 1000 carton products show that radiation sterilization products are safe and reliable.     

Electrocatalytic Hydration of Phenylpropargyl Alcohol

Selective reduction of phenylpropargyl alcohol to cinnamic and hydrocinnamic alcohols is studied in an electrocatalytic system with an activated cathode. Catalysts are selected and optimum conditions for obtaining the target products are determined.     

Absolute yields of the fission products in the neutron induced fission of 232Th and 233U

Absolute yields of 10 fission products in the reactor neutron induced fission of ²³²Th and 17 fission products in the thermal neutron induced fission of ²³³U have been determined using track etch-cum γ-ray spectrometric technique. The number of fissions occurring in the target is obtained by recording the fission events in a mica track detector. The fission product atoms are determined by the direct counting of the irradiated target on a 60 cm³ Ge(Li) detector coupled to a 4096 channel analyser. A one step radiochemical separation was done, before gamma ray counting, for few fission products in the reactor neutron induced fission of ²³²Th. The measured yield values are compared with the available literature data and an analysis of the possible errors are done. The overall uncertainty in the measurements is estimated to be 4–5%.     

Synthesis and conformational analysis of 7,8-diphenyl-1,3,4,6,9,9a-hexahydro-2H-quinolizines

New analogues of julandine with different aromatic methoxy- and chloro-substituents have been synthesized. Some features of the. nmr spectra of the final products and lactams are discussed. The conformational structure of the final products was determined.     

Determination of aromatic amines in FD&C yellow no. 5 by diazotization and coupling followed by reversed-phase HPLC

Benzidine, aniline, 4-aminobiphenyl (4-ABP) and 4-aminoazobenzene are determined at trace levels in the colour additive FD&C Yellow No. 5 by diazotization and coupling with disodium 3-hydroxy-2,7-naphthalenedisulphonate (R-salt). The products are separated and determined by reversed-phase HPLC. All four amines were found in a survey of commercial colours. 4-ABP is determined with 4,5-dihydro-5-oxo-1-(4-sulphophenyl)-1H-pyrazole-3-carboxylic acid as the coupling agent. Calibration is done by spiking a reference commercial colour at several levels.     

Characterization of linear polyurethanes

Methods are described for the qualitative analysis of linear polyurethanes of unknown composition. Based on the type of polymer, determined from the I.R.-spectrum of a polymer film, the products obtained on alkaline hydrolysis under pressure in a Parr bomb are separated by means of ion-exchangers, the course of the analysis being dependent on the type of polymer to be examined. Identification of the isolated hydrolysis products is accomplished by I.R. analysis or thin-layer chromatography.     

Nature and origin of black spots found on Miró paintings: a non-invasive study

The degradation mechanism of cadmium pigments in an oil painting by Joan Miró is determined and reproduced. All possible chemical reactions leading to the observed alteration are checked in laboratory conditions. The behaviour of the different materials (support, pigments and binding medium) are determined. The study of the reaction and products is made using optical microscopy, scanning electron microscopy (SEM) with an energy dispersive X-ray detector, Fourier transform infrared spectroscopy and X-ray diffraction.     

Influence of Encapsulation on The Mechanism of Thermal Destruction of Cyanide Transition Metal Complexes

The results of investigation of the influence of encapsulation on the mechanism of thermal decomposition of cyanide transition metal complexes, based on data obtained by methods of differential thermal analysis (inert atmosphere) and thermodesorption (mass-spectral monitoring of gaseous products) are represented. It was established, that encapsulation of cyanide iron(II) and cobalt(III) complexes in faujasite type zeolite results in the hydrolytic mechanism of thermal destruction of complexes, unlike to bulk analogues, which is determined by essential decreasing of the temperature of complex anions encapsulated destruction beginning, up to temperatures while zeolite water molecules are saved; the gaseous products of thermal destruction composition is determined by the peculiarities of localization of cations of different nature in inclusion compounds. This revised version was published online in August 2006 with corrections to the Cover Date.