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1.
聚酯酰胺的合成及表征 总被引:1,自引:0,他引:1
用两种方法合成了聚酯酰胺(PEA)共聚物.一种是两步法,即先合成对苯二甲酸乙醇酰胺(BAET)单体,然后与对苯二甲酸乙二酯(BHET)共缩聚;另一种是一步法.即在酯交换反应中直接添加乙醇胺(EA).两种方法制得的聚酯酰胺(PEA)共聚物测试证明了为产物,并分析了合成中的化学反应. 相似文献
2.
A non-linear least-squares regression program is described which is suitable for PC-compatible microcomputers. The program is written in GWBASIC, but compiled to run with the Intel 8087 fast numeric processor. Subroutines which simulate functions are compiled separately from the main program. Parameters are optimized by a Gauss-Newton-Marquardt algorithm which can be provided with either analytically or numerically calculated partial derivatives. Multi-component potentiometric titrations are simulated and parameters optimized by using analytical derivatives. Spectrophotometric titrations are also simulated, but absorptivities are optimized by linear regression while stability constants are optimized non-linearly by using numerical derivatives. Provision is made for "global analysis" of parameters. The experimental points can be displayed on screen, along with the "best" fit and the speciation. The program is demonstrated here by the determination of the pK(a) values and stability constants of a hydroxypyridinone ligand and its complexes with Fe(III). 相似文献
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4.
Production of acetone-butanol-ethanol from corn mash and molasses in batch fermentation 总被引:2,自引:0,他引:2
The production of solvents from corn mash and molasses in batch fermentation usingClostridium acetobutylicum P 262 was examined. The content of saccharose of beet molasses used in experiments is determined by using the gravimetric
method (52.45% saccharose). The quantities of molasses that are used in the nutrient medium are calculated after doing the
above determination. The samples of fermentation liquid are taken within a certain time, the determination of saccharose is
done by using the same method, and all the saccharose is converted by the microorganism to organic end products. The quantitative
and qualitative determination of acetone-butanol has been made by using gas chromatography. On the other hand, using the three
isolation way, three different cultures are obtained, and with microscopic observations, the cultures obtained are of the
C.acetobutylicum genus. According to the literature values, the concentration of maximum mixed solvent formed during fermentation is about
2%. This is seen in this experiment. There is only a slight difference from this value. This difference is caused by another
organic product that is formed during fermentation. 相似文献
5.
聚酯酰胺的合成及表征 总被引:2,自引:0,他引:2
用两种方法合成了聚酯酰胺(PEA)共聚物.一种是两步法,即先合成对苯二甲酸乙醇酰胺(BAET)单体,然后与对苯二甲酸乙二酯(BHET)共缩聚;另一种是一步法.即在酯交换反应中直接添加乙醇胺(EA).两种方法制得的聚酯酰胺(PEA)共聚物测试证明了为产物,并分析了合成中的化学反应. 相似文献
6.
7.
Formation and Processing of UV Photoproducts: Effects of DNA Sequence and Chromatin Environment 总被引:11,自引:0,他引:11
Gerd P. Pfeifer 《Photochemistry and photobiology》1997,65(2):270-283
8.
Rapid determination of lead and cadmium in biological fluids by electrothermal atomic absorption spectrometry using Zeeman correction 总被引:2,自引:0,他引:2
Procedures for the electrothermal atomic absorption spectrometric determination of lead and cadmium in urine, serum and blood are developed. For serum and blood, the samples are diluted by incorporating 0.015% (w/v) Triton X-100 and 0.1% (w/v) ammonium dihydrogenphosphate to the solutions, which are then introduced directly into the furnace. A solution containing 15% (w/v) hydrogen peroxide and 0.65% (w/v) nitric acid is also introduced into the atomizer by means of a separate injection. Zeeman-based correction is recommended. Both conventional and fast-heating programs are discussed. Calibration is carried out using the standard additions method. The reliability of the procedures is checked by analyzing three certified reference materials and by recovery studies. 相似文献
9.
John J. Mccormack Barbara A. Allen C. Nicholas Hodnett 《Journal of heterocyclic chemistry》1978,15(8):1249-1254
Quinazoline is oxidized by xanthine oxidase initially (and rapidly) to 4-hydroxyquinazoline which subsequently is oxidized more slowly to 2,4-dihydroxyquinazoline. Both oxidative reactions are inhibited strongly by allopurinol. Quinazoline is oxidized by aldehyde oxidase to 4-hydroxyquinazoline but within a short time (3–5 minutes) the reaction ceases; the proposal that cessation of reaction is due to product inhibition is rendered untenable by our observation that 4-hydroxyquinazoline is rapidly oxidized by aldehyde oxidase to 2,4-dihydroxyquinazoline. Preincubation of aldehyde oxidase with quinazoline results in complete inhibition of the ability of the enzyme to oxidize 4-hydroxyquinazoline and the standard substrate N-methylnicotinamide. It appears therefore that quinazoline is able to react with aldehyde oxidase and inactivate it. Quinoxaline and 2-hydroxyquinoxaline are not oxidized by xanthine oxidase but are converted by aldehyde oxidase to 2,3-dihydroxyquinoxaline; all oxidations mediated by aldehyde oxidase are inhibited completely by menadione. 相似文献
10.
《Analytical letters》2012,45(14):1423-1433
Abstract A sensitive method for the determination of caffeine in small plasma samples (50 μ1) is described. The samples are extracted with chloroform and the extrects are freed from interfering compounds by thin-layer chronatography. The spots of caffeine and the internal standard, 7-ethyl theophylline, are scraped off the plates and both compounds are eluted from the scrapings by means of a glass capillary collector. The caffeine in the eluate is quantitated by gas- 相似文献
11.
A new process to make monolithic and transparent silica xerogels with similar properties as silica aerogels by drying at ambient pressure has been studied. The xerogels are produced by strengthening the gel structure by additional precipitation of silica after the initial gelation. The additional precipitation of silica is achieved by ageing the alcogels in solutions of tetraethoxysilane (TEOS) and the aging is followed by a relatively rapid drying (<48 h) at ambient pressure. Due to the increased strength of the alcogels it is shown that the shrinkage during drying can be reduced and hence low density xerogels are obtained even if new monomers are added. 相似文献
12.
The average numbers of singlet peaks in one-dimensional (1D) and two-dimensional (2D) separations of randomly distributed peaks are predicted by statistical-overlap theory and compared against the effective saturation. The effective saturation is a recently introduced metric of peak crowding that is more practitioner-friendly than the usual metric, the saturation. The effective saturation absorbs the average minimum resolution of statistical-overlap theory, facilitating the comparison of 1D and 2D separations by traditional metrics of resolution and peak capacity. In this paper, singlet peaks are identified with maxima produced by a single mixture constituent. Their effective saturations are calculated from published equations for the average minimum resolution of 1D singlet peaks, and from equations derived here for the average minimum resolution of 2D singlet peaks. The fractions of peaks that are singlets in 1D and 2D separations are predicted by statistical-overlap theory as functions of saturation but are compared as functions of effective saturation. The two fractions differ by no more than 0.033 at any effective saturation between 0 and 6, when the distribution of peak heights is exponential and the edge effect is neglected. This result shows that 1D and 2D separations of randomly distributed peaks are about the same in their ability to separate singlet peaks as maxima, when assessed relative to effective saturation. Empirical equations in effective saturation are reported for the fractions of peaks that are singlets. It is argued that the effective saturation is a good metric for comparing separations having different average minimum resolutions. 相似文献
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14.
Hydride affinities (HAs) of the ethynes substituted by a wide range of different substituents are considered by using the B3LYP methodology. The computed values are in fair agreement with available experimental data, which are unfortunately scarce. The trend of changes of the HAs is rationalized by trichotomy formula. One of the important results of this analysis is a finding that similar HA values might result from completely different effects. Alternative sites of the H- attack are examined and the difference in energies relative to the most susceptible positions is interpreted. Structural features of substituted ethyne hydrides are briefly discussed. 相似文献
15.
Arylhydrazines are detected by oxidation with N-bromosuccinimide and coupling with resorcinol to form azo-dyes which are intensely coloured in alkaline media. Hydrazones and osazones are hydrolysed to form the arylhydrazines, which are then tested for 4-Nitro- and 2,4-dinitrophenylhydrazines are tested for by forming their hydrazone with salicylaldehyde and adding alkali to produce a violet colour. The hydroxylamine formed by the hydrolysis of oximes is oxidized by iodine monochloride in the presence of sulphanilic acid; coupling with 8-hydroxyquinoline forms a dye that is red in alkali. Intense colours are immediately produced when primary, secondary and tertiary aromatic amines are mixed with diacetoxyiodobenzene. All the tests are sensitive and appear to be specific. 相似文献
16.
Electroless deposited Ni-P and Co-P coatings, modified by introducing additional elements such as Zn and W are presented.
The characteristics alterations of the multicomponent films are reviewed in connection with the particularities of co-deposition
of the third metal. Based on the fair correspondence between TEM, microdiffraction and precise XRD analysis it is shown that
the structure type and lattice parameters of polycrystalline Ni-Me-P and Co-Me-P films are practically identical to pure Ni
and Co metals. No impurity phase is detected by XRD. The location of the third element is determined using TEM with EDS. The
conclusion is drawn about the grain boundary segregation of Zn and W along with P. Earlier studies by XPS and AES showed that
Zn is partially oxidized, whereas W is in elemental form inside the coatings. Crystallites built of lamellas with thickness
within the nanometer scale are observed in Ni-W-P and Co-W-P by TEM.
Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 6, pp. 764–770.
The text was submitted by the authors in English. 相似文献
17.
J. Dubois W. Fyen D. Rusu E. Peuvrel-Disdier P. Navard 《Journal of Polymer Science.Polymer Physics》1998,36(11):2005-2013
The polarized or depolarized light scattering by well-defined monodispersed sphere doublets is investigated. Two configurations of doublets are studied. In the first (at rest) the doublets are randomly oriented in a plane, in the second the doublets are oriented in a preferred direction. This is achieved by submitting a suspension of doublets to a shear flow. The scattering patterns are compared to two theoretical predictions based on simplified geometries. In the first approach, the doublet is approximated by two interpenetrating spheres scattering independently, whereas in the second, an ellipsoid geometry is used. A good qualitative comparison is obtained. However, the HV and VH patterns of a randomly dispersed suspension are not similar. The observation of the flow of a doublet suspension in shear shows that the doublets are spiraling around the vorticity axis. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2005–2013, 1998 相似文献
18.
A systematic study of the types of fragmentation undergone by internally excited protonated molecules is presented. Two representative functional groups, ethers and ketones, are selected, and both aliphatic and aromatic substituents are examined. The ions are formed by protonation or alkylation in a chemical ionization source, and caused to fragment by collision at high relative kinetic energy. The prevalence of 1,3-rearrangements and the breakdown of the even electron fragmentation rule highlight the ion chemistry uncovered here. Specific findings include: (i) electron unpairing reactions associated with alkyl radical loss are common. These are probably energetically less favorable simple bond cleavages and are observed in competition with entropically less favorable elimination reactions. (ii) Alkane elimination is a characteristic reaction, which often occurs by a four-centered mechanism. Several variations on this reaction type are encountered. (iii) Alkene elimination is another ubiquitous reaction which occurs by a four-centered mechanism in the systems studied here. Competition between alkene and alkane loss is extremely sensitive to the particular system in hand. 相似文献
19.
Relaxation processes of surfactant adsorption and surface tension, which are characterized by two specific relaxation times, are theoretically investigated. We are dealing with fluid interfaces and small initial deviations from equilibrium. For surfactant concentrations below the critical micellization concentration (CMC), we consider adsorption under mixed barrier-diffusion control. General analytical expressions are derived, which are convenient for both numerical computations and asymptotic analysis. Series expansions for the short- and long-time limit are derived. The results imply that the short-time asymptotics is controlled by the adsorption barrier, whereas the long-time asymptotics is always dominated by diffusion. Furthermore, for surfactant concentrations above the CMC, adsorption under mixed micellization-diffusion control is considered. Again, a general analytical expression is derived for the relaxation of surfactant adsorption and surface tension, whose long- and short-time asymptotics are deduced. The derived equations show that at the short times the relaxation is completely controlled by the diffusion, whereas the long-time asymptotics is affected by both demicellization and diffusion. The micellar effect is manifested as an exponential (rather than square-root) decay of the perturbation. The derived expressions are applied to process available experimental data for the nonionic surfactant Triton X-100 and to determine the respective demicellization rate constant. 相似文献
20.
火焰原子吸收法测定植物样品中硼与碘 总被引:13,自引:0,他引:13
将BO^3-3转化为BF^-4,IO^-3转化为I^-以Cd(phen)^2+3络合和硝基苯萃取,用火焰原子吸收法间接测定与碘,其特征浓度达0.016μg/mL1%A和0.028μg/mL1%A,在稻米等样品中作加标回收,硼回收率为92.8-102.4%,碘为97.2-106.7%。 相似文献