首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Changes to the fundamental and analytical parameters of a plasma have been investigated when ethanol has been added to aqueous or organic solutions. Excitation temperature, electron number density, and intensity of the H(alpha) line increased when ethanol has been added to aqueous solutions, while an electron density decrease and signal reduction have been found when ethanol has been added to xylene. The sensitivity has been improved for all ethanol concentrations when water has been the solvent, but the reverse has been found for xylene solutions.  相似文献   

2.
12-Hydroxymethyltetrahydroabietic acid has been homopolymerized by melt condensation and homopolyester has been obtained. Vinyl 12-hydroxymethyltetrahydroabietate has been prepared from 12-hydroxymethyltetrahydroabietic acid by vinyl interchange procedure with vinyl acetate, and has been homopolymerized, copolymerized with vinyl chloride, vinyl acetate, and terpolymerized with styrene and acrylonitrile. The acrylate ester of 12-hydroxymethyltetrahydroabietic acid also has been prepared from 12-hydroxymethyltetrahydroabietic acid and acrylyl chloride. The acrylate thus obtained has been homopolymerized and copolymerized with vinyl chloride and vinyl acetate. Polymers thus obtained have been characterized.  相似文献   

3.
Changes to the fundamental and analytical parameters of a plasma have been investigated when ethanol has been added to aqueous or organic solutions. Excitation temperature, electron number density, and intensity of the H line increased when ethanol has been added to aqueous solutions, while an electron density decrease and signal reduction have been found when ethanol has been added to xylene. The sensitivity has been improved for all ethanol concentrations when water has been the solvent, but the reverse has been found for xylene solutions.  相似文献   

4.
A nucleoprotein has been isolated from the gonads of the Caspian sturgeon and its composition has been determined. It has been shown that it contains 55% of DNA, 2% of RNA, 36% of protamines, and about 7% of nonprotamine proteins of nonbasic nature. The nucleoprotein has been hydrolyzed with trypsin, and the amino acid compositions of some hydrolysis products have been studied. On the basis of the results obtained, the hypothesis has been put forward of a possible linkage of the DNA with the basic proteins. It has been shown that protamines react with the DNA through the basic amino acid residues located at various regions of their molecules.  相似文献   

5.
A simple nonlinear theory of viscoelasticity has been developed for application to elastomers. The interpretation of nonlinear viscoelastic responses based on Gibbs-DiMarzio theory has been identified at a molecular level and hence structural understanding has been established. The introduced model is applied to strain imposed conditions. From this, a relaxation process has been revealed for the resultant stress, where a dependence of relaxation time on the state of strain has been established.  相似文献   

6.
任树林 《化学研究》2000,11(2):58-61
推导了络合返滴定曲线方程 ,绘制了络合返滴定曲线和计算了pN突跃。并利用双曲正弦函数的性质 ,提出了内含最大敏锐指数的络合返滴定误差计算公式 ,从而获得了计算络合返滴定pN突跃范围的公式。  相似文献   

7.
The problem of the stability of a confined atom when it is extracted from the confining cavity has been investigated, modeled by a spherical hard wall potential. The ionization probability when the atom is released from confinement has been obtained. The dependence of the ionization probability on the confinement radius and on the quantum numbers of the initial confined state has been studied. The probability density function of the ionization energy of the ejected electron has been obtained for the different cases considered. The oscillatory structure of this distribution function, with a principal maximum located in the neighborhood of the energy of the initial state and minima very close to zero has been elucidated. The sudden approximation has been applied and the analytic continuation method has been used to calculate the different stationary states.  相似文献   

8.
A nickel sulfide catalyst which efficient in the decarbonylation of fatty acids to olefins and dienes has been obtained for the first time by treating alumina-supported nickel sulfate with hydrogen, and its properties have been studied. In its presence, the olefin selectivity of the reaction can exceed 90%. The kinetics of stearic acid deoxygenation to heptadecenes has been investigated, a kinetic model has been constructed, and a mechanism has been proposed for the reaction over this catalyst. Olefin oligomerization is the dominant side reaction. Kinetic evidence for the catalytic inhibition of oligomerization by nickel hydrides formed on the catalyst has been obtained. The compositions of active site–reactant adsorption complexes have been discussed.  相似文献   

9.
The diffusion of water in non-isocyanate polyurethaneacetals (PUA) of various kinds and compositions has been studied. The direct relationship between the composition of polymers, their degree of crystallinity, morphology and diffusional characteristics has been demonstrated. It has been shown that by changing the polymer composition one can obtain hydrated polymer systems of every type, hydrophobic, hydrophilic and moderately hydrophilic. The kinetics of hydrolytic degradation of PUA in HCl solutions (pH = 0·1) between 20 and 75°C has been investigated. Hydrolysis of acetal bonds has been found to occur in the amorphous phase of a polymer sample, which is mostly formed by the fragments of urethane glycol.The influence of morphology on PUA diffusional characteristics and their stability to hydrolysis has been determined.It has been shown that the physico-chemical properties of PUA can be regulated without the introduction of new compounds.  相似文献   

10.
The conductivity of ring-shaped deposits formed at the periphery of evaporating droplets of silver nanoparticle colloidal solutions has been studied. The dependence of the resistance of the ring-shaped deposits on nanoparticle size has been shown to exhibit a percolation transition. The specific conductivity of the deposits has been estimated in relation to their geometric shapes. The conductivity has been established to nonmonotonically depend on nanoparticle sizes. It has been noted that, in rather strong fields, the conductivity of the composite layers dramatically increases after some induction period. The X-ray spectra of silver have been revealed to alter for samples the conductivity of which has increased under the action of an external electric field.  相似文献   

11.
12 α-Hydroxymethylabiet-7,8-enoic acid has been homopolymerized by melt condensation, and a partially crystalline polyester has been obtained. Vinyl 12 α-hydroxymethylabiet-7,8-enoate has been prepared from 12 α-hydroxymethylabiet-7,8-enoic acid by vinyl interchange with vinyl acetate and has been homopolymerized, copolymerized with vinyl chloride, vinyl acetate, butadiene, and acrylonitrile, and terpolymerized with styrene and acrylonitrile. Polymers thus obtained have been characterized.  相似文献   

12.
Different types of cyclodextrins (CDs) have been tested as mediators for the water phase transfer of organic-capped CdS nanocrystals (NCs), and alphaCD has been demonstrated to be the most effective system. The formation of a complex based on alphaCDs and colloidal NCs has been considered to be responsible for the phase transfer process and extensively investigated by optical, structural, and calorimetric measurements, as a function of the experimental parameters (pH and NC and CD concentration). A mechanism for the complexation phenomena has been suggested. The fabrication of 2/3 D supramolecular architectures has been proposed according to two different strategies. First, a layer-by-layer procedure has been used to obtain multilayered structures where polyelectrolyte layers have been intercalated with negatively charged alphaCD-CdS NC complexes by exploiting electrostatic interaction between polyelectrolyte and cyclodextrin OH groups. Second, a monolayer of CdS NCs has been deposited onto a self-assembled monolayer of sulfated CDs, thus combining the use of an electrostatic-force-based approach and host-guest chemistry. The important role played by host-guest interactions has then been revealed.  相似文献   

13.
A sensitive and specific radioimmunossay procedure (RIA) has been developed for the measurement of Human Placental Lactogen (HPL). Pure HPL has been labelled with125I and a specific activity of 100 μCi/μgm of HPL has been attained. Dextran-coated charcoal has been employed to separate the bound from the free hormone in radioimmuno-assay. The sensitivity of this technique has been found to be 0.2 ng of HPL. Intraassay and inter assay variations have been found to be less than 10%. This procedure has been adopted to establish the normal range of HPL in pregnant women at different periods of gestation, and to evaluate risk pregnancies.  相似文献   

14.
In order to estimate the potential of steroid estrogens modification, three D-homoanalogs of estrogens have been prepared; their structures and biological properties have been studied. The expansion of D-ring in such compounds has lead to strong decrease if the uterotropic action, however, the unfavorable hypertriglyceridemic effect has been retained. The latter has been eliminated by combined action of the studied steroids and ursolic acid; therewith the hypocholesterolemic activity has been retained.  相似文献   

15.
The electronic absorption spectrum of 2-bromopyrimidine in the u.v. region has been recorded in vapour phase and in solution phase in different solvents. Only one system has been observed in vapour phase and it has been identified as π* ← n transition. In solution phase two systems have been identified. The system on the longer wavelength side has been identified as corresponding to the one observed in vapour phase while the other one has been assigned to a π* ← π transition. The infrared spectrum of this molecule has also been recorded and analysed. Help of these i.r. data has been taken to analyse the u.v. spectrum of 2-bromopyrimidine, considering the molecule as belonging to C point group.  相似文献   

16.
A study of factor XIII A-subunit has been made by electrospray ionisation mass spectrometry. Factor XIII has been isolated and rigorously purified, and the intact A-subunit protein has been analysed to confirm its molecular weight accurately for the first time. Thrombin proteolysis of the A-subunit has been monitored and the resulting cleavage products, the activated A-subunit protein and the Activation Peptide, have been analysed by electrospray ionisation mass spectrometry to confirm the site of proteolysis. Facile and rapid separation of the Activation Peptide from the activated A-subunit protein has been achieved using simple on-line separation techniques. The molecular weight measurements have been repeated numerous times to provide an indication of the precision and variability of the analyses.  相似文献   

17.
In this work, bovine hemoglobin (Hb) has been studied mainly by the fluorescence method. pH has been found to exert a profound effect on Hb structure. This has been confirmed by fluorescence and circular dichroism (CD) studies. The pH-induced change in quaternary structure of Hb indirectly affects its secondary structure. This in turn affects ligand binding to Hb at various pH. The binding of two amphiphiles, a bile salt and a surfactant, have been investigated. The pH-induced structural modification of Hb has been confirmed by studies with the well-known denaturant urea and the polarity probe ANS, which has been used as an extrinsic fluorophore.  相似文献   

18.
Starting from tetrahydroabietic acid the model compounds tetrahydroabietoyl chloride, 2-aminoethyltetrahydroabietate hydrochloride, and 2-isocyanatoethyltetrahydroabietate have been prepared. Carbamate and urea derivatives of the isocyanate have been prepared. A Diels-Alder adduct of levopimaric acid and acrylic acid has been prepared and converted to its diacid chloride. The β-aminoethyl ester hydrochloride has been synthesized and converted to a diisocyanate which has been polymerized with poly(tetramethylene glycol) and also with p-phenylenediamine. Dimerex resin, a technical polymerized rosin, has been similarly converted to a diisocyanate. This isocyanate has not proven to be useful as a polymer-forming intermediate.  相似文献   

19.
The spatial arrangement of active component (Pt) particles on the surface of a support (Sibunit globule) has been studied by bright-field electron tomography. A tomographic attachment for a standard specimen holder and tomographic grids have been designed. The tomographic procedure has been refined, and adequate tilt series alignment and tomographic reconstruction algorithms have been chosen. The 3D distribution of the active component in the catalyst grain has been studied: particles hidden in micropores have been directly observed, and the size of the pores connecting internal cavities with the exterior has been estimated.  相似文献   

20.
用INDO系列方法对C60自由基负离子进行了几何构型优化,得到D2h对称性的构型,表明C60--确实发生了Jahn-Teller畸变,导致单键变短,双键变长,形成15种键,9种不等同碳原子,其额外负电荷主要分布在赤道附近。以此构型为基础,计算了C60--的电子光谱,与实验值吻合,在对光谱进行理论指认的同时讨论了光谱红移的原因。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号