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1.
为探讨小儿脑性瘫痪(CP)体内微量元素的变化,测定了128例脑性瘫痪患者血钙、锌、铁、铜、镁含量,随机选择128例正常儿童进行对照分析。结果表明,两组病例血锌、铜、镁均在正常范围,脑瘫组血钙56例、铁45例低于正常参考值,健康组血钙16例、铁11例低于正常参考值。经统计学处理,两组病例中血钙、铁、铜、镁含量具有显著性差异(P<0.05),血锌无显著性差异(P>0.05)。提示脑瘫儿童血钙、铁、铜、镁含量均低于正常儿童,补充钙、铁、镁等可能有利于脑瘫康复。  相似文献   

2.
Literature information on the HPLC of alkaloids, including adsorption, reversed-phase, ion-exchange, ion-pair, and other variants is generalized. Results are given of the chromatographic analysis of various classes of alkaloids with an indication of the conditions of separation, and the columns used, and also of the methods of detection. The advantages and disadvantages of the HPLC variants are discussed. The review includes the literature over the last 14 years. Scientific Center for Chromatography, Institute of Chemistry and Physics of Polymers, Uzbek Academy of Sciences, Tashkent. Institute of the Chemistry of Plant Substances, Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 595–613, September–October, 1991.  相似文献   

3.
A computer model of the active layer of the cathode of a hydrogen-oxygen fuel cell with a solid polymer electrolyte is studied. The active mass of the electrode consists of equidimensional grains of the substrate (agglomerates of carbon particles with platinum particles embedded in them) and a solid polymer electrolyte (Nafion). The flooding by water can be experienced by both the pores in the substrate grains, which facilitate the oxygen penetration into the active layer of the electrode, and the voids between the grains. All possible versions of the flooding of these pores by water are considered. A calculation of the optimum, at a given polarization of the electrode, value of electrochemical activity, the thickness of the active layer, and the weight of platinum is performed. The major parameters of the system are the concentrations of grains of the substrate and solid polymer electrolyte, the size of these grains, the platinum concentration in the substrate grains, the average diameter of pores in the substrate grains, and the polarization of electrodes. The ultimate aim of the work is to estimate how the flooding of pores of the active layer of the cathode by water affects the magnitude of the optimum current, the effective thickness of the active layer, and the weight of platinum.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 35–47.Original Russian Text Copyright © 2005 by Chirkov, Rostokin.  相似文献   

4.
The influence of eluent composition (the nature and concentration of the ion-pair reagent, medium pH, the concentration of the buffer solution, and the content of acetonitrile) on the retention of asymmetric dimethylhydrazine and its decomposition products on hydrophobized silica gels under the ion pair chromatography conditions was studied. It was shown that, for these sorbates, the influence of ion-pair reagents can be described correctly in terms of stoichiometric models. Empirical dependences of the retention of the components studied on the concentration of the buffer solution and the volume concentration of acetonitrile were determined. Conditions for the separation of the components were suggested. Original Russian Text ? A.D. Smolenkov, S.A. Ponomarenko, O.A. Shpigun, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 3, pp. 565–574.  相似文献   

5.
This review generalizes the results of structural investigations of the polysaccharides of the O-specific side chains, of the core oligosaccharides, and of the lipid A of the pseudotuberculosis microbeYersinia pseudotuberculosis which causes Far-Eastern scarlatina-like fever. The complete structures of the repeating units of the specific polysaccharides from the lipopolysaccharides of serovars I A, I B, III, IV A, V A, V B, and VI which are responsible for the O-antigenic specificity of the microorganism are given. For the majority of serovars the repeating unit is represented by a branched pentasaccharide. Exceptions are the lipopolysaccharides of serovars I A and III which have a tetrasaccharide repeating unit. The presence of an aminosugar residue at the reducing end, by which the O-specific chain is attached to the oligosaccharide of the core, is common and characteristic for the lipopolysaccharides isolated from all the serovars. The structures of the core oligosaccharide and of lipid A, which are common for all serovars ofYersinia pseudotuberculosis, are given.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, USSR Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 163–171, March–April, 1988.  相似文献   

6.
Fuerstenau [D.W. Fuerstenau, in: M.L. Hair (Ed.), Dekker, New York, 1971, p. 143] has already discussed the role of hydrocarbon chain of surfactants, the effect of alkyl chain length, chain structure and the pH of the solution on the adsorption process of surfactants. Later Kosmulski [M. Kosmulski, Chemical Properties of Material Surfaces, Surfactant Science Series, vol. 102, Dekker, New York, Basel, 2001] included the effect of surfactant concentration, equilibration time, temperature and electrolyte in his approaches. Certainly, the character of the head groups of the surfactant and the properties of the adsorbent surface are the basis for the adsorption process. Different surfactants and adsorbents cause different adsorption mechanisms described firstly by Rosen [M.J. Rosen, Surfactants and Interfacial Phenomena, second ed., Wiley, New York, 1989]. These adsorption mechanisms and their influencing factors were studied by electrokinetic investigations. Here only changes of the charges at the surfaces could be detected. To control the results of electrokinetic investigations they were compared with results from ellipsometric measurements. In the case of surfactant adsorption the chain length was vitally important. It could be shown by the adsorption of alkyl trimethyl ammonium bromides onto polymer films spin coated at wafer surfaces. The influence of the chain length depending on surface properties of the polymer film was studied. Streaming potential measurements were applied for these investigations. The obtained results enabled us to calculate the molar cohesive free energy per mol of CH2-group in the alkaline chain of the surfactant if all other specific adsorption effects were neglected.  相似文献   

7.
Isotherms of adsorption of oleic, linoleic, and linolenic acids on magnetite from solutions in carbon tetrachloride and hexane are measured. When CCl4 is used as a solvent, the adsorption values increase in the following order: oleic, linoleic, and linolenic acid. In the case of hexane, the order is opposite. Adsorption isotherms of the fatty acids on aggregated magnetite are described in terms of the theory of volume filling of micropores. It is disclosed that, in the case of CCl4 , the limiting adsorption values and characteristic energies of the process increase in a series: oleic, linoleic, and linolenic acid, but in the case of hexane, they decrease in the same sequence. Upon the adsorption of fatty acids from solutions in CCl4 and hexane on finely dispersed magnetite, molecules of the acids and solvents compete for the active sites on the adsorbent surface. The number of double bonds in the molecules of unsaturated fatty acids and the desolvation of both the adsorbent surface and adsorbate molecules substantially affect the adsorption of these acids. The effect of the solvents is most pronounced for the adsorption of oleic acid, decreasing with a rise in the number of double bonds in a fatty acid molecule.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 779–783.Original Russian Text Copyright © 2004 by Korolev, Ramazanova, Yashkova, Balmasova, Blinov.  相似文献   

8.
Nanosphere lithography (NSL) has been regarded as an inexpensive, inherently parallel, high-throughput, materials-general approach to the fabrication of nanoparticle arrays. However, the order of the resulting nanoparticle array is essentially dependent on the quality of the colloidal monolayer mask. Furthermore, the lateral feature size of the nanoparticles created using NSL is coupled with the diameter of the colloidal spheres, which makes it inconvenient for studying the size-dependent properties of nanoparticles. In this work, we demonstrate a facile approach to the fabrication of a large-area, transferrable, high-quality latex colloidal mask for nanosphere lithography. The approach is based on a combination of the air/water interface self-assembly method and the solvent-vapor-annealing technique. It enables the fabrication of colloidal masks with a higher crystalline integrity compared to those produced by other strategies. By manipulating the diameter of the colloidal spheres and precisely tuning the solvent-vapor-annealing process, flexible control of the size, shape, and spacing of the interstice in a colloidal mask can be realized, which may facilitate the broad use of NSL in studying the size-, shape-, and period-dependent optical, magnetic, electronic, and catalytic properties of nanomaterials.  相似文献   

9.
Heavy metals in wastes exist as multiple pollutants. The study of the interactions between multiple pollutants and soils should be of significance in practice. In the present study, the effect of chromate on adsorption and desorption behavior of Cu(II) in two variable charge soils was investigated, with the emphasis on the adsorption and desorption equilibria of Cu(II). The results showed that chromate can affect adsorption and desorption of Cu(II) in the colloidal systems of two variable charge soils. The extent of the effect was related to the initial concentrations of chromate and Cu(II), the system pH, and the nature of the soils. The presence of chromate led to an increase in the adsorption of Cu(II). For example, in the presence of 0.5, 0.8, 1.0, and 1.5 mmol L(-1) of chromate, for the rhodic ferralsol the adsorption of Cu(II) increased by 15.3, 18.0, 19.0, and 20.2%, respectively. For the hyperrhodic ferrasol, the corresponding figures were 11.9, 17.0, 20.3, and 26.1%, respectively. The presence of chromate also caused an increase in the desorption of Cu(II). For instance, in the presence of 0.5, 1.0, and 1.5 mmol L(-1) of chromate, the desorption for the rhodic ferralsol increased by 16.9, 27.5, and 34.1%, respectively. For the hyperrhodic ferralsol, the corresponding figures were 18.1, 35.6, and 51.4%, respectively. The increments of the adsorption and desorption increased with the increase in equilibrium concentration of Cu(II) in the solution. For instance, when the equilibrium concentrations were 0.5, 1.0, 1.5, and 2.0 mmol L(-1), the increments for the rhodic ferralsol were 2.5, 3.2, 3.3, and 3.0 mmol kg(-1), respectively. For the hyperrhodic ferralsol, the corresponding figures were 2.9, 3.5, 4.0, and 4.2 mmol kg(-1), respectively. The effect of chromate for the hyperrhodic ferralsol was greater than that for the rhodic ferralsol. This is caused by the difference in the content of iron oxides for the two soils. The increments of the adsorption and the desorption of Cu(II) increased with the rise in pH, reaching a maximum value, and then decreased. It can be assumed that the increment of the adsorption was caused by the change in surface charge of the soils induced by the adsorption of chromate and the cooperative adsorption of chromate adsorbed and Cu(II). The increase of electrostatically adsorbed Cu(II) was responsible for the increase in the desorption of Cu(II).  相似文献   

10.
The polarographic behavior of copper, lead, antimony, and zinc ions in the presence of the title ligand, HEDP, is discussed. In highly alkaline solutions, the reversible wave of copper splits into two components, reversible and irreversible, the first of which is attributed to the reduction of the free cupric ions and the second wave was assigned to the reduction of the copper phosphonate species. The polarograms of zinc and antimony showed the presence of a single irreversible wave. In the case of lead, a quasi-reversible wave is observed. Cobalt and nickel forms inactive phosphonate chelates as inferred from the suppression of the wave heights with increasing of both the concentration of the ligand and the pH of the medium. In the presence of sufficiently excess HEDP buffered to pH 11.8, mixtures of the six elements showed the presence of four reasonably separated waves at half-wave potential values ?0.51, ?0.83, ?1.17, and ?1.55 V vs SCE corresponding to the reductions of copper, lead, antimony, and zinc complexes, respectively. The possibility of the individual and simultaneous analysis of these elements in their ternary mixtures with cobalt and nickel is discussed.  相似文献   

11.
12.
Recently,a series of sensing films based upon the supra-molecular behavior of aromatic compounds immobilized on substrate surfaces and its dependence to the composition of the medium have been successfully prepared. It is found that the properties and performances of the films depend upon various factors,including the nature of the sensing element,the way of immobilization,the nature of the substrate,and the density of the sensing element immobilized etc. To accelerate and deepen the studies,it was decided to carry out the theoretical simulation of the sensing films based upon the proposed principle. The fluorescence behavior of a functional plate,of which the surface is functionalized by single layer immobilization of aromatic compounds(sensing elements),is simulated by Monte Carlo simulation method. The effects of the immobilization density of a sensing element,the excitation efficiency,and the association efficiency,P,which is a characteristic parameter of an aromatic compound,between the molecules of the sensing element on the ratio of the excimer emission to the monomer emission of the plate have been systematically examined. But the effects of the length and flexibility of a spacer are neglected,because in this simulation aromatic compounds are immobilized on a plate by the short stiff spacer. It is demonstrated that,for a functionalized plate of a short stiff spacer in a polar solvent( in this case,the association tendency is strong,and P is close to 1),aromatic compounds of middle excitation efficiency might be suitable as sensing elements. In addition,the immobilization density of the sensing element should be controlled. A recommended value is about 50%.  相似文献   

13.
It has been established that, in contrast to the pure substances, the thermal decomposition of hexacyanotransition metal complexes, encapsulated in the large cavities of faujasite, occurs by a hydrolytic mechanism. The composition of the gaseous products of the thermal decomposition depend on the characteristics of the localization of the cations in the inclusion compounds. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 107–112, March–April, 1999.  相似文献   

14.
由于碳酸盐矿物的质地特点,石灰岩文物在露天环境中极易发生表面溶蚀,其上赋存文化信息的文字、纹饰和符号等雕刻痕迹也随之湮灭,对其文物价值造成了严重减损。从耐候性和兼容性角度考虑,无机保护材料显然更适合于石灰岩文物的表面防护处理。近年来,基于草酸钙、磷灰石和碳酸钙等钙基材料的石灰岩文物表面防护研究逐渐兴起并开始走向应用。本文就上述钙基保护材料的特点、防护膜制备和应用实践等做了归纳和评述,以期为石灰岩文物保护研究提供参考和借鉴。  相似文献   

15.
We have studied the proteins of the pollen and ovules of the cotton plant. No differences were observed in the electrophoregrams of the proteins from Gossypium hirsutum L. and from G. barbadense L. In the spectrum of the pollen proteins, the main components quantitatively were polypeptides with molecular masses of 34, 44, 47, and 52 kDa. The species G. raimondii Ulbr. differed considerably, with the main polypeptides quantitatively having molecular masses of 27, 36, 46, and 58 kDa. In representatives of genomic group C, interspecies differences were observed in the protein spectra of the pollen. No appreciable differences were observed spectrally in the proteins of the cottonplant ovules.Biolog Scientific Production Combine, Academy of Sciences of the Republic of Uzbekistan, Republic of Uzbekistan, Institute of Genetics, Academy of Sciences of the Republic of Uzbekistan, Republic of Uzbekistan, Tashkent ul. F. Khodzhaeva, 28. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 454–456, May–June, 1995. Original article submitted September 13, 1994.  相似文献   

16.
The spatial structure of the sesquiterpene humulane alcohol juniferol, which is represented in the crystal by two conformers, IA and IB, differing by the conformation of the C2...C9 section, has been established by the x-ray structural method. The strain energies of the conformers have been calculated by the method of molecular mechanics. The barrier to the interconversion of the conformers by rotation of the C2...C9 section has been calculated; it amounts to 7–8 kcal/mole. This value of the transformation barrier permits the assumption that the two conformers also exist in solution, their interconversion being hindered. Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Crystallography, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 757–762, November–December, 1990.  相似文献   

17.
The electrophoresis of a concentrated dispersion of non-Newtonian drops in an aqueous medium, which has not been investigated theoretically in the literature, is analyzed under conditions of low zeta potential and weak applied electric field. The results obtained provide a theoretical basis for the characterization of the nature of an emulsion and a microemulsion system. A Carreau fluid, which has wide applications in practice, is chosen for the non-Newtonian drops, and the unit cell model of Kuwabara is adopted to simulate a dispersion. The effects of the key parameters of a dispersion, including its concentration, the shear-thinning nature of the drop fluid, and the thickness of the double layer, on the electrophoretic behavior of a drop are discussed. In general, the more significant the shear-thinning nature of the drop fluid is, the larger the mobility is, and this effect is pronounced as the thickness of the double layer decreases. However, if the double layer is sufficiently thick, this effect becomes negligible. In general, the higher the concentration of drops is, the smaller the mobility is; however, if the double layer is either sufficiently thin or sufficiently thick, this effect becomes unimportant.  相似文献   

18.
Mechanisms of foam destruction by oil-based antifoams   总被引:9,自引:0,他引:9  
Oils and mixtures of oils with hydrophobic particles are widely used in various technologies and consumer products to control foaminess and foam stability. The aim of this review is to summarize our current understanding of the mechanisms of foam destruction by such substances, which are usually called antifoams or defoamers. The experimental results show that two types of antifoam can be distinguished (called for brevity "fast" and "slow") which differ in the modes of their action. Fast antifoams are able to rupture the foam films at the early stages of film thinning. As a result, fast antifoams destroy completely the foam in less than a minute, in a typical foam-stability test. Microscopic observations have shown that the fast antifoams rupture the foam films by the so-called "bridging" mechanisms, which involve the formation of oil bridges between the two surfaces of the foam film. The stability/instability of these oil bridges is explained by using the theory of capillarity. In contrast, the oily globules of the slow antifoams are unable to enter the surfaces of the foam films and are first expelled into the Plateau borders (PBs). Only after being compressed by the narrowing walls of the PBs (due to water drainage from the foam), are the globules of the slow antifoams able to enter the solution surface and to destroy the adjacent foam films. Typically, the process of foam destruction by slow antifoams requires much longer time, minutes or tens of minutes, and a residual foam of well-defined height is observed in the foam tests. The experiments show that there is no direct relation between the magnitudes of the entry, E, spreading, S, and bridging, B, coefficients, on one side, and the antifoam efficiency, on the other side. The only requirement for having active antifoam, with respect to the bridging mechanisms, is that B should be positive. On the other hand, the barrier preventing the emergence of pre-emulsified antifoam globules on the solution surface (so-called "entry barrier") is of crucial importance for the mode of foam destruction and for the antifoam efficiency. Measurements of the entry barrier with recently developed film trapping technique (FTT) showed that antifoams possessing low entry barriers act as fast antifoams, whereas high barriers correspond to slow or inactive antifoams, although E, S, and B coefficients could be strongly positive in the latter case. A good agreement between the magnitude of the entry barrier, measured by FTT, and the height of the residual foam, in the presence of slow antifoams, was experimentally established and theoretically explained. The importance of various factors, such as the size of antifoam globules, oil spreading, kinetics of surfactant adsorption, hydrophobicity of solid particles in mixed oil-solid antifoams, and the presence of amphiphilic additives (foam boosters), is discussed from the viewpoint of the mechanisms of antifoaming. The main experimental methods, used for studying the modes of antifoam action, are briefly described.  相似文献   

19.
We use a statistical thermodynamic approach and a simple thermodynamic model of hydration to examine the molecular origins of the volumetric properties of solutes. In this model, solute-solvent interactions are treated as a binding reaction. The free energy of hydration of the noninteracting solute species coincides with the free energy of cavity formation, while the free energy of solute-solvent interactions is given by the binding polynomial. By differentiating the relationship for the free energy of hydration with respect to temperature and pressure, one obtains the complete set of equations describing the thermodynamic profile of hydration, including enthalpy, entropy, volume, compressibility, expansibility, and so forth. The model enables one to rigorously define in thermodynamic terms the hydration number and the related concept of hydration shell, which are both widely used as operational definitions in experimental studies. Hydration number, nh, is the effective number of water molecules solvating the solute and represents the derivative of the free energy of hydration with respect to the logarithm of water activity. One traditional way of studying hydration relies on the use of volumetric measurements. However, microscopic interpretation of macroscopic volumetric data is complicated and currently relies on empirical models that are not backed by theory. We use our derived model to link the microscopic determinants of the volumetric properties of a solute and its statistical thermodynamic parameters. In this treatment, the partial molar volume, V degrees, of a solute depends on the cavity volume, hydration number, and the properties of waters of hydration. In contrast, the partial molar isothermal compressibility, K degrees T, and expansibility, E degrees, observables, in addition to the intrinsic compressibility and expansibility of the cavity enclosing the solute, hydration number, and the properties of waters of hydration, contain previously unappreciated relaxation terms that originate from pressure- and temperature-induced perturbation of the equilibrium between the solvated solute species. If significant, the relaxation terms may bring about a new level of nonadditivity to compressibility and expansibility group contributions that goes beyond the overlap of the hydration shells of adjacent groups. We apply our theoretical results to numerical analyses of the volume and compressibility responses to changes in the distribution of solvated species of polar compounds.  相似文献   

20.
中药质量控制技术发展展望   总被引:6,自引:0,他引:6  
梁鑫淼  丰加涛  金郁  郭志谋  徐青 《色谱》2008,26(2):130-135
本文从中药产业需求、现代化需求、技术需求、机遇与挑战等方面概括了中药质量控制技术发展的背景;讨论了中药质量控制技术对于提高中药药效和安全性、推动产业发展和推进中药国际化的意义;综述了中药质量控制技术的现状,分析了在过程控制、安全性控制、标准品和对照品制备、指纹图谱技术等方面的不足;提出了中药质量控制技术应重点发展以分离和表征技术为主的中药质量控制关键技术、中药安全性控制技术、中药质量控制标准体系、中药质量控制原创性技术和中药标准品、对照品生产技术,制定技术标准,建立具有中药特色的过程控制和产品质量控制标准。  相似文献   

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