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101.
Drying dissipative structural patterns formed in the course of drying colloidal crystals of silica spheres (110 nm in diameter)
in water, methyl alcohol, ethyl alcohol, 1-propyl alcohol, diethyl ether, and in the mixtures of ethyl alcohol with the other
solvents above have been studied on a cover glass. The macroscopic broad rings were formed in the outside edges of the dried
film for all the solvents examined. Furthermore, much distinct broad rings appeared in the inner area when the solvents were
ethyl alcohol, methyl alcohol, and their mixtures. Profiles of the thickness of the dried films were sensitive to the organic
solvents and explained well with changes in the surface tensions, boiling points, and viscosities of the solvents. The macroscopic
and microscopic spoke-like crack patterns formed. The drying area (or the drying time) increased (or decreased) as the surface
tension of the solvent decreased. However, the absolute values of these drying parameters are determined also by the boiling
points of the solvents. Importance of the fundamental properties of the solvents is supported in addition to the characteristics
of colloidal particles in the drying dissipative pattern formation. 相似文献
102.
利用Foster-Boys定域化程序和STO-3G ab initio方法,对含有C、H、O、N原子的100多个有机链状分子进行了研究,得到定域分子轨道能量及其相互作用参数。应用这些参数和定域分子轨道模型,对于众多的含有C、H、O、N原子的有机链状分子,可得到相应的正则分子轨道能量及其与定域分子轨道的关系。以此预测它们的电离能,结果与实验值符合较好。 相似文献
103.
A review of sample preparation methods for organic acids in biological fluids, in particular serum and urine, is presented. It covers techniques on organic acid determination without sample preparation, release of organic acids from binding locations, removal of proteins by protein precipitation and ultrafiltration, isolation of the organic acids by liquid-liquid and liquid-solid extraction, purification of the extract, derivatization and pre-fractionation. The various alternative sample preparation steps are compared and critically discussed. Examples of applications including profile analysis of organic acids by gas chromatography (GC), determination of particular organic acids by GC or liquid chromatography and determination of fatty acids as a distinct chemical class of acids demonstrate that the kind of sample preparation chosen depends strongly on the analytical aims. 相似文献
104.
有机溶剂对镧和钇ICP光谱信号的增敏机理研究 总被引:2,自引:0,他引:2
本文考察了有机溶剂(乙酸丁酯)及有机试剂(PMBP)引入ICP-AES对稀土元素镧和钇光谱信号的影响。实验结果表明,有机溶剂的引入明显增大了待测物的传质效率,从而导致分析灵敏度的改善。与水相相比,有机相的引入对ICP激发温度未产生明显影响,但使线对强度比(LogI^ /I)增强,有利于待测物的电离。 相似文献
105.
Nitrogen-15 labeled pyrroles have been prepared from commercially available 15N glycine or sodium nitrite using the Barton-Zard, Knorr, and Kleinspehn approaches. These pyrroles were used as intermediates in the synthesis of per-15N labeled porphyrins needed for the analysis and assignment of vibrational spectra for sedimentary porphyrins. Etioporphyrin-I was prepared via pyrromethene intermediates, while etioporphyrins II-V and a related tetrahydrobenzoporphyrin were synthesized via stepwise routes involving the copper(II) mediated cyclization of a,c-biladienes as the key step. Detailed analyses of both the proton and carbon-13 NMR spectra provide nitrogen-15 coupling constants for these important structures. 相似文献
106.
107.
Alejandro Marcó Ramón Compañó Roser Rubio Pilar Domènech Albert Palangues Miguel Maestro 《Mikrochimica acta》2002,140(1-2):131-139
Four inter-comparison exercises on organic elemental analysis were carried out between 1997 and 2001 by the Department of
Analytical Chemistry of the University of Barcelona, together with the Microanalysis Service and the Institute of the Marine
Sciences, which both belong to the CSIC in Barcelona, and the University of A Coru?a. More than sixty laboratories participated
in these exercises. Here we describe the design and characteristics of the trials, the samples and the homogeneity tests applied.
We report the results obtained for the analysis of carbon, hydrogen, nitrogen, sulphur and oxygen, their statistical analysis,
and the most relevant aspects of the technical discussion meetings.
Received December 20, 2001; accepted March 18, 2002; published online July 22, 2002 相似文献
108.
Paolo Samorí Silvia Pieraccini Stefano Masiero Gian Piero Spada Giovanni Gottarelli Jürgen P. Rabe 《Colloids and surfaces. B, Biointerfaces》2002,23(4):283-288
We report a tapping mode scanning force microscopy investigation on the growth from solutions of a lipophilic deoxiguanosine derivative on the basal plane of a muscovite mica surface. By varying the chemical composition of the substrate surface it is possible to drive the self-assembly towards either layered thin films, which are very likely to consist of guanosine quartets, or nanoribbons, comprising hydrogen bonded networks. Both these two architectures, which are peculiar to the guanine base itself, are of notable importance for the fabrication of molecular nanowires. Moreover, the first arrangement provides evidence that the guanosine is able to behave as ionophore, thus, suggesting its utilization in the development of solid-state ion selective sensors. 相似文献
109.
The change in semiconductive properties of β-apo-8′-carotenal, astacene and methyl bixin on adsorption of various vapours
on the crystallite surfaces has been studied at a constant sample temperature. The adsorption of vapours enhances the semiconductivity
of the polyenes appreciably. This enhancement depends on the chemical nature and also on the pressure of the adsorbed vapour.
The adsorption and desorption kinetics follow the modified Roginsky-Zeldovich relation. A two stage desorption process, the
first stage of which gives a Lennard-Jones potential energy curve and is followed by a rate-determining transition over a
potential energy barrier to the second stage of adsorption forming weakly bound complexes between the vapour molecules and
the polyene crystallites, can explain satisfactorily the experimentally observed kinetic data. 相似文献
110.
Alfred Baszczyk Matthias Fischer Carsten vonHnisch Marcel Mayor 《Helvetica chimica acta》2006,89(9):1986-2005
The synthesis, characterization, and optical properties of a series of new 2,6‐disubstituted naphthalene‐bisimide dyes as molecular rods comprising terminal AcS groups is reported. The first series of dyes ( 1 – 3 ), comprising phenylhetero (Ph‐X) core substituents, cover a broad range of the VIS spectrum, ranging from yellow ( 2 ) over red ( 3 ) to blue ( 1 ). The second series of dyes contains benzylhetero (Bn‐X) core substituents ( 4 – 7 ). For the same heteroatom connecting the substituent to the naphthalene core, both series were found to display comparable colors. For the second series, the colors were blue ( 4 ), red ( 5 ), and violet ( 6, 7 ). The Ph‐X‐substituted dyes 1 – 3 are nonfluorescent, in contrast to the Bn‐X‐substituted compounds 4 – 7 . This rich variety of optical features that can be adjusted by rather small alterations of the core substituents makes these structurally very comparable molecular rods ideal candidates for optically triggered molecular‐transport investigations. Also, thanks to the terminal AcS groups, these compounds can be placed between nobel‐metal electrodes for optically triggered transport experiments. 相似文献