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Use of an on-column frit structure, constructed by sintering a mixture of glass powders, makes it possible to ground a fused-silica capillary on its side prior to its outlet. Electroosmotic pressure permits convenient sample collection. We illustrate the use of this device by depositing the eluent in a continuous manner on a moving surface. This provides a permanent record of the separated species in a mixture. 相似文献
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305.
D.L Albritton W.J Harrop A.L Schmeltekopf R.N Zare 《Journal of Molecular Spectroscopy》1973,46(1):89-102
Existing high-resolution data for the Second Negative band system have been analyzed using a nonlinear least-squares fit that employs numerically diagonalized Hamiltonians. Values for the full set of molecular constants of the A2Πu and X2Πg states are obtained for the first time. In addition to values for ν0(v′, v″), Bv, and Dv, the values for the spin-orbit coupling constants Av are determined for both states. For the X2Πg state, which is near Hund's case (a), the agreement between these Av″ values and those predicted by theory is good. However, for the A2Πu state, which is much nearer to case (b), these Av′ values and theory disagree both in magnitude and in variation with vibrational level. The A2Πu state is an inverted state for vibrational levels v′ ≤ 5 and is a regular state for levels v′ = 6–8 (the upper limit of present high-resolution data). Λ-doubling parameters are determined for the X2Πg state, the only state where Λ-doubling is statistically significant. Spin-rotation interaction is not statistically significant for either state. Dunham Yi0 and Yi1 expansion coefficients are determined for each state. Theoretical Dv values calculated from RKR potentials are used to improve the Bv values in the reduction of the data. 相似文献
306.
Khalafi-Nezhad A Parhami A Bargebid R Molazade S Zare A Foroughi H 《Molecular diversity》2011,15(2):373-381
A simple, clean and highly efficient method for the preparation of polyhydroxyl aromatic compounds is described from the reaction
of 2,6-bis(methylol)phenols and different substituted phenols in the presence of silica sulfuric acid (SSA) as a heterogeneous
catalyst. SSA afforded the clean synthesis of target compounds in much higher yields than traditional catalysts. The established
method is also suitable for the synthesis of phloroglucinol derivatives (Phloroglucides) and other polyhydric phenols. Besides
the easy work-up of the reaction mixture, the comfortable purification of the products is another advantage of this method. 相似文献
307.
In this study, an acetaminophen-modified glassy carbon electrode (ACMGCE) was fabricated for the purpose of investigating its electrochemical behavior by cyclic voltammetry (CV). ACMGCE serves as an excellent bifunctional electrocatalyst for the oxidation of ascorbic acid (AA) and glutathione (GSH) in a phosphate buffer solution (pH 7.0). The kinetic parameters such as the electron transfer coefficient, α, and the heterogeneous electron transfer rate constant, k', for the oxidation of AA and GSH at the ACMGCE surface were determined by CV. In addition, detection limits of 3.89 μM for AA and 0.37 μM for GSH were obtained at the ACMGCE using a differential pulse voltammetric (DPV) method. In DPV, the bifunctional modified electrode could separate the oxidation peak potentials of AA, GSH, adrenaline (AD) and tryptophan (Trp) present in the same solution, though the peak potentials were indistinguishable at a bare GCE. Finally, the modified electrode was successfully applied to the determination of AA in a pharmaceutical preparation and GSH in a human plasma sample. 相似文献
308.
Molecularly imprinted polymers are generated by curing a cross-linked polymer in the presence of a template. During the curing process, noncovalent bonds form between the polymer and the template. The interaction sites for the noncovalent bonds become "frozen" in the cross-linking polymer and maintain their shape even after the template is removed. The resulting cavities reproduce the size and shape of the template and can selectively reincorporate the template when a mixture containing it flows over the imprinted surface. In the last few decades the field of molecular imprinting has evolved from being able to selectively capture only small molecules to dealing with all kinds of samples. Molecularly imprinted polymers (MIPs) have been generated for analytes as diverse as metal ions, drug molecules, environmental pollutants, proteins and viruses to entire cells. We review here the relatively new field of surface imprinting, which creates imprints of large, biologically relevant templates. The traditional bulk imprinting, where a template is simply added to a prepolymer before curing, cannot be applied if the analyte is too large to diffuse from the cured polymer. Special methods must be used to generate binding sites only on a surface. Those techniques have solved crucial problems in separation science as well as chemical and biochemical sensing. The implementation of imprinted polymers into microfluidic chips has greatly improved the applicability of microfluidics. We present the latest advances and different approaches of surface imprinting and their applications for microfluidic devices. 相似文献
309.
Suppose that G is a graph and ${f: V (G) \rightarrow \mathbb{N}}$ is a labeling of the vertices of G. Let S(v) denote the sum of labels over all neighbors of the vertex v in G. A labeling f of G is called lucky if ${S(u) \neq S(v),}$ for every pair of adjacent vertices u and v. Also, for each vertex ${v \in V(G),}$ let L(v) denote a list of natural numbers available at v. A list lucky labeling, is a lucky labeling f such that ${f(v) \in L(v),}$ for each ${v \in V(G).}$ A graph G is said to be lucky k-choosable if every k-list assignment of natural numbers to the vertices of G permits a list lucky labeling of G. The lucky choice number of G, η l (G), is the minimum natural number k such that G is lucky k-choosable. In this paper, we prove that for every graph G with ${\Delta \geq 2, \eta_{l}(G) \leq \Delta^2-\Delta + 1,}$ where Δ denotes the maximum degree of G. Among other results we show that for every 3-list assignment to the vertices of a forest, there is a list lucky labeling which is a proper vertex coloring too. 相似文献
310.
A. Phirouznia V. Zare Hesari S. Hassanpour Bourkheili A. Namdar 《Applied Physics A: Materials Science & Processing》2014,116(3):1059-1063
We have performed a non-equilibrium quantum transport calculations for a two-terminal mesoscopic system including a magnetic quantum dot. Using the non-equilibrium Green’s function technique, we have obtained electric current and charge distribution in the temperature range from 1 to 10 K as a function of magnetic field. Results indicate that the density of carriers essentially can be controlled by temperature and bias voltage. 相似文献