Estimation of Joule heating effect on temperature and pressure distribution in electrokinetic-driven microchannel flows

In this study we present simple analytical models that predict the temperature and pressure variations in electrokinetic-driven microchannel flow under the Joule heating effect. For temperature prediction, a simple model shows that the temperature is related to the Joule heating parameter, autothermal Joule heating parameter, external cooling parameter, Peclet number, and the channel length to channel hydraulic diameter ratio. The simple model overpredicted the thermally developed temperature compared with the full numerical simulation, but in good agreement with the experimental measurements. The factors that affect the external cooling parameters, such as the heat transfer coefficient, channel configuration, and channel material are also examined based on this simple model. Based on the mass conservation, a simple model is developed that predicts the pressure variations, including the temperature effect. An adverse pressure gradient is required to satisfy the mass conservation requirement. The temperature effect on the pressure gradient is via the temperature-dependent fluid viscosity and electroosmotic velocity.     

Electrochemical oxidation of alcohols: Part II preparative anodic oxidation of secondary alkanols employing lithium nitrate

The nitrate-mediated oxidation of simple alkanols to the corresponding ketones is described. Except for compounds containing several tertiary hydrogens the procedure is simple to perform and gives clean products in high current yield.     

Interlayer Bond Formation in Black Phosphorus at High Pressure

Black phosphorus was compressed at room temperature across the A17, A7 and simple‐cubic phases up to 30 GPa, using a diamond anvil cell and He as pressure transmitting medium. Synchrotron X‐ray diffraction showed the persistence of two previously unreported peaks related to the A7 structure in the pressure range of the simple‐cubic phase. The Rietveld refinement of the data demonstrates the occurrence of a two‐step mechanism for the A7 to simple‐cubic phase transition, indicating the existence of an intermediate pseudo simple‐cubic structure. From a chemical point of view this study represents a deep insight on the mechanism of interlayer bond formation during the transformation from the layered A7 to the non‐layered simple‐cubic phase of phosphorus, opening new perspectives for the design, synthesis and stabilization of phosphorene‐based systems. As superconductivity is concerned, a new experimental evidence to explain the anomalous pressure behavior of T_c in phosphorus below 30 GPa is provided.     

反对数微分简易示波伏安法的研究

在获得微分简易地波伏安图的实验线路中,增加了反对数装置,提出了反对数微分简易示波伏安法。该方法被应用于铝合金中微量铜和分子筛中微量钴的测定,获得了满意结果。     

Oxygenation of Simple Olefins through Selective Allylic C−C Bond Cleavage: A Direct Approach to Cinnamyl Aldehydes

A novel metal‐free allylic C−C σ‐bond cleavage of simple olefins to give valuable cinnamyl aldehydes is reported. 1,2‐Aryl or alkyl migration through allylic C−C bond cleavage occurs in this transformation, which is assisted by an alkyl azide reagent. This method enables O‐atom incorporation into simple unfunctionalized olefins to construct cinnamyl aldehydes. The reaction features simple hydrocarbon substrates, metal‐free conditions, and high regio‐ and stereoselectivity.     

Tertiary amines promoted synthesis of symmetrical 1,3-disubstituted ureas

Symmetrical 1,3-disubstituted ureas and cyclic ureas have been synthesized from corresponding isocyanates and diisocyanates by a new versatile, simple and quick method in the presence of tertiary amines at room temperature. The method under investigation has several advantages over the existing techniques, as it is simple to carry out; does not require complicated equipment; work-up is simple, as it does not use expensive chemicals. Moreover, the yields are almost quantitative. It has a potential for commercial applications in pharmaceutical chemistry.     

Purity Determination of Phosphorus Compounds by Internat- Standard31 P Nmr Spectroscopy. an Experimental Study and Validation

Abstract

Due to the proportionality between the area of the NMR signal and the number of nuclei, internal standard³¹P NMR spectroscopy is in principle a rapid and simple method for determination of the purity of phosphorus compounds.nuclei, internal standard³¹P NMR spectroscopy is in principle a rapid and simple method for determination of the purity of phosphorus compounds.nuclei, internal standard³¹P NMR spectroscopy is in principle a rapid and simple method for determination of the purity of phosphorus compounds.nuclei, internal standard³¹P NMR spectroscopy is in principle a rapid and simple method for determination of the purity of phosphorus compounds.     

Photochemical transformations of xanthohumol

A photoinduced procedure for the addition of simple alcohols to xanthohumol, the major prenylated flavonoid of hop plants, has been developed. The reaction is regioselective, simple, and occurs in one pot to afford two new β adducts of xanthohumol.     

Applying the concepts of density functional theory to simple systems

Equations are derived for the chemical potential and local hardness of the ground states of helium and the related two electron ions. With these properties it is possible to correct the energies of the simple single‐zeta wave functions to the nearly exact values. The calculations are simple for these simple systems. In principle, it is possible to extend this method to all atoms and molecules. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Synthesis of 2-phenyl pyridine derivatives from aryl ketones and 1,3-diaminopropane using palladium acetate as a catalyst

A simple and efficient method for the synthesis of 2-phenyl pyridine via cyclization of aryl ketone with 1,3-diaminopropane using palladium acetate is established. This method is mild, operationally simple, involves short reaction time and involves easy workup procedure to afford the corresponding 2-phenyl pyridines in moderate to good yield.     

Interactions between flow and superstructure of liquid crystalline polymers

The monodomain equation for rigid rodlike polymers in the nematic phase is here extended, in a simple form, to the polydomain situation. The mathematical problem is further simplified by considering a two-dimensional restriction. Preliminary results are presented for simple shear flows, showing the formation of a superstructure along the sample thickness.     

Excitation profiles of resonance raman spectra in condensed media

A simple model, obtained by reducing a multimode system to a simple coordinate, is proposed to explain the broadening of RRS in liquid or solid media. It is shown that the coherent excitation of the near continuous background of low-frequency modes can cause homogeneous broadening of RRS profiles. The model is applied to the excitation profile of β-carotene.     

Density functional theory of inhomogeneous liquids. I. The liquid-vapor interface in Lennard-Jones fluids

A simple model is proposed for the direct correlation function (DCF) for simple fluids consisting of a hard-core contribution, a simple parametrized core correction, and a mean-field tail. The model requires as input only the free energy of the homogeneous fluid, obtained, e.g., from thermodynamic perturbation theory. Comparison to the DCF obtained from simulation of a Lennard-Jones fluid shows this to be a surprisingly good approximation for a wide range of densities. The model is used to construct a density functional theory for inhomogeneous fluids which is applied to the problem of calculating the surface tension of the liquid-vapor interface. The numerical values found are in good agreement with simulation.     

Simple Chemical Reactions in the Solid State: Towards Elaborating a Conception

In contrast to the conventional homogeneous kinetics, there is no conception of a simple reaction in the solid-state reaction kinetics. The geometric-probabilistic phenomenology currently in use is not adequate for describing the interplay between the chemical mechanism and the observed kinetic behaviour. An attempt is made to formulate a conception of simple reaction in the solid state as a basis for constructing kinetic models of involved reactions.     

镍催化芳基硼酸与芳基醛的加成反应

发展了一种基于NiCl2(PPh3)2/IPr·HCl催化体系的、芳基硼酸和芳香醛进行加成反应制备二芳基甲醇类化合物的新方法,并取得了较好的催化效果。该方法具有简便,易操作等优点,是过渡金属催化制备二芳基甲醇类化合物的一个重要补充。     

Ultimate tensile properties of elastomers. VI. Strength and extensibility of a styrene–butadiene rubber vulcanizate in equal biaxial tension

The ultimate properties of an unfilled styrene-butadiene rubber vulcanizate in equal biaxial tension were determined by inflating a circular membrane into a bubble. Tests were made at several extension rates (evaluated at the pole) from about 0.15 to 4 min^?1 and at temperatures from ?43 to 90°C. The stress in the vicinity of the pole when rupture occurred was evaluated from the pressure, the radius of curvature, and the extension ratio λ, the latter two quantities being obtained from photographic data. Below 70°C, the ultimate extension ratio λ_b is approximately 5.2 and is essentially independent of extension rate and temperature, in striking contrast to the behavior in simple and constrained biaxial tension (pure shear). Likewise, the rupture stress is manyfold greater than in either simple or constrained biaxial tension. From the extremum points of failure envelopes, the maximum extension ratio (λ_b)_max in equal biaxial tension is 5.7 and in simple tension is 7.2. An examination of ruptured membranes showed that, except at 70 and 90°C, rupture began away from the pole in a region where the stress state is unequal biaxial tension. Hence, values of the ultimate properties in truly equal biaxial tension are no doubt somewhat greater than those obtained from the membrane tests. However, it is shown that (λ_b)_max in truly equal biaxial tension must be lower than that in simple tension by at least 10%. A consideration of rupture data in simple, constrained biaxial, and equal biaxial tension leads to the conclusion that no simple failure criterion is applicable for interrelating data obtained under the several states of combined stress. The rupture patterns and factors that affect the site of rupture initiation and the mode of crack growth are also discussed.     

Mild oxygen activation with isobutyraldehyde promoted by simple salts

Oxygen activation using an aldehyde as a sacrificial reductant and mediated by metalloporphyrins is a radical process with a variable induction period in which the macrocycle function is to generate the acyl radicals to initiate a chain mechanism. This function can be also efficiently promoted by simple metal salts, which leads to a very simple and practical oxidative system that is able to epoxidize alkenes in good yields.     

Statistical thermodynamics for chain molecules with simple RNA tertiary contacts

A statistical thermodynamic model is developed for chain molecules with simple RNA tertiary contacts. The model, which accounts for the excluded volume effect and the nonadditivity in the free energy, enables reliable predictions for the conformational entropy and partition function for simple tertiary folds. Illustrative applications are made to conformational transitions involving simple tertiary contacts. The model can predict the interplay between the secondary and the tertiary interactions in the conformational changes. Though the present form of the theory is tested and validated in a two-dimensional lattice model, the methodology, which is developed based on a general graphical representation for chain conformations, is applicable to any off-lattice chain representations. Moreover, the analytical formulation of the method makes possible the systematic development of the theory for more complex tertiary structures.     

Proline-catalyzed asymmetric assembly reactions: enzyme-like assembly of carbohydrates and polyketides from three aldehyde substrates

Directed asymmetric assembly of simple achiral building blocks into stereochemically complex molecules like triketides has been described for the first time using l-proline catalyzed asymmetric double aldol reactions. The product pyranoses contain four asymmetric centers constructed under proline catalysis in a highly diastereoselective and modestly enantioselective fashion from three aldehyde molecules. These results suggest that the construction of complex products from simple starting materials is within the realm of organocatalysis involving the simple naturally occurring amino acid l-proline. Our successful assembly of pyranoses from simple aldehydes under proline catalysis suggests that this approach may warrant consideration as a prebiotic route to sugars and polyketides.