Conjugate Model for Heat and Mass Transfer of Porous Wall in the High Temperature Gas Flow

Heat and mass transfer of a porous permeable wall in a high temperature gas dynamical flow is considered. Numerical simulation is conducted on the ground of the conjugate mathematical model which includes filtration and heat transfer equations in a porous body and boundary layer equations on its surface. Such an approach enables one to take into account complex interaction between heat and mass transfer in the gasdynamical flow and in the structure subjected to this flow. The main attention is given to the impact of the intraporous heat transfer intensity on the transpiration cooling efficiency.

Disentangling mechanical and mass effects on nanomechanical resonators

Micro and nanomechanical resonators are powerful and label-free sensors of analytes in various environments. Their response, however, is a convolution of mass, rigidity, and nanoscale heterogeneity of adsorbates. Here we demonstrate a procedure to disentangle this complex sensor response, to simultaneously measure both mass and elastic properties of nanometer thick samples. This turns an apparent disadvantage of these resonators into a striking and unique asset, enabling them to measure more than mass alone.

Determination and identification of isoflavonoids in Radix astragali by matrix solid-phase dispersion extraction and high-performance liquid chromatography with photodiode array and mass spectrometric detection

The isoflavonoids in Radix astragali were determined and identified by HPLC-photodiode array detection-MS after extraction employing matrix solid-phase dispersion (MSPD). As a new sample preparation method for R. astragali, the MSPD procedure was optimized, validated and compared with conventional methods including ultrasonic and Soxhlet extraction. The amounts of two major components in this herb, formononetin (6) and ononin (2), were determined based on their authentic standards. Four major isoflavonoids, formononetin (6), ononin (2), calycosin (5) and its glycoside (1), and three minor isoflavonoids, (6aR,11aR)-3-hydroxy-9, 10-dimethoxypterocarpan (7), its glycoside (3), and (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavone-7-O-beta-D-glycoside (4), were identified based on their characteristic two-band UV spectra and [M + H](+), [aglycone + H](+) and [A1 + H](+) ions, etc. The combined MSPD and HPLC-DAD-MS method was suitable for quantitative and qualitative determination of the isoflavonoids in R. astragali. (C) 2003 Elsevier B.V. All rights reserved.

Determination of Point of Zero Charge of Tunisian Kaolinites by Potentiometric and Mass Titration Methods

This paper deals with determining points of zero charge of natural and Na+-saturated mineral kaolinites using two methods: (1) acid-base potentiometric titration was employed to obtain the adsorption of H+ and OH- on amphoteric surfaces in solutions of varying ionic strengths in order to determinate graphically the point of zero net proton charge (PZNPC) defined equally as point of zero salt effect (PZSE); (2) mass titration curve at different electrolyte concentrations in order to estimate PZNPCs by interpolation and to compare with those determined by potentiometric titrations. The two methods involved points of zero charge approximately similar for the two kaolinites between 6.5-7.8, comparable to those reported previously and were in the range expected for these clay minerals. The comparison of potentiometric surface titration curves obtained at 25 °C and those published in the literature reveals significant discrepancies both in the shape and in the pH of PZNPCs values.

Influence of isooctanol on the interfacial activity and mass transfer of ytterbium(III) using 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester as an acidic extractant

BACKGROUND: Introducing an adduct into an extractant system is an effective method of improving extraction performance. The effect of additives upon extraction is very important, especially in the case of interfacial behaviour. In most work published in the literature, there is little data on the interfacial behaviour of extractants and modifiers. As the mass transfer must pass through an interface, the influence of isooctanol on the interfacial activity and mass transfer of ytterbium(III) using 2-ethylhexylphosphonic acid mono-2-ethlhexyl ester has been investigated.RESULTS: With increasing amounts of isooctanol, the interfacial tension and surface excess (Gamma(max)) of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester(HEHEHP)-isooctanol system decreased, and the area of the absorbed HEHEHP molecule (Amin) increased. The interfacial activity of the HEHEHP-isooctanol system varied significantly depending on ionic strength and temperature and the mass transfer flux decreased with increasing isooctanol content.

Characterization of triterpenoidic saponin mixture in crude extracts from leaves of Acanthopanax senticosus Harms by saponin structural correlation and mass spectrometry

Eighteen triterpenoidic saponins in crude extracts from leaves of Acanthopanax senticous Harms have been investigated by electrospray ionization multi-stage tandem mass spectrometry and high-resolution mass spectrometry. In ESI-MS spectra, predominant [M + Na](+) ions in the positive ion mode have been observed for molecular mass information. Meanwhile, specific structural correlations between these ions are firstly found. The 18 peaks (ions) can be classified into three groups (group D, E, and F with mass increase) with each group including six peaks. There is a mass difference of 132 Da between group D and E for each corresponding peak in turn (for example peak 1 to peak 7), indicating one more pentose residue was attached to saponins in group E than those corresponding in group D. The mass difference of 146 Da between group E and F implies one more deoxy-hexose attached to saponins in group F than those corresponding in group E. The structural correlations of the corresponding ions are confirmed by tandem mass spectrometry and high-re solution mass spectrometry. These structural features can not only facilitate the rapid characterization of the native known saponins in crude plant extracts, thus avoiding tedious derivation and separation of saponins, but also help find novel compounds of the same type in a specific medicinal plant.

PEG-supported dipyridyl ligand for palladium-catalyzed Suzuki and Suzuki-type reactions in PEG and aqueous media

An air- and water-stable PEG-supported bidentate nitrogen ligand is prepared and its applications in the palladium-catalyzed Suzuki reaction of aryl halides with arylboronic acids in PEG and Suzuki-type reaction of aryl halides with sodium tetraphenylborate in aqueous media are reported. The homogeneous catalyst system is environmentally friendly and offers the advantages of high activity, reusability and easy separation.

Preparation and mass spectrometric study of egg yolk antibody (IgY) against rabies virus

Rabies virus was used as the antigen to immunize laying chickens. Anti-rabies virus immunoglobulin Y(IgY) was isolated from yolks of the eggs laid by these chickens using a two-step salt precipitation and one-step gel filtration protocol. The purified IgY was reduced with dithiothreitol, and heavy chains (HC) and light chains (LC) were obtained. In addition, the purified IgY was digested with pepsin and the fragment with specific antigen binding properties (Fab) was produced. Using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOFMS), the average molecular weights of IgY, HC, LC, and Fab were determined as 167 250, 65 105, 18 660, and 45,359 Da, respectively. IgY has two structural differences compared with mammalian IgGs. First, the molecular weight of the heavy chain of IgY is larger than that of its mammalian counterpart, while the molecular weight of the light chain of IgY is smaller. Second, upon pepsin digestion, anti-rabies virus IgY is degraded into Feb, in contrast to mammalian IgG, which has been reported to be degraded into F(ab')(2) under the same conditions. Copyright (C) 2001 John Wiley & Sons, Ltd.

X-ray photoelectron spectroscopy and mass spectrum of organic tin compounds

The relationship between the chemical displacement of the binding energy and the different chemical environment for 12 organic tin compounds was studied by means of X-ray photoelectron spectronscopy. The different substituents in the compounds have influence on the tin outer electron and Sn-O bond, which was discussed by Xray photoelectron spectroscopy and mass spectrum.

X-ray photoelectron spectroscopy and mass spectra study of alpha-amino acid

X-ray photoelectron spectroscopy and mass spectrometry have been used to study the ten alpha-Amino Acids. The chemical shiftss of N-1s electron binding energy have been explained by means of the difference in the hydrocarbon group of amino acids. The influence of the hydrocarbon group on NH2 has been disscussed using the XPS and MS results.

Studies on extraction and mass transfer of samarium and neodymium in hollow fiber membrane (HFM) with HEH/EHP

The membranes of polyvinylidene fluoride, which were synthesized by our laboratory, were used to study the transfer and extraction performances of Nd(III) and Sm(III) with the extraction system of HEH/EHP-kerosene. The results show that the membrane material was suitable to the study on membrane extraction, and could offer a good transfer performance in the membrane construction parameters selected, The extraction reaction in the membrane module was the same as that in liquid-liquid process, HEH/EHP ammoniated for increasing the mass transfer coefficient was almost the same with increasing the concentration of HEH/EHP, and H+ was still transferred first at higher pH range of feed solution when HEH/EHP was ammoniated, The controlling model of the membrane extraction process was the diffusion model accompanied by interfacial reaction, The controlling function of interfacial reaction would increase gradually with the increasing of the membrane pore size. The mass transfer coefficient increased when extraction and stripping were carried out simultaneously.

Adsorption of dodecatungstosilicic acid on to activated carbons from aqueous and acidic media

Heteropoly acids (HPAs), such as dodecatungstosilicic acid (SiW12), adsorb strongly on to activated carbons. The surface chemical properties of the activated carbons have a pronounced effect on the adsorption of HPAs. To obtain activated carbons with the desired surface chemical properties, modification with mineral acids has been applied. The adsorption isotherms of SiW12 from aqueous solution and various acidic media on to the various carbons have been studied. On the basis of the results obtained, an adsorption model for HPAs from acidic media is presented.

Adsorption of PMo12 and SiMo12 on activated carbon in aqueous and acidic media

In various acidic media, such as H2SO4, HCl, H3PO4, acetic acid of 3 M in hydrogen ion concentration, and pure acetic acid, the adsorption of heteropolyacids composed of molybdenum with the Keggin structures PMo12 and SiMo12 on different activated carbons is studied. In acidic media, the adsorbed amount of heteropolyacids is much higher than that in water. By considering the relation between adsorbed amount and the acid strength of the media, as far as SiMo12 and PMo12 are concerned, there exist different trends.