Determination of α-bisabolol and d-panthenol in cosmetic products by gas chromatography

α-bisaboloi and d -panthenol are used in many cosmetic preparations, respectively, for their anti-inflammatory and regenerating properties. Their quantitative determination was an important element of their evaluation in these emulsions. Their concentration has been determined by gas chromatographic techniques, using a flame ionization detector. In both cases, the internal standards have been chosen for their compatibility with the analysis of extracted substances.
Owing to the complexity of the cosmetic formulations, a preliminary extraction of α-bisabolol and d -panthenol was necessary. For the two substances the preparative separation was based on a liquid–liquid extraction. After dissolving the emulsion in methanol and diluting it with an aqueous buffer solution α-bisabolol was then extracted by ethyl acetate and d -panthenol by ethyl formate.     

The near field of an antenna surrounded by a dielectric with two teeth

The near field of an antenna surrounded by a dielectric with two teeth is studied when the ambient medium is dissipative. We use the continuity of radial power flux and the boundary conditions at each interface, but not near the discontinuity, to express this field.     

不同电解质溶液及其离子浓度和pH值对改性微滤膜流动电势的影响(英文)

采用商品级α-Al2O3微滤膜.由均质共沉淀法制备了TiO2改性α-Al2O3微滤膜.研究了不同的电解质溶液、溶液的离子浓度和pH值对TiO2 改性的α-Al2O3微滤膜流动电势的影响规律.结果表明:对于NaCl溶液,膜流动电势随溶液离子浓度的增大向降低,其等电点在4.3左右:随着溶液的pH值由3增加到10.膜流动电势由值逐渐变为负值.而对于FeSO4,CaSO4,Na2SO4,NaCl和CaCl2溶液,当溶液的离子浓度固定时,膜流动 电势则随溶液的电导率的增加而降低.     

Project ExCEL: Web‐based Scanning Electron Microscopy for K‐12 Education

Project ExCEL (Extended Classroom for Enhanced Learning) brings the capabilities of scanning electron microscopy (SEM) into classrooms. University and industry personnel, working together, have developed a web‐based interface to allow schools to control a modern SEM. The interface allows a user control of the operating parameters of the microscope, stage movement, and chemical analysis. Such total control is not available on any other system. Since Iowa State University (ISU) pioneered the idea of remote SEM for education, researchers have learned that providing teachers access to sophisticated equipment does not ensure that it will be used. Teachers are busy, and structured curriculums are not conducive for incorporating the SEM into classes. A lack of teacher knowledge of SEMs also discourages their use. To overcome these problems, College of Engineering and College of Education faculty are working together to train future teachers in the SEM. The web‐based SEM is being used in education courses, and selected students (who receive additional training) prepare lesson plans and present their work to the class. In‐service teachers receive instruction in the web‐based SEM through workshops. By using this integrated approach, all science teachers in Iowa will eventually gain the confidence to use the SEM in their classrooms.     

Modelling of Electrical Conductivity of a Silver Plasma at Low Temperature

During the working of electrical fuses, inside the fuse element the silver ribbon first begins to melt, to vaporize and then a fuse arc appears between the two separated parts of the element. Second, the electrodes are struck and the burn-back phenomenon takes place. Usually,the silver ribbon is enclosed inside a cavity filled with silica sand. During the vaporization of the fuse element, one can consider that the volume is fixed so that the pressure increase appears to reach pressures higher than atmospheric pressure. Thus, in this paper two pressures, 1 atm and 10 atm, are considered. The electrical field inside the plasma can reach high values since the distance between the cathode surface and the anode surface varies with time. That is to say from zero cm to one cm order. So we consider various electrical fields: 10~2V/m, 10~3V/m, 5×10~3V/m,10~4V/m at atmospheric pressure and 10~5V/m at a pressure of 10 atm. This study is made in heavy species temperature range from 2,400 K to 10,000 K. To study the plasma created inside the electric fuse, we first need to determine some characteristics in order to justify some hypotheses.That is to say: are the classical approximations of the thermal plasmas physics justified? In other words: plasma frequency, the ideality of the plasma, the Debye-Hückel approximation and the drift velocity versus thermal velocity. These characteristics and assumptions are discussed and commented on in this paper. Then, an evaluation of non-thermal equilibrium versus considered electrical fields is given. Finally, considering the high mobility of electrons, we evaluate the electrical conductivities.     

An 18·3 kb DNA Fragment from Yeast Chromosome VII Carries Four Unknown Open Reading Frames,the Gene for an Asn Synthetase,Remnants of Ty and Three tRNA Genes

An 18·3 kb DNA segment from yeast Saccharomyces cerevisiae chromosome VII encompasses the previously characterized MEP1, NUP57 and PPT1 genes as well as seven new open reading frames (ORFs) of at least 100 residues. G6358 is an ubiquitous glutamine-dependant asparagine synthase. G6362 is a membrane protein highly homologous to a protein of unknown function in the yeast Schizosaccharomyces pombe. Three ORFs (G6324, G6335 and G6365) have no significant homology with previously reported proteins or characteristic motifs. G6321 and G6359, enclosed in longer ORFs, are not likely to be coding. The segment also contains tRNA genes for Asn, Arg and Ile as well as a sigma element and two solo deltas. ORFs and genetic elements are named according to a preliminary working nomenclature. The sequence is recorded in GenBank^TM/EMBL under Accession Number X83099.©1997 John Wiley & Sons, Ltd.     

Approximate pole placement in linear multivariable systems using dynamic compensators†

The problem of approximate pole placement in linear time-invariant systems is generalized to include the case in which the controllable, observable plant of order n is augmented by o, fixed order compensator. It is shown how a low-order compensator may be obtained such that the eigenvalues of the closed-loop system are close to a set of preassigned values.