Impact of cavity symmetry on mode suppression and increase of free spectral range in solid-state dye microlaser

We describe modeling the solid-state dye laser with the microcavity size comparable to light wavelength.Certain symmetry in the allocation of gain material leads to depletion of odd longitudinal modes that,in turn, increases the tunability range of the microlaser. We provide simple physical explanation for the modeling results.     

Canonical isotopies in Euclidean space

LetG(n,k) denote the space (with the compact-open topology) of homeomorphisms ofR ⁿ which are fixed onR ^k. Theorem 1:G(n, n−2) deforms inG(n, 0) toO(2), whereO(2) is the orthogonal group. Corollary 2: (forn=2) the Kneser theorems. Corollary 3: A EuclideanR ⁿ bundleξ ⁿ overS ^m(m≦∞) which contains anR ⁿ−2 subbundleξ ^{n − 2} is isomorphic, as aG(n,0) bundle, to a Whitney sumξ ^{n − 2} ⊕ξ ². Corollary 4: (n−2) stable homeomorphisms ofR ⁿ orS ⁿ are (n−1) stable, hence stable if orientation preserving. Part of this work represents a portion of the author’s Ph.D. thesis at the University of California, Los Angeles, written under the direction of D. S. Gillman and R. C. Kirby.     

Phase transitions of adsorbed carboxylic acids on zinc oxide and of zinc soaps. Infrared and X-ray diffraction investigations

Summary The reaction between carboxylic acids in benzene solution and suspended zinc oxide particles was investigated by means of infrared spectrometry. The results show how the carboxyl groups react with the zinc oxide forming zinc carboxylate groups at the chemisorption. The chemisorbed acid forms a multilayer at the surface, which gives a new explanation of the protective action of adsorbed acids against flocculation of the particles in nonpolar solvents. The temperature-dependence of the spectra showed transitions at the same temperatures and of the same kind as the corresponding zinc carboxylates, whose spectra were also recorded. The zinc soaps exhibited thermotropic behaviour, and lyotrophy is suggested as the explanation of the multilayer formation.

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Zusammenfassung Mit Hilfe der Infrarotspektrometrie wurde die Einwirkung von Stearins?ure und ?ls?ure auf Zinkoxid untersucht, das in Benzol suspendiert worden war. Durch Carboxylatbildung wird eine multimolekulare Schicht der S?uren auf der Oberfl?che der Zinkpartikel ausgebildet. Die Partikel werden dadurch von der Flokkulation in nichtpolaren L?sungsmitteln geschützt. Die Temperaturabh?ngigkeit der Spektren entspricht der der Zinkcarboxylate.

     

Discrimination of eight chloramphenicol isomers by liquid chromatography tandem mass spectrometry in order to investigate the natural occurrence of chloramphenicol

This paper describes the discrimination of eight different isomers of chloramphenicol (CAP), an antibiotic banned for use in food producing animals, by reversed phase and chiral liquid chromatography in combination with tandem mass spectrometric detection. Previously, by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) the presence of CAP was confirmed in some grass and herb samples collected on Mongolian pastures up to concentrations of 450 μg kg(-1). It was not possible to establish the cause of CAP residues which has initiated research on the natural occurrence of this drug. CAP occurs in the para-configuration and in the meta-configuration and contains two chiral centers thus eight different isomeric configurations exist, namely four (RR, SS, RS, SR) meta-stereoisomers and four para-stereoisomers. It is known that only RR-p-CAP has antimicrobial properties. To find out if the CAP detected in the plant material samples is the active configuration, a high resolution reversed phase LC-MS/MS system was tested for its ability to separate the different isomers. This system proved to be able to discriminate between some isomers, but not between RR-p-CAP and SS-p-CAP, also called dextramycin. Despite a detailed elucidation of the product ions and the fragmentation patterns of all isomers, MS/MS did not add sufficient specificity for full discrimination of the isomers. Therefore a chiral liquid chromatographic separation with MS/MS detection that is able to distinguish all isomers was developed and finally the isomeric ratio of non-compliant plant material samples and some CAP formulations was determined using this system. This showed that Mongolian grass and herb samples only contain the biological active isomer of CAP as do the obtained formulations. Therefore the CAP present in the plant material might origin from the production by soil organisms or from a manufactured source.     

POLYMERIC SURFACTANTS BASED ON OLEIC ACID IV. Lamellar Liquid Crystal Polymerization of Sodium Oleate/Oleic Acid/Aliphatic Diene/Water System

The lamellar liquid crystalline phase in the system consisting of sodium oleate (NaOL), oleic acid (OLA), and water was determined. The interlayer spacing (d) of the lamellar liquid crystal was measured through small angle X-ray diffraction, which indicated that oleic acid molecules were solubilized between the end methyl groups at low concentrations, and then were located within the hydrocarbon chain layer with further increase of its concentration. Cross-linking agents were added to the system, which were found being located partly in between the end methyl groups and partly within the hydrocarbon chain layers. The liquid crystal phase of NaOL/OLA/H₂O system with the cross-linking agent was polymerized at 60 °C, which turned out to be a mixture of liquid crystals and solids. Interlayer spacing decreased by about 10 Å, indicating a disruption of the ordered structure by the polymerization. The polymerization took place not only within the hydrocarbon layer, but also in between the layers separated by the end methyl groups. The resulting polymer lowered the surface tension of water to below 30 mN/m, with a critical micellization concentration of about O.25g/L.     

Vapor Pressures of Phenethyl Alcohol in the System Water-Phenethyl Alcohol and the Triblock Copolymer EO4.5PO59 EO4.5

ABSTRACT

The phase diagram of water, phenethyl alcohol (PEA) and the triblock copolymer EO_4.5PO₅₉EO_4.5, (EO = ethylene oxide, PO = propylene oxide), L101, was determined and the vapor pressures of PEA were measured for different phases.

The phase diagram was almost identical to the corresponding one with a simple nonionic surfactant, Laureth 4, (?C₁₂EO₄), but the PEA vapor pressure variation with mole fraction was significantly different reflecting the strong molecular interaction between PEA and the polymer. This distinction was mainly due to difference in molecular size; vapor pressure plots against weight fraction gave curves with only moderate variance.

The results were used to discuss the variation in the PEA vapor pressure with time after application of a vesicular solution of PEA stabilized either by L101 or Laureth 4. The moderate differences in vapor pressures had a significant influence on the estimated curves of PEA pressure versus time.     

Phase Equilibria of Methoxydimethyloctylsilane,Tetramethyldioctyldisiloxane in Organic Solvents

Abstract The phase diagrams and partial solubility parameters for methoxydimethyloctyl silane (MDOS), tetramethyl dioctyl disiloxane (TDDS), and several organic components were determined. The solubility limits were established by quantitative analysis and compared to the refractive index of known single phase mixtures. The partial solubility parameters were used to provide a qualitative analysis of the phase equilibria. The results showed the phase equilibria depended on the polarity and hydrogen bonding characteristics of the solvents. The solubility of TDDS was reduced with increasing polarity/hydrogen bond character of the amphiphiles solvents.     

Visibility in ghost imaging with classical partially polarized electromagnetic beams

We consider classical second-order ghost imaging with uniformly partially polarized electromagnetic beams and examine the effect of the degree of polarization of the incident light on the visibility of the image. Closed-form expressions for two previously proposed definitions of visibility are derived. Both results are physically similar and show that the visibility increases with the degree of polarization. Hence, a polarized beam is superior to an unpolarized one to obtain a high-visibility ghost image. Some related issues in recent literature are also addressed.