On a class of atmospheres occurring in stellar hydrodynamic theory

Summary A derivation is given of the basic equation governing the behaviour of small disturbances in a stratified compressible atmosphere (with a locally unstable region bounded by semi-infinite stable regions) in which the time of radiative relaxation is constant.By means of a new independent variable that is a function of the equilibrium entropy stratification, various properties of such media can be established in a straightforward manner. A general expression for the wave energy flux is derived, and integral properties arising from this quantity are used to obtain in particular, results pertaining to the eigenfunctions and eigenvalues for strongly radiating systems. In addition, a model of an atmosphere with a strongly-radiating region embedded in a convective zone, and bounded by semi-infinite radiation-free layers is discussed in some detail. The paper is an approach towards providing some preliminary but unified results in the theory of stellar hydrodynamics.

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Résumé Nous donnons une dérivation de l'équation de base qui détermine la propagation des petites perturbations dans une atmosphère compressible stratifiée (présentant une zone d'instabilité locale entre des zones de stabilité semi-infinies) dont le temps de relaxation radiative est constant.Au moyen d'une nouvelle variable indépendante, fonction de la stratification de l'entropie en équilibre, diverses propriétés de tels milieux sont déterminées simplement. On donne une formulation du flux de l'énergie ondulative et on emploie les propriétés intégrales qui en résultent pour obtenir en particulier des résultats concernant les eigenfonctions et les eigenvalues pour des systèmes à forte radiation énergétique. En outre, on étudie en détail le modèle d'une amtosphère caractérisée par une zone à forte radiation insérée dans une zone convective entre des couches semi-infinies sans radiation.Ce travail présente quelques conclusions préliminaires mais cohérentes dans le domaine de la théorie de l'hydrodynamique stellaire.

     

Competition between photodimerization and photocycloaddition of dimethyl 3-dehydrogibberellenate to ethylene, 1,1-dichloroethylene and trichloroethylene

Photocycloadditions of dimethyl 3-dehydrogibberellenate 1 to ethylene, 1,1-dichloroethylene and trich-loro-ethylene were investigated The results exhibited markedly the competition between photodimerization and photocycloaddition of 1, and showed that the yields of cycloaddition products increased with increasing polarity of the olefins. Strangely, photocycloaddition of 1 to olefins was found to proceed through the singlet excited state     

EVALUATION OF NEW BENZOPORPHYRIN DERIVATIVES WITH ENHANCED PDT EFFICACY*

Abstract— A first report on the biological evaluation of a series of isomerically pure benzoporphyrin derivatives ( cis- and frarcs-isomers) as methyl esters is described. In preliminary in vivo studies, the n- bexyl ether analogues of both cis- and trans -isomers of benzoporphyrin derivatives were found to be more active than the industrially prepared benzoporphyrin derivative, a mixture of monocarboxylic acids (BPDMA, Quadralogic Technologies, Vancouver). Further studies with 4-de-vinyl-4-(I-hexyloxyethyl) benzoporphyrin derivative showed that, like BPDMA, it had reduced residual skin phototoxicity compared in mice with Photofrin®. The uptake and clearance characteristics of BPDMA were also compared with the 4-(1-hexyloxyethyl)-derivative by in vivo reflection spectroscopy.     

Extraction with long-chain amines-II Extraction and colorimetric determination of chromate

Highly selective extraction of chromate from slightly acidic solutions (0.1-0.2M sulphuric acid) with a chloroform solution of trioctylamine (Alamine 336-S) or trioctylmethylammonium chloride Aliquat 336-S) is described. Many metals such as iron, nickel, cobalt, copper, alluminium, zinc, are not extracted, even if present in large concentrations. Coextraction of vanadium(V) and uranium(VI) is prevented by addition of sodium chloride. Traces of extracted molybdenum are scrubbed with ammonium oxalate. Final determination of chromium is based on measurement of the absorbance of the extract at 445-450 nm.     

Epilobium angustifolium L. as a Potential Herbal Component of Topical Products for Skin Care and Treatment—A Review

Epilobium angustifolium L. (EA) has been used as a topical agent since ancient times. There has been an increasing interest in applying EA as a raw material used topically in recent years. However, in the literature, there are not many reports on the comprehensive application of this plant to skin care and treatment. EA contains many valuable secondary metabolites, which determine antioxidant, anti-inflammatory, anti-aging, and antiproliferative activity effects. One of the most important active compounds found in EA is oenothein B (OeB), which increases the level of ROS and protects cells from oxidative damage. OeB also influences wound healing and reduces inflammation by strongly inhibiting hyaluronidase enzymes and inhibiting COX-1 and COX-2 cyclooxygenases. Other compounds that play a key role in the context of application to the skin are flavonoids, which inhibit collagenase and hyaluronidase enzymes, showing anti-aging and anti-inflammatory properties. While terpenes in EA play an important role in fighting bacterial skin infections, causing, among other things cell membrane, permeability increase as well as the modification of the lipid profiles and the alteration of the adhesion of the pathogen to the animal cells. The available scientific information on the biological potential of natural compounds can be the basis for the wider use of EA in skin care and treatment. The aim of the article is to review the existing literature on the dermocosmetic use of E. angustifolium.     

Effects of laser irradiation on optical properties of a-Se100−x Te x thin films

The effect of laser irradiation on the optical properties of thermally evaporated Se_100?x Te _x (x=8, 12, 16) chalcogenide thin films has been studied. The result shows that the irradiation causes a shift in the optical gap. The results have been analyzed on the basis of laser irradiation-induced defects in the film. The width of the tail of localized state in the band gap has been evaluated using the Urbach edge method. As the irradiation time increases, the values of the optical energy gap for all compositions decrease, while tail energy width increases. It is also observed that the optical energy gap decreases with increasing Te content in the alloy. These changes are a consequence of an increment in disorder produced by laser irradiation in the amorphous structure of thin film.     

Site symmetry and crystal field splittings of Ce 3+ in LiLuF 4 and LiSr 0.8 Ca 0.2 AlF 6

Electron paramagnetic resonance (EPR) spectra of Ce 3+ in LiLuF 4 (LLF) and LiSr 0.8 Ca 0.2 AlF 6 (LSCAF) observed at low temperatures (<20 v K) show that the Ce 3+ centers have tetragonal and pseudo-trigonal symmetry with ( g , g )=(2.751, 1.467) and (2.14, 0.80), respectively. The EPR lines of Ce 3+ in LSCAF are inhomogeneously broadened by different Ce 3+ configurations which correspond to the random occupation of the second nearest neighbor cation sites by Ca 2+ and Sr 2+ and/or charge compensators. These EPR results indicate that the Ce 3+ centers in LLF and LSCAF are associated with substitution of Ce 3+ for Lu 3+ with eight-fold coordination and Sr 2+ /Ca 2+ with six-fold coordination, respectively. Fourier transform infrared absorption has been used to measure transitions between the 2 F 5/2 ground state and the 2 F 7/2 multiplet of Ce 3+ in LLF at 10 v K. The optical absorption and luminescence of Ce 3+ :LLF and Ce 3+ :LSCAF in the UV range are strongly polarized. The energy levels and polarization dependence of the optical transitions can be accounted for in terms of the crystal field potential experienced by the Ce 3+ ions under the action of the different point group symmetries.     

Utilization of the hydroxyalkylation reaction to prepare bis(benzocrown ethers)

The hydroxyalkylation reaction has been used to condense benzocrown ethers with various aldehydes and ketones. The condensation reactions are catalyzed by triflic or sulfuric acid. The products from the reactions are bis(benzocrown ethers) and they are formed in good yields (42-98%, 13 examples).