Optics of metal surfaces by reflectance of p-polarized light

A new expression is derived for the differential reflectance from an arbitrary metal surface, with chemisorbed impurities, using $\text{p}$-polarized radiation. The use of the result, which depends entirely on the dielectric response tensor of the system, to study experimental Surface Reflectance data is discussed.     

Furanverbindungen, 7. Mitt.: Synthese linear anellierter Furoxanthone

Zusammenfassung Die bemerkenswerte photodynamische Wirkung linear anellierter Furobenzopyrone (Psoralen, Methylpsoralen und Khellin) wird zum Anlaß für die Synthese von Xanthonanalogen des 8-Methylpsoralens, wie z. B. des 2,11-Dimethyl- oder des 2,7,11-Trimethyl-5-oxo-5H-furo[3,2-b]xanthens genommen.

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The appreciable photodynamic activity of linear furanobenzopyrones (psoralen, methyl psoralen and khellin) is discussed. The synthesis of xanthone analogues of 8-methylpsoralen viz. 2,11-dimethyl- or 2,7,11-trimethyl-5-oxo-5H-furo[3,2-b]xanthenes is recorded.

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Teilveröffentlichung der vonY. S. Agasimundin eingereichten Dissertation zur Erlangung eines Dr. phil. der Karnatak University.     

Furano compounds—part XIII

The Synthesis of 3, 5′-dimethyl- and 3,4′-dimethyl-furaro (2′, 3′:1, 2)?6, 7-benzoxanthones (III and IV) is described.     

On the relation of Cesàro summability to generalized (F α, q) summability

Standard special cases of the sequence-to-functionF (a, q)-transform of Meir4 admit of a more general, essentially more refined, characterization as theF ^k (a, q)-transform of the sequel, adapted from one of Faulhaber’s.1 The theorem proved,viz., that (F _{a, q} ^k) summability for sequences, corresponding to the latter transform, includes Cesàro summability of a positive integer order with a certain rapidity, applies to the standard special cases of (F _{α, q}) and (F _{a, q} ^k) summabilities which are, in famiiar notation, summabilities(E _p), (T _α), (S _β), (V _a) and (B _{α, γ}) whose further special case (B_{1, 1}) is Borel summability. The special cases of (V_1/2) and Borel summabilities go back to Hyslop.3     

Synthesis of phenyl substituted furanobenzopyrones

Proceedings - Mathematical Sciences - The syntheses of 1, 2-diphenyl-6-methyl-8-oxo-8H-furo-[2, 3-h] (1) benzopyran, 2, 3-diphenyl-5-methyl-7-oxo-7H-furo [2, 3-g] (1) benzopyran and 1,...     

Optical spectroscopy of hydrophobic sunscreen molecules adsorbed to dielectric nanospheres

Fluorescence and absorption spectra of hydrophobic sunscreens, weakly fluorescent octyl methoxycinnamate, moderately fluorescent octyl salicylate and highly fluorescent 2-ethylhexyl-4-(dimethylamino)benzoate (padimate O) adsorbed to dielectric microspheres in aqueous suspension, have been compared with spectra in organic solution. The fluorescence of adsorbed salicylate and padimate is enhanced compared with fluorescence in methanol: about a factor of 6 and 30 in terms of fluorescence yield per molecule of salicylate and padimate, respectively. Cinnamate, which has a low fluorescence yield, does not show a comparable fluorescence enhancement. The fluorescence amplification is independent of sphere diameter from 30 to 1500 nm, at least for salicylate. The enhancement, as well as the location of absorption spectral peaks, is consistent with a low-dielectric constant environment of the molecules, in spite of the presumed location near the interface between polystyrene (epsilon = 2.4-3.8) and water (epsilon = 78). The adsorbed state of these sunscreens represents a proposed improved in vitro model for the environment of sunscreens in vivo, as well as a general model for chromophores in heterogeneous environments.     

Responsive hydrogels from the intramolecular folding and self-assembly of a designed peptide

A general peptide design is presented that links the pH-dependent intramolecular folding of beta-hairpin peptides to their propensity to self-assemble, affording hydrogels rich in beta-sheet. Chemical responsiveness has been specifically engineered into the material by linking intramolecular folding to changes in solution pH, and mechanical responsiveness, by linking hydrogelation to self-assembly. Circular dichroic and infrared spectroscopies show that at low pH individual peptides are unstructured, affording a low-viscosity aqueous solution. Under basic conditions, intramolecular folding takes place, affording amphiphilic beta-hairpins that intermolecularly self-assemble. Rheology shows that the resulting hydrogel is rigid but is shear-thinning. However, quick mechanical strength recovery after cessation of shear is observed due to the inherent self-assembled nature of the scaffold. Characterization of the gelation process, from the molecular level up through the macroscopic properties of the material, suggests that by linking the intramolecular folding of small designed peptides to their ability to self-assemble, responsive materials can be prepared. Cryo-transmission electron and laser scanning confocal microscopies reveal a water-filled porous scaffold on both the nano- and microscale. The environmental responsiveness, morphology, and peptidic nature make this hydrogel a possible material candidate for biomedical and engineering technology.     

Extending the Gibbs tangent plane semicontinuous mixtures

The computation of phase equilibrium for semicontinuous mixtures results in a set of algebraic-functional equations which are commonly solved using the pseudocomponent approach or reducing the order of the functional equations to a set of algebraic equations by means of a Petrov–Galerkin approach. Both approaches can be taken as particular cases of the method of weighed residuals. In order to perform stability analysis of phase equilibrium, the classical tangent plane criterion algorithms can be used as the first approach. There is a lack of functional formulation for the stability criterion in the literature. In some special cases, such as mixtures containing continuous families of heavy-components, a new formulation of the tangent plane criterion is required. In the present work, functional extensions of the Gibbs tangent plane criterion are described. The use of the proposed criteria was exemplified by calculating solid–liquid phase equilibrium of a crude oil containing asphaltenes on titration with a precipitating agent, n-pentane.     

Copper(II), nickel(II), cobalt(II) and oxovanadium(IV) complexes of substituted β-hydroxyiminoanilides

Complexes of the general formula, ML₂ [M = Cu^II, Ni^II, Co^II and OV^IV; L = 1,2,3,5,6,7,8,8a-octahydro-3-hydroxyimino-N-(4-X-phenyl)-l-phenyl-5-(phenylmethylene)-2-naphthalenecarboxamide (X = H, Me, OMe, Cl)] have been prepared and characterized on the basis of elemental analysis, magnetic moments and i.r., e.p.r. and electronic spectra. These metal complexes contain the N₄ chromophore with the ligand coordinating through nitrogens of the azomethine and deprotonated anilide functions. C.v. measurements indicate that the copper(II) complexes are quasi-reversible in acetonitrile solution. Square planar and square pyramidal structures are assigned respectively to the copper(II) and oxovanadium(IV) complexes, whereas tetrahedral geometry is assigned to the nickel(II) and cobalt(II) complexes. Deprotonated anilide nitrogen is involved in coordination and the presence of an electron-donating group para to the anilide function decreases the ΔE values of the d–d transitions while the value is found to increase when electron-withdrawing groups are substituted. Line spacing in the e.p.r. spectra of the copper(II) and oxovanadium(IV) complexes increases when methyl group is para to the anilide group, and decreases when this group is replaced by methoxy or chloro. The ν(C–N) of the anilide group and the ν(C-N) of the azomethine function of the oxime metal complexes are metal-sensitive and the blue shift for the above stretching frequencies follows the order: copper(II) > oxovanadium(IV) > nickel(II) ≈ cobalt(II). This revised version was published online in June 2006 with corrections to the Cover Date.     

Pendeo-epitaxial growth of gallium nitride on silicon substrates

Pendeo-epitaxy (PE)¹ from raised, [0001] oriented GaN stripes covered with silicon nitride masks has been employed for the growth of coalesced films of GaN(0001) with markedly reduced densities of line and planar defects on Si(111)-based substrates. Each substrate contained previously deposited 3C-SiC(111) and AlN(0001) transition layers and a GaN seed layer from which the stripes were etched. The 3C-SiC transition layer eliminated chemical reactions between the Si and the NH₃ and the Ga metal from the decomposition of triethylgallium. The 3C-SiC and the GaN seed layers, each 0.5 μm thick, were also used to minimize the cracking and warping of the GaN/SiC/silicon assembly caused primarily by the stresses generated on cooling due to the mismatches in the coefficients of thermal expansion. Tilting in the coalesced GaN epilayers of 0.2° was confined to areas of lateral overgrowth over the masks; no tilting was observed in the material suspended above the trenches. The strong, low-temperature PL band-edge peak at 3.456 eV with a FWHM of 17 meV was comparable to that observed in PE GaN films grown on AlN/6H-SiC(0001) substrates.