Crystal and molecular structure of 1,4-diphenyl-2,3-dioxabicyclo[2,2,1] heptane,C17H16O2

The crystal structure of 1,4-diphenyl-2,3-dioxabicyclo [2,2,1] heptane has been determined from three-dimensional counter data and refined by full-matrix least-squares procedures. This endoperoxide compound crystallizes from ethanol in space groupP2₁/c with cell constantsa = 11.797(1),b = 9.051(8),c = 12.472(1) Å, = 93.78(1) °,Z = 4,D _x = 1.261, andD _m = 1.274 g cm^–3. The final residual for 2238 observed reflections is 0.063. The molecular structure possesses both an unusually long peroxide bond, 1.501(2) Å, and adjoining C-O bonds, 1.459(2) Å. This observation confirms a previously made conjecture that the forcedcis coplanarity of the C-O-O-C torsion angle would permit repulsive antisymmetric vicinal orbital interactions between the oxygen centers, destabilizing the peroxide bond relative to that normally encountered as the commonly observedgauche conformation.     

A non-destructive analysis of the influence of sputter-etching on the magnetic surface properties of manganese zinc ferrite (100) surfaces using ellipsometry and the polar magneto-optical Kerr effect

Ellipsometry and the polar magneto-optical Kerr effect have been used in the photon energy range 0.65 eV?hv?5.4 eV to study sputter-etched manganese zinc ferrite (100) surfaces. With an annealed sample as a reference, a stratified media calculation indicates the presence of a paramagnetic surface layer of 8–40 nm thickness, depending on sputter parameters. Conversion electron Mössbauer spectroscopy and Rutherford backscattering spectroscopy fully confirmed these results.     

Synthesis and molecular and electronic structure of dibenz(b,f)-1,4-oxazepine

Russian National Scientific-Research Institute of Organic Chemistry and Technology. Translated fromZhurnal Struktumoi Khimii, Vol. 36, No. 1, pp. 197–201, January–February, 1995.     

Quantum mechanical calculations of tryptophan and comparison with conformations in native proteins

We report a detailed analysis of the potential energy surface of N-acetyl-l-tryptophan-N-methylamide, (NATMA) both in the gas phase and in solution. The minima are identified using the density-functional-theory (DFT) with the 6-31g(d) basis set. The full potential energy surface in terms of torsional angles is spanned starting from various initial configurations. We were able to locate 77 distinct L-minima. The calculated energy maps correspond to the intrinsic conformational propensities of the individual NATMA molecule. We show that these conformations are essentially similar to the conformations of tryptophan in native proteins. For this reason, we compare the results of DFT calculations in the gas and solution phases with native state conformations of tryptophan obtained from a protein library. In native proteins, tryptophan conformations have strong preferences for the beta sheet, right-handed helix, tight turn, and bridge structures. The conformations calculated by DFT, the solution-phase results in particular, for the single tryptophan residue are in agreement with native state values obtained from the Protein Data Bank.     

Picosecond Soliton Pulse Generation with a Zinc Phthalocyanine Thin-Film Saturable Absorber Via Mode Locking in an Erbium-Doped Fiber Laser Cavity

Journal of Russian Laser Research - In this paper, we employ a Zinc Phthalocyanine (ZnPc) organic material to construct a saturable absorber (SA) that is used in a laser cavity to generate...     

Differential Laser‐Induced Perturbation Spectroscopy for Analysis of Mixtures of the Fluorophores l‐Phenylalanine,l‐Tyrosine and l‐Tryptophan Using a Fluorescence Probe

Quantitative detection of common endogenous fluorophores is accomplished using differential laser‐induced perturbation spectroscopy (DLIPS) with a 193‐nm UV fluorescence probe and various UV perturbation wavelengths. In this study, DLIPS is explored as an alternative to traditional fluorescence spectroscopy alone, with a goal of exploring natural fluorophores pursuant to biological samples and tissue analysis. To this end, aromatic amino acids, namely, l ‐phenylalanine, l ‐tyrosine and l ‐tryptophan are mixed with differing mass ratios and then classified with various DLIPS schemes. Classification with a traditional fluorescence probe is used as a benchmark. The results show a 20% improvement in classification performance of the DLIPS method over the traditional fluorescence method using partial least squares (PLS) analysis. Additional multivariate analyses are explored, and the relevant photochemistry is elucidated in the context of perturbation wavelengths. We conclude that DLIPS is a promising biosensing approach with potential for in vivo analysis given the current findings with fluorophores relevant to biological tissues.     

Conley conjecture and local Floer homology

In this paper we connect algebraic properties of the pair-of-pants product in local Floer homology and Hamiltonian dynamics. We show that for an isolated periodic orbit, the product is non-uniformly nilpotent and use this fact to give a simple proof of the Conley conjecture for closed manifolds with aspherical symplectic form. More precisely, we prove that on a closed symplectic manifold, the mean action spectrum of a Hamiltonian diffeomorphism with isolated periodic orbits is infinite.     

Measurement of the refractive index and optical absorption spectra of epitaxial bismuth substituted yttrium iron garnet films at uv to near-ir wavelengths

Refractive-index and optical-absorption spectra of Bi-substituted yttrium iron garnet films, epitaxially grown by liquid-phase epitaxy, have been measured in the spectral regime 0.26 m1.9 m by thin-film interference for 0.52 m and by ellipsometry for0.52 m. The Y_3–x–y Bi _x Pb _y Fe_5–z Pt _z O₁₂ films contain bismuth in the range Ox 1.42, lead in the range 0.01 y0.08 and platinum in the range 0.005<=z0.03. There is satisfactory coincidence between the results from ellipsometry and thin-film interference in the overlapping wavelength region. The materials investigated are the same as reported earlier from this laboratory in ter mof their magnetic and magnetooptic properties.     

Trace element changes during hibernation of Drosophila melanogaster by WDXRF analyses at chilling temperature

Fruit flies (Drosophila melanogaster) were exposed to low temperature (4 °C, 3d), after controlled acclimation (15 °C, 1d) and passed to artificial hibernation. The concentrations of elements in almost 1000 mature flies were measured by Wavelength-Dispersive X-ray Fluorescence (WDXRF) spectrometry. Concentration changes of Zn, K, S, Ca (33.5%, 11.2%, 10.3% and 7.5%, respectively) and especially Cr and Mn (99.90 and 99.60) were observed. Concentrations of Cr, Zn, S and Ca increased significantly, but concentrations of Mn and K decreased in with comparison to the control group.