Yield oscillations of inelastic processes under channeling conditions at angles greater than the critical angle

A quantum-mechanical analysis of the angular dependence of the yield of inelastic processes in thin crystals under planar-channeling conditions reveals strong intensity oscillations at a given depth for incidence angles ψ > ψ_c. The dependence of the period of these oscillations on the distance z from the surface of incidence is investigated, and pronounced oscillations of the yield versus z are shown to occur simultaneously at fixed ψ.     

Line-narrowed laser-absorption spectra induced by decaying adiabatic pulses

The narrowing of absorption lineshapes by the use of decaying excitation is discussed. Adiabatic pulse rise times are shown to apodise ringing encountered in transient lineshapes.     

Measurement of B(D+-->K(*0)l(+)nu(l))

Using 13.53 fb(-1) of CLEO data, we have measured the ratios of the branching fractions R(+)(e),R(+)(mu) and the combined branching fraction ratio R(+)(l), defined by R(+)(l)=[B(D+-->K(*0)l(+)nu(l))]/[B(D+-->K-pi(+)pi(+))]. We find R(+)(e)=0.74+/-0.04+/-0.05, R(+)(mu)=0.72+/-0.10+/-0.05, and R(+)(l)=0.74+/-0.04+/-0.05, where the first and second errors are statistical and systematic, respectively. The known branching fraction B(D+-->K-pi(+)pi(+)) leads to B(D+-->K(*0)e(+)nu(e))=(6.7+/-0.4+/-0.5+/-0.4)%, B(D+-->K(*0)mu(+)nu(mu))=(6.5+/-0.9+/-0.5+/-0.4)%, and B(D+-->K(*0)l(+)nu(l))=(6.7+/-0.4+/-0.5+/-0.4)%, where the third error is due to the uncertainty in B(D+-->K-pi(+)pi(+)).     

Photochemical and Photobiological Studies of a Furonaphthopyranone as a Benzo-spaced Psoralen Analog in Cell-free and Cellular DNA

Abstract— Photobiological activities of the benzo-spaced psoralen analog furonaphthopyranone 3 have been investigated in cell-free and cellular DNA. The molecular geometry parameters of 3 suggest that it should not form interstrand crosslinks with DNA. With cell-free DNA no evidence for crosslinking but also not for monoadduct formation was obtained; rather, the unnatural furocoumarin 3 induces oxidative DNA modifications under near-UVA irradiation. The enzymatic assay of the photosensitized damage in cell-free PM2 DNA revealed the significant formation of lesions sensitive to formamidopyrimidine DNA glyco-sylase (Fpg protein). In the photooxidation of calf thymus DNA by the furonaphthopyranone 3, 0.29±0.02% 8-oxo-7,8-dihydroguanine (8-oxoGua) was observed. With 2'-deoxyguanosine (dGuo), the guanidine-releasing photooxidation products oxazolone and oxoimidazolidine were formed predominately, while 8-oxodGuo and 4-HO-8-oxodGuo were obtained in minor amounts. The lack of a significant D₂O effect in the photooxidation of DNA and dGuo reveals that singlet oxygen (type II process) plays a minor role; control experiments with tert -butanol and mannitol confirm the absence of hydroxyl radicals as oxidizing species. The furonaphthopyranone 3 (E_red= -1.93±0.03V) should act in its singlet-excited state as electron acceptor for the photooxidation of dGuo (δG_ET ca – kcal/mol), which corroborates photoinduced electron transfer (type I) as a major DNA-oxidizing mechanism. A comet assay in Chinese hamster ovary (CHO) AS52 cells demonstrated that the psoralen analog 3 damages cellular DNA upon near-UVA irradiation; however, no photosensitized mutagenicity was observed in CHO AS52 cell cultures     

Synthesis of new ligands for transition metal complexes: menthyl- and neomenthyl-cyclopentadienes

Syntheses of (?)-menthylcyclopentadiene (MCp) and (+)-neomenthyl cyclopentadiene (NMCp) from (?)-menthol are described. These chiral ligands have been used to prepare (η⁵-MCp)₂TiCl₂, (η⁵-NMCp)₂, TiCl₂, (η⁵-MCp)₂ZrCl₂, (η⁵-NMCp)₂ZrCl₂, (η⁵-Cp)(η⁵-MCp)TiCl₂ and (η⁵-Cp)(η⁵-NMCp)TiCl₂. The structure and absolute configuration of (η⁵-Cp)(η⁵-MCp)TiCl₂ has been established by X-ray analysis.     

New Results of Studying the Lower Ionosphere by the Method of Resonance Scattering of Radio Waves from Artificial Periodic Inhomogeneities

We present the results of studying the lower ionosphere in 2000–2004 at the “Sura” heating facility by the method of resonance scattering of radio waves from artificial periodic inhomogeneities of the ionospheric plasma. Experimental data on a study of the sunset–sunrise phenomena in the ionospheric D region and the possibility of determining the concentrations of atomic oxygen and excited molecular oxygen are discussed. The results of studying the sporadic layers of ionization are presented and the method for a study of ion composition of the E_s layer is discussed. Data of the August 2004 experiments on a study of the influence of heating the ionosphere on the E_s layer and characteristics of artificial periodic inhomogeneities are presented. Prospects for further research are discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 757–771, September 2005.