Structure analyses of menthone- and isomenthone-tosylhydrazones,C17H26N2O2S

The crystal and molecular structures of two configurational isomers of the title compound have been determined by three-dimensional, single-crystal X-ray diffractometry. Both (2S,5R)- and (2R,5R)-4-methylbenzenesulfonic acid-[5-methyl-2-(1-methylethyl)cyclohexylidene] hydrazide (hereafter referred to as menthone- and isomenthone-tosylhydrazone, orI andII, respectively) crystallize in the orthorhombic space groupP2₁2₁2₁ (No. 19, D ₂ ⁴ ) with four formula units per cell anda=5.209(1),b=17.501(1),c=20.154(1)Å anda=5.281(1),b=17.300(1),c=20.422(1)Å, respectively. The phase problems were solved by direct methods and the respective final full-matrix least-squares refinements of 1767 and 3010 unique reflections converged toR=0.046 and 0.052. In both structures, the toluenesulfonamide group occupies a positionanti to the more substituted side of the cyclohexyl ring, the C(16)-C(11)-N(2) angles are significantly wider than 120°, and each sulfonamide nitrogen (1) atom appears to exhibit a distorted trigonal pyramidal geometry. The structures differ in the positioning of the isopropyl and methyl substituents on the cyclohexane ring, with thetrans isomerI having both groups equatorial, while thecis isomerII exhibits an axial isopropyl group. The molecules in the crystal lattice are held together by van der Waals forces. X-ray powder diffraction, conoscopic, infrared, and¹H and¹³C NMR analyses have been performed.(2S,5R)- and (2R,5R)-4-Methylbenzenesulfonic acid-[5-methyl-2-(1-methylethyl)cyclohexylidene]hydrazide.     

A theoretical and experimental study of the near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectra (XPS) of nucleobases: Thymine and adenine

The core level electron excitation and ionization spectra of thymine and adenine have been investigated by photoabsorption and photoemission spectroscopy, and the results interpreted by means of ab initio calculations using the second-order algebraic–diagrammatic construction (ADC(2)) method for the polarization propagator and the fourth-order ADC method (ADC(4)) for the one-particle Green’s function. The photoabsorption spectra are dominated by transitions from core levels to unoccupied π states, but also show clear structures due to Rydberg transitions. The calculated spectra are in good agreement with the experimental results, and many of the observed structures are assigned.     

The adsorption of adenine on mineral surfaces: Iron pyrite and silicon dioxide

The adsorption of the nucleobase adenine on surfaces of the minerals iron pyrite and silica has been studied by photoemission and soft X-ray photoabsorption spectroscopy. Pyrite samples were prepared by fracture under nitrogen followed by transfer to ultrahigh vacuum, or by cleavage in vacuum. By comparing data with multilayer spectra, adenine was found to chemisorb on pyrite, with small changes in the valence band spectrum, and stronger changes in the NEXAFS spectrum. The molecules were bonded with the molecular plane at a steep angle to the surface plane. On silica the molecule was found to adsorb at a reduced angle to the surface. The C and N 1s photoemission spectra on this surface suggest chemisorption, although the nitrogen NEXAFS spectra are similar to multilayer spectra.     

Further translation planes of order 19<Superscript>2</Superscript> admitting SL(2,5), obtained by nest replacement

We construct three translation planes of order 19² admitting SL(2,5), obtained by replacement of 24-nests of reguli in PG(3,19).     

Dissipative enhancement of the response of a bistable noisy oscillator to external driving

A study of the linear response susceptibility of a noisy bistable oscillator as a function of damping is carried out using the method of moments. It is found that this dependence, counterintuitively, has a nonmonotonic character and shows a maximum when the driving frequency is comparable to the thermal interwell hopping rate. The possible mechanism responsible for the occurrence of such dissipative sensitivity enhancement is proposed.     

Metastable (1 × 2) and (1 × 3) reconstructions of Pd(110)

By adsorption and subsequent reduction of oxygen on Pd(110), metastable (1 × 2) and (1 × 3) reconstructed surfaces have been produced. Oxygen was not present after the reduction but a small amount of residual hydrogen (< 0.15 monolayers) remained. However this is not the origin of the reconstruction as adsorption of this amount of hydrogen on the clean surface did not cause reconstruction. The structures were stable up to ˜ 370 K, and at higher temperatures they reverted to (1 × 1). These results are compared with Rh(110) where similar reconstructions have been found.     

Synchotron radiation photoemission study of adsorbate-induced 3d core level shifts of Pd(110)

The surface core level shifts of Pd(110) and oxygen and CO covered Pd(110) have been measured using synchrotron radiation. The results are consistent with values predicted using a Born-Haber cycle, confirming the usefulness of this approach. The largest shift occurs for the CO covered surface, indicating that initial state charge transfer does not dominate the shifts.     

Singularité de la mesure harmonique sur le bord d'un groupe hyperbolique

This Note deals with the dimension of the harmonic measure ν associated with a random walk on the isometry group of a Gromov hyperbolic space. We establish a link of the form $\dim \nu ?h/l$ between the dimension of the harmonic measure, the asymptotic entropy h of the random walk and its rate of escape l. Then we use this inequality to show that the dimension of this measure can be made arbitrarily small and deduce a result on the type of the harmonic measure. To cite this article: V. Le Prince, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Evaluation of the risk of noise-induced hearing loss among unscreened male industrial workers

Variability in background risk and distribution of various risk factors for hearing loss may explain some of the diversity in excess risk of noise-induced hearing loss (NIHL). This paper examines the impact of various risk factors on excess risk estimates of NIHL using data from the 1968-1972 NIOSH Occupational Noise and Hearing Survey (ONHS). Previous analyses of a subset of these data focused on 1172 highly "screened" workers. In the current analysis, an additional 894 white males (609 noise-exposed and 285 controls), who were excluded for various reasons (i.e., nonoccupational noise exposure, otologic or medical conditions affecting hearing, prior occupational noise exposure) have been added 2066) to assess excess risk of noise-induced material impairment in an unscreened population. Data are analyzed by age, duration of exposure, and sound level (8-h TWA) for four different definitions of noise-induced hearing impairment, defined as the binaural pure-tone average (PTA) hearing threshold level greater than 25 dB for the following frequencies: (a) 1-4 kHz (PTA1234), (b) 1-3 kHz (PTA123), (c) 0.5, 1, and 2 kHz (PTA512), and (d) 3, 4, and 6 kHz (PTA346). Results indicate that populations with higher background risks of hearing loss may show lower excess risks attributable to noise relative to highly screened populations. Estimates of lifetime excess risk of hearing impairment were found to be significantly different between screened and unscreened population for noise levels greater than 90 dBA. Predicted age-related risk of material hearing impairment in the ONHS unscreened population was similar to that predicted from Annex B and C of ANSI S3.44 for ages less than 60 years. Results underscore the importance of understanding differential risk patterns for hearing loss and the use of appropriate reference (control) populations when evaluating risk of noise-induced hearing impairment among contemporary industrial populations.     

Simultaneous multiple volume (SMV) acquisition algorithm for real-time navigator gating

Navigator gating techniques can effectively reduce motion effects in MRI by accepting data only when the object is in a small range of positions at the cost of significantly prolonging scan time. A simultaneous multiple volume (SMV) algorithm is reported here that can substantially increase the scan efficiency while maintaining the effectiveness of motion suppression. This is achieved by acquiring different image volumes at different motion states. Initial experiments demonstrate that SMV can significantly increase the scan efficiency of navigator MRI.