Optimal mappings with minimum number of connected components in tree-to-tree comparison problems

In this paper we consider the problem of finding a minimum cost mapping between two unordered trees which induces a graph with a minimum number of connected components. The proposed algorithm is based on the generalization of an algorithm for computing an edit distance between trees, and it solves the stated problem in sequential time precisely in O(|T₁|×|T₂|×(degT₁+degT₂)×log₂(degT₁+degT₂)).     

Statistics of travel time and intensity of two first arrivals of short pulses backscattered by a rough 3D surface

The time history of a pulse backscattered by a rough surface contains information about the position of the surface and the properties of the scatterers. This information is utilized successfully in a number of remote sensing techniques ranging from echo sounding of the ocean bottom to medical ultrasonics and satellite altimetry. In the current paper, statistical properties of backscattered waves are considered in a geometrical optics approximation. The probing pulse duration is assumed to be sufficiently short so that signals backscattered in the vicinity of individual specular points on a rough surface do not overlap in time. Theoretical results previously obtained for a 2D problem [I. M. Fuks and O. A. Godin, 2005, Waves in Random and Complex Media, 14, 539-562; M. I. Charnotskii and I. M. Fuks, 2005, Waves in Random and Complex Media, 15, 451-467] are extended to wave scattering by 3D rough surfaces by following a mathematical approach developed in stochastic geometry. Predictions of an asymptotic theory are verified against results of Monte-Carlo simulations. Probability density functions of travel times and intensities of the first and second arrivals of the backscattered wave are quantified in terms of statistical moments of roughness assuming normal distribution of elevations. It is found that, as in the 2D case, the travel time and the intensity are strongly correlated; on average, the earlier a signal arrives, the smaller is its intensity.     

A Robust and Efficient Method for the Computation of Equilibrium Composition in Gaseous Mixtures

This paper presents in detail a robust, efficient and accurate methodology for the computation of equilibrium composition in gaseous mixtures. The methodology is founded on the concept of the chemical basis, which is defined and formalized using a powerful matricial approach. The method is specially designed to be general, thus providing basic thermodynamic data in several areas, such as combustion, plasma chemistry and, more generally speaking, computational fluid dynamics. The performance of the method is given in terms of CPU usage and the computed results are compared with those in the published literature. The method is shown to yield results of very high quality in terms of accuracy and smoothness.     

General access to iminosugar C-glycoside building blocks by means of cross-metathesis: a gateway to glycoconjugate mimetics

[reaction: see text] Cross-metathesis reactions of alpha-1-C-allyl-1-deoxynojirimycin derivatives 7a,b and various functionalized alkenes mediated by Grubbs's catalyst 3 are reported. The reactions showed reasonable to very good yields and excellent E/Z selectivity. This methodology allows the efficient and convergent synthesis of iminosugar C-glycosides with a great degree of structural diversity in the aglycone, opening the way to a variety of new glycoconjugate mimetics of biological interest.     

(Z)-3-p-tolylsulfinylacrylonitrile as a chiral dienophile: diels-alder reactions with furan and acyclic dienes

The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles.     

Narrow band quantitative and multivariate electroencephalogram analysis of peri-adolescent period

ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages.