Effect of Alkyl Side Chain on the Conformational Properties of Polysulfones with Quaternary Groups

Modification of intrinsic viscosity, temperature coefficient, and preferential adsorption coefficient of polysulfones with different alkyl side groups in N,N-dimethylformamide/methanol and N,N-dimethylformamide/water was investigated at different compositions and temperatures. The specific interactions, such as hydrogen bonding and polyelectrolyte effect induced by an enhanced dissociation of the ionizable groups, determine both the modification of the solvation power of the polymer coil and the difference in the composition of the mixed solvent inside and outside the coil.     

Combined prostate diffusion tensor imaging and dynamic contrast enhanced MRI at 3T — quantitative correlation with biopsy

The purpose of this work was to compare diagnostic accuracy of Diffusion Tensor Imaging (DTI), dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) and their combination in diagnosing prostate cancer. Twenty-five patients with clinical suspicion of prostate cancer underwent MRI, prior to transrectal ultrasound-guided biopsies. MRI data were correlated to biopsy results. Logistic regression models were constructed for the DTI parameters, DCE MRI parameters, and their combination. The areas under the receiver operator characteristic curves (AUC) were compared between the models. The nonparametric Wilcoxon signed rank test was used for statistical analysis. The sensitivity and specificity values were respectively 81% (74–87%) and 85% (79–90%) for DTI and 63% (55–70%) and 90% (85–94%) for DCE. The combination “DTI or DCE MRI” had 100% (97–100%) sensitivity and 77% (69–83%) specificity, while “DTI and DCE MRI” had 44% (37–52%) sensitivity and 98% (94–100%) specificity. The AUC for DTI+DCE parameters was significantly higher than that for either DTI (0.96 vs. 0.92, P=.0143) or DCE MRI parameters (0.96 vs. 0.87, P=.00187) alone. In conclusion, the combination of DTI and DCE MRI has significantly better accuracy in prostate cancer diagnosis than either technique alone.     

Brain oscillatory activity during motor imagery in EEG-fMRI coregistration

The purpose of the present work was to investigate the correlation between topographical changes in brain oscillatory activity and the blood oxygenation level-dependent (BOLD) signal during a motor imagery (MI) task using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) coregistration.     

Optical resonances in one-dimensional dielectric nanorod arrays: field-induced fluorescence enhancement

Arrays of transparent dielectric nanorods are shown to produce very large local field enhancements at specific resonant conditions. These structures would lead to enhancement of molecular fluorescence signals without quenching. The resonant angular width and field enhancements are analytically derived as a function of wavelength, grating period, rod radius, and dielectric constant.     

Cosmological Relativity: A New Theory ofCosmology1

A new general-relativistic theory of cosmology, the dynamical variables of whichare those of Hubble's, namely distances and redshifts, is presented. The theorydescribes the universe as having a three-phase evolution with a deceleratingexpansion followed by a constant and an accelerating expansion, and it predictsthat the universe is now in the latter phase. The theory is actually a generalizationof Hubble's law taking gravity into account by means of Einstein's theory ofgeneral relativity. The equations obtained for the universe expansion are elegantand very simple. It is shown, assuming ₀ = 0.24, that the time at which theuniverse goes over from a decelerating to an accelerating expansion, i.e., theconstant expansion phase, occurs at 0.03 from the big bang, where is theHubble time in vacuum. Also, at that time the cosmic radiation temperature was11 K. Recent observations of distant supernovae imply, in defiance of expectations,that the universe's growth is accelerating, contrary to what has always beenassumed, that the expansion is slowing down due to gravity. Our theory confirmsthese recent experimental results by showing that the universe now is definitelyin a stage of accelerating expansion.     

On stochastic spatial patterns and neuronal polarity

To investigate the statistical behavior in the sizes of finite clusters for percolation, cluster size distribution n _s (p) for site and bond percolations at different lattices and dimensions was simulated using a modified algorithm. An equation to approximate the finite cluster size distribution n _s (p) was obtained and expressed as: log?(n _s (p)) = as ? b log?s + c. Based on the analysis of simulation data, we found that the equation is valid for p from 0 to 1 on site and for the bond percolation of two-dimensional (2D) and three-dimensional (3D) lattices. Furthermore, the relationship between the coefficients of the equation and the occupied ratio p was studied using the finite-size scaling method. When \(x = D(p - p_c )L^{y_t }\) , p < p _c , and D was a nonuniversal metric factor. a was found to be related only to p, and the a-x curves of different lattices were nearly overlapped; b was related to the dimensions and p, and the scaled data of the b of all lattices with the same dimension tended to fall on the same curves. Unlike a and b, c apparently had a quadratic relation with x in 2D lattices and linear relation with x in 3D lattices. The results of this paper could significantly reduce the amount of tasks required to obtain numerical data of on the cluster size distribution for p from 0 to p _c .     

Diode laser spectroscopy of the ν7a band of fluorobenzene

The diode laser absorption infrared spectrum of fluorobenzene has been recorded near 1230 cm⁻¹ after cooling the molecules in a supersonic pulsed jet. Spectral lines have been assigned to the ν_7a fundamental band. Transitions of J between 32 and 49 have been recorded, that show characteristic line groupings in the P branch. Analysis of the spectrum gives the vibrational band origin and rotational and centrifugal distortion constants of the molecule in the ν_7a = 1 state.     

Building Wavelets on ]0,1[ at Large Scales

We present a new approach to the construction of orthonormal wavelets on the interval which allows to overcome the non interacting boundaries restriction of existing constructions, and therefore to construct wavelets for U0; 1T also at large scales in such a way that, in the range of validity of the existing constructions, the two approaches give the same result.     

Symmetric incidence groupoids

In [7] point-reflection geometries were studied which can be derived from commutative kinematic spaces without involutory elements. But the class of point-reflection geometries is larger. For example, elliptic planes with their reflections cannot be derived from commutative kinematic spaces. Here we investigate a larger class of reflection geometries.This paper was sponsored by Vigoni Program 1999.