Quantum mechanical study of molecules - Eigenvalues and eigenvectors of real symmetric matrices

Computer methods for calculating eigenvalue and eigenvectors of real symmetric matrices arising in problems of molecular quantum mechanic

Molecular collisions. 16: Comparison of GPS with classical trajectory calculations of rotational inelasticity for the Ar-N2 system

Comparison of generalized phase shift treatment with classical trajectory calculations of rotational inelasticity cross sections of Ar-N2 scatterin

Diffusion Tensor Imaging in a Large Longitudinal Series of Patients With Cervical Spondylotic Myelopathy Correlated With Long-Term Functional Outcome

BACKGROUND Fractional anisotropy (FA) of the high cervical cord correlates with upper limb function in acute cervical cord injury. We investigated the correlation between preoperative FA at the level of maximal compression and functional recovery in a group of patients after decompressive surgery for cervical spondylotic myelopathy (CSM). OBJECTIVE To determine the usefulness of FA as a biomarker for severity of CSM and as a prognostic biomarker for improvement after surgery. METHODS Patients received diffusion tensor imaging (DTI) scans preoperatively. FA values of the whole cord cross-section at the level of maximal compression and upper cervical cord (C1-2) were calculated. Functional status was measured using the modified Japanese Orthopedic Association (mJOA) scale preoperatively and at follow-up up to 2 yr. Regression analysis between FA and mJOA was performed. DTI at C4-7 was obtained in controls. RESULTS Forty-four CSM patients enrolled prior to decompression were compared with 24 controls. FA at the level of maximal compression correlated positively with preoperative mJOA score. Preoperative FA correlated inversely with recovery throughout the postoperative period. This was statistically significant at 12 mo postoperation and nearly so at 6 and 24 mo. Patients with preoperative FA0.55. CONCLUSION In the largest longitudinal study of this kind, FA promises a valid biomarker for severity of CSM and postoperative improvement. FA is an objective measure of function and could provide a basis for prognosis. FA is particularly useful if preoperative values are less than 0.55

Superdiffusion in Decoupled Continuous Time Random Walks

Continuous time random walk models with decoupled waiting time density are studied. When the spatial one jump probability density belongs to the Levy distribution type and the total time transition is exponential a generalized superdiffusive regime is established. This is verified by showing that the square width of the probability distribution (appropriately defined)grows as $t^{2/\gamma}$ with $0<\gamma\leq2$ when $t\to \infty$. An important connection of our results and those of Tsallis' nonextensive statistics is shown. The normalized q-expectation value of $x^2$ calculated with the corresponding probability distribution behaves exactly as $t^{2/\gamma}$ in the asymptotic limit.Comment: 9 pages (.tex file), 1 Postscript figures, uses revtex.st

Multiplicative noise: A mechanism leading to nonextensive statistical mechanics

A large variety of microscopic or mesoscopic models lead to generic results that accommodate naturally within Boltzmann-Gibbs statistical mechanics (based on $S_1\equiv -k \int du p(u) \ln p(u)$). Similarly, other classes of models point toward nonextensive statistical mechanics (based on $S_q \equiv k [1-\int du [p(u)]^q]/[q-1]$, where the value of the entropic index $q\in\Re$ depends on the specific model). We show here a family of models, with multiplicative noise, which belongs to the nonextensive class. More specifically, we consider Langevin equations of the type $\dot{u}=f(u)+g(u)\xi(t)+\eta(t)$, where $\xi(t)$ and $\eta(t)$ are independent zero-mean Gaussian white noises with respective amplitudes $M$ and $A$. This leads to the Fokker-Planck equation $\partial_t P(u,t) = -\partial_u[f(u) P(u,t)] + M\partial_u\{g(u)\partial_u[g(u)P(u,t)]\} + A\partial_{uu}P(u,t)$. Whenever the deterministic drift is proportional to the noise induced one, i.e., $f(u) =-\tau g(u) g'(u)$, the stationary solution is shown to be $P(u, \infty) \propto \bigl\{1-(1-q) \beta [g(u)]^2 \bigr\}^{\frac{1}{1-q}}$ (with $q \equiv \frac{\tau + 3M}{\tau+M}$ and $\beta=\frac{\tau+M}{2A}$). This distribution is precisely the one optimizing $S_q$ with the constraint $_q \equiv \{\int du [g(u)]^2[P(u)]^q \}/ \{\int du [P(u)]^q \}=$constant. We also introduce and discuss various characterizations of the width of the distributions.Comment: 3 PS figure

A common NYX mutation in Flemish patients with X linked CSNB

Aims: The Schubert-Bornschein type of complete congenital stationary night blindness (CSNB) is a genetically heterogeneous retinal disorder. It is characterised by a non-progressive disease course, often associated with high myopia and nystagmus. So far, mutations in two genes, NYX (nyctalopin) and GRM6 (metabotropic glutamate receptor 6) have been associated with this form of CSNB. The purpose of this study was to identify the genetic defect in affected male patients from Flemish families with complete CSNB. Methods: Probands with CSNB from three large Flemish families underwent ophthalmological examination. DNA was extracted from peripheral blood, and the coding region of NYX along with parts of the 5'UTR and 3'UTR and intronic regions covering the splice sites were PCR amplified and sequenced. Results: In the affected individuals of three Flemish families with the complete form of CSNB a novel NYX mutation, c.855delG was identified. This deletion is predicted to lead to a frameshift mutation, p. Asp286ThrfsX62 causing a premature stop codon. Conclusion: Previously, both single families with different mutations in NYX as well as different families with an identical mutation, suggestive of a founder mutation, have been described. The c.855delG deletion in NYX seems to be a common mutation associated with CSNB in the Flemish population from Belgium. Thus, we suggest performing diagnostic testing for CSNB in the Flemish population initially directed towards the identification of this mutation. Subsequent screening for other mutations in NYX or GRM6 could be performed as a second step

Bulk Mediated Surface Diffusion: Non Markovian Desorption with Finite First Moment

Here we address a fundamental issue in surface physics: the dynamics of adsorbed molecules. We study this problem when the particle's desorption is characterized by a non Markovian process, while the particle's adsorption and its motion in the bulk are governed by a Markovian dynamics. We study the diffusion of particles in a semi-infinite cubic lattice, and focus on the effective diffusion process at the interface $z = 1$. We calculate analytically the conditional probability to find the particle on the $z=1$ plane as well as the surface dispersion as functions of time. The comparison of these results with Monte Carlo simulations show an excellent agreement.Comment: 16 pages, 7 figs. European Physical Journal B (in press