Gaucher’s disease: Report of 11 cases with review of literature

Gaucher's disease (GD) is a lysosomal storage disorder due to  glucocerebrosidase deficiency; it's one of the rare genetic diseases for which therapy is now available. The purpose of this work is to study the epidemiological features of the disease and to highlight the diagnostic difficulties. We performed an 11-year retrospective study of 11 patients with GD followed-up in the department of paediatric hepatology  gastroenterology and nutrition of Rabat children's Hospital. We observed 11 patients with GD: 6 males and 5 females. Age at onset ranged from 3 months to 10 years with an average of 3.41 years. Mean age at diagnosis was 4 years (range 3months-14years).Parental consanguinity was noted in 85% cases. According to the clinical presentation, we classified our patients into: 9 cases of type 1 (81%) and two cases of type 2 (19%), none of the patients presented GD type 3. GD type 1: The age at diagnosis ranged from 2 years to 14 year with an average of 6 years. Main symptoms were:splenomegaly, hepatomegaly , pallor, haemorrhagic appearance (40%), bone pain (40%). The diagnosis was based on histology showing the Gaucher's cells in various tissues (100%). Enzymatic activity dosage  confirmed the diagnosis of GD for 4 patients (44.5%). The treatment wasalways symptomatic (analgesics, transfusion). A splenectomy was  performed in one case presenting with multiple splenic abscesses and hightransfusion requirements. None of the patients received a specific  treatment (substitutive enzymotherapy). The follow-up period ranged from 3 months to 6 years with an average follow-up of 4 years. We noticed  stability in 4 cases, 2 worsening cases with bone and spleen complications.Three patients were lost to follow-up. GD type 2: we observed two cases of GD type 2 diagnosed at 3 and 18 months. The visceral symptoms wereserious and the neurological features included seizures, hypertony, squint, physical developmental milestones delay. Both of them died. Gaucher'sdisease is not exceptional in Morocco. Type 1 is the most common type. We noted through this study some diagnostic difficulties as the diagnosiswas delayed and the enzymatic dosage was performed in only 42% of the cases as well as therapeutic difficulty with no prescription of the specifictreatment given the high cost of the enzyme

A Two-Dimensional Unsteady FDTD Model for Radon Transport with Multiple Sources Emanation from Soil Layers

A two-dimensional numerical model for radon transport based on the finite difference time domain (FDTD) method have been developed. The model is governed by the radon transport equation taking into account the mechanisms of diffusion, advection, and decay. The purpose of this model is to simulate the evolution of radon concentration which can be influenced by various parameters including depth and diffusion coefficient of the soil layer plus the velocity and initial concentration of radon. The obtained results were compared to an analytical solution to demonstrate the ability of this model for predicting the spatio-temporal evolution of radon transport in the porous media of soil layers

Activation gaps for the fractional quantum Hall effect: realistic treatment of transverse thickness

The activation gaps for fractional quantum Hall states at filling fractions $\nu=n/(2n+1)$ are computed for heterojunction, square quantum well, as well as parabolic quantum well geometries, using an interaction potential calculated from a self-consistent electronic structure calculation in the local density approximation. The finite thickness is estimated to make $\sim$30% correction to the gap in the heterojunction geometry for typical parameters, which accounts for roughly half of the discrepancy between the experiment and theoretical gaps computed for a pure two dimensional system. Certain model interactions are also considered. It is found that the activation energies behave qualitatively differently depending on whether the interaction is of longer or shorter range than the Coulomb interaction; there are indications that fractional Hall states close to the Fermi sea are destabilized for the latter.Comment: 32 pages, 13 figure

Microscopic origin of ferromagnetism in the trihalides CrCl3 and CrI3

Microscopic origin of the ferromagnetic (FM) exchange coupling in two Cr trihalides, CrCl3 and CrI3, their common aspects and differences, are investigated on the basis of density functional theory combined with realistic modeling approach for the analysis of interatomic exchange interactions. For these purposes, we perform a comparative study based on the pseudopotential and linear muffin-tin orbital methods by treating the effects of electron exchange and correlation in generalized gradient approximation (GGA) and local spin density approximation (LSDA), respectively. The results of ordinary band structure calculations are used in order to construct the minimal tight-binding type models describing the behavior of the magnetic Cr 3d and ligand p bands in the basis of localized Wannier functions, and evaluate the effective exchange coupling (Jeff) between two Cr sublattices employing four different technique: (i) brute force total energy calculations; (ii) the second-order Green's function perturbation theory for infinitesimal spin rotations of the LSDA (GGA) potential at the Cr sites; (iii) enforcement of the magnetic force theorem in order to treat both Cr and ligand spins on a localized footing; and (iv) constrained total-energy calculations with an external field, treated in the framework of self-consistent linear response theory. We argue that the ligand states play crucial role in the ferromagnetism of Cr trihalides, though their contribution to Jeff strongly depends on additional assumptions, which are traced back to the fundamentals of adiabatic spin dynamics. Particularly, by neglecting the ligand spins in the Green's function method, Jeff can easily become antiferromagnetic, while by treating them as localized, one can severely overestimate the FM coupling. The best considered approach is based on the constraint method, where the ligand states are allowed to relax in response to each instantaneous reorientation of the Cr spins, controlled by a constraining field. Furthermore, the differences of the electronic structure of Cr trihalides in GGA and LSDA, and their impact on the exchange coupling are discussed in details, as well as the possible roles played by the on-site Coulomb repulsion U. © 2019 American Physical Society

Resonant Raman scattering in Ga(As, P) mediated by (localized exciton-LO phonon) complex

Resonance light scattering experiments in polar crystals at energies corresponding to Eex + nħωLO have suggested that dressed excitons are the relevant intermediate states. Configuration coordinate model is applied to calculate the resonance Raman spectrum (intensity of phonons lines as a function of incident frequency) of the mixed crystal GaAs 0.2P0.8 and compared with experimental results of Oueslati, Hirlimann and Balkanski (J. Physique 42 (1981) 1151-1156). This analysis gives coupling constants V1 and V2 of a localized exciton with the LO1 phonon and the LO2 phonon respectively : V1/ħωLO1 = 0.7 ± 0.2; V2/ ħωLO2 = 1.4 ± 0.3, and exciton energy E0 = 2.442 eV with its width γ = 0.030 eV.Dans les cristaux polaires, les expériences de diffusion résonnante de la lumière suggèrent que les excitons « dressés » sont les principaux états intermédiaires dans le processus de diffusion pour des énergies incidentes ħωi = Eex + nħωLO. Le spectre de résonance Raman (Intensité des Raies Raman en fonction de l'énergie incidente) du cristal mixte GaAs0,2P0,8 est calculé dans le cadre du modèle des coordonnées de configuration. La comparaison avec les résultats expérimentaux de Oueslati, Hirlimann et Balkanski (J. Physique 42 (1981) 1151-1156) donne les coefficients de couplage V1 et V2 de l'exciton localisé avec les phonons LO1 et LO2 respectivement : V1/ħω LO1 = 0,7 ± 0,2; V2/ħωLO2 = 1,4 ± 0,3, et l'énergie de l'exciton E0 = 2,442 eV ainsi que sa largeur γ = 0,030 eV

The absorption spectrum of a heteropolar crystal : the rôle of many-particle effects

We present (a) a local-orbital formulation of the electron-hole interaction in a heteropolar semiconductor which takes into account both the screened electron-hole attraction and its exchange counterpart, giving rise to the excitonic and local-field effects, respectively, and (b) a calculation of the absorption spectrum in GaP, which demonstrates the dominant rôle played by the continuum-exciton effect on the main optical absorption of a compound semiconductor. Our findings on the importance of many-particle effects closely parallel those of previous work on the covalent semiconductor Si.Nous présentons (a) une formulation, à l'aide d'orbitales locales, de l'interaction électron-trou dans un semi-conducteur hétéropolaire. Nous considérons l'attraction électron-trou et la répulsion entre paires d'électron-trou qui donnent naissance aux effets excitoniques et du champ local respectivement, et (b) un calcul du spectre d'absorption de GaP, qui démontre le rôle dominant joué par l'effet excitonique dans l'absorption optique d'un semi-conducteur composé. Nos résultats montrent l'importance des effets à N-corps et sont très comparables à des travaux antérieurs sur le silicium qui est un semi-conducteur covalent

The role of heating on the formation and the dynamics of YSO jets : I. A parametric study

International audienceTheoretical arguments as well as observations of young stellar objects (YSO) support the presence of a diversified circumstellar environment. A stellar jet is thought to account for most of the stellar spin down and disk wind outflow for the observed high mass loss rate, thus playing a major role in the launching of powerful jets. RY Tau, for instance, is an extensively studied intermediate mass pre-main sequence star. Observational data reveal a small scale jet called microjet. Nevertheless, it is not clear how the microjet shapes the jet observed at a large scale. The goal is to investigate the spatial stability and structure of the central jet at a large scale by mixing the stellar and disk components. We mix two existing analytical self-similar models for the disk and the stellar winds to build the initial set-ups. Instead of using a polytropic equation of state, we map from the analytical solutions, the heating and cooling sources. The heating exchange rate is controlled by two parameters, its spatial extent and its intensity. The central jet and the surrounding disk are strongly affected by these two parameters. We separate the results in three categories, which show different emissivity, temperature, and velocity maps. We reached this categorization by looking at the opening angle of the stellar solution. For cylindrically, well collimated jets, we have opening angles as low as 10 degrees between 8 and 10 au, and for the wider jets, we can reach 30 degrees with a morphology closer to radial solar winds. Our parametric study shows that the less heated the outflow is, the more collimated it appears. We also show that recollimation shocks appear consistently with UV observations in terms of temperature but not density

The role of heating on the formation and the dynamics of YSO jets : I. A parametric study

International audienceTheoretical arguments as well as observations of young stellar objects (YSO) support the presence of a diversified circumstellar environment. A stellar jet is thought to account for most of the stellar spin down and disk wind outflow for the observed high mass loss rate, thus playing a major role in the launching of powerful jets. RY Tau, for instance, is an extensively studied intermediate mass pre-main sequence star. Observational data reveal a small scale jet called microjet. Nevertheless, it is not clear how the microjet shapes the jet observed at a large scale. The goal is to investigate the spatial stability and structure of the central jet at a large scale by mixing the stellar and disk components. We mix two existing analytical self-similar models for the disk and the stellar winds to build the initial set-ups. Instead of using a polytropic equation of state, we map from the analytical solutions, the heating and cooling sources. The heating exchange rate is controlled by two parameters, its spatial extent and its intensity. The central jet and the surrounding disk are strongly affected by these two parameters. We separate the results in three categories, which show different emissivity, temperature, and velocity maps. We reached this categorization by looking at the opening angle of the stellar solution. For cylindrically, well collimated jets, we have opening angles as low as 10 degrees between 8 and 10 au, and for the wider jets, we can reach 30 degrees with a morphology closer to radial solar winds. Our parametric study shows that the less heated the outflow is, the more collimated it appears. We also show that recollimation shocks appear consistently with UV observations in terms of temperature but not density