Poopćenje analitičkih izraza za pseudo -voigtovu funkciju koja se rabi u analizama difrakcijskih vrhova

Nous revisitons ici la théorie, utilisée en analyse des profils de raies de diffraction des rayons X et des neutrons, relative à la fonction de forme du pic dite de pseudo -Voigt (notée pV). Nous présentons une généralisation des expressions de la largeur intégrale et à mi-hauteur de la fonction pV, de la transformée de Fourier de cette fonction ainsi que du seuil du paramètre de mélange h. Nous incorporons nos résultats dans la procédure de fit, ce qui améliore les facteurs de précision.Razmatramo teoriju koja se primjenjuje u analizi linija difraktiranog rentgenskog zračenja i neutrona a odnosi se na tzv. pseudo-Voigtovu (skraćeno pV) funkciju za opis oblika vrha. Dajemo poopćenje analitičkog izraza za ukupnu širinu i širinu na pola visine vrha funkcije pV, Fourierovu transformaciju izraza, kao i prag parametra miješanja η. Primijenjujemo naš postupak za prilagodbu i postižemo poboljšanje točnosti

Mice Doubly-Deficient in Lysosomal Hexosaminidase A and Neuraminidase 4 Show Epileptic Crises and Rapid Neuronal Loss

Tay-Sachs disease is a severe lysosomal disorder caused by mutations in the HexA gene coding for the α-subunit of lysosomal β-hexosaminidase A, which converts GM2 to GM3 ganglioside. Hexa−/− mice, depleted of β-hexosaminidase A, remain asymptomatic to 1 year of age, because they catabolise GM2 ganglioside via a lysosomal sialidase into glycolipid GA2, which is further processed by β-hexosaminidase B to lactosyl-ceramide, thereby bypassing the β-hexosaminidase A defect. Since this bypass is not effective in humans, infantile Tay-Sachs disease is fatal in the first years of life. Previously, we identified a novel ganglioside metabolizing sialidase, Neu4, abundantly expressed in mouse brain neurons. Now we demonstrate that mice with targeted disruption of both Neu4 and Hexa genes (Neu4−/−;Hexa−/−) show epileptic seizures with 40% penetrance correlating with polyspike discharges on the cortical electrodes of the electroencephalogram. Single knockout Hexa−/− or Neu4−/− siblings do not show such symptoms. Further, double-knockout but not single-knockout mice have multiple degenerating neurons in the cortex and hippocampus and multiple layers of cortical neurons accumulating GM2 ganglioside. Together, our data suggest that the Neu4 block exacerbates the disease in Hexa−/− mice, indicating that Neu4 is a modifier gene in the mouse model of Tay-Sachs disease, reducing the disease severity through the metabolic bypass. However, while disease severity in the double mutant is increased, it is not profound suggesting that Neu4 is not the only sialidase contributing to the metabolic bypass in Hexa−/− mice

Relation between interlayer exchange coupling and nonferromagnetic behavior of Fe in Ni/Fe/Co superlattices

International audienceRecent experimental studies, using a photoemission electron microscope on a Ni∕Fe∕Co∕Cu(100) system, found that the Fe layers at both the Fe∕Co and Fe∕Ni interfaces are ferromagnetically ordered, and that there is an oscillatory intercoupling between the Co and Ni layers across the Fe spacer. In the present paper we performed self-consistent ab initio calculations to determine the magnetic profile and the interlayer exchange coupling (IEC) in fcc Ni∕Fen∕Co(100) superlattices, for different thicknesses of the Fe spacer (n=1–7). The compositional ordering at the Fe∕Co and Fe∕Ni interfaces leads to a completely different IEC behavior. Strong Fe-Ni(Co) ferromagnetic coupling with enhanced Fe magnetic moment are always obtained in the intermixed layers

Analytical Modeling of Dual-Junction Tandem Solar Cells Based on an InGaP/GaAs Heterojunction Stacked on a Ge Substrate

An analytical model is used to describe the electrical characteristics of a dual-junction tandem solar cell performing with a conversion efficiency of 32.56% under air mass 1.5 global (AM1.5G) spectrum. The tandem structure consists of a thin heterojunction top cell made of indium gallium phosphide (InGaP) on gallium arsenide (GaAs), mechanically stacked on a relatively thick germanium (Ge) substrate, which acts as bottom cell. In order to obtain the best performance of such a structure, we simulate for both the upper and lower sub-cell the current density–voltage, power density–voltage, and spectral response behaviors, taking into account the doping-dependent transport parameters and a wide range of minority carrier surface recombination velocities. For the proposed tandem cell, our calculations predict optimal photovoltaic parameters, namely the short-circuit current density (J sc ), open-circuit voltage (V oc ), maximum power density (P max ), and fill factor (FF) are J sc = 28.25 mA/cm 2 , V oc = 1.24 V, P max = 31.64 mW/cm 2 , and FF = 89.95%, respectively. The present study could prove useful in supporting the design of high efficiency dual junction structures by investigating the role of different materials and physical parameters

Effect on alloying at the Fe/Ni(001) interfaces on the interlayer exchange coupling

We investigate the stability of various ordered FeNi alloys at the interfaces of Fe/Ni superlattices by using ab initio density functional calculation. We consider an Fe 0.5 Ni 0.5 ordered alloy of one or two monolayers thick at different positions beyond the interface and the possibility of an interdiffusion of a complete monolayer of Ni(Fe) in Fe(Ni) slab. An interfacial atomic layer of Fe 0.5 Ni 0.5 exchanged with its adjacent Ni monolayers, leading to a buffer zone of Ni 3Fe composition is found to be the most stable structural configuration. For this atomic arrangement we investigate the magnetic profile and the resulting interlayer exchange coupling between the Ni slabs for Fe spacer thickness of 0 to 4 monolayers. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 200675.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures), 73.21.Ac Multilayers, 75.50.Bb Fe and its alloys,