Preparation and characterization of ceramic sol–gel composite coatings - densification temperature optimisation -

Thick (~ 25 µm) ceramic coatings on porous ceramic substrates were elaborated by means of dispersing alumina and rutile powders in a silica sol-gel solution. Resulting coatings, which present a composite structure consisting in Al2O3 and TiO2 grains embedded in an amorphous SiO2 matrix, demonstrate a good adhesion to the substrate and a real improvement of its surface by closing the porosity and also reducing the roughness. Mechanical characterization by micro-indentation showed an increase of the coating hardness when the thermal treatment temperature increases. This hardness increase is attributed to the densification of the coating that proceeds by grain rearrangement thanks to the sol-gel derived silica phase viscosity decrease during the thermal treatment. In order to decrease the coating densification temperature, the silica intergranular phase was modified by incorporating Na+ ions in its structure. This was done by adding NaCl salt in the sol-gel solution and leads to the decrease of the densification temperature

Nombre chromosomique et caryotype de Cistus Ladanifer subsp. Africanus Dansereau (Cistaceae)

L’approche caryologique de Cistus ladanifer subsp. africanus Dansereau (Cistaceae) rapportée pour la première fois sur des populations du Maroc, a mis en évidence le nombre et la formule chromosomiques avec 2n = 2x = 18 = 10 m + 4 sm + 4 st ; l’existence d’un phénomène d’endomitose fréquent et la présence à la fois de cellules à chromosomes en croix et de cellules à chromosomes normaux et ceci dans un même méristème. Aussi, les deux variétés, différentes par leurs sécrétions aromatiques volatiles, ont des caryotypes similaires.The kariological approach of Cistus ladanifer subsp. africanus Dansereau (Cistaceae), reported for the fi rst time on populations of Morocco, highlighted the chromosomal number and formula (2n = 2x =18 = 10 m + 4 sm + 4 st); the existence of frequent endomitosis phenomenon’s. We have also noticed that in the same root we can fi nd two different shapes of chromosome: normal and in cross ones. Moreover, the two varieties which differ from their volatile aromatic secretions have the same karyotype

Nombre chromosomique de quelques Angiospermes marocaines

Se indican los números cromosómicos de cinco taxones pertenecientes a cinco familias de Angiospermas de Marruecos: Allium porrum 2n=32; Armeria simplex 2n=18; Asphodelus ramosus subsp. ramosus n=28; Delphinium nanum subsp. nanum 2n=16 et Dipcadi serotinum 2n=8 et 32. Cada taxon se acompaña de una fotografía en mitosis o meiósis así como de un breve comentario."Chromosome numbers of some Moroccan angiosperm". Chromosome numbers of five taxa from five families of Moroccan angiosperms are reported: Allium porrum 2n=32; Armeria simplex 2n=18; Asphodelus ramosus subsp. ramosus n=28; Delphinium nanum subsp. nanum 2n=16 and Dipcadi serotinum 2n=8 and 32. Mitotic or meiotic metaphases microphotographs and brief comments are detailed for each taxa studied

Variabilité chromosomique de neuf plantes medicinales au Maroc

Se indican los números cromosómicos de 9 taxones usados como medicinales en Marruecos: Carum carvi 2n=20; Coriandrum sativum n=11 y 2n=22; Cuminum cyminum 2n=14; Foeniculum vulgare subsp. dulce 2n=22; Nigella sativa 2n=12; Pennisetum typhoides 2n=14; Petroselinum crispum n=11 y 2n=22; Pimpinella anisum 2n=20 y Trigonella foenum-graecum 2n=16. La mayoría de estos números se indican por primera vez en poblaciones de Marruecos. Cada taxon se acompaña de una fotrografía en mitosis así como de un breve comentario.Chromosomal variability of some medicinal plants in Morocco. Chromosome numbers of nine plants used in Moroccan pharmacopoeia are reported: Carum carvi 2n=20; Coriandrum sativum n=11 and 2n=22; Cuminum cyminum 2n=14; Foeniculum vulgare subsp. dulce 2n=22; Nigella sativa 2n=12; Pennisetum typhoides 2n=14; Petroselinum crispum n=11 and 2n=22; Pimpinella anisum 2n=20 and Trigonella foenum-graecum 2n=16. Most of those numbers are reported for the first time in Moroccan populations. Mitotic metaphases microphotographs and brief comments are detailed for each taxa studied

Étude du tegument des graines des genres Cytisus L., Argyrocytisus (Maire) Raynaud, Chamaecytisus Link et Genista L. (Section Teline Medik) (Fabaceae) au Maroc

Étude du tegument des graines des genres Cytisus L., Argyrocytisus (Maire) Raynaud, Chamaecytisus Link et Genista L. (section Teline Medik.) (Fabaceae) au Maroc. La structure tégumentaire des graines de 11 espèces appartenant aux genres Cytisus L., Argyrocytisus (Maire) Raynaud, Chamaecytisus Link et Genista L. (section Teline Medik.) a été étudiée au microscope électronique à balayage MEB. Deux types principaux de structures ont été notées (microplissée et réticulée-plissée avec des cellules pentagonales ou hexagonales délimitées par un sillon ou un bord en relief intercellulaire) et discutées selon les taxons considérés et leur classification infragénérique. La description des strates du tégument et celle de la région hilaire a été également réalisée. En coupe, le tégument est constitué de deux couches: l'externe avec des cellules en palissade (assise de Malpighi) et l'interne avec des cellules en sablier (osteosclereides). La taille de ces deux couches varie énormément à l'intérieur d'une même graine, ce qui ne permet pas de différencier les taxons. Au niveau du hile, la couche palissadique est double: l'externe provient du funicule, l'interne étant la continuité de la couche de Malpighi. Au dessus se trouve une bande de trachéides dont les ponctuations sont verruqueuses, suivi d'un parenchyme lacuneux

The presence of valine at residue 129 in human prion protein accelerates amyloid formation

The polymorphism at residue 129 of the human PRNP gene modulates disease susceptibility and the clinicopathological phenotypes in human transmissible spongiform encephalopathies. The molecular mechanisms by which the effect of this polymorphism are mediated remain unclear. It has been shown that the folding, dynamics and stability of the physiological, alpha-helix-rich form of recombinant PrP are not affected by codon 129 polymorphism. Consistent with this, we have recently shown that the kinetics of amyloid formation do not differ between protein containing methionine at codon 129 and valine at codon 129 when the reaction is initiated from the a-monomeric PrPC-like state. In contrast, we have shown that the misfolding pathway leading to the formation of beta-sheet-rich, soluble oligomer waS favoured by the presence of methionine, compared with valine, at position 129. In the present work, we examine the effect of this polymorphism on the kinetics of an alternative misfolding pathway, that of amyloid formation using partially folded PrP allelomorphs. We show that the valine 129 allelomorph forms amyloids with a considerably shorter lag phase than the methionine 129 allelomorph both under spontaneous conditions and when seeded with pre-formed amyloid fibres. Taken together, our studies demonstrate that the effect of the codon 129 polymorphism depends on the specific misfolding pathway and on the initial conformation of the protein. The inverse propensities of the two allelomorphs to misfold in vitro through the alternative oligomeric and amyloidogenic pathways could explain some aspects of prion diseases linked to this polymorphism such as age at onset and disease incubation time. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved

Nombre chromosomique d’angiospermes marocaines

Le nombre chromosomique de douze taxa appartenant à onze familles d’angiospermes marocaines sont rapportés: Achyranthes sicula n = 40; Bidens pilosa 2n = 60 et n = 30; Carrichtera annua 2n = 16; Clematis cirrhosa 2n = 16; Eryngium atlanticum n = 8; Parietaria judaica n = 13; Parietaria lusitanica subsp. lusitanica n = 10;  Scrofularia canina 2n = 24; Sixalix atropurpurea 2n = 16; Solanum sodomaeum n = 12;  Spergularia diandra 2n = 18 et Urginea maritima n = 30. La plus part des ces nombres sont rapportés pour la première fois sur des populations marocaines. Des microphotographies mitotiques ou méiotiques ainsi qu’un bref commentaire sont signalés pour chaque taxon.Chromosome numbers of twelve taxa from eleven families of Moroccan angiosperms are reported: Achyranthes sicula n = 40; Bidens pilosa 2n = 60 et n = 30;  Carrichtera annua 2n = 16; Clematis cirrhosa 2n = 16; Eryngium atlanticum n = 8; Parietaria judaica n = 13; Parietaria lusitanica subsp. lusitanica n = 10;  Scrofularia canina 2n = 24; Sixalix atropurpurea 2n = 16; Solanum sodomaeum n = 12;  Spergularia diandra 2n = 18 and Urginea maritima n = 30. Most of those numbers were reported for the fi rst time in Moroccan populations. Mitotic or meiotic metaphases microphotographs and brief comments are detailed for each taxa studied

Nombre chromosomique de quelques plantes a fleurs du Maroc

Se indican los números cromosómicos de once taxones pertenecientes a nueve familias de Angiospermas de Marruecos: Armeria simplex n = 9; Atriplex semibaccata 2n = 18; Cistanche phelypaea n = 20; Echium velutinum subsp. velutinum 2n = 16; Linaria bipartita n = 6; Lupinus cosentinii n = 16; Mesembryanthemum nodiflorum 2n = 38; Plantago amplexicaulis 2n = 10; Sonchus bourgeaui 2n = 16; Vicia lutea et Vicia pseudocracca n = 7. Nueve de estos números se indican por primera vez en poblaciones de Marruecos. Cada taxon estudiado se acompaña de un breve comentario y de la mayoría de ellos se aportan observaciones en mitosis o meiosis.Chromosome numbers of some flowering plants from Morocco. Chromosome numbers of eleven taxa from nine families of Moroccan angiosperms are reported: Armeria simplex n = 9; Atriplex semibaccata 2n = 18; Cistanche phelypaea n = 20; Echium velutinum subsp. velutinum 2n = 16; Linaria bipartita n = 6; Lupinus cosentinii n = 16; Mesembryanthemum nodiflorum 2n = 38; Plantago amplexicaulis 2n = 10; Sonchus bourgeaui 2n = 16; Vicia lutea and Vicia pseudocracca n = 7. Nine of those numbers were reported for the first time in Moroccan populations. Mitotic or meiotic metaphases microphotographs and brief comments are detailed for each taxa studied.Ministère de l’Enseignement Supérieur SVT 04 / 0