Scanning Electron Microscopy of the Lateral Ventricle of the Pigeon Brain

Adult pigeons of both sexes were used for this study. Depending upon the distribution of various surface profiles, for example cilia, microvilli and blebs, ependymal areas with differing surface patterns were distinguished in the lateral ventricle. The topographical locations of these areas with respect to the underlying forebrain nuclei were determined in accord with the atlas of Karten and Hodos (1967). The medial surface (A) of the ventricle was much more densely ciliated than the lateral surface (B). There did not appear to be any correlation between a given surface pattern and a specific type of underlying nervous tissue. Comparison of the cell patterns seen in the pigeon brain with those seen in the analogous areas of the rat brain showed that it is not feasible to extrapolate from one zoological group to another. With the exception of the Kolmer cells populating the choroid plexus, there were remarkably few supraependymal cells in the pigeon lateral ventricle. Supraependymal nerve fibers were also extremely rare. Particular attention was given to the ependyma associated with the nucleus stria terminalis, to that of the lateral septal organ and to the choroid plexus. The possible classification of these areas into the group of the circumventricular organs is considered

Selective epitaxial growth of graphene on SiC

We present an innovative method of selective epitaxial growth of few layers graphene (FLG) on a pre-patterned SiC substrate. The methods involves, successively, the sputtering of a thin AlN layer on top of a mono-crystalline SiC substrate and, then, patterning it with e-beam lithography (EBL) and wet etching. The sublimation of few atomic layers of Si from the SiC substrate occurs only through the selectively etched AlN layer. The presence of the Raman G-band at ~1582 cm-1 in the AlN-free areas is used to validate the concept, it gives absolute evidence of the selective FLG growth.Comment: comments: 3 pages, reference 3 replace

Inspecting absorption in the spectra of extra-galactic gamma-ray sources for insight into Lorentz invariance violation

We examine what the absorbed spectra of extra-galactic TeV gamma-ray sources, such as blazars, would look like in the presence of Lorentz invariance violation (LIV). Pair-production with the extra-galactic background light modifies the observed spectra of such sources, and we show that a violation of Lorentz invariance would generically have a dramatic effect on this absorption feature. Inspecting this effect, an experimental task likely practical in the near future, can provide unique insight on the possibility of LIV.Comment: Published in Phys. Rev.

Growth of monolayer graphene on 8deg off-axis 4H-SiC (000-1) substrates with application to quantum transport devices

Using high temperature annealing conditions with a graphite cap covering the C-face of an 8deg off-axis 4H-SiC sample, large and homogeneous single epitaxial graphene layers have been grown. Raman spectroscopy shows evidence of the almost free-standing character of these monolayer graphene sheets, which was confirmed by magneto-transport measurements. We find a moderate p-type doping, high carrier mobility and half integer Quantum Hall effect typical of high quality graphene samples. This opens the way to a fully compatible integration of graphene with SiC devices on the wafers that constitute the standard in today's SiC industry.Comment: 11 pages, 4 figures , Submitted in AP

Method for analysis of heavy sulphur compounds using gas chromatography with flame photometric detection

A method for analysis of heavy sulphur compounds in wines, based on gas chromatography (GC) with flame photometric detection, is reported. Wine samples preparation includes a dichloromethane liquid–liquid extraction followed by concentration under a nitrogen atmosphere. The extracted fraction was also analysed by GC–mass spectrometry. The method enables high recovery of sulphur compounds in wine and satisfies the requirements of repeatability and sensitivity. Applications of the method to red, white and Port wines are reported

Testing the Special Relativity Theory with Neutrino interactions

A recent measurement of neutrino velocity by the OPERA experiment and prediction of energy loss of superluminal neutrino via the pair creation process $\nu\to \nu e^+e^-$ stimulated a search of isolated $e^+e^-$ pairs in detectors with good tracking capability traversed by a large flux of high energy neutrino like NOMAD. NOMAD has already searched for similar topologies. These results can be reinterpreted to provide stringent limits on special relativity violating parameters separately for each $\nu$ species.Comment: 3 pages, 3 figures, 1 table Accepted by EPL (Europhysics Letters

Contamination des milieux aquatiques Camarguais par les résidus de produits phyto sanitaires

Les auteurs font état des résultats qu’ils ont obtenu au terme de deux années de recherches sur la contamination des milieux aquatiques cam arguais par les résidus de produits phytosanitaires. En Camargue, les techniques culturales employées, notam ment en riziculture : irrigation intensive et extensive, lutte chimique contre les parasites, menacent de pollution l’ensemble des milieux aquatiques et plus particulièrement les étangs de la Réserve Naturelle Zoologique et Rotanique. Les polluants sont d’origine rhodanienne ou proviennent des traitements agricoles, herbicides et insecticides. L’étude concernant les herbicides est délicate à mener et les résultats obtenus jusqu’à présent sont trop fragmentaires pour pouvoir être interprétés. Des résultats plus complets concernant les insecticides montrent que la contamination de l’eau est encore très faible, mais que l’accumulation des résidus organochlorés aux différents échelons trophiques des biocœnoses présente un réel danger. Les pesticides les plus fréquemment rencontrés sont alpha HCH (d’origine rhodanienne), gamma HCH (d’origine rhodanienne et agricole). La présence à des doses décelables de DDT est moins courante. D’autres résidus ne sont soupçonnés dans l’eau que du fait de leur présence dans les tissus animaux (dieldrine). D’autres enfin ne sont décelés qu’en période de traitement des cultures (les organophosphorés et notamment le parathion), ou à la faveur de circonstances particulières (polychlorocamphane) . Les polychlorobiphényles présents dans le milieu posent un problème. Leur origine est probablement mixte (Rhône et spé cialités commerciales de pesticides agricoles où ils servent d’adjuvant). Ces organochlorés très stables sont accumulés à des taux relativement importants aussi bien dans les sédiments que dans les végétaux et les animaux aquatiques et présentent un réel danger pour la conservation des milieux naturels. La conciliation de l’agriculture et de la conservatoin de la nature en Camargue est subordonnée à deux conditions : le rejet au Rhône de toutes les eaux de drainage des cultures jusqu’à présent déversées dans le Vaccarès et la recherche de pratiques culturales moins polluantes que celles actuellement employées.Results are given of a two year study on the pollution by pesticide-residues of the aquatic environment in the Camargue. The agricultural techniques employed, notably in rice-growing (intensive and extensive irrigation, chemical control of pests) threaten the whole aquatic environment in the Camargue with pollution, particularly the lakes situated in the « Réserve Naturelie Zoologique et Botanique ». These pollutants originate from the Rhône river and from agricultural treatments using herbicides and insecticides. Herbicide studies have proved difficult to conduct and results obtained to date are too fragmentary to allow a clear interpretation. More detailed results on insecticides show that water pollu tion is still very low but that the accumulation of organo- chlorides at the different trophic levels of the ecosystem presents a real threat. The pesticides most frequently recorded are alpha HCH (BHC) (Rhone origin) and gamma HCH (Rhone and agricultural origin). Detectable doses of DDT are less frequently recorded. Other residues are only suspected in water because of their presence in animal tissues (dieldrin). Lastly, others are only revealed during the period when crops are treated (organophosphates and espe cially parathion) or as a result of very particular circumstances (polychlorocamphene) . The presence of polychlorobiphenyls in the environment raises a special problem. They probably have a mixed origin (Rhone and commercial types of agricultural pesticides where they serve as an adjuvant). These very stable organochlorides are accumulated at relatively high rates in sediments as well as in aquatic plants and animals, and present a real danger to the conservation of natural habitats. The conciliation of agriculture and nature conservation in the Camargue is dependent on two conditions : return into the Rhone of all run-off water from crops, at present discharged into the « Etang du Vaccarès », and research into cultural methods which produce less pollution than those in current use

Early stage formation of graphene on the C-face of 6H-SiC

An investigation of the early stage formation of graphene on the C-face of 6H-SiC is presented. We show that the sublimation of few atomic layers of Si out of the SiC substrate is not homogeneous. In good agreement with the results of theoretical calculations it starts from defective sites, mainly dislocations that define nearly circular flakes, which have a pyramidal, volcano-like, shape with a center chimney where the original defect was located. At higher temperatures, complete conversion occurs but, again, it is not homogeneous. Within the sample surface the intensity of the Raman G and 2D bands, evidences non-homogeneous thickness.Comment: 12 pages, 3 figure