Multi-excitonic complexes in single InGaN quantum dots

Cathodoluminescence spectra employing a shadow mask technique of InGaN layers grown by metal organic chemical vapor deposition on Si(111) substrates are reported. Sharp lines originating from InGaN quantum dots are observed. Temperature dependent measurements reveal thermally induced carrier redistribution between the quantum dots. Spectral diffusion is observed and was used as a tool to correlate up to three lines that originate from the same quantum dot. Variation of excitation density leads to identification of exciton and biexciton. Binding and anti-binding complexes are discovered.Comment: 3 pages, 4 figure

Paleomagnetism of mafic dikes from the Avalon Peninsula, eastern Newfoundland

As part of a major study of the Avalon zone in eastern Newfoundland, we describe the palromagnetism of two series of dikes located in the Bauline and Colliers-Harbour Main areas, respectively. Detailed alternating field (AF) and thermal experiments performed on these dikes indicate that they are characterized by two significantly different mean directions of magnetization: SE++(D = 153°, I = +62*; K = 46, N = 12 sites) and SW (D = 217°, I = +58°, K = 58, N = 12 sites ) with corresponding paleopole positions at A (4°N, 34"U; dp,dm = 8", 10°) and C (2"N, 81°W; dp, dm = 6", 9'). Antipoles A and C are located in southerly latitudes, and a comparison with other poles of Avalonian rocks from New Brunswick, Nova Scotia and Newfoundland indicates a Silurian to Siluro-Devonian age for these dikes. Poles A and B are interpreted as representing rapid apparent polar wander with respect to eastern Newfoundland during Silurian time. Two components of magnetization, corresponding to two distinct geological events, are observed in the dikes investigated and this situation favours the following geological scenario for the evolution of the Avalon microcontinent: (a) intracratonic rift zone resulting in long-lived Late Hadrynian and Cambrian continental extension, (b) a very late phase of distension in separating miniplates during Silurian and Early Devonian time. RÉSUMÉ Dans le cadre d'une étude d'envergure de la zone d'Avalon menée dans l'est de Terre-Neuve, nous décrivons le paléomagnétisme de deux séries de dykes situées dans les régions de Bauline et de Colliers - Harbour Main respectivement. Des experiences détaillées de désaimantation par champ alternatif (CA) et par lavage thermique démontrent que deux directions moyennes de l'aimantation caractérisent les dykes: SE++(D = 153°, I = +62*; K = 46, N = 12 sites de prélèvement) et SO (D = 217°, I = +58°, K = 58, N = 12 sites de prélèvement) avec des paléopöles correspondants aux positions A (4°N, 34"U; dp,dm = 8", 10°) et C (2"N, 81°W; dp, dm = 6", 9'). Les antipôles A et C se situent à des latitudes méridionales et par comparaison avec d'autres pôles de roches avaloniennes du Nouveau-Brunswick, de la Nouvelle-Écosse et de Terre-Neuve, on attrlbue aux dykes un âge Silurien à Siluro-Dévonien. On interprète les pôles géomagnétiques A et B comme le résultat de displacements rapides du pôle par rapport avec l'est de Terre-Neuve durant le Silurien. On observe dans ces dykes deux composantes de magnétisation, correspondant à deux évènements géologiques distincts. Ceci suggère le scenario suivant pour expliquer l’évolution du microcontinent Avalon: (a) un rift intracratonique qui se traduit par une longue période d'extension continentale depuis l'Hadrynien tardif jusqu'au Cambrien; (b) du Silurien jusqu'au début du Dévonien, une phase tardive de distension lors de la séparation des miniplaques. [Traduit par le journal

Anti-AGEs Algerian vegetal extracts. Phytochemical study of Daucus aureus desf. (Apiaceae)

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Optical imaging of luminescence for in vivo quantification of gene electrotransfer in mouse muscle and knee

BACKGROUND: Optical imaging is an attractive non-invasive way to evaluate the expression of a transferred DNA, mainly thanks to its lower cost and ease of realization. In this study optical imaging was evaluated for monitoring and quantification of the mouse knee joint and tibial cranial muscle electrotransfer of a luciferase encoding plasmid. Optical imaging was applied to study the kinetics of luciferase expression in both tissues. RESULTS: The substrate of luciferase (luciferin) was injected either intraperitonealy (i.p.) or in situ into the muscle or the knee joint. Luminescence resulting from the luciferase-luciferin reaction was measured in vivo with a cooled CCD camera and/or in vitro on tissue lysate. Maximal luminescence of the knee joint and muscle after i.p. (2.5 mg) or local injection of luciferin (50 μg in the knee joint, 100 μg in the muscle) were highly correlated. With the local injection procedure adopted, in vivo and in vitro luminescences measured on the same muscles significantly correlated. Luminescence measurements were reproducible and the signal level was proportional to the amount of plasmid injected. In vivo luciferase activity in the electrotransfered knee joint was detected for two weeks. Intramuscular electrotransfer of 0.3 or 3 μg of plasmid led to stable luciferase expression for 62 days, whereas injecting 30 μg of plasmid resulted in a drop of luminescence three weeks after electrotransfer. These decreases were partially associated with the development of an immune response. CONCLUSION: A particular advantage of the i.p. injection of substrate is a widespread distribution at luciferase production sites. We have also highlighted advantages of local injection as a more sensitive detection method with reduced substrate consumption. Besides, this route of injection is relatively free of uncontrolled parameters, such as diffusion to the target organ, crossing of biological barriers and evidencing variations in local enzymatic kinetics, probably related to the reaction medium in the targeted organ. Optical imaging was shown to be a sensitive and relevant technique to quantify variations of luciferase activity in vivo. Further evaluation of the effective amount of luciferase in a given tissue by in vivo optical imaging relies on conditions of the enzymatic reaction and light absorption and presently requires in vitro calibration for each targeted organ

Selection of Algerian medicinal plants according to a screening of their anti-AGEs properties

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