Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 4 de 4
Filtrar
Mais filtros

Base de dados
Tipo de documento
Assunto da revista
País de afiliação
Intervalo de ano de publicação
1.
Appl Opt ; 49(25): 4780-90, 2010 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-20842804

RESUMO

In-vacuum Faraday isolators (FIs) are used in gravitational wave interferometers to prevent the disturbance caused by light reflected back to the input port from the interferometer itself. The efficiency of the optical isolation is becoming more critical with the increase of laser input power. An in-vacuum FI, used in a gravitational wave experiment (Virgo), has a 20 mm clear aperture and is illuminated by an almost 20 W incoming beam, having a diameter of about 5 mm. When going in vacuum at 10(-6) mbar, a degradation of the isolation exceeding 10 dB was observed. A remotely controlled system using a motorized lambda=2 waveplate inserted between the first polarizer and the Faraday rotator has proven its capability to restore the optical isolation to a value close to the one set up in air.

2.
Opt Express ; 17(20): 18211-8, 2009 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-19907612

RESUMO

Imaging objects embedded within highly scattering media by coupling light and ultrasounds (US) is a challenging approach. In deed, US enable direct access to the spatial localization, though resolution can be poor along their axis (cm). Up to now, several configurations have been studied, giving a millimetric axial resolution by applying to the US a microsecond pulse regime, as is the case with conventional echography. We introduce a new approach called Acousto-Optical Coherence Tomography (AOCT), enabling us to get a millimetric resolution with continuous US and light beams by applying random phase jumps on US and light. An experimental demonstration is performed with a self-adaptive holographic setup containing a photorefractive GaAs bulk crystal and a single large area photodetector.


Assuntos
Acústica/instrumentação , Aumento da Imagem/instrumentação , Tomografia de Coerência Óptica/instrumentação , Ultrassonografia/instrumentação , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Integração de Sistemas
3.
Science ; 355(6321): 184-188, 2017 01 13.
Artigo em Inglês | MEDLINE | ID: mdl-28082591

RESUMO

The hippocampus is thought to initiate systems-wide mnemonic processes through the reactivation of previously acquired spatial and episodic memory traces, which can recruit the entorhinal cortex as a first stage of memory redistribution to other brain areas. Hippocampal reactivation occurs during sharp wave-ripples, in which synchronous network firing encodes sequences of places. We investigated the coordination of this replay by recording assembly activity simultaneously in the CA1 region of the hippocampus and superficial layers of the medial entorhinal cortex. We found that entorhinal cell assemblies can replay trajectories independently of the hippocampus and sharp wave-ripples. This suggests that the hippocampus is not the sole initiator of spatial and episodic memory trace reactivation. Memory systems involved in these processes may include nonhierarchical, parallel components.


Assuntos
Região CA1 Hipocampal/fisiologia , Córtex Entorrinal/fisiologia , Memória Espacial/fisiologia , Animais , Região CA1 Hipocampal/citologia , Córtex Entorrinal/citologia , Potenciais Evocados , Masculino , Ratos
4.
Biochem Pharmacol ; 47(10): 1827-33, 1994 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-8204099

RESUMO

Functional characteristics of mitochondria isolated from liver, brain and heart were studied in ethanol-fed rats using ethanol administration in drinking water as a model of moderate alcohol intoxication. Our results show a slight decrease in liver cytochrome aa3 content, the mitochondrial alteration which is most consistently observed during chronic ethanol feeding. In liver and heart mitochondria, ethanol consumption led to an increase in state 3 respiration with NAD(+)-linked substrates, whereas no changes were apparent in respiration rates with succinate as substrate. However a decrease was found in state 3 respiration with succinate in brain mitochondria isolated from ethanol-fed rats. Submitochondrial particles (SMP) were used to study the superoxide radical (O2-.) production at the level of antimycin-inhibited regions of the respiratory chain. It appears that there is no clear correlation between ethanol effects on respiration and O2-. production. Whereas O2-. generation remained unchanged in heart mitochondria, an elevation of O2-. generation was observed in brain mitochondria, and in contrast, the rate of O2-. production was decreased in liver mitochondria of the ethanol-group in comparison to the control-group. Our findings support a tissue specificity for the toxic effects of ethanol towards the mitochondria and indicate that mitochondrial free radical mechanisms are involved in ethanol-induced toxicity in the brain.


Assuntos
Química Encefálica , Etanol/toxicidade , Mitocôndrias Cardíacas/efeitos dos fármacos , Mitocôndrias Hepáticas/efeitos dos fármacos , Consumo de Bebidas Alcoólicas/metabolismo , Animais , Radicais Livres , Masculino , Mitocôndrias Cardíacas/metabolismo , Mitocôndrias Hepáticas/metabolismo , Consumo de Oxigênio , Ratos , Ratos Sprague-Dawley , Superóxidos/metabolismo
SELEÇÃO DE REFERÊNCIAS
Detalhe da pesquisa