RESUMO
High-power, external-cavity semiconductor lasers with narrow bandwidth and fiber-coupled output are designed and constructed. An output power of 540 mW is coupled out of a 100-mum multimode fiber with coupling efficiency of 72% when the laser is operated at 1.1 A. The emission linewidth is as narrow as 22 GHz, and the wavelength is tunable from 779.7 to 793.0 nm. Application of such lasers to remote real-time Raman sensing of materials is also demonstrated.
RESUMO
An experimental investigation of a semiconductor laser subject to moderate to strong optical feedback shows that sporadic power discontinuities occur everywhere along the boundary separating feedback regimes IV and V. These low-frequency fluctuations (LFF's) do not occur just near the solitary-laser threshold as previously thought. Furthermore, although the LFF's appear as power dropouts near threshold, they manifest as power jump-ups well above threshold. Theoretical modeling shows reasonable agreement with experiments.
Assuntos
Eletrocardiografia , Hipocalcemia/diagnóstico , Doenças do Recém-Nascido/diagnóstico , Doenças do Prematuro/diagnóstico , Acidose/complicações , Fatores Etários , Asfixia Neonatal/complicações , Cálcio/sangue , Feminino , Idade Gestacional , Humanos , Hipocalcemia/etiologia , Recém-Nascido , Doenças do Recém-Nascido/sangue , Doenças do Prematuro/sangue , Gravidez , Gravidez em Diabéticas/complicações , Síndrome do Desconforto Respiratório do Recém-Nascido/complicações , Choque/complicaçõesAssuntos
Aminoácidos/metabolismo , Estradiol/farmacologia , Sódio/farmacologia , Útero/metabolismo , Alanina/metabolismo , Ácidos Aminoisobutíricos/metabolismo , Animais , Transporte Biológico/efeitos dos fármacos , Isótopos de Carbono , Ciclopentanos/metabolismo , Feminino , Cinética , Modelos Biológicos , Concentração Osmolar , Ouabaína/farmacologia , Fenilalanina/metabolismo , Potássio/farmacologia , Prolina/metabolismo , Ratos , Estimulação Química , Útero/efeitos dos fármacos , Valina/metabolismoRESUMO
1. Preincubation of the immature rat uterus under physiological conditions was found to increase its subsequent ability to transport alpha-aminoisobutyric acid, l-proline, l-alanine and 1-aminocyclopentanecarboxylic acid. Uptakes of l-valine, l-phenylalanine and l-leucine were not affected. With alpha-aminoisobutyric acid, a doubling of the uptake could be obtained after a 3-5h preincubation period. Uteri from oestradiol-primed rats gave increases similar to those found in tissues from untreated animals. In both cases the preincubation increased the V(max.) of alpha-aminoisobutyric acid uptake but did not affect the K(m). 2. The conditions during the preincubation period determined the increase in subsequent uptake of alpha-aminoisobutyric acid. No increase in uptake was found if the preincubation was carried out at 1 degrees C, in the presence of cyanide or dinitrophenol, under anaerobiosis or with a concentration of puromycin that depressed incorporation of l-leucine into protein by 95%. The puromycin was also shown to prevent the increase in V(max.) normally found after the preincubation period. In addition, no increase was found if Na(+) was omitted from the preincubation medium. Other inorganic ions had smaller effects. 3. The uptake of alpha-aminoisobutyric acid by uteri before and after a preincubation period showed the same general patterns of sensitivity to competitive inhibitors, K(+), pH, temperature and 2,4-dinitrophenol. 4. The results suggest that the preincubation leads to an increase in a protein component of the ;A system' for amino acid transport in the uterus, and that metabolic energy is required for the reactions involved.