Picoseconds
Mostrando 1-12 de 21 artigos, teses e dissertações.
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1. High-Speed Pulse Sequences through Semiconductor Optical Nonlinear Amplification and Buried Fiber Propagation
Abstract Microwave pulse bursts were obtained through optical domain intensity modulated microwave carriers, sliced by cascaded modulator technique, followed by non-linear semiconductor optical amplifier (SOA) pre-chirp. After 3 to 18 km of buried fiber propagation and photo detection, the microwave signals presented increased extinction ratio, up to 36 GHz,
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2020-09
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2. Análise morfológica e da resistência adesiva dos tecidos dentais duros irradiados com lasers de pulsos ultracurtos / Evaluation of dental hard tissues irradiated with ultra-short pulsed lasers. Influence on surface morphology and microtensile bond strength
The development of restorative dentistry has reached the era of esthetic adhesive restorations and minimally invasive approach, for which innovative techniques and advanced materials are constantly introduced. Conservative techniques aim not only to remove carious dental substrate, but also to prepare cavity surfaces for adhesive restoration. The main object
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 16/09/2010
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3. Espectroscopia Ãptica nÃo linear de vidros especiais e colÃides
Nonlinear optical properties of special glasses and colloids were studied using the zscan technique. This technique aalows to calculate the nonlinear refraction index and the nonlinear absorption coefficient using the self-focusing or defocusing effect that appears when the incident laser pass through a nonlinear medium. Orthophosphate and polyphosphate anti
Publicado em: 2008
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4. Estudos das características fotofísicas da porfirina mesotetrasulfonatofenil (TPPS4): efeitos da protonação e interação com micelas de CTAB / Study of photophysical characteristics of meso-tetrakis sulphonatophenyl porphyrin (TPPS4): effects of protonation and interaction with CTAB micelles.
In this work, we study photophysical characteristics of meso-tetrakis sulphonatophenyl porphyrin (TPPS4) in protonated and nonprotonated states. We obtained the whole set of photophysical parameters of TPPS4 excited states in homogeneous aqueous solution and in the presence of micelles from cationic detergent cetyltrimethylammonium bromide (CTAB). The parame
Publicado em: 2006
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5. "Não linearidades ópticas em azocompostos" / Optical nonlinearities in azocompounds
This work reports on the temperature dependence of linear and nonlinear properties of azocompounds solutions due to isomerization mechanisms. The dependence of pipi* transitions on the linear structure of azocompounds is already noticeble in the measurements of absorption spectra as function of the temperature for the trans isomer. Knowing the energy levels
Publicado em: 2004
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6. DESENVOLVIMENTO E CARACTERIZAÇÃO DE DISPOSITIVOS FOTÔNICOS UTILIZANDO POLÍMEROS / DEVELOPMENT AND CHARACTERIZATION OF PHOTONIC DEVICES
Conjugated organic polymers are of wide interest as nonlinear optical materials because of their potential applications in photonic devices, such as communication devices. They have a large and fast nonlinear optical response, as well as a great flexibility in their preparing method. For device applications, the most important parameters are: third-order opt
Publicado em: 1996
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7. Chaves eletricas a semicondutor controladas por pulsos laser de picosegundos
In this work we have studied the construction of ultra-fast electrical switches activated by ultrashort laser pulses. Such devices, built based on high-resistivity semiconductors, transform the energy of ultra short light pulses in electrical signals. These signals have rise time and pulse width of the order of pico-seconds. Parameters concerning the constru
Publicado em: 1984
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8. Picosecond molecular motions in bacteriorhodopsin from neutron scattering.
The characteristics of internal molecular motions of bacteriorhodopsin in the purple membrane have been studied by quasielastic incoherent neutron scattering. Because of the quasihomogeneous distribution of hydrogen atoms in biological molecules, this technique enables one to study a wide variety of intramolecular motions, especially those occurring in the p
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9. Direct observations of ligand dynamics in hemoglobin by subpicosecond infrared spectroscopy.
The photodissociation of CO from HbCO at ambient temperature is studied by means of a femtosecond IR technique. The bleaching of the FeCO absorption and the appearance of a new IR absorption near that of free CO are both observed at 300 fs after optical excitation. The bleach does not recover on the time scale of a few picoseconds but does recover by approxi
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10. Role of water on unfolding kinetics of helical peptides studied by molecular dynamics simulations.
Molecular dynamics simulations have been carried out with four polypeptides, Ala13, Val(13), Ser13, and Ala4Gly5Ala4, in vacuo and with explicit hydration. The unfolding of the polypeptides, which are initially fully alpha-helix in conformation, has been monitored during trajectories of 0.3 ns at 350 K. A rank of Ala < Val < Ser < Gly is found in the order o
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11. Redox effects on the excited-state lifetime in chlorosomes and bacteriochlorophyll c oligomers.
Oligomers of [E,E] BChl CF (8, 12-diethyl bacteriochlorophyll c esterified with farnesol (F)) and [Pr,E] BChl CF (analogously, M methyl, Pr propyl) in hexane and aqueous detergent or lipid micelles were studied by means of steady-state absorption, time-resolved fluorescence, and electron spin resonance spectroscopy. The maximum absorption wavelength, excited
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12. Interaction of small peptides with lipid bilayers.
Molecular dynamics simulations of the tripeptide Ala-Phe-Ala-O-tert-butyl interacting with dimyristoylphosphatidylcholine lipid bilayers have been carried out. The lipid and aqueous environments of the peptide, the alkyl chain order, and the lipid and peptide dynamics have been investigated with use of density profiles, radial distribution functions, alkyl c