Aharonov-Bohm signature for neutral excitons in type-II quantum dot ensembles

It is commonly believed that the Aharonov-Bohm (AB) effect is a typical feature of the motion of a charged particle interacting with the electromagnetic vector potential. Here we present a magnetophotoluminescence study of type-II InP/GaAs self-assembled quantum dots, unambiguously revealing the Aharonov-Bohm-type oscillations for neutral excitons when the hole ground state changes its angular momentum from lh = 0 to lh = 1, 2, and 3. The hole ring parameters derived from a simple model are in excellent agreement with the structural parameters for this system.Comment: Revised version, 10 pages, 3 figure

Efeito do tratamento com algumas vitaminas B na potencializaçã o do efeito antiinflamatório e antinociceptivo do diclofenaco e da talidomida

The effects of some B vitamins on chemical nociception in mice or paw edema in rats were investigated. A combination of thiamine (B1), pyridoxine (B6) and cyanocobalamin (B12), in doses of 100,100 and 5mg/kg, i.p., respectively, potentiated the inhibition by diclofenac or thalidomide of paw edema induced by carrageenin in rat. Antinociceptive effects of diclofenac and thalidomide inhibition of abdominal contortion were also potentiated by the combination of the vitamins B1, B6 and B12. Thiamine, pyridoxine and cyanocobalamin given singly were effective in potentiating antinociceptive effects of thalidomide, but only cyanocobalamin potentiated these effects of diclofenac, probably reflecting the differing mechanisms of action of the two drugs. The results document the positive influence of B vitamins on antinociceptive effects of diclofenac or thalidomide and support the use of B vitamins to shorten the treatment time and reduce the daily dose of anti-inflammatories

Optical Properties of Type-I and II Quantum Dots

This paper focuses on recent results on the optical properties of self-assembled quantum dots involving type-I InGaAs/GaAs and type-II InP/GaAs interfaces. In the first part, we focus on the InGaAs/GaAs quantum dots, that were used to study the influence of a two-dimensional electron gas on the optical emission of single quantum dots. In the second part, we present the results on type-II InP/GaAs quantum dots. In this system, we observed an experimental evidence indicating that the model used to interpret the blue shift of the type-II quantum well optical emission cannot be applied to type-II quantum dots

Efeito do tratamento com algumas vitaminas B na potencialização do efeito antiinflamatório e antinociceptivo do diclofenaco e da talidomida

Mostrou-se que o pré-tratamento com as vitaminas tiamina[B1], piridoxina[B6] e cianocobalamina [B12], isoladas ou administradas conjuntamente, não inibiu o edema de pata produzido pela carragenina em ratos, nem as contorções abdominais produzidas pelo ácido acético em camundongos. Por outro lado, o diclofenaco [25 ou 50mg/kg] ou talidomida [45mg/kg] inibiram o edema de pata em ratos, e a associação das três vitaminas à estas drogas, mas não as vitaminas administradas isoladamente, potencializou os efeitos do diclofenaco [25 ou 50mg/kg] no tempo de quatro horas e a talidomida [45mg/kg], nos tempos de duas, três e quatro horas após a carragenina. As contorções abdominais em camundongos foram inibidas pelas doses de 25 ou 50mg/ kg de diclofenaco. A associação das três vitaminas ou apenas da cianocobalamina, potencializou as duas doses do diclofenaco utilizadas. As contorções abdominais foram inibidas também pela talidomida [45mg/kg] e a associação das três vitaminas, ou cada uma das vitaminas administradas isoladamente, foram capazes de potencializar os efeitos da talidomida. É provável que a diferença no mecanismo de ação destas drogas seja responsável por esta diferença dos efeitos das vitaminas. O presente estudo preconiza o uso de antiinflamatórios, combinados com as vitaminas tiamina[B1], piridoxina[B6] e cianocobalamina [B12], em doenças crônicas, diminuindo assim a dose destas drogas e seus efeitos colaterais. Palavras-chave: Diclofenaco; talidomida; contorção abdominal; piridoxina; cianocobalamina; tiamina

Optical properties of type-I and II quantum dots

This paper focuses on recent results on the optical properties of self-assembled quantum dots involving type-I InGaAs/GaAs and type-II InP/GaAs interfaces. In the first part, we focus on the InGaAs/GaAs quantum dots, that were used to study the influence of a two-dimensional electron gas on the optical emission of single quantum dots. In the second part, we present the results on type-II InP/GaAs quantum dots. In this system, we observed an experimental evidence indicating that the model used to interpret the blue shift of the type-II quantum well optical emission cannot be applied to type-II quantum dots.555559Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Influence of pulse duration, energy, and focusing on laser-assisted water condensation

We investigate the influence of laser parameters on laser-assisted watercondensation in the atmosphere. Pulse energy is the most critical parameter. Nanoparticle generation depends linearly on energy beyond the filamentation threshold. Shorter pulses are more efficient than longer ones with saturation at ∼1.5 ps. Multifilamenting beams appear more efficient than strongly focused ones in triggering the condensation and growth of submicronic particles, while polarization has a negligible influence on the process. The data suggest that the initiation of laser-assisted condensation relies on the photodissociation of the air molecules rather than on their photoionizatio