RESUMO
An electron beam passing through a tube of small inner diameter which is lined on the inside with a dielectric layer will radiate energy in the THz range due to the interaction with the boundary. The resonant enhancement of certain frequencies is conditioned by structure parameters such as tube radius and the permittivity and thickness of the dielectric layer. In low-loss structures narrow-band radiation is generated which can be coupled out by suitable antennas. For higher frequencies, the coupling to the resistive outer metal layer becomes increasingly important. The losses in the outer layer prohibit reaching higher frequencies with narrow-band conditions. Instead, short broad-band pulses can be generated with still attractive power levels. In the first section of the paper, a general theory of the impedance of a two-layer structure is presented and the coupling to the outer resistive layer is discussed. Approximate relations for the radiated energy, power and pulse length for a set of structure parameters are derived and compared with numerical results in the following section. Finally, the first numerical result of the out-coupling of the radiation by means of a Vlasov antenna and estimates of the achieved beam quality are presented.
RESUMO
Red blood cells (RBCs) are known to be the most suitable cells to study oxidative stress, which is implicated in the etiopathology of many human diseases. The goal of the current study was to develop a new effective approach for assessing oxidative stress in human living RBCs using two-photon microscopy. To mimic oxidative stress in human living RBCs, an in vitro model was generated followed by two-photon microscopy imaging. The results revealed that oxidative stress is clearly visible on the two-photon microscopy images of RBCs under oxidative stress compared to no fluorescence in controls (P<0.0001). This novel approach for oxidative stress investigation in human living RBCs could efficiently be applied in clinical research and antioxidant compounds testing.
