Current-voltage characteristics of p-Si/carbon junctions fabricated by pulsed laser deposition

Amorphous carbon/p-Si junctions were fabricated at different temperatures using KrF excimer laser (λ = 248 nm, pulsed duration 20 ns). The current-voltage measurements of the devices showed diode characteristics. The value of various junction parameters such as ideality factor, barrier height, and series resistance were determined from forward bias I-V characteristics, Cheung method, and Norde’s function. There was a good agreement between the diodes parameters obtained from these methods. The ideality factor of ∼1.12 and barrier height of ∼0.37 eV were estimated using current-voltage characteristics for films grown at room temperature.     

A Single-Phase Boost Rectifier System for Wide Range of Load Variations

Converters operated in discontinuous-conduction-mode (DCM) and in continuous-conduction-mode (CCM) are suitable for lighter and higher loads, respectively. A new, constant switching frequency based single-phase rectifier system is proposed, which operates in DCM and in CCM for outputs less than and greater than 50% rated load, respectively, covering a wide range of load variation. The power circuit and the control circuit of the proposed rectifier are easily configurable for DCM and CCM operations. The measured load current is used to select the desired operating mode. The peak device current under DCM is limited to rated device current under CCM without using a device of higher current rating. The input current shaping under CCM and DCM are based on the comparison of measured input current with linear and nonlinear carriers, respectively. A load current feedforward scheme is presented to improve the system dynamic performance and also to ensure a smooth transition between the two operating modes. All the necessary control operations are performed without using multiplication, division and square-root operation. The proposed rectifier shows improved input current characteristics over the existing CCM converters for the above load range. This is validated on a 600-W rectifier prototype. Simulation and experimental results are presented     

In vivo microdialysis and gas chromatography/mass spectrometry for studies on release of N-acetylaspartlyglutamate and N-acetylaspartate in rat brain hypothalamus

Microdialysis and gas chromatography/mass spectrometry was used for the measurement of extracellular N-acetylaspartate (NAA) and N-acetylaspartylglutamate (NAAG) in rat hypothalamus. The sensitivity of the method for each of these compounds was approximately 5 pmol/30 microliters of dialysate. Baseline NAA concentrations in dialysate were estimated to be approximately 25 pmol/36 microliters, while that for NAAG was at or below the detection limit of 5 pmol/ 36 microliters. In vivo and in vitro calibrations of microdialysis probes showed that the recovery for NAA was approximately 10 percent. For NAAG, the in vitro recovery was 6.3%, and in vivo recovery, 11%. Depolarization stimulation using 100 mM KCl in the microdialysis perfusate was employed to measure extracellular NAA and NAAG concentrations. Extracellular NAA was elevated to approximately 70 pmol/36 microliters dialysate following depolarization. No significant elevation of NAAG was observed. By infusing known amounts of stable isotopically labeled NAAG-d3 via the microdialysis probe and measuring the isotopically labeled catabolic product, NAA-d3, in collected microdialysate, we were able to confirm the existence of one or more hydrolytic enzymes active towards NAAG in the hypothalamus. This finding suggest the possible involvement of active metabolic processes in the relationship between NAAG and NAA releases.