[en] The Bipolar Junction Transistor (BJT) study is a regular subject on analog electronic subjects taught in the initial phase of electronic engineering courses. This electronic component, often considered elementary, is far from being simple to explain because it covers several concepts, such as three Regions of Operation, two Working Regimes, and two Region of Operation Boundaries. It is not surprising then that students often find it difficult to understand the functioning of this component. The present article describes partially the work developed by a team with a number of students in order to understand the difficulties of teaching/learning the BJT. We present the students’ perceptions from the analysis of several traditional and modern means to support the learning of the BJT. Interestingly, the learning BJT model considered simpler for beginner students corresponds to the model that originally gave it the name i.e. Trans-Resistor (Transistor). (Author)

[en] Teaching and learning Operational Amplifiers (OpAmps) in electronic engineering courses is a requirement, since they are a type of integrated circuit widely used for implementing simple or complex circuits. As a contribution to improve the way this integrated circuit is included in electronic engineering courses’ curricula, it was designed and implemented a reconfigurable and expandable kit to teach electronic circuits based on the OpAmp uA741. Able to run in a PC, the kit comprises a software application locally interfaced with a hardware platform. This platform includes a circuit with the OpAmp uA741 able to be reconfigured according to a set of parameters defined by a software application. Besides the reconfiguration capability provided by this kit, it also enables the establishment of automatic connections for measuring or applying signals to a reconfigured circuit, plus the ability to simulate the same or other OpAmp-based circuits. This paper provides an overview about the OpAmp uA741 and about its relevance in engineering education. Features and functionalities provided by the kit is described. At the end, supported by a technical demonstration of the kit in an international conference, some teachers’ opinions about their perceptions concerning its adoption in a real educational scenario are presented. (Author)

[en] Recent and proposed improvements in spatial resolution, temporal resolution, contrast, and detection efficiency for x-ray framing cameras are discussed in light of present and future laser-plasma diagnostic needs. In particular, improvements in image contrast above hard x-ray background levels is demonstrated by using high aspect ratio tapered pinholes

[en] Full text: A case report of a 70 year old man acutely presenting with a large descending thoracic aortic aneurysm, ruptured into the adjacent oesophagus. He was treated with an Aneurex covered stent (Medtronics). This patient has a long history of ischaemic heart disease, hypertension and previously treated abdominal aortic aneurysm. After diagnosis by CT, the bleeding was emergency temponaded by insertion of a Sengstaken-Blackmore tube into the oesophagus and inflated to arterial pressure. After stabilisation in ICU, it was decided that open surgery would probably prove fatal, and insertion of a covered thoracic aortic stent was performed in theatre with a femoral artery cut-down. Post-operatively the bleeding from the aortic aneurysm ceased. However, the patient has ongoing problems with large, open oesophageal ulcer with chronic ooze requiring intermittent transfusions, chronic infection with MRSA, requiring long term antibiotics, feeding via feeding gastrostomy tubes. The patient is stable 12 months after presentation. Treatment of this otherwise fatal problem by covered stent has permitted survival benefit. However, there are significant, unresolved issues of oesophageal ulcer and ongoing MRSA infection. Copyright (2002) Blackwell Science Pty Ltd

[en] This study aims to examine the geo system , the physiology and the geomorphology of the risk areas in public housing of Joao Paulo formation. This formation was built on a small plateau on a series of valleys, where are occupied by houses and passageways of different levels of infrastructure. There is a predominance of a yellow soil with a high level of weathering as well as a little vegetation. These characteristics associated with high rainfall and lack of infrastructure contribute to generate different type of soils

[en] We report on fluctuation magnetoconductivity measurements in a granular sample of GdBa₂Cu₃O_7-δ. The experiments show that the resistive transition is a two-stage process in this sample. The pairing transition occurs at a higher temperature, where superconductivity is established in the grains. The critical thermodynamics for this transition is that of the 3D-XY universality class, with dynamic exponent z=1.5. At a lower temperature occurs the coherence transition, where the fluctuating phases of individual grains become long-range ordered and a zero resistance state sets in

[en] Gated, microchannel-plate-based (MCP) framing cameras have been deployed worldwide for 0.2--9 keV x-ray imaging and spectroscopy of transient plasma phenomena. For a variety of spectroscopic and imaging applications, the angular sensitivity of MCPs must be known for correctly interpreting the data. We present systematic measurements of angular sensitivity at discrete relevant photon energies and arbitrary MCP gain. The results can been accurately predicted by using a simple two-dimensional approximation to the three-dimensional MCP geometry and by averaging over all possible photon ray paths

No abstract available

[en] A 1-mm-square diamond photoconductive detector (PCD) has been installed on the LLNL Nova laser system, for use as a broadband soft x-ray power diagnostic. The PCD is installed behind an array of pinholes, which cast multiple, overlapping images of the source onto the diamond. This allows reduction of the x-ray intensity, to avoid saturation problems, while avoiding the spectral dependency of thin film filters. The diode current is read out on a 5 GHz bandwidth scope. The system is calibrated by comparison to an absolutely calibrated array of filtered vacuum x-ray photodiodes ('dante'). The time response of the PCD and its bias electronics have been characterized using the 5th harmonic (210 nm) of a short pulse (<1 ps) Ti: sapphire laser. The data show a fast rise, limited by the 5 GHz scope bandwidth, and a slower fall off, characterized by an RC time of order 200 ps. copyright 1999 American Institute of Physics

[en] Extensive spectroscopic observations of Nova Cen 1986 obtained at different evolutionary phases of the event are reported. A reddening E(B-V) = 0.54 mag and a distance of 1.4 + or - 0.2 kpc are derived for the nova. The physical conditions and ionic abundances in the ejecta are also estimated. Helium, nitrogen, and oxygen are overabundant with respect to the solar values, but iron is normal. The expansion velocity is about 1400 km/s, and the total ejected mass is about 0.00003 solar mass. 24 refs