Studies of the exhaust products from solid propellant rocket motors

This study was undertaken to determine the feasibility of conducting environmental chamber tests on the physical processes which occur when a solid rocket motor exhaust mixes with the ambient atmosphere. Of particular interest was the interaction between hydrogen chloride, aluminum oxide, and water vapor. The program consisted of three phases: (1) building a small rocket motor and using it to provide the exhaust species in a controlled environment; (2) evaluating instruments used to detect and measure HCl concentrations and if possible determining whether the HCl existed in the gaseous state or as an acid aerosol; (3) monitoring a series of 6.4-percent scale space shuttle motor tests and comparing the results to the environmental chamber studies. Eighteen firings were conducted in an environmental chamber with the initial ambient relative humidity set at values from 29 to 100 percent. Two additional firings were made in a large shed, and four were made on an open concrete apron. Six test firings at MSFC were monitored, and the ground level concentrations are reported. Evidence is presented which shows that the larger Al2O3 (5 to 50 micrometers) particles from the rocket motor can act as condensation nuclei. Under appropriate ambient conditions where there is sufficient water vapor this results in the formation of an acid aerosol. Droplets of this acid were detected both in the environmental chamber and in the scaled shuttle engine tests

Scene simulation for passive IR systems

The development of large mosaic detector arrays will allow for the construction of staring long wave infrared (LWIR) sensors which can observe large fields of view instantaneously and continuously. In order to evaluate and exercise these new systems, it will be necessary to provide simulated scenes of many moving targets against an infrared clutter background. Researchers are currently developing a projector/screen system. This system is comprised of a mechanical scanner, a diffuse screen, and a miniature blackbody. A prototype of the mechanical scanner, which is comprised of four independently driven scanners, has been designed, fabricated, and evaluated under room and cryogenic vacuum conditions. A large diffuse screen has been constructed and tested for structural integrity under cryogenic/vacuum thermal cycling. Construction techniques have been developed for the fabrication of miniature high-temperature blackbody sources. Finally, a concept has been developed to use this miniature blackbody to produce a spectrally tailorable source

La reconstrucción histórica en el "Revisionismo" de David Irving

En este trabajo se plantea, más allá de examinar las tesis principales del "revisionismo", la propia naturaleza del conocimiento histórico. ¿Son válidas todas las interpretaciones de un hecho histórico? ¿Se trata en tales casos de "otra lectura", de una "versión alternativa", es decir, de otra apreciación de los datos disponibles? ¿Cómo saber cuando hay mala interpretación deliberada o falsificación de la evidencia? ¿Puede detectarse si la argumentación tendenciosa es deshonesta? El "revisionismo histórico" se ha definido a sí mismo como una corriente historiográfica que ofrece otra versión de Hitler y su régimen. Cerca de una veintena de autores, desde los años cuarenta del siglo XX, se adscriben en esta tendencia, algunos de los cuales han desplegado una sostenida actividad y han logrado una llamativa repercusión en los medios de difusión. Este es el caso de David Irving. Autor de más de treinta libros, artículos, conferencias y discursos dedicados al III Reich, ha pasado largos años de su vida rastreando y estudiando archivos alemanes. Pero muy lejos de constituir un nuevo enfoque historiográfico del nazismo, el "revisionismo" de David Irving está imbuido de política e ideología y sus métodos de trabajo incluyen la adulteración y la distorsión intencional de la historia.Beyond the main theses of the so called "revisionism", this essay considers the specific nature of historical knowledge. Are all interpretations of an historic fact valid? In those cases, are we talking about "a different reading", in other words, an "alternative version", another way to weigh the given data? How can we know if we are confronted by a deliberate misinterpretation or forgery of the evidence? Can we detect if a biased argumentation is dishonest? "Historic revisionism" has defined itself as a historiographic current that presents a different vision of Hitler and his regime. About twenty authors, beginning in the 1940s, adscribe to this school, and sorne of them have developed a continous activity, getting considerable echo in the media. This is the case of David Irving. Author of more than thirty books, articles, conferences and speeches dealing with the Third Reich, he has invested long years of his life researching and studying German archives. But far from producing a new historiographic approach of Nazism, David Irving's "revisionism" is overburdened with politics and ideology, and his methods include forgery and the intentional distorsion of the historical record.Fil: Dawbarn, Susana. Universidad Nacional de Cuyo. Facultad de Filosofía y Letras. Instituto Multidisciplinario de Estudios Sociales Contemporáneo

A study of re-evaporation nuclei

Classical considerations of the evaporation of a homogeneously nucleated droplet in an atmosphere of low humidity, indicates complete evaporation of the drop. Experimental results however, show that there is left behind a residual nucleus that is quite stable. Condensation occurs on these nuclei at comparatively low supersaturations. Using a specially instrumented cloud chamber, experimental procedures are described which attempt to investigate some of the properties of these nuclei. Various possibilities causing this stability are examined and compared to the experimental results obtained --page [ii]

Infrared sensor test methodology and facilities

As the Air Force Systems Command designated Center of Expertise for Space Simulation Testing, AEDC has defined a test methodology for the ground testing of infrared sensor systems. This test methodology and the test facilities envisioned to implement it has been addressed in another report. The progress on the implementation of that test methodology is reported and the status of the test facilities presently existing or under construction to implement it is described

El fin del último Imperio Euroasiático : el estado soviético y las repúblicas musulmanas : (tercera Parte)

Fil: Dawbarn, Susana. Universidad Nacional de Cuyo. Facultad de Filosofía y Letra

Los judíos alemanes frente a la persecución nazi : (1933-Septiembre 1939)

Parte de un proyecto de investigación más amplio -que explora las continuidades y rupturas entre el nazismo y el antisemitismo alemán -este trabajo apunta a rastrear las actitudes judías ante los atropellos del régimen nazi. Antes de la etapa del genocidio metódico, la comunidad judía alemana fue objeto de una progresiva radicalización de la violencia y exclusión implementadas por el régimen nazi. A través de una nutrida selección documental, hemos podido visualizar los obstáculos- propios y externos-, detectar sus temores e ilusiones, y explicar así. su dispar reacción. Desde este ángulo de análisis que se centra en el universo de las víctimas, afloran nuevas perspectivas para examinar la política de los perpetradores y se refuerzan los enfoques que subrayan el papel decisivo de Hitler y de sus premisas ideológicas. Sus iniciativas y las de sus allegados más firmes, tácticamente condicionadas por las presiones domésticas e internacionales, se respaldaron en una fuerte tradición antisemita. Pero rebasado por la violencia del régimen, ese antisemitismo derivó en un terrorismo de Estado que hizo de la purificación racial el principal cometido de la política interna y externa.Fil: Dawbarn, Susana. Universidad Nacional de Cuyo. Facultad de Filosofía y Letra

The Neurotrophins and Their Role in Alzheimer’s Disease

Besides being essential for correct development of the vertebrate nervous system the neurotrophins also play a vital role in adult neuron survival, maintenance and regeneration. In addition they are implicated in the pathogenesis of certain neurodegenerative diseases, and may even provide a therapeutic solution for some. In particular there have been a number of studies on the involvement of nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) in the development of Alzheimer’s disease. This disease is of growing concern as longevity increases worldwide, with little treatment available at the moment to alleviate the condition. Memory loss is one of the earliest symptoms associated with Alzheimer’s disease. The brain regions first affected by pathology include the hippocampus, and also the entorhinal cortex and basal cholinergic nuclei which project to the hippocampus; importantly, all these areas are required for memory formation. Both NGF and BDNF are affected early in the disease and this is thought to initiate a cascade of events which exacerbates pathology and leads to the symptoms of dementia. This review briefly describes the pathology, symptoms and molecular processes associated with Alzheimer’s disease; it discusses the involvement of the neurotrophins, particularly NGF and BDNF, and their receptors, with changes in BDNF considered particularly in the light of its importance in synaptic plasticity. In addition, the possibilities of neurotrophin-based therapeutics are evaluated