The cosmic X-ray experiment aboard HEAO-1

The HEAO-1 A-2 experiment, designed to study the large scale structure of the galaxy and the universe at X-ray energies is described. The instrument consists of six gas proportional counters of three types nominally covering the energy ranges of 0.15-3 keV, 1.2-20 keV, and 2.5-60 keV. The two low energy detectors have about 400 sq cm open area each while the four others have about 800 sq cm each. Dual field of view collimators allow the unambiguous determination of instrument internal background and diffuse X-ray brightness. Instrument characteristics and early performance are discussed

Measurement of the Top Quark p T Distribution

We have measured the p(T) distribution of top quarks that are pair produced in p (p) over bar collisions at roots = 1.8 TeV using a sample of t (t) over bar decays in which we observe a single high-P-T charged lepton, a neutrino, and four or more jets. We use a likelihood technique that corrects for the experimental bias introduced due to event reconstruction and detector resolution effects. The observed distribution is consistent with the standard model prediction. We use these data to place limits on the production of high-p(T) top quarks suggested in some models of anomalous top quark pair production

Appraisal of surgical treatment of 47 cases of patellofemoral instability Avaliação do tratamento cirúrgico da instabilidade fêmoro-patelar em 47 casos

INTRODUCTION: Patellofemoral instability is a common knee disease. Its etiology is complex and variable, with many components making different contributions in each individual, resulting in several distinct clinical presentations. Our goal was to analyze the results of surgical treatment in our hospital over a period of 10 years. PATIENTS AND METHODS: We analyzed 55 knees of 47 patients who underwent surgery for patellofemoral instability and were classified into 2 main groups: proximal realignment and combined proximal and distal realignment. Three other groups were analyzed according to the duration of preoperative symptoms: less than 1 year (group I); 1 to 10 years (group II); and more than 10 years (group III). RESULTS: There were 62% good results overall, with 78% good results in groups I and II. Group III had 81% bad results, showing that a late diagnosis of advanced disease results in a poor prognosis. In addition to late diagnosis, bad results were usually associated with incorrect diagnosis or choice of surgical technique. There was no significant difference between isolated proximal realignment and combined proximal and distal realignment in groups I or II, but in group III, the combined technique yielded better results. DISCUSSION: Our results indicate that patellofemoral instability should be addressed in its early stages. Patients with long-lasting symptoms or more severe disease seem to achieve better results with combined techniques. CONCLUSION: Proximal and distal realignments produce better results than isolated proximal realignment in patients with joint degeneration or with greater duration of disease. The realignment surgery does not produce good results in patients with advanced disease.<br>A instabilidade fêmoro-patelar (IFP) é patologia freqüente cuja etiologia é complexa e variável com diversos componentes cuja importância varia em cada indivíduo, resultando em diversas apresentações clínicas. Nosso objetivo foi analisar os resultados do tratamento cirúrgico em um período de 10 anos. MATERIAL E MÉTODO: Nós analisamos 55 joelhos de 47 pacientes operados por IFP em dois grupos principais: realinhamento proximal e realinhamento proximal e distal. Três outros grupos de acordo com a duração dos sintomas: <1 ano (grupo I); entre 1 e 10 (grupo II); e >10 anos (grupo III). RESULTADOS: Obtivemos 62% de bons resultados globalmente e 78% de bons resultados nos grupos I e II. O grupo III apresentou 81% de maus resultados, demonstrando que a indicação tardia não é boa. Os maus resultados, além do já mencionado, estavam em geral associados a erros diagnósticos ou de escolha de técnica cirúrgica. Não houveram diferenças significantes entre os resultados do realinhamento proximal isolado e do realinhamento proximal e distal combinados nos grupos I e II mas no grupo III o realinhamento combinado apresentou melhores resultados. DISCUSSÃO: Nossos resultados indicam que a instabilidade fêmoro-patelar deve ser tratada na fase inicial. Nos casos de longa evolução e nos casos mais graves, o realinhamento proximal e distal tem melhores resultados. CONCLUSÃO: O realinhamento proximal e distal tem melhor resultado que o realinhamento proximal isolado em pacientes com alterações degenerativas e naqueles com longa evolução. A operação de realinhamento não apresenta bons resultados nos casos de doença avançada