Biomedical subjects

A D Oliveira

Publications and source records attributed to A D Oliveira.

4 recordsLinked to original sources

PubMed2005

Comparison of deterministic and Monte Carlo methods in shielding design.

In shielding calculation, deterministic methods have some advantages and also some disadvantages relative to other kind of codes, such as Monte Carlo. The main advantage is the short computer time needed to find solutions while the disadvantages are related to the often-used build-up factor that is extrapolated from high to low energies or with unknown geometrical conditions, which can lead to significant errors in shielding results. The aim of this work is to investigate how good are some deterministic methods to calculating low-energy shielding, using attenuation coefficients and build-up factor corrections. Commercial software MicroShield 5.05 has been used as the deterministic code while MCNP has been used as the Monte Carlo code. Point and cylindrical sources with slab shield have been defined allowing comparison between the capability of both Monte Carlo and deterministic methods in a day-by-day shielding calculation using sensitivity analysis of significant parameters, such as energy and geometrical conditions.

Algorithms↗

PubMed2005

Photon track evolution.

Given the time scale of biological, biochemical, biophysical and physical effects in a radiation exposure of living tissue, the first physical stage can be considered to be independent of time. All the physical interactions caused by the incident photons happen at the same starting time. From this point of view it would seem that the evolution of photon tracks is not a relevant topic for analysis; however, if the photon track is considered as a sequence of several interactions, there are several steps until the total degradation of the energy of the primary photon. We can characterise the photon track structure by the probability p(E,j), that is, the probability that a photon with energy E suffers j secondary interactions. The aim of this work is to analyse the photon track structure by considering j as a step of the photon track evolution towards the total degradation of the photon energy. Low energy photons (<150 keV) are considered, with water phantoms and half-extended geometry. The photon track evolution concept is presented and compared with the energy deposition along the track and also with the spatial distribution of the several steps in the photon track.

Algorithms↗

PubMed2000

[Sport as integration factor of the physically handicapped in our society].

The objective of this study was to make use of sports as a rehabilitation method, as well as to assess the physical, psychological, and social aspects of those present some physical handicap, particularly those who have some kind of chronic disease and are no longer taking part in any rehabilitation program. Thirty handicapped people were evaluated: fifteen started with basketball and fifteen with swimming, according either to the specific preference of each one of them or to the degree and kind of physical impairment. They were submmited to the following evaluations: clinical examination, physiotherapy assessment, social interview and use of the Rivermead Social Scale, functional classification of the sport, use of the Barthel and Rivermead Functional Scales, and the psychological profile test (POMS). After two years, no relevant change in the moving evolution of the athletes were reported. Concerning the POMS psychological test, both basketball and swimming groups presented with high vigor and low depression levels. Considering the social aspects, both groups presented substantial improvement, specially regarding their relationship to one person or more people and also in the everyday activities (be it social, leisure, or domestic), thus leading them to better social integration. This essay shows that sport can bring people who are physically impaired a better social integration and physical conditions.

Adolescent↗

PubMedDate not supplied

[Blood pressure in school children and adolescents - The Belo Horizonte study]

OBJECTIVE: To investigate epidemiological aspects of blood pressure (BP) levels, and the prevalence of arterial hypertension in a representative sample of the whole elementary and high school population of the city of Belo Horizonte (state of Minas Gerais, southeastern Brazil). To describe the blood pressure levels found and the prevalence of BP levels above the 90th and 95th percentiles in the first and second measurements. To evaluate prevalence using four different normality references separately to assess the impact of choice of reference. To study the frequency at which the studentś blood pressure has been evaluated.METHODS: In an observational cross-sectional epidemiological study, we studied a sample of 1005 students, aged 6 to 18 year, randomized from an universe of 486,166 students from the 521 public and private elementary and high schools in the city. Each student was evaluated by means of a personal interview, anthropometric measurements, and two blood pressure measurements in a single visit and at a 10-minute interval.RESULTS: The systolic and diastolic blood pressure levels, by age and gender, were slightly lower than those described by the Task Force Report (1987) and by Rosner et al. (1993). The prevalence of BP levels (systolic or diastolic) over the 95th percentile were, according to the reference used: 8.7% - Task Force Report (1987); 5.5% - Rosner et al. (1993); 6.5% - Update on the Task Force Report (1996); and 9.8% - the 95th percentile from our own study. In the second measurement these prevalence rates dropped to 4.9%; 2.4%; 3.5% and 5.8%, respectively.CONCLUSIONS: We present a detailed description (mean values and standard deviations, and the 90th, 95th and 99th percentiles by age and gender) of the BP levels found in both measurements. Mean values and upper percentiles found in this study are very close to those found in the American references, which validates the current use of these references in Brazil. The prevalence of 9.0% of BP levels above the 90th percentile in two measurements made at random hints at the number of children who should be monitored for hypertension, and reinforces the importance of routine evaluation of blood pressure at every pediatric examination.

Journal Article↗