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R T Rodrigues

Publications and source records attributed to R T Rodrigues.

6 recordsLinked to original sources
PubMed2001

Optimizing dissolved air flotation design and saturation.

Dissolved air flotation (DAF) of iron hydroxide precipitates at working pressures lower than 3 atm, using modified flotation units to improve the collection of fragile coagula, was studied. Conventional DAF flotation was studied as a function of saturation pressure in the absence and presence of surfactants in the saturator. Without surfactants, the minimum saturation pressure required for DAF to occur was found to be 3 atm. But, by lowering the air/water surface tension in the saturator, DAF was possible at a saturation pressure of 2 atm. This behavior was found to occur in both batch and pilot DAF operation tests and almost complete recovery of the precipitates was attained. Results are explained in terms of the minimum "energy" which has to be transferred to the liquid phase to form bubbles by a cavity phenomenon. Further, studies were conducted changing equipment design and feed bubbles size distribution (mixing micro and "mid-sized" bubbles). Thus, bubbles entrance position in the collision-adhesion zone ("capture" zone) was compared to bubble entrance position in the water flow inlet below the floating bed. A "mushroom" type diffuser was used for the "capture zone" experiment and better performance was obtained. Results are explained in terms of different mass transfer phenomena in the collection zone and in the separation zone. Finally, results obtained with the use of a column flotation cell working as normal DAF and with a wide bubble size range are presented. Results indicate good performance and some gains in process kinetics with middle size bubbles.

Air↗
PubMed1993

Additive effects of exposure to silica dust and smoking on pulmonary epithelial permeability: a radioaerosol study with technetium-99m labelled DTPA.

BACKGROUND: Increased pulmonary epithelial permeability evaluated by the rate of clearance from lung to blood of the radioaerosol solute technetium-99m labelled diethylenetriamine pentaacetate (99mTc-DTPA) has been reported in smokers and in workers exposed to silica dust. A study was carried out to determine whether there are additive effects of cigarette smoke and exposure to silica dust on clearance rates of 99mTc-DTPA in ceramic workers. METHODS: Thirty one subjects with silicosis were studied, of whom 18 smoked cigarettes and 13 were non-smokers. They had similar histories of exposure to silica dust, and radiological alterations consistent with silicosis. The results from these patients were compared with those from normal subjects and smokers previously studied by the authors. RESULTS: Pulmonary function values were normal in most patients and not significantly different among groups. The median (range) rate of clearance of 99mTc-DTPA in smokers with silicosis was 4.1 (1.9-12.7) %/minute, which was higher than the rates in non-smoking patients with silicosis of 2.2 (1.1-6.6) %/minute and in smokers without exposure to silica dust of 2.9 (1.6-4.5) %/minute. These differences were more evident and significant when the clearance rates of the lower lobes of the three groups were compared. Clearance rates higher than 3%/minute were much more frequent in smokers with silicosis (85%) than in non-smoking patients with silicosis (15%) and in smokers (40%). CONCLUSION: In ceramic workers with radiographic changes resulting from exposure to silica dust, there is an additive effect of inhalation of silica dust and cigarette smoking on clearance rates of 99mTc-DTPA.

Adult↗
PubMed1993

[Daily and weekly circadian variations in sudden death in Chagas disease].

PURPOSE: To determinate the circadian daily and weekly variations in the incidence of sudden death due to Chagas' disease. METHODS: In 50 chronic chagasic individuals with sudden death due to Chagas' disease and in 473 individuals with natural, not sudden death, we analyzed both the day of the week and the time of the death. Statistical tests were applied to determine the significance of the difference between proportions and averages. RESULTS: For the chagasic group the values indicated a highly significant excess of lethality for the period between 12 and 6pm. The occurrence of the sudden death was the same in the different days of the week for both groups. CONCLUSION: The observed results suggest that the sudden death associated with Chagas' disease has a circadian pattern with a vespertine peak. Weekly variations in the sudden death of chronic chagasic individuals were not detected.

Adolescent↗
PubMedDate not supplied

[Asbestos-related pleuropulmonary diseases: pictorial essay].

Pleural and pulmonary asbestos-related diseases range from benign conditions, like pleural effusion and pleural plaques, to some neoplasias, such as lung cancer and malignant mesothelioma. Pleural effusion is the earliest finding after asbestos exposure, but the imaging findings are not specific. Diffuse pleural thickening involves the visceral pleura and pleural plaques are considered to be hallmarks of exposure. Asbestosis is the pulmonary fibrosis due to asbestos. Rounded atelectasis is a peripheral lung collapse in these individuals, generally related to pleural disease. Some neoplasias, like lung carcinoma and pleural mesothelioma, are more prevalent in asbestos-exposed subjects. The aim of this essay is to illustrate the main imaging findings of asbestos-related diseases.

Asbestos↗
PubMedDate not supplied

[Asbestos-related pleural plaques: a literature review].

Pleural plaques (PP) are considered to be hallmarks of asbestos exposure. They constitute focal thickenings of the pleura and are commonly seen in patients without lung disease. They can involve parietal, diaphragmatic and mediastinal pleura. Chest x-ray is frequently used for PP diagnosis, but computed tomography, especially when used the high-resolution technique, is the imaging exam with the greatest sensibility and specificity. PP are almost always asymptomatic, but there are some controversial about their relationship with asbestos exposure indexes, pulmonary functional alterations and risk of neoplasias.

Asbestos↗