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a b s t r a c tExperiments were performed in a laboratory scale bubble column (10 L), to investigate the pH influence on oxygen mass transfer coefficient, in order to achieve a better control of biological processes. The liquid-side mass transfer coefficient, k L , and the specific interfacial area, a, were studied individually. The specific interfacial area was obtained using the new automatic image analysis technique developed by Ferreira et al. (2012). The pH was changed by the addition to the system of the most common acids and base used in biological process: hydrochloric acid (HCl), phosphoric acid (H 3 PO 4 ) and potassium hydroxide (KOH). The results show that aqueous systems containing HCl, H 3 PO 4 or KOH present lower volumetric liquid side mass transfer coefficient, k L a, in relation to pure systems (distilled water), this decrease being not linear. It was found that the specific interfacial area presents higher values in KOH and HCl solutions in comparison with distilled water. However, an opposite behavior was observed in the liquid-side mass transfer coefficient values. The k L behavior on the impure systems was explained based on bubble surface contamination. Higbie's and Fröessling's equations were adapted in the present work in order to be used in bubble dispersion systems.

ObjectiveThe aim of this study was to evaluate the diagnostic accuracy of FNA and analyse its efficacy in enabling the initiation of treatment in musculoskeletal tumours.MethodsA total of 130 FNA were performed (94 bone and 36 soft tissue lesions) guided by CT scan (n = 64), ultrasonography (n = 36) and radioscopy (n = 30). Diagnostic yield and accuracy were evaluated. A diagnosis was considered accurate when confirmed by histology or ulterior clinical/imaging evaluation. Exclusion of malignancy or infection was considered as diagnoses.ResultsNinety diagnoses (69.2%) were obtained: 87 (96.7%) were accurate and 3 were wrong. FNA was non-diagnostic in 40 cases (30.8%) but in 15 (11.5%) it has been possible to conclude if the lesion was malignant (n = 6) or benign (n = 9). This method was completely inconclusive in 25 cases (19.2%).ConclusionDespite the low diagnostic yield, accuracy was high. FNA allowed the initiation of treatment in all 87 patients with a correct diagnosis and in 9 in which malignancy was excluded. Two of the 6 biopsies with the information of malignancy were soft tissue lesions. Even here, treatment could be done, as the majority of soft tissue sarcoma protocols begin with surgery. This study validates FNA as a method with a high diagnostic accuracy.