A note on the Moody diagram

In this work we propose an alternate scaling for the head loss in the steady flow of Newtonian fluids through tubes. The characteristics of the proposed scaling render more clear the role of inertia in this flow and ensure that the trends of the relationship between dimensionless quantities are the same ones observed in the dimensional problem.Comment: 5 pages, 2 figure

Irreversible time-dependent rheological behavior of cement slurries : constitutive model and experiments

Over the last few decades, much focus has been given to investigating the reversible rheological behavior of thixotropic materials, but the description of the rheology of materials undergoing an irreversible process is still challenging. In this work, the time-dependent rheological behavior of a cement slurry is investigated. Different rheometric experiments are performed to evaluate the structure breakdown under shear, cement gelation, and curing process. A recently proposed thixotropic elasto-viscoplastic model [de Souza Mendes, Soft Matter 7, 2471-2483 (2011)] is modified to account for irreversible effects, which can be either of a chemical or physical nature, making the current model capable of describing reversible and irreversible processes with a single structure parameter. The parameters of the model are estimated from constant shear rate tests and from the flow curve of the fresh cement slurry. The model predictions are compared to step-down and step-up in stress experiments, and the results show that the model successfully describes experimental data obtained. Interesting phenomena are observed and discussed, including (i) thixotropic behavior during the dormant period, (ii) shear banding, (iii) irreversible changes in cement slurry rheology after the hydration reactions accelerate, and (iv) the existence of a characteristic time for the transition from a thixotropic-yield-stress material to a solid during curing. The predictive capability of the new model includes bifurcation, shear banding, stress overshoots, effects of chemical reactions, and irreversible shear degradation. It is argued that the ideas employed in the present work can be used to incorporate irreversible effects into other thixotropic models, giving rise to the possibility of describing the transient rheological behavior of complex materials in an unprecedented fashion. (c) 2019 The Society of Rheology

Quality of life in liver transplant recipients and the influence of sociodemographic factors

Abstract OBJECTIVE To verify the influence of sociodemographic factors on the quality of life of patients after liver transplant. METHOD Cross-sectional study with 150 patients who underwent liver transplant at a referral center. A sociodemographic instrument and the Liver Disease Quality of Life questionnaire were applied. The analysis of variance (ANOVA) was performed, as well as multiple comparisons by the Tukey test and Games-Howell tests when p <0.05. RESULTS Old age had influence on domains of symptoms of liver disease (p = 0.049), sleep (p = 0.023) and sexual function (p = 0.03). Men showed better significant mean values than women for the loneliness dimension (p = 0.037). Patients with higher educational level had higher values for the domain of stigma of liver disease (p = 0.014). There was interference of income in the domains of quality of social interaction (p = 0.033) and stigma of the disease (p = 0.046). CONCLUSION In half of the quality of life domains, there was influence of some sociodemographic variable

A New Approach for Heparin Standardization: Combination of Scanning UV Spectroscopy, Nuclear Magnetic Resonance and Principal Component Analysis

The year 2007 was marked by widespread adverse clinical responses to heparin use, leading to a global recall of potentially affected heparin batches in 2008. Several analytical methods have since been developed to detect impurities in heparin preparations; however, many are costly and dependent on instrumentation with only limited accessibility. A method based on a simple UV-scanning assay, combined with principal component analysis (PCA), was developed to detect impurities, such as glycosaminoglycans, other complex polysaccharides and aromatic compounds, in heparin preparations. Results were confirmed by NMR spectroscopy. This approach provides an additional, sensitive tool to determine heparin purity and safety, even when NMR spectroscopy failed, requiring only standard laboratory equipment and computing facilities

Erratum to: The study of cardiovascular risk in adolescents – ERICA: rationale, design and sample characteristics of a national survey examining cardiovascular risk factor profile in Brazilian adolescents

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