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Aiming for the introduction of stability requirements in nanofluids processing, an interface-based three-step method is proposed in this work. It is theory-based design framework for nanofluids that aims for a minimum tension at the solid-liquid interface by adjusting the polar and dispersive components of the base fluid to meet those of disperse nanomaterial. The method was successfully tested in the preparation of aqueous nanofluids containing single-walled carbon nanotubes that resulted to be stable and to provide good thermal properties, i.e. thermal conductivity increases by 79.5% and isobaric specific heat by 8.6% for a 0.087 vol.% load of nanotubes at 70 °C. Besides, a system for these nanofluids was modelled. It was found to be thermodynamically consistent and computationally efficient, providing consistent response to changes in the state variable temperature in a classical Molecular Dynamics environment. From an analysis of the spatial components of the heat flux autocorrelation function, using the equilibrium approach, it was possible to elucidate that heat conduction through the host fluid is enhanced by phonon propagation along nanotubes longitudinal axes. From an analysis of the structural features described by radial distribution functions, it was concluded that additional heat storage arises from the hydrophobic effect.
RESUMO
AIM: The prevalence of cardiovascular autonomic neuropathy (CAN) in diabetes mellitus is well documented. However, the rate and predictors of both the development and progression of CAN have been less studied. Hereby, we assessed the rate and the major risk factors for CAN initiation and progression in a cohort of type 1 diabetic patients followed over a three-year period. METHODS: 175 type 1 diabetic patients (mean age: 50 ± 11 years; female/male: 76/99) with positive bedside screening for CAN were included and underwent 2 standardized autonomic testings using 4 standardized tests (deep breathing, Valsalva maneuver, 30/15 ratio, and changes in blood pressure during standing), separated by 3 ± 1 years. CAN staging was achieved according to the Toronto Consensus Panel on Diabetic Autonomic Neuropathy into 4 categories: absent, possible, confirmed, or severe CAN. RESULTS: Out of the 175 patients included, 31.4% were free of CAN, 34.2% had possible CAN, 24.6% had confirmed CAN, and 9.7% exhibited severe CAN at the first assessment. Among the 103 patients with nonsevere CAN at inclusion, forty-one (39.8%) had an increase of at least one category when reassessed and 62 (60.2%) remained stable. A bivariate analysis indicated that only BMI and exposure to selective serotonin reuptake inhibitors (SSRIs) were significantly different in both groups. A multivariate analysis indicated that lower BMI (OR: 0.15, CI 95%: 0.05-0.48, p = 0.003) and SSRI exposure (OR: 4.18, CI 95%: 1.03-16.97, p = 0.04) were the sole predictors of CAN deterioration. In the 55 patients negative for CAN at the first laboratory assessment, 12 became positive at the second assessment. CONCLUSION: No clear predictive factor for CAN onset was identified. However, once present, CAN progression was related to low BMI and SSRI exposure.
