Self- and mutual diffusion coefficient equation for pure fluids, liquid mixtures and polymeric solutions

Transport properties are important information not only for industrial equipment design but also for many research areas. While there is a well-developed theory for gases at low densities, there is no established theory to calculate diffusion coefficients for dense fluids, especially for polymeric solutions. Recently, a database of 96 self-diffusion coefficient data points were obtained from molecular dynamics (MD) simulations for freely jointed Lennard-Jones chains (LJC) with lengths of 2, 4, 8 and 16 at reduced densities ranging from 0.1 to 0.9 and in the reduced temperature interval of 1.5 to 4. These data were used to develop an equation that correlates MD self-diffusion coefficient points with an overall absolute average deviation of 15.3%. The aim of this work is to show that this equation can be used to calculate diffusivities of pure liquids and liquid mixtures, including polymeric solutions. The proposed equation is used for correlating self-diffusion coefficients for 22 pure real substances and then for predicting mutual diffusion coefficients for 12 binary liquid mixtures. The proposed equation is also used to calculate mutual diffusion coefficients for polymeric systems as: polystyrene-toluene at 110 °C, poly(vinyl acetate)-toluene at 35 °C, and poly(vinyl acetate)-chloroform at 35 and 45 °C. Results show that the model developed here seems to be a promising approach for correlating mutual diffusion coefficients not only for small-molecule systems but also for polymer-solvent systems. One advantage of the equation proposed here is that the parameters have physical meaning and most of them can be estimated without any information on binary diffusion data.     

Study of Residual Stresses on Cold-Forming Metals Using Stress Corrosion

Residual stresses are frequently evaluated using two types of tests: destructive and non-destructive. The most common type of non-destructive test examines the relationship between physical parameters measured by X-ray diffraction. This technique requires a small sample size and a planar surface. In metal forming, the geometry of different pieces is complex, and most of the surfaces are curved. This work utilizes an indirect method to evaluate the residual stresses present in the cold forming of non-flat metal surfaces using a corrosion test in the deformation region. Samples from AISI 1045 steel were cold bent to angles of 150°, 120°, 90°, and 45°. The samples were then subjected to a corrosion test to evaluate the potential difference (PD) and the results were compared to those of an unbent sample. The bending process was simulated by finite element method that revealed the intensity and nature of residual stresses in the samples. The results were statistically treated and demonstrate that the PD depends on the bending angle and exposition time to the corrosive medium but is independent of the corrosive medium. We conclude that it is possible to evaluate the residual stresses on cold-forming metal parts with complex geometries using a corrosion test.     

Dendritic Arm Spacing Affecting Mechanical Properties and Wear Behavior of Al-Sn and Al-Si Alloys Directionally Solidified under Unsteady-State Conditions

Alloys of Al-Sn and Al-Si are widely used in tribological applications such as cylinder liners and journal bearings. Studies of the influence of the as-cast microstructures of these alloys on the final mechanical properties and wear resistance can be very useful for planning solidification conditions in order to permit a desired level of final properties to be achieved. The aim of the present study was to contribute to a better understanding about the relationship between the scale of the dendritic network and the corresponding mechanical properties and wear behavior. The Al-Sn (15 and 20 wt pct Sn) and Al-Si (3 and 5 wt pct Si) alloys were directionally solidified under unsteady-state heat flow conditions in water-cooled molds in order to permit samples with a wide range of dendritic spacings to be obtained. These samples were subjected to tensile and wear tests, and experimental quantitative expressions correlating the ultimate tensile strength (UTS), yield tensile strength, elongation, and wear volume to the primary dendritic arm spacing (DAS) have been determined. The wear resistance was shown to be significantly affected by the scale of primary dendrite arm spacing. For Al-Si alloys, the refinement of the dendritic array improved the wear resistance, while for the Al-Sn alloys, an opposite effect was observed, i.e., the increase in primary dendrite arm spacing improved the wear resistance. The effect of inverse segregation, which is observed for Al-Sn alloys, on the wear resistance is also discussed.     

Semantic Granularity in Ontology-Driven Geographic Information Systems

The integration of information of different kinds, such as spatial and alphanumeric at different levels of detail, is a challenge. While a solution is not reached, it is widely recognized that the need to integrate information is so pressing that it does not matter if detail is lost, as long as integration is achieved. This paper shows the potential for information retrieval at different levels of granularity inside the framework of information systems based on ontologies. Ontologies are theories that use a specific vocabulary to describe entities, classes, properties and functions related to a certain view of the world. The use of an ontology, translated into an active information system component, leads to ontology-driven information systems and, in the specific case of GIS, leads to what we call ontology-driven geographic information systems.     

Regionalization of the GOES-10 retrieval algorithm for tropical South America

Meteorological satellites provide a unique opportunity to obtain thermodynamic profiles in regions of the globe that do not have a dense meteorological upper-air station network, such as South America. Temperature and mixing ratio profiles were retrieved every hour with a spatial resolution of 10 km over South America from July 2007 to February 2009 using radiances from the Geostationary Operational Environmental Satellite 10 (GOES-10). The GOES-10 retrieval algorithm for thermodynamic profiles was developed by the Cooperative Institute for Mesoscale Meteorological Studies (CIMMS) in the USA, so some adjustments had to be made for its application on South America, such as the construction of a new covariance matrix. In this context, the scientific focus of this research was the construction of a new covariance matrix adapted to the meteorological conditions in South America. In addition, the algorithm results were validated by the use of the original and the new covariance matrices. The variables validated were air temperature, mixing ratio vertical profiles and total precipitable water (TPW). The data set used comprised a total of 1100 radiosonde observations recorded in the tropical region of South America at 00:00 and 12:00 Universal Time Clock (UTC), as well as thermodynamic profiles from 12 h forecasts from the Centre for Weather Forecast and Climate Studies's (CPTEC's) Global Model, used as a first guess, and upwelling radiances of 18 infrared channels from GOES-10 for the period from July to November 2007. In general, the results indicated that with the regionalization of the covariance matrix, the algorithm performed better retrievals than with that of the original matrix. The greatest improvements were found in the mixing ratio profiles and in the values of the TPW. These results could be associated with the presence of the Amazon rainforest, which incorporated a greater amount of moisture into the new covariance matrix than the previous had the previous one.     

Circulating Extracellular Vesicles: The Missing Link between Physical Exercise and Depression Management?

Depression is associated with an increased risk of aging-related diseases. It is also seemingly a common psychological reaction to pandemic outbreaks with forced quarantines and lockdowns. Thus, depression represents, now more than ever, a major global health burden with therapeutic management challenges. Clinical data highlights that physical exercise is gaining momentum as a non-pharmacological intervention in depressive disorders. Although it may contribute to the reduction of systemic inflammation associated with depression, the mechanisms underlying the beneficial physical exercise effects in emotional behavior remain to be elucidated. Current investigations indicate that a rapid release of extracellular vesicles into the circulation might be the signaling mediators of systemic adaptations to physical exercise. These biological entities are now well-established intercellular communicators, playing a major role in relevant physiological and pathophysiological functions, including brain cell–cell communication. We also reviewed emerging evidence correlating depression with modified circulating extracellular vesicle surfaces and cargo signatures (e.g., microRNAs and proteins), envisioned as potential biomarkers for diagnosis, efficient disease stratification and appropriate therapeutic management. Accordingly, the clinical data summarized in the present review prompted us to hypothesize that physical exercise-related circulating extracellular vesicles contribute to its antidepressant effects, particularly through the modulation of inflammation. This review sheds light on the triad “physical exercise–extracellular vesicles–depression” and suggests new avenues in this novel emerging field.     

Combined Impact of Magnetic Force and Spaceflight Conditions on Escherichia coli Physiology

Changes in bacterial physiology caused by the combined action of the magnetic force and microgravity were studied in Escherichia coli grown using a specially developed device aboard the International Space Station. The morphology and metabolism of E. coli grown under spaceflight (SF) or combined spaceflight and magnetic force (SF + MF) conditions were compared with ground cultivated bacteria grown under standard (control) or magnetic force (MF) conditions. SF, SF + MF, and MF conditions provided the up-regulation of Ag43 auto-transporter and cell auto-aggregation. The magnetic force caused visible clustering of non-sedimenting bacteria that formed matrix-containing aggregates under SF + MF and MF conditions. Cell auto-aggregation was accompanied by up-regulation of glyoxylate shunt enzymes and Vitamin B12 transporter BtuB. Under SF and SF + MF but not MF conditions nutrition and oxygen limitations were manifested by the down-regulation of glycolysis and TCA enzymes and the up-regulation of methylglyoxal bypass. Bacteria grown under combined SF + MF conditions demonstrated superior up-regulation of enzymes of the methylglyoxal bypass and down-regulation of glycolysis and TCA enzymes compared to SF conditions, suggesting that the magnetic force strengthened the effects of microgravity on the bacterial metabolism. This strengthening appeared to be due to magnetic force-dependent bacterial clustering within a small volume that reinforced the effects of the microgravity-driven absence of convectional flows.     

Culture Medium Evaluation Using Low-Cost Substrate for Biosurfactants Lipopeptides Production by Bacillus amyloliquefaciens in Pilot Bioreactor

Total biosurfactant production by Bacillus amyloliquefaciens IT45 was evaluated with different substrates concentrations in a culture medium. A central composite design (CCD) was developed to evaluate the influence of variables, including glucose syrup, yeast extract, and calcium chloride, on surface tension (ST), total biosurfactant production, and residual sugar (RS). As a result, the best observed results for ST, RS, and total biosurfactant production were 30 mN m⁻¹, 31%, and 5.5 g L⁻¹, respectively, after 48 h of fermentations carried out in batch operation process. Characterization of the biosurfactant identified the presence of surfactin. To validate the CCD experiments, fermentations were conducted in a 40 L pilot bioreactor. For this fermentation, the cellular growth was 3.0 × 10⁹ CFU mL⁻¹, surfactin production was 0.55 g L⁻¹, and RS was 28%. The results demonstrate that B. amyloliquefaciens IT45 has the potential to produce biosurfactants and does not require high concentrations of carbon and nitrogen sources for its development.