Modeling particle formation kinetics in mixed-phase clouds

A computational model for droplet and ice particle formation kinetics in mixed clouds is developed using the kinetic equations of condensation/coagulation formulated by Piskunov and Petrov (J. Aerosol Sci. 33 (2002) 647) for two-phase disperse systems. Alongside new kinetic equations, the model involves equations of mass and thermal balance, accounts for the difference in rates of vapor condensation above water and ice, uses actual condensation and coagulation growth rates, describes the phase transition dynamics.A method of x–T diagrams is suggested for visual treatment of the dynamics of condensation redistribution of material (distillation) from the water fraction to ice particles. The method allows easy graphic representation and study of the basic condensation process stages and prediction of the final state parameters. Criteria are found for the efficiency of methods for artificial action on a cloud system involving its seeding with ice-forming reagents, based on the effect of the redistibution of material.The developed numerical model is used for computation of the precipitation formation processes in the conditions of the Montana experiment of 07/19/1981 (J. Geophys. Res. 91 (01) (1986) 1231; J. Geophys. Res. 90 (D4) (1985) 60079).     

Stability of casein micelle subjected to reversible CO2 acidification: Impact of holding time and chilled storage

Casein micelle stability and reactivity were assessed on milk subjected to reversible acidification by carbonation. Pressurised CO₂ was injected at 4 °C, leading to controlled acidification from 6.63±0.02 to a target pH (5.5 or 5.2). After holding the pressurised milk under these conditions for 15 or 60 min, the pressure was released and the milk pH returned to its initial value under stirring and vacuum degassing. Upon CO₂ treatment, calcium and protein partition, zeta potential and size of casein micelles were restored directly after neutralisation. The rheological properties of the gel obtained by acid coagulation of CO₂-treated milk did not change as a result of carbonation. Micelle hydration increased after neutralisation and during storage. Milk buffering capacity in the pH range of 4.5–5.5 decreased after neutralisation of milk acidified by carbonation, but increased during chilled storage of this milk. Holding time of carbonated milk at low pH was found to have no impact on the physicochemical characteristics of casein micelles and the rheological properties of the gel obtained by acid coagulation of this milk.     

Thermal stability of plasminogen activators and plasminogen activation in heated milk

Thermal stabilities of bovine plasminogen (PG) activators, tissue and urokinase type (t-PA and u-PA), and their impact on activation of PG, were studied after application of various heating conditions (65, 75, 85, or 90 °C for 15, 20, or 30 s), in both milk and buffer systems. Both t-PA and u-PA were thermally stable in milk heated at ⩽75 °C. However, almost half of the t-PA activity and 30% of u-PA activity was lost after heating milk at 85 °C for 30 s. A lower heat stability of both t-PA and u-PA was observed in buffer than in milk. The decrease in level of PG was more pronounced than that of active plasmin in milk heated at ⩾85 °C for 30 s; however, the residual level of PG was considerably higher than the residual level of active PL. Overall, results indicated that u-PA plays a more significant role than t-PA in the activation of PG during storage of heated milk.     

Transglutaminase cross-linking of milk proteins and impact on yoghurt gel properties

A novel yoghurt process was investigated in which milk proteins were covalently cross-linked by a microbial transglutaminase (TG) preparation containing glutathione (TG+GSH). As unheated milk is normally less reactive towards TG, TG+GSH was applied to enable non-inhibited cross-linking without requiring a pre-heat treatment beyond pasteurisation conditions. After the TG+GSH incubation phase, the enzyme was inactivated by heat treatment of the yoghurt milk prior to fermentation. During yoghurt fermentation, no negative effect of TG+GSH on fermentation time was found. Protein cross-linking by TG+GSH was enhanced, resulting in higher apparent viscosity and a higher degree of protein polymerisation than that given by TG without GSH. Furthermore, different ratios of casein to whey proteins (CWP ratios) were used to investigate the effect of both protein fractions on covalently cross-linked yoghurt gel structures. The results showed a relationship between extent of cross-linking, apparent viscosity and CWP ratio of the yoghurt gels. During storage for up to 6 weeks at 4 °C, no changes in rheological properties and degree of protein polymerisation were measurable for stirred yoghurt gels prepared from cross-linked milk proteins.     

Visualisation of pyrite leaching by selected thermophilic archaea: Nature of microorganism–ore interactions during bioleaching

In this study, pyrite (FeS₂) was leached by Acidianus brierleyi, Metallosphaera sedula and Sulfolobus metallicus during a 60 day experimental period. Leaching occurred over a redox potential range of 800 to 860 mV (S.H.E.) and in the presence of increasing Fe³⁺ levels. A modified ferrozine assay was developed to detect the increase of iron in solution as bioleaching of the ore progressed. For the first time, the interactions of these extreme thermophiles with the metal sulfide ore particles were extensively documented using SEM and TEM. As the pyrite degraded, there appeared to be a progression of deposited structures forming, ranging from sub-micron precipitates and disc-shaped structures on the ore's surface, which ultimately were similar for all leaching cultures. Furthermore, the residues resulting from the leaching of pyrite by M. sedula, the most active thermophile, were characterised using SEM/EDX, and appeared to be dominated by iron sulfate precipitates. The nature of the deposits formed, together with our other results, indicate that A. brierleyi, M. sedula and S. metallicus acted through the ‘contact’ and ‘non-contact’ sub-mechanisms of the indirect bioleaching mechanism for the dissolution of pyrite. The role of the bioleaching microorganisms is thus to maintain sufficient levels of Fe³⁺ and acid during pyrite leaching, for maximal mineral dissolution.     

pH-sensitive carbon dots for the visualization of regulation of intracellular pH inside living pathogenic fungal cells

In this paper, the pH-sensitive carbon dots were synthesized by simple one-pot hydrothermal treatment of threonine. The fluorescence of the as-synthesized carbon dots was featured by pH dependence, with the intensity decreasing as pH increases. The carbon dots can be readily internalized into plant pathogenic fungal cells for imaging with dose dependence. Moreover, intracellular pH regulation, a kind of physiological functions of living fungal cells, was visually expressed as the variation of fluorescence intensity of the internalized carbon dots. A transient reduction of the intracellular pH tightly regulated by living fungal cells under basic external condition can be presented as a gradual increase in fluorescence intensity of the carbon dots. On the contrary, the fluorescence of the carbon dots distributed in apple tissue infected by the fungal cells was soon quenched by the basic buffer because there was no intracellular pH regulation in the dead cells.     

Stable auto-tuning of hybrid adaptive fuzzy/neural controllers for nonlinear systems

In direct adaptive control, the adaptation mechanism attempts to adjust a parameterized nonlinear controller to approximate an ideal controller. In the indirect case, however, we approximate parts of the plant dynamics that are used by a feedback controller to cancel the system nonlinearities. In both cases, “approximators” such as linear mappings, polynomials, fuzzy systems, or neural networks can be used as either the parameterized nonlinear controller or identifier model. In this paper, we present an algorithm to tune the adaptation gain for a gradient-based hybrid update law used for a class of nonlinear continuous-time systems in both direct and indirect cases. In our proposed algorithm, the adaptation gain is obtained by minimizing the instantaneous control energy. Finally, we will demonstrate the performance of the algorithm via a wing rock regulation example.     

Importance of nonindigenous harpacticoids (Crustacea: Copepoda) decrease with depth in Lake Ontario

Harpacticoid copepods can be a substantial component of the meiobenthic community in lakes and serve an ecological role as detritivores. Here we present the first species-level lake-wide quantitative assessment of the harpacticoid assemblage of Lake Ontario with emphasis on the status of nonindigenous species. Additionally, we provide COI-5P sequences of harpacticoid taxa through Barcode of Life Data System (BOLD). Harpacticoids were collected at depths from 0.1 to 184 m and from a range of substrates from August to September 2018 as part of the Cooperative Science and Monitoring Initiative (CSMI) offshore benthic survey. Twenty-six meiobenthic samples were analyzed using microscopy for community composition analysis of harpacticoids. We found thirteen indigenous and three nonindigenous species of harpacticoid, with the introduced species dominating at shallow depths. The community transitioned from nonindigenous to indigenous species dominance as depth increased. Nonindigenous species accounted for 79% of the community (by abundance) at depths <20 m, 55% from 20 to 40 m, and only 24% at depths >40 m. The nonindigenous species encountered included the first detections of Schizopera borutzkyi (Monchenko, 1967) and Heteropsyllus nunni (Coull, 1975) from Lake Ontario. S. borutzkyi was the most abundant harpacticoid species in the lake, approaching a maximum density of 50,000/m² and a lake-wide average density of 7,900/m². Numerically important indigenous species included Bryocamptus nivalis (Willey, 1925), Canthocamptus robertcokeri (Wilson, 1958), Canthocamptus staphylinoides (Pearse, 1905), and Moraria cristata (Chappuis, 1929). The prevalence of nonindigenous harpacticoids in the meiobenthos of Lake Ontario suggests further investigations of Great Lakes meiofauna communities are warranted.