Drying of virus-containing particles: modelling effects of droplet origin and composition

Background and purpose Virus-containing aerosol droplets emitted by breathing, speech or coughing dry rapidly to equilibrium with ambient relative humidity (RH), increasing in solute concentration with effects on virus survival and decreasing in diameter with effects on sedimentation and respiratory uptake. The aim of this paper is to model the effect of ionic and macromolecular solutes on droplet drying and solute concentration. Methods Deliquescence-efflorescence concepts and Kohler theory were used to simulate the evolution of solute concentrations and water activity in respiratory droplets, starting from efflorescence data on mixed NaCl/KCl aerosols and osmotic pressure data on respiratory macromolecules. Results In NaCl/KCl solutions total salt concentrations were shown to reach 10-13 M at the efflorescence RH of 40-55%, depending on the K:Na ratio. Dependence on K:Na ratio implies that the evaporation curves differ between aerosols derived from saliva and from airway surfaces. The direct effect of liquid droplet size through the Kelvin term was shown to be smaller and restricted to the evolution of breath emissions. Modelling the effect of proteins and glycoproteins showed that salts determine drying equilibria down to the efflorescence RH, and macromolecules at lower RH. Conclusion Differences in solute composition between airway surfaces and saliva are predicted to lead to different drying behaviour of droplets emitted by breathing, speech and coughing. These differences may influence the inactivation of viruses.

Quantification of Solute Composition in H2O-NaCl-CaCl2 Solutions Using Cryogenic 2D Raman Mapping

Various analytical techniques have been developed to determine the solution composition of fluid inclusions, including destructive, non-destructive, single-inclusion, and bulk-inclusion methods. Cryogenic Raman spectroscopy, as a non-destructive and single-inclusion method, has emerged as a potentially powerful tool of quantitative analysis of fluid inclusion composition. A method of point analysis using cryogenic Raman spectroscopy has been previously proposed to quantitatively estimate the solute composition of H2O-NaCl-CaCl2 solutions, but there are uncertainties related to heterogeneity of frozen fluid inclusions and potential bias in the processing of Raman spectra. A new method of quantitative analysis of solute composition of H2O-NaCl-CaCl2 solutions using Raman mapping technology is proposed in this study, which can overcome the problems encountered in the point analysis. It is shown that the NaCl/(NaCl + CaCl2) molar ratio of the solution, X(NaCl, m), can be related to the area fraction of hydrohalite over hydrohalite plus antarcticite, Fhydrohalite, by the equation X(NaCl, m) = 1.1435 Fhydrohalite − 0.0884, where Fhydrohalite = hydrohalite area/(hydrohalite area + antarcticite area). This equation suggests that the molar fraction of a salt component may be estimated from the fraction of the Raman peak area of the relevant hydrate. This study has established a new way of estimating solute composition of fluid inclusions using cryogenic Raman mapping technique, which may be extended to other solutions.

The Urothelium: Life in a Liquid Environment

The urothelium, which lines the renal pelvis, ureters, urinary bladder, and proximal urethra, forms a high-resistance but adaptable barrier that surveils its mechanochemical environment and communicates changes to underlying tissues including afferent nerve fibers and the smooth muscle. The goal of this review is to summarize new insights into urothelial biology and function that have occurred in the past decade. After familiarizing the reader with key aspects of urothelial histology, we describe new insights into urothelial development and regeneration. This is followed by an extended discussion of urothelial barrier function, including information about the roles of the glycocalyx, ion and water transport, tight junctions, and the cellular and tissue shape changes and other adaptations that accompany expansion and contraction of the lower urinary tract. We also explore evidence that the urothelium can alter the water and solute composition of urine during normal physiology and in response to overdistension. We complete the review by providing an overview of our current knowledge about the urothelial environment, discussing the sensor and transducer functions of the urothelium, exploring the role of circadian rhythms in urothelial gene expression, and describing novel research tools that are likely to further advance our understanding of urothelial biology.

INFLUENCE OF BRINE COMPOSITION AND CONCENTRATION ON MICROBIAL GROWTH DURING WHOLE COMMON BEAN (Phaseolus vulgaris L) FERMENTATION USING Lb.plantarum BFE 5092

Fermentation technology improves the flavour and shelf life of foods while lowering antinutrient levels. Common bean, though a highly nutritious food, contains high levels of anti-nutrients. Fermentation can be exploited to lower antinutrients in common bean. Though significant strides have been made in bean milk and flour fermentation, common bean is majorly consumed as whole grain. This study, therefore, was aimed at developing a fermentation protocol for whole common bean. Lactobacillus plantarum BFE 5092 was used as starter culture for fermentation. Salt and salt-sugar at 1%, 2% and 3% solute concentrations were used as brine. The effect of starter culture, solute composition and concentration on the growth of lactic acid bacteria (LAB) was monitored. pH and microbial safety were also monitored during the fermentation process. Inoculation with Lb. plantarum BFE 5092 caused a significant increase (P<0.05) of LAB counts in salt brines compared to spontaneous fermentation but no significant difference (P>0.05) in salt-sugar brines. The pH of salt sugar brine solutions was significantly (P<0.05) lowered during the fermentation process from 6.07 to ≤ 3.75. This inhibited enterobacteria growth while promoting the growth of yeast. In salt brines, the pH was ≥ 4.8 favoring enterobacterial growth while inhibiting yeast growth. Solute concentration had no significant effect (P>0.05) on the growth of LAB, pH and microbial safety during fermentation. The study established that use of salt-sugar brine was effective in promoting the growth of LAB during common bean fermentation. It also lowered the pH to ≤ 3.75 and inhibited enterobacterial growth unlike salt brines.

Dominant factors that govern pressure natriuresis in diuresis and antidiuresis: a mathematical model

We have developed a whole kidney model of the urine concentrating mechanism and renal autoregulation. The model represents the tubuloglomerular feedback (TGF) and myogenic mechanisms, which together affect the resistance of the afferent arteriole and thus glomerular filtration rate. TGF is activated by fluctuations in macula densa [Cl−] and the myogefnic mechanism by changes in hydrostatic pressure. The model was used to investigate the relative contributions of medullary blood flow autoregulation and inhibition of transport in the proximal convoluted tubule to pressure natriuresis in both diuresis and antidiuresis. The model predicts that medullary blood flow autoregulation, which only affects the interstitial solute composition in the model, has negligible influence on the rate of NaCl excretion. However, it exerts a significant effect on urine flow, particularly in the antidiuretic kidney. This suggests that interstitial washout has significant implications for the maintenance of hydration status but little direct bearing on salt excretion, and that medullary blood flow may only play a signaling role for stimulating a pressure-natriuresis response. Inhibited reabsorption in the model proximal convoluted tubule is capable of driving pressure natriuresis when the known actions of vasopressin on the collecting duct epithelium are taken into account.

Dependence of Dendritic Growth on Convention with PFM Simulation

A binary alloy PFM (Phase-Field Model) which incorporates the flow field equations is constructed considering the dependence of microstructure on convention. Al-Cu binary alloy is investigated numerically based on the model, and the reasonable computational methods is studied for solving PFM, the effect of convention on dendritic growth and microsegregation patterns is implemented successfully. The computed results indicate that, the larger convention velocity U, the more developed the upstream dendritic branches is, and the more acutely the solute composition in the upstream dendritic solid fluctuates is. But the severity of microsegregation ahead of interface reduces. Nevertheless, the more undeveloped the downstream dendritic branches, the more acutely the solute composition in the the downstream dendritic solid fluctuates is, but the severity of microsegregation ahead of interface aggravates.