Higher concentrations of bacterial enveloped virus Phi6 can protect the virus from environmental decay

Phage Phi6 is an enveloped virus considered as a possible non-pathogenic surrogate for SARS-CoV-2 and other viral pathogens in transmission studies. Higher input amounts of bacteriophage Phi6 are shown to delay and protect the phage from environmental decay, both when the phage are dried in plastic tubes, and when they are stored in saline solution at 4°C. By contrast, when bacteriophage Phi6 are placed in LB (Luria-Bertani) growth medium (instead of saline) prior to placement on the plastic surface, the influence of starting concentration on viral recovery is negligible. The protection is reflected in longer half-lives of the phage at higher concentrations compared to lower. Because experiments supporting the possibility of fomite transmission of SARS-CoV-2 and other viruses rely upon survival of infectious virus following inoculation of various surfaces, high initial amounts of input virus on a surface may generate artificially inflated survival times compared to realistic lower levels of virus that a subject would normally encounter. This is not only because there are extra half-lives to go through at the higher concentrations, but also because the half-lives themselves are extended at the higher virus concentrations. It is important to design surface drying experiments for pathogens with realistic levels of input virus, and to consider the role of the carrier and matrix if the results are to be clinically relevant. IMPORTANCE During the COVID-19 pandemic, a lot of attention has been paid to the environmental decay of SARS-CoV-2 due to proposed transmission of the virus via fomites. However, published experiments have commenced with very high virus titer inoculums, an experimental design not representative of real-life conditions. The study described here evaluated the impact of initial virus titer on environmental decay of an enveloped virus, using a non-pathogenic surrogate for transmission of SARS-CoV-2, enveloped bacteriophage Phi6. We establish that higher concentrations of virus can protect the virus from environmental decay, depending on conditions. This has important implications for stability studies of SARS-CoV-2 and other viruses. Our results point to a limitation in the fundamental methodology that has been used to attribute fomite transmission for almost all respiratory viruses.

Monitoring moisture content and evaporation kinetics from mine slurries through albedo measurements to help predict and prevent dust emissions

The prediction and prevention of fugitive dust emissions from mine tailings surfaces depend largely on our ability to monitor and monitor and predict the evolution of tailings moisture content (TMC). Albedo measurements are demonstrated here to be valuable tools to quantify TMC in bauxite residue samples under controlled conditions in the laboratory. The difference in albedo between 1.30 and 1.55 µm obtained through the infrared integrating sphere method shows good correlations with those acquired with a field spectroradiometer while both are strongly correlated with TMC. Additionally, continuous spectroscopic characterization of evaporating residues is shown to reveal the evolution in their surface drying rates. These optical methods could help predict surface drying state, thereby improving the accuracy of dust emissions risk assessment protocols that support mining industries intervention and mitigation strategies.

Higher concentrations of bacterial enveloped virus Phi6 can protect the virus from environmental decay

Phage Phi6 is an enveloped virus considered as a possible non-pathogenic surrogate for SARS-CoV-2 and other viral pathogens in transmission studies. Higher input amounts of bacteriophage Phi6 are shown to delay and protect the phage from environmental decay, both when the phage are dried in plastic tubes, and when they are stored in saline solution at 4°C. When bacteriophage Phi6 are placed in LB (Luria-Bertani) growth medium prior to placement on the plastic surface, viral recovery is not influenced by the starting concentration. The protection is reflected in longer half-lives of the phage at higher concentrations compared to lower. Because experiments supporting the possibility of fomite transmission of SARS-CoV-2 and other viruses rely upon survival of infectious virus following inoculation of various surfaces, high initial amounts of input virus on a surface may generate artificially inflated survival times compared to realistic lower levels of virus that a subject would normally encounter. This is not only because there are extra half-lives to go through at the higher concentrations, but also because the half-lives themselves are extended at the higher virus concentrations. It is important to design surface drying experiments for pathogens with realistic levels of input virus, and to consider the role of the carrier and matrix if the results are to be clinically relevant.

Body size affects the vertical movement of benthic amphipods through subsurface sediments in response to drying

This study aimed to experimentally examine how riverbed drying and different rates of water level reduction influenced the vertical movement of amphipods of various sizes into different subsurface sediment compositions. Using sediment columns (mesocosms) filled with different sized transparent substrates, we explored how varying speeds of drawdown affected vertical movement and stranding of individuals. We hypothesised that: (1) larger individuals would be less able to migrate within subsurface sediments compared to smaller ones; (2) smaller sediment particles would lead to more individuals becoming stranded and; (3) faster rates of water level drawdown would increase the likelihood of individuals becoming stranded above the waterline. Body size significantly influenced the final position of an individual, with smaller individuals accessing deeper sediments more readily. Larger amphipods were more likely to become stranded above the waterline. Amphipods migrated to greater depths during faster water level reduction rates with smaller individuals displaying greater overall movement. Sediment particle size did not influence the ability of amphipods to move vertically into subsurface sediments in response to water level reduction. The results indicate that subsurface sediments may serve as a refuge from surface drying but that both the size of individual invertebrates influences their ability to migrate vertically.

The Transient Responses of an Axisymmetric Tropical Cyclone to Instantaneous Surface Roughening and Drying

Inland tropical cyclone (TC) impacts due to high winds and rainfall-induced flooding depend strongly on the evolution of the wind field and precipitation distribution after landfall. However, research has yet to test the detailed response of a mature TC and its hazards to changes in surface forcing in idealized settings. This work tests the transient responses of an idealized hurricane to instantaneous transitions in two key surface properties associated with landfall: roughening and drying. Simplified axisymmetric numerical modeling experiments are performed in which the surface drag coefficient and evaporative fraction are each systematically modified beneath a mature hurricane. Surface drying stabilizes the eyewall and consequently weakens the overturning circulation, thereby reducing inward angular momentum transport that slowly decays the wind field only within the inner core. In contrast, surface roughening initially (~12 h) rapidly weakens the entire low-level wind field and enhances the overturning circulation dynamically despite the concurrent thermodynamic stabilization of the eyewall; thereafter the storm gradually decays, similar to drying. As a result, total precipitation temporarily increases with roughening but uniformly decreases with drying. Storm size decreases monotonically and rapidly with surface roughening, whereas the radius of maximum wind can increase with moderate surface drying. Overall, this work provides a mechanistic foundation for understanding the inland evolution of real storms in nature.

Assessing the Roles of Terrestrial Stilling and Solar Dimming in Land Surface Drying/Wetting across China

Decreases in wind speed (i.e., terrestrial stilling) and radiation (i.e., solar dimming) have been identified as important causes of aridity change both globally and regionally. To understand how their roles have varied across different natural and socioeconomic circumstances in China, this study presents a nationwide attribution analysis of land surface drying/wetting across the ten first-level river basins. The results suggest that consistent warming and reductions in relative humidity have significantly enhanced atmospheric evaporative demand and driven the land surface to become drier over the past six decades. However, the widespread terrestrial stilling and solar dimming have largely offset such trends by suppressing evaporation. While spatially varying changes in precipitation were the most influential driver of aridity change over half of the 713 used climate sites, decreasing wind speed and radiation were identified as the dominant cause of wetting at 15% and 13% of the sites, respectively. The impacts of terrestrial stilling and solar dimming were generally more prominent in the north (e.g., the Liao River, Songhuajiang, Hai River, and Huai River basins) and south (e.g., the Southeast, Pearl River, and Yangtze River basins) respectively, which could be associated with the weakening monsoon and intensified anthropogenic disturbances such as ecological restoration, urbanization, and air pollution. We conclude that more attention needs to be paid to the independent and combined climatological impacts of global- and regional-level human activities to develop proactive adaptation strategies of water and land management.

Rapid Drying of High-Moisture Paddy Using a Pneumatic Dryer with Corrugated-Surface Drying Column

Combination of corrugated-surface drying column and multipass drying concept (first-pass and second-pass drying) was made to increase the performance of a pneumatic dryer for high-moisture paddy. In this study, different characteristics of the drying column, which could be characterized by the ratio between the corrugated-surface length (C) and the total length (L) of the drying column (or C/L), were proposed. The influences of drying temperature (120oC, 150oC, and 180oC) and value of C/L (0, 0.5 and 1.0) on the dryer performance and energy utilization of the drying process were disscussed. The drying column with a higher value of C/L had higher potential for increasing dryer performance. For the first-pass drying, the drying system using the drying column with corrugated surface could reduce the energy consumption by 14% to 44% compared with the drying system using the drying column without corrugated surface. For the second-pass drying, the drying system using the drying column with corrugated surface consumed more energy, however. The moisture reduction of paddy could also be significantly increased after the second-pass drying.

Assessment of Influence and Threshold Ratios of Titanium Dioxide and Calcium Carbonate as Pigments on the Physico-Mechanical Properties of Emulsion Paint

Titanium dioxide (TiO2) also known as Titanium White, is an inorganic, synthetic pigment used in paint to protect the substrate from harmful effects of ultraviolet light when lead pigments are regarded as toxic. However, its use is being limited since it causes flu-like symptoms, respiratory problem and skin irritation. Calcium carbonate (CaCO3) is a chemical commonly used as an extender pigment in cement to provide bulkiness at relatively low cost. Because of the problem associated with TiO2, it is of importance to regulate and optimize the use of TiO2 relative to CaCO3 and their influence on the physico-mechanical properties of emulsion paints. Nine paint specimens were formulated using 0 – 80 grams per litre of TiO2 and 120 – 200 grams of CaCO3, respectively at 10 gram interval. The following tests were performed on them: specific gravity, viscosity, pH, surface drying time, hard drying time, wash-ability/adhesion and opacity tests, in accordance to Nigerian Industrial Standard (NIS) 278: 1990. The result shows that all samples met specifications of 10 poise maximum, 5%, 7.5-9.0, 20 minutes, 2 hours, and 201 minimum, for viscosity, specific gravity, pH, surface drying time, hard drying time and wash-ability/adhesion properties, respectively. However, six sample specimens only met the requirement of NIS 278:1990 of 2coats for good opacity. In conclusion, TiO2 has no negative effect on the other physio-mechanical properties except the opacity of the paint and so specimens 7, 8 and 9, and ratio 30:170 is considered the threshold values for the paint production.