COVID-19 Exposure Assessment Tool (CEAT): Exposure quantification based on ventilation, infection prevalence, group characteristics, and behavior.

The coronavirus disease 2019 (COVID-19) Exposure Assessment Tool (CEAT) allows users to compare respiratory relative risk to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for various scenarios, providing understanding of how combinations of protective measures affect risk. CEAT incorporates mechanistic, stochastic, and epidemiological factors including the (i) emission rate of virus, (ii) viral aerosol degradation and removal, (iii) duration of activity/exposure, (iv) inhalation rates, (v) ventilation rates (indoors/outdoors), (vi) volume of indoor space, (vii) filtration, (viii) mask use and effectiveness, (ix) distance between people (taking into account both near-field and far-field effects of proximity), (x) group size, (xi) current infection rates by variant, (xii) prevalence of infection and immunity in the community, (xiii) vaccination rates, and (xiv) implementation of COVID-19 testing procedures. CEAT applied to published studies of COVID-19 transmission events demonstrates the model's accuracy. We also show how health and safety professionals at NASA Ames Research Center used CEAT to manage potential risks posed by SARS-CoV-2 exposures.

Covid-19 Exposure Assessment Tool (CEAT): Easy-to-use tool to quantify exposure based on airflow, group behavior, and infection prevalence in the community.

The COVID-19 Exposure Assessment Tool (CEAT) allows users to compare respiratory relative risk to SARS-CoV-2 for various scenarios, providing understanding of how combinations of protective measures affect exposure, dose, and risk. CEAT incorporates mechanistic, stochastic and epidemiological factors including the: 1) emission rate of virus, 2) viral aerosol degradation and removal, 3) duration of activity/exposure, 4) inhalation rates, 5) ventilation rates (indoors/outdoors), 6) volume of indoor space, 7) filtration, 8) mask use and effectiveness, 9) distance between people, 10) group size, 11) current infection rates by variant, 12) prevalence of infection and immunity in the community, 13) vaccination rates of the community, and 14) implementation of COVID-19 testing procedures. Demonstration of CEAT, from published studies of COVID-19 transmission events, shows the model accurately predicts transmission. We also show how health and safety professionals at NASA Ames Research Center used CEAT to manage potential risks posed by SARS-CoV-2 exposures. Given its accuracy and flexibility, the wide use of CEAT will have a long lasting beneficial impact in managing both the current COVID-19 pandemic as well as a variety of other scenarios.

Cryo-TEM Snapshots of Ferritin Adsorbed on Small Zeolite Crystals.

The adsorption of macromolecules on zeolite crystal surfaces has been investigated by cryo transmission electron microscopy (TEM) of frozen hydrates. It was determined that ferritin shows different adsorption behavior on NaY (TEM image on the right) and USY zeolites (TEM image on the left).

Conditions for the adsorption of proteins on ultrastable zeolite Y and its use in protein purification.

The adsorption of proteins on ultrastable zeolites was investigated. Protein binding to one of these, ultrastable zeolite Y (USY), was studied in detail. Protein binding to USY, with a Si/Al ratio of > 240, was found to be dependent on the pH of the solution, being highest at or just below the pI of the protein. The amount of protein adsorbed on the zeolite was found to be 10 times as much as the estimated binding to the external surface of the USY. We propose an adsorption mechanism involving the formation of a protein layer strongly bound to the USY surface, further protein layers being formed on top of this on the basis of protein-protein interactions. The protein-protein interactions can be disrupted by changing the pH. Ultrastable zeolite Y was used as a new matrix for protein purification. Undesired proteins can be removed from a crude preparation by adsorption on USY, increasing the purity of a specific protein, or the protein can be adsorbed on the zeolite and subsequently eluted through changing the pH. These two means of protein purification are exemplified by the purification of peroxidase from a crude horseradish extract and by the purification of lysozyme from egg white.

Purification of proteins by the use of hydrophobic zeolite Y.

Hydrophobic zeolite Y can be used as a fast and efficient and inexpensive matrix in the purification of proteins from crude extracts. Preferably the zeolite can be used in the first purification step, replacing the commonly used precipitation techniques with (NH4)2SO4 or ethanol. The time required for the zeolite prefractionation was a few hours compared to the much more time consuming precipitation procedure which demands centrifugation and subsequent dialysis. Proteins can be absorbed on the zeolite either in order to remove undesired proteins or to be subsequently eluted from the zeolite in order to achieve purification and concentration. Removal of undesired proteins is exemplified by the purification of horseradish peroxidase from a crude extract. The zeolite procedure enhanced the specific activity five times and provided a yield similar to that which was obtained by the use of standard procedures, (NH4)2SO4 fractionation and ion-exchange chromatography. Binding and subsequent elution of proteins from the zeolite is exemplified by the purification of monoclonal antibodies from hybridoma culture supernatants. Proteins were desorbed from the zeolite by the use of polyethylene glycol 600 and this procedure yielded a purification factor of 5.