Showing papers by "Dov Levine published in 2020"

Recharging and rejuvenation of decontaminated N95 masks

Abstract: N95 respirators comprise a critical part of the personal protective equipment used by frontline health-care workers and are typically meant for one-time usage. However, the recent COVID-19 pandemic has resulted in a serious shortage of these masks leading to a worldwide effort to develop decontamination and re-use procedures. A major factor contributing to the filtration efficiency of N95 masks is the presence of an intermediate layer of charged polypropylene electret fibers that trap particles through electrostatic or electrophoretic effects. This charge can degrade when the mask is used. Moreover, simple decontamination procedures (e.g., use of alcohol) can degrade any remaining charge from the polypropylene, thus severely impacting the filtration efficiency post-decontamination. In this report, we summarize our results on the development of a simple laboratory setup allowing measurement of charge and filtration efficiency in N95 masks. In particular, we propose and show that it is possible to recharge the masks post-decontamination and recover filtration efficiency.

Recharging and rejuvenation of decontaminated N95 masks

Abstract: N95 respirators comprise a critical part of the personal protective equipment used by frontline health-care workers, and are typically meant for one-time usage. However, the recent COVID-19 pandemic has resulted in a serious shortage of these masks leading to a worldwide effort to develop decontamination and re-use procedures. A major factor contributing to the filtration efficiency of N95 masks is the presence of an intermediate layer of charged polypropylene electret fibers that trap particles through electrostatic or electrophoretic effects. This charge can degrade when the mask is used. Moreover, simple decontamination procedures (e.g. use of alcohol) can degrade any remaining charge from the polypropylene, thus severely impacting the filtration efficiency post decontamination. In this report, we summarize our results on the development of a simple laboratory setup allowing measurement of charge and filtration efficiency in N95 masks. In particular, we propose and show that it is possible to recharge the masks post-decontamination and recover filtration efficiency.

Correlation Lengths in the Language of Computable Information.

Abstract: Computable information density (CID), the ratio of the length of a losslessly compressed data file to that of the uncompressed file, is a measure of order and correlation in both equilibrium and nonequilibrium systems. Here we show that correlation lengths can be obtained by decimation, thinning a configuration by sampling data at increasing intervals and recalculating the CID. When the sampling interval is larger than the system's correlation length, the data becomes incompressible. The correlation length and its critical exponents are thus accessible with no a priori knowledge of an order parameter or even the nature of the ordering. The correlation length measured in this way agrees well with that computed from the decay of two-point correlation functions ${g}_{2}(r)$ when they exist. But the CID reveals the correlation length and its scaling even when ${g}_{2}(r)$ has no structure, as we demonstrate by ``cloaking'' the data with a Rudin-Shapiro sequence.

Recharging improves efficiency of decontaminated N95 masks

Abstract: N95 masks form a critical part of the personal protective equipment used by frontline health-care workers, and are typically meant for one-time usage. However, the recent COVID pandemic has resulted in a serious shortage of these masks leading to a worldwide effort to develop decontamination and re-use procedures. A major factor contributing to the filtration efficiency of N95 masks is the presence of an intermediate layer of charged polypropylene electret fibers that trap particles through electrostatic or electrophoretic effects. This charge degrades quickly when the mask is used. Moreover, simple decontamination procedures (e.g. use of alcohol) immediately degrade any remaining charge from the polypropylene, thus severely impacting the filtration efficiency post decontamination. In this brief report, we summarize preliminary results on the development of a simple laboratory setup allowing measurement of charge and filtration efficiency in N95 masks. We show how the charge on the mask changes due to decontamination treatments, and correlate with reduced filtration efficiency. Additionally, we propose and show that it is possible to recharge the masks post-decontamination treatment and recover filtration efficiency. Importantly, recharging can be performed using readily available equipment and materials, and so can be employed both in urban and rural settings. We emphasize that because of the current worldwide lockdown, the measurements reported in this report are preliminary, performed with hastily constructed home-built equipment on a small variety of masks available to us. Although we are confident in our results, we encourage groups with special-purpose equipment to redo and verify our experiments.