Study measures effectiveness of different face mask materials when coughing

WASHINGTON: A team of researchers have tested everything from t-shirts and socks to jeans and vacuum bags to determine what type of mask material is most effective at trapping the ultrafine particles which may contain viruses such as SARS-CoV-2, the virus which causes COVID-19. The researchers, from the University of Cambridge and Northwestern University, tested the effectiveness of different fabrics at filtering particles between 0.02 and 0.1 micrometres - about the size of most viruses - at high speeds, comparable to coughing or heavy breathing. They also tested N95 and surgical masks, which are more commonly used in healthcare settings. Previous studies have only looked at a small selection of fabrics when the wearer is breathing normally, when particles are expelled at a lower speed. Studying more fabrics and testing them at higher speeds provides a more robust evidence base for the effectiveness of fabric masks. The results, reported in the journal BMJ Open, show that most of the fabrics commonly used for non-clinical face masks are effective at filtering ultrafine particles. N95 masks were highly effective, although a reusable HEPA vacuum bag actually exceeded the N95 performance in some respects. As for homemade masks, those made of multiple layers of fabric were more effective, and those which also incorporated interfacing, which is normally used to stiffen collars, showed a significant improvement in performance. However, this improvement in performance also made them more difficult to breathe through than an N95 mask. The researchers also studied the performance of different fabrics when damp, and after they had gone through a normal washing and drying cycle. They found that the fabrics worked well while damp and worked sufficiently after one laundry cycle, however, previous studies have shown that repeated washing degrades the fabrics, and the researchers caution that masks should not be reused indefinitely. "Fabric masks have become a new necessity for many of us since the start of the COVID-19 pandemic," said first author Eugenia O'Kelly from Cambridge's Department of Engineering. "In the early stages of the pandemic, when N95 masks were in extremely short supply, many sewers and makers started making their own fabric masks, meeting the demands that couldn't be met by supply chains, or to provide a more affordable option," added O'Kelly. While there are numerous online resources which help people make their own masks, there is little scientific evidence on what the most suitable materials are. "There was an initial panic around PPE and other types of face masks, and how effective they were. As an engineer, I wanted to learn more about them, how well different materials worked under different conditions, and what made for the most effective fit," said O'Kelly. For the current study, O'Kelly and her colleagues built an apparatus consisting of sections of tubing, with a fabric sample in the middle. Aerosolised particles were generated at one end of the apparatus, and their levels were measured before and after they passed through the fabric sample at a speed similar to coughing. The researchers also tested how well each fabric performed in terms of breathing resistance, based on qualitative feedback from users. "A mask which blocks particles really well but restricts your breathing isn't an effective mask," said O'Kelly. "Denim, for example, was quite effective at blocking particles, but it's difficult to breathe through, so it's probably not a good idea to make a mask out of an old pair of jeans. N95 masks are much easier to breathe through than any fabric combinations with similar levels of filtration." In preparation for the study, the researchers consulted with online sewing communities to find out what types of fabric they were using to make masks. Due to the severe shortage of N95 masks at the time, several of the sewers reported that they were experimenting with inserting vacuum bags with HEPA filters into masks. The researchers found that single-use and reusable vacuum bags were effective at blocking particles, but caution that the single-use bags should not be used in face masks, as they fall apart when cut, and may contain component materials which are unsafe to inhale. "It's a matter of finding the right balance - we want the materials to be effective at filtering particles, but we also need to know they don't put users at risk of inhaling fibres or lint, which can be harmful," said O'Kelly. The researchers caution that their study has several limitations: namely, that they did not look at the role which fit plays in filtering particles. In a related project, O'Kelly has been studying how the fit of masks in healthcare settings can be improved. In addition, many viruses are carried on droplets which are larger than those looked at in the current study. However, O'Kelly says the results may be useful for sewers and makers when choosing which fabric to use for making masks. "We've shown that in an emergency situation where N95 masks are not available, such as in the early days of this pandemic, fabric masks are surprisingly effective at filtering particles which may contain viruses, even at high speeds." Copyright © Jammu Links News Source: Jammu Links News

Read More........→October 30, 2020

Nuclear energy too expensive, too slow to battle climate change: report

Nuclear power as a renewable power option is more expensive and slower to implement than alternatives and therefore is not effective in the effort to battle the climate emergency, rather it is counterproductive, as the funds are then not available for more effective options, says a report on the status and trends of the international nuclear industry.

While the number of operating nuclear reactors has increased globally over the past year by four to 417 as of mid-2019, it remains significantly below historic peak of 438 in 2002, according to the World Nuclear Industry Status Report 2019 (WNISR2019), which is being released at the Central European University (CEU) in Budapest. Nuclear construction has been shrinking over the past five years with 46 units underway as of mid-2019, compared to 68 reactors in 2013 and 234 in 1979. The number of annual construction starts has fallen from 15 in the pre-Fukushima year (2010) to five in 2018 and, so far, one in 2019. The historic peak was in 1976 with 44 construction starts, more than the total in the past seven years. WNISR project coordinator and publisher Mycle Schneider stated: “There can be no doubt: the renewal rate of nuclear power plants is too slow to guarantee the survival of the technology. The world is experiencing an undeclared ‘organic’ nuclear phaseout.” Consequently, as of mid-2019, for the first time the average age of the world nuclear reactor fleet exceeds 30 years. However, renewables continue to outpace nuclear power in virtually all categories. A record 165 gigawatts (GW) of renewables were added to the world’s power grids in 2018; the nuclear operating capacity increased by 9 GW. Globally, wind power output grew by 29 per cent in 2018, solar by 13 per cent, nuclear by 2.4 per cent. Compared to a decade ago, nonhydro renewables generated over 1,900 TWh more power, exceeding coal and natural gas, while nuclear produced less. What does all this mean for the potential role of nuclear power to combat climate change? WNISR2019 provides a new focus chapter on the question. Diana Ürge-Vorsatz, Professor at the Central European University and Vice-Chair of the Intergovernmental Panel on Climate Change (IPCC) Working Group III, notes in her Foreword to WNISR2019 that several IPCC scenarios that reach the 1.5°C temperature target rely heavily on nuclear power and that “these scenarios raise the question whether the nuclear industry will actually be able to deliver the magnitude of new power that is required in these scenarios in a cost-effective and timely manner. This report is perhaps the most relevant publication to answer this pertinent question.” Over the past decade, levelised cost estimates for utility-scale solar dropped by 88 per cent, wind by 69 per cent, while nuclear increased by 23 per cent. New solar plants can compete with existing coal fired plants in India, wind turbines alone generate more electricity than nuclear reactors in India and China. But new nuclear plants are also much slower to build than all other options, eg, the nine reactors started up in 2018 took an average of 10.9 years to be completed. In other words, nuclear power is an option that is more expensive and slower to implement than alternatives and therefore is not effective in the effort to battle the climate emergency, rather it is counterproductive, as the funds are then not available for more effective options. The rather surprising outcome of the analyses is that even the extended operation of existing reactors is not climate effective as operating costs exceed the costs of competing energy efficiency and new renewable energy options and therefore durably block their implementation. “You can spend a dollar, a euro, a forint or a ruble only once: the climate emergency requires that investment decisions must favor the cheapest and fastest response strategies. The nuclear power option has consistently turned out the most expensive and the slowest,” Mycle Schneider concludes. The WNISR2019 assesses in 323 pages the status and trends of the international nuclear industry and analyses the potential role of nuclear power as an option to combat climate change. Eight interdisciplinary experts from six countries, including four university professors and the Rocky Mountain Institute’s co-founder and chairman emeritus, have contributed to the report.Source: https://www.domain-b.com

Read More........→June 29, 2020

Atomic-Scale Catalysts May Produce Cheap Hydrogen

 Credit: NCSU

Researchers at North Carolina State University have shown that a one-atom thick film of molybdenum sulfide (MoS2) may work as an effective catalyst for creating hydrogen. The work opens a new door for the production of cheap hydrogen. Researchers found MoS2 thin films are effective catalysts for hydrogen production. Hydrogen holds great promise as an energy source, but the production of hydrogen from water electrolysis – freeing hydrogen from water with electricity – currently relies in large part on the use of expensive platinum catalysts. The new research shows that MoS2 atomically thin films are also effective catalysts for hydrogen production and – while not as efficient as platinum – are relatively inexpensive. “We found that the thickness of the thin film is very important,” says Dr. Linyou Cao, an assistant professor of materials science and engineering at NC State and senior author of a paper describing the work. “A thin film consisting of a single layer of atoms was the most efficient, with every additional layer of atoms making the catalytic performance approximately five times worse.” The effect of the thin films’ thickness came as a surprise to researchers, because it has long been thought that catalysis normally takes place along the edges of the material. Because thin films have very little ‘edge,’ conventional wisdom held that thin films were essentially catalytically inactive. But the researchers discovered that a material’s thickness is important because the thinner the MoS2 thin film is, the more conductive it becomes – and the more conductive it becomes, the more effective it is as a catalyst. “The focus has been on creating catalysts with a large ‘edge’ side,” Cao says. “Our work indicates that researchers may want to pay more attention to a catalyst’s conductivity.” Cao developed the technique for creating high-quality MoS2 thin films at the atomic scale in 2013. The current production of hydrogen from the atomically thin film is powered by electricity. His team is working to develop a solar-powered water-splitting device that uses the MoS2 thin films to create hydrogen. (A Q&A with Cao on how this research differs from earlier studies of other catalysts for hydrogen production can be found on NC State’s research blog.) The paper, “Layer-dependent Electrocatalysis of MoS2 for Hydrogen Evolution,” is published online in Nano Letters. Lead author of the paper is Yifei Yu, a Ph.D. student at NC State. Co-authors include Yanpeng Li, a Ph.D. student at NC State; Dr. Shengyang Huang, a former visiting scholar at NC State; and Drs. Stephan Steinmann and Weitao Yang of Duke University. The research was supported by U.S. Army Research Office grant W911NF-13-1-0201. Contacts and sources: Dr. Linyou Cao, Matt Shipman, North Carolina State University. Source: Article

Read More........→March 19, 2014