#filtration

[fuckyeahfluiddynamics]

Filtering Like a Manta Ray

As manta rays swim, they're constantly doing two important -- but not necessarily compatible -- things: getting oxygen to breathe and collecting plankton to eat. That requires some expert filtering to send food particles toward their stomach and oxygen-rich water to their gills.  (Image credit: manta - N. Weldingh, filter - X. Mao et al.; research credit: X. Mao et al.) Read the full article

[pandemic-info]

How viruses lose infectivity in the air

Great video, but definitely maximize it to see the subs because sound is poor. I really like this channel, good in-depth explanations about airborne particles, masks, etc.

[nanotechnologyworld]

Graphene made permeable for ions

Graphene is an extremely thin, flexible and resistant material made of pure carbon. It forms layers that consist of virtually a single layer

For the first time, a team led by Frank Würthner has now created a model system with a defect that allows the halides fluoride, chloride and bromide to pass through, but not iodide. This was achieved in a stable double layer consisting of two nanographenes that encloses a cavity. The penetrated halide ions are bound in this cavity so that the time required for entry could be measured. The results have been published in the journal Nature.

[auroranekai]

Decrepit Filtration.

An old filtration pipe overgrown by wet looking vines, algae and mold. One side of the pipe seems to be broken open. The big grilles inside the pipe are partially broken and blue light is shining in from the top. Old stickers and graffiti can be seen on metal the inner walls.

I wonder what used to be filtered through these pipes and why they're not used anymore. What happened?

Aesthetic is inspired by Rain World.

[materialsscienceandengineering]

Don't wait, desalinate: A new approach to water purification: The future of clean water is electrified, according to chemists

A water purification system separates out salt and other unnecessary particles with an electrified version of dialysis. Successfully applied

Two-thirds of the Earth's surface is awash with the stuff, but water -- specifically, the clean and drinkable kind -- is inaccessible to billions of people. A new purification system developed by researchers at the Beckman Institute for Advanced Science and Technology uses an electrified version of dialysis to separate salt and other unnecessary particles from the potable product. Successfully applied to wastewater with planned expansion into rivers and seas, the method saves money and saps 90% less energy than its counterparts. The study appears in ACS Energy Letters. If only stripping salt from water was as simple as waving a giant magnet above the Pacific or sifting liquid through a super-fine sieve. Once the shifty mineral dissolves, the separation process -- christened desalination in scientific circles -- becomes more expensive and uses more energy.

Read more.

[indeedgoodman]

[meeedeee]

How to to Clean Our Indoor Air Properly Against COVID-19 | Time

Here's How to to Clean Our Indoor Air Properly Against COVID-19

From UV to ionization, a leading expert explains the best technologies for indoor air disinfection to reduce COVID-19 transmission

*Outdoors is better than indoors

*Indoors requires either greater ventilation or scrubbing of the air (filtration)

*Most buildings have poor ventilation, and cold or hot weather mat require less ventilation

*In those cases, you need to scrub (filter) the air alongside ventilation

*Air duct filtration/UV may have limited value

*Much better to filter "in the room where it happens" using portable filters and Upper-room germicidal UV (GUV) fixtures (not personal UV scrubbers)

*Upper room germicidal is most cost effective for schools and businesses

*Ionization ineffective and causes irritants

TLDR: Mechanical ventilation, upper room UV, and portable room air cleaners

"Outdoors, dilution of any aerosols is infinite—though the time it takes to dilute clouds of aerosol, depends on air movement. Think, for example, of how a cloud of cigarette smoke outdoors lingers or dissipates depending on whether there’s a breeze or not.

Indoors, however, aerosols almost always linger longer than outdoors—often long enough to be inhaled by someone sharing the same space. Put another way, if you breath in an indoor setting where other people are also breathing, you will almost surely breath in some amount of air that has been recently exhaled by someone else. That recycled air—the so-called rebreathed air fraction—estimated by room carbon dioxide measurements, is a good predictor of the risk of infection, given an infectious person generating infectious aerosol in the same room....

Think About Ventilation

Ventilation, natural or mechanical, is the main way that the risk of airborne infection indoors is reduced. For hospital airborne infection isolation and procedure rooms, the U.S. Centers for Disease Control and Prevention (CDC) recommends 6 to 12 room air changes per hour (ACH) with infection-free outdoor air, or air that has been filtered or otherwise decontaminated. One ACH occurs when a volume of air equal to that of the room enters and leaves over a period of one hour. As fresh air enters and mixes with contaminated room air, not all the contaminated air is removed by one air change. Under well-mixed conditions, one air change removes approximately 63% of room air contaminants, and a second air change removes about 63% of what remains, and so on.

But under real world conditions, the protection achieved by ventilation also depends on the amount of contaminant (virus in this case) being added over time, i.e. by an infected person, and on the contagiousness of the infection. The greater the infectiousness of the virus, greater the infection-free ventilation needed to keep concentrations low.

For Omicron, for example, 6-12 ACH ventilation, or equivalent air disinfection, may not be enough to prevent transmission. Unfortunately, not all transmission is preventable by air disinfection—for example, transmission at very close range where there is no time to remove or inactivate viruses generated by one person before they are inhaled by someone else.....

Many residential and older buildings without mechanical ventilation may have about one ACH or less due to air leakage around doors and windows—but when windows are open, depending on building design, orientation, and outside weather conditions, may enjoy significantly higher ACHs. For economical heating and cooling, however, windows are normally closed, especially in larger mechanically ventilated buildings, by design, or closed by occupants in response to outside temperatures. Automated mechanical ventilation systems often bring in a minimum amount of outside air under very cold or hot outside conditions, resulting in most air being recirculated within the building, thereby recirculating air contaminants rather than removing them...

....because mechanical ventilation may not be sufficient to reduce the risk of infection, mechanical ventilation in public buildings should be supplemented by other methods of air disinfection. For current and future viral pathogens like SARS-CoV-19, relatively high levels of “equivalent” ventilation by supplemental air disinfection will be needed.....

....the value of high-efficiency filters or germicidal UV in recirculating ventilation ducts for preventing spread is speculative and limited at best....

A more effective air disinfection strategy is to rapidly decontaminate the air within the room where person-to-person transmission occurs.

“In the room where it happened” is a song from the Hamilton musical, but it could also be a guide to the application of air-disinfection technology....

....a small UV air disinfecting device designed to be worn around the neck cannot possibly move enough air to reduce aerosol transmission. Or, another example, small boxes with UV sources designed to decontaminate cell phones are likely no better than an occasional wipe down with alcohol. Equally irrational are GUV wands because delivering an effective germicidal dose is unpredictable when waving a wand over a surface, and they must be low power to avoid accidental direct over-exposure of eyes or skin. At an even larger scale, GUV portals have been marketed and used in building entrances or exits to “disinfect” people walking through them. This makes no sense not only because no significant decontamination of skin or clothing is possible, but respiratory virus resides in the human respiratory tract, and cannot be eliminated from the outside."

[bleuefille]

__Couple kissing before the fall of the Berlin Wall, 1989