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schiffern

7,794 karmajoined il y a 15 ans

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schiffern
·il y a 3 jours·discuss
I expect many researchers are using fresh lab-made microplastics, which are indeed mostly harmless. However part of the problem is that real-world plastics are chemical sponges that absorb toxins (heavy metals, PCBs, etc) from the environment and deliver them in a concentrated dose into the body.

https://www.eurekalert.org/news-releases/923529
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·il y a 5 jours·discuss
Correct. This is why SpaceX rejected using black coatings alone for Starlink. Mirrored surfaces that they tested instead were darker than VANTA black.[0]

On some surfaces they use a SpaceX-designed coating called Low Reflectivity Black, which is the least specular space-rated paint by a factor of 5.[1]

[0] https://www.youtube.com/watch?v=MNc5yCYth5E#t=2430s

[1] https://starlink.com/public-files/BrightnessMitigationBestPr...
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·il y a 12 jours·discuss
Skeptical? I was too.

Check out the interview with Dr Bernie Cohen, who did a lot of the early epidemiological work. The interviewer is rather woo, but the professor is as hard-nose a scientist as you could hope for. It makes a good pair because it let him correct misconceptions.

Long story short, Dr Cohen became unpopular after his data showed home radon levels to be negatively correlated with lung cancer risk. The more radon, the lower your risk of lung cancer.

Part 1: https://www.youtube.com/watch?v=xhkBLhw-8pk

Part 2: https://www.youtube.com/watch?v=SuUFiUoynPo
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·le mois dernier·discuss
Yes. It was the urine processor that had problems with excess calcium, not the air scrubber.

https://ttu-ir.tdl.org/server/api/core/bitstreams/f8ca865b-1...
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·il y a 3 mois·discuss
Mostly your post is just about the side-issue of whether (in 20/20 hindsight) the censorship in the USA was justified. However this ignores the fundamental double-standard toward the USA vs the UAE. In 20/20 hindsight the UAE censorship may turn out to be justified, or not, however we don't know yet.

  > And to the extent that the censorship was justified, yes, at the very least we were legally in a properly declared war.
Didn't I (preemptively) respond to this already?

"You might say it's different since we were at war, but this ignores how the threat model and immediacy is very different in the UAE vs here in the (geographically well protected/isolated) US."

In the UAE these laws are (equally) "proper" and "legal," so I don't see how the presence or absence of a formal declaration of war makes any difference here, or meaningfully responds to my point above.
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·il y a 3 mois·discuss


  >In most of the world such photos would be deemed of public interest and shared
OTOH, anyone remember "loose lips sink ships?" Beyond the famous poster, it was backed up by robust censorship laws.[0][1]

You might say it's different since we were at war, but this ignores how the threat model and immediacy is very different in the UAE vs here in the (geographically well protected/isolated) US.

Battle damage assessment, especially if it's timely, is critical information in any conflict. This is especially true for modern drone-based / hybrid asymmetrical conflict.

[0] https://www.archives.gov/publications/prologue/2001/spring/m...

[1]https://en.wikipedia.org/wiki/Office_of_Censorship
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·il y a 3 mois·discuss
Yes I just mean the more expensive tea on the shelf. On cheaper SKUs they're trying to cut cost so they use normal tea bags. The plastic sachets were a trend for a couple years but hopefully most brands have switched away.

That study is interesting because they used SEM to image the plastic afterward, and you can see how the plastic surface has literally been torn up on a microscopic level simply by touching hot water.

Plastic has a low-energy surface, which means it doesn't take much energy to tear it apart. Even Brownian motion is enough, which is pretty wild.
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·il y a 3 mois·discuss
The kicker? It's only on high-end tea, because it's more expensive than regular tea bags.
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·il y a 3 mois·discuss
Agreed. MERV 11-14 can be far more effective than HEPA.

If you need to filter "one and done" (like pumping air into a hospital operating room), that's where you need HEPA. Most home air purifiers mix the clean air back into the same room, so MERV is closer to the ideal sweet spot.

It's also important to buy reputable brands of MERV filter, ideally ones which have a large number of folds (surface area) like the 3M 1900 MPR. In recent testing about half of filter brands scored well below their claimed MERV rating:

https://www.youtube.com/watch?v=FKAVek1YaSQ
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·il y a 3 mois·discuss
That helps for pollution that comes from outside (traffic, pollen, wood smoke), but most of the microplastics are generated by moving/wearing synthetic textiles inside the home.

Positive pressure systems are great, love 'em, but there's a quantitative mismatch in this case. Above ~1 ACH your HVAC costs will go through the roof (even with heat/humidity recovery), but for effective filtration you need 6-8 ACH to catch the larger dust before your lungs do.
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·il y a 3 mois·discuss
A false sense of security can be worse than nothing, because it prevents you from seeking out actually effective options.

I too would like such a "shy" air purifier, but manufacturers always seem to go the other way: when occupancy is detected they increase the fan speed.

Best option IMO is just to get an air purifier with a good CADR-to-decibel ratio and then (again) size it correctly. A surprisingly good option is something called the Airfanta 3 Pro, which is basically like those wildfire filter boxes except it uses PC fans.
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·il y a 3 mois·discuss


  >microwaving in plastic bowls
More generally, never let hot food touch plastics. The high temperature is what damages the plastic surface, not anything special about microwaves.

For instance the same thing happens with plastic tea bags in hot water: https://www.sciencedirect.com/science/article/pii/S004565352...
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·il y a 3 mois·discuss
https://archive.ph/UcCq6

Saying HEPA filters remove "99%" of microplastic is pretty misleading.

Most of the mass in airborne particles is in the larger sizes of visible dust. However these particles will "fall out" before they reach the air purifier.

The best advice isn't "use only HEPA" or (an odd one, from this article) "use filters with multiple stages," it's to have an air purifier where the Clean Air Delivery Rate (CADR) is matched to room size. For filtering large dust you need a lot of air flow, aim for 6-8 Air Changes per Hour (ACH).

Also the CADR on the box is always on the highest fan speed, which is always way too loud for constant use in an occupied room. So ideally you want to size the air purifiers assuming a fan speed generating 45 decibels or less. HouseFresh is an excellent review site that publishes these numbers.

Most people dramatically undersize their air purifiers, or run them on a very low fan setting, and then they throw up their hands and say that air purifiers don't work.
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·il y a 3 mois·discuss
Transport doesn't "go to zero." Terrestrial transportation is already fully reusable, so it doesn't have the same cost headroom for improvement vs orbital launch.

Thanks, I really needed this post. I'm saving this for when people inevitably try to re-write history by saying "we didn't need Elon, because did anyone really doubted space-based AI would be the winner?? It was obvious all along because blah blah... <insert 20/20 hindsight>"
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·il y a 3 mois·discuss


  >Here's an AI-generated fake video of large transformer manufacturing. It's about half wrong.[2] But right enough to be worth watching.
Which half?

You probably got a lot from this video, because you know which half is wrong. I'd probably get negative knowledge from this video, because I don't.

This may be a new incarnation of the "curse of knowledge," where one over-estimates the value of AI slop if they already know the subject...
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·il y a 3 mois·discuss


  >that’s not good enough for real world manufacturing and simulation
Dumb question: why not?? It's working for that guy and his 3D printer apparently, which is "real world" (though one could certainly argue it's not proper "manufacturing").

In theory pi has infinite places, sure . In real-world practice (vs math-lympics) you never need more than 100 digits, and indeed you rarely ever actually need more than 5.

Why doesn't it work to "just" throw more bit-width and more polygons at it? Who out there actually needs more than that (vs who just thinks they do)?
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·il y a 3 mois·discuss
This is why geometric kernels are the gateway to madness. ;) Thanks for the clarification.
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·il y a 3 mois·discuss
With today's very high orbital launch costs, it's trivially true that the desert is cheaper.

With very low orbital launch costs, it's trivially true that space would become cheaper. Solar panels have no atmosphere/night/seasons and are always pointed at the Sun, no cover glass for hail, no 24h battery either. Radiators are 1/10th the area of PV which is very doable.

The question is, where exactly is the tipping point between those two extremes, and will Starship reach that? Opinions on this naturally bifurcate depending on one's feelings about Elon Musk.

I wouldn't be too worried because SpaceX engineers put a great deal of effort into reflection mitigation, including developing a space-rated mirror able to have an RF signal fire transparently through it.[1] The strategy is to bounce all the sunlight away from Earth, which makes satellites darker than even (hypothetically) covering a satellite in Vantablack.

[1] https://youtu.be/MNc5yCYth5E?t=1717
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·il y a 3 mois·discuss


  >corners where 3 fillets meet
I would imagine there are a few different possible options (preferably a settable parameter):

* Intersection. Conceptually the simplest, the chamfers would just be joined by the solid addition of all three fillet surfaces, creating three new sharp corner edges that meet at a single vertex.

* Rolling sphere. Imagine an idealized spherical "thumb" smoothing out caulk. The middle would be joined by a new spherical concave surface, tangent to all three fillets. Also generalizable to convex fillet intersections, smoothing out sharp corners.

* NURBS, with adjustable parameters or even control points, eg when you want a little more "meat" in a corners for strength of a part.

* Flat corners, for chamfers (what do do when N>3 corners meet?)

* What else?

Ideally you might be able set the corner type separately for inside vs outside corners, or on a per-vertex or (in the most granular case) per-incoming-edge basis? Is that crazy?

How do saddle corners[0] behave? Does it just "work out" and (by some miracle) uniquely resolve for all permutations and corner types?

It certainly gets complex quickly!

[0] center, where the cubes all intersect https://entitleblogdotorg3.files.wordpress.com/2015/02/esche...
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·il y a 3 mois·discuss
By the same standard, Chrome itself is "a tool to download files from Google's servers." Chrome doesn't only download from Google's servers, but the same thing applies to yt-dlp.

I'm equally not "surprised" by their bad behavior, but that shouldn't stop us from condemning Google for unethically misleading people and engaging in browser monopoly abuse.

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EDIT: holding up (hilariously) RIAA lawyers as ethical role models only proves my point, thanks.