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Sandwich


BUMP WHEN LEARNING

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- Sat, 21 Apr 2018 22:40:48 EST +0GOZxpM No.79082
File: 1524364848505.jpg -(34547B / 33.74KB, 497x385) Thumbnail displayed, click image for full size. BUMP WHEN LEARNING
BWL

This thread is for neat facts. not fun facts .
Post here when you learn something interesting, and then I'll read it and think "Wow! Neato!"
20 posts and 9 images omitted. Click View Thread to read.
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Sidney Tillingcocke - Mon, 18 Oct 2021 05:39:29 EST ouzODikQ No.80073 Reply
I studied physics at college. Now I work on car manufacturing. I am fond ot technology and using automation tools. Control systems are an essential part of an automation system. The various types of closed-loop control techniques ensure the process variables to follow the set points. In our work we use https://eltra-trade.com/catalog/stock
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Nicholas Blackstock - Sat, 19 Feb 2022 08:33:19 EST 6bqgFKn4 No.80106 Reply
>>79082
Reverse engineering

Check out winchell chung's atomic rocket and how the certain pages get worse and worse as people write in with stuff to add
User is currently banned from all boards
>>
Phyllis Fosslebotch - Wed, 18 May 2022 13:41:27 EST qw1oy3bu No.80119 Reply
I'm studying combinatorics
neat fact:
C(n,r) = C(n-1,r) + C(n-1,r-1)

Graduate school advice

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- Thu, 11 Mar 2021 20:07:09 EST A6XAbPkj No.80005
File: 1615511229666.png -(450411B / 439.85KB, 652x466) Thumbnail displayed, click image for full size. Graduate school advice
Has anyone on /stem/ been to graduate school? How did you find programs/labs to apply to?

I'm interested in a pretty niche field, so it's hard to look up programs that would interest me. I hope to study fungal proteins/enzymes and their applications in biotechnology, which would be found in a microbiology department, but mycology is already such a tiny fraction of microbio that it feels impossible to find the labs I would want to join.

Is there any way to find prospective programs other than reading papers and looking up the authors?
3 posts omitted. Click View Thread to read.
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Clara Pittfoot - Fri, 02 Jul 2021 02:42:39 EST tcCvNWQn No.80045 Reply
Motherfucker.

OP, are you in the US? If so, you might try universities in Washington state. Washington is one of the moldiest places on Earth and mycology is a subject that's taken seriously there. I think they have a program at Washington State University to commercialize the growing of chanterelle mushrooms.
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Graham Bandlefidging - Wed, 27 Apr 2022 23:28:42 EST 6ckyDtaf No.80112 Reply
1651116522429.png -(1076142B / 1.03MB, 856x894) Thumbnail displayed, click image for full size.
OP here with an update for the two other people who visit this board

Well I didn't get into grad school. I even had an interview at University of Minnesota. They offered to fly me out, pay for my hotel and food, but then omicron cases spiked and it was all over zoom instead. That rejection really stung.

I'm not sure if I'll apply to grad school again. I found a few somewhat interesting labs, but the only one that really stuck out won't be taking new students any time soon. It seems like my dream lab doesn't exist, and I'm starting to accept that while I continue looking for new places to study. Also I recently became a published scientist, which would bolster a future application. Only 3rd author on a paper but it's still something.

My job in a university's plant pathology department ends in June, so I've got to figure out something. I'm looking at fungal biotech jobs in the SF Bay area, but they all seem to be for PhDs or entry level. I'm 27 now and kinda sick of working entry level lab jobs.
>>
Nicholas Siffingforth - Tue, 03 May 2022 21:55:54 EST omQr2edx No.80118 Reply
>>80112
You kinda need to go to grad school if you want a non-entry level job in a lab, especially if you wanna do research. What self respecting company wants to say "hey my lab manager only has a bsc."

Past exam problem. Was it wrong?

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- Wed, 22 Sep 2021 01:11:00 EST hy/3H0ZK No.80065
File: 1632287460823.png -(7225B / 7.06KB, 352x277) Thumbnail displayed, click image for full size. Past exam problem. Was it wrong?
This is a question on a past exam at university. I never understood it and it continues to frustrate me because even if I can't come up with the right answer to a problem, I'll at least 'get' (understand) the proper answer when it is given. But not this one. Here it is:


You are spearfishing in waist-deep water when you spot a fish that appears to be 45° below the water and about 50cm underneath the surface. You recognize that the light coming from the fish to your eye has been refracted and you must therefore aim at some depth below where the fish appears to be. How far below where the fish appears to be should you aim?

n air = 1
n water = 1.35
angle 1 = 45 degrees
assume a flat interface



The first part of the answer given was about first finding the angle of refraction and then the remaining angle (90 degrees minus the angle of refraction).

The second part of the answer given was about finding the value for y.

The last part of the answer given was about using this y value and the remaining angle to find the value of x. So

tan a = x/50cm
x = 50tan(a)
x = 81.3cm



Now I get each part of this answer, I just don't see how it is correct.

This is because the y value here doesn't have to do with the actual fish's position, only its apparent position.

If we knew either how far down or away the fish actually was, then it would be easy to find the missing value because we also know the angle of refraction. But we know neither.

So even though its true that at 50cm away and at an angle of 58.42 degrees, the x value would be 81.3cm, this doesn't actually have to do with the fish's real position.

Is there something that I'm just not getting or am I just a small brain?
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tms !8HZioZhw1c - Thu, 28 Apr 2022 22:13:53 EST 7A5arjSW No.80114 Reply
1651198433218.png -(11002B / 10.74KB, 501x426) Thumbnail displayed, click image for full size.
It's a practical matter. If you shift to get the proper angle for spearing the fish, the apparent position of the fish will also shift. Even if the fish itself stays perfectly still. As the diagram shows, the actual position of the fish isn't necessarily directly below its image. But you know it's somewhere along the line connecting the x position directly below the fish's image to the point on the water's surface you perceive the fish. So by spearing down through that surface point toward the position 31.3 cm below where you perceive the fish, you're guaranteed to spear the fish. Make sense?

culture

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- Fri, 03 Dec 2021 21:54:52 EST xgCvmsFG No.80097
File: 1638586492453.jpg -(105294B / 102.83KB, 750x500) Thumbnail displayed, click image for full size. culture
this image is for educational purposes only

this post might be satire
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Phyllis Crondlegold - Sat, 16 Apr 2022 20:53:46 EST JNCFjCME No.80111 Reply
>>80097
i'd love to make my own virus. it'd be manufactured to make you super horny and increase nerve sensations specifically around the reproductive organs, the breasts, and the ass - the downside is would produce slightly less cum, and you can't actually conceive for a while afterwards. and you get a slight coof.

Today I will explain some new forms of oppression.

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- Wed, 16 Mar 2022 19:08:50 EST sbZ426e/ No.80108
File: 1647472130700.jpg -(27335B / 26.69KB, 595x349) Thumbnail displayed, click image for full size. Today I will explain some new forms of oppression.
*1) In the back of the throat they can install a neurochip that controls the nervous system (It can cause neurological or cardiac diseases).

*2) People or places may have lasers with rays at frequencies not visible and valves that throw liquids (can cause skin diseases).

*3) Cell phones and computers can be remotely activated microphone, they can also emit voices at low volume (It can cause psychiatric illness).
*Advice) If you notice this happening, make a note of the date and place and upload those attacks to an email.

*****If you want to see the images or patents you can search for their scientific names "Neural dust", "BCI", Brain gate", "RFID", "high energy visible light", "metasploit".
User is currently banned from all boards

Hidden World receiver

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- Fri, 26 Nov 2021 18:18:01 EST QW41opDA No.80096
File: 1637968681686.jpg -(204199B / 199.41KB, 750x1057) Thumbnail displayed, click image for full size. Hidden World receiver
http://www.shavertron.com/owreceiver.html

What the fuck am I looking at?
1 posts omitted. Click View Thread to read.
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Dextrolord - Thu, 20 Jan 2022 12:29:20 EST UD52vAOV No.80103 Reply
>>80096
I can recognize a circuit diagram easily enough from my days in engineering skewl, but idk what itd b used for lol
>>
David Brookfield - Tue, 25 Jan 2022 09:50:39 EST r2d0e6h+ No.80104 Reply
>>80096
Basically a UHF radio that can't be tuned to anything specific.
The 954 tube is described here: https://www.radiomuseum.org/tubes/tube_954.html

The rest is just your basic passives and pots.

Untuned tube radio sets like this, or even tuned, but malfunctioning, tube radio sets can produce a lot of wierd "mystery" signals like what's described on the site.

Something similar happens if the heterodyne circuit in an old radio stops working. The heterodyne circuit makes the radio able to isolate a program you tune into, even if another program's frequency is close to or overlaps with the one you want to listen to..

I think this "radio" will just flutter around on the frequency band it's able to pick up (thus untuned), and sometimes "hook" into an ordinary radio program - so you may get random bits and pieces of ordinary radio mixed in with static, TV signal noise and other goodies - and there you have your "hidden world" signal.
I have an inkling that the third 954 tube on the diagram has something to do with this as its passives have different values - though I'm not certain on how that tube works exactly...

Could be cool though if someone could get the right parts and run a scope on it to see what it actually does

>>80103
You didn't learn about reading tubes in diagrams unless your time in engineering skewl was more than 50-ish years ago or unless you've worked with oldschool radio and tv sets or tube amps.
The 954 is also a pentode - a component and concept that's basically extinct in modern electronics...

though getting their data is like finding datasheets for ICs - if you're lucky, you can google them and not hit a paywall. Though sometimes you'll need to hit old catalogs.
>>
Cornelius Paddleridge - Fri, 11 Feb 2022 04:49:42 EST QW41opDA No.80105 Reply
>>80104
So it's basically a Electronic Voice Phenomena machine, like a Spiricom? I thought it might be. Shaver himself was supposed to have picked up alien signals on a malfunctioning welding gun in 1932. Thanks.
Oh, that reminds me, I've been trying to find someone who can figure out the circuitry diagram in this old movie:
https://www.youtube.com/watch?v=JM3hjD_W0yI

You can see the clearest view at about 3:06, but you also get a glimpse of the completed motherboard. The whole thing seems to be a kind of Jacob's Ladder, judging by it's later appearances in comics.

Acetone

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- Mon, 02 May 2016 12:59:32 EST uYoSzwJB No.77874
File: 1462208372041.jpg -(69778B / 68.14KB, 1024x576) Thumbnail displayed, click image for full size. Acetone
Are you going to be flagged if you try to buy pure acetone online? I imagine store-bought nail polish remover has some contaminants.
Experiences?
9 posts and 1 images omitted. Click View Thread to read.
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Bombastus !uYErosQbLM!!Mybq1UbK - Sat, 13 Nov 2021 21:13:21 EST vPbGdL3X No.80092 Reply
>>80042
Unless you live in a supremely methed out county where they ban acetone and everclear for precursor memes, you really don't need to do this.
>>
Dextrolord - Thu, 20 Jan 2022 12:27:18 EST UD52vAOV No.80102 Reply
1642699638133.jpg -(83578B / 81.62KB, 528x797) Thumbnail displayed, click image for full size.
>>77874
>>77874
I have for sure had much worse grey market stuff delivered multiple times, and other things similar to what ur looking for.

Take a break from the stems and try again when ur not so noided

Diversion Hydropower

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- Mon, 18 Jan 2021 20:56:05 EST cuBTyRdx No.79989
File: 1611021365942.gif -(48731B / 47.59KB, 604x454) Thumbnail displayed, click image for full size. Diversion Hydropower
Someone tell me why we don't just build canals and use diversion hydro for the majority of residential capacity needs?

Planning to build a DIY diversion hydro setup at a property in the North West U.S. soon to offset energy costs from owning an EV (small creek runs through the property).

Also fun fact... 96% of all battery storage in the U.S. comes from pumped storage. "Green" energy folks saying acid/lithium battery storage for solar/wind is somehow renewable blow my mind.
5 posts omitted. Click View Thread to read.
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Water Boi - Mon, 12 Jul 2021 10:59:00 EST Iul1K4iz No.80048 Reply
>>80001
Martin, this is a really fantastic explanation to argue against pumped storage solutions at a microgrid level.

A modern waterwheel can generate 2500-5000w depending on stream speed, and stream speed can be pretty easily created / maintained. YouTube diversion microgrid setups.

Without wanting to dmg the environment too heavily, would love to see sloped canals going inland from an ocean. Designated siphoning zones could divert the hydro towards a residential area.

Essentially controlled flooding a few hundred miles inland.
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Phyllis Suddlenuck - Fri, 03 Sep 2021 13:37:50 EST XjrKlvdV No.80056 Reply
It messes up the fish.
>>
Water boi - Sun, 21 Nov 2021 12:57:31 EST NKGNlfnm No.80095 Reply
>>80029

Agreed on all points. However... engineering a diversion setup can be as simple as creating a 10-15 foot drop along a stream with some pvc pipe and a small Turbine.. the drop would create the necessary amount of water speed to power a residential home.

Look at Amsterdam for notes on creating artificial waterways that do not impact the local wildlife. Designing/Creating a new river system from the Atlantic to the Pacific that crosses throughout the United States (not using concrete) would be amazing. We all love water.

Explosive potential of elemental potassium vs smokeless powder?

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- Fri, 08 Jan 2021 23:42:52 EST tcCvNWQn No.79986
File: 1610167372205.jpg -(6321B / 6.17KB, 225x225) Thumbnail displayed, click image for full size. Explosive potential of elemental potassium vs smokeless powder?
I watched a YouTube video of a guy that extracted the potassium from a shitload of bananas, resulting in a big chunk (30 grams maybe?) of potassium that he then threw into a lake. POW! SIZZZZZZZLE POW! This got me to wondering how potassium stacks up against modern smokeless powder. Also, shout out to YouTube channel Explosions&Fire, which is a dif YouTube channel but seriously awesome and you should go watch it.

So, can potassium replace gunpowder?
7 posts and 1 images omitted. Click View Thread to read.
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Edwin Bannernick - Sun, 11 Apr 2021 13:19:08 EST yRn5sLX5 No.80018 Reply
>>79986
No. not only is it not nearly as energetic, but firearms work more on gas expansion than concussive force from ignition/detonation. gunpowder (black powder and modern nitrocellulose and other smokeless powders) work by producing a shitload of gas themselves and building big pressures that way rather than displacing air in exploding.

of course, modern rifles are mostly gas operated and most will fire once but not self-load if fed black powder, and especially so with anything that just explodes rather than producing gas.

furhermore, supersonic muzzle velocities are only possible because the gasses propelling the bullet down the bore have a higher speed of sound in that medium in air. this is why supersonic air rifles are uncommon and usually horribly inaccurate, and why people don't cram tannerite or fuckin C4 into a case rather than nitrocellulose. even exotic caseless ammo is more like firework stars or the stuff found in road flares than being a chunk of high explosive.
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Bombastus !uYErosQbLM!!Mybq1UbK - Sat, 13 Nov 2021 21:14:38 EST vPbGdL3X No.80093 Reply
>>80018
Good answer.
Anything that explodes instead of defrags can really destroy the vessel. This is common in a lot of makeshift guns in rural Asia and Africa that poachers use where they grind up priming compounds to substitute gunpowder. Don't do this.
>>
C-Higgy !lfsExjBfzE - Sat, 13 Nov 2021 21:17:11 EST 0+4q2B79 No.80094 Reply
>>80093
lol yeah that sounds like a recipe for disaster.

Boron tribromide demethylation of codeine

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- Mon, 10 Oct 2016 14:55:50 EST 9Opqdgsf No.78280
File: 1476125750712.png -(19996B / 19.53KB, 593x246) Thumbnail displayed, click image for full size. Boron tribromide demethylation of codeine
I am having trouble with this synthesis. I take 15ml DCM with 200mg codeine base dissolved and make sure its really dry with sieves. Then add something like 500mg of boron tribromide. Immediately the codeine drops out of the DCM solution... no doubt my homemade BBr3 contains a small amount of HBr and Br2. This stuff is unbelievably reactive with air, i've never seen anything fume like it in my life. So i waited/stirred 30mins then added ice/ammonia. No precipitate, i assume the codeine hbr simply dissolved in the aqueous. So next i tried the same thing but added 200mg DIPEA to soak up the acid. Still no morphine precipitate. I worked up both layers both times and verified there was no morphine, i thought it might be dissolved in the high PH aqueous layer but that's only possible with NaOH i believe, morphine should always be insoluble in ammonia hydroxide. I don't know what the problem is.

My boron tribromide is a bit red, i don't have enough to distill. I started from Br2 and Al to make aluminum bromide, anhydrous. Unfortunately i couldn't distill this either but i did leave it under vacuum to hopeful get the free bromine out. I melted it and poured it into another flask with potassium tetrafluoroborate and ended up with only a few ml of BBr3 distilling over. Next time i will use liquid tetrafluoroborate. All 3 of these things really fume like hell. I'm not looking forward to doing it again. I will try to use a vacuum next time, my joints weren't greased and it was pulling in more air then it was worth. I have to make sure i don't get the aluminum bromide on the ground joints as well, god damn what a mess. A propane torch wouldn't even get them apart i had to soak in WD40 then use a propane torch.
34 posts and 5 images omitted. Click View Thread to read.
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Charlotte Bardfield - Mon, 12 Jul 2021 14:40:35 EST SEVIfr/l No.80049 Reply
>>78280
if i put pyridine and codeine in a frying pan and bake it for a while, can i get 10% morphine?
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Ebenezer Pickwell - Fri, 15 Oct 2021 18:43:39 EST vEdeBfXv No.80072 Reply
>>80049
you would get mostly tar, and maybe some morphine.
>>
Bombastus !uYErosQbLM!!Mybq1UbK - Sat, 13 Nov 2021 21:11:32 EST vPbGdL3X No.80091 Reply
>>80049
Just do it in the oven like a normal person. $20 toaster oven I bought used from Craigslist and put it outside was the best results and doesn't build up the toxic chemicals in your house.
You can get some dirty 80% morphine that you can clean up using one of those silica frit / diatom earth things you get on ebay.

the windows 11 upadte

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- Fri, 05 Nov 2021 03:41:39 EST DFvbYia/ No.80090
File: 1636098099289.gif -(1679376B / 1.60MB, 475x250) Thumbnail displayed, click image for full size. the windows 11 upadte
hey guys serious inquiry here, has anyone downloaded the new windows 11 update? currently rocking windows 10 and I dont want to make the leap and then notlike the new operating format

I just want to hear some folks opinion of the new update because its people like you and me that use windows

Overwhelming amount of physics

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- Wed, 21 Oct 2015 20:39:25 EST Fd+bN9n4 No.77312
File: 1445474365700.jpg -(39332B / 38.41KB, 500x417) Thumbnail displayed, click image for full size. Overwhelming amount of physics
Student here, I'm taking a calculus based physics course and it's ruining my life. Literally spend the whole day, roughly 6-8 hours working on physics problems daily because of the overwhelming amount of work that goes into our grade. To the point that I have been neglecting my other subjects and my grades in those classes are slowly going down, except physics.

My question is, is there any tips or advice on how to juggle such intensive courses and exceed in all of them at the same time? I need to reevaluate my plan because I feel like if I spend less time on physics, my grade will go down since the material is so dense.

Stories of people in higher academia are appreciated. Also tips to unwind and not let physics ruin your life.

For example, I worked on 8 hours of crunching problems in my problem set all day. Now that I'm home, I feel the need to continue but my brain feels like mush.

PS.

I take adderall on the weekday and I don't have ADHD, just because I want to pass this class.
21 posts and 6 images omitted. Click View Thread to read.
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Nigel Siblingwater - Fri, 17 Sep 2021 16:00:05 EST gdkQBrgd No.80060 Reply
>>77312 Consider the learnaifromscratch meme curriculum: https://learnaifromscratch.github.io/math.html. This will teach you mathematics at least the basics. Later you will be able to comprehend transcendental mathematics under E. Orwell and write logico-mathematical proofs of reincarnation.
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Nell Cunkinkidging - Fri, 08 Oct 2021 03:43:00 EST YAGFPcTQ No.80071 Reply
I am fond of readinf about technology and implement its part in manufacturing work .echnology has allowed the planet to become a smaller place. Over the course of a day, it is possible to travel to the other side of the world to see new countries, new cultures, and new opportunities. I think it s great to use automaton equipment like https://eltra-encoder.eu/catalog/optical-hollow-shaft-incremental-encoder encoders in packing industry.

Tech Bugs and such

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- Thu, 07 Oct 2021 03:23:15 EST 45CPlhgt No.80068
File: 1633591395752.png -(101064B / 98.70KB, 720x1440) Thumbnail displayed, click image for full size. Tech Bugs and such
Just dumping pix/screenshots of mobile tech that has at some point made me sus or triggered a skitzzo tier paranoia in me.
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>>Hmmm, what's this? - Thu, 07 Oct 2021 03:26:09 EST 45CPlhgt No.80069 Reply
1633591569654.png -(208334B / 203.45KB, 720x1440) Thumbnail displayed, click image for full size.
DICKS EVERYWHERE
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>>Hmmm, what's this? - Thu, 07 Oct 2021 03:31:06 EST 45CPlhgt No.80070 Reply
1633591866263.jpg -(230145B / 224.75KB, 625x1036) Thumbnail displayed, click image for full size.
DICKS EVERYWHERE

Will Surrounding a House by Dirt Increase R-Value?

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- Wed, 22 Sep 2021 03:58:23 EST UJChBBkQ No.80066
File: 1632297503924.jpg -(26336B / 25.72KB, 653x458) Thumbnail displayed, click image for full size. Will Surrounding a House by Dirt Increase R-Value?
If you build a house and make it so that the house has a layer of dirt around the side of the house. Say x feet/cm would the R-value increase or would it make no difference?
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Ian Dinningstone - Wed, 22 Sep 2021 04:00:33 EST UJChBBkQ No.80067 Reply
>>80066
Since dirt is everywhere and wood isn't I thought of this. Compress the layer of dirt in a layer around the house. House should be insulted more than just concrete blocks of regular insulation?

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