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2:45 AM
Q: Can facial surgical mask effectively filter particles of smoke pollution?

Saif60Singapore is having an episode of its regular hazy season because of smoke from forest fire. Some people has been using surgical mask like these: http://en.wikipedia.org/wiki/File:Blossom_3_Ply_Bacterial_Filter_Masks_Elestic_Earloop_Face_Mask_Surgical_Masks_a.jpg , presumably for health reason. ...

Off topic perhaps?
@ϚѓăʑɏβµԂԃϔ yeah, different communities have different standards
1 hour later…
4:08 AM
@DavidZaslavsky Of course... it's off-topic...
Bacteria/virus, filter dust, etc... - I don't think there's much physics in it...
Much like shopping suggestion - whether this is okay to use, etc...
4:19 AM
I'm more interested in how an island nation with 0 trees has forest fires...
hmmm, it seems the smoke is blowing in from Sumatra
anyway, I'll try to edit that question to make it more physics
4:57 AM
@ChrisWhite Now, that's what I call a heroic contribution :D
@DavidZaslavsky Okay David... Now, I give up :P
5:30 AM
Q: A "non-mainstream" flag

dimension10I have noticed some "non-mainstream" (it may be rude to say crackpot) questions and answers recently such as: Questions Mass term in the Minkowski metric and an oscillation model in Lorentz group Help me test and prove this theory? Can we model gravitation as a repulsive force? Answers what...

5 hours later…
10:12 AM
What the...!
I'm quite lazy and mostly don't insert edit descriptions under posts...
An anonymous user tried to edit something...
(not an useful edit though)
I thought of improving it. Once improved, I removed the "photos edited" phrase and saved the edit ...
Now, it's a combination of the deleted phrase + auto description.... - Ridiculous scheme :D
10:59 AM
looks okay to my weary eyes
by weary, I mean tired.... teaching unappreciative high school kids all day, week, month... and 14 years...
Paddle 'em :p
I hate it when good teachers go unappreciated :/
Seen it happen waay to often
14 years - 2 countries, 8 schools, over 1200 students.... 14 graduate Physics classes, 9 graduate maths classes and 1 graduate Chemistry class. I have taught Physics, Chem, Bio, Maths, Electronics, French, Japanese, Sport and Special Education...and feel I have accomplished nothing whatsoever....(asides from the 8.9 uni degrees)
I have been attacked 4 times (once with a knife), defended against 2 attempted abductions and shielded students during a massacre hoax
and evacuated a class of terrified kindergarten kids after an earthquake
and no student has ever failed my graduating classes
Attacked? By students? O.o
11:08 AM
yes and parents... parent-teacher interviews can get interesting
I'm a student myself, but I think that if you leave a positive impression on even a single student, teaching that class is worth it. At least, that's what I think I would feel like if teaching.
One of the more surreal times was evacuating the school before a typhoon... then a quake hit...
then the photocopier broke down
Isn't that sort of the sole purpose of photocopiers? ;)
then the coffee machine short circuited,.... we knew then that we were in a deal of trouble
11:11 AM
not o much the photocopier, but the poltergeist therein
but that will all soon come to an end
once my PhD is complete (degree no. 9)
nah... going tinto research hopefully
am only 36
tempted (but won't) post a question as to why the photocopier fritzes itself when I go within 3 metres (10 feet) of it
and why my toaster goes stir crazy when a Britney Spears song comes on the radio
Gtg, tyyl :)
11:19 AM
no worries, take care!
2 hours later…
1:16 PM
Okay.... Back with the upgraded version... Crazy Buddy - Back with his best :D
@ManishEarth: You didn't see my message...
Not the only reason that others feel difficult to ping me, but also - I'm going nuts by seeing these crazy symbols again and again when I log it :)
1 hour later…
2:42 PM
@Ben Crowell: Indeed 'energy-momentum-tensor' tag and 'stress-energy-tensor' tag are mostly synonyms. Btw, it is possible to make tags synonyms or merge tags, so one doesn't have to edit each and every single post separately.
You have switched 'energy-momentum-tensor' tag to 'stress-energy-tensor' tag in so far approx 20 posts in a row. It is a drastic change of the front page. If the posts are already located on the front page, it is one thing, but bringing up a lot of old posts is another matter. In the future, if you have to do such massive changes please do it in smaller blocks, say only 5 questions at a time, so that each new post still gets its 15 minutes of fame.
One should also ask: Do the community agree with these changes? Half the physicists may say 'energy-momentum-tensor' rather than 'stress-energy-tensor'.
Perhaps we should create a 'stress-energy-momentum-tensor' tag instead as a kind of umbrella tag? I would also be interested in what other people think.
3:04 PM
@qmechanic that won't ping him
He wasn't in the room recently
@bencrowell Please see Qmechanic's message above. Thanks :)
I know. I left him a message on the main site.
Oh. Oops. Silly me...
3:47 PM
physics.stackexchange.com/questions/64916/… A number of people talk about isotopes of varying half-lifes -- cesium, iodine, uranium -- and I get the impression that they consider radionucleides with longer half-lifes to pose greater health hazards.
Leaving aside for the moment the fact that they don't all emit the same type of radiation (alpha beta gamma) but considering only half-life, wouldn't the longest-lived isotopes be the safest to have in your environment? U-238 has half-life of >4 bn yrs acc. to Wiki. So I'm thinking it would be safe to put a chunk of it under my pillow because there are so few decays per time unit?
@EugeneSeidel well, short half-lives are safe as long as you stay away from them for, oh, a couple dozen half-lifetimes
the long half lives are safe as long as there isn't a collection of more radioactive decay products sitting there too
Ok take rad. isotope of cesium would that be considered short or medium
like uranium ore might have radium or radon sitting in it
you are saying this b/c it is impossible to manufacture 100% pure U 238?
3:51 PM
I would consider it medium - a chunk of it will outlast a person more or less
well, no, pure U238 would be safer than some rock containing U238 together with millions of years of decay products
in any event, lifetime is really only the third most important consideration for safety
what are the first 2
as you said, there is the type of emission (alpha particles are basically harmless)
3:53 PM
also bio-concentration sort of effect
how fast it washes out of the body?
like, all else being equal, cesium is safer than iodine because cesium forms a salt that washes out of the body relatively fast, whereas any iodine you ingest is all put in your thyroid
thats why they sell mega doses of iodine i guess
to block your thyroid?
this is only important because cancer requires multiple mutations in the same cell, so diffusing them throughout your body is preferential to having them all in one place
indeed - that is the point of iodine tablets
3:56 PM
i find the reporting in the media to be inadequate, they emphasize billions of years half life as an argument against storage of nuclear waste
well, that is a terrible reason, yes, especially given that all the uranium we have came from the earth to begin with
@Qmechanic: Having two synonymous tags is just a mistake. I saw a broken window, and I fixed it.
@chris the only sense there is that if you store something that long living in a facility that won't hold
thanks chris
@EugeneSeidel also, most people don't appreciate how little mass there is to nuclear waste - we're not talking landfills, we're talking small containers
3:58 PM
Then its a concern
@Manish i've read persuasive arguments why storage in primordial salt deposits should be stable for many millions of years (salt is said to be "self-healing" around ruptures)
by the way i tried to put the link to the Q on a line of its own but when i hit the return key to insert a line break it just posts
Shift + enter -> line break without posting, but I don't know if that will generate a preview
try making the link its own post
yeah did not think of that
4:22 PM
@eugene hadn't heard of that, will take a look
Thx :)
@ChrisWhite one more question if i may :) so i'm thinking -- again leaving aside a b g rad and differential distribution & persistence in body tissue (as well as relative abundance) -- that the hazardousness has a bowl shaped curve for different half lifes.
short half lifes are hazardous only locally and for a short time. medium half lifes are most hazardous because they have time to disperse over wide areas while continuing to emit ionizing radiation in significant amounts, then long lived isotopes are relatively safe again because they are almost inert in human timescale.
ah but i forgot that isotopes with long half lives don't decay down to stable ones directly, they may decay to isotopes with shorter half lives in turn
(an upside down bowl shape, that is)
4:43 PM
@EugeneSeidel I suppose that's roughly the case, but it's a tricky business
I think the byproducts have a higher correllation with deadliness over the half life
@EugeneSeidel in all honesty, many of the high-Z isotopes are at least as toxic chemically as radioactively - heavy metals aren't too good for your body
@Qmechanic I was just fine with the energy momentum tensor. The all encompassing tag could be a good idea.

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