Science desk | ||
---|---|---|
< January 18 | << Dec | January | Feb >> | January 20 > |
Welcome to the Wikipedia Science Reference Desk Archives |
---|
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
The article says they stop others from getting sick if the wearer is sick. But, do they protect the wearer from sick people? Many thanks. Anna Frodesiak ( talk) 04:53, 19 January 2019 (UTC)
I planned to write a better answer but to be honest, I can't really be bothered digging up the sources. As others have said and others mentioned, it's unclear whether face masks provide any real protection to the wearer again aerosolised viruses. They do provide some protection from the wearer coughing and sneezing.
For example, for control of season influenza, in healthcare settings the US CDC recommends they be worn by possibly infected persons until they are isolated. They also recommend either a surgical mask, or a respirator "when antiviral medication supplies are expected to be limited and influenza vaccine is not available, e.g., during a pandemic", for healthcare workers getting within 6 feet of a person who is infected or likely infected. This is along with standard and droplet precautions which I think will generally include eye protection (either goggles or a face shield [1]) They recommend infected people wear a mask in some circumstances. Outside healthcare settings, they make no recommendations for mask use, even for people who are unvaccinated and at high risk of complications. (They do suggest if they are going to wear a mask they should do it all the time.) [2]
During the 2009 H1N1 pandemic, they did recommend a face mask or respirator for those at high risk of complications where H1N1 was presented in the community in crowded settings and for caregivers of those infected. (They also said they weren't recommended could be considered by those both high risk and not high risk in non healthcare occupational settings where people were coming into with those with symptoms.) BTW, the guidelines also suggests that although there is agreement that respirators are better, it's not clear if this applies if they don't fit properly or aren't used properly. (Maybe see also [3] and the earlier CDC guidelines PDF which does note there seemed to be no differences in Hong Kong during the SARS outbreak.) I think this is one reason why they were mentioned together. (For healthcare workers, you also have to consider time taken etc and how these affect compliance rates and other issues.) [4].
It's my understanding that even for those who suspect they may be of benefit when used by non infected persons who aren't knowingly coming into close contact with infected persons, one of the biggest hypothesis advantages is actually in limiting them touching their faces. [5] [6]
Nil Einne ( talk) 04:55, 22 January 2019 (UTC)
Of the nine trials of facemasks identified in community settings, in all but one, facemasks were used for respiratory protection of well people. They found that facemasks and facemasks plus hand hygiene may prevent infection in community settings, subject to early use and compliance." So it's possible there is now evidence they are useful for non infected people in certain circumstances. That said, we still don't know why are are of use. Nil Einne ( talk) 05:21, 22 January 2019 (UTC)
I've recently read the General Code of Operating Rules, and one of the things it says is that if a diesel train gets stuck in a tunnel, the crew must shut down the engine at once (to prevent carbon monoxide poisoning, obviously). Which raises the question, what is the emergency procedure if a steam train gets stuck in a tunnel??? Because that would be a dire emergency indeed -- a steam train generates far more carbon monoxide (along with other toxic gases) than a diesel train, and also I don't see any way that the smoke production can be shut down instantly! 2601:646:8A00:A0B3:0:0:0:ECBD ( talk) 05:03, 19 January 2019 (UTC)
Hello, I wonder when I read about armor resistance against penetration, that for any type of armor, resistance against HEAT is greater than APFSDS. 46.32.122.165 ( talk) 06:28, 19 January 2019 (UTC)
So the penetrating rod is more resistant to lose its kinetic energy than the penetrating jet formed due to the melting of the copper cone inside HEAT warheads . 149.200.193.163 ( talk) 14:03, 19 January 2019 (UTC)
Thanks alot everyone. 80.10.51.64 ( talk) 21:49, 20 January 2019 (UTC)
Our article standard enthalpy of reaction currently states:
From the first law of thermodynamics we have a relation, That is, the enthalpy of a reaction at constant volume is equal to the change in the internal energy (Δ E) of the reacting system.
I will readily admit that is one topic where I get confused all the time, but I believe this is incorrect. The first law at constant volume says the change in internal energy is equal to the heat transfer. The standard enthalpy of reaction is defined by the heat of reaction at constant pressure (since it is for everything at standard T/P), but the heat of reaction at constant pressure is not necessarily the same as the heat of reaction at constant volume, is it? Tigraan Click here to contact me 19:33, 19 January 2019 (UTC)
A mundane web search says constant pressure of 1 atm, one bar and a specified temperature, 1 atm, 25 C, usual phase for STP, or 1 M in solution. It might be productive to keep looking, because I just took the top university-looking hits, but I think the OP has the right of it and can cite any of these or some other to make the change suggested. Just intuitively ... the other definition supposes, for example, that the enthalpy change of running a furnace reflects the heat produced when you dispose the exhaust from the furnace as high pressure CO2 and water, which might be ecologically friendly but doesn't seem very common. Wnt ( talk) 22:07, 19 January 2019 (UTC)
I just want to know at wich pressure air morphes into a state where it is compressed so much that it looks like steam — Preceding unsigned comment added by Saludacymbals ( talk • contribs) 20:26, 19 January 2019 (UTC)
no i meeant this: https://www.youtube.com/watch?v=dKvNmftZ3tU&t=106s and this : https://www.youtube.com/watch?v=LW9gLmDo9t0&t=2s in both videos you can see that air pressure can be so high that the air somehow solidifies and i wonder at wich pressure this occures — Preceding unsigned comment added by Saludacymbals ( talk • contribs) 00:20, 20 January 2019 (UTC)
Why is it that sources will say chimpazees and humans share 98% of DNA and all humans share 99.7% of DNA, but two non-identical human siblings share 50% of their DNA? TFD ( talk) 22:47, 19 January 2019 (UTC)
Science desk | ||
---|---|---|
< January 18 | << Dec | January | Feb >> | January 20 > |
Welcome to the Wikipedia Science Reference Desk Archives |
---|
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
The article says they stop others from getting sick if the wearer is sick. But, do they protect the wearer from sick people? Many thanks. Anna Frodesiak ( talk) 04:53, 19 January 2019 (UTC)
I planned to write a better answer but to be honest, I can't really be bothered digging up the sources. As others have said and others mentioned, it's unclear whether face masks provide any real protection to the wearer again aerosolised viruses. They do provide some protection from the wearer coughing and sneezing.
For example, for control of season influenza, in healthcare settings the US CDC recommends they be worn by possibly infected persons until they are isolated. They also recommend either a surgical mask, or a respirator "when antiviral medication supplies are expected to be limited and influenza vaccine is not available, e.g., during a pandemic", for healthcare workers getting within 6 feet of a person who is infected or likely infected. This is along with standard and droplet precautions which I think will generally include eye protection (either goggles or a face shield [1]) They recommend infected people wear a mask in some circumstances. Outside healthcare settings, they make no recommendations for mask use, even for people who are unvaccinated and at high risk of complications. (They do suggest if they are going to wear a mask they should do it all the time.) [2]
During the 2009 H1N1 pandemic, they did recommend a face mask or respirator for those at high risk of complications where H1N1 was presented in the community in crowded settings and for caregivers of those infected. (They also said they weren't recommended could be considered by those both high risk and not high risk in non healthcare occupational settings where people were coming into with those with symptoms.) BTW, the guidelines also suggests that although there is agreement that respirators are better, it's not clear if this applies if they don't fit properly or aren't used properly. (Maybe see also [3] and the earlier CDC guidelines PDF which does note there seemed to be no differences in Hong Kong during the SARS outbreak.) I think this is one reason why they were mentioned together. (For healthcare workers, you also have to consider time taken etc and how these affect compliance rates and other issues.) [4].
It's my understanding that even for those who suspect they may be of benefit when used by non infected persons who aren't knowingly coming into close contact with infected persons, one of the biggest hypothesis advantages is actually in limiting them touching their faces. [5] [6]
Nil Einne ( talk) 04:55, 22 January 2019 (UTC)
Of the nine trials of facemasks identified in community settings, in all but one, facemasks were used for respiratory protection of well people. They found that facemasks and facemasks plus hand hygiene may prevent infection in community settings, subject to early use and compliance." So it's possible there is now evidence they are useful for non infected people in certain circumstances. That said, we still don't know why are are of use. Nil Einne ( talk) 05:21, 22 January 2019 (UTC)
I've recently read the General Code of Operating Rules, and one of the things it says is that if a diesel train gets stuck in a tunnel, the crew must shut down the engine at once (to prevent carbon monoxide poisoning, obviously). Which raises the question, what is the emergency procedure if a steam train gets stuck in a tunnel??? Because that would be a dire emergency indeed -- a steam train generates far more carbon monoxide (along with other toxic gases) than a diesel train, and also I don't see any way that the smoke production can be shut down instantly! 2601:646:8A00:A0B3:0:0:0:ECBD ( talk) 05:03, 19 January 2019 (UTC)
Hello, I wonder when I read about armor resistance against penetration, that for any type of armor, resistance against HEAT is greater than APFSDS. 46.32.122.165 ( talk) 06:28, 19 January 2019 (UTC)
So the penetrating rod is more resistant to lose its kinetic energy than the penetrating jet formed due to the melting of the copper cone inside HEAT warheads . 149.200.193.163 ( talk) 14:03, 19 January 2019 (UTC)
Thanks alot everyone. 80.10.51.64 ( talk) 21:49, 20 January 2019 (UTC)
Our article standard enthalpy of reaction currently states:
From the first law of thermodynamics we have a relation, That is, the enthalpy of a reaction at constant volume is equal to the change in the internal energy (Δ E) of the reacting system.
I will readily admit that is one topic where I get confused all the time, but I believe this is incorrect. The first law at constant volume says the change in internal energy is equal to the heat transfer. The standard enthalpy of reaction is defined by the heat of reaction at constant pressure (since it is for everything at standard T/P), but the heat of reaction at constant pressure is not necessarily the same as the heat of reaction at constant volume, is it? Tigraan Click here to contact me 19:33, 19 January 2019 (UTC)
A mundane web search says constant pressure of 1 atm, one bar and a specified temperature, 1 atm, 25 C, usual phase for STP, or 1 M in solution. It might be productive to keep looking, because I just took the top university-looking hits, but I think the OP has the right of it and can cite any of these or some other to make the change suggested. Just intuitively ... the other definition supposes, for example, that the enthalpy change of running a furnace reflects the heat produced when you dispose the exhaust from the furnace as high pressure CO2 and water, which might be ecologically friendly but doesn't seem very common. Wnt ( talk) 22:07, 19 January 2019 (UTC)
I just want to know at wich pressure air morphes into a state where it is compressed so much that it looks like steam — Preceding unsigned comment added by Saludacymbals ( talk • contribs) 20:26, 19 January 2019 (UTC)
no i meeant this: https://www.youtube.com/watch?v=dKvNmftZ3tU&t=106s and this : https://www.youtube.com/watch?v=LW9gLmDo9t0&t=2s in both videos you can see that air pressure can be so high that the air somehow solidifies and i wonder at wich pressure this occures — Preceding unsigned comment added by Saludacymbals ( talk • contribs) 00:20, 20 January 2019 (UTC)
Why is it that sources will say chimpazees and humans share 98% of DNA and all humans share 99.7% of DNA, but two non-identical human siblings share 50% of their DNA? TFD ( talk) 22:47, 19 January 2019 (UTC)