Guest viewing limit reached
  • You have reached the maximum number of guest views allowed
  • Please register below to remove this limitation

Half Life in a Nutshell

The biological half-life of a substance is the time required for half of that substance to be removed from an organism by either a physical or a chemical process.

Hope that helped.
 
Bier said:
The biological half-life of a substance is the time required for half of that substance to be removed from an organism by either a physical or a chemical process.

Hope that helped.
Click to expand...

is the time required for that half to be removed the same time for the remaining half?
 
Glass half empty, glass half full. Yes, it should be the same amount of time..relatively. There are factors like saturation points, receptor mediation et cetera but in a nutshell, it simply means how long it takes for 50% of the original amount of compound to exit the body.

For pharmacological purposes, this remaining 50% is an indication of when you need to take the next dose. For example..if the aspirin you just took has a HL of 3 hours..you'll probably need another dose of aspirin 4-6 hours from the first dose.
 
bioman said:
Glass half empty, glass half full. Yes, it should be the same amount of time..relatively. There are factors like saturation points, receptor mediation et cetera but in a nutshell, it simply means how long it takes for 50% of the original amount of compound to exit the body.

For pharmacological purposes, this remaining 50% is an indication of when you need to take the next dose. For example..if the aspirin you just took has a HL of 3 hours..you'll probably need another dose of aspirin 4-6 hours from the first dose.
Click to expand...

ahhh nicely put
 
AnonyMoose said:
is the time required for that half to be removed the same time for the remaining half?
Click to expand...

No, otherwise you could just give a "whole life" time because it would just be twice the half life.

The classic examples of half life come from radioactive materials. They decay at an exponential rate (the longer it decays, the slower it decays) which is based on what the material itself is. So you can never tell how long it will take something to take to decay completely because you can only approximate it to an infinite amount of time. You could use a series of decays to figure out how long it would take to decay down to a certain fraction of what you originally started off with. You could essentially use a fraction that for all intents and purposes is going to be understood as zero. Then you could say that the substance has decayed down to a level where it is no longer useful/harmful.

Hope that helps.
 
JJC said:
No, otherwise you could just give a "whole life" time because it would just be twice the half life.

The classic examples of half life come from radioactive materials. They decay at an exponential rate (the longer it decays, the slower it decays) which is based on what the material itself is. So you can never tell how long it will take something to take to decay completely because you can only approximate it to an infinite amount of time. You could use a series of decays to figure out how long it would take to decay down to a certain fraction of what you originally started off with. You could essentially use a fraction that for all intents and purposes is going to be understood as zero. Then you could say that the substance has decayed down to a level where it is no longer useful/harmful.

Hope that helps.
Click to expand...

hugh?
 
Haha oops...I guess when I re-read it, it is a little confusing. :blink:

But basically if you have 100% of whatever, it will take x amount of time to decay half of it. Once you get down to 50%, it will take x amount of time to get down to 25%. To get down to 12.5%, it will take x amount of time again.

So you never really get to 0% and thus can never specify when it is all gone.

I was just saying that you can pick a certain percentage (say 10% of the original amount) where you thought the substance no longer had an effect and figure out how much time it takes to get there.

There. That's better. :woohoo:
 
JJC said:
But basically if you have 100% of whatever, it will take x amount of time to decay half of it. Once you get down to 50%, it will take x amount of time to get down to 25%. To get down to 12.5%, it will take x amount of time again.
Click to expand...

So, the x here stays the same or is different every time? :)

E.g. if a substance has a half life of 1 hour, it means it takes 1 hr for it to decay to 50%, but is it then 1 hour again to get to 25%, or does the process always slow down (exponentially), as you said, or does the exponential slowing down only occur with radioactive stuff? :)
 
Arzi75 said:
So, the x here stays the same or is different every time? :)

E.g. if a substance has a half life of 1 hour, it means it takes 1 hr for it to decay to 50%, but is it then 1 hour again to get to 25%, or does the process always slow down (exponentially), as you said, or does the exponential slowing down only occur with radioactive stuff? :)
Click to expand...

x is the same every time. If it wasn't, I would use y, z, etc. ;) I should really be using tau as half life, but whatevs.

Take home answer: Half life is the amount of time for half of whatever you have at that moment to decay/dissipate/whatever.

Heh, I guess in this case it might not be exponential. It really all depends on the substrate, mechanism, etc. I think I got carried away with my nerdiness...because the decay could be linear instead. I think bioman said it better than I, so see his post above. :clap2:
 
JJC said:
I guess in this case it might not be exponential. It really all depends on the substrate, mechanism, etc. I think I got carried away with my nerdiness...because the decay could be linear instead.
Click to expand...

So, the x is not same if the decay is exponential, but is the same when the decay is linear? :)

So, basically the half time can be a constant, if the decay is linear? Are there any rules of thumb to know when it is linear or when it is exponential? E.g. with like vitamins and other nutriceuticals, I'd suppose their decay would be pretty linear?

I like your nerdiness. Nothing wrong with that. :)
 
Let's get a BIG-ASS CHEESE LOG, an egg-timer, and a knife.

Ok, you got your cheese log and knife? Good, let's begin.

Set a timer for 15 minutes. When the timer goes off, cut the cheese log in half, and eat one of the halves. Reset the timer.

When it goes off, cut the remains of your cheese log in half again, and eat one of the halves. Now you should have 1/4 of the original cheese log left. Reset the timer for another 15 minutes.

After it goes off. Cut the remains in half, and eat one of the halves. Now you should have 1/16 of the original cheese log left.

You getting the drift here, or do we need to eat more cheese log? You've just completed 3 half lives of thesinner's magic cheeselog.

Things decay at a rate in proportion to themselves. Think of of people losing weight: It's a ton easier for someone who's 150lbs overweight to lose 30lbs than someone who's 12%bf to lose 10lbs. Half life refers to the amount of time it takes for something to decay to one half it's beginning state.
 
thesinner said:
Let's get a BIG-ASS CHEESE LOG, an egg-timer, and a knife.

Ok, you got your cheese log and knife? Good, let's begin.

Set a timer for 15 minutes. When the timer goes off, cut the cheese log in half, and eat one of the halves. Reset the timer.

When it goes off, cut the remains of your cheese log in half again, and eat one of the halves. Now you should have 1/4 of the original cheese log left. Reset the timer for another 15 minutes.

After it goes off. Cut the remains in half, and eat one of the halves. Now you should have 1/16 of the original cheese log left.

You getting the drift here, or do we need to eat more cheese log? You've just completed 3 half lives of thesinner's magic cheeselog.

Things decay at a rate in proportion to themselves. Think of of people losing weight: It's a ton easier for someone who's 150lbs overweight to lose 30lbs than someone who's 12%bf to lose 10lbs. Half life refers to the amount of time it takes for something to decay to one half it's beginning state.
Click to expand...


:blink: I think I need more cheeselog!


:toofunny:
 
thesinner said:
I come up with the best recipe ideas when I'm in that state. You should write down whatever food-related thoughts jump into your head.
Click to expand...

I don't have much food in the house at the moment so anything sounds good at the moment. I was tired as hell coming home from work, fell asleep, woke up and the wife was coming home from the gym. Yep, missed my w/o so I'm in a crappy mood right now. :frustrate
 
Viperspit said:
I don't have much food in the house at the moment so anything sounds good at the moment. I was tired as hell coming home from work, fell asleep, woke up and the wife was coming home from the gym. Yep, missed my w/o so I'm in a crappy mood right now. :frustrate
Click to expand...

I think I might have drove by your gym the other day (a powerhouse in MI near Detroit?). (Note: not a stalker, I just have a good memory.)
 
thesinner said:
I think I might have drove by your gym the other day (a powerhouse in MI near Detroit?). (Note: not a stalker, I just have a good memory.)
Click to expand...

Probaly not, I work out at LTF. Although I have gone to a Powerhouse a few times closer to me. Detroit is about 45 minutes east from us. What were you doing out this way?
 
Viperspit said:
Probaly not, I work out at LTF. Although I have gone to a Powerhouse a few times closer to me. Detroit is about 45 minutes east from us. What were you doing out this way?
Click to expand...

I work for an automotive supplier. Had to make a visit to one of the many Ford Plants.
 
thesinner said:
Let's get a BIG-ASS CHEESE LOG, an egg-timer, and a knife.

Ok, you got your cheese log and knife? Good, let's begin.

Set a timer for 15 minutes. When the timer goes off, cut the cheese log in half, and eat one of the halves. Reset the timer.

When it goes off, cut the remains of your cheese log in half again, and eat one of the halves. Now you should have 1/4 of the original cheese log left. Reset the timer for another 15 minutes.

After it goes off. Cut the remains in half, and eat one of the halves. Now you should have 1/16 of the original cheese log left.

You getting the drift here, or do we need to eat more cheese log? You've just completed 3 half lives of thesinner's magic cheeselog.

Things decay at a rate in proportion to themselves. Think of of people losing weight: It's a ton easier for someone who's 150lbs overweight to lose 30lbs than someone who's 12%bf to lose 10lbs. Half life refers to the amount of time it takes for something to decay to one half it's beginning state.
Click to expand...

Best. Half-Life. Example. Ever.

Hmmm maybe I should send this to my old college physics profs... :study:
 
You must log in or register to reply here.
Back
Top