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Math Help - exponential decay of a mixture

  1. #1
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    exponential decay of a mixture

    I have some stuff that decays exponentially. The problem is I have a vat of a mixture of the stuff, all added at different times. I can measure the level remaining at a given time. How do I calculate the half life? I get this equation:
    Level=Q1*0.5^\frac{time1}h+Q2*0.5^\frac{time2}h...
    and hit a wall. Any help would be greatly appreciated.
    Last edited by notamathguy; April 20th 2009 at 04:52 AM.
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  2. #2
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    Quote Originally Posted by notamathguy View Post
    I have some stuff that decays exponentially. The problem is I have a vat of a mixture of the stuff, all added at different times. I can measure the level remaining at a given time. How do I calculate the half life? I get this equation:
    Level=Q1*0.5^\frac{time1}h+Q2*0.5^\frac{time2}h...
    and hit a wall. Any help would be greatly appreciated.
    Please provide the exact text of and instructions for the exercise in question, so we can be clear on what is meant. Thank you!
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  3. #3
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    Sorry, it's not an exercise, it's a real world problem. To treat hemophilia we inject a protein into our bloodstream. This clotting factor has a half life that varies by individual. Each dose decays at the same rate, but each has its own time period and initial quantity (the Q in my equation). So, the actual level at any time is given by the sum of each remaining dose. The problem is to determine what half life will produce the measured level 'L' at 'T' if I know the times and quantities for each dose.
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  4. #4
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    Hi guys,
    Lots of people have read this thread. Is this the wrong place to ask this question, is my explanation bad, or is there just no good solution?

    Dan
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  5. #5
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    Quote Originally Posted by notamathguy View Post
    Hi guys,
    Lots of people have read this thread. Is this the wrong place to ask this question, is my explanation bad, or is there just no good solution?

    Dan
    I can't answer the original question but I can quote from the thread http://www.mathhelpforum.com/math-he...ing-faq-2.html:

    Why doesn’t anyone respond to my question?
    Remember, MHF is a global community, our members are from many different time zones and there are many new threads created everyday. Depending on your time zone, or the time of day that you ask, there may not be many active members online to answer your question, and so it may take a while to get to it. Furthermore, a competent person may be on-line but is busy with other matters and is unable to reply (that person may be a Moderator for example). It is best that you do not post problems at the last minute, but ensure that you have enough time to be patient and wait for your question to be answered. Note also that if your question has had a large number of views but no reply, you might think it's being ignored. This is not the case. A person might view but not answer your question for many reasons (including: curiosity, s/he thought they knew the answer but then realised that they didn't, s/he realises that answering will take more time than they have).
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