"The derivative of the quotient of two differentiable functions equal the denominator times the derivative of the numerator minus the numerator times the derivative of the denominator, all divided by the square of the denominator."
Washington, Allyn J. "Basic Technical Mathematics with Calculus." p.672. Chapter 23. The Derivative.
Thursday, November 15, 2007
Thursday, November 8, 2007
Does Chitin have UV protection properties?
Whilst considering the evolutionary advantage of Chitin, the exoskeleton of Arachnids and membrane of fungi, and it's benefits in an environment of high UV, prior to a substantial Ozone thickness; I was wondering if Chitin did in fact have UV protection factors?
Thursday, November 1, 2007
Adenine Obsession?
What is it about Adenine (A) H3N5C5 (approx. AMU = 133.1137), a double ringed purine with 2 hydrogen bonds, that seems to pop up everywhere in my Life Science studies? I found it in DNA, RNA, NAD+, CoEnzyme A, FAD+ and ever ATP!
Monday, October 8, 2007
Thursday, October 4, 2007
Wednesday, October 3, 2007
Brain connections cause rethink over human memory
Brain connections cause rethink over human memory
From issue 2621 of New Scientist magazine, 18 September 2007, page 23
How do we store so many memories? It is a question that has puzzled neuroscientists for decades - and now it seems that our concept of how memory works may have been wrong all along.
It was originally assumed that the number of memories was proportional to the number of neurons in a network. Given that even 1 cubic centimetre of the brain's cortex contains about 50 million neurons, it seemed that the brain could indeed store masses of information. However, this model relied on the notion that each neuron is connected to every other neuron, whereas a neuron is actually connected to between 5000 and 10,000 others.
Neuroscientists then proposed that the number of memories was proportional to the number of connections per neuron. Now Yasser Roudi and Peter Latham at University College London have found a problem with this model too. They calculated that even with 10,000 connections per neuron, a network could only store about 100 memories - regardless of how many neurons were in the network (PLoS Computational Biology, DOI: 10.1371/journal.pcbi.0030141).
This implies that to store a large amount of information, the brain would have to use multiple networks. This may be problematic for something like vocabulary, Latham says. "You wouldn't want to store 100 words in each of [many] different networks; you probably want to store them more or less in one place. Now we don't know how [the brain] does this."
From issue 2621 of New Scientist magazine, 18 September 2007, page 23
How do we store so many memories? It is a question that has puzzled neuroscientists for decades - and now it seems that our concept of how memory works may have been wrong all along.
It was originally assumed that the number of memories was proportional to the number of neurons in a network. Given that even 1 cubic centimetre of the brain's cortex contains about 50 million neurons, it seemed that the brain could indeed store masses of information. However, this model relied on the notion that each neuron is connected to every other neuron, whereas a neuron is actually connected to between 5000 and 10,000 others.
Neuroscientists then proposed that the number of memories was proportional to the number of connections per neuron. Now Yasser Roudi and Peter Latham at University College London have found a problem with this model too. They calculated that even with 10,000 connections per neuron, a network could only store about 100 memories - regardless of how many neurons were in the network (PLoS Computational Biology, DOI: 10.1371/journal.pcbi.0030141).
This implies that to store a large amount of information, the brain would have to use multiple networks. This may be problematic for something like vocabulary, Latham says. "You wouldn't want to store 100 words in each of [many] different networks; you probably want to store them more or less in one place. Now we don't know how [the brain] does this."
Ketamine relieves depression within hours
Ketamine relieves depression within hours
12:57 08 August 2006
NewScientist.com news service
Roxanne Khamsi
A drug used as a general anaesthetic may also work as a remarkably rapid antidepressant, according to a preliminary study.
The drug’s hallucinogenic side effects mean it is unlikely to be prescribed to patients, but it could pave the way to new faster-acting antidepressants, the researchers suggest.
Ketamine is used as an animal tranquiliser, but is perhaps better known as an illicit street drug, sometimes called “special K”. Now researchers have found the drug can relieve depression in some patients within just 2 hours – and continue to do so for a week.
One problem with current antidepressants is that they typically take weeks to kick in. Some studies have found that patients may face a high risk of suicide in the first week after starting an antidepressant treatment because of this lag time. So researchers have been searching for alternative drugs.
Fast acting
In 2000, a small study of eight people with major depression suggested that ketamine mitigated depression to a certain degree (Biological Psychiatry, vol 47, p 351).
Carlos Zarate, chief of the Mood and Anxiety Disorders Research Unit at the National Institute of Mental Health in Bethesda, Maryland, US and colleagues, set out to conduct a larger, more detailed trial of the drug’s antidepressant effects.
They analysed data from 17 participants, all whom suffered from moderate to severe depression and had failed to respond to at least two types of conventional drug treatments....
12:57 08 August 2006
NewScientist.com news service
Roxanne Khamsi
A drug used as a general anaesthetic may also work as a remarkably rapid antidepressant, according to a preliminary study.
The drug’s hallucinogenic side effects mean it is unlikely to be prescribed to patients, but it could pave the way to new faster-acting antidepressants, the researchers suggest.
Ketamine is used as an animal tranquiliser, but is perhaps better known as an illicit street drug, sometimes called “special K”. Now researchers have found the drug can relieve depression in some patients within just 2 hours – and continue to do so for a week.
One problem with current antidepressants is that they typically take weeks to kick in. Some studies have found that patients may face a high risk of suicide in the first week after starting an antidepressant treatment because of this lag time. So researchers have been searching for alternative drugs.
Fast acting
In 2000, a small study of eight people with major depression suggested that ketamine mitigated depression to a certain degree (Biological Psychiatry, vol 47, p 351).
Carlos Zarate, chief of the Mood and Anxiety Disorders Research Unit at the National Institute of Mental Health in Bethesda, Maryland, US and colleagues, set out to conduct a larger, more detailed trial of the drug’s antidepressant effects.
They analysed data from 17 participants, all whom suffered from moderate to severe depression and had failed to respond to at least two types of conventional drug treatments....
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