The theoretical model backs up experimental evidence from 2010 of percolation in living neural networks. And while the researchers and outside experts are loath to overstate the model’s scope, the study suggests that consciousness – or wakefulness – depends on high-quality information transfer between the thalamus and cortex, in line with other theories.
But outside experts caution that the model is quite abstract, thus muddying its relationship to the actual brain. “The link to neurophysiology is a little bit tenuous,” said Moira Steyn-Ross, a physicist at the University of Waikato in New Zealand. She wasn’t involved with the study. “They have the layers, they can describe various behaviors, but how exactly does that relate to anesthetic action?”
Part of the problem, said Michael Hawrylycz, an investigator at the Allen Institute for Brain Science in Seattle, Washington, is that “we don’t know enough about the detailed circuitry of the brain…to really ascertain the realism of models” like Zhou and Xu’s, he said.
But Xu brushes aside concerns that his model is too generic to be relevant, noting that for large-scale phenomena, the small details actually might not matter.
Further study of the chemistry behind this remarkable recovery led him to discover nucleotide excision repair, which allows DNA to recover from damage caused by UV radiation or other carcinogenic substances, such as cigarette smoke.
The mechanism is similar to that of the base excision repair that Lindahl studied. Instead of removing one broken nucleotide, though, enzymes responsible for the repair remove about a dozen nucleotides surrounding the damaged area, replace all of them and seal the strand.
He published his work in 1973.
Lippard, who worked with Sancar on nucleotide excision repair, was especially thrilled to see his colleague's work recognized by the Nobel committee.
"I view [Sancar] as one of the greatest scientists on the planet," said Lippard. "He's got deep insights and he taught me a great deal that was quite valuable in my own work."
As more is understood about the ways in which DNA is repaired, researchers can use these insights to develop strategies to fight diseases such as cancer and a host of genetically controlled and inherited maladies, said Lippard.
"We want to understand the repair mechanisms in some detail so that we can prevent the cancer cells from repairing DNA when we, for example, expose them to radiotherapy," said Lindahl in an interview with Adam Smith of Nobelprize.org.
Bases that suffered early infection allowed the model to make predictions about how the outbreak spread across the country. The model could also estimate what percentage of cases would be serious.
The researchers then simulated a future pandemic ten times worse than the one in 2009. They could make predictions about this event even before its peak had passed in the first infected communities. Knots are everywhere, from laces of shoes to stitches that seal cuts. Sailors and others have known since antiquity that some knots are stronger than others, but such knowledge came largely from intuition and tradition, rather than a fundamental understanding of what makes knots strong.
Now, experiments with wires have helped scientists develop an equation explaining the forces involved within one of the simplest knots around, the overhand knot. Such work could one day lead to a better idea of what knots work best for given applications, such as the stitches used in surgery and the steel cables used in construction, the researchers said.
"Now we can understand the basic principles underlying overhand knots, which are the most basic type of knots used in our everyday life," said study lead author Khalid Jawed, an engineer at MIT in Cambridge. "This can serve as a starting point to investigate the mechanics of more complex type of knots."
Minor differences in the way knots are tied can lead to major differences in strength. Imagine taking a rope, crossing both ends left over right, and then bringing the left end under and out, as if tying a pair of shoelaces. Repeating this sequence results in the relatively weak granny knot. But if one instead crosses the right end over the left, the result is the stronger reef knot.
Developing a scientific model of how a particular knot will perform has proven challenging because sharp turns generate forces that are difficult to calculate. Although straight rods and other linear structures often behave in a straightforward manner, twisted nonlinear structures can behave in unpredictable ways.
To avoid the extra complications involved in sharp turns, previous research exploring knot behavior analyzed simple cases, such as a rope wrapped several times around a rod and locked in place by friction. However, such structures are not true knots.