Just a Short Note

Just wanted to share what I've been reading lately and might be interesting for you too :

Edward Boyden, assistant professor in the MIT Media Lab, uses pulses of yellow light to to reversibly silence brain cells, which could block abnormal neuron activity associated with diseases like epilepsy and Parkinson's. Hopefully this is a good sign for non-surgical treatment.

Researchers from Institut de recherche pour le Développement reported that the Himalayan glaciers are melting under the effect of global warming. Here is the report in PDF format.

Molecular oxygen has finally been discovered in interstellar space according to Swedish Space Corporation.

And last but surely not least, I just found a great site about A Review of the Universe - Structures, Evolutions, Observations, and Theories.

Okay guys, that's is for now. See ya!

Rotaxane machine - a nanomachine inspired by Maxwell's demon

Continuing my earlier post about Maxwell's Demon, recently Professor David Leigh of the University of Edinburgh's School of Chemistry and and colleagues have built a model that mimics Maxwell's demon - an atom-sized motor that could lead to man-made nanomachines.

The molecular model of the demon is a rotaxane (mechanically-interlocked molecular architecture consisting of a dumbbell-shaped molecule that is threaded through a macrocycle or ring-like molecule.). In this rotaxane machine (nanomachine), information about the location of the molecular ring is used to move the system from equilibrium. But gathering and then implementing that information costs energy... in other words the second law of thermodynamics remains valid.

Maxwell's Demon Becomes Reality :

“Our machine has a device - or ‘demon’ if you like - inside it that traps molecule-sized particles as they move in a certain direction.

“Maxwell reasoned that if such a system could ever be made it would need energy to work. Without energy, it might appear that the perpetual motion of the molecules could power other devices in the same way as a windmill, but Maxwell reasoned that this would go against the second law of thermodynamics.

“As he predicted, the machine does need energy and in our experiment it is powered by light. While light has previously been used to energise tiny particles directly, this is the first time that a system has been devised to trap molecules as they move in a certain direction under their natural motion. Once the molecules are trapped they cannot escape.”

Dreams of theory of everything

The ultimate aim of many scientists and theorists is to find a complete description of nature, maybe some simple mathematical equation that you could write on your hat!

This theory of everything would refer to gravity in the same mathematical form as the other forces - that of quantum theory. This would tie up all the basic forces of the universe into one coherent system. So far, though, there is no satisfactory theory of quantum gravity, but "superstring theory" - in which particles are regarded not as point-like objects but as modes of vibration on loops of "string" - seems to bring gravity into the quantum regime.

Steven Hawking predicts that such a theory will be discovered in the next 20 years. A new theory asserts that biology, not physics, will be the key to unlocking the deepest mysteries of the universe, such as quantum mechanics.

"The answer to the universe is biology -- it's as simple as that," says Dr. Robert Lanza, vice president of research and scientific development at Advanced Cell Technology. He details his theory in The American Scholar's spring issue, published on Thursday. Lanza says scientists will establish a unified theory only if they radically rethink their understanding of space and time using a "biocentric" approach. His article is essentially a biological and philosophical response to Hawking's A Brief History of Time, in which he questions how we interpret the big bang, the existence of space and time, as well as many other theories -- assertions that might ruffle the feathers of some physical scientists.

Read more at Will Biology Solve the Universe?

Non-Newtonian fluid

Non-Newtonian fluid is a fluid whose viscosity changes when the gradient in flow speed changes. Colloidal suspensions and polymer solutions like ketchup and starch/water paste are non-Newtonian fluids. A non-Newtonian fluid is a fluid in which the viscosity changes with the applied strain rate. As a result, non-Newtonian fluids may not have a well-defined viscosity.

A pool filled with non-newtonian fluid

Predictions of the Properties of Water from First Principles

Krzysztof Szalewicz, UD professor of physics and astronomy, led the development of the first computer model that can accurately predict both the properties of a pair of water molecules and of liquid water.

Equipped with high-speed computers and the laws of physics, scientists from the University of Delaware and Radboud University in the Netherlands have developed a new method to “flush out” the hidden properties of water--and without the need for painstaking laboratory experiments.

Their new first-principle simulation of water molecules--based exclusively on quantum physics laws and utilizing no experimental data--will aid science and industry in a broad range of applications, from biological investigations of protein folding and other life processes, to the design of the next generation of power plants.

We all know a molecule of water chemically as H2O--two hydrogen atoms bonded to one oxygen atom. Sounds simple, doesn't it? But liquid water is much more complex than that.

“Water as a liquid is not simple at all and has several properties different from most other liquids,” Szalewicz said. “For example, a well-known anomaly of water is that its density is highest at four degrees Celsius above the freezing point. Thus, ice floats on water, whereas the solid state of other compounds would sink in their liquids."

Among its many properties, water also can absorb large amounts of heat before it begins to get hot, and it releases heat slowly during cooling. Otherwise, pools of water, from puddles to oceans, might boil during the day or freeze solid at night, regardless of the season.

Water's unique characteristics are directly related to its molecular structure and the ability of water molecules to form hydrogen bonds with other water molecules.

“For a long time, most researchers agreed that, in its liquid state, each water molecule coordinates on average with four other water molecules by forming hydrogen bonds,” Szalewicz said. “However, a 2004 paper in Science claimed that this coordination takes place with only two molecules, a discovery that, if correct, would turn over the whole water paradigm.”

The experimental claim was not dismissed right away, Szalewicz said, because existing theoretical models of liquid water were “parameterized” or coordinated to a specific class of experiments.

“However, the ambiguities about the structure of liquid water may be resolved if the structure is predicted directly from the laws of physics,” Szalewicz said.

Through the use of quantum mechanics, the application of the laws of physics at the microscopic level, the scientists were able to generate a new theoretical framework for describing the structure and behavior of the water molecule atom by atom.

“This became possible recently when fast multiprocessor computers enabled very accurate solutions of the equations of quantum mechanics describing the forces that water molecules exert on each other,” Szalewicz said. “Once these forces are known, one can find motions in an ensemble of water molecules and predict all the properties of liquid water.”

The UD researchers used clusters of Linux computers to perform the large-scale computer calculations required for the research. The study took several months to complete.

The result is a new model -- the first that can accurately predict both the properties of a pair of water molecules and of liquid water.

Among its many applications, the research should help scientists better understand water in not only its liquid form, but in other states as well, such as crystalline forms of ice, and water in extreme conditions, including highly reactive “supercritical” water, which is used to remove pollutants in wastewater and recover waste plastic in chemical recycling, Szalewicz said.

Source : University of Delaware

Maxwell's Demon - violating the entropy

Maxwell's demon is an imaginary creature created by James Clerk Maxwell in 1867. It is a thought experiment meant to raise questions about the possibility of violating the second law of thermodynamics.

Suppose there is a room filled with a gas at some temperature. This means that the average speed of the molecules is a certain amount depending on the temperature. Some of the molecules will be going faster than average and some will be going slower than average. Suppose that a partition is placed across the middle of the room separating the two sides into left and right. Both sides of the room are now filled with the gas at the same temperature.

Maxwell imagined a molecule sized trap door in the partition with his minuscule creature (the demon) poised at the door who is observing the molecules (look at the picture above). When a faster than average molecule approaches the door he makes certain that it ends up on the left side (by opening the tiny door if it's coming from the right) and when a slower than average molecule approaches the door he makes sure that it ends up on the right side.

So after these operations he ends up with a room in which all the faster than average gas molecules are in the left side and all the slower than average ones are in the right side. So the room is hot on the left and cold on the right. Then one can use this separation of temperature to run a heat engine by allowing the heat to flow from the hot side to the cold side.

Thermodynamics says this is impossible, you can only increase entropy (or rather, you can decrease it at one place as long as that's balanced by at least as big an increase somewhere else).

So why wouldn't a setup like Maxwell's demon work? Well, any real "demon" that does this would not be a disembodied spirit receiving its information telepathically. To acquire information about the world you must be in physical interaction with it, and on the atomic and molecular scale you cannot ignore the quantum mechanical nature of the world. For instance, to be able to see the molecules the "demon" would have to absorb whole photons at a time, and any detailed version of the thought experiment will run into the uncertainty principle and the fact that an interacting "demon" will acquire the same temperature as the rest of the system.

The link between thermodynamics and quantum physics is even stronger: macroscopic entropy can only be computed correctly from the cumulative contributions from microscopic states if these are described quantum mechanically.

Information theory is about the concept of entropy abstracted away from physical systems, and applied to any context that deals with knowledge about the state of a system (signal processing, communication, data compression, encryption &c.). In fact, Shannon originally referred to information as "entropy" (with a minus sign). In recent times, there have been interesting developments in applying the ideas of information theory back to physics, notably in dynamical systems theory, aka chaos.

Real-life versions of Maxwellian demons (with their entropy lowering effects of course duly balanced by increase of entropy elsewhere) actually occur in living systems, such as the ion pumps that make our nervous systems work, including our minds. Molecular-sized mechanisms are no longer found only in biology however, it's also the subject of the exciting new field of nanotechnology.

So Maxwell's demon is an icon for our times, sitting at the crossroads of information and the physical universe.