Posted by Benjamin Roudenis on February 5, 2010 0 comments
A study in the Feb. 5 Science reports that water can freeze at different temperatures depending on whether the surface it rests on is positively or negatively charged. Under certain conditions, water can even freeze as it heats up.
“We are very, very surprised by this result,” says study coauthor Igor Lubomirsky of the Weizmann Institute of Science in Rehovot, Israel. “It means that by controlling surface charge, either positive or negative, you can either suppress ice formation or enhance ice formation.”
. . . . .
With no charge on the surface, the water froze at -12.5º C, on average. But on the positively charged surface, water froze at a relatively balmy -7º. And on a negatively charged surface, ice formed, on average, at a chilly -18º.
. . . . .
Lubomirsky and colleagues also managed to freeze water by heating it. Water droplets stayed liquid at -11º for up to 10 minutes on a negatively charged surface. But after the negative charge dissipated, heating the room to -8º was enough to induce a positive charge in the pyroelectric crystal and freeze the water.
Posted by Benjamin Roudenis on January 24, 2010 0 comments
With a median family income under $30,000 and unemployment rate at a whopping 27 percent, Detroit is in need of help. While most residents are not so worried about the condition of the city, one of the few remaining millionaires is trying to transform Detroit from Motor City to an Urban Farm.
John Hantz has come up with a plan to develop farm pods on the vacant land in Detroit, which isn’t that expensive. Each of these pods will utilize the latest in green farming techniques like compost-heating greenhouses and hydroponic systems.
Each of these pods will have their own residential frontage, and food would be grown there to prevent transportation from distant cities. Hantz is willing to put up the $30 million required to start the project, once he gets concessions from the Detroit city government.
Posted by Benjamin Roudenis on January 24, 2010 0 comments
Stanford University researchers aren’t stopping at paper when it comes to exploring how carbon nanotubes can be used to create thin, flexible batteries. They’ve moved on from paper and ink to cotton and polyester. Looking at combining carbon nanotubes and fabrics, the research team is bringing us closer to having wearable electronics and conductive fabrics.
The work, published in Nano Letters, expands on the science behind lightweight, flexible, and wearable electronics. Think about that cool turn signal jacket for cyclists that uses conductive thread and to make LED lights flash with just a touch of the hand to the sleeve. And all those concept designs for clothing that charges a device while you walk are a little less futuristic.
The researchers state that “with an extremely simple “dipping and drying” process using single-walled carbon nanotube (SWNT) ink” the fabric is turned into highly conductive textiles.
Posted by Benjamin Roudenis on January 10, 2010 0 comments
Read Erik Verlinde ‘s paper “On the Origin of Gravity and the Laws of Newton,” where he explains gravity as an entropic force. Here is the abstract:
Starting from first principles and general assumptions Newton’s law of gravitation is shown to arise naturally and unavoidably in a theory in which space is emergent through a holographic scenario. Gravity is explained as an entropic force caused by changes in the information associated with the positions of material bodies. A relativistic generalization of the presented arguments directly leads to the Einstein equations. When space is emergent even Newton’s law of inertia needs to be explained. The equivalence principle leads us to conclude that it is actually this law of inertia whose origin is entropic.
Posted by Benjamin Roudenis on January 9, 2010 0 comments
On January 5, the National Weather Service changed the criteria for severe thunderstorms by upping the minimum size hail from ¾ to 1 inch—quarter size. The wind threshold—50 knots, or 58 mph—remains the same.
The reason for the change, according to a statement issued by the Fire and Public Weather Services Branch of the NWS, is that research reveals “significant damage” doesn’t occur from hail smaller than an inch. Hailstones the size of quarters or larger are the ones most destructive to cars, homes, buildings, and crops.
Over the years, and particularly in the Plains states, the statement reads, “the frequency of severe thunderstorm warnings issued for penny-size and nickel-size hail might have desensitized the public to take protective action during a severe thunderstorm warning.” Too many warnings for events that were not damaging garnered complaints and made the warnings somewhat meaningless.
Posted by Benjamin Roudenis on January 5, 2010 0 comments
This is my favorite speech from my favorite author. Here is an excerpt:
I regard consensus science as an extremely pernicious development that ought to be stopped cold in its tracks. Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled. Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you’re being had.
Let’s be clear: the work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science consensus is irrelevant. What is relevant is reproducible results. The greatest scientists in history are great precisely because they broke with the consensus.
Finally, I would remind you to notice where the claim of consensus is invoked. Consensus is invoked only in situations where the science is not solid enough. Nobody says the consensus of scientists agrees that E=mc2. Nobody says the consensus is that the sun is 93 million miles away. It would never occur to anyone to speak that way.
Posted by Benjamin Roudenis on January 1, 2010 0 comments
Most of the carbon dioxide emitted by human activity does not remain in the atmosphere, but is instead absorbed by the oceans and terrestrial ecosystems. In fact, only about 45 percent of emitted carbon dioxide stays in the atmosphere.
However, some studies have suggested that the ability of oceans and plants to absorb carbon dioxide recently may have begun to decline and that the airborne fraction of anthropogenic carbon dioxide emissions is therefore beginning to increase.
Many climate models also assume that the airborne fraction will increase. Because understanding of the airborne fraction of carbon dioxide is important for predicting future climate change, it is essential to have accurate knowledge of whether that fraction is changing or will change as emissions increase.
To assess whether the airborne fraction is indeed increasing, Wolfgang Knorr of the Department of Earth Sciences at the University of Bristol reanalyzed available atmospheric carbon dioxide and emissions data since 1850 and considers the uncertainties in the data.
In contradiction to some recent studies, he finds that the airborne fraction of carbon dioxide has not increased either during the past 150 years or during the most recent five decades.
Posted by Benjamin Roudenis on December 23, 2009 0 comments
By dipping an ordinary piece of paper into ink infused with carbon nanotubes and silver nanowires, scientists have been able to create a low-cost battery or supercapacitor that is ultra-lightweight, bendable and very durable. The paper can be crumpled, folded or even soaked in acidic or basic solutions and still will work.
Stanford University scientist Yi Cui had previously created nanomaterial energy storage devices using plastics, but his new research showed that a paper battery is more durable because the ink adheres more strongly to paper. Coating a sheet of paper with ink made of carbon nanotubes and silver nanowires produced a highly conductive storage device that could be used in a multitude of applications.
“These nanomaterials are special,” Cui said. “They’re a one-dimensional structure with very small diameters. “The small diameter helps the nanomaterial ink stick strongly to the fibrous paper, making the battery and supercapacitor very durable. The paper supercapacitor may last through 40,000 charge-discharge cycles – at least an order of magnitude more than lithium batteries. The nanomaterials also make ideal conductors because they move electricity along much more efficiently than ordinary conductors, Cui said.
The flexibility of paper allows for many clever applications. “If I want to paint my wall with a conducting energy storage device,” Cui said, “I can use a brush.” In his lab, he demonstrated the battery by connecting it to an LED (light-emitting diode), which glowed brightly.
Posted by Benjamin Roudenis on December 22, 2009 0 comments
Researchers knew that the information carried in light pulses could be transferred to clouds of ultracold atoms, called Bose-Einstein condensates. In this technique, a laser called a control laser prepares the atomic cloud for an incoming light beam. As the photons fly in, they leave an imprint in a subset of the atoms. This imprint, stored in a quantum property known as spin, contains all the relevant information needed to reconstitute the light beam. But the imprint is fragile and deteriorates in milliseconds. The light’s information is lost as other atoms in the cloud interfere with the imprint.
Lene Hau of Harvard University and colleagues overcame this problem by sequestering the matter imprint from the rest of the atoms in the cloud. The team shone a pulse of laser light — which looks like the yellow light from street lamps, Hau says — into a small cloud of sodium atoms. A three-microsecond pulse produced a stretch of light about a kilometer long, but as the pulse entered the atom cloud, it began to compress. Like an accordion closing, the light folded up and crammed itself into a space just 0.02 millimeters long. The spin states of the sodium atoms in the light’s path were changed, forming the matter imprint. By turning off the control laser, the researchers were able to freeze the matter imprint.
Next, the researchers strengthened the magnetic field applied to the atom cloud to protect the imprint from interfering atoms. At a certain magnetic field, Hau says, interactions between the imprint and the rest of the atoms start to become repulsive, and the imprint separates from the cloud like a drop of oil in water. “This matter imprint digs a little hole for itself in the condensate,” Hau says. “It can snugly sit there for long periods of time.”
After waiting 1.5 seconds, the team revived the light beam. First, the researchers coaxed the matter imprint to the outside of the cloud by changing the magnetic field, and then they turned the control laser back on. The light beam that emerged from the atom cloud was weaker than the light beam that went in but similar in other regards, such as frequency and polarization, Hau says. Improving the stability of the magnetic field will likely lead to longer storage times, she adds.
