Tuesday, August 16, 2011
As the sizes of electronic components shrink, soon down to the size of single atoms or molecules, quantum interactions become ever more important. Consequently, enhanced knowledge and exploitation of quantum effects is essential. Researchers at the Joint Quantum Institute (JQI) in College Park, Maryland, operated by the University of Maryland and the National Institute of Standards and Technology (NIST), and at Georgetown University have uncovered evidence for a long-sought-after quantum state of matter, a spin liquid (more on quantum spin-liquid see this article).
The research was performed by JQI postdoctoral scientists Christopher Varney and Kai Sun, JQI Fellow Victor Galitski, and Marcos Rigol of Georgetown University. The results appear in an editor-recommended article in the 12 August issue of the journalPhysical Review Letters.
You can't pour a spin liquid into a glass. It's not a material at all, at least not a material you can touch. It is more like a kind of magnetic disorder within an ordered array of atoms. Nevertheless, it has many physicists excited.
To understand this exotic state of matter, first consider the concept of spin, which is at the heart of all magnetic phenomena. For instance, a refrigerator magnet, at the microscopic level, consists of trillions of trillions of iron atoms all lined up. Each of these atoms can be thought of loosely as a tiny spinning ball. The orientation of that spin is what makes the atom into a tiny magnet. The refrigerator magnet is an example of a ferromagnet, the ferro part coming from the Latin word for iron. In a ferromagnet, all the atomic spins are lined up in the same way, producing a large cooperative magnetic effect.
Important though they may be, ferromagnets aren't the only kind of material where magnetic interactions between spins are critical. In anti-ferromagnets, for instance, the neighboring spins are driven to be anti-aligned. That is, the orientations of the spins alternate up and down (see top picture in figure). The accumulative magnetic effect of all these up and down spins is that the material has no net magnetism. The high-temperature superconducting materials discovered in the 1980s are an important example of an anti-ferromagnetic structure.
More complicated and potentially interesting magnetic arrangements are possible, which may lead to a quantum spin liquid. Imagine an equilateral triangle, with an atom (spin) at each corner. Anti-ferromagnetism in such a geometry would meet with difficulties. Suppose that one spin points up while a second spin points down. So far, so good. But what spin orientation can the third atom take? It can't simultaneously anti-align with both of the other atoms in the triangle. Physicists employ the word "frustration" to describe this baffling condition where all demands cannot be satisfied. Read more to learn how physicist address this 'frustration' in this review from which this post is created.
Thursday, August 11, 2011
|In the early hours of Tuesday morning, our nearest star put on a show that won't be forgotten for a long, long time. Under the ever-watchful eyes of an armada of solar observatories, the sun unleashed an M2-class solar flare|
|This spectacular high definition image of the sun was captured by NASA's Solar Dynamics Observatory (SDO) just as sunspot 1087 was rotating out of view. Although it will soon disappear behind the sun, this sunspot region isn't going quietly|
|On April 2, NASA's Solar Dynamics Observatory (SDO) captured this rare view of the sun. Only twice a year, SDO enters an "eclipse season" when the Earth blocks its otherwise uninterrupted view of our nearest star. For up to 72 minutes a day, an ominous shadow can be seen to obscure the otherwise high-definition view of the solar surface|
|Highest resolution photograph of the sun available to date, part of a brand new series of NASA Solar Dynamics Observatory (SDO) observations.|
Monday, August 8, 2011
Monday, August 1, 2011
|Apparatus from the original 1853 paper in which the Wiedemann-Franz Law was first established. (Credit: Image courtesy of University of Bristol)|
A violation of one of the oldest empirical laws of physics has been observed by scientists at the University of Bristol. Their experiments on purple bronze, a metal with unique one-dimensional electronic properties, indicate that it breaks the Wiedemann-Franz Law.
In 1996, American physicists C. L. Kane and Matthew Fisher made a theoretical prediction that if you confine electrons to individual atomic chains, the Wiedemann-Franz law could be strongly violated. In this one-dimensional world, the electrons split into two distinct components or excitations, one carrying spin but not charge (the spinon), the other carrying charge but not spin (the holon). When the holon encounters an impurity in the chain of atoms it has no choice but for its motion to be reflected. The spinon, on the other hand, has the ability to tunnel through the impurity and then continue along the chain. This means that heat is conducted easily along the chain but charge is not. This gives rise to a violation of the Wiedemann-Franz law that grows with decreasing temperature.
The experimental group, led by Professor Nigel Hussey of the Correlated Electron Systems Group at the University of Bristol, tested this prediction on a purple bronze material comprising atomic chains along which the electrons prefer to travel.
Not only does this remarkable capability of this compound to conduct heat have potential from a technological perspective, such unprecedented violation of the Wiedemann-Franz law provides striking evidence for this unusual separation of the spin and charge of an electron in the one-dimensional world.
Professor Hussey said: "One can create purely one-dimensional atomic chains on substrates, or free-standing two-dimensional sheets, like graphene, but in a three-dimensional complex solid, there will always be some residual coupling between individual chains of atoms within the complex that allow the electrons to move in three-dimensional space.
|Graphene is a two-dimensional crystal consisting of a single layer of carbon atoms arranged hexagonally. (Credit: Berkeley Lab/U.S. Department of Energy)|
The Nobel prize winning scientists Professor Andre Geim and Professor Kostya Novoselov who discovered world's thinnest material graphene are now at the process of using it to produce fastest electronics. Graphene is a novel two-dimensional material which can be seen as a monolayer of carbon atoms arranged in a hexagonal lattice. It possesses a number of unique properties, such as extremely high electron and thermal conductivities due to very high velocities of electrons and high quality of the crystals, as well as mechanical strength.
Well, the opportunities for a faster electronics with devices like touch-screens, ultra-fast transistors and photodetectors are accelerated with such discoveries like graphenes and one-dimensional material like purple bronze!
Sunday, July 31, 2011
Artist impression of Pluto and largest moon Charon from the surface of either Nix or Hydra, two smaller moons. "P4" is the new addition.
Last week, news broke that a team of astronomers using the Hubble Space Telescope had discovered a new moon in orbit around Pluto.
They were actually looking for signs of a ring system when they stumbled across another tiny object -- now imaginatively called "P4" -- bringing Pluto's moon count to four.
After addition of a new moon, will Pluto be called a planet again? NO... Why? click on the link and Read More in this article.
Thursday, July 21, 2011
Fundamental constants 'change': Gravity weaker, electromagnetic force stronger, according to latest recommended values
The constants, which range from relatively famous (the speed of light) to the fairly obscure (Wien frequency displacement law constant) are adjusted every four years in response to the latest scientific measurements and advances. These latest values arrive on the verge of a worldwide vote this fall on a plan to redefine the most basic units in the International System of Units (SI), such as the kilogram and ampere, exclusively in terms of the fundamental constants.
The values are determined by the Committee on Data for Science and Technology (CODATA) Task Group on Fundamental Constants, an international group that includes NIST members. The adjusted values reflect some significant scientific developments over the last four years.
Wednesday, July 20, 2011
The debate on weather the Multiverse really exist or not is a hot topic since many years. The proponents of parallel universes strike back with multiverse. Read the links for a fascinating overview of these reveling concepts which challenge our perceptions.
Finally a man (Theoretical Physicist) who is a rebel in his own field always challenging his fellow men about current concepts or theories. He even disputed Stephen Hawking about black holes and eventually made him concede with his black hole physics. He is the man behind the development of parallel universe concept again challenging with the concept of a Level 1 multiverse.
We may never be able to grasp that reality. The universe and its ingredients may be impossible to describe unambiguously - Leonard Susskind
Tuesday, July 19, 2011
Neural signature of 'mental time travel': Memories formed in the same context become linked, evidence shows
Almost everyone has experienced one memory triggering another, but explanations for that phenomenon have proved elusive. Now, University of Pennsylvania researchers have provided the first neurobiological evidence that memories formed in the same context become linked, the foundation of the theory of episodic memory. Read More
Which is better, a quick vertical jab on the buttock or the delicately soft entry of a blood sample? Waiting to find out "for what," some are already wondering "how" to use those tiny "molecular syringes" which are carbon nanotubes. With a diameter of less than one millionth of a millimetre (nanometre) and a maximum length of just a few millimetres, the first use that springs to mind when we think of this ethereal tubes -- the smallest ever made by man -- is as potential needles for injecting drugs or genes into sick cells. And if a syringe it is, we had better start thinking about how to use them. Read More
The above picture is an illustration of how a nanorobot or a nanobot injects drug into a red blood cell and Phil Ball, a science writer warns in his column how pictures which are a combination of photographic reality and graphic inventions can persuade us into believing such things!
"We can now monitor how individual cells talk to one another in real-time with unprecedented spatial and temporal resolution," says Jeffrey Karp, senior study author, and co-director of the Center for Regenerative Therapeutics (ReGen Rx) at BWH. "This allows us to understand signaling between cells and interactions with drugs in great detail that should have broad implications for basic science and drug discovery", Read More
Sunday, July 17, 2011
Thursday, July 14, 2011
Delft University of Technology (TU Delft) is currently testing an intelligent street lighting system on its campus, which uses up to 80% less electricity than the current systems and is also cheaper to maintain. The system consists of street lights with LED lighting, motion sensors and wireless communication. This enables the installation to dim the lights when there are no cars, cyclists or pedestrians in the vicinity. Wireless communication between the street lights and a control room is also possible. The system was developed by TU Delft alumnus Management of Technology, Chintan Shah, who won a competition in 2010 with this concept for improving energy efficiency on the university campus.
The pillar ATM, which NCR corp. is designing for rural areas in developing countries such as India and China, is waist high and could be secured to the ground with bolts or weights. The cylindrical shape is designed to minimize places where a crowbar might be applied to pry open the ATM. As an added measure of security, the machine's cash box is designed to collapse in on itself if the ATM is breached.Read More
Monday, July 11, 2011
We've all heard our brain likened to a computer. But professor Jian-Jun Shu and his students at Nanyang Technical University are taking that comparison quite literally.
Shu and his team at the university's School of Mechanical and Aerospace Engineering have proposed a way to use DNA strands for computing operations.
Their article “DNA-Based Computing of Strategic Assignment Problems,” was recently published in the journal Physical Review Letters.
Shu points out that the human body performs computations that are naturally more faster than even the fastest silicon-based computer.
Sunday, July 10, 2011
Saturday, July 9, 2011
Remember how it is to go to a dental teaching institute and become a guinea pig to dental students with all their anxiety of trying to experiment their theory knowledge on us? Well it could sometimes be disastrous combination of shaking hands, confusion and apprehension.
Japan's Showa University for the first time has invented in collaboration with Orient Industry a life-like dental training robot that is capable of mimicking human's gagging reflex, coughing, blinking, sneezing, head shaking and snapping the mouth shut like a real life human. The robot's face is made of silicone which gives a real-life effect. It also is capable of moving its tongue. The speech recognition has enabled the robot to respond to certain instructions. The robot has a name: Showa Hanako-2. And whats more, it can also store and analyse each student's performance and provide feedback through a computer link!
Surely, this will help dental students to learn and trained better with a simulation of real life situation.
Watch this video to witness the superb simulation this 'Showa Hanako 2' provides to a student.
A group of researchers at the Perelman School of Medicine of Pennsylvania University for the first time have succeeded in transforming two different cell-types (astrocyte, a brain cell and a fibroblast, a skin cell) into a heart cell using mRNAs (messenger RNAs are the molecules which contain the blueprints for protein). It is a breakthrough in medicine as it is going to pave the way for cell-based therapy for cardiovascular diseases.
Researchers have used a method called Transcriptome Induced Phenotype Remodeling which is similar to prior nucleus transfer from one cell to another cell which then directs the cell to change the phenotype based on the RNAs that are made. The advantage of this method is that it does not need an intermediate step. This research might make it possible now to repair the injured hearts by replacing lost tissue.
Tuesday, July 5, 2011
This blog will try to give a glimpse of the 'art' or 'skills' used by humans which is influencing man and other living species to adapt to their natural environment. This is a place where my perceptions about how science which provides knowledge is helping/challenging/counterfeiting/ruining/re-creating the natural environment. It might be just reporting the updated news/scoops, sometimes with my opinions or with a review of experts opinion.
My only desire is to share what I learn everyday to everyone else out there!