The Periodic Table Of Videos
The Periodic Table Of Videos is an experiment by Professor Martyn Poliakoff of the University of Nottingham, UK.
                  |
 Net World Directory Your personal directory for the internet | ||
| Net World Directory: Archives of chemistry blog |
 | ||
Archives Of Chemistry Blog From NetworlddirectorySubscribe To Chemistry Blog RSS Feed 
The Periodic Table Of Videos is an experiment by Professor Martyn Poliakoff of the University of Nottingham, UK. Creating unconventional metals
The magnetic bar magnets (called "magnetic moments") associated with the mobile electrons (red arrows) responsible for electrical conduction and manganese atoms (green arrows) in manganese doped iron silicide (Fe1-xMnxSi). This figure depicts the coupling of the magnetic moments as the temperature is reduced from room temperature (top of the figure) where the magnetic dipoles are independent, to very low temperature (bottom of the figure) where coupling between the dipoles creates regions where the moments add to zero (light blue region).
The new material exists in a quantum halfway house between magnet and semiconductor - in the same way that much more complex materials such as ceramics which exhibit high temperature superconductivity exist in quantum halfway houses between metals and magnetic insulators. The research is of fundamental importance because it demonstrates, for the first time, a simple recipe for reaching this halfway house, whilst also suggesting new mechanisms for controlling electrical currents and magnetism in semiconductor devices. Professor J.F. DiTusa of Louisiana State University and a co-author of the paper said: "It's amazing that something which was thought to exist theoretically in mathematical physics could actually be found in an alloy which was simply formed by melting together a few common elements"......... Radicals Shake Up Molecules
The illustration depicts an unexcited deuterium molecule--a form of molecular hydrogen composed of two deuterium, or heavy hydrogen, atoms. The interactions of this molecule with a single hydrogen atom offer the first glimpse of the newly coined "Tug o' War Mechanism," which describes how the transfer of energy between colliding molecules affects the collision behavior. Stanford researchers, along with international collaborators, discovered this fundamental mechanism underlying many inelastic, or energy transferring, collisions in gases and liquids.
Credit: Stuart Greaves, University of Bristol The new experiment, transforming the textbook story, waccording toformed in the lab of Richard Zare, chair of the Department of Chemistry at Stanford University. This work on energy transferring, or inelastic, collisions is featured in the July 3, 2008 issue of the journal Nature. "How energy transfer occurs in molecular collisions is a topic of deep interest to chemists, for energy transfer is often the precursor to chemical transformations," Zare said. "This is the reason why I regard finding a new mechanism for energizing molecules through collisions to be of such potential importance". "The work by Zare and colleagues shows an interesting and unexpected result," shared Charles Pibel, director of the Physical Chemistry Program at the National Science Foundation (NSF). "The conventional wisdom had been that most collisions between molecules excite vibrational motion through a hard impact, like a piano's hammer striking a string." But instead of molecules impacting and deflecting backwards, the Tug o' War Mechanism stretches the molecule and then releases it, starting the molecule rattling. The effect is "more like a violinist, plucking a string, pizzicato." In the collisions studied by the Zare group, a lone hydrogen atom tugs on one end of a deuterium molecule and lets go, exciting the molecular deuterium into vibration......... Physicists create millimeter-sized 'Bohr atom'
Using laser beams and electric fields, Rice physicists coaxed a point-like, "localized" electron to orbit far from the nucleus of a potassium atom.
Credit: Jeff Mestayer/Rice University The research is available online in Physical Review Letters Bohr offered the first successful theoretical model of the atom in 1913, suggesting that electrons traveled in orbits around the atom's nucleus like planets orbiting a star. Bohr's model led to a deeper understanding of both the chemical and optical properties of atoms and won him a Nobel Prize in 1922. But his notion of electrons traveling in discrete orbits was eventually displaced by quantum mechanics, which revealed that electrons don't have precise positions but are instead distributed in wave-like patterns. "In a sufficiently large system, the quantum effects at the atomic scale can transition into the classical mechanics found in Bohr's model," said lead researcher Barry Dunning, Rice's Sam and Helen Worden Professor of Physics and Astronomy. "Using highly excited Rydberg atoms and a series of pulsed electric fields, we were able to manipulate the electron motion and create circular, planet-like states"......... Quantum computing breakthrough
A new hybrid atom
In a Nature Physics journal paper currently online, the scientists describe how they have created a new, hybrid molecule in which its quantum state can be intentionally manipulated - a mandatory step in the building of quantum computers. "Up to now large-scale quantum computing has been a dream," says Gerhard Klimeck, professor of electrical and computer engineering at Purdue University and associate director for technology for the national Network for Computational Nanotechnology. "This development may not bring us a quantum computer 10 years faster, but our dreams about these machines are now more realistic". The workings of traditional computers haven't changed since they were room-sized behemoths 50 years ago; they still use bits of information, 1s and 0s, to store and process information. Quantum computers would harness the strange behaviors found in quantum physics to create computers that would carry information using quantum bits, or qubits. Computers would be able to process exponentially more information. If a traditional computer were given the task of looking up a person's phone number in a telephone book, it would look at each name in order until it found the right number. Computers can do this much faster than people, but it is still a sequential task. A quantum computer, however, could look at all of the names in the telephone book simultaneously......... Much-Anticipated Online Mathematics Reference
This visual representation of a Hankel function for complex variables in the NIST Digital Library of Mathematical Functions can be explored in three dimensions by Web users. Hankel functions are solutions of Bessel's differential equation, and they play an important role in many problems of mathematical physics, such as heat conduction and wave propagation.
Credit: NIST The DLMF is designed to be the definitive reference work on the special functions of applied mathematics. Special functions are "special" because they occur very frequently in mathematical modeling of physical phenomena, from atomic physics to optics and water waves. These functions have also found applications in many other areas; for example, cryptography and signal analysis. The DLMF provides basic information needed to use these functions in practice, such as their precise definitions, alternate ways to represent them mathematically, illustrations of how the functions behave with extreme values and relationships between functions......... Lost Reds In Homer Painting
Winslow Homer, "For to Be a Farmer's Boy" (1887). Watercolor from the collection of the Art Institute of Chicago, Gift of Mrs. George T. Langhorne in memory of Edward Carson Waller.
In Homer's watercolor "For to be a Farmer's Boy," painted in 1887, some of the red and yellow pigments have faded in the sky, leaving that area virtually without color. Van Duyne, Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences, is working with Francesca Casadio, a conservation scientist at the Art Institute, to determine what the original colors were. To solve this mystery, they are using surface enhanced Raman spectroscopy (SERS), the analytical technique pioneered by Van Duyne in 1977. SERS uses laser light and nanoparticles of precious metals to interact with molecules to show the chemical make-up of a particular dye. SERS is a variation of Raman spectroscopy, a widely used technique first developed in the 1920s. What sets SERS apart is its ability to analyze extremely minute samples of organic dyes; some samples are so small they cannot be seen by the naked eye......... Prototype Hydrogen Storage Tank
Salvador Aceves (left) and Tim Ross check out the on-board hydrogen storage tank that powers a prototype hybrid vehicle.
Photos by Jacqueline McBride/LLNL Unlike conventional liquid hydrogen (LH2 tanks in prototype cars, the LLNL pressure vessel was parked for six days without venting evaporated hydrogen vapor. The LLNL development has significantly increased the amount of time it takes to start releasing hydrogen during periods of long-term parking, as in comparison to today's liquid hydrogen tanks capable of holding hydrogen for merely two to four days. LH2 tanks hold super-cold liquid hydrogen at around -420 Fahrenheit. Like water boiling in a tea kettle, pressure builds as heat from the environment warms the hydrogen inside. Current automotive LH2 tanks must vent evaporated hydrogen vapor after being parked three to four days, even when using the best thermal insulation available (200 times less conductive than Styrofoam insulation). In recent testing of its prototype hydrogen tank onboard a liquid hydrogen (LH2) powered hybrid, LLNL's tank demonstrated a thermal endurance of six days and the potential for as much as 15 days, helping resolve a key challenge facing LH2 automobiles......... New process could cause titanium price to tumble
Next-generation combat vehicles equipped with titanium alloy doors will provide increased safety for soldiers. The doors are made using low-cost titanium powders and a non-melt consolidation process developed by a team of Oak Ridge National Laboratory researchers that includes Bill Peter of the Materials Science and Technology Division. (Photo by Jason Richards)
That could change, however, with a non-melt consolidation process being developed by Oak Ridge National Laboratory and industry partners. The new processing technique could reduce the amount of energy mandatory and the cost to make titanium parts from powders by up to 50 percent, making it feasible to use titanium alloys for brake rotors, artificial joint replacements and, of significant interest now, armor for military vehicles. "We recently exhibited the new low-cost titanium alloy door made by ORNL for the Joint Light Tactical Vehicle, which is a next-generation combat vehicle," said Bill Peter, a researcher in ORNL's Materials Science and Technology Division. "By using a titanium alloy for the door, BAE Systems was able to reduce the weight of its vehicle yet at the same time decrease the threat of armor-piercing rounds." The lightweight titanium alloy also improves the operation of the door and increases mobility of the vehicle, making it even more useful to the military. Peter noted that the non-melt approach, which includes roll compaction for directly fabricating sheets from powder, press and sinter techniques to produce net shape components and extrusion, offers a number of advantages over traditional melt processing......... Improved Ion Mobility Is Key to New Hydrogen Storage Compound
The atomic structure of the mix of lithium amide with lightweight metal hydrides shows layers of calcium that the lithium ions can sprint through. This facilitates hydrogen storage and release.
Credit: NIST The abundant element hydrogen could play a role in replacing carbon-based fuels for transportation in the future, but scientists first must develop a method to store and release large amounts of the highly flammable, odorless invisible gas economically and safely. There are materials that are known to trap relatively large quantities of hydrogen, at normal pressures, but to date they all require heating to fairly high temperatures to release the hydrogen. Hui Wu, a research associate from the University of Maryland working in a cooperative research program at the NIST Center for Neutron Research, has been investigating a new hydrogen storage compound that mixes lithium amide with lightweight metal hydrides. Lithium amide can hold more than 10 percent of hydrogen by weight, well above the 6 percent target set by the U.S. Department of Energy as a 2010 goal for a hydrogen storage material for transportation. The material absorbs and releases hydrogen reversibly, but both absorbing and releasing the hydrogen requires high temperatures and also produces a toxic byproduct, ammonia......... |
||
| Net World Directory: Navigation |