Archive for 2 de outubro de 2008

Tech Tips for the Basic Computer User

“One of these days, I’m going to write a book called, ‘The Basics.’ It’s going to be a compendium of the essential tech bits that you just assume everyone knows–but you’re wrong.
(I’ll never forget watching a book editor at a publishing house painstakingly drag across a word in a word processor to select it. After 10 minutes of this, I couldn’t stand it. ‘Why don’t you just double-click the word?’ She had no clue you could do that!)”
Many readers chimed in with other “basics” that they assumed every computer user knew–but soon discovered that what’s common knowledge isn’t the same as universal knowledge.

Veja o material completo no Blog de DAVID POGUE


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A simpler way to test quantum computers

Physicists in Canada have invented a new way of testing optical components that could someday be used to build quantum computers. They claim that their technique is much simpler than conventional tests because it uses standard laser light, rather than relying on the creation of photons in special quantum states.
A quantum computer could, at least in principle, exploit the weird laws of quantum mechanics to vastly outperform classical computers on certain tasks. In such a computer, data would be input and stored in terms of quantum states — such as the polarization of individual photons. These data would be processed by devices that involve transitions in quantum systems, such as the absorption and emission of photons by a single atom.

Veja a matéria completa em http://physicsworld.com/cws/article/news/36028

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Magnetization vector manipulation by electric fields
D. Chiba, M. Sawicki, Y. Nishitani, Y. Nakatani, F. Matsukura & H. Ohno

Conventional semiconductor devices use electric fields to control conductivity, a scalar quantity, for information processing. In magnetic materials, the direction of magnetization, a vector quantity, is of fundamental importance. In magnetic data storage, magnetization is manipulated with a current-generated magnetic field (Oersted–Ampère field), and spin current is being studied for use in non-volatile magnetic memories. To make control of magnetization fully compatible with semiconductor devices, it is highly desirable to control magnetization using electric fields. Conventionally, this is achieved by means of magnetostriction produced by mechanically generated strain through the use of piezoelectricity. Multiferroics have been widely studied in an alternative approach where ferroelectricity is combined with ferromagnetism. Magnetic-field control of electric polarization has been reported in these multiferroics using the magnetoelectric effect, but the inverse effect—direct electrical control of magnetization—has not so far been observed. Here we show that the manipulation of magnetization can be achieved solely by electric fields in a ferromagnetic semiconductor, (Ga,Mn)As. The magnetic anisotropy, which determines the magnetization direction, depends on the charge carrier (hole) concentration in (Ga,Mn)As. By applying an electric field using a metal–insulator–semiconductor structure, the hole concentration and, thereby, the magnetic anisotropy can be controlled, allowing manipulation of the magnetization direction.

Texto completo em http://www.nature.com/nature/journal/v455/n7212/full/nature07318.html
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Brazil braced for unexpected oil wealth

At a time when most countries are struggling with ageing oilfields, Brazil is debating a new future as an oil exporter following the recent discovery of world-class reservoirs off its coast.
President Luiz Inácio Lula da Silva (Lula) has appointed a cabinet-level committee to come up with recommendations on proposals such as the creation of a state-owned company to manage the development, and a national ‘rainy-day’ fund for collecting and disbursing the revenue. The committee is expected to report later this week, but Lula is said to favour both approaches, and says that he wants to see the money invested in education and social programmes.
(Veja a material completa em http://www.nature.com/news/2008/080924/full/455438b.html).

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Nanoscale magnetic sensing with an individual
electronic spin in diamond

Detection of weak magnetic fields with nanoscale spatial resolution
is an outstanding problem in the biological and physical
sciences. For example, at a distance of 10 nm, the spin of a single
electron produces a magnetic field of about 1 mT, and the corresponding
field from a single proton is a few nanoteslas. A sensor
able to detect such magnetic fields with nanometre spatial resolution
would enable powerful applications, ranging from the detection
of magnetic resonance signals from individual electron or
nuclear spins in complex biological molecules to readout of classical
or quantum bits of information encoded in an electron or
nuclear spin memory. Here we experimentally demonstrate an
approach to such nanoscale magnetic sensing, using coherent
manipulation of an individual electronic spin qubit associated
with a nitrogen-vacancy impurity in diamond at room temperature.
Using an ultra-pure diamond sample, we achieve detection
of 3 nT magnetic fields at kilohertz frequencies after 100 s of averaging.
In addition, we demonstrate a sensitivity of 0.5 mTHz1/2 [microtesla.(Hz na potência -1/2)]
for a diamond nanocrystal with a diameter of 30 nm.
Este artigo de J. R. Maze et al. e outros sobre nanomagnetismo encontram-se em: http://www.nature.com/nature/journal/v455/n7213.

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