Πριν από 15 χρόνια
‘Mind Uploading’ & Digital Immortality May Be Reality By 2030 : Dr. Michio Kaku
There are two major questions surrounding the concept of mind uploading. There is the question of feasibility: Can we build a model of a brain complete enough to allow a conscious mind to emerge? The other question is concerned with identity. Some people argue that, if a copy of a conscious mind is identical by all measures (ignoring the fact that one is biological and the other is neuromorphic software/hardware) it should be thought of as a continuation of the mind that was mapped and uploaded. Others argue that a copy cannot be considered the same as the original, so the newly awakened consciousness must be another person.
A new way to make laser-like beams using 1,000x less power
With precarious particles called polaritons that straddle the worlds of light and matter, University of Michigan researchers have demonstrated a new, practical and potentially more efficient way to make a coherent laser-like beam.
They have made what's believed to be the first polariton laser that is fueled by electrical current as opposed to light, and also works at room temperature, rather than way below zero.
Those attributes make the device the most real-world ready of the handful of polariton lasers ever developed. It represents a milestone like none the field has seen since the invention of the most common type of laser – the semiconductor diode – in the early 1960s, the researchers say. While the first lasers were made in the 1950s, it wasn't until the semiconductor version, fueled by electricity rather than light, that the technology took off.
This work could advance efforts to put lasers on computer circuits to replace wire connections, leading to smaller and more powerful electronics. It may also have applications in medical devices and treatments and more.
The researchers didn't develop it with a specific use in mind. They point out that when conventional lasers were introduced, no one envisioned how ubiquitous they would become. Today they're used in the fiber-optic communication that makes the Internet and cable television possible. They are also in DVD players, eye surgery tools, robotics sensors and defense technologies, for example.
A polariton is part light and part matter. Polariton lasers harness these particles to emit light. They are predicted to be more energy efficient than traditional lasers. The new prototype requires 1,000 times less electricity to operate than its conventional counterpart made of the same material.
"This is big," said Pallab Bhattacharya, the Charles M. Vest Distinguished University Professor of Electrical Engineering and Computer Science and the James R. Mellor Professor of Engineering at U-M. "For the past 50 years, we have relied on lasers to make coherent light and now we have something else based on a totally new principle."
Bhattacharya's system isn't technically a laser. The term was initially an acronym for Light Amplification by Stimulated Emission of Radiation. Polariton lasers don't stimulate radiation emission. They stimulate scattering of polaritons.
In a typical laser, light—or more often electrical current— is pumped into a material called a gain medium that's designed to amplify the signal. Before the pumping begins, most of the electrons in the gain medium are in their least energetic state, also known as the ground state. Once the light or current hits them, the electrons absorb that energy and move to a higher-energy state. At some point, more electrons are high-energy than are low-energy and the device is said to have achieved a "population inversion." Now any light or current that goes in has the opposite effect on the excited electrons. It kicks them down to the ground state and releases pent-up light in the process.
Polariton lasers don't rely on these population inversions, so they don't need a lot of start-up energy to excite electrons and then knock them back down. "The threshold current can be very small, which is an extremely attractive feature," Bhattacharya said.
He and his team paired the right material – the hard, transparent semiconductor gallium nitride – with a unique design to maintain the controlled circumstances that encourage polaritons to form and then emit light.
How it works
A polariton is a combination of a photon or light particle and an exciton – an electron-hole pair. The electron is negatively charged and the hole is technically the absence of an electron, but it behaves as if it were positively charged. Excitons will only fuse with light particles under just the right conditions. Too much light or electrical current will cause the excitons to break down too early. But with just enough, polaritons will form and then bounce around the system until they come to rest at their lowest energy level in what Bhattacharya describes as a coherent pool. There, the polaritons decay and in the process, release a beam of single-colored light.
The beam they demonstrated was ultraviolet and very low power – less than a millionth of a watt. For context, the laser in a CD player is about one-thousandth of a watt.
"We're thrilled," said Thomas Frost, a doctoral student in electrical and computer engineering. "This is the first really practical polariton laser that could be used on chip for real applications."
The design the team used helped them achieve the beam with an electrical rather than light input signal. Getting the electrical current into the system requires electrodes sandwiching the gallium nitride and several layers of mirrors to render the electrical signal useable. Other groups' approaches put the electrodes outside the mirrors. Bhattacharya said it was tough to get the signal strong enough under those circumstances. So he deconstructed the sandwich. He put the mirrors on the sides of the gallium nitride and left the electrodes on the top and bottom.
Read more at: http://phys.org/news/2014-06-laser-like-1000x-power.html#jCp
Just Add Water, and Silicon Folds Into Origami Shapes
Researchers created microscopic cubes, pyramids, half soccer-ball-shaped bowls
and long triangular Toblerone-like structures, all of which fold themselves when
wetted by a drop of water. Credit: A. Legrain, et. al, University of Twente
Remember those elementary geometry lessons that involved cutting out a pattern from a worksheet and folding along the dotted lines to create a cube, cone or cylinder? Well, fully grown scientists are still doing the same thing, only on a microscopic scale.
Researchers from the University of Twente in the Netherlands have created self-folding, microscopic structures out of silicon nitrate. When the silicon is exposed to water, like magic, the flat cutouts fold into cubes, hexagonal bowls, pyramids and even Toblerone-shaped triangular tubes, all no bigger than a grain of sand.
The research team’s shapes could someday be deployed in a variety of biomedical applications where stealth and accuracy are desired.
Knowing How to Fold’em
To coax a 2-D silicon cutout into 3-D, researchers rely on the cohesive properties of water molecules. A microscopic water droplet beneath the silicon causes the creases to pull together to create the geometric object.
Researchers showed they could vary the amount of water in channels beneath the silicon to open and close the shape up to 60 times without showing signs of wear. Although this team wasn’t the first to demonstrate hydro-folding silicon, they were the first to develop a replicable, controllable technique to deliver the water. Up to now, scientists added droplets of water by hand, and their shapes could only be folded once.
They described their water-based folding system in theJournal of Applied Physics.
Shaping Up, and Shipping Out
Researchers believe the new folding system will make assembling tiny shapes cheaper and thus more practical. They believe these microscopic structures could be used to deliver medication in a targeted fashion, or to perform micro-biopsies.
Check out the video below to see how water and silicon come together to work their magic.
3000 year old trousers discovered in Chinese grave oldest ever found
A team of researchers working in the ancient Yanghai graveyard in China's Tarim Basin has uncovered what appears to be the earliest example of trouser wearing. The research team has published a paper in the journal Quaternary International describing the pants and why they were likely developed to assist with riding horses.
The Tarim Basin in western China is host to the famous Yanghai tombs, a large ancient burial ground that dates back thousands of years—thus far over 500 individual gravesites have been excavated. In this latest find, two adult males (believed to be herders and warriors) both approximately 40 years old at the time of death, were wearing trousers. Carbon dating put the age of the material at approximately 3000 years ago, making the find the oldest known instance of trouser wearing.
In the tomb, along with the bodies, were a horse bit made of wood, a whip, a bow and a battle-axe. These artifacts along with the cut of the pants, suggest the trousers were created and worn to allow for easier horse riding over long periods of time. They also suggest that trouser creation had matured to a level that allowed for custom tailoring. Both specimens were created from three pieces of material (sized to fit a particular individual) one for each leg and a crotch piece—both also had an associated belt made of strings. No cutting was required. Each pant leg also had cross stitching that appeared to serve a purely decorative function.
Many historians believe that trousers were invented as a means of riding horses—riding for a long time can cause skin irritation and discomfort. The trousers worn by horse riders likely migrated to other people, the theory goes, who chose to adopt them for unknown reasons. Its likely modifications were made because riding pants are not particularly comfortable for walking or engaging in everyday life. Prior to trousers, people of both genders tended to wear tunics, robes, togas, etc. It is also generally believed that horse riding by humans began approximately 4000 years ago, which suggests trouser wearing began long before the two men in the Yanghai gravesite donned theirs.
More information: The invention of trousers and its likely affiliation with horseback riding and mobility: A case study of late 2nd millennium BC finds from Turfan in eastern Central Asia, Quaternary International, Available online 22 May 2014 dx.doi.org/10.1016/j.quaint.2014.04.056
Abstract
Here, we present the first report on the design and manufacturing process of trousers excavated at Yanghai cemetery (42°48′–42°49′N, 89°39′–89°40′E) near the Turfan oasis, western China. In tombs M21 and M157 fragments of woollen trousers were discovered which have been radiocarbon dated to the time interval between the 13th and the 10th century BC. Their age corresponds to the spread of mobile pastoralism in eastern Central Asia and predates the widely known Scythian finds. Using methods of fashion design, the cut of both trousers was studied in detail. The trousers were made of three independently woven pieces of fabric, one nearly rectangular for each side spanning the whole length from waistband to hemline at the ankle and one stepped cross-shaped crotch-piece which bridged the gap between the two side-pieces. The tailoring process did not involve cutting the cloth: instead the parts were shaped on the loom, and they were shaped in the correct size to fit a specific person. The yarns of the three fabrics and threads for final sewing match in color and quality, which implies that the weaver and the tailor was the same person or that both cooperated in a highly coordinated way. The design of the trousers from Yanghai with straight-fitting legs and a wide crotch-piece seems to be a predecessor of modern riding trousers. Together with horse gear and weapons as grave goods in both tombs our results specify former assumptions that the invention of bifurcated lower body garments is related to the new epoch of horseback riding, mounted warfare and greater mobility. Trousers are essential part of the tool kit with which humans improve their physical qualities.
Read more at: http://phys.org/news/2014-06-year-trousers-chinese-grave-oldest.html#jCpHere, we present the first report on the design and manufacturing process of trousers excavated at Yanghai cemetery (42°48′–42°49′N, 89°39′–89°40′E) near the Turfan oasis, western China. In tombs M21 and M157 fragments of woollen trousers were discovered which have been radiocarbon dated to the time interval between the 13th and the 10th century BC. Their age corresponds to the spread of mobile pastoralism in eastern Central Asia and predates the widely known Scythian finds. Using methods of fashion design, the cut of both trousers was studied in detail. The trousers were made of three independently woven pieces of fabric, one nearly rectangular for each side spanning the whole length from waistband to hemline at the ankle and one stepped cross-shaped crotch-piece which bridged the gap between the two side-pieces. The tailoring process did not involve cutting the cloth: instead the parts were shaped on the loom, and they were shaped in the correct size to fit a specific person. The yarns of the three fabrics and threads for final sewing match in color and quality, which implies that the weaver and the tailor was the same person or that both cooperated in a highly coordinated way. The design of the trousers from Yanghai with straight-fitting legs and a wide crotch-piece seems to be a predecessor of modern riding trousers. Together with horse gear and weapons as grave goods in both tombs our results specify former assumptions that the invention of bifurcated lower body garments is related to the new epoch of horseback riding, mounted warfare and greater mobility. Trousers are essential part of the tool kit with which humans improve their physical qualities.
Scientists find stronger 3-D material that behaves like graphene
Scientists at Oxford, SLAC, Stanford and Berkeley Lab have discovered
that a sturdy 3-D material, cadmium arsenide, mimics the
electronic behavior of 2-D graphene. This illustration depicts fast-moving,
massless electrons inside the material. The discovery could lead to new
and faster types of electronic devices. Credit: Greg Stewart/SLAC
Scientists have discovered a material that has the same extraordinary electronic properties as 2-D graphene, but in a sturdy 3-D form that should be much easier to shape into electronic devices such as very fast transistors, sensors and transparent electrodes.
The material, cadmium arsenide, is being explored independently by three groups, one of which includes researchers at the University of Oxford, SLAC, Stanford and Lawrence Berkeley National Laboratory who described their results in a paper published May 25 in Nature Materials.
"Now more and more people realize the potential in the science and technology of this particular material. This growing interest will promote rapid progress in the field – including the exploration of its use in functional devices and the search for similar materials," said Yulin Chen of the University of Oxford, who led the research.
The group's work builds on its earlier studies of a sodium bismuth compound that also mimics graphene but turns to powder when exposed to air. Both compounds had been predicted by co-authors Zhong Fang and Xi Dai, theoretical physicists from the Chinese Academy of Sciences, who suggested that cadmium arsenide, which is used in detectors and sensors, would provide the same properties in a much more stable form.
Their prediction proved correct, said Zhongkai Liu, the paper's first author and a graduate student at SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC. "The environmental stability of cadmium arsenide allows us to explore it very systematically, and makes it easier to study," he said.
Graphene is a one-atom-thick sheet of carbon atoms peeled from a piece of graphite, which is familiar as the lead in pencils. One of its hallmarks is the weird behavior of its electrons: When confined to this thin layer of regularly spaced atoms, these lightweight particles act as if they have no mass at all. This allows them to zip through the material much faster than usual. The scientists who first isolated graphene in 2004 were awarded the Nobel Prize in Physics; and researchers have been racing to explore its properties and find practical uses for it ever since.
One such quest has been to find graphene-like materials that are three-dimensional, and thus much easier to craft into practical devices. Two other international collaborations based at Princeton University and in Dresden, Germany, have also been pursuing cadmium arsenide as a possibility. One published a paper on its results in the May 7 issue of Nature Communications, and the other has posted an unpublished paper on the preprint server arXiv.
Chen's group made samples of cadmium arsenide at Oxford and tested them at the Diamond Light Source in the United Kingdom and at Berkeley Lab's Advanced Light Source.
"We think this family of materials can be a good candidate for everyday use," Chen said, "and we're working with theorists to see if there are even better materials out there. In addition, we can use them as a platform to create and explore even more exotic states of matter; when you open a door, you find there are many other doors behind it."
The research team included Zhi-Xun Shen, a professor at SLAC and Stanford and SLAC's advisor for science and technology; Zahid Hussain, senior staff scientist at Berkeley Lab; and other researchers from SIMES, Berkeley Lab, Oxford University, Fudan University in Shanghai, the Chinese Academy of Sciences and Diamond Light Source. The work was partially funded by the U.S. Department of Energy Office of Science and the Defense Advanced Research Projects Agency (DARPA) Mesodynamic Architectures program.
http://phys.org/
