Twenty young scientists from among those taking part in the National Science Foundation’s (NSF) Faculty Early Career Development Program (CAREER) recently received an additional distinction as winners of the Presidential Early Career Awards for Scientists and Engineers (PECASE) for the 2007 competition.
The PECASE program recognizes outstanding scientists and engineers who, early in their careers, show exceptional potential for leadership at the frontiers of knowledge. This Presidential Award is the highest honor bestowed by the U.S. government on scientists and engineers beginning their independent careers. In addition to the NSF’s winners, there are 48 scientists nominated by other government agencies.
By receiving awards through the CAREER program, the PECASE winners had already demonstrated their success in integrating research and education within the context of the mission of their organization.
“We take great pride in the PECASE winners,” says Kathie L. Olsen, NSF’s deputy director. “It is important to support the transformational research of these beginning scientists, and to foster their work in educational outreach and mentoring.”
Recent simulated earthquake tests conducted by University of California, San Diego engineers are expected to lead to retrofit schemes that make historic buildings safer. The structural engineers tested a structure similar to those that were built in California in the 1920s that have masonry infilled walls and reinforced concrete frames. Based on data collected from tests performed on the world’s only outdoor shake table, the engineers will come up with new seismic assessment tools and critical retrofit designs for these kinds of structures, which were not designed according to current standards. As part of the project, the engineers subjected a Three-story structure with non-ductile reinforced concrete frames with unreinforced masonry infilled walls to shaking representative of a series of different seismic events.
Infill walls can generally improve the seismic safety of a building up to a certain level of earthquake intensity depending on the number of walls present and their locations. Once the earthquake force exceeds the strength of the walls, the failure of such structures could be sudden and catastrophic as demonstrated in the recent UC San Diego tests. Due to the frame-panel interaction, the earthquake load resisting mechanism of these structures is complicated, and it is difficult for engineers to assess their seismic resistance. The objectives of this project are to investigate the resistance of this type of structure under realistic seismic load conditions with large-scale tests and develop and calibrate reliable analytical models to assess their seismic performance.
“We will also look into retrofit methods to push the performance envelope of these structures. In reality, some of these structures may not have sufficient walls to resist earthquake loads or some walls may be missing in critical locations of a building. Hence, we need reliable means to assess and improve their performance,” says Benson Shing, a structural engineering professor at the UC San Diego Jacobs School of Engineering, and the lead researcher on the project.
Currently, there is a lack of reliable analysis methods to evaluate the seismic performance of these older structures and validated retrofit methods to improve their seismic behavior. In California, construction of unreinforced masonry buildings including those with brick infill walls came to a halt after the 1933 Long Beach earthquake, which was a 6.4 magnitude, but many of them still exist today. Although only moderate in terms of magnitude, this earthquake caused serious damage to unreinforced masonry structures on land fill from Los Angeles to Laguna Beach. Property damage was estimated at $40 million, and 115 people were killed.
The impact of this $1.24 million project, funded by the National Science Foundation, is vast since a large number of such structures can be found in the Pacific Northwest, and in the Midwestern and Eastern United States, where big earthquakes could occur even though the recurrence frequency is lower. This type of structural system is also very common in areas of high seismicity around the world, including China and the Mediterranean region.
Comments Off on Harnessing Light to Drive Nanomachines
Science fiction writers have long envisioned sailing a spacecraft by the optical force of the sun’s light. But, the forces of sunlight are too weak to fill even the oversized sails that have been tried. Now a team led by researchers at the Yale School of Engineering & Applied Science has shown that the force of light indeed can be harnessed to drive machines—when the process is scaled to nano-proportions.
Their work opens the door to a new class of semiconductor devices that are operated by the force of light. They envision a future where this process powers quantum information processing and sensing devices, as well as telecommunications that run at ultra-high speeds and consume little power.
The research demonstrates a marriage of two emerging fields of research, nanophotonics and nanomechanics, which makes possible the extreme miniaturization of optics and mechanics on a silicon chip.
The energy of light has been harnessed and used in many ways. The force of light is different—it is a push or a pull action that causes something to move.
“While the force of light is far too weak for us to feel in everyday life, we have found that it can be harnessed and used at the nanoscale,” says team leader Hong Tang, assistant professor at Yale. “Our work demonstrates the advantage of using nano-objects as ‘targets’ for the force of light—using devices that are a billion-billion times smaller than a space sail, and that match the size of today’s typical transistors.”
Until now, light has only been used to maneuver single tiny objects with a focused laser beam, a technique called “optical tweezers.” Postdoctoral scientist and lead author, Mo Li notes, “Instead of moving particles with light, now we integrate everything on a chip and move a semiconductor device.”
“When researchers talk about optical forces, they are generally referring to the radiation pressure light applies in the direction of the flow of light,” states Tang. “The new force we have investigated actually kicks out to the side of that light flow.”
While this new optical force was predicted by several theories, the proof required state-of-the-art nanophotonics to confine light with ultra-high intensity within nanoscale photonic wires. The researchers showed that when the concentrated light was guided through a nanoscale mechanical device, significant light force could be generated—enough, in fact, to operate nanoscale machinery on a silicon chip.
The light force was routed in much the same way electronic wires are laid out on today’s large-scale integrated circuits. Because light intensity is much higher when it is guided at the nanoscale, they were able to exploit the force. “We calculate that the illumination we harness is a million times stronger than direct sunlight,” adds Wolfram Pernice, a Humboldt postdoctoral fellow with Tang.
“We create hundreds of devices on a single chip, and all of them work,” says Tang, who attributes this success to a great optical I/O device design provided by their collaborators at the University of Washington.
It took more than 60 years to progress from the first transistors to the speed and power of today’s computers. Creating devices that run solely on light rather than electronics will now begin a similar process of development, according to the authors.
“While this development has brought us a new device concept and a giant step forward in speed, the next developments will be in improving the mechanical aspects of the system. But,” says Tang, “the photon force is with us.”
While general wisdom says that you look at the eyes first in order to recognize a face, University of California, San Diego computer scientists now report that you look at the nose first.
The nose may be the where the information about the face is balanced in all directions, or the optimal viewing position for face recognition, the researchers from UC San Diego’s Jacobs School of Engineering propose in a paper recently published in the journal Psychological Science.
The researchers showed that people first look just to the left of the center of the nose and then to the center of the nose when trying to determine if a face is one they have seen recently. These two visual “fixations” near the center of the nose are all you need in order to determine if a face is one that you have seen just a few minutes before. Looking at a third spot on the face does not improve face recognition, the cognitive scientists found.
Understanding how the human brain recognizes faces may help cognitive scientists create more realistic models of the brain, models that could be used as tools to train or otherwise assist people with brain lesions or cognitive challenges, explains Janet Hsiao, the first author on the Psychological Science paper and a postdoctoral researcher in the computer science department at UC San Diego.
“The nice thing about models like neural nets is that—unlike computer programs—you can lesion them and they still run, which means you can test them in ways you could never test a human brain,” says Garrison Cottrell, an author on the paper and a computer science professor at UC San Diego’s Jacobs School of Engineering. “Understanding how the brain works is the greatest mystery facing us in this century and that is just what we are trying to do,” states Cottrell, who directs the NSF-funded Temporal Dynamics of Learning Center (TDLC) at UC San Diego.
In the experiments reported in Psychological Science, subjects were shown images of faces they had seen a few minutes prior and images of faces they had never seen. The subjects had to decide in a very short time whether they recognized each face or not. Meanwhile, the researchers used eye tracking technology to monitor where on each face the subjects looked—and how long their eyes stayed at each location.
In particular, the researchers employed an innovative eye tracking approach that allowed them to control how many different places on the face subjects could “fix” their eyes before the image disappeared.
When subjects were allowed to fix their eyes on two different face locations, they performed better on face recognition tasks than when they were given the same amount of time but could only look at one spot on the face. Allowing a third or fourth fixation did not improve performance.
Cottrell explains, “The location of the second fixation, like the first, was almost always near the center of the nose. This means you are just shifting the face you are looking at on your retina a bit. This shift changes which neurons are firing in your retina and therefore changes the neurons in the cortex that the visual pattern goes to.”
Researchers from the University of New South Wales (UNSW) in Australia have found that while Internet searches do bring up a variety of useful materials, people pay more attention to information that matches their pre-existing beliefs.
“Even if people read the right material, they are stubborn to changing their views,” says author and UNSW Professor Enrico Coiera. “This means that providing people with the right information on its own may not be enough.”
The research considered how people use Internet search engines to answer health questions.
“We know that the Web is increasingly being used by people to help them make healthcare decisions,” says Coiera. “We know that there can be negative consequences if people find the wrong information, especially as people in some countries can now self-medicate by ordering drugs online.”
“Our research shows that, even if search engines do find the ‘right’ information, people may still draw the wrong conclusions-in other words, their conclusions are biased.”
What also matters is where the information appears in the search results and how much time a person spends looking at it, according to the research, which has been published in the Journal of the American Medical Informatics Association.
“The first or the last document the user sees has a much greater impact on their decisions,” states Coiera, who is the director of the Centre for Health Informatics at UNSW.
Dr. Annie Lau worked with Professor Coiera to design an interface to help people make sense of the information which they are presented with and to break down these decision biases.
“The new search engine interface we have designed could be a part of any search engine and allows people to organize the information they find, and as a result organize their thoughts better,” says Coiera.
While the research was conducted in the area of health, Coiera says the results-and the technology-are applicable to other fields too. The research on the interface will be publicly available within a year.