Eric Sembrat's Test Bonanza

Close to 200 physics college students converged at Georgia Tech for the Conference of Undergraduate Women in Physics (CUWIP) on Jan. 15-17, 2016. CUWIP is a program of the American Physical Society to support the professional growth of undergraduate women in physics. This year marks the first time Georgia Tech hosted the event. In welcoming conference attendees, Georgia Tech College of Sciences Dean Paul M. Goldbart, who is a physicist, expressed joy in being “with my people….People who understand that physics is much more than just another class. It’s a calling, a passion--something that thrills us and excites our hearts, as well as our minds.”

Goldbart acknowledged that women are still underrepresented in physics, as in many other fields. Yet, he said, the physics community has much to celebrate “in the progress that has been achieved” by women in physics “despite the people who have willfully stood in the way or who have failed to acknowledge the serious challenges that remain.”

Participants, including 15 high school students, feasted on scientific talks, poster sessions, and tours of Georgia Tech research facilities. Also on the menu were one-hour workshops covering topics from soft matter physics to dealing with depression. Panel discussions addressed questions such as: Is graduate school right for me? What can I do with a physics degree outside of academia?

Among renowned women physicists who gave plenary talks were

• Ginger Kerrick, NASA’s first non-astronaut capsule communicator, responsible for relaying information from NASA mission control to astronaut crews;
• Jane Rigby, an astrophysicist at the NASA Goddard Space Flight Center, public speaker on astronomy, and blogger at AstroBetter;
• Connie B. Roth, an associate professor of physics at Emory University who specializes in experimental soft condensed matter physics; and
• C. Megan Urry, a professor of physics and astronomy at Yale University and the current president of the American Astronomical Society.

Among the conference highlights was the dinner talk by Sue Payne, recently retired executive from Exxon Mobil Corporation, where she last served as manager of global geoscience. Payne, who earned a B.S. Physics from Georgia Tech, is also a member of the Georgia Tech College of Sciences Advisory Board. She urged participants to

• Let go of the fear of failing.
• Feed your curiosity.
• Act with Integrity.
• Collaborate, collaborate, collaborate.

Payne also gave a shout-out to STEM (science, technology, engineering, mathematics) teachers, saying “we need many more teachers with math and science degrees, who are then paid much more competitively.”

CUWIP also showcased the strength of physics, collaborative research, and interdisciplinary fields at Georgia Tech. The School of Physics has “well-recognized groups in the areas of physics we study,” said Flavio H. Fenton, a Georgia Tech associate professor of physics. “We are unique,” he added, “in having a Physics of Living Systems program, which studies dynamics at all length scales, from subcellular to ecological sizes.” Fenton noted that the idea to host CUWIP came from graduate student Andrea J. Welsh, now in her fourth year of Ph.D. studies. Chair of the CUWIP organizing committee, she works in the CHAOS Lab (CHAOS = Complex Heart Arrhythmias and Other Oscillating Systems), helping to understand the collective behavior or groups of organisms. “I came to Georgia Tech not only for the research,” Welsh said, but also “because the school is very friendly and accommodating.”

Welsh recalled that the first CUWIP she attended, at Yale University in 2009, was where she found the most women scientist together in one room. It was an experience she wanted to share with other young women aspiring for careers in science. “Even at Georgia Tech, a decent-sized institute, I am often the only woman in my physics classes,” she said. “I wanted students who had never seen parts of themselves in their peers and mentors to be able to, and I think in a small way this conference succeeded in achieving that.”

The path to equitable representation of women in many aspects of life is bumpy, and conferences such as CUWIP exist partly to make it smooth. “I find myself asking if our goal as a community should be to render meetings like this unnecessary,” Goldbart told the attendees. “I’m not sure,” he said. “Even when we reach equality of status, perhaps there will remain distinct needs that such meetings can be helpful with.” More importantly, he concluded, it’s really up to women themselves to decide: “It matters what you think. And it matters that you are heard".

Regent's and Institute Professor Uzi Landman received a $900,000 grant from the U.S. Air Force Office of Scientific Research (AFOSR) to explore the foundation of a new theory that describes the chemistry of ultracold atoms by developing a different type of computational theory.

Read more at:
http://www.news.gatech.edu/2015/10/28/entering-strange-world-ultra-cold-chemistry

Having a light touch can make a hefty difference in how well animals and robots move across challenging granular surfaces such as snow, sand and leaf litter. Research reported October 9 in the journal Bioinspiration & Biomimetics shows how the design of appendages – whether legs or wheels – affects the ability of both robots and animals to cross weak and flowing surfaces.

Using an air fluidized bed trackway filled with poppy seeds or glass spheres, researchers at the Georgia Institute of Technology systematically varied the stiffness of the ground to mimic everything from hard-packed sand to powdery snow. By studying how running lizards, geckos, crabs – and a robot – moved through these varying surfaces, they were able to correlate variables such as appendage design with performance across the range of surfaces.

The key measure turned out to be how far legs or wheels penetrated into the surface. What the scientists learned from this systematic study might help future robots avoid getting stuck in loose soil on some distant planet.

“You need to know systematically how ground properties affect your performance with wheel shape or leg shape, so you can rationally predict how well your robot will be able to move on the surfaces where you have to travel,” said Dan Goldman, a professor in the Georgia Tech School of Physics. “When the ground gets weak, certain animals seem to still be able to move around independently of the surface properties. We want to understand why.”

The research was supported by National Science Foundation, Army Research Laboratory and Burroughs Wellcome Fund.

For years, Goldman and colleagues have been using trackways filled with granular media to study the locomotion of animals and robots, but in the past, they had used fluidized bed only to set the initial compaction of the media. In this study, however, they used variations in continuous air flow – introduced through the bottom of the device – to vary the substrate’s resistance to penetration by a leg or wheel.

Goldman compares the trackway to the wind tunnels used for aerodynamic studies.

“By varying the air flow, we can create ground that is very, very weak – so that you sink into it quite easily, like powdery snow, and we can have ground that is very strong, like sand,” he explained. “This gives us the ability to study the mechanism by which animals and robots either succeed or fail.”

Using a bio-inspired hexapedal robot known as Sandbot as a physical model, the researchers studied average forward speed as a factor of ground penetration resistance – the “stiffness” of the sand – and the frequency of leg movement. The average speed of the robot declined as the increased air flow through the trackway made the surface weaker. Increasing the leg frequency makes the speed decrease more rapidly with increasing air flow.

The five animals – with different body plans and appendage features – all did better than the robot, with the best performer being a lizard collected in a California desert. The speed of the C. draconoides wasn’t slowed at all as the surface became easier to penetrate, while other animals saw performance losses of between 20 and 50 percent on the loosening surfaces.

“We think that this particular lizard is well suited to the variety of terrain because it has these ridiculously long feet and toes,” Goldman said. “These feet and toes really enable it to maintain high performance and reduce its penetration into the surface over a wide range of substrate conditions. On the other hand, we see animals like ghost crabs that experience a tremendous loss of performance as the substrate changes, something that was surprising to us.”

The robot lost 70 percent of its speed even with wheels designed to lighten its pressure on the surface.

Skiers and beachcombers can certainly understand why. As the surface becomes easier for a ski or foot to penetrate, more energy is required to move and forward progress slows. Human and skiers haven’t evolved solutions to that problem, but desert-dwelling creatures have. The research, Goldman says, will help us understand how they do it.

“The magic for us is how the animals are so good at this,” he said. “There’s a clear practical application to this. If you can get the controls and morphology right, you could have a robot that could move anywhere, but you have to know what you are doing under different conditions.”

As part of the research, Georgia Tech graduate students Feifei Qian and Tingnan Zhang used a terradynamics approach based on resistive force theory to perform numerical simulations of the robots and animals. They found that their model successfully predicted locomotor performance for low resistance granular states.

“This work expands the general applicability of our resistive force theory of terradynamics,” said Goldman. “The resistive force theory, which allows us to compute forces on limbs intruding into the ground, continues to work even in situations where we didn’t think it would work. It expands the applicability of terradynamics to even weaker states of material.”

In addition to those already mentioned, co-authors include Wyatt Korff from the Howard Hughes Medical Institute in Virginia, Paul Umbanhowar from Northwest University, and Robert Full from the University of California at Berkeley.

This research was supported by the Burroughs Wellcome Fund and by the Army Research Laboratory (ARL) Micro Autonomous Systems and Technology (MAST) Collaborative Technology Alliance (CTA) under cooperative agreement number W911NF-08-2-0004, and by the National Science Foundation Physics of Living Systems CAREER and Student Research Network and ARO Grant No. W911NF-11-1-0514. Any conclusions or opinions expressed are those of the authors and do not necessarily reflect the official views of the sponsoring agencies.

CITATION: Feifei Qian, et al., “Principles of appendage design in robots and animals determining terradynamic performance on flowable ground,” (Bioinspiration & Biomimetics, 2015). http://dx.doi.org/10.1088/1748-3190/10/5/056014

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Eyes will be on the skies Sunday night, for a rare celestial event.
What it is being referred to as may sound like something ripped from a superhero comic book: The supermoon lunar eclipse.

Astronomer Dr. Jim Sowell from the Georgia Tech School of Physics explains what you’ll be able to see with the naked eye.

“A curved shadow moving slowly across the moon. A lot of people think that the moon goes through phases because it’s going into the earth’s shadow, but that’s not the case. The only time the moon goes into the shadow is during an eclipse,” he explains.

So what makes this eclipse even more super?

“The moon’s orbit is not exactly circular,” Dr. Sowell says. “There are times in the moon’s orbit where it’s a little bit closer to the earth.”

This eclipse is happening at time when the moon is nearest to earth, making it appear larger and brighter.

There is another nice thing about this eclipse in particular. It’s happening early enough in the evening that many people will be able to see it. Because of the earth’s alignment the Eastern Unites States is in prime position for viewing. That puts Georgia and Atlanta on the front row.

Dr. Sowell gave us this approximate timing:
9:07 pm: Eclipse begins.
10:11 pm: Moon moves into totality, being completely covered by earth’s shadow.
around 11:30 pm: Moon will begin moving out of shadow.
around 12:30 : Eclipse ends.

Georgia Tech’s School of Physics will host a viewing event Sunday evening open to the public on Tech Green. They will bring a variety of telescopes and point them towards the skies to offer an up-close and in-depth look at the supermoon eclipse.

There may be far fewer galaxies further out in the universe than might be expected, suggests a new study based on simulations conducted on the Blue Waters supercomputer at the National Center for Supercomputing Applications and supported by the Georgia Institute of Technology.

The study, which was published July 1 in Astrophysical Journal Letters and led by Michigan State University, shows the first results from the Renaissance Simulations, a suite of extremely high-resolution adaptive mesh refinement (AMR) calculations of high redshift galaxy formation.

The simulations show hundreds of well-resolved galaxies, allowing researchers to make several novel and verifiable predictions ahead of the October 2018 launch of the James Webb Space Telescope (JWST), a new space observatory that succeeds the Hubble Space Telescope.

“The Hubble Space Telescope can only see what we might call the tip of the iceberg when it comes to taking inventory of the most distant galaxies,” said San Diego Supercomputer Center (SDSC) Director Michael Norman, who was part of the study’s research team. “A key question is how many galaxies are too faint to see. By analyzing these new, ultra-detailed simulations, we find that there are 10 to 100 times fewer galaxies than a simple extrapolation would predict.”

“Our work suggests that there are far fewer faint galaxies than one could previously infer,” said principal investigator and lead author Brian O’Shea, an associate professor at Michigan State. “Observations of high redshift galaxies provide poor constraints on the low-luminosity end of the galaxy luminosity function, and thus make it challenging to accurately account for the full budget of ionizing photons during that epoch.”

Georgia Tech Assistant Professor John Wise wrote the code that made the simulations possible on Blue Waters. He also interpreted the data to make predictions for the JWST, serving as a “simulation architect” by setting the simulation parameters.

Wise and his fellow researchers found that the ultraviolet luminosity function of the simulated galaxies is consistent with observations of redshift galaxy populations at the bright end of the luminosity function and essentially flat rather than rising steeply at lower luminosities.

“The flattening at lower luminosities is a key finding in the study and significant to researchers’ understanding of the reionization of the universe, when the gas in the universe changed from being mostly neutral to mostly ionized,” said Wise, Dunn Family Assistant Professor in Georgia Tech’s School of Physics.

The term ‘reionized’ is used because the universe was ionized immediately after the fiery Big Bang. During that time, ordinary matter consisted mostly of hydrogen atoms with positively charged protons stripped of their negatively charged electrons. Eventually, the universe cooled enough for electrons and protons to combine and form neutral hydrogen. They didn’t give off any optical or UV light, and without that light astrophysicists aren’t able to see traces of how the cosmos evolved during these dark ages using conventional telescopes. The light returned when reionization began.

Because these simulations are so costly to generate, the team moved the entire output of the Renaissance Simulations to SDSC Cloud– some 100 terabytes of data, or the equivalent of about 150,000 audio compact discs. “A data access portal is being set up so that others can investigate their properties in more detail,” added Norman, also a distinguished professor of physics at UC San Diego and a faculty member with the Center for Astrophysics & Space Sciences at the university.

The results are detailed in the paper, titled Probing the Ultraviolet Luminosity Function of the Earliest Galaxies with the Renaissance Simulations.

In an earlier paper, simulations conducted by two researchers who were part of this new study concluded that about 300 million years after the “Big Bang,” the universe was 20 percent ionized, 50 percent ionized at 550 million years, and fully ionized at 860 million years after its creation. 

While the James Webb Space Telescope will give cosmic researchers the ability to view and record substantial numbers of galaxies, the telescope has a relatively small field of view, according to the researchers. As a result, interpretation of any JWST survey must by necessity take into account cosmic variance – the statistical variation in the number of galaxies from place to place. A deeper understanding based on theory may be necessary to correctly interpret high redshift survey results.

The simulations were done on the National Science Foundation-funded Blue Waters supercomputer, one of the largest academic supercomputers in the world.

The research team also included Hao Xu, a postdoctoral research associate with the Center for Astrophysics & Space Sciences, at the University of California, San Diego. The research was funded by the National Science Foundation and NASA.

LIGO will for the first time directly detect gravitational waves, the ripples in the fabric of space-time predicted a century ago by Einstein with his theory of general relativity. Detecting and characterizing gravitational waves will unveil a new perspective of the cosmos, complementing the view provided by electromagnetic waves such as visible light, X-rays, radio, infrared and gamma rays. Cadonati, currently chair of the LIGO Scientific Collaboration data analysis council, has joined the Center for Relativistic Astrophysics (CRA) in the Georgia Tech School of Physics. The center is devoted to interdisciplinary research and education linking astrophysics, astroparticle physics, cosmology and gravitational physics. In addition to Cadonati, the LIGO effort at Georgia Tech will also include Deirdre Shoemaker, an associate professor in the School of Physics and director of the CRA, and will involve close collaboration with Pablo Laguna, chair of the School of Physics.

Read the full story here.