The University of Rochester is one of the nation's leading private research universities, renowned for its commitment to innovation, interdisciplinary collaboration, and academic excellence. Guided by its motto, "Meliora"—Ever Better—the University fosters groundbreaking research and transformative education across its schools and centers.

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What happens when something exceptional gets better? At the University of Rochester we bring together exceptional people—doctors, researchers, inventors, entrepreneurs, artists, musicians, students, and teachers—from across the globe, and we challenge them to become even better.

Animation by Dave Dever, Revel Pix
Music by Shoghi Hayes ’15E
Written and Voiced by Jim Lahue, University of Rochester Medical Center
Produced by Matthew Mann, University Communications, University of Rochester

Making the Exceptional Better

See how this device works: http://www.youtube.com/watch?v=GAmWs6zfTj8

To see how these devices are made, read the PDF of the paper: http://arxiv.org/abs/1306.0863 (hint: there are four mirrors involved)

UPDATE: the paper was published in March 2014 in Applied Optics: http://www.opticsinfobase.org/ao/fulltext.cfm?uri=ao-53-9-1958&id=281980

John Howell, a Professor of Physics at the University of Rochester, decided to tackle an unusual DIY project. With the help of his 14 year-old son, Benjamin, he built three simple, but surprisingly effective optical cloaking devices with inexpensive, off-the-shelf materials.

Cloaking is a common topic both in popular culture and in the scientific community. Cloaking means hiding an object from view at specific frequencies, and different types of cloaking have been recently demonstrated in labs around the world. Howell and his son built three different devices to show that it is possible to do optical, unidirectional cloaking cheaply, and for large objects.

In a paper they recently posted on the online paper depository, arxiv, they explain the strengths and limitations of the three approaches they used. The first device used plexiglass, out of which they fashioned L-shaped containers filled with water. The second used four $3 lenses to show optical cloaking similar to what a group from Cornell University recently showed, except that the Howells demonstrated spatial cloaking instead of temporal cloaking. The third device, which will be familiar to many amateur magicians, used an assembly of inexpensive, hardware-store mirrors (see demo in the video above). In the paper, the Howells stressed that the device, although it has some drawbacks, is "clearly scalable to very large dimensions."

John Howell's usual area of research is in quantum physics, including quantum information, weak measurement, entanglement and slow light. Intrigued by some of the recent cloaking work, he thought he would try a few experiments outside of his normal field with some help from his son.

The single direction in which these can be viewed is probably the biggest limitation, but for some uses that might not be a problem, for example earth-orbiting satellites. Large-scale applications, however, are likely to cost a bit more than the $150 that the Howells spent on this project.


To read more about John Howell's research, see his group's page:
http://www.pas.rochester.edu/~jhgroup/

Music: Doug Munro, "Hoof It"

A Basic Demonstration of Optical Cloaking

To see the latest device using this technology, please visit: https://www.youtube.com/watch?v=QF8qkoIWH64

For more information about John Howell’s research, please visit:
 
http://www.rochester.edu/newscenter/compressive-sensing-provides-new-approach-to-measuring-a-quantum-system/
 
http://www.rochester.edu/news/show.php?id=2723

Researchers at the University of Rochester Create a Three-dimensional,Transmitting, Continuously Multidirectional Cloaking Device

(To read the full press release, visit: http://www.rochester.edu/newscenter/watch-rochester-cloak-uses-ordinary-lenses-to-hide-objects-across-continuous-range-of-angles-70592/)

Inspired perhaps by Harry Potter’s invisibility cloak, scientists have recently developed several ways—some simple and some involving new technologies—to hide objects from view. The latest effort, developed at the University of Rochester, not only overcomes some of the limitations of previous devices, but it uses inexpensive, readily available materials in a novel configuration.
 
“There’ve been many high tech approaches to cloaking and the basic idea behind these is to take light and have it pass around something as if it isn’t there, often using high-tech or exotic materials,” said John Howell, a professor of physics at the University of Rochester. Forgoing the specialized components, Howell and graduate student Joseph Choi developed a combination of four standard lenses that keeps the object hidden as the viewer moves up to several degrees away from the optimal viewing position.

“This is the first device that we know of that can do three-dimensional, continuously multidirectional cloaking, which works for transmitting rays in the visible spectrum,” said Choi, a PhD student at Rochester’s Institute of Optics.

Many cloaking designs work fine when you look at an object straight on, but if you move your viewpoint even a little, the object becomes visible, explains Howell. Choi added that previous cloaking devices can also cause the background to shift drastically, making it obvious that the cloaking device is present.

In order to both cloak an object and leave the background undisturbed, the researchers determined the lens type and power needed, as well as the precise distance to separate the four lenses. To test their device, they placed the cloaked object in front of a grid background. As they looked through the lenses and changed their viewing angle by moving from side to side, the grid shifted accordingly as if the cloaking device was not there.  There was no discontinuity in the grid lines behind the cloaked object, compared to the background, and the grid sizes (magnification) matched.
 
The Rochester Cloak can be scaled up as large as the size of the lenses, allowing fairly large objects to be cloaked. And, unlike some other devices, it’s broadband so it works for the whole visible spectrum of light, rather than only for specific frequencies.

Their simple configuration improves on other cloaking devices, but it’s not perfect. “This cloak bends light and sends it through the center of the device, so the on-axis region cannot be blocked or cloaked,” said Choi. This means that the cloaked region is shaped like a doughnut. He added that they have slightly more complicated designs that solve the problem.  Also, the cloak has edge effects, but these can be reduced when sufficiently large lenses are used.

In a new paper published in the journal Optics Express (http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-24-29465), Howell and Choi provide a mathematical formalism for this type of cloaking that can work for angles up to 15 degrees, or more.  They use a technique called ABCD matrices that describes how light bends when going through lenses, mirrors, or other optical elements.

While their device is not quite like Harry Potter’s invisibility cloak, Howell had some thoughts about potential applications, including using cloaking to effectively let a surgeon “look through his hands to what he is actually operating on,” he said. The same principles could be applied to a truck to allow drivers to see through blind spots on their vehicles.

Howell became interested in creating simple cloaking devices with off-the-shelf materials while working on a holiday project with his children. Together with his 14 year-old son and Choi, he recently published a paper about some of the possibilities, and also demonstrated simple cloaking with mirrors, like magicians would use.

Note: A patent has been filed for this cloaking device. Please contact UR Ventures for additional information: http://www.rochester.edu/ventures/about/who-are-we/

The Rochester Cloak

Scientists at the University of Rochester have used lasers to transform metals into extremely water repellent, or super-hydrophobic, materials without the need for temporary coatings. 

Super-hydrophobic materials are desirable for a number of applications such as rust prevention, anti-icing, or even in sanitation uses. However, as Rochester’s Chunlei Guo explains, most current hydrophobic materials rely on chemical coatings. 

In a paper (http://scitation.aip.org/content/aip/journal/jap/117/3/10.1063/1.4905616) published today in Journal of Applied Physics, Guo and his colleague at the University’s Institute of Optics, Anatoliy Vorobyev, describe a powerful and precise laser-patterning technique that creates an intricate pattern of micro- and nanoscale structures to give the metals their new properties.  This work builds on earlier research by the team in which they used a similar laser-patterning technique that turned metals black (http://www.rochester.edu/news/show.php?id=2701). Guo states that using this technique they can create multifunctional surfaces that are not only super-hydrophobic but also highly-absorbent optically.

Guo adds that one of the big advantages of his team’s process is that “the structures created by our laser on the metals are intrinsically part of the material surface.” That means they won’t rub off. And it is these patterns that make the metals repel water.

“The material is so strongly water-repellent, the water actually gets bounced off. Then it lands on the surface again, gets bounced off again, and then it will just roll off from the surface,” said Guo, professor of optics at the University of Rochester. That whole process takes less than a second. 

The materials Guo has created are much more slippery than Teflon—a common hydrophobic material that often coats nonstick frying pans. Unlike Guo’s laser-treated metals, the Teflon kitchen tools are not super-hydrophobic. The difference is that to make water to roll-off a Teflon coated material, you need to tilt the surface to nearly a 70-degree angle before the water begins to slide off. You can make water roll off Guo’s metals by tilting them less than five degrees.

As the water bounces off the super-hydrophobic surfaces, it also collects dust particles and takes them along for the ride. To test this self-cleaning property, Guo and his team took ordinary dust from a vacuum cleaner and dumped it onto the treated surface. Roughly half of the dust particles were removed with just three drops of water. It took only a dozen drops to leave the surface spotless. Better yet, it remains completely dry. 

Guo is excited by potential applications of super-hydrophobic materials in developing countries. It is this potential that has piqued the interest of the Bill and Melinda Gates Foundation, which has supported the work. 

 “In these regions, collecting rain water is vital and using super-hydrophobic materials could increase the efficiency without the need to use large funnels with high-pitched angles to prevent water from sticking to the surface,” says Guo. “A second application could be creating latrines that are cleaner and healthier to use.”

Latrines are a challenge to keep clean in places with little water. By incorporating super-hydrophobic materials, a latrine could remain clean without the need for water flushing. 
But challenges still remain to be addressed before these applications can become a reality, Guo states. It currently takes an hour to pattern a 1 inch by 1 inch metal sample, and scaling up this process would be necessary before it can be deployed in developing countries. The researchers are also looking into ways of applying the technique to other, non-metal materials. 

Guo and Vorobyev use extremely powerful, but ultra-short, laser pulses to change the surface of the metals. A femtosecond laser pulse lasts on the order of a quadrillionth of a second but reaches a peak power equivalent to that of the entire power grid of North America during its short burst.

Guo is keen to stress that this same technique can give rise to multifunctional metals. Metals are naturally excellent reflectors of light. That’s why they appear to have a shiny luster. Turning them black can therefore make them very efficient at absorbing light. The combination of light-absorbing properties with making metals water repellent could lead to more efficient solar absorbers – solar absorbers that don’t rust and do not need much cleaning.

Guo’s team had previously blasted materials with the lasers and turned them hydrophilic, meaning they attract water. In fact, the materials were so hydrophilic that putting them in contact with a drop of water made water run “uphill” (http://www.rochester.edu/news/show.php?id=3387).

Help us caption & translate this video!

http://amara.org/v/GA08/

Using Lasers to Create Super-hydrophobic Materials

Researchers at the University of Rochester have measured for the first time light emitted by photoluminescence from a nanodiamond levitating in free space. In a paper published this week in Optics Letters, they describe how they used a laser to trap nanodiamonds in space, and -- using another laser -- caused the diamonds to emit light at given frequencies.

The experiment, led by Nick Vamivakas, an assistant professor of optics, demonstrates that it is possible to levitate diamonds as small as 100 nanometers (approximately one-thousandth the diameter of a human hair) in free space, by using a technique known as laser trapping. 

"Now that we have shown we can levitate nanodiamonds and measure photoluminescence from defects inside the diamonds, we can start considering systems that could have applications in the field of quantum information and computing," said Vamivakas. He said an example of such a system would be an optomechanical resonator.

Vamivakas explained that optomechanical resonators are structures in which the vibrations of the system, in this case the trapped nanodiamond, can be controlled by light. "We are yet to explore this, but in theory we could encode information in the vibrations of the diamonds and extract it using the light they emit."

Possible avenues of interest in the long-term with these nano-optomechanical resonators include the creation of what are known as Schrödinger Cat states (macroscopic, or large-scale, systems that are in two quantum states at once). These resonators could also be used as extremely sensitive sensors of forces -- for example, to measure tiny displacements in the positions of metal plates or mirrors in configurations used in microchips and understand friction better on the nanoscale. 

"Levitating particles such as these could have advantages over other optomechanical oscillators that exist, as they are not attached to any large structures," Vamivakas explained. "This would mean they are easier to keep cool and it is expected that fragile quantum coherence, essential for these systems to work, will last sufficiently long for experiments to be performed." 

The future experiments that Vamivakas and his team are planning build on previous work by Lukas Novotny, a co-author of the paper formerly at Rochester and now at ETH in Zurich, Switzerland, and Romain Quidant, also a co-author from ICFO, Spain. Novotny, Quidant and their teams showed previously that by tweaking the trapping laser's properties, a particle can be pushed towards its quantum ground state. By linking the laser cooling of the crystal resonator with the spin of the internal defect it should be possible to monitor the changes in spin configuration of the internal defect -- these changes are called Bohr spin quantum jumps -- via the mechanical resonator's vibrations. Vamivakas explained that experiments like this would expand what we know about the classical-quantum boundary and address fundamental physics questions.

The light emitted by the nanodiamonds is due to photoluminescence. The defects inside the nanodiamonds absorb photons from the second laser -- not the one that is trapping the diamonds -- which excites the system and changes the spin. The system then relaxes and other photons are emitted. This process is also known as optical pumping. 

The defects come about because of nitrogen vacancies, which occur when one or more of the carbon atoms in diamond is replaced by a nitrogen atom. The chemical structure is such that at the nitrogen site it is possible to excite electrons, using a laser, between different available energy levels. Previous experiments have shown that these nitrogen vacancy centers in diamonds are good, stable sources of single photons, which is why the researchers were keen to levitate these particles.

Using lasers to trap ions, atoms and more recently larger particles is a well-established field of physics. Nanodiamonds, however, had never been levitated. To position these 100 nanometers diamonds in the correct spot an aerosol containing dissolved nanodiamonds sprays into a chamber about 10 inches in diameter, where the laser's focus point is located. The diamonds are attracted to this focus point and when they drift into this spot they are trapped by the laser. Graduate student Levi Neukirch explains that sometimes "it takes a couple of squirts and in a few minutes we have a trapped nanodiamond; other times I can be here for half an hour before any diamond gets caught. Once a diamond wanders into the trap we can hold it for hours."

The Rochester researchers collaborated on this paper with Lukas Novotny, formerly at the University of Rochester and now at ETH Zurich, Switzerland, and with Jan Gieseler and Romain Quidant, at the Institut de Ciencies Fotoniques in Barcelona, Spain.

Optically Levitated, Glowing Diamonds for Nanoscale Research

Researchers at the University of Rochester have found that a simple visual task can predict IQ. In the study, individuals watched video clips of black and white bars moving across a computer screen, very similar to the clips seen in this video. Their sole task was to identify which direction the bars drifted: to the right or to the left. 

The images were presented in different sizes and the researchers measured how much time participants needed to be able to perceive the direction of the motion. Because the brain filters out background movement, it's actually harder for most people to see movement in the larger images. 

The study found that people with higher IQs were actually the worst at seeing movement in the large images, or, in other words, the best at filtering out distracting sensory signals. How people performed on this simple task turns out to be a very good predictor of their performance on a standardized intelligence test.

To read more about the findings of the research, visit: http://www.sciencedirect.com/science/article/pii/S0960982213004946

Music: Beethoven Piano Sonata 25, Opus 79 1st movement

For more information on this, read the story on the University of Rochester Newscenter: http://rochester.edu/news/show.php?id=6422
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Testing Your "Motion Quotient"

A team of geologists at the University of Rochester has discovered a new species of bird in the Canadian Arctic. At approximately 90 million years old, the bird fossils are among the oldest avian records found in the northernmost latitude, and offer further evidence of an intense warming event during the late Cretaceous period.

“The bird would have been a cross between a large seagull and a diving bird like a cormorant, but likely had teeth,” says John Tarduno, professor and chair of the Department of Earth and Environmental Sciences at the University and leader of the expedition.  

Tarduno and his team, which included both undergraduate and graduate students, named the bird Tingmiatornis arctica; “Tingmiat” means “those that fly” in the Inuktitut language spoken in the central and eastern Canadian Arctic (Nunavut territory).

Their findings, published in Scientific Reports, add to previous fossil records Tarduno uncovered from the same geological time period and location in previous expeditions (LINK TO: http://www.rochester.edu/news/show.php?id=3311, http://www.rochester.edu/pr/releases/ear/champ.htm). Taken together, these fossils paint a clearer picture of an ecosystem that would have existed in the Canadian Arctic during the Cretaceous period’s Turonian age, which lasted from approximately 93.9 to 89.8 million years ago. 

“These fossils allow us to flesh out the community and add to our understanding of the community’s composition and how it differed from other places in the world,” says Donald Brinkman, vertebrate paleontologist and director of preservation and research at the Royal Tyrrell Museum in Alberta, Canada.

Building historic climate records further helps scientists determine the effects of climate on various communities, ecosystems, and the distribution of species and could help predict the effects of future climatic events.

“Before our fossil, people were suggesting that it was warm, but you still would have had seasonal ice,” Tarduno says. “We’re suggesting that’s not even the case, and that it’s one of these hyper-warm intervals because the bird’s food sources and the whole part of the ecosystem could not have survived in ice.” 

From the fossil and sediment records, Tarduno and his team were able to conjecture that the bird’s environment in the Canadian Arctic during the Turonian age would have been characterized by volcanic activity, a calm freshwater bay, temperatures comparable to those in northern Florida today, and creatures such as turtles, large freshwater fish, and champsosaurs—now-extinct, crocodile-like reptiles. 

“The fossils tell us what that world could look like, a world without ice at the arctic,” says Richard Bono, a PhD candidate in earth and environmental sciences at the University and a member of Tarduno’s expedition. “It would have looked very different than today where you have tundra and fewer animals.”

The Tingmiatornis arctica fossils were found above basalt lava fields, created from a series of volcanic eruptions. Scientists believe volcanoes pumped carbon dioxide into the Earth’s atmosphere, causing a greenhouse effect and a period of extraordinary polar heat. This created an ecosystem allowing large birds, including Tingmiatornis arctica, to thrive.

Tarduno’s team unearthed three bird bones: part of the ulna and portions of the humerus, which, in birds, are located in the wings. From the bone features, as well as its thickness and proportions, the team’s paleontologist, Julia Clarke of the University of Texas, was able to determine the evolutionary relationships of the new birds as well as characteristics that indicate whether it likely was able to fly or dive. 

“These birds are comparatively close cousins of all living birds and they comprise some of the oldest records of fossil birds from North America,” Clarke says. “Details of the upper arm bones tell us about how features of the flightstroke seen in living species came to be.”

Previous fossil discoveries indicate the presence of carnivorous fish such as the 0.3-0.6 meter-long bowfin. Birds feeding on these fish would need to be larger-sized and have teeth, offering additional clues to Tingmiatornis arctica’s characteristics.

Physiological factors, such as a rapid growth and maturation rate, might explain how this line of bird was able to survive the Cretaceous-Paleogene mass extinction event that occurred approximately 66 million years ago and eliminated approximately three-quarters of the plant and animal species on Earth.  

These physiological characteristics are still conjecture, Tarduno emphasizes, but he says the bird’s environment gives clear indications as to why the bird fossils were found in this location.

“It’s there because everything is right,” Tarduno says. “The food supply was there, there was a freshwater environment, and the climate became so warm that all of the background ecological factors were established to make it a great place.”

New Arctic Bird Species Discovered from 90 Million Year Old Fossils

The Earth’s magnetic field plays a key role in making the planet habitable. It shields lifeforms from harmful solar and cosmic radiation. It helps limit erosion of the atmosphere and keeps water from escaping into space.

 But new data show a prolonged near collapse of Earth’s magnetic field that took place some 575-565 million years ago coincided with the blossoming of macroscopic complex animal life.

We now face the possibility of a new, unexpected twist in how life might relate to the magnetic field, says John A. Tarduno, the William R. Kenan Professor of Geophysics and the dean of research at the School of Arts and Sciences and the Hajim School of Engineering and Applied Sciences at the University of Rochester.

 
“That twist could reach deep into Earth’s inner core,” says Tarduno, who recently wrote about the findings for Physics Today magazine. Tarduno is frequently cited by news outlets, like CNN, The Washington Post, and Smithsonian magazine, on matters related to the Earth’s inner core, or dynamo, and magnetic field. He can be reached at john.tarduno@rochester.edu. 

The Earth’s magnetic field protects life, but an ancient phase when it nearly collapsed coincided with a key step in evolution, says University of Rochester geophysicist John A. Tarduno.

Weird and complex life emerged on Earth as the planet's magnetic field gave way

The Earth’s magnetic field protects life, but an ancient phase when it nearly collapsed coincided with a key step in evolution, says University of Rochester geophysicist John A. Tarduno.