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September 24, 2014

In Research

Researchers send electricity, light along same super-thin wire

graphic showing hoops along wire on a grid
Rochester researchers report that they have designed a basic model circuit in which photons propogate along a silver nanowire using electromagnetic waves called plasmons.
Illustration by Michael Osadciw

Scientists at the University and at Swiss Federal Institute of Technology in Zurich reported earlier this month in the Optical Society’s journal Optica a new combination of materials that can efficiently guide electricity and light along the same tiny wire. The finding could be a step toward building computer chips capable of transporting digital information at the speed of light. The coauthors of the paper describe a basic-model circuit consisting of a silver nanowire and a single-layer flake of molybdenum disulfide (MoS2). Using a laser to excite electromagnetic waves called plasmons at the surface of the wire, the researchers found that the MoS2 flake at the far end of the wire generated strong light emission. Going in the other direction, as the excited electrons relaxed, they were collected by the wire and converted back into plasmons, which emitted light of the same wavelength. Typically about a third of the remaining energy would be lost for every few microns (millionths of a meter) the plasmons traveled along the wire. While devices can be much faster than electronic ones, they are bulkier because devices that focus light cannot be miniaturized nearly as well as electronic circuits. The new results hold promise for guiding the transmission of light, and maintaining the intensity of the signal, in very small dimensions.

Researchers identify rare neuromuscular disease

An international team of researchers, including David Herrmann, professor of neurology, has identified an inherited neuromuscular disorder.

The rare condition is the result of a genetic mutation that interferes with the communication between nerves and muscles, causing impaired muscle control. The focus of the research is the neuromuscular junction, the point at which the axon fibers that extend from peripheral nerves meet the muscle cells. The chemical signals that pass across the junction are essential for motor function.

There are a number of disorders— both acquired and inherited—that interfere with the communication that occurs at the neuromuscular junction, resulting in muscle weakness and fatigue, primarily in the limbs.

While the families in the study had at one point been diagnosed with other neuromuscular conditions, the researchers identified them as unique, due to their particular motor abnormalities, including problems resembling Lambert-Eaton, and because the disease was passed from one generation to the next.

The researchers compiled a genetic profile of affected family members and found that the two different families had mutations in the code that creates the protein synaptotagmin 2 (SYT2). The authors have used the mutation in SYT2 to create a fruit fly (drosophila) model of the disease and see this as a first step to the development of potential new therapies to treat the condition.

Look at the face, see a person’s heart

With the assistance of a web camera and software algorithms, the face can reveal whether or not an individual is experiencing atrial fibrillation, a treatable but potentially dangerous heart condition.

A pilot project, the results of which were published online in August in the journal Heart Rhythm, demonstrates that subtle changes in skin color can be used to detect the uneven blood flow caused by atrial fibrillation. The technology was developed in a partnership between the School of Medicine and Dentistry and Xerox.

Atrial fibrillation is an irregular or sometimes rapid heart rate that commonly causes poor blood flow to the body. This occurs when erratic cardiac electrical activity causes the upper and lower chambers of the heart to beat out of sync. More than three million Americans suffer from the disease.

While the condition—which affects more than 3 million Americans— can be readily diagnosed, in many people it goes undetected, either because it comes and goes, or because the symptoms, fatigue and weakness, are too general to warrant concern. Consequently, it is estimated that 30 percent of people with atrial fibrillation do not know they have the condition. If untreated, the condition places individuals at a significantly higher risk for blood clots and stroke.

The technology described in the study employs a software algorithm developed by Xerox that in 15 seconds scans the face and can detect changes in skin color that are imperceptible to the naked eye. All this requires is that the subject remain still for 15 seconds.

The researchers found that the color changes detected by video monitoring corresponded with an individual’s heart rate as detected on an ECG. The video monitoring technique—which researchers have dubbed videoplethymography— had an error rate of 20 percent, comparable to the 17 to 29 percent error rate associated with automated ECG measurements. What’s more, the contactless nature of the technology and the proliferation of web cameras could eventually allow the screening to occur without interrupting the user, with the program running while someone is reading their email on their tablet, computer, or smart phone.

Doing more with less in quantum physics

Robert Boyd, professor of optics and of physics, along with graduate students Mohammad Mirhosseini, Omar Magana-Loaiza, and Seyed Mohammad Hashemi Rafsanjani, have developed a new way of determining quantum wave functions. Called compressive direct measurement, it allows the team to reconstruct a quantum state using only a quarter of the measurements required by previous methods.

While recent compressive sensing techniques have been used to measure sets of complementary variables like position and momentum, Mirhosseini explains that their method allows them to measure the full wave function. Compression is widely used in the classical world of digital media, including recorded music, video, and pictures. The MP3s on your phone, for example, are audio files that have had bits of information squeezed out to make the file smaller at the cost of losing a small amount of audio quality along the way.

In digital cameras, the more pixels you can gather from a scene, the higher the image quality and the larger the file will be. But it turns out that most of those pixels don’t convey essential information that needs to be captured from the scene. Most of them can be reconstructed later.

Compressive sensing works by randomly sampling portions from all over the scene, and using those patterns to fill in the missing information. Similarly for quantum states, it is not necessary to measure every single dimension of a multidimensional state. It takes only a handful of measurements to get a high-quality image of a quantum system.

The method introduced by Mirhosseini and the team has important potential applications, including secure communication, teleportation of quantum states, and ideally to perform quantum computation. This latter process holds great promise as a method that can, in principle, lead to a drastic speed-up of certain types of computation.

Group Looks at Stem Cell Potential, Challenges

In an article appearing online last month in the journal Science, a group of researchers, including Rochester neurologist Steve Goldman, review both the potential and challenges facing the scientific community as therapies involving stem cells move closer to reality.

The review article focuses on pluripotent stem cells (PSCs), which are stem cells that can give rise to all cell types. These include both embryonic stem cells, and those derived from mature cells that have been “reprogrammed” or “induced”—a process typically involving a patient’s own skin cells—so that they possess the characteristics of stem cells found at the earliest stage of development. These cells can then be differentiated, through careful manipulation of chemical and genetic signaling, to become virtually any cell type found in the body. While the process of making induced PSCs is just seven years old, one of the reasons that these cells are viewed with promise by the scientific community is because they are derived from the patient’s own tissue.

Consequently, cells used for transplant can be a genetic match and far less likely to be rejected, thereby potentially mitigating the need to use immune system suppressing drugs. However, while progress has been made, the authors concede significant challenges remain. Scientists must be able to obtain the precise cell populations required to treat the target disease, and once transplanted, make sure that these cells get to where they are needed and integrate into existing tissue. The cells that are transplanted must also first be checked for purity and screened for unwanted cells that could give rise to tumors.

Work supports alternate mechanism of speciation

two ants
A queen ant of the parasitic species Mycocepurus castrator (l) and a queen ant of the host species Mycocepurus goeldii queen (r).

A newly discovered species of ant supports a controversial theory of species formation, according to work by a Rochester team. The findings were published Thursday in the journal Current Biology.

“Most new species come about in geographic isolation,” said Christian Rabeling, assistant professor of biology. “We now have evidence that speciation can take place within a single colony.”

In discovering the parasitic Mycocepurus castrator, researchers uncovered an example of a still-controversial theory known as sympatric speciation, which occurs when a new species develops while sharing the same geographic area with its parent species, yet reproducing on its own. New species are formed when its members are no longer able to reproduce with members of the parent species. The commonly-accepted mechanism is called allopatric speciation, in which geographic barriers— such as mountains—separate members of a group, causing them to evolve independently.

“Since Darwin’s Origin of Species, evolutionary biologists have long debated whether two species can evolve from a common ancestor without being geographically isolated from each other,” said Ted Schultz, curator of ants at the Smithsonian’s National Museum of Natural History and co-author of the study. “With this study, we offer a compelling case for sympatric evolution that will open new conversations in the debate about speciation in these ants, social insects and evolutionary biology more generally.”

Baby aspirin? Most doctors don’t recommend, despite guidelines

A majority of middle-aged men and women eligible to take aspirin to prevent heart attack and stroke do not recall their doctors ever telling them to do so, according to a University study of more than 3,000 patients nationally.

Published online by the Journal of General Internal Medicine, the finding illustrates a common disconnect between public health guidelines and what occurs in clinical practice. Led by Kevin Fiscella, professor of family medicine, and John Bisognano, director of outpatient cardiology services at UR Medicine, the Rochester study is consistent with other research showing that physicians often do not recommend aspirin as prevention therapy to the general population, despite established guidelines by the U.S. Preventative Services Task Force. Among the reasons cited by phyisicans: too little time with patients to assess their eligibility for aspirin treatment, and the potential for harm to the digestive-tract bleeding.

“Patients often view changes as an illustration that folks in the medical field can’t really make up their minds,” said Bisognano, professor of medicine. “Changes can undermine a practitioner’s or patient’s enthusiasm to immediately endorse new guidelines because they wonder if it will change again in three years.”

The study notes that using expanded primary care teams of nurses, medical assistants, and health educators may help to reduce the volume of decisions that rest solely with physicians at office visits. Sharing care can improve agreement between published guidelines, the use of risk models, and actual practice, the study notes.

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