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Scientists Watch Bacterial Sensor Respond to Light

A number of important biological processes, such as photosynthesis and vision, depend on light. But it’s hard to capture responses of biomolecules to light because they happen almost instantaneously. Now, researchers have made a giant leap forward in taking snapshots of these ultrafast reactions in a bacterial light sensor. Using the world’s most powerful X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory, they were able to see atomic motions as fast as 100 quadrillionths of a second – 1,000 times faster than ever before. “We’re the first to succeed in taking real-time snapshots of an ultrafast structure transition in a protein, in which a molecule excited by light relaxes by rearranging its structure in what is known as trans-to-cis isomerization,” says the study’s principal investigator, Marius Schmidt from the University of Wisconsin, Milwaukee. The technique could benefit studies of light-driven, ultrafast atomic motions. For example, it could reveal: How visual pigments in the human eye respond to light, and how absorbing too much of it damages them. How photosynthetic organisms turn light into chemical energy – a process that could serve as a model for the development of new energy technologies. How atomic structures respond to light pulses of different shape and duration – an important first step toward controlling chemical reactions with light. “The new data show for the first time how the bacterial sensor reacts immediately after it absorbs light,” says Andy Aquila, a researcher at SLAC’s Linac Coherent Light Source, a DOE Office of Science User Facility. “The initial response, which is almost instantaneous, is absolutely crucial because it creates a ripple effect in the protein, setting the stage for its biological function. Only LCLS’s X-ray pulses are bright enough and short enough to capture biological processes on this ultrafast timescale.”

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Researchers Develop Thin, Flexible Sheet Camera

A team led by Shree K. Nayar, T.C. Chang Professor of Computer Science at Columbia Engineering, has developed a novel sheet camera that can be wrapped around everyday objects to capture images that cannot be taken with one or more conventional cameras. The team designed and fabricated a flexible lens array that adapts its optical properties when the sheet camera is bent. This optical adaptation enables the sheet camera to produce high-quality images over a wide range of sheet deformations. "Cameras today capture the world from essentially a single point in space," says Nayar. "While the camera industry has made remarkable progress in shrinking the camera to a tiny device with ever increasing imaging quality, we are exploring a radically different approach to imaging. We believe there are numerous applications for cameras that are large in format but very thin and highly flexible." If such an imaging system could be manufactured cheaply, like a roll of plastic or fabric, it could be wrapped around all kinds of things, from street poles to furniture, cars, and even people's clothing, to capture wide, seamless images with unusual fields of view. This design could also lead to cameras the size of a credit card that a photographer could simply flex to control its field of view. The new "flex-cam" requires two technologies: a flexible detector array and a thin optical system that can project a high-quality image on the array. One approach would be to attach a rigid lens with fixed focal length to each detector on the flexible array. In this case, however, bending the camera would result in "gaps" between the fields of views of adjacent lenses. This would cause the captured image to have missing information or appear "aliased." To solve this problem, the Columbia Engineering team developed an adaptive lens array made of elastic material that enables the focal length of each lens in the sheet camera to vary with the local curvature of the sheet in a way that mitigates aliasing in the captured images. This inherent optical adaptation of the lens is passive, avoiding the use of complex mechanical or electrical mechanisms to independently control each lens of the array.

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Astronomers Use Imaging Software to See Peanut Shell Galaxy

Astronomers at Swinburne University of Technology, Melbourne, have discovered an unusually shaped structure in two nearby disc galaxies. The Swinburne team recently developed new imaging software, making it possible to observe the double "peanut shell shape" formed by the distribution of stars bulging from the centers of these galaxies. The results are published in a new paper in Monthly Notices of the Royal Astronomical Society. Using data from the Hubble Space Telescope and the Sloan Digital Sky Survey, the researchers realized that two of the galaxies they were studying (NGC 128 and NGC 2549) were quite exceptional. They are roughly 200 and 60 million light years away respectively, in the constellations of Pisces and Lynx, and they displayed a peanut shell configuration at two separate layers within the galaxies' three-dimensional distribution of stars. "Ironically, these peanut-shaped structures are far from peanut-sized," says Swinburne's Professor Alister Graham, co-author of the research. "They consist of billions of stars typically spanning up to a quarter of the length of the galaxies." Although the “bulges” of both galaxies were already known to display a single peanut shell pattern, astronomers had never before observed the fainter second structure in any galaxy. "They resemble two peanut shells, with one neatly nested within the other; this is the first time such a phenomenon has been observed," says Bogdan Ciambur, the Ph.D. student who led the investigation. "We expect the galaxies' surprising anatomy will provide us with a unique view into their pasts. Deciphering their history can tell us about transformations that galaxies like our own Milky Way might experience."

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Infection alert in catheters could tackle hospital superbugs

A new infection alert system in catheters could prevent serious infections in millions of hospital patients worldwide. The system, detailed in a new paper in “Biosensors and Bioelectronics,” changes the color of the urine so patients and healthcare providers can see easily if bacteria are starting to block the catheter. Designed by Dr. Toby Jenkins and his colleagues at the University of Bath, the new catheter infection alert system provides a means of early detection, so the catheter can be changed and the infection treated before a person becomes unwell. “Catheter-related infections are a serious problem, especially if the bacteria are resistant to antibiotics,” said Jenkins. “We hope that with this simple-to-use sensor system we can ultimately make a real difference to patients' lives.” Over time bacteria can build a layer called a biofilm inside the catheter tubes that eventually blocks them. The urine can't escape and pushes back into the kidneys where the bacteria can cause kidney failure, body-wide infection and death. Up to half of people who use catheters long-term have problems with blockages caused by bacteria, but there is currently no way to detect potential blockages before they cause problems. The new coating detects biofilms built by a bacterium called Proteus mirabilis, the most common cause of catheter blockage. The system gives advanced warning of a catheter blockage 10 to 12 hours before it happens. The coating is made up of two layers. The first reacts to changes in urine caused by the bacteria; the second layer releases the dye. The dyed urine gathers in the collection bag, turning the urine bright yellow. The color change reveals the infection. Biofilms built by bacteria are not easy to treat. They avoid the natural defenses of the immune system and can't be broken down by antibiotics. Jenkins is optimistic about the benefits of the system: "Our new coating works with existing catheter designs and gives a clear, early visual warning of infection before a catheter is blocked. It could dramatically reduce the number of infections resulting from bacterial blockages."

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New device prevents damage while securing tubes

The U.S. Army Institute of Surgical Research has developed a novel device for securing medical tubes and catheters intubated within a patient that will prevent damage to the incisors as well as to the soft tissue around the corners of the mouth.  Burn patients often have problems breathing on their own due to scorched esophagi, damaged airways due to smoke inhalation, or organ failures. Therefore, it becomes necessary to intubate the patient so that they can breathe. Patients have lost their incisors due to prolonged forceful clamping of the jaw on the semi-rigid bite block. This new device moves the bite blocks (one for each side) from the front teeth to the molars, to capitalize on the greater strength of these teeth to prevent tooth damage. Positioning the bite blocks at the molars also prevents the incisor teeth from biting and occluding the endotracheal or nasogastric tubes. In addition to the potential loss of teeth, the current method of securing endotracheal tubes often leaves patients with cuts or tears in and around their mouths. This device prevents damage by attaching the bite blocks to a framework that protrudes from the patient’s mouth and that provides attachment sites for straps to secure the device to the patient, and a track-and-clamp system to secure the endotracheal or nasogastric tubes. The attachment sites are an improvement in capability over the current state of the art, in which the tubes are taped to the bite block and the combined structure is then taped to the patient.  The Army is seeking a partner interested in commercializing this technology.

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New research uses graphene oxide to fight bacteria

Scientists at the Università Cattolica del Sacro Cuore in Rome are studying graphene oxide in the hopes of creating bacteria-killing catheters and medical devices. Coating surgical tools with this carbon-based compound could kill bacteria, reducing the need for antibiotics, decreasing the rates of post-operative infections, and speeding recovery times. "We want to make materials that will help patients and medical professionals," said Valentina Palmieri, a biotechnologist at the Università Cattolica del Sacro Cuore. Graphene oxide, a form of graphene with molecular oxygen incorporated into it, protects against infection by destroying bacteria before it gets inside the body. The graphene oxide wraps around the bacteria, puncturing its membrane. A broken membrane prevents the bacteria from growing and often kills it. "The bacteria lose their complex structure and die," Palmieri added. "And since graphene is just carbon (a building block of life) its cytotoxicity against human cells is much lower compared to any drug-based antimicrobial therapy."  Researchers decided to use graphene oxide because it is very stable in a water solution, making it safe to interact with human cells. Graphene specifically attacks bacterial cells, while sparing human cells, and the mechanism behind this specificity is still unclear, Palmieri said. Current theories include that the material interacts more favorably with the bacterial cell wall or that mammalian cells have evolved multiple repair mechanisms to survive the chemical oxidation damage that graphene induces.  Graphene is also more eco-friendly. Traditional methods of preventing infection include antibiotic therapy and tools coated with silver, both of which are toxic to the environment, Palmieri said.

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Wartime medical device is saving lives at home

A patient at the University of California Davis Medical Center was losing blood from multiple gunshot wounds, and doctors feared he was not going to survive long enough for them to operate. The newly approved REBOA catheter was used to restore blood flow to his critical organs so they could save his life.  "Air Force research conducted at the CIF directly contributed to saving the life of this 28-year-old father of six," said Air Force Maj. Timothy Williams, 60th SGCS vascular surgeon. "I have done trauma surgery all of my professional life, including work at three civilian level I trauma centers and three deployments. I can, without reservation, state that REBOA saved his life." The CIF is the Clinical Investigation Facility located at David Grant USAF Medical Center, one of seven Air Force medical facilities with formal clinical investigation programs and resources.  Approved by the FDA in January, the REBOA (resuscitative endovascular balloon occlusion of the aorta) catheter was developed by researchers to slow bleeding, without damaging vital organs, so a patient can receive life-saving care. This device is inserted into a hemorrhaging vessel and stops or slows the blood flow to that injury while allowing blood flow to continue to vital organs and other body parts.   The idea originated at the 59th Medical Wing at Lackland Air Force Base in Texas, the main hub for autopsies performed on combat casualties. Air Force Maj. Lucas Neff, 60th SGCS vascular surgeon, explained: "The autopsies showed that the No. 1 cause of potentially survivable deaths by service members is noncompressible hemorrhaging in the chest and core. We have worked on techniques (with the REBOA) that allow us to control the amount of blood flow that can pass while using the catheter. It's like a faucet, where you can turn the flow down in areas where there is bleeding without turning it completely off, allowing blood to flow to other important areas."  Williams and Neff were deployed together to Afghanistan in 2014. "I don't know if I would've gone down this road of research if it wasn't for that deployment," Williams said. "Having actually been there and seen the casualties firsthand brought me to this research."

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