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Single-pixel digital cameras and new images showing how the brain recovers from stroke were among the highlights at Frontiers in Optics 2006–the 90th Annual Meeting of the Optical Society of America (OSA)–held October 8-12 in Rochester, New York. Co-located with Laser Science XXII, the annual conference of the APS Division of Laser Science, the meeting also celebrated 90 years of innovations in optics.
In a plenary and awards presentation, Nobel Laureate Steven Chu, the director of Lawrence Livermore National Laboratory, provided a scientist's perspective on the global energy problem, with emphasis on climate change, then outlined our current options and some areas of energy research that may lead to society-transforming technologies.
Lee Goldstein of Harvard Medical School described evidence that optical tests can detect the signs of Alzheimer's disease in the eye even before symptoms appear in the brain.
Single-Pixel Digital Cameras. A single-pixel camera, scientists at Rice University believe, could eventually lead to a consumer product that requires less power consumption and storage space without sacrificing image detail. The new approach aims to confront one of the basic dilemmas of digital imaging, namely the huge waste of data in going from a million numbers (the light levels from a picture taken with a megapixel camera) to something like 10,000 numbers, corresponding to the result of a data-reduction transformation that takes place right on the chip inside the camera.
The Rice camera gets rid of the million pixels and views the scene with a single pixel. Instead of looking once at the object using a million pixels, it looks 10,000 times using one pixel. In each of those viewings, however, the light from the object reflects off the myriad surfaces of a digital micromirror device, the same technology used in projection TVs and digital movie projectors.
On the left a close-up view of spine vessel relationship in mouse brain in vivo. On the right, projection image showing Texas-Red labeled vasculature and green labeled dendrites taken from a transgenic mouse before induction of ischemia in vivo. Note the cerebral vessels coursing through the dendritic arbors.
How the Brain Recovers from Stroke. New study results provide encouraging new information on how the brain can recover after severe strokes if treated early. It is the first published experiment monitoring blood flow and individual brain cells at the same time. Tim Murphy of the University of British Columbia said the result suggests that rapid treatment could offer new hope to human stroke patients.
Murphy and his colleagues watched how the disruption of blood flow affects the structure of microscopic nerve cells (neurons) in the brains of live mice. The researchers studied special mice with brain neurons that contain the YFP protein, which lights up in response to laser light. In addition, the researchers introduced a fluorescent polymer that fails to enter blood cells but gets absorbed by plasma, the liquid portion of blood. When irradiated, the plasma glows and blood cells show up as dark structures on a bright background. This enables the team to look simultaneously at blood flow as well as important nerve-cell structures that can be damaged during a stroke.
Murphy’s team found that if blood flow is restored within 10 to 60 minutes following even severe stroke conditions, the dendrite and spine structure is mostly restored, demonstrating that the brain's ability to recover from a stroke may be even more remarkable than previously thought. Preliminary measurements suggest that the nerve cells with recovered structure restore their function as well, according to the researchers.
Fiber Optic Stealth Transmissions. Bernard Wu and Evgenii Narimanov of Princeton University presented a method for transmitting secret messages over existing public fiber-optic networks. This technique could immediately allow inexpensive, widespread, and secure transmission of confidential and sensitive data by governments and businesses.
Wu and Narimanov’s technique is not the usual form of encryption, in which computer software scrambles a message. Instead, this is a more hardware-oriented form of encryption–it uses the real-world properties of an optical-fiber network to cloak a message. The sender transmits an optical signal that is so faint that it is very hard to detect, let alone decode. The method takes advantage of the fact that real-world fiber optics systems inevitably have low levels of “noise,” random jitters in the light waves that transmit information through the network. The new technique hides the secret message in this optical noise.
Shape-Shifting Blood Cells. Responding to various chemical and temperature changes, living cells change their shape and their volume. The outer layers (membranes) of red blood cells, for example, can change by tens of nanometers on time scales of tens of milliseconds. Now an MIT group has figured out a way of studying such tiny, quick fluctuations, and how they are related to the cell’s osmotic behavior–that is, to the cell’s ongoing effort to maintain a balance in the concentration of ions between itself and its surroundings. It can do this, for instance, by admitting or expelling water. If the osmotic imbalance becomes too great, however, the cells can burst, an action called lysis. Diseased cells are more prone to lysis.
Gabriel Popescu, a researcher in the MIT laser spectroscopy lab of Michael Feld, says that their optical microscopy measurements of the role of osmotic pressure in red blood cell flickering are likely to help in understanding clinical problems such as the effects of the malaria virus on the red blood cell membrane and changes in the mechanical properties of the cells during sickle cell disease.
New Eye Instrumentation. Employing methods from astronomy and physics, researchers presented advances in eye instrumentation that promise to detect eye diseases much earlier. Ann Elsner and Benno Petrig of Indiana University presented a new tool for detecting eye diseases resulting from diabetic retinopathy, a class of retina-related eye diseases that affects 45 percent of those with diabetes and includes diabetes-related cataracts and glaucoma.
Other research groups are using a technique borrowed from astronomy, called adaptive optics (AO), which uses a special mirror whose surface can be deformed to help a telescope remove the effect of atmospheric distortion to obtain clearer images of far-away objects. Over the last five years, researchers have introduced laser-based ophthalmoscopes that use AO technology.
Yuhua Zhang of the University of California, Berkeley presented a new-generation AO scanning laser ophthalmoscope (AOSLO) that uses a micro-electro-mechanical deformable mirror. This miniature, flexible mirror could potentially be mass-produced, thus offering the prospect of a smaller, more cost-effective AO system.
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