Princeton scientists have developed a new more energy efficient way to generate laser light. The finding should allow for building of miniature diagnostic devices that monitor light’s attenuation in a liquid sample, potentially leading to specialized blood glucose meters and other similar devices.

The laser used in the Princeton study is a special type called a quantum cascade laser. Built at Princeton University’s nanofabrication facility, the device is about one-tenth as thick as a human hair and 3 millimeters long. Despite its tiny size, it is made of hundreds of layers of different semiconductor materials. Each layer is only a few atoms thick. In this device, electrons “cascade” down through the layers as they lose energy and give off synchronized photons.
In an earlier study published in Applied Physics Letters in June 2007, Franz [graduate student Kale Franz], Gmachl [Claire Gmachl, an electrical engineer and director of the Mid-Infrared Technologies for Health and the Environment (MIRTHE) center --ed.] and others had reported that a quantum cascade laser they had built unexpectedly emitted a second laser beam of slightly smaller wavelength than the main one. Further studies by Menzel and others revealed that the second beam could not be explained by any existing theory of quantum cascade lasers. Unlike a conventional semiconductor laser, the second beam grew stronger as the temperature increased, up to a point. Further, it seemed to compete with the “normal” laser, growing weaker as the latter strengthened when more electric current was supplied. “It’s a new mechanism of light emission from semiconductor lasers,” said Franz.
To explain this mechanism, the researchers invoked a quantum property of electrons called momentum. In the conventional view of quantum cascade lasers, only electrons of nearly zero momentum participate in “lasing” (producing laser light). Further, a substantial number of electrons has to attain the same level of energy and momentum – be in a so-called “quasi-equilibrium” condition — before they can participate in laser action. In contrast, studies by Gmachl’s group showed that the second laser beam originated from electrons of lower energy, but higher momentum that were not in equilibrium. “It showed, contrary to what was believed, that electrons are useful for laser emission even when they are in highly non-equilibrium states,” said Franz.
The new laser phenomenon has some interesting features. For instance, in a conventional laser relying on low momentum electrons, electrons often reabsorb the emitted photons, and this reduces overall efficiency. In the new type of laser, however, this absorption is reduced by 90%, said Franz. This could potentially allow the device to run at lower currents, and also makes it less vulnerable to temperature changes. “It should let us dramatically improve laser performance,” he said.
The device used in the study does not fully attain this level of performance, because the conventional, low-efficiency laser mechanism dominates. To take full advantage of the new discovery, therefore, the conventional mechanism would need to be turned off. The researchers have started to work on methods to achieve this outcome, said Franz.
Unlike other lasers, quantum cascade lasers operate in the mid- and far-infrared range, and can be used to detect even minute traces of water vapor, ammonia, nitrogen oxides, and other gases that absorb infrared light. As a result, these devices are finding applications in air quality monitoring, medical diagnostics, homeland security, and other areas that require extremely sensitive detection of different chemicals.

Press release: Princeton researchers discover new type of laser…

Who would have thought there would be a reason to make sugar-free antibodies? Well, researches at MIT did! It has long been thought that a particular sugar attachment was required for antibody function but new research shows this to not be the case. This opens the door to mass producing therapeutic antibodies by bacteria or fungi.

MIT engineers have found that antibodies do not need a particular sugar attachment long believed to be essential to their function, a discovery that could make producing therapeutic antibodies much easier and cheaper in the future.
Therapeutic antibodies are a promising new type of treatment for cancer and other diseases, but their practicality has been limited by the fact that only mammalian cells have the right machinery to build the sugar attachment.
“To date, people have faced limitations in how they were going to make these antibodies because they appeared to require these (sugar) structures,” said Dane Wittrup, the C.P. Dubbs Professor of Chemical Engineering, Biological Engineering, member of the Koch Institute for Integrative Cancer Research, and senior author of a paper on the work that appeared in the Dec. 12 online edition of the Proceedings of the National Academy of Sciences.
Wittrup and biological engineering graduate student Stephen Sazinsky, co-lead author of the paper, found that antibodies don’t need the sugar normally found attached to a certain region of antibody when the sequence is slightly mutated.
Antibodies are a key part of the immune system, roaming around the body to detect invaders such as bacteria and viruses. Each antibody is specific to a particular pathogen. When an antibody finds its target, it first binds to the pathogen, then binds to immune cells, alerting them to attack the pathogen.
The attached sugar was believed necessary to allow antibodies to bind to immune cells, such as NK (natural killer) cells and macrophages. However, the MIT team found that mutant forms of the antibody with no sugar were also able to bind to immune cells.
Knowing this, scientists will now be able to develop therapeutic antibodies that can be mass-produced by bacteria or fungi, a process that is cheaper and faster than using mammalian cells.
There are now dozens of FDA-approved antibody treatments, and hundreds more are in clinical trials. Such therapeutic antibodies can be used to treat cancer, autoimmune diseases, cardiovascular disease and many others.
The new discovery also raises the question of why the sugars are attached to antibodies in the first place. Sazinsky theorizes that the sugar has been evolutionarily conserved as a way for the immune system (and now scientists) to tinker with the binding affinities of different antibodies.
Other authors of the paper are co-lead author Rene Ott of Rockefeller University; Nathaniel Silver, an MIT graduate student in chemistry; Bruce Tidor, MIT professor of biological engineering and computer science; and Jeffrey Ravetch of Rockefeller University.
The research was funded by the National Cancer Institute and the National Institutes of Health.

MIT News press release: Surprising find could lead to better manufacturing options for cancer-fighting antibodies…

At Christmas play and make good cheer,
For Christmas comes but once a year – Thomas Tusser
Do your New Year’s resolutions include losing weight and cutting back on a few of your indulgences? May not be a bad idea, but just in case you need another rationalization during the holidays, researchers at Oxford have released a study showing that brain performance is boosted by chocolate, wine, and tea!

All that chocolate might actually help finish the bumper Christmas crossword over the seasonal period. According to Oxford researchers working with colleagues in Norway, chocolate, wine and tea enhance cognitive performance.
The team from Oxford’s Department of Physiology, Anatomy and Genetics and Norway examined the relation between cognitive performance and the intake of three common foodstuffs that contain flavonoids (chocolate, wine, and tea) in 2,031 older people (aged between 70 and 74).
Participants filled in information about their habitual food intake and underwent a battery of cognitive tests.Those who consumed chocolate, wine, or tea had significantly better mean test scores and lower prevalence of poor cognitive performance than those who did not. The team reported their findings in the Journal of Nutrition.
The role of micronutrients in age-related cognitive decline is being increasingly studied. Fruits and beverages such as tea, red wine, cocoa, and coffee are major dietary sources of polyphenols, micronutrients found in plant-derived foods. The largest subclass of dietary polyphenols is flavonoids, and it has been reported in the past that those who consume lots of flavonoids have a lower incidence of dementia.
The latest findings seem to support the theory, although the researchers caution that more research would be needed to prove that it was flavonoids, rather than some other aspect of the foods studied, that made the difference.The effect was most pronounced for wine.
However, say the researchers, those overdoing it at Christmas should note that while moderate alcohol consumption is associated with better cognitive function and reduced risk of Alzheimer’s disease and dementia, heavy alcohol intake could be one of many causes of dementia – as well as a host of other health problems.

University of Oxford press release: Chocolate, wine and tea improve brain performance…