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Laser therapy may ease type of eczema

(Reuters Health) – Laser therapy that delivers a concentrated beam of ultraviolet light may help ease a hard-to-treat form of eczema, a small study suggests.


The study, published in the British Journal of Dermatology, compared the effects of laser therapy versus corticosteroid ointment in 13 patients with what is known as the prurigo form of atopic dermatitis.

Atopic dermatitis is a type of eczema, or skin inflammation, that arises from an allergic reaction; the prurigo form is marked by small, hard, intensely itchy nodules on the skin.

Only a small proportion of people with atopic dermatitis have the prurigo form, but the condition can be challenging to manage, according to Dr. Elian E.A. Brenninkmeijer, a dermatologist at the University of Amsterdam, in the Netherlands, and the lead researcher on the study.

The current findings, while based on only a small number of patients, suggest that when topical treatments fail to improve prurigo atopic dermatitis, laser therapy may be a suitable option, Brenninkmeijer told Reuters Health in an email.

Specifically, a device called the 308-nm excimer laser is approved in the U.S. for treating atopic dermatitis and certain other skin conditions, including psoriasis and vitiligo. It works by emitting a concentrated beam of ultraviolet B (UVB) light directly to patches of affected skin, avoiding the healthy surrounding skin.

UVB light has long been used to treat some cases of atopic dermatitis; it is thought to help by quelling the exaggerated immune response causing the skin inflammation. The purported advantage of the excimer laser over traditional UVB therapy is that it more precisely targets the problem areas of the skin.

However, there are only limited study data on the effectiveness of the laser therapy for atopic dermatitis, and almost nothing known about how it works for the prurigo form.

To investigate, Brenninkmeijer and his colleagues recruited 13 adults with atopic dermatitis and prurigo nodules on the upper or lower extremities on both sides of the body.

Over 10 weeks, the patients received twice-weekly laser treatments on one side of the body, and used prescription corticosteroid ointment — clobetasol propionate — on the other side of the body. Both the laser treatment and the ointment were applied directly to the prurigo nodules.

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Mapping Ancient Civilization, in a Matter of Days

For a quarter of a century, two archaeologists and their team slogged through wild tropical vegetation to investigate and map the remains of one of the largest Maya cities, in Central America. Slow, sweaty hacking with machetes seemed to be the only way to discover the breadth of an ancient urban landscape now hidden beneath a dense forest canopy.

Even the new remote-sensing technologies, so effective in recent decades at surveying other archaeological sites, were no help. Imaging radar and multispectral surveys by air and from space could not “see” through the trees.

Then, in the dry spring season a year ago, the husband-and-wife team of Arlen F. Chase and Diane Z. Chase tried a new approach using airborne laser signals that penetrate the jungle cover and are reflected from the ground below. They yielded 3-D images of the site of ancient Caracol, in Belize, one of the great cities of the Maya lowlands.

In only four days, a twin-engine aircraft equipped with an advanced version of lidar (light detection and ranging) flew back and forth over the jungle and collected data surpassing the results of two and a half decades of on-the-ground mapping, the archaeologists said. After three weeks of laboratory processing, the almost 10 hours of laser measurements showed topographic detail over an area of 80 square miles, notably settlement patterns of grand architecture and modest house mounds, roadways and agricultural terraces.

“We were blown away,” Dr. Diane Chase said recently, recalling their first examination of the images. “We believe that lidar will help transform Maya archaeology much in the same way that radiocarbon dating did in the 1950s and interpretations of Maya hieroglyphs did in the 1980s and ’90s.”

The Chases, who are professors of anthropology at the University of Central Florida in Orlando, had determined from earlier surveys that Caracol extended over a wide area in its heyday, between A.D. 550 and 900. From a ceremonial center of palaces and broad plazas, it stretched out to industrial zones and poor neighborhoods and beyond to suburbs of substantial houses, markets and terraced fields and reservoirs.

This picture of urban sprawl led the Chases to estimate the city’s population at its peak at more than 115,000. But some archaeologists doubted the evidence warranted such expansive interpretations.

“Now we have a totality of data and see the entire landscape,” Dr. Arlen Chase said of the laser findings. “We know the size of the site, its boundaries, and this confirms our population estimates, and we see all this terracing and begin to know how the people fed themselves.”

The Caracol survey was the first application of the advanced laser technology on such a large archaeological site. Several journal articles describe the use of lidar in the vicinity of Stonehenge in England and elsewhere at an Iron Age fort and American plantation sites. Only last year, Sarah H. Parcak of the University of Alabama at Birmingham predicted, “Lidar imagery will have much to offer the archaeology of the rain forest regions.”

The Chases said they had been unaware of Dr. Parcak’s assessment, in her book “Satellite Remote Sensing for Archaeology” (Routledge, 2009), when they embarked on the Caracol survey. They acted on the recommendation of a Central Florida colleague, John F. Weishampel, a biologist who had for years used airborne laser sensors to study forests and other vegetation.

Dr. Weishampel arranged for the primary financing of the project from the little-known space archaeology program of the National Aeronautics and Space Administration. The flights were conducted by the National Science Foundation’s National Center for Airborne Laser Mapping, operated by the University of Florida and the University of California, Berkeley.

Other archaeologists, who were not involved in the research but were familiar with the results, said the technology should be a boon to explorations, especially ones in the tropics, with its heavily overgrown vegetation, including pre-Columbian sites throughout Mexico and Central America. But they emphasized that it would not obviate the need to follow up with traditional mapping to establish “ground truth.”

Jeremy A. Sabloff, a former director of the University of Pennsylvania Museum of Archaeology and Anthropology and now president of the Santa Fe Institute in New Mexico, said he wished he had had lidar when he was working in the Maya ruins at Sayil, in Mexico.

The new laser technology, Dr. Sabloff said, “would definitely have speeded up our mapping, given us more details and would have enabled us to refine our research questions and hypotheses much earlier in our field program than was possible in the 1980s.”

At first, Payson D. Sheets, a University of Colorado archaeologist, was not impressed with lidar. A NASA aircraft tested the laser system over his research area in Costa Rica, he said, “but when I saw it recorded the water in a lake sloping at 14 degrees, I did not use it again.”

Now, after examining the imagery from Caracol, Dr. Sheets said he planned to try lidar, with its improved technology, again. “I was stunned by the crisp precision and fine-grained resolution,” he said.

“Finally, we have a nondestructive and rapid means of documenting the present ground surface through heavy vegetation cover,” Dr. Sheets said, adding, “One can easily imagine, given the Caracol success, how important this would be in Southeast Asia, with the Khmer civilization at places like Angkor Wat.”

In recent reports at meetings of Mayanists and in interviews, the Chases noted that previous remote-sensing techniques focused more on the discovery of archaeological sites than on the detailed imaging of on-ground remains. The sensors could not see through much of the forest to resolve just how big the ancient cities had been. As a consequence, archaeologists may have underestimated the scope of Mayan accomplishments.

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Rain-making lasers could trigger showers on demand

Lasers that stimulate condensation may help to induce rain artificially.

Zeeya Merali

The rain dance is getting a twenty-first-century revamp using laser technology. Optical physicists have demonstrated that shooting lasers into the air can trigger the formation of water droplets, a technique that could one day help to stimulate rainfall.

For more than 50 years, efforts to try to artificially induce rain have concentrated on ‘cloud seeding’ — scattering small particles of silver iodide into the air to act as ‘condensation nuclei’, or centres around which rain droplets can grow. “The problem is, it’s still not clear that cloud seeding works efficiently,” says optical physicist Jérôme Kasparian at the University of Geneva, Switzerland. “There are also worries about how safe adding silver iodide particles into the air is for the environment.”

Kasparian and his colleagues realized that there might be a more environmentally friendly alternative. Firing a laser beam made up of short pulses into the air ionizes nitrogen and oxygen molecules around the beam to create a plasma, resulting in a ‘plasma channel’ of ionized molecules. These ionized molecules could act as natural condensation nuclei, Kasparian explains.

To test whether this technique could induce droplets, the researchers fired a high-powered laser through an atmospheric cloud chamber in the lab containing saturated air (see video). They illuminated the chamber using a second, standard low-power laser, enabling them to see and measure any droplets produced. Immediately after the laser was fired, drops measuring about 50 micrometres wide formed along the plasma channel. Over the next three seconds, the droplets grew in size to 80 micrometres as the smaller droplets coalesced. The team’s results are published online in Nature Photonics1.


The next step for Kasparian and his team was to take the technique outside. The researchers already have experience using plasma channels to modify the weather: in 2008, they demonstrated that a beam from their high-powered portable ‘Teramobile laser’ could be fired into thunder clouds, triggering an electric discharge2. The beam was able to reach its target without being deflected because the generated plasma channel modifies the speed at which light travels through air — slowing it down in the centre of the beam and speeding it up at the sides. This causes the beam to continually self-focus, helping it to maintain a high intensity across large distances (see ‘Bendy laser beam fired through the air’).

This time, Kasparian and his colleagues tested the Teramobile laser over a number of different nights and in various humidity conditions. Once again, they detected the amount of condensation induced by monitoring how much the light from a second laser was back-scattered by any droplets. In low humidity conditions, the Teramobile laser did not induce droplets. But when the humidity was high, the team measured up to 20 times more back-scattering after the Teramobile laser was fired than before, says Kasparian, suggesting that condensation droplets were forming.

Roland Sauerbrey, an expert on laser physics at the FZD Dresden–Rossendorf Research Centre in Dresden, Germany, says that the team has the potential to create a “breakthrough technology”. “This is the first time that a laser has been used to cause condensation outdoors,” he says.

However, the technique is still in its early stages. “We can only create condensation along the laser channel, so we won’t be going out and making rain tomorrow,” Kasparian notes. He and his team are now investigating whether they can create condensation over a wider area, by sweeping their laser across the sky.

Thomas Leisner, an atmospheric physicist at the Karlsruhe Institute of Technology, Germany, remains cautious about the feasibility of scaling up the technique in this way. “I am sceptical that this could be used to trigger rain on demand,” he says. But he adds that the technology will have other uses. The researchers should now calibrate the relationship between the amount of condensation produced by the laser and the prevailing atmospheric conditions, he says. “They could use the amount of condensation produced by their laser as a measure of water saturation to help forecast the chance of rain,” he says. 

  • References
    1. Rohwetter, P. et al. Nature Photonics advance online publication doi:10.1038/nphoton.2010.115 (2010).
    2. Kasparian, J. et al. Opt. Express 16, 5757-5763 (2008). | Article

Source : naturenews

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