Tag Archives: ultraviolet

Hummingbird eyes can detect UV, allowing them to see the world in colors that humans can’t even imagine

The male broad-tailed hummingbird can see combinations of colors like ultraviolet plus green or ultraviolet plus red. In fact, the bird’s throat, which looks like magenta to us, is likely perceived as ultraviolet plus purple by birds.

Compared to many birds, such as the delightful hummingbird (Colibri), humans are color-blind, says Mary Caswell Stoddard. The Princeton University professor, along with colleagues, showed that hummingbirds are able to discriminate various ultraviolet (UV) color combinations, allowing the birds to see the world in additional colors that humans can’t even comprehend.

A hidden world of ultraviolet

Humans essentially see the world in a combination of three colors: red, green, and blue. Each primary color is detected and decoded by corresponding specialized cones in the eye.

The hummingbird, however, has a fourth color cone, which extends its color-vision range into the ultraviolet. But, how exactly does this additional color cone morph the bird’s vision?

In their new study, Stoddard and colleagues left their labs at Stanford and traveled to Gothic, Colorado, for fieldwork in the alpine meadows each summer over the course of three years.

Their work mainly focused on how hummingbirds sense non-spectral colors, which are combinations of hues from widely separated parts of the color spectrum. A clear example of a non-spectral color is purple, which combines blue and red wavelengths of light, but not green. In contrast, teal (blue-green) and yellow (green-red) are blends of neighboring colors in the spectrum.

In fact, purple is the only non-spectral color that humans can sense. But birds should theoretically be able to see up to five, thanks to their extra color cone type. In addition to purple, birds should also be able to see combinations of ultraviolet and red, green, yellow, and purple, respectively.

“Most detailed perceptual experiments on birds are performed in the lab, but we risk missing the bigger picture of how birds really use color vision in their daily lives,” Stoddard said in a statement. “Hummingbirds are perfect for studying color vision in the wild. These sugar fiends have evolved to respond to flower colors that advertise a nectar reward, so they can learn color associations rapidly and with little training.”

The research team performed a series of experiments with wild broad-tailed hummingbirds (Selasphorus platycercus) that had two feeders at their disposal that they could use. One contained sugary water, the other just plain water.

Each feeder had an LED tube that flashed various colors. The tube that corresponded to sugar water emitted one color, while the other emitted a different color — with an important caveat.

To you or I, both colors look the same, i.e. green. However, the LEDs can display a broad range of colors, including non-spectral colors like ultraviolet plus green. If the birds could indeed see additional non-spectral colors, this should be obvious from their choice of feeders.

The researchers swapped the positions of the rewarding and unrewarding tubes at random intervals of time to make sure the birds weren’t going to the same location to pinpoint the treat. They also performed control experiments to rule out the influence of smell or anything other non-vision-related cues.

Over the course of 19 experiments, the researchers recorded over 6,000 feeder visits. An analysis of the hummingbirds’ feedings patterns showed that the birds can distinguish ultraviolet plus green from pure ultraviolet or pure green, as well as two different blends of ultraviolet plus red light (one redder, the other less so).

“It was amazing to watch,” said Harold Eyster, a University of British Columbia Ph.D. student and a co-author of the study. “The ultraviolet+green light and green light looked identical to us, but the hummingbirds kept correctly choosing the ultraviolet+green light associated with sugar water. Our experiments enabled us to get a sneak peek into what the world looks like to a hummingbird.”

You might be curious to learn what these additional colors look like. Unfortunately, there is no way to see them — we simply lack the hardware to do so due to the absence of the fourth color cone type.

“The colors that we see in the fields of wildflowers at our study site, the wildflower capital of Colorado, are stunning to us, but just imagine what those flowers look like to birds with that extra sensory dimension,” said co-author David Inouye.

No need to be too jealous, though. The researchers also analyzed a dataset of 3,315 feather and plant colors and found that birds likely perceive many of these colors as non-spectral. However, these non-spectral colors do not stand out relative to other colors that are also visible to humans.

The findings appeared in the journal Proceedings of the National Academy of Sciences.

Complex glass objects 3D-printed using new take on old method

Researchers at ETH Zürich have developed the first 3D-printing method that can produce highly-complex, porous glass objects. The approach relies on a special resin that can be cured using ultraviolet (UV) light.

Several of the 3-D printed objects created by the team.
Image credits Group for Complex Materials / ETH Zurich.

Glass has been a long-standing goal of 3D-printing enthusiasts for a long time now; it’s also proven to be the most elusive. The inherent problem regarding printable glass is that the material requires very high temperatures to process. The two approaches we’ve tried so far are to either ‘print’ molten glass — which requires expensive and specialized heat-resistant equipment — or to use ceramic powders as ink to sinter into glass — an approach that sacrifices precision and thus the complexity of the finished product.

In order to solve the issue, the team from ETH Zurich went back to the roots, and worked from stereolithography, one of the first 3-D printing techniques developed during the 1980s. They developed a resin which contains a plastic material and organic molecules tied to glass precursors that can be hardened by exposure to UV light.

A light touch

When blasted with UV light — the team says commercially available Digital Light Processing technology works just fine — photosensitive components in the resin bind together. The plastic in the ink forms into a maze-like polymer that provides the structural framework. Ceramic-bearing molecules link together in the empty areas created by the framework.

This allows an object to be built layer-by-layer, and by modifying the intensity of the UV light, the team can change various parameters in each layer. Weak light intensity results in large pores, for example, while intense illumination produces small pores.

“We discovered that by accident, but we can use this to directly influence the pore size of the printed object,” says Kunal Masania, a co-author of the study.

So where does the glass fit into this? The team explains that they can modify the microstructure of their (hardened) ink by mixing silica with borate or phosphate and adding it to the resin. Silica is the main component of glass, while borate and phosphate are added to specialized, heat-resistant and optical glass respectively. The team explains that their approach allows for single or multiple types of inks to be mixed into a single object, allowing for several kinds of glass to be produced in the end.

The final step involves using heat to actually turn the hardened ink into glass. The printed ‘blanks’ are fired at 600˚C, which burns away the polymer framework, and then at 1000˚C to transform the ceramic structure into glass. During the thermal treatment, the blanks shrink significantly, the authors report, while becoming as transparent and hard as window glass.

So far, the approach can only be used for small objects — about the size of a die. Larger objects such as bottles, drinking glasses, or window panes cannot be produced this way, but that wasn’t the goal here, Masania explains. The team wanted to prove that glass is a viable material for 3D-printing, he explains.

The team has applied for a patent on their technology and are negotiating with industry representatives to take their process to market.

The paper “Three-dimensional printing of multicomponent glasses using phase-separating resins” has been published in the journal Nature Materials.

Pink Squirrel.

North American flying squirrels are bright pink — under UV light

A chance sighting revealed that the North American flying squirrel (and its related species) glow bright pink under fluorescent light.

Pink Squirrel.

A flying squirrel seen under normal (top) and ultraviolet light.
Credit: Kohler et al., (2019), JoM.

Dr. Jon Martin, associate professor of forestry at Northland College in Wisconsin, stumbled upon the discovery in his own back yard. He was doing an exploratory forest survey with an ultraviolet flashlight, trying to find what lichens, mosses, and plants fluoresced. By chance, however, a flying squirrel dining at his bird feeder startled him, and he beamed his flashlight at it — and it glowed pink.

Secretly pink

Martin set up a team to further investigate the issue, which included Allison Kohler, a graduate student in the Texas A&M University wildlife and fisheries department, as well as Dr. Paula Anich, associate professor of natural resources, and Dr. Erik Olson, assistant professor of natural resources, both at Northland College.

The team first requested access to the collection of the Minnesota Science Museum, to see if their hypothesis holds or if it was just a figment of Martin’s imagination.

“I looked at a ton of different specimens that they had there,” Kohler said. “They were stuffed flying squirrels that they had collected over time, and every single one that I saw fluoresced hot pink in some intensity or another.”

Next, they expanded their investigations to the collection of the Field Museum of Natural History in Chicago. All in all, they looked at over 100 specimens ranging across numerous states by this point, and all of them confirmed their “pink theory.” They then looked at three live specimens of different species of North American flying squirrels — the Northern flying squirrel, the Southern flying squirrel, and Humboldt’s flying squirrel. “All three of them fluoresced,” Kohler recounts.

Comparison with flying species of other squirrels, like the American red squirrel and gray squirrel, revealed that the pink fluorescent color is unique to the flying squirrel (genus Glaucomys).

Exactly why they glow bright pink under UV isn’t known. They’re not the only species to show fluorescence, however. The team’s running hypothesis is that it aids in communication and/or camouflage, but they’ve yet to confirm their suspicions.

“They could be communicating with members of their own species by showing off their fluorescence to each other, or it might be a sort of mating display,” Kohler said.

“The other hypothesis is that they could be using this fluorescence as an anti-predator trait to communicate with other species, avoiding predation by other species by blending in or dealing with their potentially ultraviolet-saturated environments.”

So far, the findings don’t seem particularly important, since we don’t yet know where they fit in the larger picture. Kohler, however, says she will continue expanding on the issue while pursuing her master’s degree at Texas A&M — hopefully, this will reveal the full implications of the team’s finding.

“It could potentially help with the conservation of the species or other species, and it could also relate to wildlife management,” Kohler said. “The more that we know about the species, the more we can understand it and help it. This is opening a new door to the realm of nocturnal-crepuscular, or active during twilight, communication in animals.”

The paper “Ultraviolet fluorescence discovered in New World flying squirrels (Glaucomys)” has been published in the Journal of Mammalogy.

Robots might soon be sanitizing hospital rooms, killing far more bacteria than humans

With drug-resistant bacteria being more dangerous than ever, we need all the help we can get.

Image credits: Infection Prevention Technologies / Youtube.

Technology could help temper this ever-growing problem — hospital infections are running rampant, but they may be pushed back by ultraviolet (UV) Robots.

Current cleaning techniques, almost always manual, are nearly helpless in tackling resilient bacteria. This is where the disinfection robots enter the stage.

At certain wavelengths, UV light is mutagenic to bacteria, viruses, and other microorganisms. Particularly at wavelengths around 260 to 270 nanometers (the visible range is around 380 to 750 nanometers), UV light breaks molecular bonds within microorganismal DNA, severely disabling or killing the organisms.

The use of UV as a disinfectant isn’t new. It’s been used in medical sanitation and sterile work facilities since the mid-20th century, and more recently, it’s also been used to sterilize drinking and wastewater facilities.

Now, researchers have fitted UV lamps on disinfection robots which ensure full-room sterilization. Nursing homes, field hospitals, and biohazard zones could all be sterilized in a matter of minutes. The robots are faster and more efficient than human workers, and their ability to move around enables them to cover the entirety of the room, including shadowy areas and corners, as well as door handles and bed frames.

Infection Prevention Technologies (iPT), the company which built the robot, has reportedly tested the technology and found that after 10 minutes, the rooms were completely sterilized. This could go a long way towards reducing hospital infections.

“A 6-month, hospital-wide study showed a 34% drop in the incidence of healthcare associated infections with the use of the IPT 3200 UV robot and specially trained disinfection teams.” iPT claims.

Results have been presented in a new paper.

“One of the problems facing our healthcare system is hospital-associated infections,” says Nicholas Fitzkee, an independent scientist of the paper. Infections cost “thousands of lives and billions of dollars annually”, he adds.

Another advantage of the technology is that it requires minimal human intervention: just one person to guide and monitor the robot.

At the currently used levels, the radiation is harmless to humans. However, it’s still recommended that humans exit the room during the sterilization process.

According to the World Health Organization, drug-resistant pathogens are one of the biggest threats to mankind, and things are only expected to get worse. The CDC also warns that unusual germs with unusual drug-resistance are now widespread in the US. Technologies such as UV sanitizing could go a long way towards fighting that problem where it matters most (hospitals) and kill off some of the most resilient pathogens.

Germicidal UV.

Far-ultraviolet lamps could eradicate airborne viruses in public spaces — with no risk to us

Flooding public spaces with far-UVC light, a type of ultraviolet light that’s harmless to humans, could finally spell the end of seasonal flu epidemics.

Germicidal UV.

Germicidal UV tube.
Image via Wikimedia.

Continuous but low doses of far-ultraviolet C light (far-UVC) will kill airborne flu viruses while leaving human cells unscathed, new research has found. Their use in hospitals, doctors’ offices, schools, airplanes, and other public spaces could become a powerful tool against seasonal influenza epidemics, and influenza pandemics, according to a study from the Center for Radiological Research at Columbia University Irving Medical Center (CUIMC).

Tan-tastic way to fight the flu

Researchers have known for decades that short-wavelength UV light (dubbed UVC) is highly effective at killing bacteria and viruses. That’s because the radiation’s relatively tiny wavelength, of between 200 and 400 nanometers, allows it to pierce through the organisms’ shells and wreak havoc on the molecular bonds in their genetic material. In fact, it’s so good at doing it, that conventional UV light is routinely used to disinfect and decontaminate surgical tools and equipment.

“Unfortunately, conventional germicidal UV light is also a human health hazard and can lead to skin cancer and cataracts, which prevents its use in public spaces,” said lead author David J. Brenner.

However, the narrow spectrum of ultraviolet light called far-UVC retains this microbe-killing potential but without the ability to damage human tissue. That’s the spectrum that Brenner and his team focused on in their research. Previously, Dr. Brenner’s team proved that far-UVC light could kill MRSA (methicillin-resistant S. aureus) bacteria, a common culprit for surgery-associated infections, without harming human or mouse skin.

“Far-UVC light has a very limited range and cannot penetrate through the outer dead-cell layer of human skin or the tear layer in the eye, so it’s not a human health hazard. But because viruses and bacteria are much smaller than human cells, far-UVC light can reach their DNA and kill them,” he explains.

Influenza spreads from person to person mainly through fine drops of liquid (aerosols) that float around after people cough, sneeze, or talk. The study examined whether far-UVC light could efficiently kill aerosol-borne influenza viruses in settings similar to a public space. They worked with an aerosolized H1N1 virus, a common strain of the flu, which they released into a test chamber, and later exposed to very low doses of far-UVC light (222 nm). A control group was similarly aerosolized but not exposed to UVC light.

The results showed that far-UVC light inactivated the viruses with roughly the same efficiency as conventional UV disinfection treatments. If the results can be recreated in other settings, the team is confident that overhead, low-level far-UVC lighting in public locations could form a powerful tool for limiting the airborne transmission and spread of microbial diseases, “such as influenza and tuberculosis,” said Dr. Brenner. It would be a comparatively cheap measure, as far-UVC lights are relatively inexpensive and broadly-applicable.

“Unlike flu vaccines, far-UVC is likely to be effective against all airborne microbes, even newly emerging strains.”

The paper “Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases,” has been published in the journal Scientific Reports.

Self-tanning drug could fight skin cancer — and improve your beach experience

A new compound promises to give you a nice sun tan without any radiation at all.

A natural tan is much better than a tanning bed, but it can still be unhealthy. Image via Max Pixel.

Getting a tan

When we’re exposed to ultraviolet (UV) rays, our body starts to trigger a series of chemical reactions which lead to the production of melanin. Melanin is a pigment that gives skin, hair, and eyes their color. The extra production darkens our skin, which protects us against the damaging effect of the sun’s rays. That’s right, a tan is your body’s way of protecting you against the Sun.

Now, researchers from the Massachusetts General Hospital have created a drug that tricks the body into developing a tan without any sunlight whatsoever. This is a markedly different effect to fake tan, which basically “paints” the skin without adding any melanin and any protection against UVs. It’s also very different to so-called tanning pills, which can increase your melanin production but still require exposure to UVs. This is the real deal — you rub it on your skin, and the body starts to produce melanin.

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“It has a potent darkening effect,” said Dr. David Fisher, one of the researchers involved in the project. “Under the microscope, it’s the real melanin, it really is activating the production of pigment in a UV-independent fashion.”

Fighting cancer

Even if you can’t see it directly, sunscreen does a lot of work protecting your skin from UV light. Image credits: Spigget / Wikipedia.

They’re also not doing this for a cosmetic reason — they have their eyes set on a much bigger problem: skin cancer. In 2015, there were 5.6 identified cases of skin cancer, many of which are associated with exposure to UV light. Tanning beds are also a growing problem. It is believed that tanning beds are the cause of hundreds of thousands of cases of cancer, with the World Health Organization placing tanning bed users at the highest risk of developing skin cancer. Of course, sunscreen helps, but people often misuse the sunscreen or don’t use appropriate protection. Also, sunscreen has the nasty habit of keeping your skin white, which is considered undesirable by many people who want to develop a tan.

“We know what causes skin cancer – it’s really associated with UV radiation – and yet it’s at the top of the list [of most common cancers], and it continues to increase in frequency,” says David Fisher, a dermatologist at Massachusetts General Hospital who led the research. “Sunscreen does prevent skin cancer. It has been shown. But it’s not enough. What I think could be done is to use sunscreen that has been supplemented by something to darken the skin.”

This discovery didn’t come out of the blue. Fisher has spent the past ten years figuring out how UV exposure triggers the production of melanin and previously gave mice a nice tan using a similar approach. But with human skin being five times thicker than that of mice, it took quite a while before they found something that seems to work.

In mice, Fisher and colleagues activate the pathway by inhibiting a type of enzymes, called salt-inducible kinases (SIK). But the inhibitors couldn’t penetrate human skin, so they needed to find a workaround. Working with chemist Nathaniel Gray, they found another type of SIK inhibitors which does the same job. The response of the skin completely mimicked that of a natural tan, without any visible side effects.

 “We’ve got several compounds that we can apply right onto human skin that was kept alive artificially in a petri dish,” Fisher says. “We could see that the skin starts to turn dark.”

This could save millions and millions of lives, especially with skin cancer rates going through the roof around the world. Matthew Gass, from the British Association of Dermatologists, praised the study, saying that it was a “novel approach.”

The team is also looking into ways this could help people with autoimmune diseases such as vitiligo, or how it could be applied to redheads, who don’t really tan — they just get burns when exposed to the sun because their skin doesn’t produce the extra melanin.

“Assuming there are no safety concerns, it is clearly a better option than UV exposure,” says Jerod Stapleton, a behavioral scientist at the Rutgers Cancer Institute of New Jersey in New Brunswick who studies indoor tanning and was not involved in the work. “We are talking about millions of young people potentially not using tanning beds each year. … It could be a game-changer for skin cancer prevention.”

Before we get overly excited about this, it’s important to note that it hasn’t been tested on humans yet — only on mice and patches of human skin leftover from surgeries. Fisher says it will still be three to five years before they move on to clinical trials.

Journal Reference: Nisma Mujahid et al — A UV-Independent Topical Small-Molecule Approach for Melanin Production in Human Skin. DOI: http://dx.doi.org/10.1016/j.celrep.2017.05.042

myopia children playing

Play outside, kids! Sunlight reduces chances of myopia in children

You often hear people complaining that kids don’t play outside anymore – instead just hanging in the house all day long, playing on the computer (tablet/xbox/whatever). This is a pretty big problem, because there is a myriad of advantages to playing outside; this study has added yet another advantage to that list: playing outside reduces the risk of myopia in kids.

myopia children playing

Playing outside seems to reduce the risk of myopia in children. Image via PicturesNew.

For quite a long time, it was thought that playing in front of the computer instead of playing outside can damage your eyes; this has been proven wrong, but now, research has shown that if you play outside as a kid, you have better chances of not developing myopia, though it’s not clear why.

“We don’t really know what makes outdoor time so special,” said Donald Mutti, the lead researcher of the study from Ohio State University College of Optometry, in a press release. “If we knew, we could change how we approach myopia.”

Myopia (or short-sightedness) is a condition in which the light that comes in the eye does not directly focus on the retina but in front of it, causing the image that one sees when looking at a distant object to be out of focus. The causes of myopia are still elusive and to make things even more interesting, a number of studies have shown the incidence of myopia increases with level of education. Many studies have shown a correlation between myopia and a higher intelligence quotient (IQ). Myopia is also highly hereditary.

But whatever the cause may be, sunlight seems to work against the condition. Previous research showed that UVB light, (invisible ultraviolet B rays), plays a role in the cellular production of vitamin D, which helps the eyes focus light on the retina. But study authors believe there is another reason why playing outside fights against myopia.

“Between the ages of five and nine, a child’s eye is still growing,” said Mutti. “Sometimes this growth causes the distance between the lens and the retina to lengthen, leading to nearsightedness. We think these different types of outdoor light may help preserve the proper shape and length of the eye during that growth period.”

The pupil also seems to play a role here – when exposed to more light (like in the outdoors), the pupil dilates. But not all light comes equally, and natural sunlight seems to yield better effects.

“Our initial research suggests that the pupil responds more if these cells have been exposed to a lot of sunlight in the previous few days.”

The key threshold seems to be 14 hours (or more) a week; even kids who are genetically susceptible to myopia are three times less likely to need glasses provided they are playing in the sun for at least 14 hours a week.

There are many more questions to be answered, but ultimately, the takeaway message is that kids should play outside – if not for their own development and fun, then at least for their eyes.

“I think the research we are doing now will help us finally solve the mystery of the outdoor effect, and maybe help some people avoid a lifetime of wearing glasses,” he said. “In the meantime, I tell parents don’t worry about reading, get their kids outside, but don’t forget … sunscreen.”

Journal Reference: Lisa A. Jones-Jordan, Loraine T. Sinnott, Nicholas D. Graham, Susan A. Cotter, Robert N. Kleinstein, Ruth E. Manny, Donald O. Mutti, J. Daniel Twelker, Karla Zadnik, for the CLEERE Study Group. The Contributions of Near Work and Outdoor Activity to the Correlation Between Siblings in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. Published online before print September 9, 2014, doi: 10.1167/iovs.14-14640

Tomorrow’s camera is flash free, regardless of light conditions

As any amateur photographer can tell you, in order to take a clear picture, you require a good light source; so in poor light conditions, the solution was the intense flash. However, there are some obvious disadvantages.

Still, computer scientist Rob Fergus started thinking if we actually need such an intense light source, or if we could actually develop some sort of invisible flash that would solve the inconvenient that come with the traditional camera flash.

F is a multi spectral flash, A is using ambiental lighting, which is way lower than it should be, R is a combined version of the two, and L is a reference long exposure shot

So one year later, the end result was a camera that emits and records light outside the visible spectrum. Practically, the prototype emits a flash, but you just don’t see it, and the photographs are as good as old-school flash ones. How does it work ? Well, usually, cameras have a filter that prevents any type of light from the infrared spectrum.  For this innovative camera, Fergus replaced the filter; the UV however, was a little trickier. His camera could already detect UV, but sending it out, that was a real challenge. So he employed the help of some hobbyists that use UV photography to reveal hidden patterns on flowers: landing strips for insects, polinators, etc.

So the camera is done, but is it any good ? Well, it most definitely is. as you can see for yourself.

“Most pictures you take with a flash look quite crappy,” says Ankit Mohan, an expert in camera technology at the Massachusetts Institute of Technology says. “They look kind of flat, you get the red-eye effect, and one part of the scene is always much brighter than another part. But the problem of capturing a picture with no flash is that you don’t get detail. By combining the two you get the best of both worlds.”

Despite the comfort advantages it provides, this development is also quite useful in some fields.

Cramer Gallimore, a professional photographer based in North Carolina, believes dark-flash photography has great potential. “You might be able to take high-quality photographs of wildlife without disturbing them,” Gallimore says, “and for forensic photography, it would be very useful to have technology like this that could switch between infrared technology and visible light photography to record certain traces of human activity at a crime scene.”

Source: Popular Mechanics