Dr. Barbara Veselka: “The results from our study represent a major step forward in the fields of biological anthropology, archaeology, and palaeopathology by opening up a variety of new possibilities for the study of health and activities related to sunlight exposure of numerous past populations that practiced cremation as their funerary ritual.” The study was published in the academic journal Scientific Reports.

Burning experiments

As part of the Brussels Bioarchaeology Lab (www.bb-lab.be) and the MARI and AMGC research groups, Dr. Barbara Veselka and Prof. Christophe Snoeck conducted burning experiments using an archaeological sample of 17 paired teeth.

Veselka: “We conducted burning experiments with teeth to assess the visibility of interglobular dentine, a mineralization defect in the dentine attributed to vitamin D deficiency, in teeth burned at temperatures varying from 600 to 900°C. Our study is the first to demonstrate that this defect is still visible at temperatures up to 900°C. This enables, for the first time, the identification of vitamin D deficiency in cremated human remains.”

Sixteen pairs of molars came from the cemetery of Koekelberg, Belgium, and one pair of canines came from the cemetery of the Broerekerk Zwolle, the Netherlands. From each pair, one unburnt tooth was microscopically evaluated via thin section for interglobular dentine. The other tooth was burned at temperatures of 600, 800, or 900°C. Duration of the burning process was 2, 4, or 8 hr. Each of the burnt teeth were examined for interglobular dentine and compared to their unburnt counterparts.

Study of sunlight exposure in the past

The fact that interglobular dentine is still visible in teeth burned at temperatures of 900°C is remarkable and allows the assessment of vitamin D deficiency in past populations. Moreover, the age at which the disease occurred, the severity of the deficit, and if the disease was recurrent can also be determined. Since most of vitamin D deficient cases can be attributed to limited exposure to adequate amounts of sunlight, information on the age of occurrence aids in the reconstruction of daily activities related to sunlight exposure.

Veselka: “This innovative study stimulates more bioarchaeological research, which will increase our understanding of the influence environmental and sociocultural variables have on individuals.”

Story Source:

Materials provided by Vrije Universiteit Brussel. Note: Content may be edited for style and length.

But the control of light can also come in high-tech forms. The screen of the computer, tablet, or phone on which you are reading this is one example. Another is telecommunications, which controls light to create signals that carry data along fiber-optic cables.

Scientists also use high-tech methods to control light in the laboratory, and now, thanks to a new breakthrough that uses a specialized material only three atoms thick, they can control light more precisely than ever before.

The work was conducted in the lab of Harry Atwater, the Otis Booth Leadership Chair of the Division of Engineering and Applied Science, Howard Hughes Professor of Applied Physics and Materials Science, and director of the Liquid Sunlight Alliance (LiSA). It appears in a paper published in the October 22 issue of Science.

To understand the work, it is helpful first to remember that light exists as a wave and that it has a property known as polarization, which describes the direction in which the waves vibrate. Imagine being in a boat bobbing on the ocean: Ocean waves have a vertical polarization, which means that as the waves pass under the boat, it goes up and down. Light waves behave in much the same way, except these waves can be polarized at any angle. If a boat could ride waves of light, it might bob from side to side, or on a diagonal, or even in a spiraling fashion.

Polarization can be useful because it allows light to be controlled in specific ways. For example, the lenses in your sunglasses block glare (light often becomes polarized when it reflects off a surface, like the window of a car). The screen of a desk calculator creates legible numbers by polarizing light and blocking it in areas. Those areas where the polarized light is blocked appear dark, while areas where the light is not blocked appear light.

In the paper, Atwater and his co-authors describe how they used three layers of phosphorus atoms to create a material for polarizing light that is tunable, precise, and extremely thin.

The material is constructed from so-called black phosphorus, which is similar in many ways to graphite, or graphene, forms of carbon that consist of single-atom-thick layers. But whereas the layers of graphene are perfectly flat, black phosphorus’s layers are ribbed, like the texture of a pair of corduroy pants or corrugated cardboard. (Phosphorus also comes in red, white, and violet forms, distinct because of the arrangement of the atoms within it.)

That crystal structure, Atwater says, makes the black phosphorus have significantly anisotropic optical properties. “Anisotropy means is that it’s angle dependent,” he explains. “In a material like graphene, light is absorbed and reflected equally no matter the angle at which it’s polarized. Black phosphorus is very different in the sense that if the polarization of light is aligned along the corrugations, it has a very different response than if it’s aligned perpendicular to the corrugations.”

When polarized light is oriented across the corrugations in black phosphorus, it interacts with the material differently than when it is oriented along the corrugations — kind of like how it is easier to rub your hand along the ribs in corduroy than it is to rub your hand across them.

Many materials can polarize light, though, and that ability alone is not especially useful. What makes black phosphorus special, Atwater says, is that it is also a semiconductor, a material that conducts electricity better than an insulator, like glass, but not as well as a metal like copper. The silicon in microchips is an example of a semiconductor. And just as how tiny structures built from silicon can control the flow of electricity in a microchip, structures built from black phosphorus can control the polarization of light as an electric signal is applied to them.

“These tiny structures are doing this polarization conversion,” Atwater says, “so now I can make something that’s very thin and tunable, and at the nanometer scale. I could make an array of these little elements, each of which can convert the polarization into a different reflected polarization state.”

The liquid crystal display (LCD) technology found in phone screens and TVs already has some of those abilities, but black phosphorus tech has the potential to leap far ahead of it. The “pixels” of a black phosphorus array could be 20 times smaller than those in LCDs, yet respond to inputs a million times faster.

Such speeds are not necessary for watching a movie or reading an article online, but they could revolutionize telecommunications, Atwater says. The fiber-optic cable through which light signals are sent in telecommunications devices can transmit only so many signals before they begin to interfere with and overwhelm each other, garbling them (picture trying to hear what a friend is saying in a crowded and loud bar). But a telecommunications device based on thin layers of black phosphorus could tune the polarization of each signal so that none interfere with each other. This would allow a fiber-optic cable to carry much more data than it does now.

Atwater says the technology could also open the door to a light-based replacement for Wi-Fi, something researchers in the field refer to as Li-Fi.

“Increasingly, we’re going to be looking at light-wave communications in free space,” he says. “Lighting like this very cool-looking lamp above my desk doesn’t carry any communication signal. It just provides light. But there’s no reason that you couldn’t sit in a future Starbucks and have your laptop taking a light signal for its wireless communication rather than a radio signal. It’s not quite here yet, but when it gets here, it will be at least a hundred times faster than Wi-Fi.”

The paper describing the work is titled, “Broadband electro-optic polarization conversion with atomically thin black phosphorus.” The lead author is Souvik Biswas, graduate student in applied physics. Other co-authors are Meir Y. Grajower, postdoctoral scholar research associate in applied physics and materials science, and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan.

“These are exciting times for new materials discovery that can shape the future of photonic devices, and we have barely scratched the surface,” Biswas says. “It would be gratifying if some day you could buy a commercial product constructed out of such atomically thin materials, and that day might not be very far.”

Funding for the research was provided by the U.S. Department of Energy; Japan’s Ministry of Education, Culture, Sports, Science and Technology; the Japan Society for the Promotion of Science; and the Japan Science and Technology Agency.

Most of us control light all the time without even thinking about it, usually in mundane ways: we don a pair of sunglasses and put on sunscreen, and close — or open — our window blinds.

But the control of light can also come in high-tech forms. The screen of the computer, tablet, or phone on which you are reading this is one example. Another is telecommunications, which controls light to create signals that carry data along fiber-optic cables.

Scientists also use high-tech methods to control light in the laboratory, and now, thanks to a new breakthrough that uses a specialized material only three atoms thick, they can control light more precisely than ever before.

The work was conducted in the lab of Harry Atwater, the Otis Booth Leadership Chair of the Division of Engineering and Applied Science, Howard Hughes Professor of Applied Physics and Materials Science, and director of the Liquid Sunlight Alliance (LiSA). It appears in a paper published in the October 22 issue of Science.

To understand the work, it is helpful first to remember that light exists as a wave and that it has a property known as polarization, which describes the direction in which the waves vibrate. Imagine being in a boat bobbing on the ocean: Ocean waves have a vertical polarization, which means that as the waves pass under the boat, it goes up and down. Light waves behave in much the same way, except these waves can be polarized at any angle. If a boat could ride waves of light, it might bob from side to side, or on a diagonal, or even in a spiraling fashion.

Polarization can be useful because it allows light to be controlled in specific ways. For example, the lenses in your sunglasses block glare (light often becomes polarized when it reflects off a surface, like the window of a car). The screen of a desk calculator creates legible numbers by polarizing light and blocking it in areas. Those areas where the polarized light is blocked appear dark, while areas where the light is not blocked appear light.

In the paper, Atwater and his co-authors describe how they used three layers of phosphorus atoms to create a material for polarizing light that is tunable, precise, and extremely thin.

The material is constructed from so-called black phosphorus, which is similar in many ways to graphite, or graphene, forms of carbon that consist of single-atom-thick layers. But whereas the layers of graphene are perfectly flat, black phosphorus’s layers are ribbed, like the texture of a pair of corduroy pants or corrugated cardboard. (Phosphorus also comes in red, white, and violet forms, distinct because of the arrangement of the atoms within it.)

That crystal structure, Atwater says, makes the black phosphorus have significantly anisotropic optical properties. “Anisotropy means is that it’s angle dependent,” he explains. “In a material like graphene, light is absorbed and reflected equally no matter the angle at which it’s polarized. Black phosphorus is very different in the sense that if the polarization of light is aligned along the corrugations, it has a very different response than if it’s aligned perpendicular to the corrugations.”

When polarized light is oriented across the corrugations in black phosphorus, it interacts with the material differently than when it is oriented along the corrugations — kind of like how it is easier to rub your hand along the ribs in corduroy than it is to rub your hand across them.

Many materials can polarize light, though, and that ability alone is not especially useful. What makes black phosphorus special, Atwater says, is that it is also a semiconductor, a material that conducts electricity better than an insulator, like glass, but not as well as a metal like copper. The silicon in microchips is an example of a semiconductor. And just as how tiny structures built from silicon can control the flow of electricity in a microchip, structures built from black phosphorus can control the polarization of light as an electric signal is applied to them.

“These tiny structures are doing this polarization conversion,” Atwater says, “so now I can make something that’s very thin and tunable, and at the nanometer scale. I could make an array of these little elements, each of which can convert the polarization into a different reflected polarization state.”

The liquid crystal display (LCD) technology found in phone screens and TVs already has some of those abilities, but black phosphorus tech has the potential to leap far ahead of it. The “pixels” of a black phosphorus array could be 20 times smaller than those in LCDs, yet respond to inputs a million times faster.

Such speeds are not necessary for watching a movie or reading an article online, but they could revolutionize telecommunications, Atwater says. The fiber-optic cable through which light signals are sent in telecommunications devices can transmit only so many signals before they begin to interfere with and overwhelm each other, garbling them (picture trying to hear what a friend is saying in a crowded and loud bar). But a telecommunications device based on thin layers of black phosphorus could tune the polarization of each signal so that none interfere with each other. This would allow a fiber-optic cable to carry much more data than it does now.

Atwater says the technology could also open the door to a light-based replacement for Wi-Fi, something researchers in the field refer to as Li-Fi.

“Increasingly, we’re going to be looking at light-wave communications in free space,” he says. “Lighting like this very cool-looking lamp above my desk doesn’t carry any communication signal. It just provides light. But there’s no reason that you couldn’t sit in a future Starbucks and have your laptop taking a light signal for its wireless communication rather than a radio signal. It’s not quite here yet, but when it gets here, it will be at least a hundred times faster than Wi-Fi.”

The paper describing the work is titled, “Broadband electro-optic polarization conversion with atomically thin black phosphorus.” The lead author is Souvik Biswas, graduate student in applied physics. Other co-authors are Meir Y. Grajower, postdoctoral scholar research associate in applied physics and materials science, and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan.

“These are exciting times for new materials discovery that can shape the future of photonic devices, and we have barely scratched the surface,” Biswas says. “It would be gratifying if some day you could buy a commercial product constructed out of such atomically thin materials, and that day might not be very far.”

Funding for the research was provided by the U.S. Department of Energy; Japan’s Ministry of Education, Culture, Sports, Science and Technology; the Japan Society for the Promotion of Science; and the Japan Science and Technology Agency.

In a recent study published in Science Advances, Japanese researchers showed that a low protein diet can accelerate brain degeneration in mouse models of Alzheimer’s disease. More importantly, they found that Amino LP7 — a supplement containing seven specific amino acids — can slow down brain degeneration and dementia development in these animals. Their work expands on previous studies, which have demonstrated the effectiveness of Amino LP7 in improving cognitive function.

Dr. Makoto Higuchi from the National Institutes for Quantum Sciences and Technology, one of the lead scientists on the study, explains, “In older individuals, low protein diets are linked to poor maintenance of brain function. Amino acids are the building blocks of proteins. So, we wanted to understand whether supplementation with essential amino acids can protect the brains of older people from dementia, and if yes, what mechanisms would contribute to this protective effect.”

First, the researchers studied how a low protein diet affects the brain in mouse models of Alzheimer’s disease, which generally demonstrate neurodegeneration and abnormal protein aggregates called “Tau” aggregates in the brain. They found that mice consuming a low protein diet not only showed accelerated brain degeneration but also had signs of poor neuronal connectivity. Interestingly, these effects were reversed after supplementation with Amino LP7, indicating that the combination of seven specific amino acids could inhibit brain damage.

Next, the research team examined how Amino LP7 affects different signs of brain degeneration in the Alzheimer’s model. Untreated mice showed high levels of progressive brain degeneration, but Amino LP7 treatment suppressed neuronal death and thereby reduced brain degeneration, even though the Tau aggregates remained. According to Dr. Akihiko Kitamura, who also led this study, “Tau plaques in the brain are characteristic of Alzheimer’s and most treatments target them. However, we have shown that it is possible to overcome this Tau deposition and prevent brain atrophy via supplementation with Amino LP7.”

Next, to understand how Amino LP7 protects the brain, the researchers comprehensively analyzed the gene-level changes induced by Amino LP7. Their findings were quite encouraging. They observed that Amino LP7 reduces brain inflammation and also prevents kynurenine, an inflammation inducer, from entering the brain, thereby preventing inflammatory immune cells from attacking neurons. They also found that Amino LP7 reduces neuronal death and improves neuronal connectivity, improving brain function.

“These results suggest that essential amino acids can help maintain balance in the brain and prevent brain deterioration. Our study is the first to report that specific amino acids can hinder the development of dementia,” say Dr. Hideaki Sato and Dr. Yuhei Takado, both of whom majorly contributed to the study. “Although our study was performed in mice, it brings hope that amino acid intake could also modify the development of dementias in humans, including Alzheimer’s disease,” they add.

The study by this research group throws open several avenues for better understanding how dementias occur and how they can be prevented. Given that Amino LP7 improves brain function in older people without cognitive impairment, their findings suggest that it could also be effective in people with cognitive dysfunction.

Indeed, this patent-pending supplement could one day help millions worldwide live an improved, dementia-free life.