A breakthrough cure for blindness may have been reached after a study on mice showed that vision loss can be treated with a chemical injection to the eye. Experts hope that further experiments will lead to a treatment for humans. The chemical, which temporarily restores partial vision in blind mice, was discovered by a research team at the University of California, Berkeley, in association with the University of Munich and Seattle’s University of Washington. The substance, known as acrylamide-azobenzene-quaternary ammonium (AAQ), makes cells in the retina, the light-sensitive membrane in the back of the eye, more receptive. The rodents used in the experiment had congenital mutations that made the light-sensitive cells (rods and cones) inside their eyes wither within months after birth. Injections of AAQ into their eyes briefly restored their ability to see light. This approach "offers real hope to patients with retinal degeneration," study co-author Dr. Russell Van Gelder of the University of Washington in Seattle said in a press release. "We still need to show that these compounds are safe and will work in people the way they work in mice, but these results demonstrate that this class of compound restores light sensitivity to retinas blind from genetic disease." If this new approach is successful, it could be used to treat retinitis pigmentosa, the most common inherited mode of blindness, and age-related macular degeneration, the most common cause of acquired blindness in underdeveloped nations. In both cases, the retina’s rods and cones die, rendering the eye blind from a lack of photoreceptors. The AAQ remedy only lasts for about 24 hours, but scientists are set to conduct further research with more sophisticated versions of the compound. “The advantage of this approach is that it is a simple chemical, which means that you can change the dosage, you can use it in combination with other therapies, or you can discontinue the therapy if you don't like the results,” says Richard Kramer, a professor of molecular and cell biology at the University of California, Berkeley, to the school’s newspaper. “As improved chemicals become available, you could offer them to patients. You can't do that when you surgically implant a chip or after you genetically modify somebody.” Source: Sam Daily Times
Injection helps blind mice see: Humans next?
A breakthrough cure for blindness may have been reached after a study on mice showed that vision loss can be treated with a chemical injection to the eye. Experts hope that further experiments will lead to a treatment for humans. The chemical, which temporarily restores partial vision in blind mice, was discovered by a research team at the University of California, Berkeley, in association with the University of Munich and Seattle’s University of Washington. The substance, known as acrylamide-azobenzene-quaternary ammonium (AAQ), makes cells in the retina, the light-sensitive membrane in the back of the eye, more receptive. The rodents used in the experiment had congenital mutations that made the light-sensitive cells (rods and cones) inside their eyes wither within months after birth. Injections of AAQ into their eyes briefly restored their ability to see light. This approach "offers real hope to patients with retinal degeneration," study co-author Dr. Russell Van Gelder of the University of Washington in Seattle said in a press release. "We still need to show that these compounds are safe and will work in people the way they work in mice, but these results demonstrate that this class of compound restores light sensitivity to retinas blind from genetic disease." If this new approach is successful, it could be used to treat retinitis pigmentosa, the most common inherited mode of blindness, and age-related macular degeneration, the most common cause of acquired blindness in underdeveloped nations. In both cases, the retina’s rods and cones die, rendering the eye blind from a lack of photoreceptors. The AAQ remedy only lasts for about 24 hours, but scientists are set to conduct further research with more sophisticated versions of the compound. “The advantage of this approach is that it is a simple chemical, which means that you can change the dosage, you can use it in combination with other therapies, or you can discontinue the therapy if you don't like the results,” says Richard Kramer, a professor of molecular and cell biology at the University of California, Berkeley, to the school’s newspaper. “As improved chemicals become available, you could offer them to patients. You can't do that when you surgically implant a chip or after you genetically modify somebody.” Source: Sam Daily Times
Flexible, Light Solar Cells Of Graphene Could Provide New Opportunities
Illustration courtesy of the research team
MIT researchers develop a new approach using graphene sheets coated with nanowires. MIT researchers have produced a new kind of photovoltaic cell based on sheets of flexible graphene coated with a layer of nanowires. The approach could lead to low-cost, transparent and flexible solar cells that could be deployed on windows, roofs or other surfaces. The new approach is detailed in a report published in the journal Nano Letters, co-authored by MIT postdocs Hyesung Park and Sehoon Chang, associate professor of materials science and engineering Silvija Gradečak, and eight other MIT researchers. Illustration shows the layered structure of the new device, starting with a flexible layer of graphene, a one-atom-thick carbon material. A layer of polymer is bonded to that, and then a layer of zinc-oxide nano wires (shown in magenta), and finally a layer of a material that can extract energy from sunlight, such as quantum dots or a polymer-based material. While most of today’s solar cells are made of silicon, these remain expensive because the silicon is generally highly purified and then made into crystals that are sliced thin. Many researchers are exploring alternatives, such as nanostructured or hybrid solar cells; indium tin oxide (ITO) is used as a transparent electrode in these new solar cells. “Currently, ITO is the material of choice for transparent electrodes,” Gradečak says, such as in the touch screens now used on smartphones. But the indium used in that compound is expensive, while graphene is made from ubiquitous carbon. The new material, Gradečak says, may be an alternative to ITO. In addition to its lower cost, it provides other advantages, including flexibility, low weight, mechanical strength and chemical robustness. Building semiconducting nanostructures directly on a pristine graphene surface without impairing its electrical and structural properties has been challenging due to graphene’s stable and inert structure, Gradečak explains. So her team used a series of polymer coatings to modify its properties, allowing them to bond a layer of zinc oxide nanowires to it, and then an overlay of a material that responds to light waves — either lead-sulfide quantum dots or a type of polymer called P3HT. Despite these modifications, Gradečak says, graphene’s innate properties remain intact, providing significant advantages in the resulting hybrid material. “We’ve demonstrated that devices based on graphene have a comparable efficiency to ITO,” she says — in the case of the quantum-dot overlay, an overall power conversion efficiency of 4.2 percent — less than the efficiency of general purpose silicon cells, but competitive for specialized applications. “We’re the first to demonstrate graphene-nanowire solar cells without sacrificing device performance.” In addition, unlike the high-temperature growth of other semiconductors, a solution-based process to deposit zinc oxide nanowires on graphene electrodes can be done entirely at temperatures below 175 degrees Celsius, says Chang, a postdoc in MIT’s Department of Materials Science and Engineering (DMSE) and a lead author of the paper. Silicon solar cells are typically processed at significantly higher temperatures. The manufacturing process is highly scalable, adds Park, the other lead author and a postdoc in DMSE and in MIT’s Department of Electrical Engineering and Computer Science. The graphene is synthesized through a process called chemical vapor deposition and then coated with the polymer layers. “The size is not a limiting factor, and graphene can be transferred onto various target substrates such as glass or plastic,” Park says. Gradečak cautions that while the scalability for solar cells hasn’t been demonstrated yet — she and her colleagues have only made proof-of-concept devices a half-inch in size — she doesn’t foresee any obstacles to making larger sizes. “I believe within a couple of years we could see [commercial] devices” based on this technology, she says. László Forró, a professor at the Ecole Polytechnique Fédérale de Lausanne, in Switzerland, who was not associated with this research, says that the idea of using graphene as a transparent electrode was “in the air already,” but had not actually been realized. “In my opinion this work is a real breakthrough,” Forró says. “Excellent work in every respect.” He cautions that “the road is still long to get into real applications, there are many problems to be solved,” but adds that “the quality of the research team around this project … guarantees the success.” The work also involved MIT professors Moungi Bawendi, Mildred Dresselhaus, Vladimir Bulovic and Jing Kong; graduate students Joel Jean and Jayce Cheng; postdoc Paulo Araujo; and affiliate Mingsheng Wang. It was supported by the Eni-MIT Alliance Solar Frontiers Program, and used facilities provided by the MIT Center for Materials Science Engineering, which is supported by the National Science Foundation. Contacts: David L. Chandler, MIT News Office, Source: Nano-Patents-Innovations
Underground nuclear tests are hard to detect. A new method can spot them 99% of the time
Since the first detonation of an atomic bomb in 1945, more than 2,000 nuclear weapons tests have been conducted by eight countries: the United States, the Soviet Union, the United Kingdom, France, China, India, Pakistan and North Korea.
Groups such as the Comprehensive Nuclear-Test-Ban Treaty Organization are constantly on the lookout for new tests. However, for reasons of safety and secrecy, modern nuclear tests are carried out underground – which makes them difficult to detect. Often, the only indication they have occurred is from the seismic waves they generate.
In a paper published in Geophysical Journal International, my colleagues and I have developed a way to distinguish between underground nuclear tests and natural earthquakes with around 99% accuracy.
Fallout
The invention of nuclear weapons sparked an international arms race, as the Soviet Union, the UK and France developed and tested increasingly larger and more sophisticated devices in an attempt to keep up with the US.
Many early tests caused serious environmental and societal damage. For example, the US’s 1954 Castle Bravo test, conducted in secret at Bikini Atoll in the Marshall Islands, delivered large volumes of radioactive fallout to several nearby islands and their inhabitants.
Between 1952 and 1957, the UK conducted several tests in Australia, scattering long-lived radioactive material over wide areas of South Australian bushland, with devastating consequences for local Indigenous communities.
In 1963, the US, the UK and the USSR agreed to carry out future tests underground to limit fallout. Nevertheless, testing continued unabated as China, India, Pakistan and North Korea also entered the fray over the following decades.
How to spot an atom bomb
During this period there were substantial international efforts to figure out how to monitor nuclear testing. The competitive nature of weapons development means much research and testing is conducted in secret.
Groups such as the Comprehensive Nuclear-Test-Ban Treaty Organization today run global networks of instruments specifically designed to identify any potential tests. These include:
- air-testing stations to detect minute quantities of radioactive elements in the atmosphere
- aquatic listening posts to hear underwater tests
- infrasound detectors to catch the low-frequency booms and rumbles of explosions in the atmosphere
- seismometers to record the shaking of Earth caused by underground tests.
A needle in a haystack
Seismometers are designed to measure seismic waves: tiny vibrations of the ground surface generated when large amounts of energy are suddenly released underground, such as during earthquakes or nuclear explosions.
There are two main kinds of seismic waves. First are body waves, which travel outwards in all directions, including down into the deep Earth, before returning to the surface. Second are surface waves, which travel along Earth’s surface like ripples spreading out on a pond.
The difficulty in using seismic waves to monitor underground nuclear tests is distinguishing between explosions and naturally occurring earthquakes. A core goal of monitoring is never to miss an explosion, but there are thousands of sizeable natural quakes around the world every day.
As a result, monitoring underground tests is like searching for a potentially non-existent needle in a haystack the size of a planet.
Nukes vs quakes
Many different methods have been developed to aid this search over the past 60 years.
Some of the simplest include analysing the location or depth of the source. If an event occurs far from volcanoes and plate tectonic boundaries, it might be considered more suspicious. Alternatively, if it occurs at a depth greater than say three kilometres, it is unlikely to have been a nuclear test.
However, these simple methods are not foolproof. Tests might be carried out in earthquake-prone areas for camouflage, for example, and shallow earthquakes are also possible.
A more sophisticated monitoring approach involves calculating the ratio of the amount of the energy transmitted in body waves to the amount carried in surface waves. Earthquakes tend to expend more of their energy in surface waves than explosions do.
This method has proven highly effective for identifying underground nuclear tests, but it too is imperfect. It failed to effectively classify the 2017 North Korean nuclear test, which generated substantial surface waves because it was carried out inside a tunnel in a mountain.
This outcome underlines the importance of using multiple independent discrimination techniques during monitoring – no single method is likely to prove reliable for all events.
An alternative method
In 2023, my colleagues and I from the Australian National University and Los Alamos National Laboratory in the US got together to re-examine the problem of determining the source of seismic waves.
We used a recently developed approach to represent how rocks are displaced at the source of a seismic event, and combined it with a more advanced statistical model to describe different types of event. As a result, we were able to take advantage of fundamental differences between the sources of explosions and earthquakes to develop an improved method of classifying these events.
We tested our approach on catalogues of known explosions and earthquakes from the western United States, and found that the method gets it right around 99% of the time. This makes it a useful new tool in efforts to monitor underground nuclear tests.
Robust techniques for identification of nuclear tests will continue to be a key component of global monitoring programs. They are critical for ensuring governments are held accountable for the environmental and societal impacts of nuclear weapons testing.
Mark Hoggard, DECRA Research Fellow, Australian National University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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