Silver nanowire sensors ease long-term EKG monitoring
Researchers from N.C. State University have developed a new, wearable sensor that uses silver nanowires to monitor electrophysiological signals, such as electrocardiography (EKG) or electromyography (EMG). Their sensor is as accurate as “wet electrode” sensors used in hospitals but can be used for long-term monitoring and is more accurate than existing sensors when a patient is moving.
Wet electrode sensors rely on an electrolytic gel between the sensor and the patient’s skin to improve the sensor’s ability to pick up the body’s electrical signals. However, this technology poses problems for long-term monitoring, because the gel dries – irritating the patient’s skin and making the sensor less accurate.
The new nanowire sensor is comparable to the wet sensors in terms of signal quality but is a “dry” electrode: It doesn’t use a gel layer.
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Yong Zhu, an associate professor of mechanical and aerospace engineering at N.C. State, is senior author of a paper published in RSC Advances that describes the work. “In addition,” Zhu said, “our electrode is mechanically robust, because the nanowires are inlaid in the polymer.” ncsu.edu
1 algae species could be used to make 2 biofuels
A common algae commercially grown to make fish food holds promise as a source for both biodiesel and jet fuel, according to a study published in the journal Energy & Fuels.
The researchers, led by Greg O’Neil of Western Washington University and Chris Reddy of Woods Hole Oceanographic Institution, exploited an unusual and untapped class of chemical compounds in the algae to synthesize two different fuel products, in parallel, from a single algae.
Algae contain fatty acids that can be converted into fatty acid methyl esters, the molecules in biodiesel. For their study, the researchers targeted a specific algal species – Isochrysis – because growers have already demonstrated they can produce it in large batches to make fish food. Also, it is among only a handful of algal species around the globe that produce fats called alkenones – compounds the researchers believe have potential as a fuel source. whoi.edu
Long drought periods likely doomed ancient Mexican city
Archaeologists continue to debate the reasons for the collapse of cities and states in pre-Columbian Central America, and climate change is considered one of the major causes.
A study by a team from the University of California, Berkeley, provides evidence that a prolonged period of below-average rainfall was partly responsible for the abandonment of one such city, Cantona, between AD 900 and AD 1050.
At its peak, Cantona, located in a dry, volcanic basin east of today’s Mexico City, was one of the largest cities in the New World, with 90,000 inhabitants.
UC Berkeley geographers analyzed sediment cores from a lake 20 miles south of the site of Cantona. They found evidence of a 650-year period of frequent droughts that were part of a long-term drying trend in highland Mexico. The climate became wetter again around AD 1300, just prior to the rise of the Aztec empire.
“The decline of Cantona occurred during this dry interval, and we conclude that climate change probably played a role, at least towards the end of the city’s existence,” said lead author Tripti Bhattacharya, a UC Berkeley graduate student. The findings are published in the journal Proceedings of the National Academy of Sciences. berkeley.edu