Daily Archives: April 4, 2023

Bio-inspired Nanocomposite Membranes for Osmotic Energy Harvesting: Joule

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Context & Scale

Osmotic energy is a renewable energy with zero emissions and minimal daily variations. However, the membranes for osmotic energy harvesting must have multiple properties that are thought to be impossible to realize to make this technology viable. Here, we show that cartilage-inspired cation-selective composite membrane assembled from aramid nanofibers and boron nitride nanosheets make it possible by a layer-by-layer assembly technology. The osmotic energy can be harvested by both salt concentration gradient and pressure-driven streaming because of the high mechanical and transport characteristics of the membranes. The combination of high strength, toughness, chemical resilience, rapid ion transport, and structural versatility of aramid-boron nitride composites makes it a promising candidate for osmotic energy harvesting under realistic operational conditions and life-cycle requirements.

Summary

Osmotic energy represents a widespread and reliable source of renewable energy with minimal daily variability. The key technological bottleneck for osmotic electricity is that membranes must combine highly efficient ion rectification and high ionic flux with long-term robustness in seawater. Here, we show that nanocomposite membranes with structural organization inspired by soft biological tissues with high mechanical and transport characteristics can address these problems. The layered membranes engineered with molecular-scale precision from aramid nanofibers and BN nanosheets simultaneously display high stiffness and tensile strength even when exposed to repeated pressure drops and salinity gradients. The total generated power density over large areas exceeded 0.6 W m−2 and was retained for as long as 20 cycles (200 h), demonstrating exceptional robustness. Furthermore, the membranes showed high performance in osmotic energy harvesting in unprecedentedly wide ranges of temperature (0°C–95°C) and pH (2.8–10.8) essential for the economic viability of osmotic energy generators.
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Source: Bio-inspired Nanocomposite Membranes for Osmotic Energy Harvesting: Joule

Double-slit experiment done using time instead of space

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The experiment relies on materials that can change their optical properties in fractions of a second, which could be used in new technologies or to explore fundamental questions in physics.

The original double-slit experiment, performed in 1801 by Thomas Young at the Royal Institution, showed that light acts as a wave. Further experiments, however, showed that light actually behaves as both a wave and as particles – revealing its quantum nature.

These experiments had a profound impact on quantum physics, revealing the dual particle and wave nature of not just light, but other ‘particles’ including electrons, neutrons, and whole atoms.

Now, a team led by Imperial College London physicists has performed the experiment using ‘slits’ in time rather than space. They achieved this by firing light through a material that changes its properties in femtoseconds (quadrillionths of a second), only allowing light to pass through at specific times in quick succession.

Lead researcher Professor Riccardo Sapienza, from the Department of Physics at Imperial, said: “Our experiment reveals more about the fundamental nature of light while serving as a stepping-stone to creating the ultimate materials that can minutely control light in both space and time.”

Details of the experiment are published today in Nature Physics.

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The material the team used was a thin film of indium-tin-oxide, which forms most mobile phone screens. The material had its reflectance changed by lasers on ultrafast timescales, creating the ‘slits’ for light. The material responded much quicker than the team expected to the laser control, varying its reflectivity in a few femtoseconds.

The material is a metamaterial – one that is engineered to have properties not found in nature. Such fine control of light is one of the promises of metamaterials, and when coupled with spatial control, could create new technologies and even analogues for studying fundamental physics phenomena like black holes.

Co-author Professor Sir John Pendry said: “The double time slits experiment opens the door to a whole new spectroscopy capable of resolving the temporal structure of a light pulse on the scale of one period of the radiation.”

The team next want to explore the phenomenon in a ‘time crystal’, which is analogous to an atomic crystal, but where the optical properties vary in time.

Co-author Professor Stefan Maier said: “The concept of time crystals has the potential to lead to ultrafast, parallelized optical switches.”

Source: Double-slit experiment that proved the wave n | EurekAlert!

ICE Is Grabbing Data From Schools, Abortion Clinics and news orgs with no judicial oversight

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US Immigration and Customs Enforcement agents are using an obscure legal tool to demand data from elementary schools, news organizations, and abortion clinics in ways that, some experts say, may be illegal.

While these administrative subpoenas, known as 1509 custom summonses, are meant to be used only in criminal investigations about illegal imports or unpaid customs duties, WIRED found that the agency has deployed them to seek records that seemingly have little or nothing to do with customs violations, according to legal experts and several recipients of the 1509 summonses.

A WIRED analysis of an Immigration and Customs Enforcement (ICE) subpoena tracking database, obtained through a Freedom of Information Act request, found that agents issued custom summons more than 170,000 times from the beginning of 2016 through mid-August 2022. The primary recipients of 1509s include telecommunications companies, major tech firms, money transfer services, airlines, and even utility companies. But it’s the edge cases that have drawn the most concern among legal experts,

The outlier cases include custom summonses that sought records from a youth soccer league in Texas; surveillance video from a major abortion provider in Illinois; student records from an elementary school in Georgia; health records from a major state university’s student health services; data from three boards of elections or election departments; and data from a Lutheran organization that provides refugees with humanitarian and housing support.

In at least two instances, agents at ICE used the custom summons to pressure news organizations to reveal information about their sources.

All of this is done without judicial oversight.

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The 1509 customs summons is an administrative subpoena explicitly and exclusively meant for use in investigations of illegal imports or unpaid customs duties under a law known as Title 19 US Code 1509. Its goal is to provide agencies like ICE with a way to obtain business records from companies without having to go to a judge for a warrant.

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Without access to the underlying subpoenas ICE issued in each use of a 1509, it’s difficult to know exactly why companies in the database were issued customs summonses. However, nearly everyone we spoke to was concerned about the types of organizations that received these summonses. Our investigation found that ICE issued scores of customs summonses to hospitals and hundreds to elementary schools, high schools, and universities. “It’s disturbing,” Mao says. “I really can’t imagine how a student or a health record could possibly be relevant to a permissible customs investigation under the law.”

To figure out if these summonses were issued for customs investigations, we contacted 30 organizations that received them. Most did not respond, and many who did refused to speak on the record for fear of retaliation.

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In March last year, US senator Ron Wyden, an Oregon Democrat who chairs the Senate Finance Committee, revealed that ICE had been using 1509 customs summonses to obtain millions of money transfer records, which were added to a database that was shared with hundreds of law enforcement agencies across the country. According to the American Civil Liberties Union (ACLU), it was one of the largest government surveillance programs in recent memory.

Immediately after Wyden’s investigation, the number of customs summons issued by ICE fell from 3,683 in March 2022 to 1,650 by the end of August, according to the records WIRED obtained.

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Source: ICE Is Grabbing Data From Schools and Abortion Clinics | WIRED