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Science, 19 APR 2024, VOL 384, ISSUE 6693

Science, April 19, 2024, Vol. 384, No. 6693

Astronomy

Dating the Solar System’s giant planet orbital instability using enstatite meteorites

Determination of periods of instability in the orbits of giant planets in the solar system using enstative meteorites

▲ 作者:CHRYSA AVDELLIDOU, MARCO DELBO', DAVID NESVORNÝ, KEVIN J. WALSH & ALESSANDRO MORBIDELLI

▲ Links:

https://www.science.org/doi/10.1126/science.adg8092

▲ Abstract:

The giant planets of the solar system originally formed in compact orbits, transitioning to their current wider structures due to unstable orbits. The timing of such instability is difficult to determine.

The team used dynamic simulations to demonstrate orbital instability, implanting star fragments in the terrestrial planetary region into the asteroid's main belt. Using meteorite data, the implantation occurred more than 60 million years after the birth of the solar system.

Combining this constraint with a previous upper limit from Jupiter's Trojan asteroid, the team concluded that orbital instability occurred between 60 million and 100 million years after the birth of the solar system. The great impact that formed the Moon occurred during this period, so it may be related to the instability of the giant planets.

▲ Abstract：

The giant planets of the Solar System formed on initially compact orbits, which transitioned to the current wider configuration by means of an orbital instability. The timing of that instability is poorly constrained. In this work, we use dynamical simulations to demonstrate that the instability implanted planetesimal fragments from the terrestrial planet region into the asteroid main belt. We use meteorite data to show that the implantation occurred >60 million years (Myr) after the Solar System began to form. Combining this constraint with a previous upper limit derived from Jupiter’s trojan asteroids, we conclude that the orbital instability occurred 60 to 100 Myr after the beginning of Solar System formation. The giant impact that formed the Moon occurred within this range, so it might be related to the giant planet instability.

材料科学Materials Science

Structural disorder determines capacitance in nanoporous carbons

The structural disorder determines the capacitance of nanoporous carbon

▲ 作者：XINYU LIU, DONGXUN LYU, CÉLINE MERLET, MATTHEW J. A. LEESMITH, XIAO HUA, ZHEN XU, ET AL.

▲ Links:

https://www.science.org/doi/10.1126/science.adn6242

▲ Abstract:

The difficulty in characterizing the complex structure of nanoporous carbon electrodes has led to a lack of clear design principles to improve supercapacitors. Aperture size has always been considered the main lever for increasing capacitance.

However, the research group's evaluation of large quantities of commercial nanoporous carbon found a lack of correlation between pore size and capacitance. In contrast, NMR spectroscopy measurements and simulations reveal a strong correlation between electrode structure disorder and capacitance.

Disordered carbons with smaller graphene-like domains exhibit higher capacitance because they store ions more efficiently in their nanopores. This discovery proposes a way to understand and utilize disorder to achieve high energy density supercapacitors.

▲ Abstract：

The difficulty in characterizing the complex structures of nanoporous carbon electrodes has led to a lack of clear design principles with which to improve supercapacitors. Pore size has long been considered the main lever to improve capacitance. However, our evaluation of a large series of commercial nanoporous carbons finds a lack of correlation between pore size and capacitance. Instead, nuclear magnetic resonance spectroscopy measurements and simulations reveal a strong correlation between structural disorder in the electrodes and capacitance. More disordered carbons with smaller graphene-like domains show higher capacitances owing to the more efficient storage of ions in their nanopores. Our findings suggest ways to understand and exploit disorder to achieve highly energy-dense supercapacitors.

High energy density in artificial heterostructures through relaxation time modulation

High energy density of artificial heterostructures is achieved by relaxation time modulation

▲作者:SANGMOON HAN, JUSTIN S. KIM, EUGENE PARK, YUAN MENG, ZHIHAO XU, ALEXANDRE C. FOUCHER, ET AL.

▲ Links:

https://www.science.org/doi/10.1126/science.adl2835

▲ Abstract:

Electrostatic capacitors are the cornerstone of advanced electronics and high-power electrical systems due to their ultra-fast charge/discharge capabilities. Ferroelectric materials have a high maximum polarization, but the high residual polarization hinders their effective deployment in energy storage applications. The previous method had encountered a bottleneck due to the degradation of the crystallinity of ferroelectric materials.

The research group introduced a method to control the relaxation time using two-dimensional (2D) materials while minimizing energy loss and maintaining the crystallinity of ferroelectric 3D materials by using 2D/3D/2D heterostructures. An energy density of 191.7 J/cm3 can be achieved with an efficiency of more than 90% using this method.

This precise control of relaxation time is expected to facilitate widespread adoption and has the potential to accelerate the development of efficient energy storage systems.

▲ Abstract：

Electrostatic capacitors are foundational components of advanced electronics and high-power electrical systems owing to their ultrafast charging-discharging capability. Ferroelectric materials offer high maximum polarization, but high remnant polarization has hindered their effective deployment in energy storage applications. Previous methodologies have encountered problems because of the deteriorated crystallinity of the ferroelectric materials. We introduce an approach to control the relaxation time using two-dimensional (2D) materials while minimizing energy loss by using 2D/3D/2D heterostructures and preserving the crystallinity of ferroelectric 3D materials. Using this approach, we were able to achieve an energy density of 191.7 joules per cubic centimeter with an efficiency greater than 90%. This precise control over relaxation time holds promise for a wide array of applications and has the potential to accelerate the development of highly efficient energy storage systems.

More resilient polyester membranes for high-performance reverse osmosis desalination

More resilient polyester membranes enable high-performance reverse osmosis desalination

▲ 作者：YUJIAN YAO, PINGXIA ZHANG, FEI SUN, WEN ZHANG, MENG LI, GANG SHA, ET AL.

▲ Links:

https://www.science.org/doi/10.1126/science.adk0632

▲ Abstract:

For nearly half a century, membrane composite reverse osmosis membranes have been the gold standard technology for desalination and water purification. Polyamide membranes have excellent water permeability and salt repellency, but they also have the disadvantages of poor chlorine resistance, high fouling tendency and low boron rejection.

The research group solved these problems by molecularly designing a polyester membrane composite reverse osmosis membrane by using a co-solvent-assisted interfacial polymerization method to react 3,5-dihydroxy-4-methylbenzoic acid with trimelliptyl tricarboxyl chloride. This polyester film has excellent water permeability, high rejection of sodium chloride and boron, and is completely chlorine resistant.

The membrane's ultra-smooth, low-energy surface also prevents fouling and mineral fouling compared to polyamide membranes. By further optimizing water-salt selectivity, the membrane is expected to surpass polyamide membranes and provide a new avenue to greatly reduce the pretreatment step of desalination.

▲ Abstract：

Thin-film composite reverse osmosis membranes have remained the gold standard technology for desalination and water purification for nearly half a century. Polyamide films offer excellent water permeability and salt rejection but also suffer from poor chlorine resistance, high fouling propensity, and low boron rejection. We addressed these issues by molecularly designing a polyester thin-film composite reverse osmosis membrane using co-solvent–assisted interfacial polymerization to react 3,5-dihydroxy-4-methylbenzoic acid with trimesoyl chloride. This polyester membrane exhibits substantial water permeability, high rejection for sodium chloride and boron, and complete resistance toward chlorine. The ultrasmooth, low-energy surface of the membrane also prevents fouling and mineral scaling compared with polyamide membranes. These membranes could increasingly challenge polyamide membranes by further optimizing water-salt selectivity, offering a path to considerably reducing pretreatment steps in desalination.

人工智能Artificial Intelligence

Fusion of memristor and digital compute-in-memory processing for energy-efficient edge computing

Convergence of memristor and digital in-memory computing processing for efficient edge computing

▲作者:TAI-HAO WEN, JE-MIN HUNG, WEI-HSING HUANG, CHUAN-JIA JHANG, YUN-CHEN LO, HUNG-HSI HSU, ET AL.

▲ Links:

https://www.science.org/doi/10.1126/science.adf5538

▲ Abstract:

Artificial intelligence (AI) edge devices are more likely to employ high-capacity non-volatile in-memory computing (CIM) to achieve high energy efficiency and fast wake-up responses that are accurate enough. Most of the previous work was either based on memristor based CIM that suffered a loss of accuracy due to its limited durability and did not support training, or a CIM based on digital static random access memory (SRAM) but limited by large manufacturing needs and volatile storage.

The research group reported an AI edge processor using a memristor-SRAM CIM fusion scheme that can take advantage of the high accuracy of digital SRAM CIM and the high power efficiency and memory density of resistive random access memory memristor CIM. This also enables adaptive local training to adapt to individual features and user environments.

The converged processor achieves high CIM capacity, short wake-up latency (392 microseconds), high peak efficiency (77.64 TOPS/W), and robust accuracy (accuracy loss<0.5%). This work demonstrates that memristor technology has moved beyond the laboratory development stage and is now manufacturable for AI edge processors.

▲ Abstract：

Artificial intelligence (AI) edge devices prefer employing high-capacity nonvolatile compute-in-memory (CIM) to achieve high energy efficiency and rapid wakeup-to-response with sufficient accuracy. Most previous works are based on either memristor-based CIMs, which suffer from accuracy loss and do not support training as a result of limited endurance, or digital static random-access memory (SRAM)–based CIMs, which suffer from large area requirements and volatile storage. We report an AI edge processor that uses a memristor-SRAM CIM-fusion scheme to simultaneously exploit the high accuracy of the digital SRAM CIM and the high energy-efficiency and storage density of the resistive random-access memory memristor CIM. This also enables adaptive local training to accommodate personalized characterization and user environment. The fusion processor achieved high CIM capacity, short wakeup-to-response latency (392 microseconds), high peak energy efficiency (77.64 teraoperations per second per watt), and robust accuracy (<0.5% accuracy loss). This work demonstrates that memristor technology has moved beyond in-lab development stages and now has manufacturability for AI edge processors.

地球科学Earth Science

A national-scale assessment of land subsidence in China’s major cities

A nationwide assessment of land subsidence in major cities in China

▲ 作者:ZURUI AO, XIAOMEI HU, SHENGLI TAO, XIE HU, GUOQUAN WANG, MINGJIA LI, ET AL.

▲ Links:

https://www.science.org/doi/10.1126/science.adl4366

▲ Abstract:

China's massive urbanization wave could be threatened by land subsidence.

Using spaceborne interferometric synthetic aperture radar (SAR) measurement technology, the research group conducted a systematic assessment of land subsidence in major cities in China from 2015 to 2022. Of the surveyed urban land, 45% of the land is subsidencing at a rate of more than 3 mm per year, and 16% is subsidencing at a rate of more than 10 mm per year, affecting 29% and 7% of the urban population, respectively.

Subsidence appears to be related to a range of factors, including groundwater pumping and building weight. By 2120, due to the combined impact of urban subsidence and sea level rise, 22%~26% of China's coastal land will have a relative altitude below sea level, accounting for 9%~11% of the coastal population.

The results of the study highlight the need for enhanced protection measures to mitigate potential damage caused by subsidence.

▲ Abstract：

China’s massive wave of urbanization may be threatened by land subsidence. Using a spaceborne synthetic aperture radar interferometry technique, we provided a systematic assessment of land subsidence in all of China’s major cities from 2015 to 2022. Of the examined urban lands, 45% are subsiding faster than 3 millimeters per year, and 16% are subsiding faster than 10 millimeters per year, affecting 29 and 7% of the urban population, respectively. The subsidence appears to be associated with a range of factors such as groundwater withdrawal and the weight of buildings. By 2120, 22 to 26% of China’s coastal lands will have a relative elevation lower than sea level, hosting 9 to 11% of the coastal population, because of the combined effect of city subsidence and sea-level rise. Our results underscore the necessity of enhancing protective measures to mitigate potential damages from subsidence.