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Category: nanotechnology – Page 178

The torsion balance contains a rigid balance beam suspended by a fine thread as an ancient scientific instrument that continues to form a very sensitive force sensor to date. The force sensitivity is proportional to the lengths of the beam and thread and inversely proportional to the fourth power of the diameter of the thread; therefore, nanomaterials that support the torsion balances should be ideal building blocks. In a new report now published on Science Advances, Lin Cong and a research team in quantum physics, microelectronics and nanomaterials in China have detailed a torsional balance array on a chip with the highest sensitivity level. The team facilitated this by using a carbon nanotube as the thread and a monolayer graphene coated with aluminum films as the beam and mirror. Using the experimental setup, Cong et al. measured the femtonewton force exerted by a weak laser. The balances on the chip served as an ideal platform to investigate fundamental interactions up to zeptonewton in accuracy.

A modern role for ancient scientific instruments

The torsion pendulum is an ancient scientific instrument used to discover Coulomb’s law in 1785 and to determine the density of Earth in 1798. The instrument is useful across a range of applications including existing scientific explorations of precisely determining the gravitational constant. The most efficient method to achieve high sensitivity in the setup is by reducing the diameter of the suspension thread as much as possible. For instance, in 1931, Kappler et al. used a centimeters-long thread to develop a highly sensitive torsion balance to set a record for a hitherto unattained intrinsic force sensitivity. At present, carbon nanotubes form one of the strongest and thinnest materials known. In this work, the team synthesized ultra-long carbon nanotubes (CNTs) and large-area graphene to substantially increase the lengths of the balance beam and suspension thread to significantly improve the sensitivity of the instrument.

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Should interest those into links on aging/longevity and neuroscience.

The mammalian center for learning and memory, hippocampus, has a remarkable capacity to generate new neurons throughout life. Newborn neurons are produced by neural stem cells (NSCs) and they are crucial for forming neural circuits required for learning and memory, and mood control. During aging, the number of NSCs declines, leading to decreased neurogenesis and age-associated cognitive decline, anxiety, and depression. Thus, identifying the core molecular machinery responsible for NSC preservation is of fundamental importance if we are to use neurogenesis to halt or reverse hippocampal age-related pathology.

While there are increasing number of tools available to study NSCs and neurogenesis in mouse models, one of the major hurdles in exploring this fundamental biological process in the human brain is the lack of specific NSCs markers amenable for advanced imaging and in vivo analysis. A team of researchers led by Dr. Mirjana Maletić-Savatić, associate professor at Baylor College of Medicine and investigator at the Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, and Dr. Louis Manganas, associate professor at the Stony Brook University, decided to tackle this problem in a rather unusual way. They reasoned that if they could find proteins that are present on the surface of NSCs, then they could eventually make agents to “see” NSCs in the .

“The ultimate goal of our research is to maintain neurogenesis throughout life at the same level as it is in the young brains, to prevent the decline in our cognitive capabilities and reduce the tendency towards mood disorders such as depression, as we age. To do that, however, we first need to better understand this elusive, yet fundamental process in humans. However, we do not have the tools to study this process in live humans and all the knowledge we have gathered so far comes from analyses of the postmortem brains. And we cannot develop tools to detect this process in people because existing NSC markers are present within cells and unreachable for in vivo visualization,” Maletić-Savatić said. “So, in collaboration with our colleagues from New York and Spain, we undertook this study to find surface markers and then develop tools such as ligands for positron emission tomography (PET) to visualize them using advanced real-time in vivo brain imaging.”

Continue reading “A novel marker of adult human neural stem cells discovered” | >

Circa 2013

One of the greatest aspirations of the human mind has been to realize machines that surpass its cognitive intelligence. The rapid expansion in computing power, about to exceed the equivalent of the human brain, has yet to produce such a machine. The article by Neftci et al. in PNAS (1) offers a refreshing and humbling reminder that the brain’s cognition does not arise from exacting digital precision in high-performance computing, but rather emerges from an extremely efficient and resilient collective form of computation extending over very large ensembles of sluggish, imprecise, and unreliable analog components. This observation, first made by John von Neumann in his final opus (2), continues to challenge scientists and engineers several decades later in figuring and reproducing the mechanisms underlying brain-like forms of cognitive computing.

Related developments are currently unfolding in collaborative initiatives engaging scientists and engineers, on a grander scale, in advancing neuroscience toward understanding the brain. In parallel with the Human Brain Project in Europe, the Brain Research through Advancing Innovative Neurotechnologies Initiative promises groundbreaking advances in enabling tools for revolutionizing neuroscience by developing nanotechnology to probe brain function at greatly increased spatial and temporal detail. Engineers are poised to contribute even further in revolutionizing such developments in neuroscience. In this regard it is helpful to relate the inquisitive nature of science—analysis—to the constructive power of engineering, synthesis.

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When optimizing catalysis in the lab, product selectivity and conversion efficiency are primary goals for materials scientists. Efficiency and selectivity are often mutually antagonistic, where high selectivity is accompanied by low efficiency and vice versa. Increasing the temperature can also change the reaction pathway. In a new report, Chao Zhan and a team of scientists in chemistry and chemical engineering at the Xiamen University in China and the University of California, Santa Barbara, U.S., constructed hierarchical plasmonic nanoreactors to show nonconfined thermal fields and electrons. The combined attributes uniquely coexisted in plasmonic nanostructures. The team regulated parallel reaction pathways for propylene partial oxidation and selectively produced acrolein during the experiments to form products that are different from thermal catalysis. The work described a strategy to optimize chemical processes and achieve high yields with high selectivity at lower temperature under visible light illumination. The work is now published on Science Advances.

Catalysts

Ideal catalytic processes can produce desired target products without undesirable side effects under cost-effective conditions, although such conditions are rarely achieved in practice. For instance, high efficiency and high selectivity are antagonistic goals, where a relatively high temperature is often necessary to overcome the large barrier of oxygen activation to achieve high reactant conversion. Increasing the functional temperature can also lead to overoxidized and therefore additional byproducts. As a result, researchers must compromise between selectivity and efficiency. For instance, a given molecule typically requires diverse catalysts to generate different products, where each catalyst has different efficiency and selectivity. To circumvent any limitations, they can use surface plasmons (SPs) to redistribute photons, electrons and heat energy in space and time.

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Researchers at the University of Ottawa have debunked the decade-old myth of metals being useless in photonics – the science and technology of light – with their findings, recently published in Nature Communications, expected to lead to many applications in the field of nanophotonics.

“We broke the record for the resonance quality factor (Q-factor) of a periodic array of metal nanoparticles by one order of magnitude compared to previous reports,” said senior author Dr. Ksenia Dolgaleva, Canada Research Chair in Integrated Photonics (Tier 2) and Associate Professor in the School of Electrical Engineering and Computer Science (EECS) at the University of Ottawa.

“It is a well-known fact that metals are very lossy when they interact with light, which means they cause the dissipation of electrical energy. The high losses compromise their use in optics and photonics. We demonstrated ultra-high-Q resonances in a metasurface (an artificially structured surface) comprised of an array of metal nanoparticles embedded inside a flat glass substrate. These resonances can be used for efficient light manipulating and enhanced light-matter interaction, showing metals are useful in photonics.”

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A new, simpler solution process for fabricating stable perovskite solar cells overcomes the key bottleneck to large-scale production and commercialization of this promising renewable-energy technology, which has remained tantalizingly out of reach for more than a decade.

“Our work paves the way for low-cost, high-throughput commercial-scale production of large-scale solar modules in the near future,” said Wanyi Nie, a research scientist fellow in the Center of Integrated Nanotechnologies at Los Alamos National Laboratory and corresponding author of the paper, which was published today in the journal Joule. “We were able to demonstrate the approach through two mini-modules that reached champion levels of converting sunlight to power with greatly extended operational lifetimes. Since this process is facile and low cost, we believe it can be easily adapted to scalable fabrication in industrial settings.”

The team invented a one-step spin coating method using sulfolane, a liquid solvent. The new process allowed the team, a collaboration among Los Alamos and researchers from National Taiwan University (NTU), to produce high-yield, large-area photovoltaic devices that are highly efficient in creating power from sunlight. These perovskite also have a long operational lifetime.

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Researchers at the University of Ottawa have debunked the decade-old myth of metals being useless in photonics—the science and technology of light—with their findings, recently published in Nature Communications, expected to lead to many applications in the field of nanophotonics.

“We broke the record for the resonance quality factor (Q-factor) of a periodic array of by one order of magnitude compared to previous reports,” said senior author Dr. Ksenia Dolgaleva, Canada Research Chair in Integrated Photonics (Tier 2) and Associate Professor in the School of Electrical Engineering and Computer Science (EECS) at the University of Ottawa.

“It is a well-known fact that metals are very lossy when they interact with light, which means they cause the dissipation of electrical energy. The high losses compromise their use in optics and photonics. We demonstrated ultra-high-Q resonances in a metasurface (an artificially structured surface) comprised of an array of metal nanoparticles embedded inside a flat glass substrate. These resonances can be used for efficient light manipulating and enhanced light-matter interaction, showing metals are useful in photonics.”

Read more | >

If you want to build a fully functional nanosized robot, you need to incorporate a host of capabilities, from complicated electronic circuits and photovoltaics to sensors and antennas.

But just as importantly, if you want your robot to move, you need it to be able to bend.

Cornell researchers have created micron-sized shape memory actuators that enable atomically thin two-dimensional materials to fold themselves into 3D configurations. All they require is a quick jolt of voltage. And once the material is bent, it holds its shape—even after the voltage is removed.

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At microscopic scales, picking, placing, collecting, and arranging objects is a persistent challenge. Advances in nanotechnology mean that there are ever more complex things we’d like to build at those sizes, but tools for moving their component parts are lacking.

Now, new research from the University of Pennsylvania’s School of Engineering and Applied Science shows how simple, microscopic robots, remotely driven by magnetic fields, can use capillary forces to manipulate objects floating at an oil-water interface.

This system was demonstrated in a study published in the journal Applied Physics Letters on January 28, 2020.

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