In a recent study, researchers have experimentally demonstrated for the first time a celebrated model of “phyllotaxis,” the study of mathematical regularities in plants. In 1991, S.L. Levitov proposed a model of phyllotaxis suggesting that the appearance of the Fibonacci sequence and golden mean in the pattern of spines on a cactus can be replicated for cylindrically constrained, repulsive objects. Now, researchers have constructed a “magnetic cactus” with 50 outward-pointing magnets acting as spines, which are mounted on bearings and free to rotate on a vertical axis acting as the plant stem. With this setup, the researchers, from Los Alamos National Laboratory in New Mexico; Cornell University in Ithaca, New York; and The Pennsylvania State University (PSU), have verified Levitov’s model, and their study has been published in a recent issue of Physical Review Letters. In their experiment, the researchers put the system in a low-energy state by mechanical agitation. Then the scientists observed as the magnets (spines) arranged to form phyllotactic spirals, generating a so-called Farey tree of unfavorable angles. The unfavorable angles are fractional multiples of 2π (i.e. 2πi/j, such as 2π/3, 4π/3, etc.). The spines on the magnetic cactus, like those on a plant, form a helix around the cylindrical stem by growing around these particular angles. The mathematical regularity of these static patterns of phyllotaxis surprised the researchers, until they made an even more surprising discovery. They found that the statics of phyllotaxis had been intriguing historical figures for the past several centuries and more.“Initially, we rediscovered all of static phyllotaxis, not realizing that it had already been discovered and investigated by figures such as Kepler, da Vinci, Bravais, and even the ancient Romans/Greeks,” coauthor Vincent Crespi, a physics professor at PSU, told PhysOrg.com. “We were quite excited by the beautiful mathematics and physics of the static ground-state energy plots, with the commensurate peaks and valleys in between. Then Cristiano [Nisoli, lead author from PSU and Los Alamos] found Levitov’s paper explaining similar static physics, but in a layered geometry. Only after that did we realize that our system had strong connections to biological phyllotaxis as well. We had made an independent re-discovery – several centuries later!” (PhysOrg.com) — One of humanity’s earliest mathematical inquiries might have involved the geometric patterns in plants. The arrangement of leaves on a branch, seeds in a sunflower, and spines on a cactus appear with an intriguing regularity, providing a simple demonstration of mathematically complex patterns. Citation: Magnetic Cactus Experimentally Demonstrates Mathematical Plant Patterns (2009, May 20) retrieved 18 August 2019 from https://phys.org/news/2009-05-magnetic-cactus-experimentally-mathematical-patterns.html Once the researchers realized that they had rediscovered static phyllotaxis, they decided to investigate the dynamics. Dynamic phyllotaxis had not previously been explored since historically people had been thinking in terms of biological systems. As Crespi explained, biological systems are highly damped and so don’t have well-defined phonons or soliton modes. “Having approached the system from the physics end, we were naturally equipped and disposed to study dynamics,” he said. “Cristiano’s simulations of the dynamical system, coupled to Nathan [Gabor, coauthor from PSU and Cornell] and Jay’s [Maynard, coauthor from PSU] experiments with the physical magnet system, then revealed fascinating new physics in the dynamical regime.”The team found that the dynamics of the magnetic cactus reveal interesting physical processes. The researchers observed unusual excitations in the cactus’ energy landscape. For instance, the domain walls that separate regions of different dynamics can move axially while rotating. These domain wall “kinks” can convert a potential energy difference into rotational kinetic energy, moving as solitons, which are pulses with unusually rich properties. The researchers observed other excitations (rotons and maxons) having a classical origin, even though these excitations were previously thought to be intrinsically quantum mechanical when observed in helium superfluids.The researchers explain that both the static and dynamic effects of phyllotaxis are purely geometrical. The various patterns can be described by the simple fact that a spine’s nearest neighbors in one dimension (along the stem) are not its nearest neighbors in three dimensions (around the curved surface of the stem). Because phyllotaxis has a purely geometrical origin, the scientists explain that the excitations observed here could appear across nearly every field of physics. For example, similar dynamics could occur in crystallized ion beams, in which the system self-organizes into concentric cylindrical shells. Dynamical phyllotaxis could also occur in other physical systems such as Wigner crystals in curved nanostructures and trapped ions in cylindrical potentials, and have applications in electronics. “The physical regime itself is defined in purely geometrical terms, so it is quite general across many sub-fields of physics,” Crespi said. “I am quite curious about the extension to the quantum regime, and also the charge-transport properties of a pinned lattice. If the lattice itself is pinned by external disorder (which is commonly the case), then the system will transport charge via motion of solitons (which, when the axial degree of freedom is released, will have a slightly different density than the rest of the system and hence carry charge). Different solitons will carry different charges, and when the solitons collide and/or merge, they can change identity and so change their charge. Quasiparticles that don’t conserve (mobile) charge in collisions is a quite unusual regime. Novel physical regimes such as that always carry the potential for unanticipated new physics and new applications.”More information: Cristiano Nisoli, Nathaniel M. Gabor, Paul E. Lammert, J.D. Maynard, and Vincent H. Crespi. “Static and Dynamical Phyllotaxis in a Magnetic Cactus.” Physical Review Letters 102, 186103 (2009).Copyright 2009 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Explore further (Left) Mammillaria elongata, or golden star cactus, displays a helical morphology. (Right) A magnetic cactus of dipole magnets on stacked bearings assumes phyllotactic spirals, similar to the biological cactus. With the magnetic cactus, physicists have investigated the dynamics of phyllotaxis. Image credit: Cristiano Nisoli, Nathaniel M. Gabor, Paul E. Lammert, J.D. Maynard, and Vincent H. Crespi. ©2009 APS. Computer model explaines alluring plant shapes This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Explore further Chief executive officer of Astrium, François Auque, said the system is at the testing stage, but that a viable system collecting and transmitting power from space could be within reach soon. Auque said space solar power is an attractive idea because it is an inexhaustible and clean form of energy. Unlike solar plants on Earth, orbital solar collectors can work around the clock, and there is no interference from clouds or atmospheric dusts or gases, which means the energy hitting photovoltaic cells in orbit is much greater than it would be for the same panels on the ground.Earlier concepts of beaming power to Earth from space were criticized because they relied on microwaves to transmit the power to the ground, which has safety concerns, so Astrium plans to use infrared lasers instead, which means that even if they were misdirected people and objects hit by the laser beams could not be scorched.The transmission of power via infrared laser has been tested in Astrium’s laboratories, and they are now concentrating on improving the system’s efficiency. Work on developing converters to convert received infrared energy to electricity is proceeding rapidly, and Astrium is collaborating in this work with scientists at the University of Surrey, in the UK. The company is hoping to achieve 80% efficiency in the conversion.According to Astrium’s chief technology officer, Robert Laine, at present the power handled by the system is limited by the size of the laser that can be built. A demonstration mission would also be necessary to prove the system works, and this should be possible within the present decade.The concept of harvesting solar power in space has been discussed for at least the last three decades, but the problems of power loss during transmission and the expense and difficulty of assembling large arrays of solar collectors in space have seemed almost insurmountable. However, Astrium is not the only company close to bringing the idea to fruition. Last September Japan announced it is planning to put a small demonstration solar collecting satellite in orbit by 2015. This system will transmit the power to Earth using microwaves.EADS Astrium is seeking investors and partners such as the EU, national governments, space agencies, or power companies, to fund and contribute in other ways to the development of its operational orbital solar collection and transmission system. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. © 2010 PhysOrg.com More information: EADS Astrium — www.astrium.eads.net/ (PhysOrg.com) — EADS Astrium, Europe’s biggest space company, plans to put a solar power satellite in orbit to demonstrate the collection of solar power in space and its transmission via infrared laser to provide electricity on Earth. $21 Billion Orbiting Solar Array will Beam Electricity to Earth Citation: European space company wants solar power plant in space (2010, January 21) retrieved 18 August 2019 from https://phys.org/news/2010-01-european-space-company-solar-power.html
(PhysOrg.com) — What if there was an eco-friendly car that acted like a plant? It would take in CO2, and its exhaust would be oxygen. That’s exactly what the Shanghai Automotive Industry Corporation unveiled at the Shanghai Expo 2010 recently. The YeZ is a concept car designed to photosynthesize carbon dioxide from the air, much like a plant. The car is even designed to emphasize the idea of a eco-friendly through a plant-like process. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. © 2010 PhysOrg.com Citation: YeZ: The Car that Acts Like a Plant (2010, May 21) retrieved 18 August 2019 from https://phys.org/news/2010-05-yez-car.html Not only will this green car make use of photosynthesis for power generation, but it will also be able to utilize wind power. CNET describes how the YeZ works:YeZ works its magic of photoelectric conversion with the help of state-of-the-art solar panels on the roof, wind power conversion via small wind turbines in the wheels, and carbon dioxide absorption and conversion through the bodywork. This last bit is made of a metal-organic framework that can apparently absorb carbon dioxide and water molecules from the air. Through the series of chemical reactions, energy is generated, and it’s then stored in the car’s lithium ion batteries. The car is a two-seater, though, and doesn’t appear to have much room for luggage. And, of course, it is only a concept. It might take as many as 20 years for this concept car to be available — if it is something that happens at all. But the YeZ does offer us some insight into what might be possible if we start looking more to the natural environment for solutions to our pollution problems. More information: Juniper Foo, “YeZ concept car sucks in C02, exhales oxygen,” CNET (May 20, 2010). Available online: news.cnet.com/8301-17938_105-20005538-1.html Explore further The Audi e-tron concept electric car Image source: http://news.drive.au
(a) An illustration of the energy-harvesting cantilever device. (b) A photo of the cantilever. (c) An optical micrograph and SEM image of the CNF material. Image credit: Venu Kotipalli, et al. ©2010 American Institute of Physics. (PhysOrg.com) — With the goal to enable small electronic devices to harvest their own energy, researchers have designed a device that can convert light and thermal energy into electricity. When exposed to visible light and/or heat (infrared) radiation, the 20-mm-long carbon-nanotube-film-based cantilever bends back and forth repeatedly, as long as the light and/or heat remains on. This is the first time that such cyclic bending behavior, which the scientists call “self-reciprocation,” has been observed in this kind of system. IMEC reports 40 microwatt from micromachined piezoelectric energy harvester Copyright 2010 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. More information: Venu Kotipalli, et al. “Light and thermal energy cell based on carbon nanotube films.” Applied Physics Letters 97, 124102 (2010). DOI:10.1063/1.3491843 The researchers, led by Professor Long Que and including graduate students Venu Kotipalli, Zhongcheng Gong, and other students from Louisiana Tech University, have published a paper on the device in a recent issue of Applied Physics Letters. In their experiments, they demonstrated that the device could generate 2.1 microwatts of power at a light intensity of 0.13 W/cm2, which is sufficient to operate some low-power microsensors and integrated sensors. The researchers predict that the power output could be significantly improved with further optimization.“The greatest significance of this work is that it offers us a new option capable of continuously harvesting both solar and thermal energy on a single chip, given the self-reciprocating characteristic of the device upon exposure to light and/or thermal radiation,” Que told PhysOrg.com. The 20-mm-long energy-harvesting device consists of a layer of carbon nanotube film (CNF) placed on top of an electrode and a piezoelectric material called lead zirconate titanate (PZT). Since carbon nanotubes are excellent absorbers of photons, the CNF layer efficiently absorbs the radiation and causes the underlying PZT layer to bend. As a piezoelectric material (known for its ability to convert mechanical energy into electricity), the moving PZT layer generates power. The impressive thing about the new device is that, once the cantilever reaches its maximum displacement under the radiation, the displacement decreases, then increases again, and continues this cycle as long as the radiation remains on. When the radiation is turned off, the displacement decreases to zero. As the scientists explain, the self-reciprocation is due to the cantilever continuously absorbing photons, as well as its high electrical conduction and rapid thermal dissipation into the environment. The self-reciprocation characteristic means that the energy-harvesting device has the ability to continuously generate energy without consuming other additional energy, such as for modulating the radiation. “To the best of our knowledge, previous reported research mainly exploited and developed for DC displacement,” Que said. “We observed this self-reciprocation phenomenon in my lab by accident for the first time, and thereafter we did a series of systematic experiments and confirmed that this phenomenon always occurs not only in the lab but also in the field under sunlight. In order to better understand this observation and optimize the performance of this technology, further fundamental investigations have been underway in our lab.” In the future, the scientists plan to investigate the contributions from the light and heat when the device is under illumination, although their observations so far indicate that the thermal portion is the major contributor. The scientists also anticipate that decreasing the device’s internal resistance, and perhaps operating an array of devices, could improve the power output. The energy-harvesting device could potentially be used to power a wide variety of systems, from implanted biomedical devices to remotely located sensors and communication nodes. “I also would like to mention that, given the nature of the cantilever-based device, actually this technology can harvest additional multiple types of energies such as all types of vibrational energies and wind energy as well, which we have already experimentally demonstrated but not reported in this article,” Que said. “This technology is truly a hybrid energy-harvesting technology.”Additional coauthors of the paper are Pushparaj Pathak, Tianhua Zhang, Yuan He, and Shashi Yadav. Citation: Cantilever bends repeatedly under light exposure for continuous energy generation (2010, October 5) retrieved 18 August 2019 from https://phys.org/news/2010-10-cantilever-repeatedly-exposure-energy.html Explore further
© 2012 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Her 3-D printed device is based on the Wilmington Robotic Exoskeleton (WREX), an orthopedic apparatus made from hinged bars and resistance bands. The WREX is described as an anti-gravity upper limb orthosis. The WREX was constructed to help children with little residual strength from muscular and joint disorders to move their arms in space. The problem was that, while WREX was able to help arthrogryposis sufferers as young as six years old, the child in this case study, Emma, was only two and weighed twenty-six pounds. Of life and limb Explore further (Phys.org) — A disabled toddler suffering from Arthrogryposis Multiplex Congenita (AMC) is able to pick up objects and play, not only thanks to her research team of doctors at the Nemours/duPont Hospital for Children but thanks to the technology of 3-D printing, which enabled her to use a magical arms device to move freely for the first time. The device was too heavy and bulky for her to manage easily. Development, even with WREX, would still be a challenge. The medical team on Emma’s case turned to what they knew about and had available in 3-D printing, which they put to use to suit Emma. They used a Dimension SST 1200es 3D printer and Stratasys production system. so as to create a prosthetic light enough for young Emma to continue moving around freely. The toddler was now able to lift her arms and pick up objects for the first time in her life. Her parents say that her very first sentence was the say that she wanted her magic arms. The Stratsys system makes use of medical-grade materials that contributed to the success of the device. The ABS plastic material for the magic-arms device was described as “human friendly, strong, and durable.”Most important, using a robust 3-D printing technology means that doctors can rely on a system to accommodate wide-ranging specifications for patients. In the case of Emma, the use of 3-D printing will allow the doctors to keep adjusting her prosthetic; it will evolve as she grows. “Without the 3-D printer we would not be able to make devices for children,” said one member of Emma’s team. He noted that in the area of prosthetics for children, “we need ‘custom everything.’” Creating a lightweight exoskeleton by hand would be extremely difficult, and 3-D printing technology enabled the researchers to customize WREX to exact specifications.Neuromuscular disabilities and orthopedic disorders in children include muscular dystrophy, spinal muscular atrophy, AMC, scoliosis, spinal cord injury, and leg length discrepancies. AMC is a rare congenital disorder that sees the muscles and joints shortened and muscles weakened. Citation: Movement-limited toddler gets 3-D-printed magic arms (w/ Video) (2012, August 6) retrieved 18 August 2019 from https://phys.org/news/2012-08-movement-limited-toddler-d-printed-magic-arms.html More information: Stratasys
Google advises Iran users to change passwords © 2013 Phys.org Google has been investigating alternatives to typed passwords, which includes a Yubico log-on device slid into a USB reader as part of Google’s quest to help strengthen password security. Google’s eyes are on future login techniques that will be primarily device-centric. Wired, in a sneak peek at the research paper set for publication, reported that the paper explores several physical device options, to make a password process that will be easy to accommodate but also sufficiently secure. Google’s suggestions include a ring worn on the finger. and the YubiKey device from Yubico. In the YubiKey scenario, it would be programmed so that it can automatically log a user into that user’s Google account. (Yubico was founded in 2007 with a prototype of its YubiKey for securing online identities. The devices are manufactured in Sweden and the U.S.) “Along with many in the industry, we feel passwords and simple bearer tokens such as cookies are no longer sufficient to keep users safe,” Grosse and Upadhyay wrote in their paper, according to Wired.Their project focus is none too soon, as, beyond Google and within the general Internet community, hacker fever has turned into password-reset fatigue. Users have complained over wiped out mail accounts and stolen data from their hacked accounts. Security experts have argued that no passwords are really secure enough, and even CAPTCHA schemes to prove the user is human have been found lacking in keeping users safe. Media attention to the password impasse grew widespread in November, when Wired senior writer Mat Honan wrote, “This summer, hackers destroyed my entire digital life in the span of an hour. My Apple, Twitter, and Gmail passwords were all robust—seven, 10, and 19 characters, respectively, all alphanumeric, some with symbols thrown in as well—but the three accounts were linked, so once the hackers had conned their way into one, they had them all. They really just wanted my Twitter handle: @mat. As a three-letter username, it’s considered prestigious. And to delay me from getting it back, they used my Apple account to wipe every one of my devices, my iPhone and iPad and MacBook, deleting all my messages and documents and every picture I’d ever taken of my 18-month-old daughter.”Google’s Grosse does not see the utter obliteration of the password but instead a situation where users can be freed from the need to implement and re-enter complex passwords. “We’ll have to have some form of screen unlock, maybe passwords but maybe something else,” he said. Nonetheless, he added, the primary authenticator will be some piece of hardware. Grosse and Upadhyay acknowledged that others have tried similar approaches and actually did not achieve much success in the consumer world, but the two authors of the research paper are not deterred. Success may come with wider cooperation outside Google. “Although we recognize that our initiative will likewise remain speculative until we’ve proven large scale acceptance, we’re eager to test it with other websites.” According to Wired, Google has created a universal protocol for device-based authentication that is able to work independent of Google’s own services; just a web browser is needed to support the standard. Credit: Wikipedia. (Phys.org)—Should typed passwords ever make their way into the Memory Bin, no tears will be shed in certain quarters at Google. The search giant is taking a serious look at a computing future where users have a safer environment that can secure their online information and accounts via physical passwords, perhaps in the form of finger rings or USB sticks or keys. Google’s Vice President of Security Eric Grosse and engineer Mayank Upadhyay have presented their suggestions for better hardware authentication in an upcoming research paper to be published in Security & Privacy magazine. Citation: Google wants Password123 in Museum of Bad Headaches (2013, January 19) retrieved 18 August 2019 from https://phys.org/news/2013-01-google-password123-museum-bad-headaches.html Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Many of the craft are expected to survive falling to Earth—those falling to moon’s surface, on the other hand will perish. Those who sign on to the project and buy a craft will be able to watch as their Pocket Spacecraft is made, tested, packed and carried to a rocket for launch.On its Kickstarter page, the team says they hope to collect the £290,000 goal needed for the project to proceed, and that if all goes as planned, would like to create a similar project for launching tiny craft to other planets in the solar system as well. More information: www.kickstarter.com/projects/1 … t-on-a-mission-to-thpocketspacecraft.com/about/press/This story was corrected: 4am July 3, 2013. (Phys.org) —One of the team members who successfully launched KickSat on Kickstarter has started a new project called “Pocket Spacecraft” with the aim of launching thousands of CD shaped “space craft” into space and landing them back on Earth or on the moon. Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Citation: KickSat co-creator, team launches new ‘Pocket Spacecraft’ project on Kickstarter (2013, July 2) retrieved 18 August 2019 from https://phys.org/news/2013-07-kicksat-team-pocket-spacecraft-kickstarter.html KickSat was a project that was designed to allow anyone (for a small price) to put a tiny satellite aboard a rocket and have it launched and sent into an orbit around Earth. That Kickstarter project reached its funding goals and is now scheduled for launch sometime later this year. In this new project, the team wants to give anyone who wishes to do so, the opportunity to send a craft to space and back, or more optimistically, to the moon.At the heart of the project is the Pocket Spacecraft—it’s shape and size is similar to a DVD only smaller and much thinner. The idea is to pack thousands of them onto a craft that is itself put aboard a rocket. Upon launch, some of the Pocket Spacecraft will be released into space where they will fall back to Earth—others will continue on to the moon where they will be set free to crash-land onto its surface.Each Pocket Spacecraft is up for sale—those who wish to purchase one can upload pictures or messages to it, or even add some programming. Each has a solar panel on it, electronic circuitry and communications gear that will allow for its owner to track its movements with their cell phone. Prices for the Pocket Spacecraft vary depending on whether the buyer wants their craft to fall back to Earth (Earth Scout-£99), or travel on to the moon (Lunar Scout-£199). Other options are also available to allow for groups to share a craft. © 2013 Phys.org NASA considering capturing and placing asteroid into moon orbit
Journal information: Nature Materials Representative micrographs showing cross-sections of hMSCs 36 h after encapsulation into 3D matrices made from the shortest (P1) and the longest polymer (P6) and constant GRGDS density, visualized by bright-field microscopy. Credit: (c) Nature Materials (2015). DOI: 10.1038/nmat4483 The extracellular matrix (ECM) plays an important role in controlling what happens within a cell by way of physical properties like stiffness and topography. This type of interaction in which mechanical properties lead to a series of biochemical activity is known as mechanotransduction. One are of interest is how ECM stress-stiffness influences stem cell differentiation.In order to study the mechanism behind stiffness-induced cell differentiation, researchers have tried to mimic the ECM environment. Prior studies employed several different systems to do this, including ECM-protein-derived hydrogels, synthetic polymers, and elastomeric mircopost arrays. Each of these has its strengths and weakness in how well it replicates the ECM. Das, et al. have designed a new type of cell culture system to mimic a three-dimensional ECM. They developed a thermoresponsive hydrogel from oligo(ethylene)glycol polyisocyanopeptides (PICs) that they can use to study the effects of stress-stiffening on human mesenchymal stem cells (hMSCs) in a three-dimensional setting by changing the length of the ethylene glycol portion of the polymer.After making their synthetic polymers, they were functionalized with known stem cell adhesives. Analysis of the polymers showed that all of the polymers were soft and exhibited similar stiffness with critical stress measurements falling within a biologically relevant range. Additionally, critical stress was found to increase linearly as a function of polymer chain length. Das, et al. then used their hydrogel polymers to investigate how stress-stiffening affected hMSC differentiation. Cells were cultured in a 3D matrix of the hydrogel surrounding the hMSCs. Markers for differentiation appeared after 96 hours. The cultures were tested for markers for osteogenesis and adipogenesis. Das, et al. found that cells cultured in the gel with the lowest critical stress demonstrated adipogenesis, while cells cultured in higher critical stress progressively favored osteogenesis over adipogenesis. Additional studies using RGD-modified polymers in the presence of antibodies showed that ligand interactions played an important role in mediating how stress-stiffening informs differentiation.Das, et al. suspected that microtubule dynamics likely plays a role in stem cell fate based on the results of treating their cells with cytochalasin D, actin polymerization inhibitor, and Taxol, a microtubule stabilizing agent. They decided to investigate how exactly microtubule dynamics is at work in this system by looking at the role of DCAMKL1 and RUNX2 in stress-stiffening and hMSC cell fate. DCAMKL1 is a known microtubule-associated protein and represses RUNX2. RUNX2 is an early osteogenesis marker. They found that DCAMKL1 expression was lowest in the longest polymers, those with highest critical stress, and its expression increased in gels with lower critical stress. Additionally, RUNX2 expression was not observed in low critical stress polymers, but was in the higher ones. Analysis confirmed a switch-like relationship between DCAMKL1 and RUNX2 and correlates to hMSCs’ preference for osteogenesis in the presence of higher stress-stiffening. The authors report that this is the first time DCAMKL1, a microtubule-associated protein, has been shown to be involved in stress-stiffening-mediated mechanotransduction pathway and demonstrates how microtubule dynamics is involved in hMSC cell fate.This study provides a new three-dimensional hydrogel for investigating stress-stiffening, and using this new hydrogel, Das, et al. were able to identify a new mechanotransduction pathway that controls hMSC differentiation that is distinctly different from two-dimensional systems. (Phys.org)—Several properties of the extracellular matrix affect cellular interaction, including stem cell differentiation. Some of these are physical properties, such as topography and matrix stiffness. In an effort to investigate these physical properties, Rajat K. Das, Veronika Gocheva, Roel Hammink, Omar F. Zouani, and Alan E. Rowan from Radbound University in The Netherlands, and the company Histide in Switzerland designed a model 3D hydrogel polymer system that demonstrates how stress-stiffening in the extracellular matrix causes human mesenchymal stem cells to favor osteogenesis over adipogenesis. Using their new model system, they determined that the expression of DCAMKL1, a microtubule associated protein, is decreasing when stress-stiffness is higher, demonstrating a novel pathway in which microtubule dynamics affects cell fate. Their work appears in Nature Materials. Growing bone cells: New method allows for more control in the differentiation of stem cells into bone cells More information: Rajat K. Das et al. Stress-stiffening-mediated stem-cell commitment switch in soft responsive hydrogels, Nature Materials (2015). DOI: 10.1038/nmat4483AbstractBulk matrix stiffness has emerged as a key mechanical cue in stem cell differentiation. Here, we show that the commitment and differentiation of human mesenchymal stem cells encapsulated in physiologically soft (~0.2–0.4 kPa), fully synthetic polyisocyanopeptide-based three-dimensional (3D) matrices that mimic the stiffness of adult stem cell niches and show biopolymer-like stress stiffening, can be readily switched from adipogenesis to osteogenesis by changing only the onset of stress stiffening. This mechanical behaviour can be tuned by simply altering the material’s polymer length whilst maintaining stiffness and ligand density. Our findings introduce stress stiffening as an important parameter that governs stem cell fate in a 3D microenvironment, and reveal a correlation between the onset of stiffening and the expression of the microtubule-associated protein DCAMKL1, thus implicating DCAMKL1 in a stress-stiffening-mediated, mechanotransduction pathway that involves microtubule dynamics in stem cell osteogenesis. © 2015 Phys.org Citation: New hydrogel gives clues to mechanism behind stress-stiffening-mediated mesenchymal stem cell fate (2015, December 17) retrieved 18 August 2019 from https://phys.org/news/2015-12-hydrogel-clues-mechanism-stress-stiffening-mediated-mesenchymal.html Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Journal information: Physical Review Letters (Phys.org)—Physicists have implemented the first experimental demonstration of everlasting quantum coherence—the phenomenon that occurs when a quantum system exists in a superposition of two or more states at once. Typically, quantum coherence lasts for only a fraction of a second before decoherence destroys the effect due to interactions between the quantum system and its surrounding environment. The collaboration of physicists, led by Gerardo Adesso at The University of Nottingham and with members from the UK, Brazil, Italy, and Germany, have published a paper on the demonstration of the extreme resilience of quantum coherence in a recent issue of Physical Review Letters.”Quantum properties can be exploited for disruptive technologies but are typically very fragile,” Adesso told Phys.org. “Here we report an experiment which shows for the first time that quantum coherence in a large ensemble of nuclear spins can be naturally preserved (‘frozen’) under exposure to strong dephasing noise at room temperature, without external control, and for timescales as long as a second and beyond.”Quantum coherence is an inherently quantum property that arises due to the wave-like nature of matter. Most importantly for potential applications, quantum coherence allows a quantum system to occupy a superposition of states. This trait leads to quantum parallelism, which is the key ingredient that allows some quantum devices to outperform classical ones in a wide range of applications. For instance, many research groups are currently working on harnessing quantum coherence to develop quantum algorithms, quantum cryptography, quantum metrology, and other quantum technologies.However, a major obstacle to developing these technologies is to overcome the fragile, fleeting nature of quantum coherence. While researchers have developed methods to slow down or correct the effects of decoherence, these methods are generally very resource-demanding.The method presented in the new study does not attempt to slow down or correct decoherence, but instead it reveals a natural mechanism under which resilience to decoherence spontaneously emerges. The results show that, under certain conditions, quantum coherence remains completely unaffected by common mechanisms of decoherence that typically destroy coherence. The new mechanism was predicted to exist in a study published last year by some of the same authors.In the new study, the researchers have experimentally observed this effect for the first time. The scientists demonstrated the mechanism in composite systems whose subsystems are all affected by decoherence, yet the overall composite system maintains its quantum coherence for as long as desired. More information: Isabela A. Silva et al. “Observation of time-invariant coherence in a room-temperature quantum simulator.” Physical Review Letters. DOI: 10.1103/PhysRevLett.117.160402Also at arXiv:1511.01971 [quant-ph] Citation: Forever quantum: physicists demonstrate everlasting quantum coherence (2016, October 14) retrieved 18 August 2019 from https://phys.org/news/2016-10-quantum-physicists-everlasting-coherence.html Physicists quantify the usefulness of ‘quantum weirdness’ “The trick lies in the fact that local decoherence acts in a preferred direction, which is perpendicular to the one in which coherence is measured,” Adesso explained. “Consequently, the resulting quantum states are overall degraded by such noise, but their observed coherence remains unaffected during the dynamics if the initial conditions are suitably chosen.”The researchers implemented the method using set-ups that involve room-temperature liquid-state nuclear magnetic resonance (NMR) quantum simulators, and demonstrated the effect in two- and four-qubit ensembles.”We used two different NMR set-ups,” said first author Isabela Silva, at the University of São Paulo and The University of Nottingham. “The first, owned by Ivan Oliveira’s group in Brazil, consisted of a simple chloroform sample labeled with Carbon-13 to encode the two-qubit system in the hydrogen and carbon nuclei. The four-qubit system was instead a heteronuclear sample specially developed in Steffen Glaser’s group in Germany. To manipulate this four-channel heteronuclear system independently, a prototype NMR probe head was also developed. Both systems are affected by natural and independent dephasing channels. Therefore, once initial quantum states satisfying special constraints are prepared, the quantum coherence freezing can be automatically observed, with no need for external control.”The researchers predict that the surprising effect can occur in larger systems composed of any even number of qubits. Odd-numbered qubit systems do not exhibit the resilience because the specific initial conditions supporting the phenomenon cannot be met due to the different geometry of quantum states in such instances.The researchers also showed that the mechanism appears to be universal, since it does not depend on the specific measure used to quantify the amount of coherence. The researchers expect that this trait will make the mechanism especially useful for future applications.”The universality paves the way toward designing a novel generation of quantum-enhanced devices able to harness coherence for unscathed performance in realistic and adverse conditions,” Adesso said.Besides technological innovations, the results may also shed light on the quantum coherence that occurs naturally in biological systems, such as the light-harvesting systems in plants. Previous research has shown that some biological systems can maintain quantum coherence for very long times in certain noisy environments. “The new study raises the possibility that these systems may have evolved an ability to harness natural mechanisms for coherence protection, similar to the one reported here,” said coauthor Rosario Lo Franco at the University of Palermo in Italy. (a) Preparation of two-qubit states in a chloroform molecule that exhibit quantum coherence for an arbitrarily long time. (b) Visual representation and (c)-(f) tomographies of the state dynamics. Credit: Silva et al. ©2016 American Physical Society © 2016 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further
© 2019 Science X Network Recent advances in the observation of high-energy radiations, including X-rays and gamma-rays, have unveiled many high-energy aspects of the universe. To achieve a complete understanding of these radiations, however, researchers need to find out more about the high-energy particles (i.e. cosmic rays) that produce them. In fact, non-thermal radiations characterized by the power-law spectrum are all backed by the acceleration and propagation of these rays. A direct observation of these cosmic rays can only be achieved by placing measuring instruments above all, or most, of the Earth’s atmosphere. In addition, as these highest-energy particles are quite rare, studying them requires significantly long observation times. The International Space Station (ISS) is thus an ideal location to collect these observations. The CALET collaboration, a large team of researchers from several renowned universities worldwide, has developed an instrument that can identify high-energy particles (e.g. electrons, protons and other atomic nuclei) and accurately measure their energy. They then placed this instrument on the ISS and used it to collect a direct measurement of the cosmic-ray proton spectrum. In a recent paper published in Physical Review Letters, the researchers presented the analysis and results of their measurements. “In order to observe cosmic rays, especially galactic cosmic rays, it is necessary to detect them at high altitude where the remaining atmosphere is sufficiently thin,” the CALET collaboration told Phys.org, via email. “For this purpose, many instruments are designed and flown to carry out direct observations for years. As a result, we now have a standard picture of galactic cosmic rays and know that cosmic rays are accelerated by the shock waves in supernova remnants, propagate diffusively through the irregularity of galactic magnetic field, and finally escape from our Galaxy.”Since the beginning of the 21st century, researchers have made significant progress in the observation of cosmic rays using particle-detection techniques developed in collider experiments. Over the past decades, space experiments that leverage Earth’s lack of atmosphere have also suggested the occurrence of an unexpected spectral hardening in cosmic rays such as protons, contradicting previous single power-law spectrum predictions. Researchers have proposed several theoretical models to explain this observed spectral hardening, which are still actively debated upon. Exposed Facility of Japanese Experiment Module on the International Space Station. CALET is installed on the port #9. Credit: Adriani et al. Citation: Direct measurement of the cosmic-ray proton spectrum with the CALET on the ISS (2019, May 27) retrieved 18 August 2019 from https://phys.org/news/2019-05-cosmic-ray-proton-spectrum-calet-iss.html Journal information: Physical Review Letters “CALET was optimized for measurement of cosmic-ray electrons, but is also beautifully capable of identifying other charged particles: protons (which are hydrogen nuclei), helium nuclei, and nuclei of heavier elements,” the CALET collaboration explained.CALET is made up of three detector systems, each composed of various types of scintillators that emit a pulse of light when penetrated by a charged particle. The charge detector (CHD) at its top can identify the charge of the incident particle (i.e. 1 for electrons and protons, 2 for helium nuclei, etc.), while an imaging calorimeter (IMC) supplements the charge measurement of the CHD, identifies the trajectory of the particle and starts measuring its energy. The final component of CALET is a total absorption scintillating calorimeter (TASC); a very thick [26.4cm] stack of high-density scintillators (lead tungstate) that is thick enough to contain the entire shower of particles initiated by interaction of the particle with thin layers of tungsten interspersed between scintillators in the IMC. The TASC component is thicker than any previously developed space-based calorimeter, which gives CALET an unprecedented precision and range of energy measurement.CALET was officially launched back in August 19, 2015 and installed on the Japanese Experiment Module-Exposed Facility on the ISS, with an expected mission duration of five or more years. The researchers’ scientific observations began a few months later, on October 13, and continuous operations have been carried out since. “Our data analysis consists of detector calibration, event reconstruction, proton-candidate selection based on the charge and other quantities, estimation of remaining contamination and its subtraction, energy unfolding considering the detector response and the detection- efficiency correction,” the CALET collaboration explained. “Detailed assessment of systematic uncertainties including the tune up and the validation of the Monte Carlo simulation using the beam test results at CERN-SPS is another key point in this analysis.”The recent results published by the researchers are based on flight data up to August 31, 2018. The fully calibrated and reconstructed dataset they collected, dubbed ‘level 2,” amounted to more than 30 TB, yet the resultant proton spectrum was merely a few kB of it. The CALET space instrument enabled the measurement of the cosmic-ray proton spectrum from 50 GeV to 10 TeV covering, for the very first time, the whole energy interval that was previously investigated in separate sub-ranges using different magnetic spectrometers (e.g. BESS-TeV, PAMELA, and AMS-02) and calorimetric instruments (e.g. ATIC, CREAM, and NUCLEON), with a single instrument. Cosmic-ray proton spectrum measured by CALET (red points) from 50~GeV to 10~TeV, together with recent direct measurements. Credit: Adriani et al. Schematic view of CALET calorimeter, consisting of Charge Detector (CHD), Imaging Calorimeter (IMC), and Total Absorption Calorimeter (TASC). Credit: Adriani et al. Explore further More information: O. Adriani et al. Direct Measurement of the Cosmic-Ray Proton Spectrum from 50 GeV to 10 TeV with the Calorimetric Electron Telescope on the International Space Station, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.122.181102 “CALET has provided a precise measurement of the cosmic-ray proton energy spectrum over a wider range of energies than from any previously published results from other instruments,” the researchers said. “CALET’s results agree with prior measurements at lower energies, and extend those measurements to higher energies.” Using CALET, the researchers were able to finally establish that the intensity of protons at higher energies is significantly greater than would be expected from a simple extrapolation of the intensity spectrum from lower energies, which had already been suggested by earlier measurements. This ‘hardening’ of the high-energy proton spectrum demands an alteration of earlier methods of cosmic-ray production and propagation through our galaxy. “CALET provides an accurate direct measurement of the cosmic-ray proton spectrum in a wide energy range from 50 GeV to 10 TeV showing progressive hardening in the TeV region, thereby severely constraining current models of acceleration and propagation of galactic cosmic rays discussing the generally observed hardening of nuclei spectra,” the researchers explained. “The CALET measurement helps to draw a coherent experimental picture, overcoming the long standing issue of connecting the precise measurements performed by magnetic spectrometers below about 1 TeV, with calorimetric measurements performed by balloon experiments at supra-TeV energies. We think this could be considered as one of the highlights in the history of proton-spectrum measurements.”In addition to confirming the existence of spectral hardening, the measurements collected by the CALET collaboration could inform calculations used in indirect searches for dark matter, atmospheric and cosmogenic neutrinos, as well as gamma-ray physics. The researchers are now planning to test a further hypothesis related to a possible charge-dependent cutoff in the nuclei spectra, which would explain the “knee” observed in the all-particle spectrum. This hypothesis can only be tested directly with measurements collected in space experiments of a significant duration, with significant exposure and with the ability to identify individual elements based on charge measurements. “The acceleration limit of supernova remnants calculated with standard parameters is typically found to be far smaller than the energy of the ‘knee,’ as observed indirectly by ground detectors,” the researchers explained. “Therefore, precise direct observation of the proton and helium spectra at high energy is highly important. Improved statistics and better understanding of the instrument based on the analysis of additional flight data during the ongoing five years (or more) of observations might reveal a charge dependent energy cutoff possibly due to the acceleration limit in supernova remnants in proton and helium spectra, or set important constraints on the acceleration models.” The calorimetric electron telescope (CALET) created by the CALET collaboration is a space-based instrument optimized to measure the all-electron spectrum and equipped with a fully active calorimeter. Their instrument can measure the main components of cosmic rays, including protons, light and heavy nuclei in the energy range up to 1 PeV. CALET succeeds in direct measurements of cosmic ray electron spectrum up to 4.8 TeV This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.