Dark Energy And The Inverse Square Law

first_img Citation: Dark Energy And The Inverse Square Law (2007, January 25) retrieved 18 August 2019 from https://phys.org/news/2007-01-dark-energy-inverse-square-law.html “Newton’s inverse-square law has been around for a while,” Daniel Kapner tells PhysOrg.com. “But, by testing this law, we’re looking for new physics.” The new physics Kapner and his colleagues are looking for in their recent Physical Review Letters submission deals with dark energy. “Dark energy is an unknown driving force behind the acceleration of the universe, and we’re measuring the inverse-square law below the dark-energy length scale to look for a possible new gravitational phenomenon.”Kapner and his colleagues are associated with the Center for Experimental Nuclear Physics and Astrophysics at the University of Washington in Seattle. Their Letter, “Tests of the Gravitational Inverse-Square Law below the Dark-Energy Length Scale,” addresses questions of dark energy gravity possibilities. “As the universe expands, gravity should be slowing down that expansion,” explains Kapner. “But that’s not what is happening. Astrophysical measurements show that the expansion is speeding up. The unknown mechanism behind this accelerated expansion is termed Dark Energy.” Kapner and his colleagues use a sensitive device called a torsion balance to test the inverse-square law, attempting to shed some light on dark energy. “This is one step more complicated than the old mass on the end of a spring,” Kapner says, referring to the classic physics class demonstration of measuring a force by the distance a spring stretches. While the earth’s gravity pulls straight down, a sideways force can induce a very small twist of the balance. “This is done a vacuum chamber,” explains Kapner, “so there is no friction. This is essentially the best you can do with a direct measurement. If standard physics has new particles or exchange forces which act at this length scale, this apparatus would be sensitive to it.” The group’s torsion balance can measure gravity-strength forces down to distances of 55 microns.And the results regarding the dark-energy length scale? “There are no deviations from the inverse-square law,” Kapner insists. “We see it behaves just as Newton predicted.” The test, he says, establishes that there is nothing new at the dark-energy length scale. So the continuing acceleration of the universe remains a mystery.But the test used by Kapner and his colleagues is not limited to questions of dark energy. The torsion balance measurements can be used to constrain other models that suggest new exchange forces and particles. “We’ve used this to test other models, such as large extra dimensions in string theory,” he says. “And we could test any other models which predict deviations from the inverse-square law.”Kapner says that the next version of the project is being built now. “We can go to even smaller lengths, and get results that are 100 times better.” Kapner thinks that the current test pretty well ruled out that dark energy holds nothing new regarding short-distance gravity, but another test would make the team’s assertion stronger. “We want to keep refining this technique as far as technology will allow.”After all, Kapner points out, “Even though the obvious answer wasn’t there, this technique still holds promise for discovering something new.”By Miranda Marquit, Copyright 2007 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.center_img 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.last_img read more

Robot Suit May Help You Achieve a Perfect Golf Swing

first_imgA robotic feedback suit: markers on the right arm indicate the joints that are regulated by the system. Credit: Lieberman and Breazeal. ©2007 IEEE. MIT researchers Jeff Lieberman and Cynthia Breazeal have published the results of the study in a recent issue of IEEE Transactions on Robotics. The study presents a proof-of-concept wearable robotic system that provides real-time tactile feedback over every joint simultaneously. “Oddly enough, the idea for the robot suit initially came from a dream,” Lieberman told PhysOrg.com. “The dream involved people who weren’t physically able to express themselves, but who were mentally normal, who used a machine that aided them to get their inner feelings out. This ranged from people with muscular difficulties to even toddlers and ‘untrained’ people who do not know how to wield a paintbrush. Upon waking and thinking about that idea for about an hour, the idea for this project was born, and I started doing research that day; the overall project was about six months for software and hardware development.”In experiments with arm motions, the researchers found that the suit increased students’ learning rates by up to 23%, and reduced errors by up to 27%, as well as enabling students to learn movements “more deeply” by affecting their subconscious learning of motor skills. The latter can be especially important for patients with neurological injuries who have lost the ability to form new long-term memories, but can still build new motor skills.The suit works by optically tracking body markers for the teacher’s movement (or a pre-recorded ideal movement) and the student’s movement with a Vicon motion capture system, which has millimeter accuracy. The tracking data is fed to software that compares the teacher’s and student’s movements, and generates feedback signals to the suit. “The most challenging part was the human motion tracking system, which needs to function extremely quickly [about 100 hz] and be extremely accurate [about 1mm] to be able to adequately represent complex human motions,” Lieberman explained. “The system we use is a very expensive one for very high-tech applications, and for this to be successful in the real world it has to be much less expensive, and very robust. Tracking systems are typically optical [needing a setup in the room] or exoskeleton-style [wearable] which results in high expense and high weight, respectively. We’d like to solve both those at the same time and are working on new possibilities, although it is not the main focus of the research.” Small actuators against the skin vibrate in proportion to the amount of positional error of the student’s joints, giving the sensation of a vibrating “force field” around the correct motion. The suit can also correct for rotational errors of joints by sequentially vibrating individual actuators placed around joints clockwise or counterclockwise, giving the sensation that a rotating signal is urging the joint to rotate. Because everyone has different physical proportions, the system must first spend 10 minutes calibrating a new user’s limb lengths and joint locations, and then match them to the teacher’s proportions. Once a teacher’s motions are tracked, they can be recorded, repeated, and played at different speeds.As the researchers explain, the system has the potential to teach a student the precise motions of a teacher in place of the teacher. The system could therefore work well for teachers who are highly skilled, but are not good at teaching, by physically guiding a student who can simultaneously watch the teacher or a pre-recorded motion for visual feedback. However, visual feedback may not even be necessary with the wearable feedback suit, giving it the potential to be used as a training device for blind individuals.“The biggest initial market is in a sport such as golf, which already spends millions annually on video analysis machines, which tell the student exactly what they need to change,” Lieberman said. “But it tells them after they’re done, and decades of motor learning research tells us that students will learn much more quickly if the feedback is given immediately with no delay. Imagine how easy improving your swim stroke would be if you didn’t need to lift your head out of the water to improve it; after about 100 strokes, you’d be mimicking your teacher almost exactly.”He also explained that the health industry represents an equally, if not more exciting, opportunity. People with neurological trauma might use the suit for remapping their brains, and people with back pain could train their muscles with correct posture.“We are developing a new system using this technology that will monitor your posture and give you vibrotactile cues to keep yourself sitting properly,” Lieberman said. “Typically people only realize their posture is bad once pain starts, so this would give immediate feedback to prevent any pain, and retrain those who have already developed back pain. We should be running tests on this new device early next year. You can imagine having one suit, and 10 people each wearing it one week out of 10, to retrain their posture; the retraining of muscles should have a long-lasting effect, greatly helping those with back pain.”Before some of the complex motions— like a golf swing—are tested, however, the researchers say improvements are needed on the robot suit. These include creating a full-body suit with more than 100 actuators, defining ideal marker placement, investigating the human ability to respond to large amounts of feedback, and finding a less expensive and more mobile tracking system.“With the golf swing, the difficulty lies not only in the fact that you need to monitor many more joints, but also that the mapping from teacher to student is much harder to clearly define,” Lieberman explained. “In our tests, the mapping explicitly told the subject to try to copy the angles the teacher was making. In golf, it is more important that the end of the club contact the ball, and copying normal angles from someone taller than you will result in the club going into the ground, so it’s very difficult to map that.”Related information: robotic.media.mit.edu and bea.st. Citation: Lieberman, Jeff and Breazeal, Cynthia. “TIKL: Development of a Wearable Vibrotactile Feedback Suit for Improved Human Motor Learning.” IEEE Transactions on Robotics, Vol. 23, No. 5, October 2007.Copyright 2007 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. Researchers have developed a vibrotactile feedback suit to help individuals learn new motor skills more quickly and accurately than by mimicking human teachers alone. Besides golf, dance and sports training, the suit may also be useful for individuals undergoing motor rehabilitation after neurological damage, as well as for posture improvement.center_img 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: Robot Suit May Help You Achieve a Perfect Golf Swing (2007, October 31) retrieved 18 August 2019 from https://phys.org/news/2007-10-robot-golf.htmllast_img read more

New evidence backs up claim of dinosaur soft tissue find

first_img Explore further Citation: New evidence backs up claim of dinosaur soft tissue find (2011, June 15) retrieved 18 August 2019 from https://phys.org/news/2011-06-evidence-dinosaur-soft-tissue.html (PhysOrg.com) — In a new study, biochemist James San Antonio and colleagues offer evidence to support the claims by Mary Higby Schweitzer back in 2005, that she and her colleagues had unearthed a soft tissue specimen that belonged to a Tyrannosaurus rex. Roundly criticized by many in the science community, the specimen, discovered inside a femur fragment, has yet to be proven to be anything else. Now, in a paper published on PLoS ONE, San Antonio and his colleagues (including Mary Schweitzer) claim they’ve found a plausible explanation for the survival of soft dinosaur material after some 68 million years. The team focused on bits of collagen found in the remains, which are a group of proteins found in the flesh and bones of animals; it grows in a triple helix, which when it winds together, is known as a microfibril. When thousands of microfibril wind together, as they often do, they are known as microfibrils. After carefully studying 11 fragments of collagen recovered from the T. rex bone and then comparing them to similar fragments in modern rat and human collagen, the team discovered that the found fragments all came from the same innermost part of the fibrils that make up microfibrils. San Antononio likens them to tiny fibers that sit at the very innermost part of a very thick strong rope.In their paper, the research team suggests that because they were so tightly wound, the microfibrils could have survived over millions of years. They also note that the specimens also contained very few amino acids, which are very susceptible to decay.To back up her claims, or to quiet the naysayers, Schweitzer points out that if the specimens found were actually contaminants from other more recent organisms, as some have claimed, there should have been more randomness to the collagen, instead of the strict uniformity that was found. She also notes that two other labs have corroborated her results.The unfortunate side story to all the research done so far though, including these latest findings, is that thus far there is no way to definitively prove whether the soft tissue found inside that T. rex bone was in fact a remnant from its original owner, or something that came after. Thus, claims from both those supporting the idea that dinosaur tissue could have survived for millions of years, and those that think it’s nonsense, are likely to continue. © 2010 PhysOrg.com More information: San Antonio JD, Schweitzer MH, Jensen ST, Kalluri R, Buckley M, et al. (2011) Dinosaur Peptides Suggest Mechanisms of Protein Survival. PLoS ONE 6(6): e20381. doi:10.1371/journal.pone.0020381AbstractEleven collagen peptide sequences recovered from chemical extracts of dinosaur bones were mapped onto molecular models of the vertebrate collagen fibril derived from extant taxa. The dinosaur peptides localized to fibril regions protected by the close packing of collagen molecules, and contained few acidic amino acids. Four peptides mapped to collagen regions crucial for cell-collagen interactions and tissue development. Dinosaur peptides were not represented in more exposed parts of the collagen fibril or regions mediating intermolecular cross-linking. Thus functionally significant regions of collagen fibrils that are physically shielded within the fibril may be preferentially preserved in fossils. These results show empirically that structure-function relationships at the molecular level could contribute to selective preservation in fossilized vertebrate remains across geological time, suggest a ‘preservation motif’, and bolster current concepts linking collagen structure to biological function. This non-random distribution supports the hypothesis that the peptides are produced by the extinct organisms and suggests a chemical mechanism for survival. Tyrannosaurus rex femur (MOR 1125) from which demineralized matrix (insets; bars, 20 µm) and peptides were obtained. Image: PLoS ONE 6(6): e20381. doi:10.1371/journal.pone.0020381 Proteins, Soft Tissue from 80 Million-Year-Old Hadrosaur Add Weight to Theory that Molecules Preserve Over Time 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.last_img read more

Researchers discover genomewide variations in gene expression between male and female mammals

first_imgA team of researchers affiliated with several institutions in the U.S. has discovered genome-wide variations in gene expression between male and female mammals. In their paper published in the journal Science, the group describes their RNA sequencing studies in several types of mammals and what they found. Play Researchers find an evolutionarily preserved signature in the primate brain 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. Physiological differences between mammalian genders are quite often easy to spot—in addition to organs involved in reproduction, there are skeletal and facial hair differences, as well as height differences. Prior research and anecdotal evidence has also suggested there may be some differences in the way the brain works. But what about variations in gene expression? The researchers in this new effort report that very little research has been done in this area, which is a problem—recent studies have shown that there are many gender-based health issues. Women are more likely to suffer from autoimmune diseases, for example. And men are more likely to develop cardiovascular diseases. To understand why such differences exist, medical scientists need to better understand gender-based variations in the genome. To learn more about gender-based gene expression, the researchers sequenced the RNA of both genders of four non-human mammals: rats, mice, macaques and dogs. As part of their efforts, they tested different tissues in each of the animals to ensure that each germ layer was represented. They also sequenced tissue from all of the most prominent organs. They then compared what they found to similar data collected from human subjects stored in the Genotype Tissue Expression Consortium database.The researchers found examples of hundreds of conserved gender-biased gene expressions in each tissue. As just one example, they found that 12 percent of the gender differences related to average height in humans could be attributed to conserved gender-biased gene expression. They note that such findings are significant because they prove that gender biases in gene expression can lead directly to differences in traits.The researchers also found evidence that suggested such gender-biased gene expressions came about relatively recently, evolutionarily speaking. They suggest this finding indicates that researchers need to pay particular attention to such differences when using non-human models to study gender-based differences in humans. PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen Credit: CC0 Public Domaincenter_img © 2019 Science X Network Citation: Researchers discover genome-wide variations in gene expression between male and female mammals (2019, July 19) retrieved 18 August 2019 from https://phys.org/news/2019-07-genome-wide-variations-gene-male-female.html More information: Sahin Naqvi et al. Conservation, acquisition, and functional impact of sex-biased gene expression in mammals, Science (2019). DOI: 10.1126/science.aaw7317 Journal information: Science Explore furtherlast_img read more

Vegan delight

first_imgVegetarians often complain for the lack of option in the Capital, but complain no more! With special focus on perfection, Mr Banan, the man behind success and popular chains like Sagar Ratna and Swagath, has brought the same passion to its vegetarian venture Shraman at the Ashok.With its many cultural influences, it’s a place that offers a varied selection of cuisines to satisfy your palate. Signature dishes like Saundhi Paneer Tikka, Shraman 56 Bhog, Paneer Lazeez, Dal Shraman, Gatta Curry, Jodh Puri Mirchi Paneer, Vegetable Lohla Puri, Sabzi Balluchi and Shraman Punch will leave one craving for more. A visit promises to be a feast not only for the taste buds but also for the eyes.last_img read more