Month: August 2019

Modified gravity v dark energy

first_imgFor many years now, scientists have wondered why the universe is expanding faster than it should be. Through conventional knowledge of physics, the universe should be expanding at a slower pace that observations show that it is. “There are two main theories for why the universe is expanding so fast,” Martin Kunz tells PhysOrg.com. “One is modified gravity and the other is the presence of dark energy. We want to figure out how to distinguish between the two.” Explore further Citation: Modified gravity v. dark energy (2007, April 12) retrieved 18 August 2019 from https://phys.org/news/2007-04-gravity-dark-energy.html Detecting the difference between dark energy and modified gravity would provide physicists with a better understanding of how the universe works. And detecting modified gravity would add a further benefit by contributing to the understanding of one the fundamental forces in the universe. Kunz, a scientist at the University of Geneva, and his colleague Domenico Sapone have published a Letter in Physical Review Letters addressing the difficulties of distinguishing between modified gravity and dark energy. The Letter is titled “Dark Energy versus Modified Gravity.”“There are theoretical problems with dark energy,” explains Kunz, “and this had led people to modified Einstein’s general relativity in order to get modified gravity, which some think would explain the expansion of the universe.” The problem, he says, comes in when one tries to observe one of these phenomena. “We cannot observe either dark energy or modified gravity directly. We can only observe how galaxies behave.”Kunz points out that in many models, the universe is shown as smooth, assuming that the energy is evenly distributed and homogenous. “This is not completely the case,” Kunz says. “There are small fluctuations. But many measurements only probe the smooth universe.” He continues: “In this simple model, you can make everything look like a component with negative pressure, there is no way to decide whether it is due to dark energy or a modification of gravity.” Some scientists have looked at the growth of structure in the universe as way to distinguish between the effects of modified gravity and the effects of dark energy. It is these measurements that Kunz and Sapone find lacking in terms of ability to detect differences between the two. Through some modeling and equations of their own, the two have found that dark energy perturbations can affect the distribution of galaxies in a way that matches the effects of modified gravity. “At a certain level, dark energy and modified gravity look the same,” Kunz explains.“People hoped that you could prove general relativity wrong by studying how structure forms in the universe,” Kunz says. “We showed that you could rule out certain models of dark energy, but not general relativity itself.”So, while Kunz and Sapone did not manage to show how to distinguish dark energy from modified gravity, they did discover new avenues that need to be explored in the debate of modified gravity versus dark energy. And they discovered something else: “One thing we saw that was really essential was anisotropic stress,” says Kunz. “The presence or absence of anisotropic stress might help to distinguish between the two. If we measure the presence of anisotropic stress in the universe, it is more likely to be modified gravity.”Kunz also sees hope for the future of settling this debate. “Over the next few years, precise measurements of weak gravitational lensing will become possible, which also measures anisotropic stress. Combined with the next round of distance measurements with supernovae, we will be able to get good constraints.”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 Supercomputer shows ‘Chameleon Theory’ could change how we think about gravity 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

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Polymer remembers four shapes

first_img © 2010 PhysOrg.com Researchers design shape-memory polymers for biomedical applications Explore further Quadruple-shape memory properties of PFSA. Visual demonstration. Image credit: Nature. More information: Tunable polymer multi-shape memory effect, Tao Xie, Nature, 464, 267-270 (11 March 2010), DOI:10.1038/nature08863 (PhysOrg.com) — A new study by General Motors has found that a polymer used commercially in fuel cell membranes can “memorize” four shapes, each assigned to a different temperature. The material could find applications in fields such as space exploration and biomedical engineering. Xie said that each shape would be assigned to a specific temperature chosen by the manufacturer. As long as there is sufficient difference between the temperatures, the material has been demonstrated to be able to hold four shapes, but Xie said it may be able to hold more. The next step in the research is to investigate shape memory polymers that are more appropriate for bulk processing, and those with UV radiation resistance for use in space, or biocompatibility for use in medical applications such as self-tying sutures, bone implants and blood vessel stents.The paper, by Tao Xie of the General Motors Research and Development Center in Warren, Michigan, is published in the journal Nature. The material, a perfluorosulphonic acid ionomer (PFSA) called Nafion, is a shape memory polymer. These materials can remember shapes set under specific conditions of moisture content, temperature, light, or exposure to a magnetic field. When they are next exposed to the same conditions, they revert to the remembered shape. Shape memory polymers have been known for decades, and have been used in wiring insulation and other industrial applications. Tests have been carried out for medical purposes such as stents for clearing blood vessels of clots, and the US space agency NASA has also considered using shape memory polymers for applications such as unfolding antennas in space. Previous polymers have only been able to remember two or three shapes including the original shape, and Nafion is the first known material that can memorize four.The research team, led by Tao Xie, heated thin films of Nafion, shaped it at a fixed temperature, and then cooled the material. They then repeated the process for other temperatures and shapes. When reheated the polymer reverted to the shape formed previously at that temperature. The shapes are locked in when the material is at its transition temperature, at which its structure changes from a frozen “glass” to a mobile “rubbery” phase. Nafion is able to hold more shapes than other polymers because it has a wide transition temperature range from about 55 to 130°C, leaving more temperature options available. Triple-shape memory properties of PFSA. a. Visual demonstration. b. Quantitative thermal mechanical cycle. Image credit: Nature. Citation: Polymer remembers four shapes (2010, March 15) retrieved 18 August 2019 from https://phys.org/news/2010-03-polymer.html 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

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Researchers find a way to predict dragon kings in small circuits

first_img © 2013 Phys.org (Phys.org) —A research team with members from Switzerland, the U.S. and Brazil has discovered a way to predict and circumvent “dragon kings” that appear in a synchronized master-slave circuit system that occasionally become unsynchronized. They have uploaded a paper they’ve written describing their system and results to the preprint server arXiv—later to be published in the journal Physical Review Letters. Appearance of dragon-kings. Bubble event-size probability density function (PDF) for c = 4.4. The dashed line is a fit to a power law. Credit: arXiv:1301.0244 [nlin.CD] Journal information: arXiv Citation: Researchers find a way to predict ‘dragon kings’ in small circuits (2013, October 30) retrieved 18 August 2019 from https://phys.org/news/2013-10-dragon-kings-small-circuits.html , Physical Review Letters 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 Chaos-on-a-chip model shows market bubbles may be predictable, controllable Dragon kings (the term came about as a means to describe wealth distribution in medieval times) are large unexpected events that occur in complex systems. Earthquakes, stock-market crashes and even the abnormal population growth of Paris are some common examples. For obvious reasons, scientists and others have been studying such events to try to figure out if they can be predicted, and if so, if some of them at least, can be prevented. In this latest effort, the researchers weren’t studying dragon kings, they were simply trying to better understand a circuit anomaly—a master/slave circuit connected together in a way that was supposed to keep the two synchronized with one another. The problem was, sometimes the two would occasionally go completely out of whack. In studying the circuit they discovered that it was very small occasional misses in the synchronizing process that led to bigger and bigger misses until the circuits became completely unsynchronized. Further study showed that making a minor adjustment to the system just before it went out of whack prevented the big event from occurring. Later analysis of the properties of the big event showed that it followed the definition of a dragon king. This has led the researchers to suggest that if such variables as were found in the circuit system could be identified in other systems, it seems reasonable to conclude that large random fluctuations might be predicted and in some cases prevented, in them as well.That’s a pretty big jump the researchers acknowledge—other systems are not only far more complex but have some variables beyond human control, such as those that lead to earthquakes or the amount of money investors have available to spend. But, because they were able to predict a dragon king in a circuit, it shows it can be done, at least in one system. That alone is enough to offer hope that similar analysis of other systems might lead to the same ability in some others. More information: Predictability and suppression of extreme events in complex systems, arXiv:1301.0244 [nlin.CD] arxiv.org/abs/1301.0244AbstractIn many complex systems, large events are believed to follow power-law, scale-free probability distributions, so that the extreme, catastrophic events are unpredictable. Here, we study coupled chaotic oscillators that display extreme events. The mechanism responsible for the rare, largest events makes them distinct and their distribution deviates from a power-law. Based on this mechanism identification, we show that it is possible to forecast in real time an impending extreme event. Once forecasted, we also show that extreme events can be suppressed by applying tiny perturbations to the system.last_img read more

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Oldest known sponge found in China

first_img Scientists discover bacteria in marine sponges harvest phosphorus for the reef community 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. Sponges have been the object of research for quite some time, but when they first appeared on Earth has been the subject of debate, with estimates ranging from 700 million years ago to a time known as the Cambrian period (541 million to 485 million years ago). This new finding would place the sponge approximately 60 million years before the Cambrian started. Researchers want to pin down the date because they believe it is critical to understanding early animal evolution—the split between sponges and most other animals, it is believed, was a major event in the early history of life on our planet.In any case, the find is impressive because of its condition, it is nearly pristine—and tiny, just over one millimeter in height and width. To get a good look at it required scanning electron microscopy and X-ray technology. The team has named it Eocyathispongia qiania and note that it is made up of hundreds of thousands of cells and is formed in three tube-like chambers that are affixed to a common base, with cell structures that resemble those in modern sponges. They also found surface cells that indicate pores, again, like modern sponges, which control water flowing into the organism. There was also an area inside one of the tubes with pits surrounded by raised collars, a possible precursor to choanocyte cells which modern sponges use to move water through their bodies.In addition to being the oldest of the really old sponge fossils found, the find also represents one of the most pristine. It cannot be confirmed as yet, of course, because that requires more than one specimen example. The researchers appear optimistic that such confirmation will be forthcoming, however, as they have more material from the site where the sponge was found, and will be sifting through it looking for more tiny sponges and perhaps other organisms as well. © 2015 Phys.org A scanning electronic microscope image of the 600 million-year-old sponge-like animal fossil. Credit: Zongjun Yin Explore furthercenter_img More information: Sponge grade body fossil with cellular resolution dating 60 Myr before the Cambrian, PNAS, Zongjun Yin, DOI: 10.1073/pnas.1414577112AbstractAn extraordinarily well preserved, 600-million-year (Myr)-old, three-dimensionally phosphatized fossil displaying multiple independent characters of modern adult sponges has been analyzed by SEM and synchrotron X-ray tomography. The fossilized animal (Eocyathispongia qiania gen. et sp. nov.) is slightly more than 1.2 mm wide and 1.1 mm tall, is composed of hundreds of thousands of cells, and has a gross structure consisting of three adjacent hollow tubes sharing a common base. The main tube is crowned with a large open funnel, and the others end in osculum-like openings to the exterior. The external surface is densely covered with flat tile-like cells closely resembling sponge pinacocytes, and this layer is punctuated with smaller pores. A dense patch of external structures that display the form of a lawn of sponge papillae has also survived. Within the main funnel, an area where features of the inner surface are preserved displays a regular pattern of uniform pits. Many of them are surrounded individually by distinct collars, mounted in a supporting reticulum. The possibility cannot be excluded that these pits are the remains of a field of choanocytes. The character set evinced by this specimen, ranging from general anatomy to cell type, uniquely indicates that this specimen is a fossil of probable poriferan affinity. So far, we have only this single specimen, and although its organized and complex cellular structure precludes any reasonable interpretation that its origin is abiogenic, confirmation that it is indeed a fossilized sponge will clearly require discovery of additional specimens. (Phys.org)—A team of researchers with members from China, the U.S. and France has identified an ancient sponge found in a geologic formation in southern China and have dated it to 600 million years ago. In their paper published in Proceedings of the National Academy of Sciences, the team claims the sponge is the oldest ever found and likely represents a group of descendants that is an ancestor of all sponges. Citation: Oldest known sponge found in China (2015, March 10) retrieved 18 August 2019 from https://phys.org/news/2015-03-oldest-sponge-china.html Journal information: Proceedings of the National Academy of Scienceslast_img read more

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You Recognize Your Face Even When You Dont See It

first_imgFor the experiment, participants looked at a cross symbol displayed in the center of a computer screen while a picture of a face appeared on each side of the cross. The face on one side of the cross was the participant’s own face, while the face on the other side of the cross belonged to a stranger. The participants were told to focus their attention on the cross and ignore anything else that might appear. “Despite our participants not knowing that at a givenmoment their own face was being presented, their brain focused attention onthat side of the field of view. This means that the brain must have – withoutthe participation of consciousness – identified both of the faces and reactedto the face known as its own. It thus seems that consciousness is not necessaryfor recognition of faces after all,” adds Michał Wójcik. “This type of technique allows us to test – inlaboratory conditions – the influence of stimuli that reach our senses but arenot strong enough to reach our consciousness,” says coauthor Michał Bola, whospecializes in the study of unconscious processes. Previous research has shown this phenomenon withsimple stimuli – such as a red object embedded among many green objects – butthis study shows that it occurs with more complex stimuli, as well. Importantly, thefindings also showed that participants automatically attended to their ownfaces even when they weren’t aware of them. “Both our intuition and previous studies indicate thatour own face is to each of us a very strong and important stimulus. It awakensa variety of feelings and associations, and as a consequence effectivelyattracts our attention,” explains study coauthor Anna Nowicka, who specializesin researching the mechanics of how we process information about ourselves. The findings showed that participants automaticallyattended to their own faces when they appeared on screen, despite the fact thatthey were instructed not to do so. “This is a confirmation of earlier researchconducted by our and other teams, showing that we preferentially process stimulibelonging to the concept of ‘I,’ for example our own name or face,” MariaNowicka says. “We’ve known for a long time that our brain is capableof subliminally processing and analyzing different types of simple stimuli. Inour studies, we are trying to respond to the question of whether more complexstimuli can be efficiently processed subliminally and subsequently influence ourbehavior,” explains lead author Michał Wójcik, who conducted the research atthe Nencki Institute of Experimental Biology in Warsaw and is a current PhD studentat the University of Oxford. On half of the trials, the faces were clearly visible and easy to recognize; on the other half of the trials, the faces were displayed for only 32 ms and were followed by a random pattern that masked the faces. This procedure is commonly used to present stimuli to participants outside of conscious awareness, and the researchers confirmed that it was effective in this study: Participants were able to identify faces that appeared briefly, but they were not able to identify the faces followed by a “mask” pattern. “It has been known for many years that directing ourattention to one side causes an asymmetry in brain activity betweenhemispheres. By analyzing these asymmetries, we were able to determine if in agiven moment the participant’s attention was directed to the face presented onthe left or the right,” explains Maria Nowicka, a coauthor and PhD student atthe Nencki Institute.center_img Given the limited capacity of our attention, we only process a small amount of the sights, sounds, and sensations that reach our senses at any given moment — what happens to the stimuli that reach our senses but don’t enter awareness? Research suggests that certain stimuli – specifically, your own face – can influence how you respond without you being aware of it. The findings are published in Psychological Science, a journal of the Association of Psychological Science. A face is one such complex object. Despite the fact that most faces are pretty similar to one another, through the simultaneous analysis of many elements – eyes, lips, nose – we are usually able to recognize the faces of people we know with accuracy and efficiency. “In our study, we showed that much more complexobjects – like faces, which consist of many elements and require more detailedanalysis to recognize – can unconsciously attract attention,” says Bola. “Ourexperiment is part of a research trend indicating that the capacities of our ‘unconsciousmind’ are much larger than we previously thought.” The researchers used EEG to monitor participants’brain activity as they completed the task. The researchers hypothesized that because one’s own face is such a strong stimulus the brain will recognize and react to it outside of conscious awareness.  The researchers note that additional research will benecessary to determine whether it is specifically the identity of one’s ownface or the extreme familiarity of one’s face that attracts attention outsideof awareness. They also plan to investigate whether this preferential attentionoutside awareness is specific to faces or also occurs with other complexobjects. The project was funded by the National Science Centre Poland. All data have been made publicly available via the Open Science Framework. This article has received the badge for Open Data.last_img read more

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Target luxury

first_imgWalter Knoll, a luxury German furniture brand, further strengthens its presence in India by announcing Alpana Kirloskar, renowned architect and interior designer, as its Brand Ambassador for the Indian Market. The announcement was made by Markus Benz, CEO and Partner, Walter Knoll on 28 September at Taj Mahal Hotel in the Capital. Kirloskar commented, ‘It is an honour to be associated with the brand and I relate to its 150 year old legacy and core values and beliefs. As an architect I respect the excellence for high quality, timeless design, skilled craftsmanship and attention to detail. I am proud to be the brand ambassador of Walter Knoll and strengthen its presence amongst the discerning Indians.’   Also Read – ‘Playing Jojo was emotionally exhausting’Markus Ben said, ‘India is a country with a modern understanding of architecture and design. Increasing wealth, the presence of international premium brands, and appreciation of quality and design, marks India as a growth market. We want to further strengthen the brand Walter Knoll in India.’Other guests present at the event were – Raseel Gujral, Mohit Gujral, Jyothi Rath, and Sunita Kohli, among others. Industrialists like Priya Paul, Nakuland Timsy Anand, Dipika Jindal, Alok Modi, Sushil Ansal, Sheetal Ansal, Sanjay Chandra, Archana and Vipin Luthra were also present.last_img read more

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South Bengal districts parts of city receive moderate rain

first_imgKolkata: Rains, along with squally winds, lashed some of the South Bengal districts of Bengal and the northern fringes of the city on Sunday afternoon, creating inconvenience for people. Slow traffic movement was reported in some parts, including suburban areas, following the rain. The districts that have received the maximum rainfall, are North 24-Parganas, South 24-Parganas, Howrah and Hooghly. Some other districts have also received rainfall. Rain was moderate in the northern parts of the city and its outskirts. Also Read – Heavy rain hits traffic, flightsThe regional meteorological centre has predicted that a wind measuring around 50-60 km per hour may sweep through some of the South Bengal districts, along with moderate rainfall in the next 24 hours. Various parts of the city and the districts remained overcast from Sunday morning. According to the weather office, a low pressure trough has formed, bringing rainfall in the city. Sunday’s rainfall has brought down the temperature in the city and its adjoining areas by a few notches. This has given relief to the people, who were facing sultry and uncomfortable weather for the past couple of days. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedIt may be mentioned that an alert has been issued to East Midnapore district administration, saying that there may be a high tide in Digha. The fishermen in the area have been alerted not to venture out, due to rough sea. A thunderstorm, along with rainfall, had lashed the city on last Tuesday, killing 18 persons across the state.The meteorological office in Alipore predicted that similar conditions may prevail for the next 24 hours. Apart from the city, the coastal districts will also receive light to moderate rainfall, along with a strong wind which will also sweep through South Bengal. The sky will remain cloudy in some parts of the state.last_img read more

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Kate Moss husband to exhibit her nude photos

first_imgSupermodel Kate Moss’ husband Jamie Hince is planning an exhibition of his wife’s naked photographs. His debut exhibition opened last June in New York.The model is thought to be excited about becoming the centre of attention in the display.“Jamie is compiling a series of iconic nude photographs of his wife around their home for his second exhibition,” a source told dailystar.co.uk.last_img

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AAP MLAs demand gazetted holiday on Ambedkar Jayanti

first_imgAAP’s Kondli MLA Manoj Kumar said that Ambedkar Jayanti falls under restricted holidays, as announced by the government. However, former Delhi Minister Raj Kumar Chauhan had said that Ambedkar’s birth anniversary has always been celebrated as a holiday. The government of India has maintained Ambedkar’s Jayanti under the observance holiday category, while Vaisakhi has been kept as restricted holiday on same date. Kumar said that every year, the city government announces a holiday on this day, around 10-12 days before the jayanti. “We met the CM and demanded him to announce a holiday for Ambedkar’s birth anniversary,” Kumar said.last_img read more

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Aroop Biswas to hold meeting today to end Tollywood tussle

first_imgKolkata: The stalemate in the shooting of television serials in Tollywood may be resolved, as the state Youth affairs minister Aroop Biswas will convene a high level meeting with the representatives of Artistes’ Forum and Federation of Cine Technicians on Thursday.It is assumed that the technicians may arrive at a negotiation with the producers. There had been a ceasework by the Artistes’ Forum, with a demand to regularise pay.The producers’ association said it was ready for talks with no pre-condition, while the artistes body maintained that dialogue would start only after getting a formal letter from the other side. Also Read – Rain batters Kolkata, cripples normal lifeThe talks between the forum and the Welfare Association of Television Producers (WATP) had yielded no results. Federation of Cine Technicians and Workers of Eastern India had issued a Press release on Tuesday, saying that the artistes have agreed to join work the moment WATP agrees to implement the MoU signed between the producers and artistes.The forum had also specified that any artiste working for more than 10 hours should be paid on an hourly basis, after the expiry of the scheduled time. But the decision had not been honoured by a section of producers. The minister will hold the meeting so that a solution can be arrived at.It may be mentioned that the stand-off between theTollywood artistes andproducers has entered its fifth day on Thursday. Due to the resulting disruption of the shooting schedule, thechannels were forced to go for repeat telecast of the episodes aired earlier.last_img read more

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