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Thursday, April 12, 2012
Fab Sale: Free Shipping at Little Skye Children?s Boutique
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Google Currents app updated with international support, offline reading
Google Currents app updated with international support, offline reading originally appeared on Engadget on Wed, 11 Apr 2012 17:06:00 EDT. Please see our terms for use of feeds.
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Bats save energy by drawing in wings on upstroke
ScienceDaily (Apr. 11, 2012) ? Bat wings are like hands: meaty, bony and full of joints. A new Brown University study finds that bats take advantage of their flexibility by folding in their wings on the upstroke to save inertial energy. The research suggests that engineers looking at flapping flight should account for wing mass and consider a folding design.Whether people are building a flying machine or nature is evolving one, there is pressure to optimize efficiency. A new analysis by biologists, physicists, and engineers at Brown University reveals the subtle but important degree to which that pressure has literally shaped the flapping wings of bats.
The team's observations and calculations show that by flexing their wings inward to their bodies on the upstroke, bats use only 65 percent of the inertial energy they would expend if they kept their wings fully outstretched. Unlike insects, bats have heavy, muscular wings with hand-like bendable joints. The study suggests that they use their flexibility to compensate for that mass.
"Wing mass is important and it's normally not considered in flight," said Attila Bergou, who along with Daniel Riskin is co-lead author of the study that appears April 11 in the Proceedings of the Royal Society B. "Typically you analyze lift, drag, and you don't talk about the energy of moving the wings."
The findings not only help explain why bats and some birds tuck in their wings on the upstroke, but could also help inform human designers of small flapping vehicles. The team's research is funded by the U.S. Air Force Office of Sponsored Research.
"If you have a vehicle that has heavy wings, it would become energetically beneficial to fold the wings on the upstroke," said Sharon Swartz, professor of ecology and evolutionary biology at Brown. She and Kenneth Breuer, professor of engineering, are senior authors on the paper.
The physics of flexed flapping
The team originally set out to study something different: how wing motions vary among bats along a wide continuum of sizes. They published those results in 2010 in the Journal of Experimental Biology, but as they analyzed the data further, they started to consider the intriguing pattern of the inward flex on the upstroke.
That curiosity gave them a new perspective on their 1,000 frames-per-second videos of 27 bats performing five trials each aloft in a flight corridor or wind tunnel. They tracked markers on the bats, who hailed from six species, and measured how frequently the wings flapped, how far up and down they flapped, and the distribution of mass within them as they moved. They measured the mass by cutting the wing of a bat that had died into 32 pieces and weighing them.
The team fed the data in to a calculus-rich model that allowed them to determine what the inertial energy costs of flapping were and what they would have been if the wings were kept outstretched.
Bergou, a physicisist, said he was surprised that the energy savings was so great, especially because the calculations also showed that the bats have to spend a lot of energy -- 44 percent of the total inertial cost of flapping -- to fold their wings inward and then back outward ahead of the downstroke.
"Retracting your wings has an inertial cost," Bergou said. "It is significant but it is outweighed by the savings on the up and down stroke."
The conventional wisdom has always been that bats drew their wings in on the upstroke to reduce drag in the air, and although the team did not measure that, they acknowledge that aerodynamics plays the bigger role in the overall energy budget of flying. But the newly measured inertial savings of drawing in the wings on the upstroke seems too significant to be an accident.
"It really is an open question whether natural selection is so intense on the design and movement patterns of bats that it reaches details of how bats fold their wings," Swartz said. "This certainly suggests that this is not a random movement pattern and that it is likely that there is an energetic benefit to animals doing this."
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The above story is reprinted from materials provided by Brown University.
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Journal Reference:
- D. K. Riskin, A. Bergou, K. S. Breuer, S. M. Swartz. Upstroke wing flexion and the inertial cost of bat flight. Proceedings of the Royal Society B: Biological Sciences, 2012; DOI: 10.1098/rspb.2012.0346
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.
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Fitness is More than Just Exercising But You Can't Get Fit Without it ...
Everyone can get fit. There is no reason that you shouldn?t be able to get reasonably fit if you are patient and willing to do the work involved to change. More and more people are concerned with their health every year. Take a moment and think: how much do you think something like ?I really need to be healthier?? How many times do you think to yourself ?I need to exercise more?? Health and fitness are very real concerns all over the world. If you have been thinking about trying to get fit, here are a few hints that can help you out. Also, in case you?re interested, an effective way to build some additional muscle is with Bodylastics bands.
Work your entire body. Don?t listen to people who tell you that you only have to concentrate on the parts of your body that you want to improve. To be successful you will need to put together a routine that will work your whole body and all of its systems. You will need to train in endurance, strength and cardiovascular systems. All of your muscles need to be worked on if you really want to make your body healthy. Concentrating on just a few areas will only ?beef up? those same areas which will make you feel bigger than you felt before you started working out.
Seek help from a personal trainer. By now you are probably flirting with the idea of joining a gym or might have even already joined one. Your gym probably has a personal trainer on hand to help you put together and perfect a workout routine that you can use to increase your fitness. Your personal trainer will teach you how to use the machines and gym equipment, tell you which fitness classes you should take and help you decide just how much time you should be spending working out each day. Perhaps most importantly of all, a personal trainer will cheer you on when you need it. Putting together an exercise routine of your own can be scary. A great confidence booster is working with someone who is not only well versed in fitness but who is also very interested in seeing you succeed.
Use Wii Fit! Whether or not you want to believe it, this game is a godsend for people just starting out on the road to fitness. You can use this game to get in a full exercise routine right in your living room. It also teaches you some basic maneuvers so that, if you do decide to move to a public space to do your workout, you will have some knowledge under your belt. Working out in public is something that scares many people. Wii Fit helps you avoid this problem.
Getting in a full fitness routine has never been easier. Even if you don?t like the idea of Wii Fit there are plenty of other options available on the Wii system.
Fitness involves your whole life. There is more to fitness than going for a jog a few times a week. Fitness involves a healthy diet, healthy choices and a regular exercise routine. You have lots of options when it comes to finding success at fitness. Don?t forget that there is more to fitness than simply working out on a regular basis! Before you go, be sure to read our Bodylastics review.
Tags: build muscle, exercise, fitness
Posted in weight loss
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Santorum cancels events after daughter discharged from hospital
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Cash boost in bee parasite fight
11 April 2012
Last updated at 03:29 ET
Scientists are to try to turn a honey bee parasite's natural defences against itself in a bid to beat the pest.
University of Aberdeen researchers have won ?250,000 to study how to subvert the varroa mite's immune system.
The blood-sucking varroa mite is endemic in many honey bee colonies and saps the vitality of a hive if present in large numbers.
Novel ways to tackle varroa are needed because mites are becoming resistant to existing chemical treatments.
The cash will be used to extend a completed study that showed how to target specific genes used by the mite.
Potential targetsSo far, said Dr Alan Bowman of the University of Aberdeen who is leading the project, this "knock-down" approach has only been used to home in on non-lethal genes.
"The next step is to continue finding which are the best genes that will kill them quickly at very low doses and then we'll move on out to field trials in greenhouses," said Dr Bowman.
The knock-down technique attempts to trick part of the bug's immune system into thinking that one of its genes is a virus.
Typically the part of the immune system being subverted only tackles external threats in the form of a certain types of RNA-based viruses.
Continue reading the main story?Start Quote
End Quote Dr Alan Bowman University of AberdeenResistance to a single treatment can often develop quite quickly?
As active genes also use RNA, it should be possible to subvert this defence mechanism by making it think one of the genes keeping the mite living is actually an invader.
Varroa mites' genomes are being sequenced to discover which genes are being actively expressed and are potential targets.
Dr Bowman hoped to have identified likely genes by the autumn and to start small-scale trials in 2013.
Beekeepers are being asked to send in live varroa mites so the researchers have a stock of bugs on which to test candidate treatments.
Dr Bowman said it was unlikely that the research would produce a treatment that would completely rid hives of the pest.
"I do not think we are expecting any silver bullets and it's probably the wrong approach to look for them these days," he said. "It'll be another piece in the arsenal and at the moment it's a very small arsenal."
Max Watkins, technical director of Vita Europe, which is providing some of the research money, said finding treatments that kill mites but leave bees and the environment unharmed was very difficult.
"The challenge is heightened because the relatively short life cycle of the varroa mite means that resistance to a single treatment can often develop quite quickly," he said.
Honey bees, solitary bees and bumble bees play a hugely important role in pollinating crops, said Friends of the Earth as it kicked off its Bee Cause campaign.
The pressure group estimates that it would cost the UK about ?1.8bn a year to hand-pollinate crops if all bees died out.
It has called on David Cameron to back a national bee action plan that would limit urban expansion and pesticide use.
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Wednesday, April 11, 2012
What triggers a mass extinction? Habitat loss and tropical cooling were once to blame
ScienceDaily (Apr. 10, 2012) ? The second-largest mass extinction in Earth's history coincided with a short but intense ice age during which enormous glaciers grew and sea levels dropped. Although it has long been agreed that the so-called Late Ordovician mass extinction -- which occurred about 450 million years ago -- was related to climate change, exactly how the climate change produced the extinction has not been known. Now, a team led by scientists at the California Institute of Technology (Caltech) has created a framework for weighing the factors that might have led to mass extinction and has used that framework to determine that the majority of extinctions were caused by habitat loss due to falling sea levels and cooling of the tropical oceans.
The work -- performed by scientists at Caltech and the University of Wisconsin, Madison -- is described in a paper currently online in the early edition of the Proceedings of the National Academy of Sciences.
The researchers combined information from two separate databases to overlay fossil occurrences on the sedimentary rock record of North America around the time of the extinction, an event that wiped out about 75 percent of marine species alive then. At that time, North America was an island continent geologists call Laurentia, located in the tropics.
Comparing the groups of species, or genera, that went extinct during the event with those that survived, the researchers were able to figure out the relative importance of several variables in dictating whether a genus went extinct during a 50-million-year interval around the mass extinction.
"What we did was essentially the same thing you'd do if confronted with a disease epidemic," says Seth Finnegan, postdoctoral scholar at Caltech and lead author of the study. "You ask who is affected and who is unaffected, and that can tell you a lot about what's causing the epidemic."
As it turns out, the strongest predictive factors of extinction on Laurentia were both the percentage of a genus's habitat that was lost when the sea level dropped and a genus's ability to tolerate broader ranges of temperatures. Groups that lost large portions of their habitat as ice sheets grew and sea levels fell, and those that had always been confined to warm tropical waters, were most likely to go extinct as a result of the rapid climate change.
"This is the first really attractive demonstration of how you can use multivariate approaches to try to understand extinctions, which reflect amazingly complex suites of processes," says Woodward Fischer, an assistant professor of geobiology at Caltech and principal investigator on the study. "As earth scientists, we love to debate different environmental and ecological factors in extinctions, but the truth is that all of these factors interact with one another in complicated ways, and you need a way of teasing these interactions apart. I'm sure this framework will be profitably applied to extinction events in other geologic intervals."
The analysis enabled the researchers to largely rule out a hypothesis, known as the record-bias hypothesis, which says that the extinction might be explained by a significant gap in the fossil record, also related to glaciation. After all, if sea levels fell and continents were no longer flooded, sedimentary rocks with fossils would not accumulate. Therefore, the last record of any species that went extinct during the gap would show up immediately before the gap, creating the appearance of a mass extinction.
Finnegan reasoned that this record-bias hypothesis would predict that the duration of a gap in the record should correlate with higher numbers of extinctions -- if a gap persisted longer, more groups should have gone extinct during that time, so it should appear that more species went extinct all at once than for shorter gaps. But in the case of the Late Ordovician, the researchers found that the duration of the gap did not matter, indicating that a mass extinction very likely did occur.
"We have found that the Late Ordovician mass extinction most likely represents a real pulse of extinction -- that many living things genuinely went extinct then," says Finnegan. "It's not that the record went bad and we just don't recover them after that."
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The above story is reprinted from materials provided by California Institute of Technology. The original article was written by Kimm Fesenmaier.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.
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