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#1 05-12-2018 03:38:31

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Date d'inscription: 23-11-2015
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SAN FRANCISCO Nike Shox Clearance Sale , Aug. 22 (Xinhua) -- New research may explain a gradual lowering of the frequency of blue whale calls documented by scientists for the past two decades, but hardly explains why the largest animals to have ever lived on Earth make the change.


In a study published this week in Scientific Reports, a group of acoustic researchers at Oregon State University (OSU) showed that whales can control the frequency of their calls by blowing air through their vocal cords at a faster or slower rate, in a much different way than previously thought.


Previously Nike Shox Clearance , it was thought that whales generated their calls mostly by resonating sound in large chambers or cavities in their upper respiratory system.


Made possible when the researchers at OSU's Hatfield Marine Science Center recorded a blue whale call, then created a model to replicate that sound based on a series of controlled air bursts from the animal's vocal cords, the new findings imply that the frequency of the whale's calls are dictated by the size of the animal - the lower the frequency, the bigger the animal.


In addition Men's Nike Flyknit Trainer White Gum Clearance , according to Robert Dziak, an acoustics scientist with the National Oceanic and Atmospheric Administration (NOAA) and lead author on the study, the research shows that blue whales can change frequency in the middle of their call, by pulsing air through their vocal cords Men's Nike Vandal High Supreme Obsidian Clearance , and that the change in the frequency might be cognitive, meaning they are choosing to make it higher or lower in response to some sort of environmental stimulus.


Having created similar acoustic models to replicate the sounds of icebergs scraping across the seafloor as well as the explosions from undersea volcanic eruptions, Dziak and his colleagues began to recreate the sound of a blue whale by using a clear call from a blue whale off Yaquina Head near Newport, a city on the central coast of Oregon Men's Nike Air Force 270 Metallic Black Clearance , a state in the U.S. Pacific Northwest, that they recorded using an undersea hydrophone that was part of a study to monitor the environmental impacts of wave energy.


The research group then developed acoustical models of the whale sound and incorporated anatomical respiratory system models of blue whales. "Only when we pulsed air through the process of opening and closing the vocal cords did we get a way to produce sounds that can change frequencies in mid-call as well as remove overtones," Dziak was quoted as saying in a news release from OSU on Tuesday. "And this method produced models that matched the natural Yaquina Head blue whale call very, very closely."


Why the change? Joe Haxel Men's Nike Air More Money Black White Clearance , an OSU acoustics specialist at Hatfield Marine Science Center, speculates that as blue whale populations recover from commercial whaling, there are more of them and the lowering of frequency and other unusual characteristics of the calls are related to changes in population, or that it may be possible the whales are modulating their vocalization frequency in response to an increase in human-generated noise Men's Nike SB Zoom Blazer Low Decon Basketball Light Bone Clearance , essentially trying to find "a radio channel" that has less static to communicate in.


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WASHINGTON Men's Nike Hyperadapt 1.0 JP Team Orange Casual Clearance , Jan. 22 (Xinhua) -- The U.S. government on Wednesday proposed upgrades to its motor vehicle safety standard for child-restraint systems to ensure child passengers are protected in side crashes.


The proposed upgrades would include a first-ever side impact test for car seats sold in the U.S. that are designed for children weighing up to 40 pounds (18 kilograms), said the U.S. Department of Transportation's National Highway Traffic Safety Administration (NHTSA).


"Car seats are an essential tool for keeping young children safe in vehicles and have a proven track record of saving lives," NHTSA Acting Administrator David Friedman said in a statement. " Today we continue to build on our extensive child seat safety program by adding side-impact crash protection for the first time. "


In the proposed test simulating a side-impact vehicle crash, car seats must demonstrate they can safely restrain a child by preventing harmful head contact with an intruding vehicle door and reducing the crash forces transmitted to the child's head and chest.


Under the proposal Men's Nike Hyperadapt 1.0 Triple White Casual Clearance , car seats would be tested in a specially designed sled test that simulates a "T-bone" crash, where the front of a vehicle traveling 30 mph (50 kph) strikes the side of a small passenger vehicle traveling at 15 mph (25 kph).


The sled test is the first of its kind in the world being proposed for regulation, as it simulates both the acceleration of the struck vehicle and the vehicle door crushing toward the car seat, the NHTSA said.


In addition to using an existing 12-month-old child dummy Men's Nike Air More Uptempo Chrome White Clearance , the proposed test will also utilize a newly developed side-impact dummy representing a 3-year-old child.


The agency estimated that the proposal would save five lives and prevent 64 injuries annually.


It proposed a 3-year timeframe for car-seat manufacturers to make any necessary changes to meet the proposed requirements upon final rule publication.


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