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: The Absolute Chronology and Thermal Processing of Solids in the Solar Protoplanetary Disk, Science, 2 November 2012: Vol. 338 no. 6107 pp. 651-655 DOI: 10.1126/science.1226919ABSTRACTTransient heating events that formed calcium-aluminum–rich inclusions (CAIs) and chondrules are fundamental processes in the evolution of the solar protoplanetary disk, but their chronology is not understood. Using U-corrected Pb-Pb dating, we determined absolute ages of individual CAIs and chondrules from primitive meteorites. CAIs define a brief formation interval corresponding to an age of 4567.30 ± 0.16 million years (My), whereas chondrule ages range from 4567.32 ± 0.42 to 4564.71 ± 0.30 My. These data refute the long-held view of an age gap between CAIs and chondrules and, instead, indicate that chondrule formation started contemporaneously with CAIs and lasted ~3 My. This time scale is similar to disk lifetimes inferred from astronomical observations, suggesting that the formation of CAIs and chondrules reflects a process intrinsically linked to the secular evolution of accretionary disks.Press release Chondrules from the chondrite Grassland, L4. Credit: Wikipedia. Explore further Citation: Researchers use new technique to date CAIs and chondrules (2012, November 2) retrieved 18 August 2019 from https://phys.org/news/2012-11-technique-date-cais-chondrules.html Chondrules younger than thought Journal information: Science © 2012 Phys.org (Phys.org)—Researchers working out of the University of Copenhagen have published a paper in the journal Science in which they claim that a new method of dating chondrules and calcium-aluminum–rich inclusions (CAIs) is more accurate than previous methods. Their dating method produces results that contradict earlier findings that have suggested that chondrules formed up to 2 million years later than CAIs; instead they say, the two materials found in meteorites formed at roughly the same time. Scientists believe that the sun and all of its orbiting bodies formed from a spinning disk approximately 4.6 billion years ago. Theory suggests the sun came first, initially surrounded by a cloud of dust and gas that over time became the planets, comets and asteroids. But for that to happen, some bit of material had to bind together first, and researchers believe two of them – chondrules and CAIs – are still present in modern meteorites. Up till now however, there has been disagreement among researchers regarding the age of such materials found in meteorite samples that have struck the Earth.Prior attempts to measure the age of materials in meteorite samples involved using techniques to discern how much aluminum 26 was present. The thinking was that differences in the levels of the isotope indicated different ages. The problem with this methodology, the new team points out, is that it ignores the possibility that objects forming in different locations might naturally have different amounts of the isotope in them.Their new technique involves isolating small amounts of lead found in a sample and then measuring the isotopic composition of both it and uranium and then calculating the age of the material using the known rate of decay of uranium. Using this method, the team calculated that both materials in a meteorite sample were approximately 4.56730 billion years old. And because their method is so precise they say the error rate of their technique is just 160,000 years.If the new method for calculating the age of chondrules and CAIs is adopted by the scientific community it will likely mean revising some ideas regarding the makeup of the early universe.
Tag: 上海后花园千花 XGEPLs initiative towards a greener future
XGEPL has partnered with Indraprastha Gas Limited (IGL) for the implementation of its green drive in the region of Delhi and NCR, for carrying out conversion of already in-use diesel generators for the existing IGL customers being supplied PNG. In the pilot phase, the company has converted in-use three diesel generators in institutions using Euro IV technology and have been made operational. Apart from contributing to the environment, these gas based gensets would reduce the operational cost by around 40% as compared to diesel run gensets. Also Read – Add new books to your shelfE S Ranganathan, Managing Director, Indraprastha Gas Limited inaugurated first of this gas based 125 KVA genset at General William Masonic Polyclinic at Janpath on March 11, 2019, in the presence of Yash Arora and Vikram Bakshi, Directors of XGEPL. Xpert Gas Equipments Pvt Ltd (XGEPL) primarily deals in the conversion of industrial and residential diesel generators to operate on natural gas. Their working technology is not only modern and advanced but most importantly eco-friendly which makes it the absolute necessity of the hour. Since the usage of diesel gensets is restricted in times of high pollution levels as per Graded Response Plan (GRP), gas based gensets would be an opportunity for housing complexes, commercial as well as industrial establishments for having unrestricted power supply. Also Read – Over 2 hours screen time daily will make your kids impulsiveXGEPL started its conversion of diesel generators primarily utilising the technology imported from Italy, and later on went ahead to develop and design its own in-house technology which is equally efficient and cost effective to the end user. The biggest USP which gives a cutting edge to the conversions of diesel generators carried out by XGEPL is that whereas the existing diesel generators in India are meeting the CPCB-II standards of emission, the diesel generators converted using the in-house technology developed by XGEPL is designed to meet the Euro-IV standards of emission without much compromise to the output power of the generator. This level of operational functioning of the converted diesel generator is not only one of its kind but also latest in the Indian market. Geared with its technical team which possesses the necessary professional expertise, its state-of-the-art technology and partnering with IGL, the company looks forward to a brighter future and huge support in conversion of diesel generators, not only helping its users to run eco-friendly generators, but to some extent help them save on high operational costs. And, in a broader perspective to help Delhi NCR to reduce its related pollution by a remarkable margin.
March 16, 2016 5 min read Free Webinar | Sept. 9: The Entrepreneur’s Playbook for Going Global “When I was 15 or 16, your whole life revolved around saving up money to drive a car,” says David Plouffe, the chief advisor for and a board member at Uber. “Your entire social life revolved around the car. That is changing.”Indeed: Ridesourcing technology companies such as Uber and Lyft are trying to build a future in which the idea of owning a car is a bit nostalgic. For consumers, not owning a car can be a big cost-saver. And for cities, getting more consumers to use shared modes of transportation is a way to decrease congestion.To encourage Americans to detach with their generations-long obsession with car ownership, Uber and Lyft will be working ever more closely to integrate with public transportation systems. The San Francisco-based ridesourcing technology rivals say that means they will have to become the last-mile solution in areas where public transportation is just out of reach.If Uber and Lyft can become an intuitive last-mile solution for consumers, the idea of not owning a car will become a reasonable option. “When you reach that tipping point of three or more shared modes [of transportation] that someone uses, that’s when they get rid of the vehicle, and that is the sort of robust ecosystem that is starting to develop now in major cities and increasingly metropolitan areas and suburban areas,” says Emily Castor, director of transportation policy for Lyft.Related: Transportation ‘Supersharers’ Are Also SupersaversDallas is a front-runner in the integration of ridesourcing technology with local public transportation in the U.S. Within the Dallas-metro area, it’s seamless for a customer to book a ride for the first or last mile of a trip on the public transit system. While Portland doesn’t have the same system integration as Dallas, one out of every four Uber trips begins or ends at a local rail station, says Plouffe. In Washington, D.C., 60 percent of Uber trips are within a quarter mile of a metro station, he adds. Uber and Lyft say that they do not compete with public transportation networks. Instead, the companies need to work with regional mass transit. “This is a huge opportunity for public-private collaboration,” says Castor.Overwhelmingly, people use ridesourcing technology platforms such as Uber and Lyft when public transportation is not otherwise available. “There was a clear peak in ridesourcing demand between 10 p.m. and 4 a.m. on weekends,” says Michael Melaniphy, the president and CEO of American Public Transportation Association, the national public transit advocacy group. The trend held across all seven cities that were surveyed for the report: Austin, Boston, Chicago, Los Angeles,San Francisco, Seattle and Washington D.C. “This is the time of greatest demand overall and public transit is often unavailable in those hours.”Related: Alcohol Drives Use of Uber and LyftPublic transportation is still cheaper than ordering an Uber or Lyft in many instances. “Five bucks gets you all of our system all day. That’s a pretty good deal. Even our ridesharing colleagues can’t match that,” says Morgan Lyons, assistant vice president for community engagement for the Dallas Area Rapid Transit, chuckling to the Uber and Lyft representatives. “And so folks like to use that.”As more and more regional transportation systems bring their public transportation ticketing systems online, that will facilitate the integration of public transportation systems with Uber and Lyft. To goal is for a consumer to be able to book a ride that involves a combination of public transportation and ridesourcing through a single app. Castor, Plouffe, Lyons and Melaniphy were speaking on a conference call with reporters timed to the release of a report on that very topic, titled “Shared Mobility and the Transformation of Public Transit.” This new research paper is by the public-interest advocacy group, Shared-Use Mobility Center, released this week on behalf of American Public Transportation Association, and paid for with money from the Federal Transit Administration.“Instead of needing to use a physical fare card, already in many cities, like Dallas, you can pay for your transit ticket on an app, and that really is important for our ability to create partnerships with transit because that brings them into our world,” says Castor. “It brings them into the world of technology-based transportation services where we can become increasingly interoperable.”Related: This New App Lets You Summon Your Grandma (or Tinder Date) Via a Prepaid Uber RideTransforming the transportation networks in the U.S. will take more than just interoperable technology, though. It also depends on a shift in user behavior.“Where we would like to see this go is that you have just got neighbors driving neighbors,” says Plouffe. The average Uber driver clocks fewer than 10 hours per month and that average is going to continue to decline. “Our view is that over the next few years, you are not even going to think about becoming an Uber driver. You are just going to say, ‘I am going to turn on my car, turn on my phone and if I can pick up someone along the way, that’s what I am going to do.’”To be sure, that’s a reality that Uber would benefit from. But while improving technology and making networks integrated is a virtual given, changing consumer behavior is a far slower, more unpredictable art. Growing a business sometimes requires thinking outside the box. Register Now »