“Every solution breeds new problems” laments a Murphyism, and Henry Gee feels the pain. In Nature this week,1 he delved into the growing quandary about where to put the common ancestor of starfish, sea squirts and chordates, including the vertebrates and us human beings. His challenge is to prove the idiot’s sanity:So, if lancelets really are close relatives of echinoderms, what are the implications for our picture of deuterostome evolution? The short answer is that the textbook scheme is turned on its head. Rather than the steady acquisition of progressively more chordate-like (and, by implication, human-like) features from an ancestor with nothing much to recommend it, the story becomes one of persistent loss. The last common ancestor of extant deuterostomes would have been a free-living, bilaterally symmetrical creature with a distinct throat region perforated by gill slits, segmented body-wall musculature and possibly a reasonably sophisticated brain and central nervous system. In a sentence, the ancestor would have looked like a cross between an amphioxus and a larger, brainier, tunicate tadpole larva. Crazy? Possibly. But possibly not. (Emphasis added in all quotes.)Reporting on phylogenetic study by Delsuc et al. from fossils and genetics in the same issue,2 the senior editor at Nature tried to be upbeat about the latest proposal, but called it another exercise in humility. “Time and again,” he preached, “further work has exposed our prejudices for the parochial conceits that they are.” A quote from the paper by Delsuc et al. shares this view, and demonstrates the revolutionary nature of the proposed new phylogeny:The monophyly of Olfactores invalidates the traditional textbook representation of chordate, and even deuterostome, evolution as a steady increase towards complexity culminating in the highly specialized brain of vertebrates. This anthropocentric interpretation is perhaps best reflected by the terms ‘Euchordata’ (that is, ‘true chordates’) or ‘chordates with a brain’, which are used to designate the grouping of cephalochordates and vertebrates. Tunicates should therefore no longer be considered as ‘primitive’ but rather as derived chordates with highly specialized lifestyles and developmental modes. Meanwhile, over in Science Now, Elizabeth Pennisi quoted some other evolutionists not quite ready to accept the new phylogenetic tree. Calling the tunicate an “ugly sister,” Pennisi quoted experts saying the proposal will turn some heads, and the jury is still out. She said they said, “Tunicates and larvaceans evolve rapidly and have gained and lost so many genes that it’s very hard to position them properly in an evolutionary tree.”1Henry Gee, “Evolution: Careful with that amphioxus,” Nature 439, 923-924 (23 February 2006) | doi:10.1038/439923a.2Delsuc et al., “Tunicates and not cephalochordates are the closest living relatives of vertebrates,” Nature 439, 965-968 (23 February 2006) | doi:10.1038/nature04336.Evolutionists could use a lot more humility. They should quit the parochial school of Pope Charlie that is producing a class of lemmings who cling to crazy ideas. What Gee is saying contradicts evolution. This new story line puts the advanced muscles, nervous system and mobility of Amphioxus before organisms that were assumed more primitive (in the old “progressive” evolution picture), and describes subsequent evolution as a story of persistent loss. Meanwhile, Eugenie Scott and Alan Gishlick sit on a Grand Canyon beach trying to whoop up enthusiasm for their evening song service: “It’s a long way from amphioxus / It’s a long way to us. / It’s a long way from amphioxus to the meanest human cuss. / Goodbye fins and gill slits / Hello lungs and hair! / It’s a long, long way from amphioxus, / But we come from there” (10/06/2005 commentary). It’s even longer when you’re going backwards. Gee’s story gives them more food for cuss.(Visited 17 times, 1 visits today)FacebookTwitterPinterestSave分享0
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MOST READ Don’t miss out on the latest news and information. Wilson, Matthew Wright, and Jeff Chan each had 19 points to lead the Fuel Masters while Jason Perkins added 12 points.Scottie Thompson led all scorers with 22 points for theGin Kings to go along 13 rebounds. Read Next Chung limps out of Aussie Open but has eyes fixed on future “It’s a good thing we were able to build a big enough lead,” said Phoenix head coach Louie Alas in Filipino. “I think we were almost too cautious of the lead and that’s the difficult part in a team where you’re still trying to build that winning habit.”Ginebra outscored Phoenix, 29-12, in the payoff period but the Fuel Masters’ lead, which was at 75-53 at the end of third quarter, proved insurmountable.FEATURED STORIESSPORTSWATCH: Drones light up sky in final leg of SEA Games torch runSPORTSLillard, Anthony lead Blazers over ThunderSPORTSMalditas save PH from shutoutThe Fuel Masters snapped a two-game slide for a 3-3 card while sending the Gin Kings reeling to their third straight setback a t2-3 .After slipping to a 26-25 midway through the second quarter, the Fuel Masters pushed the nitrous button and went wild on a 24-3 dash with Willie Wilson scoring six straight to cap it off and give Phoenix a 49-29 lead at halftime. Globe Business launches leading cloud-enabled and hardware-agnostic conferencing platform in PH John Lloyd Cruz a dashing guest at Vhong Navarro’s wedding LATEST STORIES Trending Articles PLAY LIST 00:50Trending Articles00:50Trending Articles00:50Trending Articles01:29Police teams find crossbows, bows in HK university01:35Panelo suggests discounted SEA Games tickets for students02:49Robredo: True leaders perform well despite having ‘uninspiring’ boss02:42PH underwater hockey team aims to make waves in SEA Games01:44Philippines marks anniversary of massacre with calls for justice01:19Fire erupts in Barangay Tatalon in Quezon City Slow and steady hope for near-extinct Bangladesh tortoises Brace for potentially devastating typhoon approaching PH – NDRRMC Ginebra Gin Kings vs Phoenix Fuel Masters. PBA IMAGESBarangay Ginebra’s comeback effort fell short as Phoenix held on to the 87-82 victory Friday in the PBA Philippine Cup at Smart Araneta Coliseum.The Gin Kings went on a blazing 18-6 run in the final 6:33 after falling behind 81-64, but it just wasn’t enough as the Phoenix had a big enough cushion to subdue the “never say die” spirit.ADVERTISEMENT Kammuri turning to super typhoon less likely but possible — Pagasa 2 ‘newbie’ drug pushers fall in Lucena sting Typhoon Kammuri accelerates, gains strength en route to PH NEXT BLOCK ASIA 2.0 introduces GURUS AWARDS to recognize and reward industry influencers View comments
Director Sajid Khan’s Himmatwala remake was a flop and now he blames the film’s failure on his arrogance.”I am a changed man now. I was very arrogant then and I was talking anything to get attention and make statement. Now I am back on track and thank god Himmatwala flopped. In the middle, I lost it completely,” Sajid told reporters during the press conference of his next Humshakals.Sajid Khan’s Humshakals is slated for a June 20 release”I wanted people to respect me as a filmmaker. Heyy Babyy did well, then Housefull did well, so I wanted people to take me seriously. I am glad Himmatwala didn’t work,” he added.Though his Humshakals is yet to hit the screens, it is under scrutiny for being a remake of Comedy Of Errors.But shooting down the reports, Sajid said his film has “nothing to do with that film”.The star cast – Saif Ali Khan, Riteish Deshmukh, Ram Kapoor, Tamannaah Bhatia, Esha Gupta – was present at the event.However, Bipasha Basu skipped the event and Sajid said that she is “unwell”, but she will “attend other events and interviews”.It is being reported that Bipasha will not join the promotional activities of the film.When asked about it, Sajid’s response was that “it’s not true at all. Truth will come out one day. No one can hide it.”Humshakals is slated for a June 20 release.
Many have been waiting for the spring concert of the Community Concert Choir of Baltimore, which will be held at 5 p.m., May 25 at Good Shepherd Baptist Church, 3459 Park Heights Avenue. The group of more than 100 singers will render a program, entitled “Let Me Walk with Thee,” that will feature classically trained musicians, including organist W. Patrick Alston and accompanist Marcus D. Smith, who are Baltimore City Public School music educators at City College High School. “We are committed to preserve the rich music of the Black Church, which is celebrated around the world,” said Marco K. Merrick, the choir’s founding director. “In many churches, you no longer hear these songs, nor is our heritage taught and shared — people hunger for it.” Founded in 2010, the CCC has quickly become a noted musical force in the Baltimore Washington Metropolitan area, garnering standing-room only crowds at its signature concerts each spring and fall. The annual fall concert benefits programs for students in Baltimore City Public Schools and is sponsored by Alpha Phi Alpha, Fraternity, Delta Lambda Chapter. This concert is free and open to the public. A freewill offering will be received during the concert and a reception will be held for everyone in the church’s fellowship hall. For further information, contact Good Shepherd Baptist Church at 410-462-5864 or Dr. Marco K. Merrick at 410-728-4129 or email@example.com
The polymer’s self-healing properties were tested by first cutting it into two pieces and then allowing it to re-from. The authors found that the cut on the polymer film was not discernable after being allowed to “heal” at room temperature for forty-eight hours. The polymer spontaneously healed at low temperatures, -20oC, without the addition of additives that would promote polymerization, something that is unprecedented for an autonomous, self-healing polymer. Finally, the Fe-Hpdca-PDMS polymer showed excellent potential as a model system for artificial muscles. Li, et al. punctured the polymer with a sharp object and marked the area of damage. They then let the polymer self-heal for seventy-two hours. After this time, they applied a square-wave high-voltage signal through electrodes with a high enough potential that the polymer began to deform. However, despite the damage, the polymer did not show a dielectric breakdown, even at the location where it was punctured. This polymer has many properties that make it a compelling model system for an artificial muscle. It displays high stretchability and flexibility. It self-heals and has a high dielectric strength. The polymer can be tuned by changing the ligand-to-metal molar ratio as well as adding functional groups to the ligand, two things that the authors report could be explored in future studies. Image of a stretchable autonomous self-healing polymer. Credit: Zhenan Bao Play Self-healing artificial muscle. Credit: Zhenan Bao The Fe-Hpdca-PDMS polymer showed remarkable mechanical strength, stretchability, and recovery. When the polymer was stretched, then allowed to rest for an hour, and then stretched again, it showed almost full recovery of its original shape. It also showed recovery after a cyclic stress test. When the polymer was subjected to stretching for an hour, it took a little longer to recover and did not quite return to its original state. Notably, the authors report that their polymer can withstand a much higher strain before breaking than typical crosslinked PDMS polymers or reported elastomers. 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. (Phys.org)—Animal muscle needs to be strong enough to endure strain; it must also be flexible and elastic; and it is self-healing. Finding a polymer that has all of these properties has proved challenging. However, researchers from Stanford, Nanjing University, UC Riverside, Harvard, and the University of Colorado have reported the synthesis of an elastomer that mimics the properties of animal muscle. Their polymer, is also stable at room temperature and not sensitive to water. Their work appears in Nature Chemistry. Efforts to create polymers that mimic the properties of biological muscle have come short of being practically useful. Often the bonding involved in making these polymers must be sufficiently strong to serve as actuators, but weak enough for reversible self-healing. Many models, to date, involve hydrogen bonding, but hydrogen bonds are sensitive to water. Li, et al. have, instead, exploited metal-ligand interactions as a way to mimic muscle properties.The ligand 2,6-pyridinedicarboxamide (pdca)binds to Fe(III) via the pyridyl nitrogen and the nitrogen and oxygen on the carboxamides. Two pdca molecules coordinate to one Fe(III) atom through six coordination sites. Two of the sites are strong bonds (the pyridyl), two sites are “medium” strength bonds (the amides), and two are weak bonds (the carboxyl). Calculations of bond strength show that the strong bonds are similar to covalent bonds, while the weak Fe-O bonds are similar to hydrogen bonding. This multi-bonding structure, as it turns out, provides an excellent framework for making an elastomer.The ligand was then tethered to a poly(dimethylsiloxane), or PDMS, polymer backbone. Two of these polymer strands were held together through a coordinated Fe(III) atom. Force calculations of the PDMS-tethered, crosslinked polymer confirmed that by having bonds of multiple strengths next to each other, the weaker bonds can readily break and re-form, which is conducive for stretching and self-healing. But the Fe(III) can remain near the ligand through the stronger coordination sites, allowing for rapid re-formation after unfolding. Explore further 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 Citation: An elastomer that behaves like an artificial muscle (2016, May 3) retrieved 18 August 2019 from https://phys.org/news/2016-05-elastomer-artificial-muscle.html More information: Cheng-Hui Li et al. A highly stretchable autonomous self-healing elastomer, Nature Chemistry (2016). DOI: 10.1038/nchem.2492AbstractIt is a challenge to synthesize materials that possess the properties of biological muscles—strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as −20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl–iron one, and two weaker carboxamido–iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron–ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material. © 2016 Phys.org Researchers create super stretchy, self-healing material that could lead to artificial muscle Journal information: Nature Chemistry