Despite its importance for the evolution and final end states of stars, the physics of stellar angular momentum transport remains poorly understood. Recent advances in ensemble asteroseismology has yielded measurements of core rotation in many ascending red giant branch stars (RGB) . The main result (Fig [period]) is that the cores of these stars are rotating at least 10 times slower than what is predicted by state-of-the art models . Moreover, detailed asteroseismic modeling shows that the bulk of radial differential rotation is localized in the radiative region between the H-burning shell and the bottom of the convective envelope . The magnetorotational instability (MRI) has been extensively studied in the context of angular momentum transport in accretion disks. However, it is not clear what role–if any–it might play in the radiative regions of differentially rotating stars. The existing literature is limited , and attempts to simulate this mechanism in stellar interiors have not yielded complete results appropriate for inclusion in stellar evolution codes. We propose to investigate the role of the MRI in stars using simulations that account for the important physical ingredients of stellar radiative regions: stable radial stratification, mean molecular weight gradients, differential rotation, and magnetic fields. These effects are parameterized by the Brunt-Väisälä frequency N, background gradient ∇μ, shear parameter q = dlogΩ/dlogR, and plasma β. emphasized the importance _double-diffusive_ effects in the stellar MRI. These effects occur when there is an imbalance between the microphysical dissipation of momentum ν, magnetic field η, and heat χ. In their analysis, they note that double diffusive effects can both stabilize and destabilize depending on the relative ratio of these coefficients. Here, we will carefully consider the effects of double-diffusive effects by a series of fast, linear solutions to characterize the parameter space most relevant to stellar parameters. Using the Dedalus framework, we will simulate the MRI in a simplified geometry to extract effective torques over a range of parameters. We will then implement these results in a 1D implementation in the MESA code to test against the full set of observations available: the core rotation of red giants, the solar core rotation profile, and the final spin rate of compact remnants. This project is extremely ambitious owing to the many length scales that must be resolved simultaneously and the very large parameter space to be spanned. However, we have at our disposal the ideal tools to make significant progress: the spectral magnetohydrodynamic simulation framework Dedalus and the extremely flexible stellar evolution code MESA. Dedalus provides an excellent platform to study the MRI in stellar interiors: it can be adapted to include the new terms and its spectral accuracy ensures that the widest possible dynamic range for a given resolution (Fig. [Dedalus]). Thanks to the extraordinary results from Kepler asteroseismology and the versatility of the open stellar evolution code MESA, we will be able to immediately test our results against the observations. This project could lead to a novel theory for internal angular momentum transport in stellar interiors, and, among other results, to updated predictions for SN and GRB progenitors. Both the Dedalus and MESA codes are fully open, so our results will be fully testable and reproducible by the astrophysics community. We will publish not only our results, but also our input files and configuration for both codes.
The Hubble image of the Bubble Nebula (NGC 7635) is the official image celebrating the 26th anniversary of Hubble's launch into Earth orbit's. Since 1990 Hubble has been capturing awe-inspiring images of the Universe. Floating about 350 miles above the Earth, the Hubble Space Telescope (HST) is able to take high-resolution images free of the image-distortion that occurs due to atmospheric turbulence. Hubble performs a full orbit around the Earth approximately every 95 minutes, and since its launch has completed 1.2 million observations. Among its many accomplishments, HST helped scientists determine the rate of expansion of the Universe.
CERN's 2008 Large Hadron Collider is not just the world's largest and most powerful particle collider but also the largest single machine and most complex experimental facility. Here, physicists are able to test fundamental physics theories by smashing particles with extremely high energies. On 8 October 2013 the Nobel prize in physics was awarded jointly to François Englert and Peter Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider."
Thomas Edison has an impressive 2,332 worldwide patents. Some of his well-known inventions include the phonograph, motion pictures, and the magnetic iron ore separator. After the success of his first major invention, the quadruplex telegraph, Edison wanted to build his own laboratory so that he could continue to innovate. In 1875, he purchased around 34 acres in Raritan Township, NJ and built the "Invention Factory". By Spring 1876, the Invention Factory consisted of a main laboratory, ancillary buildings, a carpenters’ shop, carbon shed, and blacksmith shop. His first breakthrough at the Invention Factory, the phonograph, produced the first voice recording (“Mary Had a Little Lamb”) and earned Edison the title, “The Wizard of Menlo Park”.
Last Thursday, September 22nd, we held our 5th New York open science meetup (#opensciencenyc). Science journalists, Columbia faculty members, and enthusiasts from our open science meetup group came out to hear Dr. Stuart Firestein talk about ignorance in scientific research and why it is necessary and valuable (yes, you read that right).
Retraction Watch is a blog that tracks retractions in science -- and it's probably a site you never want your research to be on. To many, retracting your work means that you've committed fraud, and in most cases can be the end of a researcher's career. However, that's not always the case: in fact, retracting your work for the right reasons can even be good for your career and good for science (Lu 2013). Retraction Watch highlights cases where scientists did not retract their work due to fraud, but rather because it was "the right thing." Here we take the opportunity to further highlight these pieces and the courageous scientists that did the right thing despite an enormous stigma.We believe the future of scholarly communication will be more dynamic than it is today. By definition, this will require more corrections and retractions. Authorea was built to show the full history of a document, from creation to final publication. We allow annotations of the literature and believe that a more dynamic and robust form of communication is the future -- it's what we're building. Join us!
How researchers communicate with one another and the world has changed very little over the last 350 years. Attempts to improve the process have been implemented throughout the years, not all of which have been to the benefit of research. Here we highlight some policies implemented by various publishers that we believe are antithetical to research communication and what we're doing to try to fix them.
Peer review is arguably necessary for effective communication amongst researchers. Authors, editors, and the public rely on peer review to ensure a first measure of trust in scientific communication. While peer review is considered to be integral in scholarly communication by most, its shortcomings are becoming evident. Former editor of JAMA and NEJM Drummond Rennie once said, "if peer review was a drug it would never be allowed onto the market." Is this true? Does peer review, as it is done today, cause more harm than good?
The web was built specifically to share research papers amongst scientists. Despite this being the first goal of the modern web, most research is still published behind a paywall. We have recently highlighted famous math papers that reside behind a paywall as well as ten papers that have achieved a near rockstar status in research and the public. Here we systematically look at the top one hundred cited papers of all time and find that 65% of these papers are not open. Stated another way, THE WORLD’S MOST IMPORTANT RESEARCH IS INACCESSIBLE FROM THE MAJORITY OF THE WORLD. A few facts about the top 100 cited papers: 1. The weighted average of all the paywalls is: $32.33, rounding to the nearest cent. 2. There are 1, 088, 779 citations of the Open Access articles, so, if they cost the same on average as the Paywalled articles and were paid for individually, they would cost a total of: $35, 199, 108.44–that’s 14 Bugatti Veyrons, or enough to buy everyone in New York City a Starbucks Tall coffee and chocolate chip cookie. In comparison, the total amount for the paywalled articles, assuming everyone bought the paywalled articles individually, is $54, 722, 252.80. 3. That’s 23 Bugatti Veyrons, or enough to buy everyone in New York City a footlong from Subway. 4. Although 65% of the most cited papers are paywalled, only 61% of those paper’s citations are from paywalled journals. Thus the open access articles in this list are, on average, cited more than the paywalled ones.
What better way to argue for the benefits of open access than to publish a research paper with restricted access rights? While open access has been shown to be beneficial for researchers and the public by numerous studies (some of which are listed below), these same papers make it pretty self-evident that the move to full open access is going to take some time. It is true that more and more open access articles appear each year -- some predict that the volume of open access publications will overtake subscription publications by 2018 -- yet despite the increase in publishers and researchers adopting open access as a modus operandi, paywalls still remain on the vast majority of articles, including many which tout the benefits of open research. The following is a list of articles that while advocating for open research remain, ironically, behind paywalls:
Some research findings have permeated all parts of our culture -- so much so that we often take the actual ideas and access to them for granted. Would you believe that Einstein's "Does the Inertia of a Body Depend Upon Its Energy Content?" remains behind a paywall, despite being more than 100 years old? Here we show 10 famous papers that have achieved a similar "rockstar" status in the public imagination yet are still subject to paywalls. At Authorea, we believe that open communication is the key to advancing research. We're working every day to make it possible for researchers to have full control over their work and its dissemination.
Scholarly communication is advancing culturally and technologically towards a better future. There are an increasing number of disciplines and people publishing their content under open-access licenses, publishing their work as preprints, and publishing different types of content from data to posters to single figures. We're happy to be part of this push towards a more dynamic and transparent system of communication. In fact, it's one of the reasons we exist--to improve how leading researchers and student's alike communicate their ideas amongst each other and to the world. These are the world's most important ideas, how we communicate them is important.
The 2016 Olympics have captivated the world -- records are breaking, medal counts are climbing, and nationalism is roaring! It's all very exciting. It should get even more exciting in Tokyo in four years time at the 2020 games when several new sports are scheduled to be introduced, including surfing, skateboarding, and... research! Okay, research definitely won't be included, but what if it were? How would each country fare? Here we look at research output vs. Olympic prowess on a per-country basis.
During the night of August 11th, a meteor shower called ’Perseids’ might put up a memorable show. After the moon sets, which occurs around 1:00 AM local time, it might be possible to see up to 200 ’shooting stars’ per hour. Below, what you need to know about this astronomical event. WHAT IS A SHOOTING STAR? Despite their name, shooting stars are actually small rocks (meteoroids) falling towards the Earth due to our planet’s gravitational attraction. As they move rapidly through the atmosphere, they reach very high temperatures due to friction with air particles. This makes them burn and become visible to the human eye. The trail they leave is called ’Meteor’. Due to their tiny size, they usually almost completely burn in a fraction of a second. In some very exceptional cases, large meteors can continue the hot descent and hit the ground. If they also survive the crash, they get promoted immediately to the ’meteorites’ class. Generally speaking a meteoroid producing a meteor needs to be at least as large as a marble to reach the Earth and eventually become a meteorite. Some Burning facts: - Average meteorite velocity: 30000 miles/hour (48000 km/h) - Max temperature: 3000 F (1650 C) - The Meteor Crater in Arizona was formed 50000 years ago by an object 160 feet (50 meters) across - ... yes, impacts like the one that produced the Meteor Crater are extremely rare
如果您正在寻找基于网页的 LaTex 编辑器,Authorea 应该是您一个不错的选择。Authorea 是一个强大的在线 LaTeX 编辑器,并拥有很多强大的功能,包括立即可用的模板,方便合作的工具,文档更改历史记录,聊天功能,自动创建参考文献,方便插入图像,链接,表格等。 Authorea 还支持多种文件格式,包括 LaTeX,HTML,Markdown 等等。索引页面的创建,导出文件为 PDF,在社交媒体上分享,支持的平台:基于网页的,支持所有主流浏览器。快速编辑,打开/关闭评论,字数统计,这些都是 Authorea 能够提供的一些主要功能。这也是为什么它能成为 LaTeX 最好的的编辑器之一,使你能方便地用你最喜欢的浏览器做 LaTeX 编辑。Authorea 使得插入数学公式,图像和表格变得非常简单。总而言之,这些功能使得 Authorea 是一款简单易用的 LaTeX 编辑工具,你不需要花费很长时间就能学会使它。主要功能:非常容易插入图像,数学公式,表格和其它对象,合作,引用文章,自动创建参考文献,评论功能,可互动的图像,可插入 Ipython/Jupyter 文本。支持的平台:基于网页的,支持所有主流浏览器。
Social media is generally discouraged in science today. A recent article, "I'm a serious academic, not a professional Instagrammer" castigated scholars with active online social lives. Most advisors won't ask you to "tweet out our paper" or "write a blog post about our findings" and it's likely that you'd close Twitter or Reddit if your colleague or advisor walked by. Some conferences have taken it so far as to enforce a "no tweeting" policy. But social networking is here to stay and will likely become even more integrated into our lives and research.