Every school child has seen artwork of planets evolving from a disk of dust and gas around a star like our sun, but there’s a missing link in the story. How did the dust particles stick together?Once a clump of material is massive enough, it can attract more material by its own gravity. The moon, for instance, pulls meteors in. They stay there and don’t bounce off, except in the unusual case of a high-speed glancing blow. From the well-understood law of gravity, a planetary body needs to be about 1-10 km in diameter to grow by accretion. From there, this “planetesimal,” according to theory, would experience runaway growth as long as there is material around to feed it. Getting the body to this size is the problem. Smaller bodies do not have sufficient gravity to pull in neighboring material. A disk around a star, however, starts out with dust and ice grains much smaller, even microscopic in size. It is estimated that the original dust particles in the primordial solar nebula were a tenth of a micrometer in diameter, too small to see. How could these grow into planetesimals a mile across?This problem is not new. Planetary evolutionists have wrestled with it repeatedly. In the February issue of Icarus,1 Sin-iti Sirono of Nagoya University, Japan, tries to identify the requirements for colliding particles to stick together rather than bounce or smash each other apart. He certainly respects the problem; in his introduction, he asks with a Japanese accent, “There is a immense gap of 13 orders of magnitude between the grain size and the size of a planet. How planets are formed across this gap?” Behold the missing link of planetary evolution.Accretion is a complex problem with many variables. Think of firing a bullet at a rock. A small bullet might form a crater, catastrophically disrupt the rock, or merge with the rock, if the rock is porous and able to absorb the blow. What physical laws govern the outcome? Sirono, after a great deal of modeling and computation, arrives at three constraints:The target must have low compressive strength relative to shear strength and tensile strength.Impact velocity must be 0.4% the speed of sound of the medium.The bodies must be made of materials that allow the “restoration of damage” effect. This is an automatic “repair” mechanism that occurs if a ruptured material can rebound such that interatomic forces can partially heal the breach, as if little magnets in the pieces pull them back together.It should be evident with a little thought that other variables can also be important. To visualize this, imagine two astronauts, Chuck and Tom, having a snowball fight in the cargo bay of a space shuttle. Let’s say they both have good timing and aim; they always make their snowballs collide in the space between them. Since gravity is not a factor in the weightlessness of space, what factors would make the snowballs stick together (accrete) instead of bouncing off each other or fragmenting into smithereens? Here are a few of the variables:Temperature. Soft, wet snowballs are more likely to stick than hard, icy ones.Density. Low-density snowballs are more likely to stick than packed ones. The compressive strength of snowballs can vary by a factor of 1000, Sirono says: “As the density of an aggregate goes lower, the strength becomes lower and vice versa. For example, the strength range due to density variations is more than three orders of magnitude for a bed of snow.” So if our astronauts tightly pack their snowballs, they well be less likely to stick, but also more subject to disruption.Relative size. A small snowball might stick more readily to a large one, than would two of equal size. Sirono’s simulations suggest that the threshold ratio for optimum chance of sticking is 3/10 or lower.Glancing angle. A small impactor is more likely to stick to a target in a direct bulls-eye hit rather than a glancing blow.Differentiation. Let’s say Chuck and Tom throw rocks coated with snow. They might accrete if the relative velocity is low and the snow coating absorbs some of the energy.Glue. If our astronauts have access to some kind of adhesive with which to saturate their weapons, the snowballs might glue themselves together. Sirono thinks interstellar organic molecules might just do the trick. He cites earlier work that suggests organics might comprise a significant fraction of the material (silicate:ice:organic mass ratio of 1:1:1.6), and that the organics might form a viscoelastic fluid between the particles. “It may be possible that the organic materials play a role of glue which connects grains and fragments,” he suggests.If our astronauts perfect the art of getting their snowballs to stick together, new problems arise as the wad of snowballs grows. Earlier models often assumed that the properties of an accreting mass scaled uniformly upward, but Sirono reminds us that the aggregate of particles is subject to new forms of catastrophic rupture. Sirono explains,There are voids and cracks inside a large aggregate that significantly lowers the strength of an aggregate. Tensile stress concentrates in regions around the cracks, and fracturing starts from contacts between such grains. An aggregate will be broken by much smaller stresses than those expected by direct extrapolation from interaction forces between grains.So until the aggregate is large enough for gravity to compress and homogenize the insides, it is even more subject to disruption than were the original starting grains. Even if a lucky aggregate forms, all Tom needs to do is lob a high-speed ice ball at it and it could splinter into small fragments again. Better luck next time.It seems, therefore, that many special conditions are required to keep the hopeful aggregate growing up to a size where gravitational accretion can take over. Sirono does not estimate how likely this is to occur in a real stellar nebula. He just points out that any accretion needs to obey the laws of physics.1Sin-iti Sirono, “Conditions for collisional growth of a grain aggregate,” Icarus Volume 167, Issue 2, February 2004, Pages 431-452, doi:10.1016/j.icarus.2003.09.018.Observation 1: planets around a star, with a little dust. Observation 2: a lot of dust around a star, with no planets. What are appropriate conclusions based on this data?There are two possibilities. One is that the second star is a young star with a dust disk that is on the way to becoming a new solar system, and the first is an old star with mature planets. But there’s another possibility. Maybe the first star has widely spaced, mature planets with stable orbits and few collisions, and the second star started out with mature planets in erratic orbits, which since collided and ground each other to dust. The conclusion you reach has a lot to say about your world view and your respect for observation.While no one can rule out all possibility of dust and ice grains sticking together, the probability seems rather low. Sirono invokes several ad hoc conditions to increase the odds. Maybe if they are as soft as silly putty and infused with some sort of organic glue, with the right angle of attack, slow enough collision speed and the right temperature, they just might stick instead of bouncing off each other. But the organic glue cannot get too warm, because Sirono says, “It has been found that the shear modulus of the organics decreases by five orders of magnitude as temperature increases from 200 to 300 K.” This means the glue loses its elasticity real fast as the temperature rises: “The consequence of decrease in elasticity by a factor of 10 is severe fragmentation,” he says. For particles in the warmer parts of the nebula, this seems to be a problem, yet we observe Mercury in our solar system baking in the heat of the sun, and gas giants bigger than Jupiter in even closer orbits around other stars. Also, even if the conditions are lucky enough for the particles to start sticking to each other, they become even more subject to disruption as the aggregate grows.Perhaps Sinoro’s constraints don’t seem too outlandish, and one can envision scenarios in which all the right conditions might be met. It could be argued that out of uncounted myriads of particles, some might reach the threshold of runaway gravitational accretion. All it takes is a few to get a planetary system, right? (Actually, our solar system is filled with many thousands of gravitationally accreting bodies, like asteroids, Kuiper Belt objects, comets, and small moons, in addition to the planets and larger moons. Some of them appear to have been busted apart by collisions.)Regardless, the fact remains that no one has observed grains accrete into a planetesimal, but astronomers have abundantly observed the opposite: bodies fragmenting into smaller bodies and dust. Small bodies show abundant evidence of cratering and erosion, even the recently-photographed comet Wild-2 (see 01/02/2004), a fact that surprised scientists because this was supposed to be a pristine object from the quiet deep freeze of the outer solar system. We observe ongoing processes of fragmentation, catastrophic collision, erosion to dust and de-evolution, but accretion exists only in the minds of theorists. Which principle is more in accord with the second law of thermodynamics?One would think that scientists would err on the side of conservatism, and not make claims beyond the evidence. But the disruption view implies starting conditions that are philosophically repugnant to a naturalist: if the planets were already there, they must have been created. So strong is the urge to have a universe that evolves upward from a bang to galaxies to planets to life, that philosophical naturalists will sneak glue and fudge and whatever else is needed to fill in the gaps. You can believe that the dust around Vega is a young solar system in the making, but be sure your model particles obey the laws of physics. After all, a naturalist should respect the laws of nature, by definition. Better yet, perform realistic lab experiments. We’ll wait till you get particles that stick before worrying you with all the other problems, such as the Kuiper capers (10/05/2003), small moon mysteries (09/29/2003), turbulent stress in planetesimals and in scientist minds (09/22/2003), the rarity of sunlike solar systems (07/21/2003), declining popularity of the planetesimal hypothesis (06/03/2003), migration woes (05/16/2003), the war of the worlds (04/17/2003), the tweak Olympics (11/22/2002), etc., and so forth, and so on.(Visited 41 times, 1 visits today)FacebookTwitterPinterestSave分享0
Many evolutionists use software tools to construct evolutionary trees from genetic data. Two mathematicians have just reported in Science1 that several popular “tree-building” algorithms can give misleading results:Markov chain Monte Carlo (MCMC) algorithms play a critical role in the Bayesian approach to phylogenetic inference. We present a theoretical analysis of the rate of convergence of many of the widely used Markov chains. For N characters generated from a uniform mixture of two trees, we prove that the Markov chains take an exponentially long (in N) number of iterations to converge to the posterior distribution. Nevertheless, the likelihood plots for sample runs of the Markov chains deceivingly suggest that the chains converge rapidly to a unique tree. Our results rely on novel mathematical understanding of the log-likelihood function on the space of phylogenetic trees. The practical implications of our work are that Bayesian MCMC methods can be misleading when the data are generated from a mixture of trees. Thus, in cases of data containing potentially conflicting phylogenetic signals, phylogenetic reconstruction should be performed separately on each signal. (Emphasis added in all quotes.)Will this workaround cure all problems, though? Only for small data sets – maybe. The more data, the more impossible the task becomes:For small trees one can hope to overcome the slow convergence by using multiple starting states. However, mixtures coming from large trees may contain multiple species subsets where one tree has T1 as an induced subtree and the other has T2. If there are k such subsets, then about 15k random starting points will be needed. Thus if there are 10 disagreement subsets, then 1510 random starting points will be needed in order to sample from the posterior distribution.That’s over 576 billion. Most tree-building programs try to take shortcuts around the computational hurdles, but these mathematicians are not sure that the heuristic algorithms used are successful in avoiding assumptions that could bias the results. Their paper has proven one way the results can be misleading. Are there others?In our setting, BMCMC [Bayesian Markov-Chain Monte Carlo] methods fail in a clearly demonstrable manner. We expect that there is a more general class of mixtures where BMCMC methods fail in more subtle ways. These subtle failures may occur for many real-world examples where the Markov chains quickly converge to some distribution other than the desired posterior distribution. Users of BMCMC methods should ideally avoid mixture distributions that are known to produce degenerate behavior in various phylogenetic settings. A good practice is to decompose the data into nonconflicting signals and perform phylogenetic reconstruction separately on each signal. Our work highlights important unresolved questions: how to verify homogeneity of genomic data and what phylogenetic methods can efficiently deal with mixtures.Thus, they leave some potential gaping loopholes unexplored.1Mossel and Vigoda, “Phylogenetic MCMC Algorithms Are Misleading on Mixtures of Trees,” Science, Vol 309, Issue 5744, 2207-2209, 30 September 2005, [DOI: 10.1126/science.1115493].What this seems to say is that the method might work on closely-related organisms, like species of snails, but the more you mix different types of organisms into a tree of common ancestry, the more the results of these popular methods will give misleading results. Even with the closely-related trees, though, how can one be sure that the answers might “fail in more subtle ways”? And how do we know that once the smaller trees are assembled, the algorithms won’t mislead horrendously in the final mix? Most creationists would probably not have qualms about trees of closely-related “kinds” of animals, like cats for one, or dogs for another. It is the Darwinian assumption that everything is phylogenetically related – cats, pine trees, bacteria, sharks, petunias, turtles, mushrooms, senators – that causes the controversies. Evolutionists often showcase the printouts from these programs in their scientific papers to lend an air of computational legitimacy to their theories (see the fallacy of statistics). Well, we warned you that evolutionists are bad at math (08/19/2005, 07/25/2002). The only illustration in Darwin’s Origin of Species was a phylogenetic tree. Since then, tree-building has become a favorite pastime around the Darwin Temple gamerooms (10/22/2001, 06/13/2003). Impressive as the charts look to the uninformed, they hawk symbolism over substance. This fits Hawkins Theory of Scientific Progress (right sidebar). After reading this article, and the links to previous ones, how do you feel about that NSF Tree of Life project costing $12 million in tax dollars? (10/30/2002). If you want a better Tree of Life, try God’s (search) – it’s free, it’s honest, and you don’t have to play Monte Carlo to find it.(Visited 12 times, 1 visits today)FacebookTwitterPinterestSave分享0
Related Posts Follow the Puck Tags:#BYOD#cloud#cloud services#DaaS#Device Security#IoT Robin Hau is the founder and CEO of SimplyClouds, a provider of powerful, affordable cloud services that utilizes a self-service marketplace. Hau also serves as CEO of SimplyClouds’ parent company, USWired. The modern workplace is increasingly characterized by remote and contingent workers, BYOD policies, and the need for 24/7 access to data. My position as the CEO of USWired has given me a firsthand look at both the positive impact the cloud can have on businesses and the barriers to its adoption. We’ve seen a growing demand for cloud-hosted desktop as a service, but many people don’t know what factors to consider when adopting DaaS.Under the Hood of a Hosted DesktopDaaS allows users to access critical applications and files at any time — no matter where in the world they are — from any smart device, regardless of its operating system.In other words, cloud-hosted desktops mean enhanced workflow across devices.You can start a working session on your Windows laptop, and if it runs out of battery life, you can pick up right where you left off on your iPad. Ultimately, this increased accessibility translates to increased productivity.Housing data and files remotely also provide additional security. DaaS solutions typically come with enterprise-grade firewalls, intrusion detection, and malware protection, and they secure your data through encryption, regular backups, and multifactor authentication. These security features mean that it’s harder for attackers to breach your network, and the fact that your business data is stored remotely makes a complete recovery from an on-premise disaster far more likely.In short, DaaS makes your business more resilient.There are also benefits from a financial standpoint. Because the cost of hosting your desktop in the cloud is dependent on your needs, you only pay for what you use. It enables you to avoid the expenses that come with upgrading hardware or installing new platforms, as the only requirement for accessing a hosted desktop is a connected device.Finding the Best Cloud Provider for Your NeedsNot all virtual desktop providers are created equal, and choosing one that fails to deliver what you’re looking for can be a significant drain on resources.One of the common mistakes business leaders make: choosing the wrong provider, so start your process by doing plenty of research.Jot down the names of providers that are well-reviewed or mentioned in publications. Ask for recommendations from your professional network. Once you have a list, visit the providers’ websites to see whether they offer the services that you need and the prices that fit your budget.After you’ve narrowed your list to three or four options, call them to discuss your hosted desktop needs. Ask for references, and make sure they are authorized by the respective vendors (Microsoft, Citrix, etc.). Vet providers by asking the following questions:Is uptime guaranteed? DaaS providers should be able to offer close to a 100% uptime, or system reliability. Good providers will guarantee near-perfect reliability. Inquire about support resources available for when issues do inevitably arise. Most providers should offer extended support hours and services.Will my privacy be protected? DaaS providers typically have access to data that belongs to all clients. Ask for details about how a provider ensures confidentiality. Ask about technical security features, and make sure that your provider is located in a geographically secure area — damage to its facilities could affect your business.Can the provider comply with industry regulations? If you work in a highly regulated industry such as finance or healthcare, for instance, you’ll face unique legal requirements. Make sure a provider has experience working in your environment.What is the lag time? Data stored in the cloud has to travel between servers and devices so that users could experience lag time during particular transactions. Specific high-performance, graphics-intensive applications, such as computer-aided design and drafting, may need a dedicated graphics processing unit as part of their hosted desktop configuration to achieve an acceptable level of performance. Depending on the underlying technology a vendor uses for the hosted desktop and your Internet connection, lag time may or may not be an issue. Citrix’s Virtual Desktop (formerly called XenDesktop) claims near-native performance, for example. Regardless, you should discuss your specific performance requirements with any potential provider.Implementing Hosted Desktops With Minimum DisruptionWhen you’ve secured a partnership with a provider you trust, work with those experts to create a nimble, specialized DaaS platform that meets your company’s needs.Your company’s DaaS platform will not look like any other company’s platform, and that’s a good thing. Walk through the following steps with your selected provider to determine the best program for your needs:1. Decide how much control you’ll allow users.A hosted desktop can either be shared among all users or dedicated to each user. Work with your cloud provider to determine which approach makes the most sense for your company’s workflow and regulations.Shared desktops allow higher-ups greater control over what users can do. When users log in, they can customize their desktop and have private folders to store documents. However, they can’t install applications themselves. A shared hosted desktop is ideal for businesses that need to limit application or data use.Dedicated desktops provide maximum flexibility for users but limited control for the business owner. In addition to customizing desktops, users can install any application. A dedicated, hosted desktop is ideal for businesses that want maximum flexibility for their users.2. Decide which applications and data should remain on-premise.Even with DaaS, many businesses choose to maintain some applications or data storage in-house. This is an important discussion to have with your provider. For example, would it make more sense for your company to run the email system through the cloud but payroll through on-premise servers? Does your industry have regulations about keeping sensitive data on-site? Be sure also to consider the requirements of vendors whose applications you are considering moving to the cloud.If you have decided to have applications running on-premise as well as in the cloud, you need a hosted desktop capable of running a hybrid cloud. The provider typically will set up a virtual private network, or VPN, to your on-premise network so that your hosted desktop can access your on-premise applications as if you were using a locally networked office desktop.3. Obtain a second internet line.The cloud provides security in case of a disaster or other interruptions that would otherwise bring operations to a halt. However, access is key. Invest in a second internet line to protect your data, applications, and transactions in case the primary line goes down. You should not use the same internet provider for your second line as for your primary line, in case one has a blackout. Ask your cloud provider for a recommendation.4. Account for the transition.It shouldn’t take long for a provider to configure your virtual desktop. Depending on the DaaS provider, it can take anywhere from 30 minutes to 24 hours to provision a hosted desktop. The reason for this wide range is that some DaaS providers completely automate the provisioning (requiring no human intervention); others have to manually provision the desktop (which requires a human being to receive the work order and then schedule an engineer to configure and spin up the desktop).What will take the longest is employees becoming comfortable with the new system, so you’ll likely need to provide training and encourage plenty of patience. Ask your provider for training, resources, and support.A virtual desktop can be a game-changer for your business, but choosing the wrong provider can turn DaaS into an obstacle rather than a solution. Find a provider who is willing to spend time learning about your objectives and your unique needs and who understands your industry. The best providers will give you useful input and recommendations that steer you toward the right solution. AI: How it’s Impacting Surveillance Data Storage How Data Analytics Can Save Lives Why IoT Apps are Eating Device Interfaces Robin HauCEO of SimplyClouds
Add flares to your video shots using this simple in-camera DIY solution.There’s a ton of ways to add flares to your videos in post, but there’s no substitute for achieving this organic effect in-camera. We’re digging this DIY technique by recent creativeLIVE presenter Lindsay Adler.In the short video below, Lindsay demonstrates how she created a custom flare filter using a cheap crystal (bought online) and a simple lens filter (a low cost UV filter does the trick). By gluing the crystal to directly to the filter, you can create unique refracted light effects that give the video image a dream-like quality. This DIY solution, is super cheap and easy to create.This isn’t a technique that you’ll use on a ton of shots – but given the right subject matter (fashion or weddings, for example) it’s one that can be really impactful.Check out the quick tutorial and example shots below – a snippet from Lindsay’s full creativeLIVE workshop “Keep it Simple: Video for Photographers“.Thanks to DIYPhotography.net for tipping us off to this video.
Bhubaneswar, Feb 14 (PTI) Mahanadi Coalfields (MCL) has extended a helping hand towards 61 under-privileged farmers in Odishas Sambalpur, raising the total number of peasants sponsored by it to 378 in the district, to enable them water their crop timely and reap a good harvest.MCL, a leading coal mining CPSU and a subsidiary of Coal India Ltd, has sponsored 61 more below poverty line (BPL) SC and ST farmers of Bamra, Jamankira and Kuchinda blocks of Sambalpur to avail Deep Borewell Secha Karyakrama Scheme of Odisha government and have own bore-well in their fields.With these 61 beneficiaries, total number of under-privileged farmers sponsored by MCL to avail government scheme has gone up to 378 in Sambalpur district, a company statement said today.The State government has a scheme under which an SC/ST BPL farmer can have their own deep borewell on making subsidised payment of Rs 9,000. However, many farmers in the district could not avail this scheme due to their low income.The district administration took an initiative to identify such under-privileged farmers and requested MCL to sponsor them for the Deep Borewell Secha Karyakrama Scheme so that they can also prosper and contribute towards economic growth, it said.State governments executing agency, Odisha Lift Irrigation Corporation (OLIC), has a plan to provide deep borewells to these beneficiaries by April this year.”Being a farmer means shaking hand with Mother Nature every day and contributing towards strengthening these hands is always an honour,” said MCLs Director (Personnel) L N Mishra, who heads the empowered CSR Committee of the company.advertisementFarmers are the mainstay of nations economy and supporting agrarian segment of the society is one such area MCL is keen to work for, he said, asserting that positive change at the grass root level can ensure development.Besides ensuring uninterrupted supply of coal to the power plants, MCL has been contributing through its popular CSR activities towards infrastructure and socio-economic development of under-privileged segments of the society, particularly in peripheral areas under its command.A Rs 25 crore State-of-the-art Sports Stadium in Sambalpur, Rs 8.62 crore Burla water scheme, Rs 5 crore rope-way connecting Gandhi Minar at Hirakud, hostels to VSSUT and Sambalpur University to help students of far-flung areas get higher education, first electric crematorium of western Odisha at Sambalpur, setting-up a medical college at a cost of Rs 492 crore and Rs 30 crore cardiac hospital in Jharsuguda and running two nursing schools are among the long list of companys CSR activities. PTI SKN CR MKJ
WASHINGTON, D.C.- Jamaicans and friends of Jamaica in Atlanta, Georgia, will mark the country’s 51st Year of Independence with two major activities between August 4 and 10.The programme of activities, which are being planned by the Atlanta Jamaican Association (AJA), commences with a Thanksgiving Service at the Hillside Presbyterian Church in Decatur at 5:00 p.m. on Sunday, August 4. The service will feature music, songs and poetry, which capture Jamaica’s rich cultural heritage.The sermon will be delivered by Professor of Theology at Emory University, The Rev. Dr. Noel Erskine, while the Rev. Dr. Barry Davis, will bring a special musical tribute.The celebration comes to close on Saturday, August 10 with the Annual Independence Ball and Scholarship Awards at the Marriott Atlanta Airport Gateway.This spectacular black tie event, which is the premier annual Caribbean event in Atlanta, attracts patrons from Georgia and surrounding states.A special feature of this year’s event will be the honouring of the Hon. Vin Martin, former Jamaican Honorary Consul in Atlanta, who retired from that position at the end of June this year after serving for 16 years. Among those who will be paying tribute to Mr. Martin are US Congressman, Hank Johnson; President of the Atlanta Jamaican Association (AJA), Errol Ritchie; Dr. Noel Erskine and Dr. David Panton.Two education scholarships will be awarded, one from the AJA and the other from the Tropical Sports Club, to two students of Jamaican parentage. The AJA Community Service Award will be presented to Ms Jacqueline Hawthorne-Robinson of Golden Krust Bakery.According to Mr. Ritchie, the annual events commemorating the anniversary of Jamaica’s independence are very important to Jamaicans in Atlanta.“They serve to bring us together in a cultural bond that oftentimes overpowers the individualistic urges that seem to restrict our coming together as a people. These events bring back memories of our time in Jamaica and force us to reflect on our achievements as a nation and as individuals. They also serve to remind us of our rich culture and generate the festive mood that we have all come to associate with our independence celebrations,” he said. Thanksgiving Service at the Hillside Presbyterian Church in Decatur at 5:00 p.m. on Sunday, August 4 Story Highlights Annual Independence Ball and Scholarship Awards at the Marriott Atlanta Airport Gateway on August 10 The programme of activities are being planned by the Atlanta Jamaican Association (AJA)