- The hyoid bone is unique in the human skeleton for being free-floating; it does not share a joint with any other bones, and is only distantly connected to the skull through the Stylohyoid ligament. It is mostly held in place by muscle and cartilage, and helps control the tongue and larynx. Unlike a human’s clavicle, a cat’s clavicle is similarly free-floating, allowing a cat’s shoulders to squeeze through openings as narrow as their skull.
…was the first of a series of missions to Mars that included rovers, and was the first successful lander since the two Vikings landed on the red planet in 1976…In addition to scientific objectives, the Mars Pathfinder mission was also a “proof-of-concept” for various technologies, such as airbag-mediated touchdown and automated obstacle avoidance, both later exploited by the Mars Exploration Rover mission. The Mars Pathfinder was also remarkable for its extremely low cost relative to other robotic space missions to Mars.
Here’s Cindy Healy talking about UNIX administration for Pathfinder.
(H/t Dan Fincke.)
- Good write-up about the boys rescued from the cave in Thailand.
18-year-old Ewin Tang has proved that the Kerenidis and Prakash recommendation algorithm does not provide an example of an exponential speed up in quantum machine learning. Here’s his advisor Scott Aaronson on the implications:
Prior to Ewin’s result, the KP algorithm was arguably the strongest candidate there was for an exponential quantum speedup for a real-world machine learning problem. The new result thus, I think, significantly changes the landscape for quantum machine learning; note that whether KP gives a real exponential speedup was one of the main open problems mentioned in John Preskill’s survey on the applications of near-term quantum computers
More Fuel For The QML Skeptic Game.
Breather switches, also known as expansion joints, allow train tracks to expand and contract from temperature changes without buckling or leaving a gap.
Expansion joint near Hayle railway station, England (Wikipedia)
- IceCube experiment matches first neutrino with an extra-galactic object. (Journal article.) IceCube has a collection volume of a cubic kilometer (to increase by an order of magnitude) and a neutrinio momentum angular resolution of 0.7 degree. It is sensitive enough to see the neutrino shadow (!) cast by the moon. Rediculous
Fermat’s Library Cofounders João Batalha and Luís Batalha on the YCombinator podcast.
- Time lapse of fireworks for July 4 in LA.
The meticulous Alyssa Vance on the aging of Y Combinator:
[Paul] Graham’s writing talks about a pair of nineteen-year-old geeks as the archetypal founders. The first iteration of Y Combinator, the Summer Founders Program, was explicitly set up for undergrads, and was started during the summer so that students wouldn’t have to drop out (http://old.ycombinator.com/sfp.html). Sam Altman, the current president of Y Combinator, was one of these initial summer founders, and was a 20-year-old Stanford undergrad at the time.
However, things appear to have changed quite a bit since then. Y Combinator doesn’t publish exact statistics, but in their Winter 2015 batch, there were zero founders who were 18 or 19, out of around 300 people (https://blog.ycombinator.com/yc-stats-winter-2015/). In an informal survey I did of fifty or so LinkedIn profiles (sadly I didn’t save the data, sorry), no one was younger than 25, which with a median of 29 implies that the distribution is tightly clustered. I’d be very interested to see a full statistical analysis of YC cohorts and how they’ve changed over time, unfortunately re-assembling that data would take a while.
- Some linguistic aspects of how consonants on the end of French words become silent.
How Uranus got it’s tilt (maybe):
Scientists have always wondered how Uranus got tilted so much that it spins on its side, and now research on the planet’s early formation gives us new insight. Four billion years ago, scientists believe a young proto-planet of rock and ice collided with Uranus, causing its extreme tilt. Instead of rotating like a top spinning nearly upright, as Earth does, the planet “rolls” on its side as it circles the sun.
- Paul Christiano on The Elephant in the Brain.
The year 2017 in nuclear power worldwide:
4 reactor startups (12 less than scheduled), 3 shutdowns, 4 construction starts, 2 abandoned constructions, bankruptcy of Westinghouse, bailout and breakup of AREVA, significant financial and economic pressure on nuclear operators. Five new reactors entered long-term outage, and 3 were restarted. Globally, 405 reactors operating (1 less than a year ago), 52 under construction (3 less).
(H/t Hauke Hillebrandt.)
The German Me 163 Komet from 1944 was the only rocket-powered plane ever used in military combat. And here is the XFY-1 Pogo, also rocket-powered and one of the first tail-sitters:
On the genetics of Triticale, a cross between wheat and rye:
Commercially available triticale is almost always a second-generation hybrid, i.e., a cross between two kinds of primary (first-cross) triticales. As a rule, triticale combines the yield potential and grain quality of wheat with the disease and environmental tolerance (including soil conditions) of rye. …When crossing wheat and rye, wheat is used as the female parent and rye as the male parent (pollen donor). The resulting hybrid is sterile and must be treated with colchicine to induce polyploidy and thus the ability to reproduce itself…The triticale hybrids are all amphidiploid, which means the plant is diploid for two genomes derived from different species. In other words, triticale is an allotetraploid. In earlier years, most work was done on octoploid triticale. Different ploidy levels have been created and evaluated over time. The tetraploids showed little promise, but hexaploid triticale was successful enough to find commercial application.
- The X-59 will test a design for lowering the intensity of sonic booms by three orders of magnitude, potentially opening up commercial supersonic travel over land.
- Illuminating discussion of Thomas Piketty’s Capital In The Twenty-First Century by Scott Alexander and commenters: 1, 2, 3.
- Why nobody ever wins the car at the mall.
From Tyler Cowen: A guide to newsletters and podcasts on China. And what Varlam Shalamov learned in the Kolyma gulag. And an interview with Vitalik Buterin:
- Nick Beckstead (1, 2, 3) and Paul Christiano (1, 2) on whether economic growth and tech progress is net good or bad for x-risk.
Tabarrok reports on Einav et al:
That one-quarter of Medicare spending in the United States occurs in the last year of life is commonly interpreted as waste. But this interpretation presumes knowledge of who will die and when. Here we analyze how spending is distributed by predicted mortality, based on a machine-learning model of annual mortality risk built using Medicare claims. Death is highly unpredictable. Less than 5% of spending is accounted for by individuals with predicted mortality above 50%. The simple fact that we spend more on the sick—both on those who recover and those who die—accounts for 30 to 50% of the concentration of spending on the dead.
- Neutrophils, the most common types of white blood cell, kill bacteria by bleaching them. First, a bacteria is consumed by the neutrophil, enveloped in a section of the neutrophil cell membrane — a phagosome — and released free floating in the interior of the neutrophil cell. Then, small packets containing ADPH oxidase and myeloperoxidase fuse with the phagosome and dump their contents inside, where they generate superoxides that kill the bacteria.
SpaceX has massively upgraded it’s giant sea borne net for catching rocket fairings falling from space. Here are comparisons with the old structure. And here’s an industry ad showing off the ship’s lateral thrusters (pre-net), and here is the drone footage of the new net configuration:
How childhood vaccines are scheduled:
Babies survive initially on their mother’s natural antibodies (shared through the placenta and then through breastmilk) until the baby itself has developed an immune system capable of protecting itself. The thymus in particular is an organ that needs to develop for a while before it can handle any vaccines. Otherwise, without a functional immune system, the vaccine can just make the baby sick and won’t result in the development of any immunity.
It then comes down to A) whether the vaccine is attenuated, dead, or a toxin vaccine, which each require the developing body to be a certain age/immune strength to be effective. B) The age of administration of the vaccine is also relevant to the diseases the baby will encounter at that age. Many are given at 6, 12, 18 months etc because babies are very prone to whooping cough, measels, pertussis, polio, with lethal outcomes. On the other hand, the gardasil vaccine isn’t really necessary until the child is much older (I think the current age is 12, may soon be 10), because it is unlikely that a 12mo baby will encounter a sexually transmitted virus.
The vaccine scheduled has been refined to make sure the greatest amount of immunity can be achieved at the earliest time possible.
PBS video on the mechanics of the mosquito probocis.
(H/t Darren McKee.)
For most mammals, the sex of the embryo is determined by whether the sperm has an X or Y chromosome, and this mass difference allows semen to sorted by sex with surprising accuracy. The future possibility of picking the gender of children has been much discussed, but sex-selection in dairy calves is already deployed:
…sexed semen has an approximate conception rate of 90% of the conventional semen rate. Sexed semen is also roughly 90% accurate for the gender selected…
For dairy farmers, the major economic advantage to sorted semen is the heifer replacement aspect. Holstein heifer calves currently bring about $200 more than bull calves. The difference is about $700 in the Jersey breed. With this value difference, the additional revenue generated from a higher percentage of heifer calves offsets the higher cost of sexed semen compared to conventional semen, making it a profitable breeding alternative.
According to Hippen, sexed semen allows for more females, of course, but it also allows for the dairy to select from a larger group of females to keep when selecting replacements.
“If the dairy genomic tests all their females, they can also increase the genetic value of their herd sooner,” Hippen says. “There is also some research that shows higher milk production for the dam when she delivers two females in a row. This also means calving ease — specifically less stress on the animal delivering females as well.”
- Ben Garfinkel on the continuum between literary metaphors and motte-and-baileys. (H/t Rob Wiblin and Stefan Schubert.)
Liquid breathing started as idea to enable underwater diving at extreme depths, and was popularized in the James Cameron movie The Abyss. Here, Thomas Shaffer describes how the idea for liquid breathing was applied to preterm infants:
According to the Wikipedia article, though, this technique has not yet been shown to have superior outcomes:
Clinical trials with premature infants, children and adults were conducted. Since the safety of the procedure and the effectiveness were apparent from an early stage, the US Food and Drug Administration (FDA) gave the product “fast track” status…due to its life-saving potential. Clinical trials showed that using perflubron with ordinary ventilators improved outcomes as much as using high frequency oscillating ventilation (HFOV). But because perflubron was not better than HFOV, the FDA did not approve perflubron, and Alliance is no longer pursuing the partial liquid ventilation application. Whether perflubron would improve outcomes when used with HFOV or has fewer long-term consequences than HFOV remains an open question.
Alas, recent contact w/ & gossip on crypto world suggests lots of tool/platform building, but too little effort to gain ordinary customers. I now tentatively guess 80% chance of collapse w/in 7 yrs to <20% of current activity level, a collapse that lasts >15years.
- “Ask HN: What are the things that you have automated in your personal life?”
Introduction to the Aerospike rocket-engine nozzle:
It is notable that empirical properties of the Earth and of conventional fuels means that single-stage to orbit is just out of reach with conventional technology, such that merely dynamically re-shaping the engine’s thrust with an aerospike would in-principle allow the avoidance of stages.
A recent XKCD on the presidential line of succession points us to this excellent summary of the Continuity of Government Commission organized by the American Enterprise Institute and the Brookings Institution.
PROBLEM: The current constitutional and legal provisions fail to take into account the possibility of a catastrophic attack on Washington, D.C. Since all individuals included in the Presidential line of succession are based in our nation’s capital, a catastrophic attack on the city could potentially kill or incapacitate many if not all of these individuals and cause significant confusion about who can assume the powers of the presidency. With the inclusion of members of Congress and acting cabinet secretaries in the line of succession, all of whom must resign from their current positions before assuming the presidency and can then be “bumped” from the presidency by an individual ranking higher in the line of succession, it is possible to have no one remaining in the line of succession. Current procedures leave our nation especially vulnerable at presidential inaugurations and State of the Union Addresses.
Temple Grandin: “I see kids today; they’re playing with legos. That’s great. But then the kids never graduate to tools. He’s still building legos at age 10.”
Methods for clearing orbital debris are currently being tested:
Rather than engaging in active debris removal (ADR) of real space debris, the RemoveDEBRIS mission plan is to test the efficacy of several ADR technologies on mock targets in low Earth orbit. In order to complete its planned experiments the platform is equipped with a net, a harpoon, a laser ranging instrument, a dragsail, and two CubeSats (miniature research satellites). The experiments are as follows:
- Net experiment – One of the CubeSats, called DebrisSat 1, will deploy a balloon meant to simulate a piece of space debris. From a short distance away, the RemoveDEBRIS satellite will attempt to capture the debris in a net and then manoeuvre this package to fall into Earth’s atmosphere and burn up.
- Vision-based navigation – The other CubeSat, called DebrisSat 2, will be released and the RemoveDEBRIS satellite will undergo a series of manoeuvres in order to obtain data and images using both lidar and optical cameras.
- Harpoon and deployable target – A harpoon connected by a tether will be fired at a plate attached to an arm extending from the RemoveDEBRIS platform itself.
- Dragsail – After the conclusion of the other experiments the satellite will deploy a large sail, which will act in a similar fashion to an air brake. The dragsail will bring RemoveDEBRIS from the relatively low orbital altitude of the space station into the planet’s atmosphere to safely disintegrate.
Weird stationary bubbles that form in the fish tank experiment on the International Space Station.
On the frequency and impact of mutations introduced in each generation:
De novo mutations have been shown to be a major cause of severe early-onset genetic disorders such as intellectual disability, autism spectrum disorder, and other developmental diseases. In fact, the occurrence of novel mutations in each generation explains why these reproductively lethal disorders continue to occur in our population.Recent studies have also shown that de novo mutations are predominantly of paternal origin and that their number increases with advanced paternal age….
A typical human genome varies at 4.1 to 5.0 million positions compared with the human reference genome . The vast majority of genetic variation observed in a typical human genome is common and shared by more than 0.5% of the population as a result of having been recombined, selected, and passed on for many generations. By contrast, a typical human genome contains 40,000 to 200,000 rare variants that are observed in less than 0.5% of the population…
Genome-wide NGS studies place the germline de novo mutation rate for SNVs in humans at 1.0 to 1.8 × 10–8 per nucleotide per generation, with substantial variation among families. This number translates into 44 to 82 de novo single-nucleotide mutations in the genome of the average individual, with one to two affecting the coding sequence.
The analogy between overfitting and code rot:
I recently came across this artice:
Although it describes the issue pertaining to statistics + machine learning, this is also exactly what end ups up happening with a large codebase without clear requirements or test cases, and people just making incremental, piecemeal changes over time. You end up with an application that has been trained (overfitted) with historical data and usecases, but breaks easily for slightly new variations that are different from anything that has ever been handled by the system before in some trivial way that better designed, cleaner, more abstract system would be able to deal with.
Solving Rubik’s three cubes while juggling them:
(H/t Dominic Roser.)
Microchimerism in cattle:
A freemartin…is an infertile female mammal with masculinized behavior and non-functioning ovaries. Genetically the animal is chimeric: Karyotyping of a sample of cells shows XX/XY chromosomes. The animal originates as a female (XX), but acquires the male (XY) component in utero by exchange of some cellular material from a male twin, via vascular connections between placentas… Freemartinism is the normal outcome of mixed-sex twins in all cattle species that have been studied, and it also occurs occasionally in other mammals including sheep, goats and pigs.
In most cattle twins, the blood vessels in the chorions become interconnected, creating a shared circulation for both twins. If both fetuses are the same sex this is of no significance, but if they are different, male hormones pass from the male twin to the female twin. The male hormones (testosterone and anti-Müllerian hormone) then masculinize the female twin, and the result is a freemartin. The degree of masculinization is greater if the fusion occurs earlier in the pregnancy – in about ten percent of cases no fusion takes place and the female remains fertile.
The male twin is largely unaffected by the fusion, although the size of the testicles may be slightly reduced. Testicle size is associated with fertility, so there may be some reduction in bull fertility.
Aspects of VR:
Foveated rendering is an upcoming graphics rendering technique which uses an eye tracker integrated with a virtual reality headset to reduce the rendering workload by greatly reducing the image quality in the peripheral vision (outside of the zone gazed by the fovea).
- Popehat on the recent legal defeat of the SPLC.
- Life by biomass. (H/t Simon Eckerström Liedholm.)
- Jeff Kaufman argues that the widely quoted claim about the caloric efficiency of meat vs. plant farming — that only ~10% energy survives the conversion from grain to meat — is somewhat exaggerated.
- Speculation in PRL on stable quark matter.
- Find where any address would have been on Pangea. (H/t Scott Alexander.)
- The indigenous people of Norway and Sweden are the Sami. Unlike many indigenous groups around the world who were engulfed by waves of European colonization beginning in the 15th century, the Sami were originally displaced thousands of years earlier by early farmers pushing north into Scandinavia.
- Mysterious alternative space access company SpinLaunch raises $40M.
DARPA’s Ground X-Vehicle Technologies:
- The resolution of the images taken by the first US satellites orbiting the moon were drastically downgraded before public release in order to keep secret the advanced US imaging technology (which was simultaneously deployed on Earth-imaging satellites). The classified full resolution images were used to pick the Apollo landing sites, and have only recently been released. (EDIT: Maybe not.)
LaTeX in commentsInclude [latexpage] to render LaTeX in comments. (More.)
- GitWikXiv follow-up: Distinctions in academic tools (3)
- Beyond papers - GitWikXiv (49)
- GitWikXiv follow-up: An open attribution standard? (1)
- Moyal bracket with manifest (affine) symplectic covariance (2)
- Comments on "Longtermist Institutional Reform" by John & MacAskill (1)
- Tyler John Thanks so much for these excellent questions! Here are my replies, which I've cross-posted to... – Jul 31, 10:00 AM
- Living bibliography for the problem of defining wavefunction branches (12)
- Jess Riedel I'm very familiar with the ideas in Andy's paper and it doesn't conflict with my... – Jul 26, 1:26 PM
- Devin The choice of angle can at least clearly be chosen by a quantum source. I'm... – Jul 26, 12:54 PM
- Jess Riedel > I see that agents develop their own framework and can choose the questions they’ll... – Jul 26, 10:20 AM
- Devin I think I see what you're saying now: that there is one classical framework imposed... – Jul 26, 2:42 AM
- GitWikXiv follow-up: Distinctions in academic tools (3)
foreXiv by C. Jess Riedel is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.