Links for September 2014

  • In discussions about the dangers of increasing the prevalence of antibiotic-resistant bacteria by treating farm animals with antibotics, it’s a common (and understandable) misconception that antibiotics serve the same purpose with animals as for people: to prevent disease. In fact, antibiotics serve mainly as a way to increase animal growth. We know that this arises from the effect on bacteria (and not, say, by the effect of the antibiotic molecule on the animal’s cells), but it is not because antibiotics are reducing visible illness among animals:

    Studies conducted in germ free animals have shown that the actions of these AGP [antimicrobial growth promoters] substances are mediated through their antibacterial activity. There are four hypotheses to explain their effect (Butaye et al., 2003). These include: 1) antibiotics decrease the toxins produced by the bacteria; 2) nutrients may be protected against bacterial destruction; 3) increase in the absorption of nutrients due to a thinning of the intestinal wall; and 4) reduction in the incidence of sub clinical infections. However, no study has pinpointed the exact mechanism by which the AGP work in the animal intestine. [More.]

  • You’ve probably noticed that your brain will try to reconcile contradictory visual info. Showing different images to each eye will causes someone to essentially see only one or the other at a time (although it will switch back and forth). Various other optical illusions bring out the brain’s attempts to solve visual puzzles. But did you know the brain jointly reconciles visual info with audio info? Behold, the McGurk effect:

  • The much-hyped nanopore technique for DNA sequencing is starting to mature. Eventually this should dramatically lower the cost and difficulty of DNA sequencing in the field, but the technology is still buggy.

  • There is a new Expert Review from Nature on the genetic underpinning of intelligence, including discussion of “the first new quantitative genetic technique in a century”: Genome-wide Complex Trait Analysis (which is not without its detractors).

  • Although it’s a bit of a game of semantics, astronomers have delineated the supercluster of galaxies that contain the Milky Way, dubbing it “Laniakea”:

    Their definition is based on the idea of an attractor basin:

    The peculiar velocity is the line-of-sight departure from the cosmic expansion and arises from gravitational perturbations; a map of peculiar velocities can be translated into a map of the distribution of matter. Here we report a map of structure made using a catalogue of peculiar velocities. We find locations where peculiar velocity flows diverge, as water does at watershed divides, and we trace the surface of divergent points that surrounds us. Within the volume enclosed by this surface, the motions of galaxies are inward after removal of the mean cosmic expansion and long range flows. We define a supercluster to be the volume within such a surface, and so we are defining the extent of our home supercluster, which we call Laniakea.

    Nature has another popular article. Wikipedia is less effusive.

  • Think you’re being gouged by monopolistic pricing in the Atlantic-Pacific canal market? Fear not. The fat cats in Panama are about to get some competition from the Nicaragua Canal.

  • The consistently excellent magazine Nautilus covers the competition for a billion dollar telescope. Wikipedia has a comparison of telescopes by mirror size (full list here):


    Existing and proposed telescopes by primary mirror size.

  • Overtime-exempt salaried worker are seeing a higher fraction of their pay in the form of bonuses:

    In the US, performance-based bonuses made up 12.7 per cent of payroll in 2014, the highest ratio companies have paid toward annual bonuses in 35 years of record-keeping…

    Insofar as total pay stays fixed, increased bonus pay shifts economic risks from the company to workers. Bonuses allow companies to retain workers in boom times when they are being courted by other companies, while allowing the salaries to fall during contractions. Naively one would think that companies would be better able to shoulder risk, especially in large companies that are exposed to many markets, so they would offer stable salaries as a form of insurance for employees. On the other hand, bonuses are plausibly a way for companies to get around economically inefficient wage stickiness, assuming that stickiness is due to “irrational” psychological effect in employees and assuming bonus-reductions are psychologically less painful than salary cuts. However, neither of these considerations are new, so it’s not clear why this shift is happening now.

  • The Atlantic has a bit on Google’s drone delivery research project.

  • Back in November, two planes carrying sky divers preparing for a joint exercise over Wisconsin collided in midair. One plane immediately broke apart in a fireball, and all sky divers were thrown from or abandoned their planes. The pilot of the severed plane managed to locate his emergency parachute in the falling wreckage, and parachuted to safety. The remaining pilot landed his damaged but operational plane, suffering only a few cuts that were not life-threatening. All sky divers landed without injury.

    Most of the sky divers were wearing GoPro cameras, and the entire event was recorded from several angles. Exclusive rights to this footage were sold to a news station, who significantly cut it down for broadcast. However, most people didn’t realize that the entire video from several points of view was released on YouTube a few weeks later:

    (Be warned that this video is very intense. No one is seriously hurt, but there is dramatic risk to life.)

  • The Wikipedia Summer of Monuments is a campaign to improve coverage of American historic sites on Wikipedia. In particular, you can pull up a list of historic landmarks in your area and see if there are any nearby that haven’t yet been photographed. Then take a picture and upload it to Wikipedia.

  • The also-always-excellent magazine Quanta has an great article on the surprising degree of genetic variation within different cells of a single organism, including humans.

  • “It’s like a stud finder, but for people!”



  • You may remember Yitang Zhang who rose from obscurity to solve one of the great outstanding problems in number theory. Now he has been recognized as a MacArthur fellow. He has an incredibly inspiring academic story of perseverance and passion in the face of adversity:

    After graduation, Zhang had a hard time finding an academic position…He managed to find a position as a lecturer after many years, at the University of New Hampshire, where he was hired by Kenneth Appel back in 1999. Prior to getting back to academia, he worked for several years as an accountant and a delivery worker for a New York City restaurant. He also worked in a motel in Kentucky and in a Subway sandwich shop.

    The UNH department is ranked #108 in math nationwide.

  • I am going to order some Sugru:

    (h/t Diana Fleichman.)

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