Cochrane review finds that there is little evidence that water fluoridation has any dental benefits, although it does not dispute that fluoride in toothpaste reduces tooth decay:
Studies that attest to the effectiveness of fluoridation were generally done before the widespread usage of fluoride-containing dental products like rinses and toothpastes in the 1970s and later, according to the recent Cochrane study. So while it may have once made sense to add fluoride to water, it no longer appears to be necessary or useful, Thiessen says.
It has also become clear in the last 15 years that fluoride primarily acts topically, according to the CDC. It reacts with the surface of the tooth enamel, making it more resistant to acids excreted by bacteria. Thus, there’s no good reason to swallow fluoride and subject every tissue of your body to it, Thiessen says.
Another 2009 review by the Cochrane group clearly shows that fluoride toothpaste prevents cavities.
Earth rise, as seen by a Japanese lunar orbiter
A dermatome is an area of skin that is mainly supplied by a single spinal nerve. There are 8 cervical nerves (C1 being an exception with no dermatome), 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. Each of these nerves relays sensation (including pain) from a particular region of skin to the brain…
Along the thorax and abdomen the dermatomes are like a stack of discs forming a human, each supplied by a different spinal nerve. Along the arms and the legs, the pattern is different: the dermatomes run longitudinally along the limbs. Although the general pattern is similar in all people, the precise areas of innervation are as unique to an individual as fingerprints.
Probably important for disagnosing nerve damage. (h/t Quinn van Handel.)
- “Dutch universities start their Elsevier boycott plan“.
Newish ideas for macroeconomics: Trills.
The governments of the world should issue shares in their GDPs, securities that pay to investors as dividends a specified fraction of GDP, in perpetuity (or until the government buys them back on the open market). Governments need to end their historic reliance on debt financing: governments issuing shares in GDP is analogous to corporations issuing equity. My Canadian colleague Mark Kamstra and I propose issuing trillionth shares in GDP, and so to call these “Trills.” Last year, a U.S. Trill would have paid $15.09 in dividends, a Canadian Trill C$1.72. The dividends will change every year as GDP is announced, and predicting these changes will certainly interest investors, just as in the stock market. Governments can auction off Trills when current government debt comes due and needs to be refinanced, as part of a debt reduction program.
Substituting Trills for conventional debt helps deleverage the government, something whose importance has become very clear with the debt crisis in Europe. The payments required of the government by the Trills is connected to the country’s ability to pay, measured by their GDP.
See also the NYTimes article. (H/t Rob Wiblin and Alex Flint.)
You might think this gives a government bad incentives to misstate their GDP, but this actually seems like they have much less room to maneuver here than they do when they can de-value the currency they pay their debts in by printing money. (Another way to think about this is that it extends, to countries like Greece in monetary unions, the natural debt flexibility available to countries that control their own currency.)
Going further, you might want something that isn’t linear in GDP since the country’s ability to pay probably won’t be either. For instance, consider a financial instrument that pays zero if the GDP is below some fixed amount (or some schedule) but rises supralinearly if the country is successful.
- GiveWell covers geomagnetic storms as a global catastrophic risk. Relatedly, Stuart Russell lectures from Cambridge on the long-term future of artificial intelligence.
Anarcho-capitalism; not as crazy as it sounds?
…statelessness did not lead to chaos. Rather, Somalia continued to resemble other African societies on most measures.
- Scientific American article on the interaction between gut flora and the immune system.
- Here is some good recent discussion of Lyft vs. Uber. I still don’t understand why many people assume rideshare services have strong network effect. Many drivers drive for both, switching between the two with a touch of their phone. Likewise for riders. (I ride them interchangeably.) Yes, people get into habits and may tend to stick with an incumbent out of habit, but that’s true for just about every product. There’s nothing strongly locked-in or social in them like there is for services like Facebook.
- Tech-related blogs and podcasts suggested by HN readers.
- Jeff Atwood on the rather bleak state of password security.
Oil platforms are awesome, in the traditional sense of inspiring awe.
Here is a documentary on one of them: Perdido.
Bonus: Troll A
- My diffusion SQL paper is now published: PRA 92, 010101(R) (2015) [arXiv:1504.03250]. I expect you will be ordering your dead-tree copy soon.
Peter Singer and critics debate Effective Altruism. Excellent follow up by Chris Blattman and Rob Wiblin. In particular, effective altruism is not synonymous with earn-to-give.
…the proportion of people for whom we think earning to give is the best option has gone down over time….Instead, we think that most people should be doing things like politics, policy, high-value research, for-profit and non-profit entrepreneurship, and direct work for highly socially valuable organizations….Here are the reasons why we think fewer people should earn to give than we did in the past…
Relatedly, Yudkowsky lays out the highly suspicious nature of flow-through-effect arguments.
- Lots of nice plots on overall world economics development. “GDP per square kilometer” is especially novel to me.
- TED talk on the view from driverless cars. Relatedly, here is a wireframe reconstructed video of the Google self-driving car getting rear-ended by a distracted human driver.
- 3D visualization of earth-orbiting satellites. (If you are using Chrome and see only orbits, no dots, then try opening it in Firefox.) Zoom out to see the heavily-dotted circle of geostationary orbit. The GLONASS satellites are also visibly dense along a certain inclined orbit at roughly that distance. (HN Discussion.)
- Incidentally, I thought I must have posted this before but I can’t pull it up: the Deep Space Network status panel.
- Rare system of five stars discovered.
- Sabine on the over-reported death of lone scientific work.
- “Will Our Understanding of Math Deteriorate Over Time?” Yes, and it happens for most disciplines. This could be mitigated by better incentives for organizing and synthesizing the literature, but nobody cares.
- New robotic camera mount lets you film yourself more easily. It tracks a small transmitter you keep with you.
- The best ground-based images of the planets before the first space probes arrived. More here.
- Pentaquarks. LHCb says they finally have been seen definitively. But see Marek Karliner.
- Some details behind New Horizon’s cameras.
New Guardian article on the square kilometer array.
(“SKA antennas at night” by SKA Organisation.)
- Great introductory talk on extrasolar planets by Sara Seager given here at PI. (Search “mp4” on the page source to down the video file directly.) I was blown away that they think they can directly image exoplanets using orbital telescopes and giant “starshades” to occult the host star. Interestingly, the starshades can be usefully deployed independently of the main satellite with only minimal communication between the two. (Here is a video on the Nasa page that was included in Sara’s talk.)
- Computer-assisted correspondence chess games (the highest level of chess play) are converging to 80-90% draws. One proposed solution: give more than half a point to players who stalemate the game with better pieces remaining than their opponent. (H/t Tyler Cowen.)
- February NYTimes op-ed on using prizes to supplement patents for incentivizing antibiotic discoveries.