Not me, myself, but our lab has a 1000 kN tensile testing machine. That is the metric equivalent of the 220 kip tensile testing machine shown in this Slow Mo Guys video of a tensile test on a roughly 600 MPa rebar. What did I learn from their video? First, what we do is cool, and second, there is a unit out there called kip, and it’s not for measuring hotel capacity.
This is not a question most people ask of themselves, and those that should don’t think to ask it. It’s left to us parents to wonder: How many Crest commercial brushloads can my kid eat before I should worry about the fluoride? Here’s a calculation to help answer that.
The safety data I’m using is from the 2013 article by the European Food Safety Authority EFSA, Scientific Opinion on Dietary Reference Values for fluoride. They state that regardless of age and condition, the adequate intake is 0.05mg per day per kg of body weight. For a 20-kg person (44 lbs), that works out to 1mg per day.
How much toothpaste to get to 1 mg? It depends on the toothpaste. Most toothpastes have an indication of fluoride ion content. We have a children’s toothpaste (Elmex) which states 500ppm fluoride ion, and a regular toothpaste (Crest) that indicates 0,15%. Our fluoridated table salt contains 0,025% fluoride. This works out to 2g of toothpaste for Elmex, 0,7g for Crest, and 4g of table salt.
That’s all very well, but few people visualize grams well. For the salt, an online converter tells me we’re looking at 0,7tsp. My not terribly precise kitchen scale indicated that for the Crest toothpaste, it corresponds roughly to one TV commercial brushload; for Elmex, to three such brushloads.
And then there’s tea… which weighs in at anywhere between 1.5mg/liter to 4mg/liter, perhaps even more, depending also on whether your water is fluoridated. AcneEinstein has a more detailed treatment of the tea question, which also links to WHO guidelines that seem to only partially square up with the EFSA guidelines.
The upshot: monitor and train your kids, but don’t freak out if they eat a little toothpaste. And don’t raise them exclusively on iced tea…
LinkedIn led me to an interesting article on teamwork and how to assemble a great team. It’s long (compared to the average internet attention span), but worth reading in full – if you have the time.
For those who don’t, here’s the summary: Personality tests are not enough, nay, they are even misleading, because humans are rarely consistent enough in their actions across time and different social settings for the tests to have any useful predictive power. A pretty good predictor on how well a team will work is what the author calls Factor C, which is in turn made up of three measures of the individual members. Those are fairly simple: People who can read non-verbal communication (body language, eyes, etc.) well strengthen a team, as do women. People who dominate the conversation drag down team performance.
Remember, them be stats. I’m sure you can find counter-examples of great male team-players or women who make teamwork trying. I can without hardly thinking. And the author cautions that the gender advantage may simply be another way of pointing out that on average, women are better at reading non-verbal communication. He also points out that this Factor C matters most in face-to-face interaction, and far less in remote collaboration on projects that can be divided into chunks of independent work.
So it’s all more complicated, as you might have expected, but one thing seems certain: Myers-Briggs stinks.
Hello again, world.
Usually, WordPress updates work without a hitch. This time, however, the update somehow thought it had to install a new blog, create new blog database tables within my blog database, and show a lousy “Hello World” post instead of the videos I had just painstakingly uploaded. And within two minutes I was getting roughly an e-mail a minute notifying me of my Chinese spammer friends.
Fixing it wasn’t that obvious, so I’m taking notes here as a reminder for future muck-ups. First, I exported my database before updating – a good idea for my peace of mind, but, if I’m not mistaken, not necessary for saving/restoring my blog. (20/20 Hindsight Tip™: empty spam before exporting, that’ll save a lot of MB.) I had to do three things to restore my database to visibility:
- In wp-config.php, change the value for $table_prefix from “wp_” to “myprefix_”. (Insert real prefix for “myprefix”.)
- In wp-config.php, change the character set to latin1.
- In the newly restored admin panel, change the permalink settings first to default and save the change, then change back to my custom permalink structure (I was smart enough to copy-paste the custom bit beforehand).
Finally, I also deleted the new tables that the new installation had created, which took care of the spam comments in a hurry. And WordPress had to update my database when logging in after step 2, which made my heart skip a beat, but that worked fine.
I do wonder if the update hiccup came from being logged in to the admin panel and the hosting service at the same time, but that seems strange. It’s the only distinction to previous updates, however, that comes to mind.
Josh Kaufman is a guy who’s held a TED talk. With the proliferation of TED talks, that doesn’t seem to set him apart much, but this does: he’s a guy whose TED talk I’ve watched.
TED talks take around 20 minutes, and you’re welcome to watch the talk in its entirety, but for my own benefit I’ve jotted down his four steps for learning a new skill here.
- Deconstruct the skill: break it down into pieces and practice the most important ones.
- Learn enough theory to self-correct, and then start practicing as soon as possible.
- Remove barriers to practicing (distractions, “activation energy,” etc.).
- Practice for at least 20 hours total: this commitment helps overcome frustration.
Adam Leipzig is another guy who’s held a TED talk that I’ve watched. His is half the length of Josh Kaufman’s, which gives him a leg up. His contention is that the happiest people focus outward, on serving others, and he suggests thinking about the following set of questions:
- Who are you?
- What do you do? Put differently: what is the one thing you feel supremely qualified to teach people?
- Whom do you do it for?
- What do those people want and need, and how do they change as a result of what you do? (This question forces me to be outward-facing in my reflection.)
Once you’ve gone through these questions and answered them to your satisfaction, Leipzig suggests changing your answer to the ubiquitous question “What do you do?” from a description of your job to a description of how others change as a result of your work. So, for instance, replace “I head the metallography lab in a steel mill” with “I make sure our customers have reliable data for their safety-relevant car parts” or something along that line. It’s still not perfect: the “change” component is still missing, so I’ve still got some work to do…
Over on sursumcorda’s blog, there’s a post about noticing the numbers we read. I’ve recently noticed wrong numbers in two otherwise excellent books – errors that I think are frequent enough that mentioning them here won’t hurt.
The first instance comes in “Switch,” the Heath brothers’ fascinating examination of what helps and what hinders change both in personal and organizational practice. In their tenth chapter, “Rally the Herd,” they discuss how apt reporting of peer behavior can be used to spread proper behavior. They tell the story of a review time turnaround at a peer-reviewed journal called MSOM:
When Gerard Cachon took over MSOM, most peer reviews were taking from seven to eight months… …Cachon announced that MSOM would review papers within sixty-five days – that was 72 percent faster than its previous average!
Now, the 72 percent don’t appear out of nowhere: 65 days are roughly 28 percent of seven to eight months, so it’s correct (albeit oddly accurate) to say Cachon wanted to reduce the average review period by 72%. However, “faster” implies speed, not duration: and then the Heath brothers understate their case. The original review cycle ran at a speed of about 1.6 reviews per year; Cachon wanted to raise the speed to 5.6 reviews per year. The difference – 4.0 reviews per year – is a whopping 250%!
The second instance comes in “Built to Last,” the business book by Jim Collins and Jerry I. Porras which investigates what attributes determine the long-term fate of a company. In their eighth chapter, “Home-Grown Management,” they write:
Of 113 chief executives for which we have data in the visionary companies, only 3.5 percent came directly from outside the company, versus 22.1 percent of 140 CEOs at the comparison companies. In other words, the visionary companies were six times more likely to promote insiders to chief executive than the comparison companies [emphasis theirs].
While it is true that 22.1 is roughly six times 3.5, that factor represents the relative likelihood of hiring an outsider, not of promoting an insider. For insider promoting, the factor is far less majestic: 96.5 percent is only 1.2 times more than 77.9 percent, making the visionary companies only a good fifth more visionary than their peers…
If you’re unhappy with how your cookies turned out, don’t know which ingredient or which process variable caused the trouble, and don’t have the time, ingredients, or test eaters to vary each variable individually: statistics to the rescue! Done right, design of experiment allows an appreciable reduction in trials without losing the information on which variables have a significant effect on the process. Doing it with a cookie recipe provides an accessible illustration of how it’s done. In this case, the trial runs were reduced by at least a third, depending on how an individual variation experiment might be set up.
I just came across a video of sepak takraw and am impressed by the skillful footwork of these athletes. Have a look: it’s like hackey sack volleyball.
We still don’t have a good system set up. I’m uploading them with the youtube uploader, managing about a dozen overnight in full resolution, so at least in terms of video quality there’s something gained for our loyal readers, even if promptness has taken a brutal hit.
Grouped (roughly) by theme:
Joseph: Picking up and counting, Singing in Japanese, Singing Bappe’s ditty, Reading in German (again), Reading Händel, Picking up with letters, Pi, Counting in French, You Can Count on Monsters (again) (again), Art Inspired by Monsters, Singing by the Drain, Up to 11, 12 and beyond, Ten out of Bed, City Blocks, Green Eggs and Ham (cont’d), A Message from Mommy, Counting in French, Grandma’s Squares Book.
Vivienne: What does the dog say?, Flash cards, Exercising with Mommy, Bend it like Beckham, Too Cute to Perform (again), Brushing Teeth, Jump, Harvest, Chase the Camera, Bunnies, Balcony Chalk, Math Time, Counting in French, Playing together with the Hammer Toy (again), Dancing.
Other family: Four on a couch.
Other: Paradigm Change
And I’m not surprised at what he can do. Small, wiry, always in motion – at a later stage I remember him running at a wall to do a backflip, but clearly he didn’t stop at that.
Sensitive ears may want to turn off the sound.