tingilinde

0x5f3759df

The fast inverse square root.  Very useful in computer graphics.  I was unaware of the trick.  You have to love the code sniplet from Quake III. 

A tip of the hat to Greg for pointing it out.

 

 

human error and not biology

The reason for the apparent decline in mortality among the very old.  

a tip of the hat to Greg

if you're into this sort of thing the paper is really interesting

 

Errors as a primary cause of late-life mortality deceleration and plateaus

Saul Justin Newman

Research School of Biology, The Australian National University, Acton, ACT, Australia

Abstract
Several organisms, including humans, display a deceleration in mortality rates at advanced ages. This mortality deceleration is sufficiently rapid to allow late-life mortality to plateau in old age in several species, causing the apparent cessation of biological ageing. Here, it is shown that late-life mortality deceleration (LLMD) and late-life plateaus are caused by com- mon demographic errors. Age estimation and cohort blending errors introduced at rates below 1 in 10,000 are sufficient to cause LLMD and plateaus. In humans, observed error rates of birth and death registration predict the magnitude of LLMD. Correction for these sources of demographic error using a mixed linear model eliminates LLMD and late-life mor- tality plateaus (LLMPs) without recourse to biological or evolutionary models. These results suggest models developed to explain LLMD have been fitted to an error distribution, that ageing does not slow or stop during old age in humans, and that there is a finite limit to human longevity.

Author summary
In diverse species, mortality rates increase with age at a relatively fixed rate within popula- tions. However, recent discoveries have suggested this relationship breaks down in advanced old age, with mortality rate increases slowing and even reaching a plateau. This late-life mortality deceleration has initiated sustained debate on the cause of late-life decel- eration and plateaus. Proposed explanations include evolutionary patterns, the exhaustion of selective pressure, population heterogeneity, and even the cessation of the ageing pro- cess. Here, I demonstrate that apparent late-life mortality decelerations and plateaus can be generated by low-frequency errors. I then reveal how indicators of demographic data quality predict the magnitude of late-life mortality deceleration and the existence of late- life plateaus in human populations. These findings suggest that human late-life mortality plateaus are largely, if not entirely, artefacts of error processes. As a result, late-life mortal- ity plateaus and decelerations may be explained by error patterns in humans and many other species without invoking complex biological, heterogeneity, or evolutionary models. This finding has immediate consequences for demographic modelling, evolutionary biol- ogy, and the projected upper limits of human and nonhuman life.

 

the making of bryne's euclid

This is special - if you have any interest in math just go there.

 

 

a curious map projection

A Euler spiral

 

john urschel goes pro

What happens when a pro football player has a serious interest in something reasonably academic .. like math.  I've had posts on John Urschel before, but here's a good interview.  You might be interested in the linked talk too.

 

 

 

any positive integer can be expressed as the sum of three integer palindromes

So neat

and the paper.

 

EVERY POSITIVE INTEGER IS A SUM OF THREE PALINDROMES

JAVIER CILLERUELO, FLORIAN LUCA, AND LEWIS BAXTER

Abstract. For integer g ≥ 5, we prove that any positive integer can be written as a sum of three palindromes in base g.

 

 

celebrating a nasa computer

Katherine Johnson turned 100 yesterday.

a tip of the hat to Sukie

 

 

breaking spaghetti into two pieces

Hold a spaghetti stand at both ends and break it.  Count the pieces:)  Some new work shows how it can be broken into just to pieces. 

snip

...

If you happen to have a box of spaghetti in your pantry, try this experiment: Pull out a single spaghetti stick and hold it at both ends. Now bend it until it breaks. How many fragments did you make? If the answer is three or more, pull out another stick and try again. Can you break the noodle in two? If not, you’re in very good company.
The spaghetti challenge has flummoxed even the likes of famed physicist Richard Feynman ’39, who once spent a good portion of an evening breaking pasta and looking for a theoretical explanation for why the sticks refused to snap in two.
Feynman’s kitchen experiment remained unresolved until 2005, when physicists from France pieced together a theory to describe the forces at work when spaghetti — and any long, thin rod — is bent. They found that when a stick is bent evenly from both ends, it will break near the center, where it is most curved. This initial break triggers a “snap-back” effect and a bending wave, or vibration, that further fractures the stick. Their theory, which won the 2006 Ig Nobel Prize, seemed to solve Feynman’s puzzle. But a question remained: Could spaghetti ever be coerced to break in two?

...

a tip of the hat to Yuri

 

how humans interpret graphics

Kennedy Elliot at InfoVis

 

a tip of the hat to Lynn

 

feynman's discussion of why planets orbit in elipses

Reconstructed from a lost Freshman physics lecture and presented by 3Blue1Brown

An entertaining method that doesn't require differential equations.  That said it is probably only for those who like math.