Author Archives: ran bi


Stephen Hawking and the ALS disease

Dr Stephen Hawking Physics professor and author at Cambridge University

Less than a week ago, beloved cosmologist and theoretical physicist Stephen Hawking, science’s brightest star, died at the age of 76 in the morning on Mar.14. His brilliance and persistence has inspired people around the world. People who are not specialist in physics may have not heard of his four laws of black hole mechanics or the Hawking radiation, but often have heard of his courageous story and lifelong battle with the amyotrophic lateral sclerosis disease (ALS).

While studying at Oxford, the young Stephen Hawking was diagnosed with ALS – a disease that causes death of neurons and gradually paralyses voluntary muscles – at the age of 21, in 1963. The doctor gave him a life expectancy of less than three years, but Stephen Hawking have defied the odds and coped with the daunting disease for over half a century. He spent 30 years as mathematics professors at the University of Cambridge, published the world-renowned The Universe in a Nutshell and A Briefer History of Time, which introduced cutting edge findings in theoretical physics to millions of readers. While Lou Gehrig and other people that suffer from ALS usually succumb in less than ten years, why has Hawking beat the odds and lived with the formidable disease?

Illustration of a normal nerve structure (left) and an ALS affected nerve cell (right)

Amyotrophic lateral sclerosis is a highly variable disorder and can be classified a few different ways: by where the motor neuron is first affected, and by how fast the disease progresses. Hawking was an outlier, the neurons that control the diaphragm and swallowing muscle are not severely deteriorated, that means breathing muscle functions properly, malnutrition and dehydration which are often found in other cases would not be seen on Hawking.

The disorder progression also tends to be slower in people with onset at less than 40 years old, the reason behind this remains unknown. Hawking’s case is very similar to juvenile amyotrophic lateral sclerosis, which progresses very slowly and have a life expectancy of more than 30 years. And like his mind, Hawking’s illness seems to be singular. Hawking’s longevity is partly due to the excellent care that he received, and more importantly – the biology of his form of the neurodegenerative disease. Stephen Hawking’s case is a unique example of the variability of the disease, he not only gives hope to patient who also suffer from the ALS disease, but also inspires millions for his determination to fight against the odds.

Stephen Hawking’s contribution to physics and cosmology will live in the annals of science forever.

Brainless slime mold grows in pattern like Tokyo’s subway system

Physarum polycephalum, literally the “many-headed slime”

You may have spotted these yellow slime mold in your backyard, they flourish in shady, moist areas, such as decaying leaves. It is a single-celled organism that is not an animal, plant nor fungus. Scientists classify them to the taxonomic group named Protist, which is a group of organisms that are unicellular or unicellular-colonial and form no tissues. Slime mold isn’t capable of forming tissues, let alone organs or body systems. But surprisingly, a group of scientists from Japan found the brainless slime mold, Physarum polycephalum, to be able to remember, decide and solve complex optimization problems.

A group of researchers led by Toshiyuki Nakagaki from the Hokkaido University in Japan, placed Physarum polycephalum in a petri-dish scattered with oat flakes. The position of food scraps was deliberately placed to replicate the locations of some of the most visited site in Tokyo. In the first few hours, the slime mold’s size grew exponentially, and it branched out through the entire edible map. Within a few days, the size of its branches started to shrink, and the slime mold established a complex branching network between the oats on the petri-dish. Despite growing and expanding without a central coordination system like the brain, the mould had re-created an interconnected network made of slimes that looks almost exactly like the efficient, well-designed Tokyo subway system.

Comparison of the Physarum branching networks with the Tokyo subway networks

As you may know, the Tokyo’s rail system is one of the best in the world. With 102 train lines, it serves an estimated 14 billion passengers per year. Such a legendary metro system is the fruit of collaboration between community dwellings, civil engineering, urban planning over decades. However, the lowly slime mold solve this complex spatial problem in a matter of just a few days.

A beautiful map of the complex Tokyo subway system

Slime mold has been evolving on our planet for an estimation of at least 600 million years, and has survived through countless rounds of evolutionary competition. If we could capture the essence of this ancient adaptive network formation system and summarize it in to engineering and biological models, it will certainly inspire new algorithms that guides network construction many domains.

—-Ran Bi