allotrope – Page 58 – Akshat Rathi

Stronger than ceramic yet supple as metals

February 14, 2010December 30, 2013 Akshat RathiLeave a comment

Strong materials like ceramic are brittle while ductile materials like metals are weak. Researchers at the California Institute of Technology have developed a material that has ceramic-like strength and metal-like ductility. They have achieved this feat through the use of zirconium based metallic glasses and nano-sized pillared structure.

Metallic glass is by no means a new concept, it was first reported in 1960 and has since attracted a lot of attention owing to their superior mechanical properties like high strength and large elastic strain. Amorphous metal, more commonly known as metallic glass, are non-crystalline metallic materials. They are generally produced by rapid cooling of an alloy that has three or more components in it. These alloys achieve their advantages by using atoms of significantly different sizes which results in low free volume, thus higher viscosity. Although they are have poorer electrical and thermal conductivity than metals, the non-crystalline structure avoids crystal defects like grain boundaries and dislocations thus increasing resistance to erosion and corrosion.

Nanopillars — Scanning Electron Microscope image of a typical nanopillar

Jang and Greer fabricated nano-sized pillars (see image) from a bulk metallic glass (Zr35Ti30Co6Be29) using an ion beam to etch the material into its final form. They were able to achieve superior strength of 2.25 GPa (which is equivalent to an elephant standing on 1 sq.cm of that material) and plastic deformability of ~25% by reducing the size to ~500 nm diameter nano pillared structure. At a size reduction to 100 nm, the strength remained same and plasticity was homogeneous. Such high strength has never been reported without sacrificing on the ductility of the material.

With such strength and resistance to erosion, these materials can find application in nanoimprint lithography making nanomolds which are currently silicon-based, expensive and get very easily damaged. Amorphous materials have previously also found use as biomaterials typically as implants in bones. It is possible to control their rate of dissolution by varying the contents of the alloy and thus become implants which eventually get replaced by bone tissue.

Jang, D., & Greer, J. (2010). Transition from a strong-yet-brittle to a stronger-and-ductile state by size reduction of metallic glasses Nature Materials DOI: 10.1038/nmat2622

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How to stay awake for 22-hours everyday?

January 22, 2010December 30, 2013 Akshat Rathi4 Comments

Physicists have not yet found a way to alter the Earth’s speed of rotation to give us a thirty-hour day, but sleep researchers may have found a way to get an eight-hour sleep in just two hours—letting you cram in six more wakeful hours a day. The key to this superhuman ability is polyphasic sleeping, a form of sleeping which was first reported was reported in Time Magazine in 1943. Buckminster Fuller, the great inventor and futurist, trained himself to take a half-hour nap every six hours, a pattern which he maintained for two years. This was the first polyphasic sleep schedule invented, and is known as Dymaxion sleep.

Today, there exist three polyphasic sleep schedules; Everyman, Uberman and Dymaxion in the decreasing order of sleep. Little scientific research has been done to show the safety of such sleep schedules, but enough proof exists for a thriving community of polyphasic sleepers. The longest scientific experiment was performed on a single subject, Francesco, by the founder of the Chronobiology Research Institute, Claudio Stampi. Francesco followed a schedule of sleeping for twenty minutes every four hours, now known as the Uberman sleep schedule. After the 48-day study, Stampi reports in his book, Why we nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep that Francesco’s performance did not seem to suffer as a result of adopting the polyphasic sleeping pattern. The studies showed a change in the brain wave pattern during the short naps. It is only recently that a greater understanding of these brain wave patterns has been developed.

Natural sleep is divided into rapid eye movement (REM) sleep and non-REM (NREM) sleep. In normal sleeping REM sleep is observed only at the end of a 90-minute cycle. REM sleep is associated with dreaming and consolidation of memories. However, when deprived of sleep, as in polyphasic sleeping, subjects fall into REM sleep within minutes of starting a nap. Based on these observations, polyphasic sleepers believe that REM sleep is the most important form of sleep & the brain when deprived of sleep capitalises on any chance to sleep in this mode. The online community of people who adapted themselves to the Uberman schedule reports on the blogosphere that they achieve heightened alertness and concentration when fully adapted. Polyphasic sleeping also seems to induce lucid dreaming, a form of dreaming in which the dreamer can consciously participate in the dream.

These anecdotal theories gained some credence in a study recently published in PNAS, which shows that REM sleep is responsible for improving associative networks in the brain. The study involved 77 young adults who were given a number of creative tasks in the morning. They shown multiple groups of three words (such as: cookie, heart, sixteen) and asked to find a fourth word that can be associated to all three words (like sweet). Later in the day, some were allowed a nap, and monitored using brain scans to see what kind of sleep they entered. They were then given the same and new tasks. For the same tasks, the passage of time and sleep allowed them to “incubate” their thoughts and come up with better and more varied solutions. However, for new tasks those participants that entered REM sleep improved by almost 40% over their morning performances.

If these theories are proven on a scientific basis, does it mean that people on polyphasic sleep schedules not only sleep less but are also capable of performing better than normal people? That seems a little counter-intuitive, but a fast growing community of polyphasic sleepers is trying to prove otherwise. More research in this field can lead to development of medically-endorsed techniques which could let to polyphasic sleeping being rolled out to a wider community.

Also published on Cherwell’s Science Blog: Matters Scientific

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