K-MODDL > Tutorials > Reuleaux Triangle If an enormously heavy object has to be moved from one spot to another, it may not be practical to move it on wheels. Instead the object is placed on a flat platform that in turn rests on cylindrical rollers (Figure 1). As the platform is pushed forward, the rollers left behind are picked up and put down in front. An object moved this way over a flat horizontal surface does not bob up and down as it rolls along. The reason is that cylindrical rollers have a circular cross section, and a circle is closed curve "with constant width." Is a circle the only curve with constant width? How to construct a Reuleaux triangle To construct a Reuleaux triangle begin with an equilateral triangle of side s, and then replace each side by a circular arc with the other two original sides as radii (Figure 4). The corners of a Reuleaux triangle are the sharpest possible on a curve with constant width. Here is another really surprising method of constructing curves with constant width:
Scientists Uncover How Dainty Rhino Feet Support Huge Bodies | Despite Their Portliness, Rhinos' Feet Take It All in Stride | Rhinoceros Feet Explained How do rhinos' dainty little pigeon-toed feet support their portly bodies? A group of veterinary scientists in the United Kingdom are on the case. By coaxing three white rhinos to walk back and forth across a "pressure pad," a floor mat embedded with thousands of pressure sensors, the researchers are collecting data on how much force the beasts exert on different parts of their feet as they walk. A rhinoceros can weigh as much as 8,000 pounds (3,600 kilograms), yet somehow, their feet manage to take all those tons in stride. "Impressively, the peak pressures aren't that different from human feet (similar range of values), although the timing and distribution of pressures around the feet surely are different to some degree we haven't yet quantified," said John Hutchinson, professor of evolutionary biomechanics at the Royal Veterinary College's structure and motion laboratory and one of the researchers working on the study. White rhinos in Namibia.Credit: Ikiwaner | Creative Commons
SLCC - Learning Handouts Skip navigation links ugs : life and learning in sync Sanger Learning Center is UT Austin’s main resource for academic support. Each year, we help more than 20,000 students achieve their academic potential. We are open Monday through Friday, 8 a.m.-5 p.m. Come in for one-on-one or drop-in tutoringImprove your study skills with a learning specialistMeet weekly with a peer academic coachAttend free classes and workshops Learn how self-testing can better prepare you for your next exam.
Lab-made organ implanted for first time Scientists created an artificial trachea using polymers that had a spongy and flexible texture. In June, doctors implanted an artificial trachea into a 36-year-old manThe organ was created in a lab and bathed with the patient's stem cellsIt took away the need for the patient to wait for a donor organ (CNN) -- For the first time, a patient has received a synthetic windpipe that was created in a lab with the patient's own stem cells and without using human donor tissue, researchers said Thursday. Previous lab-generated transplants either used a segment of donor windpipe or involved tissue only, not an organ. In a laboratory in London, scientists created a trachea, which is a tube-like airway that connects at the voice box and branches into both lungs. On June 9, doctors implanted this synthetic windpipe into a 36-year-old man with late-stage tracheal cancer at Karolinska University Hospital in Stockholm. Tracheal cancers are extremely rare, accounting for less than 1% of all cancers.
Introduction to Evolutionary Biology Introduction to Evolutionary Biology Version 2 Copyright © 1996-1997 by Chris Colby[Last Update: January 7, 1996] volution is the cornerstone of modern biology. It unites all the fields of biology under one theoretical umbrella. It is not a difficult concept, but very few people -- the majority of biologists included -- have a satisfactory grasp of it. Misunderstandings about evolution are damaging to the study of evolution and biology as a whole. This is a brief introduction to evolutionary biology. What is Evolution? Evolution is a change in the gene pool of a population over time. The English moth, Biston betularia, is a frequently cited example of observed evolution. The increase in relative abundance of the dark type was due to natural selection. Populations evolve. Evolution can be divided into microevolution and macroevolution. The word evolution has a variety of meanings. Common Misconceptions about Evolution Evolution is not progress. Genetic Variation Natural Selection
THE CENTRAL NERVOUS SYSTEM The billions of neurons in the brain are connected to neurons throughout the body by trillions of synapses. The nervous system is organized into two parts: the central nervous system, which consists of the brain and the spinal cord, and the peripheral nervous system, which connects the central nervous system to the rest of the body. A schematic diagram of the divisions of the nervous system and their various subparts
Longevity Protein Discovered A protein that can extend the lifetimes of worms could have implications for human longevity and development of cancers, a new study suggests. Roundworms (C. elegans) born without the protien called arrestin lived a third longer than normal, while worms with triple the amount of the protein cut their lives short by one-third. The findings could have implications for humans, because most proteins in worms have human counterparts, according to study researcher Jeffrey L. "The links we have found in worms suggest the same kind of interactions occur in mammals although human biology is certainly more complicated," Benovic said. The roundworm is a useful model for studying human diseases and other aspects of human biology, because the worm is much simpler than humans but also has similarities to us. Taking advantage of this simplicity, Benovic and Aimee Palmitessa, a postdoctoral research fellow at the university, deleted the single arrestin gene in worms to see what would happen.
The Brain—Information about the Brain 1 Introduction “I think, therefore I am.” —René Descartes, 17th-century philosopher Few of us question the crucial importance of the brain. The brain makes up only 2 percent of our body weight, but it consumes 20 percent of the oxygen we breathe and 20 percent of the energy we consume. Scientists have worked for many years to unravel the complex workings of the brain. Despite these and other significant advances in the field of brain research, most of the processes responsible for the integrated functioning of billions of brain cells remain a mystery. An essential aspect of any scientific research is communicating results to the public in a way that is easily understood. To correctly interpret the information transmitted through these venues, we need a better understanding of basic concepts related to the brain. 2 Myths and Realities about the Brain As a result of the misinformation presented by various media, many people maintain misconceptions about the brain and brain function.