Pure Home Water, Ghana manufactures and distributes AfriClay Filters in an effort to bring clean water to 1 million people. So far they have delivered filters to provide 100,000 people clean water.
The process is simple. Water is placed in a clay filter and gravity pulls the water through the pores left in the clay during firing.
Sediment and bacteria are filtered out in several ways:
Physical straining: the particles are too large to fit through the pores in the clay
Sedimentation or adsorption: particles come to rest on or stick to the clay
Inertia: friction in the pores keeps the particles from passing through
Bacteria are also killed by a coating of colloidal silver (a disinfectant), which we apply to all filters that pass our quality control tests. While sediment and bacteria are filtered out, the molecules of water are small enough to pass through the pores in the clay.
The filters are sold to those who will use them. The effort has shown a willingness to pay by villagers in remote Northern Ghana (those earning < US$1/day). I imagine (I am just guessing) the prices are subsidized; in the last decade more (most?) appropriate technology solutions will have those benefiting pay something for the benefits they receive.
My nephews are working on a similar effort in India, using bio sand filters, I plan to post more on that later. There is current a campaign to help fund the delivery of water filters to Indian villages.
Hummingbirds and insects have evolved for sustained hovering ﬂight from vastly different ancestral directions, and their distinct phylogenies underlie the differences in their aerodynamic styles. In all other birds—and, presumably, hummingbird ancestors—the downstroke provides 100% of weight support during slow ﬂight and hovering. Given that many birds possess the mass-speciﬁc power (using anaerobic metabolism) to hover for short periods, the selective pressure on hummingbird ancestors was probably for increased efﬁciency (resulting in stiff wings with greatly simpliﬁed
kinematics), and an upstroke muscle (the supracoracoideus) that makes the recovery stroke rapid, while contributing enough to the hovering power requirements to allow the downstroke muscle (the pectoralis) to operate within its aerobic limits.
In other words, this pseudosymmetrical wingbeat cycle is good enough, and although hummingbirds do not exhibit the elegant aerodynamic symmetry of insects, natural selection rewards ‘good enough’ as richly as it does our aesthetic ideals
You will learn things like why it is so important to chew your food well (increase the surface area for enzymes to get at the food). Our bodies also have adapted to provide a huge surface area for the digestive system to work; the small intestine alone has a surface area of 250 square meters (larger than the size of most apartments). Your small intestine is 4.5 to 10.5 meters long.
Fun video showing how scientists use Lego Mindstorm robots to aid research into creating artificial bones. Lego Mindstorm robots are useful at a very reasonable price.
The webcast also includes this practical quote from Michelle Oyen, lecturer in the Department of Engineering at Cambridge University: “without your bones you would be a pile of goo lying on the floor.”
Another very good webcast on a science topic from Crash Course. It is packed with info, thankfully you can pause and rewind as much as you need. Well normally you can, YouTube decided to not let me do that just now 🙁
This webcast is packed with information on the makeup and function of eukaryotic cells, which are the type of cells found in animals. It is part of a interesting series of science webcasts by Crash Course. The webcast style might be a bit too hyperactive and flippant for some but the content is quite interesting and the videos they are are of similar style and quality so if you like this one you can subscribe to their channel. They offer quite a few webcasts on science but they also offer webcasts on history.
Very cool. Very good job by University of Cambridge to make this kind of material available openly online. I find this kind of video amazing. Every day you body has this going on all day long. How amazing.
This was shot by University of Cambridge medical researcher Alex Ritter, and is 92 times faster than real time.
Cells of the immune system protect the body against pathogens. If cells in our bodies are infected by viruses, or become cancerous, then killer cells of the immune system identify and destroy the affected cells. Cytotoxic T cells are very precise and efficient killers. They are able to destroy infected or cancerous cells, without destroying healthy cells surrounding them.