We are currently using a centralized production model for this isotope with just a six hour half-life. This model involves just a handful of dedicated, government-funded research reactors, producing molybdenum-99 from highly enriched uranium (which is another issue for another time). Moly, as we’ve come to affectionately call it, decays via beta emission to technetium, and when packaged into alumina columns, is sterilized, and encased in a hundred pounds of lead. It is then shipped by the thousands to hospitals around the world. The result: the world has come to accept Tc-99m, which is used in 85% of the 20 to 40 million patient scans every year as an isotope available from a small, 100 pound cylinder that was replaced every week or so, without question, without worry. Moly and her daughter were always there…but in 2007 and again in 2009, suddenly they weren’t. The world had come to realize that something must be done.
Distributed solutions can be more robust than centralized solutions, especially if coordination problems plague the central model. Here is a great example of how distributed production of Tc 99 may be superior to centralized manufacturing.
The great weakness of distributed models centers around communication, and when the task being distributed requires little to no communication, distributed solutions usually scale very well (e.g., image processing).
Posted by Fred on March 21, 2012
We now have yet another indication that neutrinos cannot travel faster than the speed of light after all, provided by a neighbor of the OPERA detector that set off the fuss in the first place. OPERA’s detector sits deep underground at Gran Sasso in Italy, where it receives neutrinos from a beam generated at CERN, 730km away on the French-Swiss border. Because the neutrino beam spreads out over the intervening distance, it’s possible to run multiple detectors at the same site, all listening in on the same beam. The team running one of Gran Sasso’s other detectors (called ICARUS) has now performed time-of-flight measurements on neutrinos and determined that they don’t seem to be moving faster than light.
Both ICARUS and OPERA use the same neutrino source, and so have the same clocking capabilities. ICARUS uses a slightly different technique to detect neutrinos, but without some compelling explanation for the new data, it is safe to put the OPERA results down as “likely experimental error.” Relativity wins the day, again.
Posted by Fred on March 16, 2012
Instead, the genetic analysis shows, modern humans encountered and bred with at least two groups of ancient humans in relatively recent times: the Neanderthals, who lived in Europe and Asia, dying out roughly 30,000 years ago, and a mysterious group known as the Denisovans, who lived in Asia and most likely vanished around the same time.
Apparently, modern human DNA varies quite a bit across the globe. Humans outside Africa have around 2.5% Neanderthal DNA, and some Asian communities have around 5% Denisovian DNA. Southeastern Asians have both Neanderthal and Denisovian DNA. Modern humans have been the only human species since Homo floresiensis died out about 17,000 years ago. We don’t know how much, if any, H. floresiensis DNA is present in modern humans, because we don’t have any well-preserved DNA for that species.
There is no hard and fast rule about what distinguishes one species from another, but the fact that modern humans apparently interbred with at least two now-extinct human species may have been responsible for some of our disease resistance. The fact that these genes survived and spread from a small number of hybrid offspring indicates the genes increased the hardiness of modern humanity.
Posted by Fred on March 8, 2012