Science – Page 106 – a sibilant intake of breath

Peering into metal with muons

When cosmic rays collide with molecules in the upper atmosphere, they produce particles called muons. About 10,000 of these strike every square metre of the earth’s surface each minute. These particles are able to penetrate several tens of metres through most materials, but are scattered to an unusual extent by atoms that include large numbers of protons in their nuclei. Since this includes uranium and plutonium, muons could have valuable security applications.

Muon tomography is a form of imaging that can be used to pick out fissile materials, even when they are embedded in dense masses. For instance, a tunnel sized scanner could examine entire semi trucks or shipping containers in a short time. Such tunnels would be lined with gas-filled tubes, each containing a thin wire capable of detecting muons on the basis of a characteristic ionization trail. It is estimated that scans would take 20-60 seconds, and less time for vehicles and objects of a known configuration.

Muons have also been used in more peaceful applications: such as looking for undiscovered chambers in the Pyramids of Giza and examining the interior of Mount Asama Yama, in Japan.

Desalination

Water scarcity is a frequently discussed probable impact of climate change. As glaciers and snowcaps diminish, less fresh water will accumulate in the mountains during the winter; that increases both flooding (during wet seasons) and drought. Higher temperatures also increase water usage for everything from irrigation to cooling industrial processes. Given the extent to which the world’s aquifers are already depleted (see: Ogallala Aquifer), relatively few additional natural sources exist.

The big alternative to natural sources is the desalination of seawater. This is done in one of two ways: using multistage flash distillation or reverse osmosis. About 1,700 flash distillation plants exist in the Middle East already, processing 5.5 billion gallons of seawater per day (72% of the global total). These plants use superheated steam, a by-product of fossil fuel combustion, to pressurize and heat a series of vessels. As salt water flows into each successively lower pressure vessel, it flash boils. Condensers higher in the vessel cause the fresh water to precipitate out from the hot pressurized air solution. This is a simple process, but an energy intensive one.

Reverse osmosis, by contrast, uses a combination of high pressure pumps and specialized membranes to desalinate water. Essentially, the pressure drives fresh water through the membranes more quickly than the accompanying salts. As such, it is progressively less saline with each membrane crossing. In this process, there are both relatively high energy requirements (for high pressure pumping) and the costs associated with building and maintaining the membranes. Because it can be done at different scales, portable reverse osmosis facilities are the preferred option for combat operations or disaster relief.

Unfortunately, both processes are highly energy intensive. Particularly when that energy is being generated in greenhouse gas intensive ways, this is hardly a sustainable solution. Part of the solution is probably to sharply reduce or eliminate water subsidies – especially for industry and agriculture. More transparent pricing should help ensure that the whole business of desalination is only undertaken in situations where the need for water justifies all the expenses incurred.

Opiates and pain control

This rather heart-wrenching article from the New York Times discusses the shortage of pain-killing opiates for medical care in the developing world. This is more the consequence of (seemingly misguided) policies than of poverty. The issue was touched upon here earlier, as part of this discussion on the Afghan opium crop.

Hydrogen and AAs

At a party this weekend, I had a conversation with someone who believed that the energy needs of the future would be solved by hydrogen. Not hydrogen as the input for nuclear fusion, but hydrogen as a feedstock for fuel cells and combustion engines. It’s not entirely surprising that some people believe this. For years, car companies have been spouting off about hydrogen powered vehicles that will produce only water vapour as emissions. The Chevron game mentioned earlier lets you install ‘hydrogen’ electricity generating capacity. The oversight, of course, is that hydrogen is just an energy carrier. You might as well say that the energy source of the future will be AA batteries.

AA batteries are obviously useful things. They provide 1.5 volts of power that you can carry around with you and use to drive all manner of gadgetry, but they are hardly an energy system unto themselves. The chemicals inside them that create their electrical potential had to be extracted, processed, and combined into a usable form. Inevitably, this process required more energy than is in the batteries at the end. The loss of potential energy is a good trade-off, because we get usable and portable power, but there is no sense in which we can say that AA batteries are an energy system.

A similar trade-off may well eventually be made with hydrogen. We may break down hydrocarbons, sequester the CO2 produced in that process, and use the hydrogen generated as fuel for cars. Alternatively, we might use gobs of electricity to electrolyse water into hydrogen and oxygen. Then, we just need to find a way to store a decent amount of hydrogen safely in a tank small, durable, and affordable enough to put in vehicles; build fleets of vehicles with affordable fuel cells or hydrogen powered internal combustion engines; and develop an infrastructure to distribute hydrogen to all those vehicles.

When you think about it, hydrogen seems less like a solution in itself, and more like the possible end-point of solving a number of prior problems. As far as ground vehicles go, it seems a safer bet to concentrate on improvements to rechargeable battery technology.

Betting on a long shot

While it is unwise to place too much hope in unproven technologies like carbon capture and sequestration or nuclear fusion as mechanisms to address climate change, there is also a good case to be made for expanded research and development in promising areas. As such, it is more than a bit regrettable that Canada withdrew participation from the largest international fusion research effort back in 2003. It may be a long shot and it may take fifty years or more to reach the point of commercial deployment, but fusion does seem to be one possible long-term option.

In addition to providing electrical power, fusion plants could also be used to produce hydrogen for vehicles by means of electrolysis. Depending on their ultimate ability to scale production up and down, they could also be important for peak power management. Even if we accept that 50 years may be an ambitious period for fusion technology to mature, it is possible that the first commercial fusion plants could be coming online just as coal plants built today are reaching the end of their lives.

Betting on a long shot isn’t always a bad idea – especially when it is one strategy among many alternatives.

New ideas in genetics

The high school biology version of genetics we all learned seems to be faring increasingly poorly, though that is no real surprise. The first actual human genome was sequenced recently. It belongs to J. Craig Venter, founder of Celera Genomics: the private firm that competed with the Human Genome Project to first map the human genome. Both groups used genetic material from multiple subjects and used mathematical tools that may have underplayed the level of genetic diversity that exists in human DNA.

Meanwhile, RNA is getting a lot more attention.

Some half-related earlier posts: the Global Ocean Sampling Expedition and the Human Microbiome Project.

Physics animations

If your math / physics geek tendencies have not been properly addressed lately, you may want to have a look at these physics related flash animations. They run from basic kinematics through to relativity, quantum mechanics, and chaos theory.

This method for evaluating the area of a circle as a limit is very intuitive. Lorenz attractors continue to confuse me, despite Wikipedia.

Shrimponomics

Here is an interesting blog post analyzing theories about why people are eating more shrimp than was previously the case. In short, people without training in economics seem to focus more on the demand side than people with such training.

One response that surprised me was “a rise in the number of vegetarians who will eat shrimp.” Now, if you are a vegetarian because you think it is wrong to kill cows and chickens for food, that may be a sensible position. If you are a vegetarian for general reasons of ecological sustainability, it is a lot less valid. As fisheries go, shrimp is one of the worst when it comes to bycatch. The UN Food and Agriculture Organization says that the present shrimp catch is at least 50% above the maximum sustainable level. Shrimp also tends to be collected through a process called bottom trawling: where large steel rollers smash and kill everything on the ocean floor.

Shrimp aquaculture is arguably even worse. There are all the problems attendant to all agriculture – close quarters, disease, harvesting other creatures unsustainably to turn into feed, antibiotics, etc – and then there is the fact that mangrove swamps are ideal for conversion into shrimp farms. The UN Environment Programme estimates that 1/4 of the total destruction of these important ecosystems has been brought about by shrimp farming.

From an ecological standpoint, vegetarianism (and probably veganism) remains a far preferable option, compared to eating meat.

Random numbers

Truly random numbers are hard to find, as patterns tend to abound everywhere. This is problematic, because there are times when a completely random string of digits is necessary: whether you are choosing the winner of a raffle or generating the one-time pad that secures the line from the White House to the Kremlin.

Using random radio crackle, random.org promises to deliver random data in a number of convenient formats (though one should be naturally skeptical about the security of such services). Another page, by Jon Callas, provides further information on why random numbers are both necessary and surprisingly tricky to get.

This comic amusingly highlights another aspect of the issue.

The Great Dying

251.4 million years ago, the earth experienced the most severe extinction event ever recorded. The Permian-Triassic (P-Tr) extinction event (informally referred to as the Great Dying) involved the loss of 90% of all extant species. This included about 96% of all marine species and 70% of terrestrial vertebrate species.

There are a number of theories about what caused the event:

A comet or meteor impact
Massive volcanic activity
Continental evolution
A supernova destroying the ozone layer
Methane clathrate release

Some combination of such factors may well be responsible. Regardless of the initial cause, one of the defining elements of the P-Tr event was a high degree of global warming. Mean global temperatures increased by about 6°C, with much higher increases at the poles. This period also involved the large-scale failure of ocean circulation, leaving nutrients concentrated at the ocean bottom and an acute lack of oxygen in the sea. The latter was the product both of decreased circulation and the large-scale die off of the kind of phytoplankton species that now produce about 90% of the planet’s oxygen.

The study of such historical occurrences is useful, largely because it helps to improve our appreciation for how climatic and biological systems respond to extreme shifts. Just as the re-emergence of life after a forest fire and a clearcut may have some common properties, perhaps the patterns of decline and reformation after the P-Tr event can offer us some insight into macro level processes of ecological succession after traumatic climatic events.