Aicm.v2

lady-tyrell:

wow this firefly haitus is really taking a while isnt it

Stanford engineers have built a basic computer using carbon nanotubes (CNTs), a semiconductor material that has the potential to launch a new generation of electronic devices that run faster, while using less energy, than those made from silicon chips.

This unprecedented feat culminates years of efforts by scientists around the world to harness this promising but quirky material.

The research is reported in an article on the cover of the journal Nature.

About 15 years ago, CNTs were fashioned into transistors, the on-off switches at the heart of digital electronic systems; however, inherent imperfections in CNTs have stood in the way of outing this promising material to practical use.

Firstly, CNTs do not necessarily grow in neat parallel lines, as chipmakers would like. Over time, researchers have devised tricks to grow 99,5 per cent of CNTs in straight lines. But with billions of nanotubes on a chip, even a tiny degree of misaligned tubes could cause errors, so that problem remained.

Secondly, depending on how the CNTs grow, a fraction of these carbon nanotubes can end up behaving like metallic wires that always conduct electricity, instead of acting like semiconductors that can be switched off.

The Stanford engineers found a way to deal with misaligned and/or metallic CNTs without having to search for them. They call their two-pronged approach an “imperfection-immune design”.

To eliminate the wire-like or metallic nanotubes, the Stanford team switched off all the good CNTs. Then they pumped the semiconductor circuit full of electricity. All of that electricity concentrated in the metallic nanotubes, which grew so hot that they burned up and literally vapourised into tiny puffs of carbon dioxide. This sophisticated technique eliminated the metallic CNTs in the circuit.

Bypassing the misaligned nanotubes required even greater subtlety. The engineers sorted this problem out by creating a powerful algorithm that maps out a circuit layout that is guaranteed to work no matter whether or where CNTs might be askew.

The Stanford team used this imperfection-immune design to assemble a basic computer with 178 transistors, a limit imposed by the fact that they used the university’s chip-making facilities rather than an industrial fabrication process.

Their CNT computer performed tasks such as counting and number sorting. It runs a basic operating system that allows it to swap between these processes. In a demonstration of its potential, the researchers also showed that the CNT computer could run MIPS, a commercial instruction set developed in the early 1980s by then Stanford engineering professor and now university President John Hennessy.

The new Stanford approach could very well lead to the mass production of carbon nanotube semiconductors and points to a new generation of electronic devices beyond silicon.

– Tom Abate | Stanford University

Source: Stanford University

Story and pictures by Sean Woods

Soaring electricity tariffs and an over-burdened national grid – it’s no wonder many budget conscious, blackout-wary homeowners are opting for solar geysers. This makes perfect sense: after all, domestic geysers are responsible for up to half of our monthly electricity spend, and the one thing our country has in abundance is sunshine. Right?

If only things were that simple. Although solar water heating systems and our sun-drenched skies theoretically make for a perfect match, in practice, there are a few drawbacks for the unwary. First off: most solar water heating systems require regular care and maintenance to remain in optimal operating condition, and because many homeowners tend to forget about them once they’ve been installed, failure rates tend to be high.

Even diligent maintenance doesn’t guarantee that you’re able to enjoy a hot shower for the foreseeable future; one decent Highveld hailstorm can demolish your system in under a minute. The uncomfortable fact is that our region’s unique set of environmental conditions make strong demands on solar heating systems, and until now, the only designs available were conceived in climes very different from ours. The obvious solution was to develop a system from scratch – which is exactly what Gauteng’s Etienne Holder has done with his newly patented Novasun solar water heating system.

With over 15 years in the geyser manufacturing game – much of it spent working closely with solar manufacturers and installers – Holder has an intimate understanding of the issues facing current solar water heating (SWH) systems.

He explains: “As solar became more popular, we began noticing the shortcomings of imported systems. We have one of the highest radiation levels in the world and, as most SWH systems available here are best suited to colder European conditions, they take an absolute hammering.”

The list of things that can go wrong is a real eye-opener. Stagnation, where the system overheats because of underuse, is a huge issue, especially for evacuated (EV) tubes. Holder elaborates: “Runaway heating can cause internal temperatures to rise as high as 200 degrees. Apart from creating a serious safety hazard, this degrades the insulation around pipes, drastically reduces the life of the water cylinder, and ultimately, wastes water by causing the safety valve to open and dump it on to your lawn.”

At the opposite end of the scale, as ambient temperatures drop below zero, is the issue of freezing. This causes water trapped in flat-panel systems to expand and pop their copper channels. Then, when it gets warmer, you effectively end up with an expensive, leaking sieve bolted to your roof. Says Holder: “In 2010, one company alone lost a few hundred systems due to a big freeze. It had a huge impact on the solar and insurance industries as a whole.”

To overcome the problem, indirect heating systems – where the panel is filled with an anti-freeze solution that passes through a heat transfer unit – were developed. However, the antifreeze needs to be topped up on a regular basis and replaced biannually, which adds to the hassle factor. There’s also a drop in efficiency of at least 30 per cent because the water’s not heated directly. Says Holder: “This means that much of the electricity savings you’re supposedly making by purchasing the unit get ploughed back into the system to keep it running.”

Water quality’s a big problem, too. “You just have to read the newspapers… our water quality is deteriorating. Many areas now have very high levels of dissolved solids in the water, which blocks pipes in the panels and renders them ineffective. To remove the sludge, we have to disconnect everything and flush the system with mild acid. It’s a huge job. Even then, we’re lucky if we manage to get half of it out. Municipalities are also forced to add excessive amounts of chlorine to the water to kill bacteria; this plays havoc with the stainless steel components.” Lastly, the complexity of many systems doesn’t make for easy installation, which confuses both the installer and homeowner. Says Holder: “The only folk who seem to understand them are the manufacturers.”

According to Holder, most consumers are caught between a rock and a hard place. “Cheap systems are financially accessible, but don’t last long. And good systems are so prohibitively expensive that any chance of you recouping your costs over the guarantee period is highly unlikely.”

Realising the only real option was to develop a local solution, Holder began applying his mind. Working with his long time business partner Walter Hupertz, his goal was to create a system that didn’t stagnate or freeze, was hail-resistant and cost-effective. It also had to be totally maintenance-free, easy to install, and “something he could guarantee for a long period of time”.

After two years of effort, they got it right. Says Holder: “Truth be told, we first thought EV tubes were the answer. However, because they were designed for arctic conditions, they’re just too efficient. Most people prefer flat panel collectors, but these also have serious drawbacks.” Eventually, the two men settled on a combination of the best attributes of both to create a completely new hybrid system. “Basically, we took inspiration from EV tubes, took ideas from flat panel designs, then threw our own five cents’ worth into the mix.”

Inside its flat panel collector, the Novasun system features thin copper tubes, all of which have been laser-welded on to the collector sheet. Inside each of the hermetically sealed tubes is just 7 ml of fluid, described as a “special mix of herbs and spices” that eliminates any possibility of freezing. As the fluid heats up, it becomes a gas, rising to dissipate its heat into a heat exchanger and warm the water. The gas then condenses and falls to the bottom of the tubes and the cycle is repeated. Once the water inside the heat exchanger reaches a temperature of about 65 degrees, the gas can no longer condense and the cycle is halted, preventing stagnation.

The unit is enclosed by a sheet of low-iron boron glass, making the entire collector completely hail-proof. It’s connected to Holder’s proven Solartherm water cylinder, which employs a cross-linked polyethylene (PEX) lining to prevent any grime build-up from dirty water. The complete system is reportedly very easy to install.

The Novasun SWH system has been awarded the SABS mark of approval and is already on Eskom’s rebate system. A 200-litre unit is expected to cost around R17 500 (including installation) and comes with a 10-year unconditional guarantee. Says Holder: “What we’re bringing to the table here is a simple, one-size-fits-all solution. It works equally well on a shack as it does in a posh suburb such as Houghton.”

For more information, contact Solar Assist on 0861 106 618 or visit www.solarassist.co.za

Last week, before we headed out for the weekend, I had a brief exchange with Ben Lillie on Twitter, prompted by the following set of tweets:

OK, here's a thing. I'll often hear people complain that Hollywood gets science wrong because there's *1* scientist who does everything 1/3

— Ben Lillie (@BenLillie) September 27, 2013

But in reality, science is massively collaborative. So why can't storytellers get that right? 2/3

— Ben Lillie (@BenLillie) September 27, 2013

*BUT* at the same time we have, and wildly celebrate, the Nobel, which embodies exactly that myth. 3/3

— Ben Lillie (@BenLillie) September 27, 2013

I sort of feel obliged to respond to this, because I’m both a person who has complained about the lone scientist myth in movies and a guy who’s running a Nobel Prize betting pool, increasing the hype for the upcoming awards (to the infinitesimal degree that I can contribute, anyway). But as I said to Ben, it doesn’t fit well within Twitter’s character limits. The short version, though, is that the Nobel Prizes are basically like The Big Bang Theory on tv.

By that, I don’t mean that they’re a sitcom with an obtrusive laugh track– though there are some comical aspects to the overall pomposity of the event. (OBNobelStories: when Bill Phillips won back in ’97. he created a small stir by blowing a kiss to his wife when he bowed to the audience after receiving the medal, and the Literature laureate, Dario Fo, was ostentatiously sleeping during the boring introductory speeches.) Instead, I mean that both are cultural icons that are a bit controversial and somewhat problematic in terms of their portrayal of science but I think on balance they do more good than harm.

In the case of the Nobels, the primary source of controversy is, as Ben mentioned, the fact that they’re awarded to small number of individuals. This creates an incorrect perception of the business of science as something done by brilliant individuals on their own, when in fact the bulk of the work is done in teams. This is exacerbated by the entirely arbitrary limitation to three recipients, which often leads to deserving scientists being shut out entirely. This is getting a bit more attention these days because the Higgs boson is an obvious candidate for a Nobel in the near future, but there are at least half a dozen physicists with a reasonable claim to the idea. But even with lower profile subjects, there are always a few people with a beef after the announcements are made– the grad students and post-docs who did the real work for which the laureate is being honored, or competitors who had similar results at around the same time, and so on.

In the case of The Big Bang Theory, the problem is more one of image. There’s still a lone genius problem– none of the characters have anywhere near enough collaborators to be actual scientists– but the main source of controversy is that they play as broad stereotypes. They’re not socially adept in any conventional sense, or physically attractive, and their personalities are just collections of nerd signifiers. A fair fraction of physicists roll their eyes when the show gets brought up, and some are deeply annoyed by the perpetuation of unflattering stereotypes about physicists.

On balance, though, I think the show probably ends up being a positive thing– and I say this as someone who would have some reason to complain about the stereotyping. In the end, though, what saves it (for me– this is just opinion, mind) is that for as much as the principal characters are broad nerd stereotypes, at least in the episodes I’ve seen, they are also unquestionably the heroes of the piece. The real focus for audience identification seems to be the character of Leonard, but the plot structure pushes the audience very strongly to root for the science nerds– in the handful of episodes that bring “normal” people into the picture, they either end up as the butt of jokes, or as the villains of the episode. (This is actually the factor that keeps me from watching– I’m not wild about the stereotyping, but the ham-fisted plotting is much harder to take…)

There are unquestionably problems with the show and the characters, and I can totally see how somebody else could decide that the overall package breaks in a different way. But ultimately, I end up feeling that the benefit of getting a massive audience to root for such ostentatious nerd stereotypes is enough of a positive factor to outweigh the negatives of the stereotyping.

Similarly, with the Nobels, I agree that the “lone genius” aspect of the thing is problematic, and they may in some small way encourage cutthroat behavior on the part of elite scientists. But on the other hand, this is the one event every year that’s guaranteed to put science on the front page of major national newspapers in a positive light. They’re not the only story of the year, by any stretch, but with the Nobels, you know you’re going to get a “Hey, look, here’s some amazing science stuff!” frame, where a lot of other high-profile science stories are much more ambiguous, or even negative. October is the one month when I know I will get faculty colleagues from other departments asking me to explain some cool point of physics in a way that is genuinely excited and curious.

That kind of unambiguously positive buzz, which happens on a very broad scale, makes up for a little bit of hard feelings and excessive valorization of individuals. Again, this is just my opinion, and I can see how somebody else might decide that the balance tips the other way, but as far as I’m concerned, the Nobels are a good thing for science on the whole, and I’m happy to have them as an annual celebration of science.

(The original images used to make the composite in the “featured image” above come from here and here.)