Tallis vs Eagleman

post from Top stories on 06 May 2012 10:51:58 AM. © Top stories

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The Observer has a discussion between Tallis and

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http://machineslikeus.com/news/tallis-vs-eagleman

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Astronomers Discover a Rare Stellar Disk of
Quartz Dust

post from CR4 - Recent Blog Entries on 06 May 2012 10:26:10 AM. © CR4 - Recent Blog Entries

From Phys.org - latest science and technology news stories: A research team of Japanese astronomers led by Dr. Hideaki Fujiwara (Subaru Telescope) has discovered a main-sequence star that is surrounded by a rare disk of quartz dust. Collisions of planetesimals, building blocks for planet

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http://cr4.globalspec.com/blogentry/19803/Astronomers-Discover-a-Rare-Stellar-Dis
k-of-Quartz-Dust?from_rss=1

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European Space Probe to Search for Life on
Jupiter's Icy Moons

post from CR4 - Recent Blog Entries on 06 May 2012 10:19:31 AM. © CR4 - Recent Blog Entries

From Tech News Headlines - Yahoo! News: The European Space Agency (ESA) announced this week that it's spending $1.3 billion on a 2022 mission to explore Jupiter's largest moons. Watch the video above to see why scientists are hopeful that the Jovian system is a sweet spot for extraterres

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http://cr4.globalspec.com/blogentry/19802/European-Space-Probe-to-Search-for-Life
-on-Jupiter-s-Icy-Moons?from_rss=1

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Blue Origin Dishes More Details on its
Bezos-Backed Spacecraft

post from CR4 - Recent Blog Entries on 06 May 2012 10:11:24 AM. © CR4 - Recent Blog Entries

From Engadget: Blue Origin typically keeps pretty tight-lipped about its projects. The private space-travel firm claims it prefers to talk about what is has done, rather than what it hopes to do. As such, We recently heard about its "Space Vehicle" (that's its actual name,) having comple

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http://cr4.globalspec.com/blogentry/19801/Blue-Origin-Dishes-More-Details-on-its-
Bezos-Backed-Spacecraft?from_rss=1

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Jupiter, acting all superior

post from Bad Astronomy on 06 May 2012 09:00:45 AM. © Bad Astronomy

This is a cool picture: What you’re seeing is from the NASA/ESA satellite Solar and Heliospheric Observatory, or SOHO. It stares at the Sun all the time, monitoring its activity. This image, from May 3, 2012 is from the LASCO C3, one of the cameras[...]

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http://feedproxy.google.com/~r/BadAstronomyBlog/~3/nyWUHKlZnCo/

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Using Nanocomposites to Improve Dental Filling
Performance

post from Curious Cat Science and Engineering Blog on 06 May 2012 08:15:19 AM. © Curious Cat Science and Engineering Blog

After a dentist drills out a decayed tooth, the cavity still contains residual bacteria. Professor Huakun (Hockin) Xu says it is not possible for a dentist to remove all the damaged tissue, so it’s important to neutralize the harmful effects of the bacteria, which is just what the new nanocomposites are able to do.

Rather than just limiting decay with conventional fillings, the new composite he has developed is a revolutionary dental weapon to control harmful bacteria, which co-exist in the natural colony of microorganisms in the mouth.

“Tooth decay means that the mineral content in the tooth has been dissolved by the organic acids secreted by bacteria residing in biofilms or plaques on the tooth surface. These organisms convert carbohydrates to acids that decrease the minerals in the tooth structure,” says Xu, director of the Division of Biomaterials and Tissue Engineering in the School’s Department of Endodontics, Prosthodontics and Operative Dentistry.

The researchers also have built antibacterial agents into primer used first by dentists to prepare a drilled-out cavity and into adhesives that dentists spread into the cavity to make a filling stick tight to the tissue of the tooth. “The reason we want to get the antibacterial agents also into primers and adhesives is that these are the first things that cover the internal surfaces of the tooth cavity and flow into tiny dental tubules inside the tooth,” says Xu.

The main reason for failures in tooth restorations, says Xu, is secondary caries or decay at the restoration margins. Applying the new primer and adhesive will kill the residual bacteria, he says.

Fillings made from the School of Dentistry’s new nanocomposite, with antibacterial primer and antibacterial adhesive, should last longer than the typical five to 10 years, though the scientists have not thoroughly tested longevity. Xu says a key component of the new nanocomposite and nano-structured adhesive is calcium phosphate nanoparticles that regenerate tooth minerals. The antibacterial component has a base of quaternary ammonium and silver nanoparticles along with a high pH. The alkaline pH limits acid production by tooth bacteria.

The new products have been laboratory tested using biofilms from saliva of volunteers. The Xu team is planning to next test its products in animal teeth and in human volunteers in collaboration with the Federal University of Ceara in Brazil.

Bringing products into the market, after preliminary research success is very difficult. I once made some money shorting a stock, Enamelon, that was targeting the regeneration of enamel. Short selling is when you sell it before you buy it, anticipating a decline in price. This research on does seem to hold promise, I hope it pans out and we can take advantage of these improvements.

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http://engineering.curiouscatblog.net/2012/05/06/using-nanocomposites-to-improve-
dental-filling-performance/

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Travelling Salesman - the Movie

Science in the movies is a topic we've looked at a few times here on the blog. But this one is for the pure mathematicians. Check out this preview to the upcoming flick "Travelling Salesman".

I love these kinds of films - overly melodramatic acting, a slight misrepresentation of the science behind the plot (which is OK by me as this is a movie), government conspiracies, and mysterious music. The name "Travelling Salesman" comes from the famous mathematical Travelling Salesman Problem in which a salesman needs to visit a numerous destinations and wishes to do it in the shortest time. Whilst this may seem to be a simple problem, it is one of the most studied problems in mathematics. The more destinations involved, the more difficult to solve and in general there is no algorithm that can find the best answer. Brute force methods (that is, computing every possible solution and then finding the best) are computationally difficult, and with too many destinations, impossible. Hence mathematicians often use heuristics which find good, although not necessarily optimal, solutions quickly.

The premise of the movie is that the famous P vs NP problem has been solved. I'm not a pure mathematician, so I'll do my best here... P problems are those whose solutions can be found quickly (in Polynomial time, hence the P). NP problems are those whose solutions can not be found quickly, but if somehow a solution is produced using some extra information, it is easy to check that this solution is the best one (in polynomial time). Solving these problems take Non-deterministic Polynomial time - hence NP. A good example to show this is a jigsaw puzzle - finding a solution may be very difficult (and it's probably most accurate to image a blind person doing the puzzle), but it only takes a quick glance to see if any solution is correct.

The question that mathematicians ask is whether P=NP - which means, are there algorithms out there that solve seemingly NP problems in polynomial time? We haven't found any yet and mathematicians tend to think that P does not equal NP, but there is currently no proof. Proving this one way or the other is one of the seven Millennium Prize Problems selected by the Clay Mathematics Institute and carries a US$ 1,000,000 prize for the first correct solution.

But why do we care? One of the reasons is that modern cryptography is based on the fact that P does not equal NP - this is the premise of the movie. Modern codes start with a pair of large prime numbers p₁ and p₂ and multiply them together to give m=p₁p₂. The number m is released to the public, but p₁ and p₂ are kept secret. To crack the code you have to findp₁ and p₂, given the value of m. It turns out that finding the prime factors of large numbers (100+ digits) is exceptionally difficult, although checking an answer is very easy. It is thought to be an NP problem. But if indeed P does equal NP, this suggests that out there somewhere is an algorithm that could solve this problem in quick time, meaning that modern encryption codes are vulnerable.

They don't give too much away in the preview, but I suspect what happens is they prove P=NP, although the example of looking for something hidden in the desert seems like a P problem (you just check out under each grain of sand, which would be easy, although it's a nice illustration of the problem). We stretch the science here a bit - even if you prove P=NP, you still need to find the appropriate algorithm for the problem, which has never been done. But hey, it's a movie, and we don't pull Terminator up on its stretching of science!

There is a very good write up of the P vs NP problem over on Plus - check it out, it does a much more thorough job than I do!

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http://feedproxy.google.com/~r/MrSciencePodcast/~3/3rRY42XrZk4/travelling-salesma
n-movie.html

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What Is It for 5/6/12

This week's image:Check back on Wednesday for the answer!

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http://cr4.globalspec.com/blogentry/19775/What-Is-It-for-5-6-12?from_rss=1

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3D view of an unnamed lunar crater

Grab your red-blue 3D glasses and dive in to this small but spectacular unnamed lunar crater as seen in a Lunar Reconnaissance Orbiter photo.

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http://www.planetary.org/blogs/emily-lakdawalla/2012/05031308.html

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