Science Sunday #24
Posted by Don McLenaghen on November 27, 2011
– and on the seventh day we learn.
Each week I hope to give a synopsis of the interesting science stories I have heard on my plethora of science podcasts I listen to each week plus anything I pick up scanning the inter-web. This week’s top stories:
This week’s top stories:
Filling in holes may make them more bright –
The nano scale world just never makes sense. In resent research published in Optics Express (published by Optical Society of America) showed that when holes in a metal plate were completely caped (i.e. the hole was covered completely) by a metal particle, up t0 70% MORE light passed through.
Their complete results report (i) the observation of light transmission through the holes blocked by the metal disks up to 70% larger than the unblocked holes; (ii) the observation of tuning the light transmission by varying the coupling strength between the blocking disks and the hole array, or by changing the size of the disks and holes; (iii) the observation and simulation that the metal disk blocker can improve light coupling from free space to a sub-wavelength hole; and (iv) the simulation that shows the light transmission through sub-wavelength holes can be enhanced, even though the gap between the disk and the metal film is partially connected with a metal.
Why is this important?
Current wisdom with regards when you want to block all light you can ignore the nano scale. In very sensitive optical instruments, such as microscopes, telescopes, spectrometers and other optical detectors, for example, it is common to coat a metal film onto glass with the intention of blocking light. Dust particles, which are unavoidable in metal film deposition, inevitably create tiny holes in the metal film, but these holes have been assumed to be harmless because the dust particles become capped and surrounded by metal, which is thought to block the light completely.
Conversely, on aspect of this discovery is the ability to fine tune the light. This approach may be used to make better and more accurate microscopes by boosting the amount and kind of light delivered to the target.
How does it work?
The metal disk acts as a sort of “antenna” that picks up and radiates electromagnetic waves. In this case, the metal disks pick up light from one side of the hole and radiate it to the opposite side. The waves travel along the surface of the metal and leap from the hole to the cap, or vice versa depending on which way the light is traveling.
Most people naively think that water freezes at 0o C. Some will know that you can supercool water below that point under special conditions but until research published in Nature, the absolute lower limit was not known.
Super-cooled liquid water must become ice at minus 55 F not just because of the extreme cold, but because the molecular structure of water changes physically to form tetrahedron shapes, with each water molecule loosely bonded to four others, according to the new study by chemists Valeria Molinero and Emily Moore.
The findings suggest this structural change from liquid to “intermediate ice” explains the mystery of “what determines the temperature at which water is going to freeze,” says Molinero.
However, in the strange and wacky world of water, tiny amounts of liquid water theoretically still might be present even as temperatures plunge below minus 55 F and almost all the water has turned solid — either into crystalline ice or amorphous water “glass,” Molinero says. But any remaining liquid water can survive only an incredibly short time — too short for the liquid’s properties to be detected or measured.
So, why is this important?
Atmospheric scientists studying global warming want to know at what temperatures and rates water freezes and crystallizes into ice. “You need that to predict how much water in the atmosphere is in the liquid state or crystal state,” which relates to how much solar radiation is absorbed by atmospheric water and ice, Molinero says. “This is important for predictions of global climate.”
Liquid water as cold as minus 40 F has been found in clouds. Scientists have done experiments showing liquid water can exist at least down to minus 42 F.
Why doesn’t it freeze at 0o C?
“If you have liquid water and you want to form ice, then you have to first form a small nucleus or seed of ice from the liquid. The liquid has to give birth to ice,” says Molinero. Yet in very pure water, like that can be found in the high atmosphere, no nucleation points are available.
God particle missing –
It seems physicists may soon be atheists all over again as their search for god turns up a blank. No, not god in the theological sense but the illusive ‘god particle’ (which it is not, and I hate articles the use the term…which means I hate this article – damn logic!).
There was much hope that the Large Hadron Collider would be able to discover the Higgs Boson, that theoretical sub-atomic particle that is supposed to provide mater its weight.
At a conference in Paris on 18 November, teams from ATLAS and the CMS experiments presented a combined analysis that wipes out a wide swathe of potential masses for the Higgs particle. Gone is the entire mass range from 141 to 476 gigaelectronvolts (GeV; energy and mass are interchangeable in particle physics). Together with earlier results from the 1990s, the analysis leaves a relatively narrow window of just 114–141 GeV in which the Higgs could lurk.
Analysis of the very latest data from this autumn — which Murray isn’t yet ready to share — will scour the range that remains. If it turns out to be empty, physicists may have to accept that the particle simply isn’t there.
What is the Higgs Boson? First, some background.
Four fundamental forces are at work in nature: gravity, the strong nuclear force, the weak nuclear force and electromagnetism. Since the mid-1960s, physicists have strongly suspected that the weak and electromagnetic forces are actually different aspects of a single ‘electroweak’ force. This is partly because the photon, the force-carrying particle of electromagnetism, is highly similar to the force-carrying particles of the weak force — the W and Z bosons. Moreover, a single electroweak theory successfully predicts the interactions of fundamental particles.
There is one problem, however: the W and Z bosons are extremely heavy, nearly 100 GeV, whereas the photon is massless. To explain the difference, a number of physicists (including Peter Higgs in 1964) proposed a new field and particle. The eponymous Higgs mechanism would interact with the W and Z bosons, giving them mass, but would ignore the photon, allowing it to remain massless. Relatively straightforward tweaks to the Higgs machinery allow it to endow other particles, such as quarks, with their observed masses as well.
What if it doesn’t exist?
Well, mostly it’s back to the drawing board. One theory holds that there is not A Higgs boson but a set of them. However, if that is true, finding THEM only amplifies the detection problem. The Higgs itself is only leaves a small mark as it decays into the W and Z boson; if there are 2 (or more) each will be leave an even small mark.
In Praise of Nuclear Power –
Just this week NASA launched Curiosity, a large rover to explore Mars. However, due to its size, the extent of the mission and the desire to ‘move quickly’; NASA decided not to use solar panels to provide power but opted for a nuclear power plant. Well, not nuclear so much as radioactive. The power supply does not use fission to provide power but heat generated by radioactive decay. The Multi-Mission Radioisotope Thermoelectric Generator is the latest “space battery” that can reliably power a deep space mission for many years
This will be the 26th mission using this style of power supply however the unit itself is the latest generation of “Radioisotope Thermoelectric Generator”. It currently provided 145 watts of power and weighs 44 kg; future versions are expected generate 250w while others are going for size generating only 50w but weighing only 7 kg. The biggest advantage to these is both the reliability and quantity (remember the farther from the sun, the less effective solar panel become) of power but they have a life time of 14 yrs +/-.
However there is an Achilles heal to this story. The radioactive source is Plutonium 238 was weapons production reactors…these have been shut down for over 2 decades. The stock pile NASA has is expected to run out by 2018. It takes about 8 yrs for current facilities to produce 5 kg at a current cost of 150 million. Curiosity is using about 5kg. The current state of US politics and the impending deadline means future outer-solar missions may be canceled due to lack of an appropriate power source.
Electronic Eye –
Babak Praviz of the University of Washington has demonstrated a first for contact eye wearers. He created and demonstrated the operation of a contact lens display powered by a remote radio-frequency transmitter in free space and on a live rabbit
The test lens was powered remotely using a 5-millimetre-long antenna printed on the lens to receive gigahertz-range radio-frequency energy from a transmitter placed ten centimetres from the rabbit’s eye. To focus the light on the rabbit’s retina, the contact lens itself was fabricated as a Fresnel lens – in which a series of concentric annular sections is used to generate the ultra-short focal length needed.
They found their lens LED glowed brightly up to a metre away from the radio source in free space, but needed to be 2 centimetres away when the lens was placed in a rabbit’s eye and the wireless reception was affected by body fluids. All the 40-minute-long tests on live rabbits were performed under general anaesthetic and showed that the display worked well – and fluorescence tests showed no damage or abrasions to the rabbit’s eyes after the lenses were removed.
A key challenge of the research was testing whether they could project an image onto the lens in such a way that the eye could see it. Because the human eye normally is unable to focus on anything closer than 15 centimeters, Parviz and his team compensated for the problem by incorporating a miniature Fresnel lens into their contact lenses. Fresnel lenses—originally designed for lighthouses—are flat and thin, and allow for a large aperture and a short focal length. “If an image is placed on a Fresnel contact lens, I can force the light rays to converge on the retina, making the light source more in focus,” Parviz says. “In a sense the lens tricks the eye into thinking that the image is farther away so it can focus on it.”