Monthly Archives: January 2011

What does the discoverer of room-temperature superconductivity look like?

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The science-fiction TV show Primeval has recently started its fourth season. Set (for the most part) in modern Britain, the show is based on the possibility that dinosaurs, humans, and other animals can travel back and forth through anomalies in the fabric of spacetime.

The show’s computer-generated imagery is highly accomplished and ensures that the dinosaurs look real and scary. Most of the show’s drama, however, revolves around how the few humans who know about the anomalies react to the reality of time-traveling dinosaurs and the possibility of traveling into Earth’s future.

Time travel is hard for physicists to stomach. In Albert Einstein’s special theory of relativity, which has passed all experimental tests, time can slow down, objects can become heavier and shorter, but a cause must always precede its effect.

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Of course, without time travel there’d be no Primeval—no Kaprosuchus preying on homeless people living by the Thames, no dodos running around the Home Office, no Pteranodons swooping on golfers. As if to restore physics verisimilitude to the show, the fourth season features a new main character, Philip Burton, who is, and looks like, a physicist.

Burton is a billionaire industrialist, who made his money after discovering room-temperature superconductivity. He’s played by Alexander Siddig (shown here), whose previous roles included Julian Bashir on Star Trek: Deep Space Nine.

At 45, Siddig-as-Burton is about the right age to have made such a momentous discovery. Heike Kamerling Onnes discovered superconductivity in 1911 at the age of 58. When they discovered high-temperature superconductivity in 1986, Georg Bednorz was 36 and Alex Müller was 59. The newest class of superconductors, the iron pnictides, was discovered in 2008 by Hideo Hosono, who was 55 at the time.

Siddig-as-Burton also resembles some successful physicists in his self-confidence (or arrogance, if you prefer) and his appearance. He wears a jacket, but no tie, and sports a short, stubbly beard.

Siddig himself is of mixed parentage. He was born in Sudan to an English mother and a Sudanese father. In the past he has played a Pakistani terrorist, an Emirates oil minister, and a Persian poet.

I don’t know whether Siddig’s ethnicity was a factor in his casting in Primeval but I like to think the show’s producers believe, as I do, that the person who discovers room-temperature superconductivity for real could come from the Middle East.

Charles Day

Miniaturized adaptive optics at SPIE Photonics West

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For some products, even fairly new ones, you can predict whether the latest versions will be bigger or smaller than their predecessors. Disk and flash drives are getting smaller (or staying the same size while storing more data), TV screens are getting wider, and laptops are getting slimmer.

But if you’d asked me before today to predict the size trend of adaptive optics systems, I wouldn’t have said they’re shrinking.

A perfect parabolic mirror will bring an object into perfect, diffraction-limited focus, provided the wavefronts radiating from the object are parallel and flat. Starlight arriving at a ground-based telescope doesn’t have parallel, flat wavefronts. Fluctuating, uneven refraction caused by atmospheric turbulence bends the wavefronts out of shape. The focus is imperfect.

In 1953 Horace Babcock of the Mount Wilson and Palomar Observatories in California proposed a way—adaptive optics—to compensate for atmospheric blurring. If you could measure the distortions as they happen, and if you could deform the telescope mirror quickly and arbitrarily, you could restore the wavefronts to their flat, parallel state.

Babcock’s idea was ahead of its time. Earth’s atmosphere fluctuates on a time scale of 10 to 100 milliseconds. Measurement and control systems from the 1950s through the 1980s couldn’t keep up. But since the early 1990s, adaptive optics systems have been installed at several observatories, including the two Keck telescopes on Mauna Kea in Hawaii and the Very Large Telescope (VLT) on Cerro Paranal in Chile. The three huge telescopes under development now—the European Extremely Large Telescope (E-ELT), the Thirty Meter Telescope, and the Giant Magellan Telescope—would not be worth building without adaptive optics.

The E-ELT’s primary mirror is 42 meters wide. That’s five times bigger than the primaries in each of the four VLT telescopes. Because I had just read a news story in Nature about the E-ELT, the association of adaptive optics with mirrors the size of swimming pools was freshly established in my mind.

Michael Helmbrecht’s talk at SPIE Photonics West soon wiped out my mistaken prejudice. Helmbrecht is the CEO and owner of Iris AO Inc, a company based in Berkeley, California, that makes miniaturized adaptive optics systems.

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The photo shows Iris AO’s PTT111-X deformable mirror. The product fact sheet lists its impressive features, among them its aperture: 3.5 mm. One hundred eleven tiny MEMS (microelectromechanical systems) actuators deform the mirror’s 37 segments.

NASA and the Pentagon are Iris AO’s current customers. After the talk, I asked Helmbrecht what the first commercial applications for his products would be. High-end microscopes for biology was one area. Lasers for semiconductor fab plants was another. As for retinal imaging, an area where bulkier adaptive optics systems are already in use, he said the price of his devices would first have to drop significantly.

Disk and flash drives, big-screen TVs, and laptops have all gotten cheaper. I expect MEMS-based deformable mirrors will, too.

Charles Day

Thuringians at SPIE Photonics West

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If you asked me to name the optics capital of the world, I’d pick Jena, Germany. Since 1846, the city has been the home of the venerable optical equipment manufacturer Carl Zeiss AG. Its sister company Schott AG is also based in Jena. Both companies, which are part of the Carl Zeiss Group, continue to thrive.

I doubt I’m the only person here at SPIE Photonics West who’d also choose Jena. Given the city’s fame, I was surprised, therefore, to receive an invitation to a cocktail reception and buffet hosted during Photonics West by the State Development Corporation of Thuringia, the state where Jena is located. The reception’s goal was to tout Thuringia as a place to do business, optics business.

Despite Thuringia’s prominence in optics—Jenoptik AG and the Fraunhofer Institute for Applied Optics and Precision Engineering are also in Jena—the state, whose coat of arms is shown below, needs more companies to move there.

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Like other parts of the former East Germany, Thuringia is trying to catch up economically with Germany’s rich Western states. At $25 000, its gross state product per capita is $10 000 lower than the German average and a daunting $36 000 lower than that of Hamburg, Germany’s richest state.

Thuringia is evidently succeeding in attracting companies. One of the speakers at the reception was Michael Foley, the CEO of Reflexite Corp. Based in Avon, Connecticut, Reflexite makes a wide range of reflective materials, including microstructured optics components for the solar power industry. Its German headquarters are in the Thuringian town of Apolda, 20 km from Jena.

I didn’t stay to hear Foley speak, so I’m not sure if he told his fellow guests why his company chose Thuringia. I wouldn’t be surprised if he cited the long tradition of optics in the region or the central location (Erfurt, the state capital, is the closest city to Germany’s geographical center). Maybe Thuringia offers tax breaks.

But whatever the reasons, I was impressed by the effort Thuringia is making to ensure it retains its preeminence in optics. In today’s global economy, no region—even one with a long history of industrial innovation—can afford to be complacent.

Charles Day

Monitoring cancer therapies at SPIE Photonics West

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When pharmacologists develop anticancer drugs, they need a way of seeing whether the drugs really do shrink and kill tumors. Magnetic resonance imaging can do the job without harming human patients or lab animals, but it’s expensive, especially if you need high spatial resolution. Biopsies are cheaper, but they risk interfering with the growth—or, one hopes, the shrinkage—of the tumors under investigation.

Yesterday at SPIE Photonics West, I learned about an optical method for tracking tumors: diffusive optical tomography. In DOT beams of near-IR light are sent through tissue at various angles and detected when they emerge, much depleted by both absorption and scattering. Wavelengths are chosen to reveal differences in concentration of various molecules, including hemoglobin.

Forming a three-dimensional image from those diffuse signals is doubly challenging. First, detecting the signals requires a sensitive instrument. You can’t arbitrarily increase the incident intensity to boost the output signal lest tissue be damaged. Second, untangling the paths taken by the light as it makes its way through a scattering medium is a formidable mathematical problem. Those and other challenges have been met. Diffuse optical tomography is now a cheap, fast, and effective imaging modality for use in the lab and the hospital.

In one talk I heard yesterday, Molly Flexman of Columbia University in New York City described how her group is using DOT to monitor the efficacy of bevacizumab, a drug designed to kill tumors by cutting off their ability to grow blood vessels and therefore their ability to obtain nutrients.

Bevacizumab is controversial. Marketed by its maker Genentech under the name Avastin, the drug appears to shrink some tumors, but not others. That known, variable performance suits Flexman because it gives her the opportunity to test whether DOT can indeed monitor the efficacy of any anticancer drug. Moreover, whether or not the drug targets a tumor’s blood vessels, DOT can readily detect them thanks to its sensitivity to hemoglobin.

Flexman and her colleagues looked at two types of cancer: Ewing’s sarcoma, for which bevacizumab has some beneficial effect, and neuroblastoma, for which bevacizumab is less effective. It turned out that DOT could reveal the difference in how the two cancers responded to the drug.

For her study, Flexman used lab mice. In the introduction to her talk, she explained why she and her colleagues chose to focus on Ewing’s sarcoma and neuroblastoma. Both cancers afflict children. Because children are still growing, therapies that attack cells’ ability to divide, such as ionizing radiation, have worse side effects for children than for adults.

Charles Day

Practical holography at SPIE Photonics West

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I’m in San Francisco this week for SPIE Photonics West, “the world’s leading photonics, laser, and biomedical optics event,” according to the conference slogan. The conference is huge. In fact, it consists of five separate but contemporaneous conferences: BiOS (1771 research papers), LASE (662), MOEMS-MEMS (202), OPTO (1320), and Green Photonics (270).

Faced with such a cornucopia, I chose to spend my first morning attending an OPTO session entitled “Scientific Holography, Applications and Experimental Techniques I.” Here, I thought, was a session that represents what Photonics West is all about: an interesting and important application of light.

My favorite talk of the morning was by Tokyo University’s Naoya Tate. He and his colleagues are using nanotechnology to embed information on the nanoscale within information on the macroscale.

That goal is hard to reach if, as is the case with Tate’s scheme, the information is to be retrieved optically. “Nanoscale” is a somewhat loose term, but it usually refers to features that are 1 to 100 nm long. Visible light, which ranges in wavelength from 380 nm (violet) to 750 nm (red), can’t ordinarily resolve subwavelength features.

However, if you bring your probe into the near-field region—that is, within one wavelength of an object’s surface—you can resolve subwavelength features. In Tate’s scheme, which he calls a nanophotonic hierarchical hologram, the subwavelength features belong to a nanoscale metallic grid-like structure embedded within a sandwich of holographic gratings.

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When illuminated from a macroscopic distance, the gratings project a hologram of a three-dimensional, macroscale object. When illuminated and viewed from a nanoscale distance, the nanoscale grid reveals the information encoded in its structure.

Security is one possible application. The nanoscale grid could serve as a covert watermark on a hologram. Besides a near-field microscope, no special equipment would be needed to check it.

In his talk, Tate noted that the idea of embedding information on short length scales in a larger image has been used before. Last year, scientists examining the Mona Lisa discovered that Leonardo da Vinci had written tiny letters on Lisa del Giocondo’s pupils.

Charles Day

Climate change, insurance companies, and criminals

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Swiss Re is the world’s second largest company in the reinsurance business, the business of insuring insurance companies. In 1990, when the first report from the Intergovernmental Panel on Climate Change came out, Swiss Re decided that sea-level rise, desertification, and other risks of climate change are real. If the company failed to take them into account, it risked losing money.

Now, Swiss Re is in the vanguard of companies and organizations that are raising the alarm about climate change. Last year, it released a detailed scientific rebuttal of the arguments climate skeptics make against anthropogenic warming.

Swiss Re’s pragmatic position popped into my mind last week when I read a BBC news story about a scam. Swindlers are inviting climate scientists to attend fake conferences in London. To fool the scientists, swindlers created a conference website and pretended the meeting would take place in a real hotel, the Crowne Plaza on Buckingham Gate (shown here). To entice the scientists, the swindlers offered to cover all travel expenses—provided the scientists paid an upfront reservation fee.

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The title of the BBC story was “Climate Scientists Targeted for Fraud.” When I spotted it on the BBC homepage, my first thought was that rogue climate-change deniers were creating mischief. It came as an odd relief to learn that the swindlers’ motives were purely and grubbily criminal.

It’s also oddly reassuring that for two classes of professional, insurers and criminals, climate change is a matter not of contentious politics or disputed science, but of cold cash. In this second decade of the 21st century, the cost of mitigating climate change seems to many people more real than the cost of doing nothing. But as the mean global temperature inexorably rises, doing nothing will clearly become more costly.

Charles Day

Did the White House snub Chinese American scientists?

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Yesterday, President Obama held a state dinner for China’s president Hu Jintao. As is usual on such occasions, my local paper, the Washington Post, published the guest list.

The list had the usual Washington mix of politicians and journalists, along with business leaders. It also included several distinguished Chinese Americans (or Chinese who live in America). Figure skater Michelle Kwan, cellist Yo-Yo Ma, pianist Lang Lang, architect Maya Lin, and actor Jackie Chan were among the 255 guests, who dined on pear salad, poached lobster, rib-eye steak, and apple pie.

Chinese American scientists, however, were conspicuously absent. Granted, physicist Steven Chu and medical researcher Patrick Soon-Shiong were there, but Chu is also the US Energy secretary and Soon-Shiong is also a billionaire businessman.

By my count, seven Chinese Americans have won Nobel Prizes in science. All of them are alive, and at least two of them, C. N. Yang and T. D. Lee, have dedicated much of their lives to improving China’s science enterprise and to strengthening scientific ties between China and the US.

Now it’s possible that Chinese American Nobel laureates were invited, but for one reason or another could not, or chose not to, attend. It’s also possible that the White House did not invite the laureates to avoid offending President Hu. Nobel Prizes are a sensitive issue in China. The country’s first unhyphenated Nobel laureate, the writer Gao Xingjian, lives in political exile in Paris. Its second unhyphenated laureate, the human rights activist Liu Xiaobo, is imprisoned in northeast China.

Refraining from offending one’s guests is polite. Still, the contribution of Chinese students, postdocs, and researchers to science in the US is so great that the White House should have found a way to reflect it in the guest list.

Charles Day

Special relativity, car batteries, and the pursuit of problems

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Despite subscribing to the Economist for 25 years, I’ve yet to become a regular reader of the newspaper’s Science and Technology department. Because my job entails keeping up to date with scientific developments, the science covered in the Economist is often already familiar. Other stories—a smaller number—describe long-shot ideas that would overthrow current thinking, provided they’re true.

But the lead story in the current issue was neither familiar nor about long-shot science. In “A Spark of Genius,” the Economist‘s anonymous reporter described a paper entitled “Relativity and the Lead-Acid Battery” that had recently appeared in Physical Review Letters.

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I encourage you to read the story, which is a tour de force of science writing. Here’s a brief summary.

The University of Helsinki’s Pekka Pyykkö and his colleagues asked themselves a question that you’d think had been answered before: Why are lead–acid batteries—the type that have been used in cars for more than a century—so effective?

The science behind a lead–acid battery is outwardly simple. Each of the battery’s six cells consists of two electrodes dipped in a solution of 35% sulfuric acid and 65% water. The anode is made of lead(IV) oxide; the cathode is made of lead. Immersion in sulfuric acid causes the Pb cathode to shed electrons, which readily accumulate on the PbO2 anode, creating the all-important potential difference—about 2 V per cell.

Lead belongs to the periodic table’s carbon family, as does tin, which lies just above it. Given the two elements’ similar chemistry, a tin–acid battery ought to work nearly as well as, or even slightly better than, a lead–acid battery, but it doesn’t.

Pyykkö suspected that special relativity might account for lead’s better battery performance. As one gets deeper into the periodic table, the positive charge on an atom’s nucleus becomes bigger. Consequently, the outermost electrons, the ones that participate in chemistry, feel a stronger force—so strong, in the case of lead, that the electrons whizz around the nucleus at 0.6 the speed of light, c.

According to special relativity, a particle traveling with speed v behaves like a particle that’s more massive by a factor, γ, given by

γ = (1 − v2/c2)−1/2.

The effect of relativity on a lead–acid battery’s electrode materials is opposite but not equal. In lead, the increase in effective mass causes the outer electrons to sink closer to the nucleus. In lead oxide, it deepens the empty potentials into which free electrons can fall. Lead becomes a worse cathode, but lead oxide becomes an even better anode. For tin, γ is a nonnegligible 1.07, but for lead, γ is a chemistry-changing, battery-boosting 1.25.

That relativity influences atomic properties wasn’t new to me. The exotic superconductivity of so-called heavy fermion systems arise from partially filled d and f orbitals. Spin–orbit coupling, the interaction between an electron’s spin and orbital angular momentum, underlies the spin Hall effect and other phenomena. The coupling increases with atomic weight.

In hindsight, Pyykkö’s evocation of special relativity doesn’t seem, well, special. What is remarkable, at least to me, is his choice of problem. In high school and university, we learn how to solve problems that already have worked-out answers. Being a scientist entails identifying new problems, which is sometimes harder than solving them.

Charles Day

Does the world need the US to lead particle physics?

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Last Monday, the US Department of Energy announced that it would not pay the additional cost of three more years of Higgs hunting at Fermilab’s Tevatron collider. The extension, which was recommended by a panel of eminent physicists, would have given Fermilab a chance to scoop the Large Hadron Collider while the bigger machine spends 2012 off line and under repair.

Despite the glory that would redound to Fermilab if it found the Higgs, the merits of the proposed extension are not beyond doubt or challenge. As Adrian Cho put it in a news story that ran in Science last September.

Scientists at the last remaining U.S. particle physics lab have a shot at a major discovery. But pursuing that prize means delaying other projects that could enhance the lab’s long-term viability. Should they still go for the glory?

Those other projects form part of a broad strategy to direct Fermilab away from experiments at the energy frontier, where the Higgs presumably lives, and toward the intensity frontier, where rare phenomena are brought into view and studied. Prolonging Fermilab’s Higgs hunt would divert the lab’s resources—including particles accelerated by the Tevatron—from the NOνA neutrino experiment and others.

Not being a particle physicist, I can’t offer an expert opinion on the canceled extension. But as a naturalized American, I can complain about one of the justifications that some physicists in the US make to keep the Tevatron in the Higgs hunt: that the US must maintain leadership in particle physics.

As the energy frontier has advanced, so too has the cost of building accelerators and detectors. A next-generation machine capable of elucidating Higgs properties is beyond the budget of any single country. Particle physics has become international. As if to acknowledge the new reality, one possible next-generation machine, the International Linear Collider, even has “international” in its name.

If particle physics is inevitably international, why do US physicists fret publicly about losing leadership? Does particle physics even need a single country to lead it?

The answer to the second question is “no.” Answers to the first question could range from the not discreditable “out of national pride” to the cynical “to appeal to our Congressional paymasters.” Neither strikes me as compelling because neither evokes the reason for building the Tevatron in the first place: to further humanity’s understanding of matter’s ultimate constituents.

Charles Day

To save the planet should scientists refrain from traveling?

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Today’s issue of Science includes the results of an online poll that the magazine conducted last December. The poll was prompted by a letter to Science from the University of Wyoming’s Ingrid Burke.

Burke’s letter urged readers to consider the environmental consequences of their travel. The poll asked readers: Would you participate in an annual meeting remotely (via video teleconferencing or other technology)? Respondents were given four answers to choose from:

  1. Yes: Participating remotely would be about as valuable as attending in person.
  2. Yes: It would lose some value, but the trade-off would be acceptable given the environmental benefits.
  3. No: It would lose some value, and the trade-off would be unacceptable despite the environmental benefits.
  4. No: Participating remotely would be about as valuable as not attending at all.

The results revealed rough parity between the combined yeses (52%) and the combined nos (48%). The most popular answer by far was 2. Forty-four percent of respondents would forego the full experience of attending a conference in person to reduce their emission of greenhouse gases.

Later this month I’ll fly to San Francisco to attend Photonics West. In March I’ll fly to Dallas to attend the American Physical Society’s March meeting. My mission at both conferences is to meet people and learn about what they’re working on. Attending virtually isn’t a good option. Still, not wanting to deprive polar bears of their habitat, submerge the Maldives, or turn Spain into a desert, I tried to find out how much carbon dioxide my trips would generate per capita.

The answers I got from the Nature Conservancy’s carbon footprint calculator were equivocal. My share of the CO2 emitted by a jetliner on a “long” return flight is 2.2 tons. For a “short” flight, it’s 0.4 tons. But my gasoline-sipping 18-year-old Honda Civic emits about 6 tons of CO2 per year. In my case, giving up attending a few meetings each year wouldn’t reduce my personal carbon footprint dramatically.

One of the respondents to the Science poll, John Burke Burnett, left this comment on the poll’s website:

Until we come up with holographic teleconferencing with the ability to eat virtual lunch together in smaller groups, there will always be a need for large gatherings from time to time.

There might be a hint of sarcasm in Burnett’s comment, but I prefer to recast it as a challenge to software and hardware engineers: Create a virtual conference on a Star Trek Holodeck, and I’ll stay at home.

Charles Day