The Dayside

A new x-ray light source for a new university

2012-02-02T15:35:29Z

The financial crisis of 2008 and the continuing debt crisis in the eurozone have stifled growth in the US, Western Europe, and elsewhere. If asked to predict when robust growth will return, some economists cite the sorry case of Japan, whose economy, the world's third largest, has been stagnant for the past two decades—the Lost Years (失われた20年) in Japanese. If a country doesn't implement the right policies, the economists warn, it risks languishing in the doldrums as Japan has.

But despite its stagnant economy, Japan's physics enterprise remains vibrant—and ambitious, as exemplified by Kamiokande, the nucleon decay experiment at Kamioka, a village in Gifu Prefecture.

Completed in 1983, he first Kamiokande experiment consisted of 3000 tons of water contained in a 16-meter-high tank whose inner surface was lined with 1000 photomultiplier tubes. The goal of the experiment was to watch for flashes of Cherenkov radiation that manifest rare, hypothesized proton decays.

In 1985 Kamiokande was upgraded to characterize the flux of neutrinos that stream from the Sun. Kamiokande II did just that. It also detected 11 neutrinos from Supernova 1987A. Those precious neutrinos reached Earth three hours before the supernova's first visible photons did. The difference in arrival time suggested that neutrinos have mass.

Super Kamiokande, which began taking data in 1996, is a new and bigger version of Kaniokande II. Its 41-meter-high tank contains 50 000 tons of water and 11 000 photomultiplier tubes. By 2002, Super KamiokaNDE had seen enough neutrinos to prove that neutrinos oscillate between different mass states.

Detecting proton decay, the goal of the original Kamiokande and a goal of Super Kamiokande, remains beyond the abilities of current experiments. Undeterred—and inspired by that challenge—physicists in Japan are planning Hyper KamiokaNDE, which will be 10 times bigger than its Super predecessor. The ambitiously huge leap forward in size is reflected by a Japanese pun: When spoken, "kamiokande" can be understood to mean 神を噛んで (bite into God).

Looking outward

As the Lost Years continued, some Japanese people began to turn inward and become less interested in the rest of the world. That insularity is not shared by Japan's science establishment. To prosper scientifically, Japan needs to attract foreign students, postdocs, and professors. At 8.2 births per 1000 people, the country's birthrate is the world's second lowest after Germany's 8.1. What's more, as America's swelling roster of Nobel-winning immigrants demonstrates, foreign researchers enrich domestic science.

In 2007 the Japanese government launched the World Premier International Research Center Initiative. Its goal, as declared on its website, is to build

“globally visible” research centers that boast a very high research standard and outstanding research environment, sufficiently attractive to prompt frontline researchers from around the world to want to work in them. These centers are given a high degree of autonomy, allowing them to virtually revolutionize conventional modes of research operation and administration in Japan.

The qualities of ambition and looking outward are both represented in Japan's newest university, the Okinawa Institute of Science and Technology, which is shown here. Research at OIST is inherently interdisciplinary and is focused on five areas: neuroscience, molecular sciences, environmental sciences, ecological sciences, and physical sciences.

But what makes OIST special, besides its newness, is the international makeup of its faculty and students. More than half of the OIST community comes from outside Japan. Instruction is in English, not Japanese. Only 20 students—all working toward PhDs—are accepted each year. The student-to-faculty ratio is 2:1.

OIST's stated aim is to "recruit the best students in the world to work in an environment that encourages creativity, uniqueness, and diversity." To help meet that ambitious goal, OIST has just announced that it intends to buy a compact, laboratory-sized x-ray light source (XLS).

Appropriately for an internationally minded institution, OIST has issued a call for expression of interest to vendors worldwide. If you know of any XLS manufacturers, please send them the link. The deadline is 23 February.

A compact hyperspectral camera at Photonics West

2012-01-26T17:15:06Z

As you might expect from its name, a hyperspectral camera does more than reproduce the appearance of objects. The name connotes spectroscopy: For each of its pixels, a hyperspectral camera yields a continuous spectrum over the same, wide waveband.

Given that molecules' distinctive fingerprints lie in the IR, hyperspectral imaging is especially useful when the camera's waveband encompasses both the IR and the visible. Indeed, IR-to-visible hyperspectral imagers have found a host of applications, including remote sensing of vegetation, prospecting for oil, and surveillance of criminal suspects.

Most hyperspectral cameras owe their spectroscopic ability to a diffraction grating, which spreads the light from a narrow slit-shaped aperture over a sensor. If the slit is oriented in, say, the x direction, then sweeping the aperture over a scene by means of a movable mirror builds the image in the y direction.

The narrow slit and long focal length yield fine spectral and spatial resolution, but at the expense of throughput (because the aperture is small), camera size (because of multiple optical components), and mechanical complexity (because the optics move). In 2009 Andy Lambrechts and his colleagues at IMEC in Leuven, Belgium, set out to design a cheaper, more compact camera. Last week at SPIE Photonics West, the camera was publicly unveiled for the first time.

Chips and filters

Besides its standard optics, the IMEC camera (shown here) consists of two main components, a CMOS sensor and a Fabry–Pérot or dichroic filter. The camera's CMOS sensor is the commercially available 2048 × 2048-pixel CMV4000 made by CMOSIS of Antwerp, Belgium. It operates in the same way as other CMOS sensors: Each of its silicon-based pixels converts photon energy into electronic charge, which is then read out by the pixel's transistor-based electronics.

The Fabry–Pérot filter was developed by Lambrechts's team and is what makes the IMEC hyperspectral camera special. In cross section the filter resembles a staircase of tiny steps. Interference between the top surface of each step and the bottom surface of the staircase ensures that the step transmits only one spectral band to the sensor below.

The camera unveiled at Photonics West has 100 spectral bands that range from 560 nm (green) to 1000 nm (near-IR), but different and wider wavebands are possible. The upper limit of a CMOS sensor's waveband is limited to 1125 nm, which is the size of silicon's bandgap. The lower limit depends on the choice of material and how it is modified. Lambrechts' team is currently working on a new sensor that reaches 400 nm (violet).

The filter, which is made as a wafer, is fixed directly above the CMOS sensor to create a compact hyperspectral sensor that has no moving parts and which makes simultaneous use of all the light that falls on it. The spectral resolution of the IMEC camera is lower than that of a standard hyperspectral camera, but, thanks to its wide aperture, it has the offsetting advantage of high throughput and therefore fast operation.

At the IMEC booth in the Photonics West exhibition hall, Lambrechts's colleague Bart Masschelein demonstrated the camera. He had it scan, in less than a second, over a collection of green objects: real leaves, life-like tissue leaves, and pieces of plastic. Masschelein's computer interface quickly displayed the images and their corresponding spectra, which clearly distinguished the different materials. Masschelein's software could also classify the objects based on their spectra—that is, knowing what the spectrum of a real leaf looks like, it could find the real leaves among the other objects.

Lambrechts hopes that the IMEC camera, being cheaper and more compact than standard hyperspectral imagers, will find applications beyond the traditional uses. But IMEC is a research center, not a manufacturer. If its cameras are put to work, say, inspecting vegetables on a conveyor belt or watching for poison gas on a battlefield, they will be built by IMEC's industrial partners.

Infrared neural stimulation at Photonics West

2012-01-24T00:42:04Z

In 2005 Vanderbilt University's Anita Mahadevan-Jansen and her colleagues made a remarkable discovery: Pulsed IR light triggers a tightly localized response in mammalian peripheral nerves. What's more, the pulse energy needed is far below the threshold for damaging tissue.

Mahadevan-Jansen's team had found, to quote from the abstract of the discovery paper in Optics Letters, "a simple yet novel approach to contact-free in vivo neural activation that has major implications for clinical neurosurgery, basic neurophysiology, and neuroscience." Followup research supports that optimism. Infrared neural stimulation (INS) evokes responses not just in nerves that control a mammal's limbs, as was the case in the original paper, but also auditory and cardiac nerves.

The mechanism behind INS is thermal. In a series of experiments published five years ago in the Biophysical Journal, the Vanderbilt team and their collaborators from the University of Texas at Austin, investigated effects that could plausibly underline INS, including photochemistry, pressure, and electromagnetism. Their conclusion: The moderate, transient tissue heating engendered by the IR pulse activates transmembrane ion channels and begets action potentials—that is, triggers the nerves to fire.

Unlike electrical stimulation, which requires electrodes to be inserted to tissue, INS can be delivered without contact. Given the compact size of solid-state light sources, INS-based cochlear implants, pace makers, and other medical devices are conceivable—at least in principle.

From PNS to CNS

At this year's SPIE Photonics West, one of Mahadevan-Jansen's Vanderbilt colleagues, Anna Wang Roe, reported on her team's efforts to advance INS beyond the peripheral nervous system and into the central nervous system. The goal is challenging. As Roe notes in a recent paper, peripheral neurons tend to be organized in parallel bundles like wires and cables in utility pipes. In contrast, nerves in the brain are organized in complex hierarchical three-dimensional architectures. What's more, cerebral neurons interact with astrocytes and other brain cells that may affect the neurons' response to INS.

The focus of Roe's talk was on her team's use of both functional magnetic resonance imaging (fMRI) and optical imaging to map the cerebral cortex of macaque and squirrel monkeys. The cerebral cortex, which forms the outer part of the mammalian brain, is important for several high-level functions including attention, memory, and language. Research has shown that specific functions are controlled by clusters of nerves that occupy distinct domains about 200 μm across.

The fMRI scans can pinpoint which regions of the brain become active in response to a stimulus, such as a blinking light, a burst of noise, or even—in the case of human subjects—a verbal suggestion. The technique works because brain cells, when called into action, require energy, which they obtain, in part, from a sudden inrush of oxygenated blood. Oxygenated hemoglobin, being less magnetic than deoxygenated hemoglobin, shows up in fMRI. Roe's lab is one of the few in he world that has an MRI scanner (shown here) whose bore is of a suitable size and orientation for monkey studies.

Oxygenated hemoglobin is also redder and brighter than deoxygenated hemoglobin. The sudden inrush of blood to a region of the brain is also visible—literally—if the region under investigation is exposed and close to the surface. The difference in red brightness is not difficult to detect. Roe's lab uses a red laser and a commercial CCD camera.

It's more difficult to expose an area of the monkey's cerebral cortex to visualize those changes in oxygenation. To meet that goal, Roe and her collaborators surgically implanted an optical window in the monkey's skull, a procedure involving replacement of a section of the skull and native dura (the protective membrane surrounding the brain) with a circular chamber and a biocompatible transparent, artificial dura. Besides providing a way to view the cerebral cortex, the window also allows an INS signal to be delivered.

At this stage of their research, Roe and her team have succeeded in associating some brain functions, like attention, with cortical domains. They have observed the telltale reddening of the domains when the monkeys are called on to perform a task. And they have confirmed, as her colleague Mahadevan-Jansen has done for the peripheral nervous system, that INS does not cause visible, lasting damage to tissue.

What remains to be demonstrated is whether INS can potentially be used to achieve therapeutic effects in the central nervous system. Enhancing or restoring lost function is one possibility. At the end of her talk, Roe speculated that some symptoms of autism and attention deficit hyperactivity disorder might one day be treatable with INS.

Microtomography for microfluidics at Photonics West

2012-01-22T21:42:31Z

Microfluidics is a technique for controlling, processing, and analyzing small volumes of liquid in submillimeter devices. The small scale befits biology especially. Not only are cells and microorganisms themselves small, but they are often available only in small, precious quantities.

Monitoring a microfluidic device is usually done through an optical microscope, which is typically a hundred times as big as the device itself. What's more, because conventional microscopes rely on lenses, high spatial resolution is obtained at the expense of a small field of view. Paradoxically, big microscopes yield small images.

At this year's SPIE Photonics West, graduate student Serhan Isikman from Aydogan Ozcan's biophotonics lab at UCLA described a lensless tomographic imaging system whose 4- by 6-mm CMOS sensor array is not much bigger than a typical microfluidic device. Like a hospital CT scanner, the UCLA imager takes multiple two-dimensional images from which 3D images are reconstructed. Isikman and Ozcan call the technology optofluidic tomography.

The figure shows the basic principle. Each 2D image consists of a so-called in-line hologram. Spherical wavefronts emanate from a coherent light source and either pass right through the objects in the microfluidic device or are scattered and absorbed by them. What the CMOS sensor records is the interference pattern formed by the unaffected and affected wavefronts. The 2D image is reconstructed directly from the hologram (that is, the interference pattern) without the need to send a second reconstruction beam through the hologram, as is the case in standard "off-line" holography.

The 2D images are created in quick succession by a bank of LEDs arranged in a circular arc above the microfluidic device. A second round of reconstruction, called filtered back projection, is used to create a 3D image from the 2D images.

Because the UCLA system lacks magnification, its spatial resolution is ordinarily limited by the pixel size of the sensor, 2.2 μm. But finer resolution can be obtained thanks to a technique called pixel superresolution (PSR). Assuming that an object doesn't change size or shape as it passes over a patch of pixels, you can use the signals recorded in the pixels to interpolate the object's shape. If the object is stationary, rocking the light sources with electromagnetic actuation enables PSR to be applied.

Using PSR, Isikman, Ozcan, and their colleagues have obtained a resolution of less than 1 μm. That's comparable to the resolution of an optical microscope, but it's achieved over a bigger field of view (about 100 times as wide as an optical microscope at ×40 magnification). Despite its significantly enlarged field of view, the lensless tomographic microscope can fit in a small volume of 96 × 89 × 40 mm, and weighs only about 110 grams.

In his talk, Isikman reported results of imaging two microorganisms, the nematode worm and model invertebrate Caenorhabditis elegans and the eggs of the dwarf tapeworm Hymenolepis nana.

The lensfree tomography and computational microscopy work of Ozcan's bio-photonics lab has yielded several patent applications over the last few years. They're licensed by Holomic LLC, a startup based in Los Angeles.

"Let's say yes to nuclear and no to Dr. No's nonsense"

2012-01-21T23:11:23Z

My title comes from the last line of a recent press release issued by Britain's Royal Society of Chemistry. The RSC noted that filming began on the first James Bond movie, Dr. No, 50 years ago. In the movie Bond kills the eponymous villain by forcing him into the cooling tank of a nuclear reactor. That scene and the movie's anniversary prompted the press release, which speculated on the negative impact of Bond on the public's perception of nuclear power.

Blaming Bond is a tough sell. Even taking into account the artistic license that moviemakers grant themselves to put entertainment above accuracy, Dr. No doesn't exaggerate the perils of nuclear power, nor does it downplay nuclear power's benefits.

Dr. No plans to disrupt Project Mercury, NASA's first manned space program, by disrupting the navigation system of its rocket launchers. To do so from his lair on the Caribbean island of Crab Key, he needs a powerful radio transmitter. Nuclear power—movie watchers are left to presume—gives him a means of generating electricity that doesn't require large, attention-attracting shipments of fossil fuel.

When Bond and his companion Honey Rider are captured and brought to Dr. No's lair (shown here), they are scrupulously checked for radiation and scrubbed until a henchman wielding a Geiger counter declares them clean.

Granted, Dr. No's nuclear reactor and its cooling tank are implausibly accessible. Nevertheless, to sabotage the reactor and prevent the transmitter from fatally diverting the Mercury mission, Bond had to disguise himself as a powerplant worker. Then, facing determined, physical opposition, he had to seize the reactor's controls.

Nuclear weapons, but not nuclear reactors, appear as plot elements in five of the 21 Bond movies that followed Dr No. In Goldfinger (1964), the eponymous villain plans to detonate a Chinese nuclear device inside the US gold depository at Fort Knox, Kentucky. His goal is not necessarily to destroy the gold, but to contaminate it, thereby raising the value of his own gold holdings.

Thunderball (1965) hinges on the theft of an RAF bomber and its two nuclear bombs, one of which the villain, Emilio Largo, threatens to detonate in Miami unless he receives a massive ransom. In The Spy Who Loved Me (1977), the megalomaniacal shipping magnate Karl Stromberg hijacks three nuclear-armed submarines, one British, one Soviet, and one American. By targeting their missiles at New York and Moscow, he aims to provoke a nuclear war that will destroy the superpowers and leave him free to lead and establish a new underwater civilization. Octopussy (1983) also involves a stolen nuclear weapon, as does The World Is Not Enough (1999).

However fanciful the plots of the five nuclear-armed Bond movies are, the recurrence of stolen weapons as a plot element reflects a real and widespread fear. We might be able to convince ourselves—barely—that an established nuclear power won't use its weapons unless severely provoked. Nuclear-armed terrorists are far scarier because they want to attack, kill, and destroy their perceived opponents.

Nuclear power is also scary, as the disaster last March at Fukushima Daiichi demonstrated. Saying yes or no to nuclear power entails acknowledging and examining our fears, not ignoring them.

The creativity factor

2012-01-11T19:21:16Z

Last year two developmental psychologists from Cornell University, Stephen Ceci and Wendy Williams, published a paper in the Proceedings of the National Academy of Sciences entitled "Understanding current causes of women's underrepresentation in science." The paper caused a stir. Ceci and Williams attributed the low proportion of women in physics and other hard sciences to the choices made by girls and women.

My modest response to the paper was to question whether the choice to avoid the hard sciences is truly free. In their recently posted preprint, Theodore Hill and Erika Rogers looked more deeply into the question of choice. Referring to Ceci and Williams's work, they wrote:

Even if the “women’s preference” conclusion is accepted, the original question of “Why?” remains unanswered, and, perhaps more importantly, so does the question of what could or even should be done about it. Do the majority of women prefer not to go into the hard sciences because of their own limitations in either aptitude or attitude (i.e., they simply don’t have the talent, or they think they don’t have the talent), or because there’s something intrinsically unappealing to them about these fields? And what about the women who do go into these fields, and then leave? The issue of raising children simply does not account for the smaller influxes and larger exoduses observed in hard science careers over others. Is there some other important common factor that should be considered?

Unlike Ceci and Williams, Hill and Rogers are hard scientists. Hill is professor emeritus of mathematics at the Georgia Institute of Technology. Rogers is retired from California Polytechnic State University, where she was a professor of computer science. Perhaps because of their backgrounds, Hill and Rogers seized on a what they perceived to be a glaring limitation of previous studies of gender gaps:

The self-described “top researchers” in the gender gap in science seem to have completely ignored an important and compelling factor. In spite of acknowledging up front “the kind of intense, highly creative thinking required of mathematicians,” they have omitted the well-studied issue of gender differences in creativity. In ignoring the creativity factor, the science gender gap experts have greatly underestimated the potential importance of a completely different set of both biological and societal factors which may “conspire to limit talented women and girls”. Consequently, decision makers are thereby missing significant opportunities for constructive improvements.

Hill and Rogers note that experts in the field of gender differences in creativity often distinguish two facets of creativity: creative ability and creative productivity. Studies of the former facet are inconclusive: There is no strong evidence that men have more creativity ability than women. But Hill and Rogers found a broad consensus about creative productivity: With the exception of creative writing and acting, men outproduce women in architecture, music, science, and other creative fields.

Given that a successful mathematician or physicist must be both creative and productive, Hill and Rogers wondered if creativity could be a significant factor in explaining the dearth of women in the hard sciences. To answer that question, they reviewed studies of creative productivity with an eye out for possible gender differences. They found three possible factors:

Playfulness. Men more than women are willing to engage in playful, seemingly irrelevant activities that sometimes lead to innovative ideas. Hill and Rogers cited card- and Go-playing mathematicians at Bell Labs. I wrote two years ago about Andre Geim and Konstantin Novoselov's practice of routinely devoting 10% of their time to "crazy things that probably won’t pan out at all, but if they do, it would be really surprising." Geim and Novoselov's playfulness helped them win a Nobel Prize.
Curiosity. Studies have shown that on average men are significantly more curious than women. "Curiosity," according to one psychologist quoted by Hill and Rogers, "functions as an adaptive motivational process related to the pursuit of novelty or challenge" and could, Hill and Rogers speculate, help explain gender difference in creativity.
Risk taking. Hill and Rogers didn't cite any studies to support the claim that men take more risks and endure failure more readily than women. But it's a widely held view. To prove his and Robin Warren's ridiculed theory that Helicobacter pylori causes stomach ulcers, Barry Marshall drank a petri dish of the bacterium, which first gave him nausea and then, within eight days, gastritis. Antibiotics cured him.

Hill and Rogers take seriously—as any scientist should—the possibility that men could be innately more creative than women. But they also note that there are significant cultural and societal reasons for the gender gap in creativity. Society, unlike our genetic programming, can be changed.

Indeed, the most valuable contribution of Hill and Rogers's work, it seems to me, is to get us thinking about how to create environments where girls and women can develop their creativity and can indulge, as Hill and Rogers put it, in "'unladylike' playful behavior from getting dirty to tearing devices apart."

As an exemplar of that approach, they cite Stanford University's Hasso Plattner Institute of Design, known popularly as the d.school. According to the school's website, "Students and faculty in engineering, medicine, business, law, the humanities, sciences, and education find their way here to take on the world’s messy problems together." Besides nurturing creativity, Stanford's d.school also trains students to deal with failure.

Hill and Rogers conclude by urging that more resources be devoted to studying and nurturing creativity.

In the meantime, we feel that changes enhancing and encouraging a “culture of creative opportunity” for students and faculty could be implemented effectively and quickly within current academic environments, particularly those with a view to improving women’s representation in the hard sciences.

If Hill and Rogers are right and if we follow their advice, followup studies by Ceci and Williams will register a welcome rise in the number of girls and women choosing to pursue physics.

Putting the applied cart before the basic horse

2012-01-05T18:23:55Z

To some physicists, the traditional order of teaching science in high school—biology, then chemistry, then physics—is back to front. Making sense of living things is easier if you already know how their molecular building blocks behave and interact chemically. Making sense of chemical reactions is easier if you already know how electrons behave and interact physically.

This so-called Physics First approach hasn't caught on beyond a few pioneering pockets, perhaps because physics requires more math than chemistry does, and chemistry requires more math than biology does. What's more, by starting with biology, students progress from the familiar world of bees and birds toward the abstract world of F = ma and pV = nRT.

But regardless of the order in which they're taught, biology, chemistry, and physics are all basic sciences. With a good grounding in all three, a student can go on to study any of them more deeply or to study one or more of their applied offshoots. And because the core of scientific literacy lies in biology, chemistry, and physics, students who don't want to pursue science also benefit from learning the three basics.

Not having any children, I hadn't thought much about high school science. But I have five young nieces and three young godchildren. Two of them, Miriam and Sarah, will be 11 next month. Time, I thought, to pay attention to their scientific education.

Miriam will be attending Ysgol Eirias in Colwyn Bay, a town on the coast of North Wales. ("Ysgol" is Welsh for "school.") On page 14 of the school's prospectus, you'll find this brief description of the science faculty:

The Science Faculty is an energetic team of teachers specialised in Physics, Chemistry and Biology who endeavour to meet the needs of all students through the effective delivery of the Science curriculum.

Sarah is headed for Sherwood High School in Sandy Spring, Maryland. According to its website, the school is in the process of implementing an academy model. Sherwood's Academy of Science aims to provide students with

the knowledge and skills needed to not only compete, but excel and thrive in science and medicine in college. The Academy of Science also provides students with unique opportunities to interact with professionals in the areas of medicine, biotechnology and environmental science.

Sherwood's science academy sounds great—until you look at the courses it offers. They're organized in two "pathways," environmental science and health professions. Biology and chemistry appear in both, but physics is absent. Sarah could, however, study horticulture, if she chose the environmental science pathway, or medical careers science, if she chose the health professions pathway.

I commend Sherwood for putting together two coherent science courses that mix basic and applied sciences and which prepare students for employment. It's conceivable that some Sherwood students will be inspired to become scientists not by the challenge of understanding nature, as I was in my physics class, but by the challenge in their horticulture class of growing a more nutritious carrot.

On the other hand, the physicist in me recoils at the apparent absence of my favorite science. Physics is also absent from the two pathways in Sherwood's Academy Engineering and Technology: simulation and gaming, and engineering.

I'm also troubled by what strikes me as the premature and limited specialization implied by the two—and only two—science pathways. Students' interests change, as does the local job market. A curriculum focused on a handful of applied sciences, it seems to me, will offer fewer potential opportunities than one focused on basic sciences.

Let's not put the applied cart before the basic horse.

An old way to fund new physics

2011-12-21T13:37:29Z

When I saw the headline "Crisis Mounts at BlackBerry Maker" in last Friday's Wall Street Journal, my first reaction was, Oh no! What about the Perimeter Institute?

The Perimeter Institute for Theoretical Physics, to give the independent research center its full name, was founded in 1999 and is located in Waterloo, Ontario. Funds to establish the new institute came from Mike Lazaridis, who founded and runs Research in Motion. RIM's main product is the BlackBerry smartphone—hence my alarm at the WSJ headline.

But I wasn't sure that the reaction was justified. Seeking clarification, I emailed John Matlock, the institute's director of external relations and public affairs. Matlock promptly replied with the reassuring news that the Perimeter Institute has a mix of funding sources, including the provincial government of Ontario, which recently renewed investment of $50m, and the national government of Canada, which pledged the same amount. Last year the BMO Financial Group donated $4 million.

The Perimeter Institute's recent foundation, the source of its seed money in high-tech, and the architecture of its buildings give the impression of a 21st century enterprise. Its scholars conduct research in topics at the forefront of theoretical physics, including topological insulators, gravitational waves, and quantum information.

Despite the topics' manifest modernity, we should keep in mind that research in physics always entails pushing at the frontiers of ignorance. Topics that seem hot now can cool off. String theory, for example, underwent two revolutionary bursts: in 1984–86 and 1994–2000. Whether it's now waxing, waning, or coasting is unclear.

What's more, rich benefactors have funded research for centuries. In 1704 Thomas Plume, the archdeacon of Rochester, donated funds to his alma mater, the University of Cambridge, for the purpose—in his words—of erecting "an Observatory and to maintain a studious and learned Professor of Astronomy and Experimental Philosophy, and to buy him and his successors utensils and instruments quadrants telescopes etc."

Three years ago Stephen Hawking took up a visiting professorship at the Perimeter Institute. From 1979 until 2009 he was the Lucasian professor of mathematics at Cambridge. The chair was founded in 1663 at the bequest of Henry Lucas, another rich benefactor.

So in this season of giving, let’s toast Lucas, Plume, Lazaridis, and their fellow physics funders, past, present, and—I hope—future.

EDust and nanomedicine standards

2011-12-16T16:28:11Z

Iain M. Banks's 2000 novel Look to Windward closes with a grisly scene of revenge. A priest, or Estodien, of a tiger-like advanced race called the Chelgrians is assassinated for his role in planning a mass-murderous terrorist attack. The instrument of vengeance is EDust, a cloud of weaponized nanoparticles that can rapidly coalesce into different forms, including, as in the following extract, that of a Chelgrian female:

Estodien Visquile opened his mouth to scream for mercy. She became insects—they represented something of a phobia for the Estodien—and poured into his throat, choking him and forcing open the route to his lungs and to his stomach. The insects packed each tiny air-sac in his lungs tight; others bulked out the Estodien's stomach to the point of bursting and beyond, then invaded his body cavity, while others rammed down into the rest of his digestive system, forcing an explosion from his anus.

The Estodien crashed and battered about the shower cabinet lift capsule, smashing the ceramic fittings and denting the plastics. More insects streamed into his ears and forced their way around his horrified, staring eyes, burning their way into his skull while his skin crawled and writhed with the insects which had invaded his body cavity and and gone on to slide their way under his flesh.

The killing of Estodien Visquile is the most horrific use of nanotechnology I've encountered in fiction. EDust, as it's explained in the novel, consists of particles smaller than 100 μm (but with the single exception of a 1-mm-long antimatter missile). "Interestingly," the explanation continued, "the dust had originally been designed as the ultimate building material."

Banks is not opposed to nanotechnology or other advanced technologies. Indeed, his socialist convictions led him to devise the Culture, a pan-galactic civilization of such astounding technological accomplishments that all its citizens, humanoid and AI, are free from having to earn a living.

My first news story about manmade nanoparticles appeared in Physics Today's October 2003 issue. As you can tell from the story's title, "Nanoparticles locate and flag the blood vessels that nourish tumors," the goal of the research I wrote about—treating cancer—is clearly remote from assassination.

But despite the benevolent aim of such research, nanoparticles scare the general public and worry scientists. Nanoparticles seem threatening, I think, because even the power to treat cancer implies an awesome capability that could conceivably be bent toward evil ends. What's more, nanoparticles, like alpha particles and other kinds of ionizing radiation, are invisible.

Reassuring the public that the nanoparticles they might encounter are safe depends on establishing and following strong standards. That effort is under way and is far from easy. Nanotechnolgy Standards (Springer, 2011) contains a chapter on nanomaterial toxicity, which describes the challenge:

While chemical structure is the most important consideration when testing conventional chemicals, nanomaterials are much more complex structures where multiple physico-chemical characteristics are likely to play a key role in defining a nanomaterial's potential toxicity and hazard. For example, researchers have reported relationships between nanomaterial toxicity and parameters such as size, shape, aggregation state and surface chemistry.

Marie Skłodowska-Curie died of a disease, aplastic anemia, that is thought to have been caused by her prolonged exposure to ionizing radiation. Safety standards that might have protected her didn't exist at the time. We know more about nanoparticles than Curie did about radiation. Researchers who work with nanoparticles can presume the particles are toxic and guard against accidental inhalation or ingestion.

The case of medical nanoparticles is different because it involves not just researchers but also patients, doctors, nurses, other hospital workers, and the environment itself. In a September 2011 news story for Nature, Jessica Marshall noted that roughly 250 nanomedicine treatments are currently being tested on humans.

Marshall's story was prompted by the release of a preliminary set of comprehensive recommendations for the oversight of nanomedicine. The final recommendations are expected before the end of the year.

Gleanings from the softer side of a profession

2011-12-05T13:42:41Z

Earlier this year Frances Bajet, a publicist at Cambridge University Press in New York City, sent me an advance copy of Henry Petroski's An Engineer's Alphabet: Gleanings from the Softer Side of a Profession. The book lives up to its subtitle. Browsing through its pages I found entries on asphalt cookies, concrete canoes, practical jokes ("if at all possible, involve a cow"), and slide rules.

But the book also has a harder side. Petroski writes about engineering's history, practice and impact on society. Collectively, his numerous, diverse entries gave me a renewed sense of awe and respect for engineers. The book also made me wonder why I didn't choose to become an engineer myself.

My hometown of Conwy, North Wales, doesn't lack engineering marvels that might have inspired the younger me. A massive 13th-century castle dominates the town. Two of the bridges that span the River Conwy were built by 19th-century titans of civil engineering, Thomas Telford and Robert Stephenson. In high school, I enjoyed, and was good at, metalwork ("shop" in American parlance).

But I preferred science. The aeronautical engineer and investigator of fluids Theodor von Kármán once said, "The scientist describes what is; the engineer creates what never was.” Even if I'd been familiar with Kármán's famous quote, the physicist's quest to understand nature was more attractive to me than the engineer's quest to build new and useful machines.

I know of at least four Nobel Prize–winning physicists who studied engineering before switching to physics: Paul Dirac, Edward Purcell, Carlo Rubbia, and Eugene Wigner. The influence of engineering on Dirac is hard to discern. His most famous contribution to physics was to unify two abstract theories, quantum mechanics and special relativity.

Rubbia wanted to become a physicist in high school, but he switched to engineering when he failed to win a prestigious scholarship. Fate brought him back to physics when one of the scholarship winners resigned his scholarship, which created an opening. The autobiography that Rubbia wrote for the Nobel Foundation leaves you with the impression that he considered his escape from engineering not only lucky but also welcome.

To their evident benefit, Purcell and Wigner pursued engineering further than Dirac and Rubbia did. Purcell earned a bachelor's degree in electrical engineering in from Purdue University. His discoveries of nuclear magnetic resonance in solids and the 21-cm radiation in the cosmos depended on the construction and operation of novel electronic detectors.

Wigner earned a PhD in chemical engineering at what is now the Technical University of Berlin. After graduating, he worked for his father's chemical engineering company. Wigner's engineering background is evident not so much in his theoretical contributions to quantum mechanics, but in his work as a nuclear engineer. He designed the first large-scale nuclear reactors that ran at the Hanford Site in Washington State.

Petroski's An Engineer's Alphabet abounds in evidence that the various kinds of engineering are, like physics, challenging and rewarding. Whether today's high school students pursue engineering, physics, or neither is their choice. But that choice should be made freely and with a familiarity of what those two broad, rich subjects offer.

I hope, therefore, that Petroski's book finds its way into the hands of students and that someone writes a similar book about physics that is just as entertaining, informative, and inspiring.

Charles Day

Super-heavy turkeys and super-heavy elements

2011-11-21T17:50:10Z

Perhaps because I'm immersed in physics, my brain spontaneously makes associations between physics and everyday life. When I glance at a digital clock that says 5:11 pm or at a rowing machine monitor that says I have 511 meters to go, the electron's rest-mass energy, 511 keV, comes to mind. News stories about post-season college football inevitably mention BCS, which makes me think first of the Bardeen-Cooper-Schrieffer theory of superconductivity, not the Bowl Championship Series. If you're a physicist, too, you might be similarly afflicted.

An odder association popped into my mind early last Wednesday evening. As usual, I was listening to American Public Media's Marketplace while preparing dinner. This being the Thanksgiving season, the radio show included a story about the economics of raising turkeys for American dinner tables.

Americans' preference for breast meat led in the 1950s to a selective breeding program that culminated in the Broad Breasted White, a turkey whose breasts are so heavy and whose legs are so short that it cannot mate. Turkey farmers have to artificially inseminate turkey hens with semen collected from toms, like the one shown here. The popularity of the Broad Breasted White's flesh more than makes up for the additional cost of insemination.

So what did I think of when I heard about the economics of turkey insemination? Super-heavy elements. Twelve days before the story was broadcast, the International Union of Pure and Applied Chemistry announced the official names of elements 110, 111, and 112: darmstadtium, roentgenium, and copernicium.

Like the Broad Breasted White, the newly named elements owe their existence to human intervention. Darmstadtium, for instance, was first created on 9 November 1994 at the famous GSI lab outside Darmstadt, Germany. To make it, a team directed by GSI's Sigurd Hofmann fired nickel-62 ions at a target made of lead-208.

But it wasn't artificial synthesis that formed my mental bridge between super-heavy elements and super-heavy turkeys. Rather, it was their instability. Just as the Broad Breasted White is wobbly on its too-short feet, darmstadtium, roentgenium, and copernicium are unstable to nuclear fission. The most stable isotope of roentgenium, ²⁸¹Rg, has a half-life of just 26 seconds.

Turkey meat is rich in the amino acid tryptophan, although only marginally richer than other meats are. Perhaps because serotonin, an anxiety-relieving neurotransmitter, is derived from tryptophan, the amino acid's presence in turkey meat has been identified as the source of postprandial drowsiness on Thanksgiving Day.

Whether or not turkey makes us pleasantly tired, consider this as you tuck into your Thanksgiving meal. Tryptophan is the biggest and heaviest of the 22 standard amino acids. Its chemical formula is C₁₁H₁₂N₂O₂. If a tryptophan molecule is made up of the most abundant isotopes of carbon, hydrogen, nitrogen, and oxygen, then it contains 108 protons and 96 neutrons. A single nucleus of the most stable isotope of copernicium, ²⁸⁵Cn, contains 112 protons and 173 neutrons.

Charles Day

A chat with Australia's chief scientist

2011-11-17T15:05:37Z

Last week I visited the Australian Embassy in Washington, DC, to have a chat with Ian Chubb, Australia's chief scientist. He was in town to promote Australian science and to meet science policy makers. He'd just arrived from London; his next stop was Ottawa.

Chubb is a neuroscientist, whose research focuses on the biochemistry of signal transmission. Before he took up his position, he served as the vice chancellor—that is, the chief executive officer—of the Australian National University in Canberra.

Our hour-long conversation ranged over several topics, including climate change, education, and Australia's bid with New Zealand to host what will become the world's biggest, most sensitive telescope, the Square Kilometre Array (SKA). I was aware of Australia's strengths in astronomy, medicine, and other fields of science. But after listening to Chubb, I came away with the impression that Australia has another, less well-known strength: science policy.

In its population (22.7 million) and GDP ($1.2 trillion), Australia resembles a medium-sized European country. Its scientific output is that of a rich, advanced nation. According to Thomson-Reuters, Australia's share of the world's scientific papers published in 2006–10 was 3.17%, 10 times its share of the world's population. Australia is particularly strong in molecular biology and genetics and in immunology. In both fields in 2008, papers from Australia garnered on average more than 20 citations each.

Geographically of course, Australia is quite different from, say, Spain or the Netherlands. The sixth biggest country in the world, Australia occupies an entire continent and is located almost as far as cartographically possible from both the ancestral homeland of most of its citizens, the UK, and its most powerful military ally, the US.

Australia's unique geography is a factor in its science. The country's vast, largely unpopulated interior provides an excellent site for SKA and other astronomical facilities that require dark or radio-quiet skies. Australia grows enough food to feed three times its population. If climate change imperils Australia's farmland, the loss of production will be felt beyond its borders.

Hot topics

Climate change is a hot political issue in Australia. The failed effort in 2010 to establish a cap-and-trade system for greenhouse emissions led to the resignation of Australia's previous prime minister, Kevin Rudd. On the day I met Chubb, the Australian Senate had just passed a different carbon-limiting scheme. Under the Clean Energy Bill, around 500 power stations, factories, and other heavy users of fossil fuels will be required to buy permits for each ton of carbon dioxide they emit. The revenue will be used to lower personal income tax and to fund clean-energy initiatives.

On climate change, Chubb said he regarded his role as providing the Australian government with the best scientific advice. The evidence in favor of manmade climate change is strong enough that governments should try to slow the pace of change, he said. As for whether a carbon tax is the best course of action and, if so, what its value should be, "That's a matter for economists."

Rich countries, big or small, typically fund individual scientists at similar levels. Size matters when it comes to particle accelerators, satellite observatories, and other expensive projects. Besides the SKA, Australia's biggest project is the Australian Synchrotron, which was completed in 2007 at a cost of $220 million. Using the facility's publications search page, I discovered that the synchrotron has yielded 507 journal articles. (However, the facility has faced funding and leadership problems.)

The recently announced Clean Energy Future amounts to another, big project—or, rather, projects. The multi-faceted initiative includes a finance corporation. Backed with $10 billion from the recently passed carbon tax, the corporation will invest in clean-energy companies that might have difficulty raising capital themselves.

On the topic of science education, Chubb cited a recent survey that revealed, surprisingly, that 70% of the undergraduate students taking chemistry at Australian universities are freshmen. Evidently, Australian undergraduates study chemistry more as a prerequisite for medicine and other subjects rather than as a subject itself. Chubb suspects the same could be true for physics.

Prompted by those and other concerns, Chubb is overseeing a new study of Australia's science skills base and its relevance to the country's present and future needs. Another study led by Chubb will assess Australia's publicly funded research.

Besides seeking to improve the health of science and home, Chubb and his fellow policy makers want Australia to play a bigger international role. Rising ocean temperatures and sea levels threaten the corals that form the Great Barrier Reef, one of the country's most valuable natural assets. By tackling climate change at home, Australia is contributing toward and shaping a global solution.

Charles Day

Why my wife and I didn't buy a Toyota Prius

2011-11-09T14:17:36Z

In April this year my wife and I were involved in a four-car pileup. Neither of us was hurt, but our car, a 1993 Honda Civic hatchback, was written off as a total loss by our insurance company. We had to get a new car.

Because we live in an inner city neighborhood and park on the street, we wanted a small car. We also wanted an economical car, one that would cost little to own and run over a lifetime at least as long as our old Civic's 18 years.

The cost of 18 years' of gasoline is significant. For some cars, it's comparable to the initial cost of buying the car. Would getting a hybrid car end up saving money?

Consumer Reports provides estimates for the overall mileage of cars derived from a representative mix of highway and city driving. For the Honda Fit (the car at the top of our shopping list), CR's overall mileage is 33 mpg. For the Toyota Prius (the world's most popular hybrid), it's 44 mpg.

My 10-mile commute breaks down into 4 miles of city driving and 6 miles of highway. My wife gets to work on the Washington, DC, Metro. In a typical year, we drive about 6250 miles. Maintaining that rate over 18 years yields a lifetime total of 112 500 miles. Driving that distance with CR's overall mileage rates, a Fit would consume 3409 gallons; a Prius, 2557 gallons.

The Prius is considerably more expensive than the Fit. CR gives the range of their MRSP as $23 520 – $39 525 for the Prius and $15 175 – $19 540 for the Fit. Given our driving habits, would a Prius prove cheaper than a Fit in the long, 18-year run?

Not knowing the future price of gasoline, I framed the question as follows: At what gasoline price, averaged over 18 years, would the Prius become cheaper? The answer is $9.79. We bought the Fit shown here.

Going electric

Why not get an electric car? The Nissan Leaf is a four-door hatchback like the Prius and the Fit. At $35 200 – $37 250, its MSRP is as high as that of a fully tricked-out Prius. Even with its high fuel economy (CR gives the Leaf's overall "gas" mileage as 106 mpg), the Fit would still prove cheaper to run. What's more, the Leaf's modest 100-mile range is too short for comfort.

At last week's Industrial Physics Forum in Nashville, Tennessee, I learned that the limit on an electric car's range is due not so much to the capacity of lithium-ion batteries but to their density. You can't arbitrarily increase an electric car's range by adding more batteries without weighing it down.

Even if the ranges of electric cars did match those of gasoline-power cars, electric cars are more expensive. What's more, given that 70% of the electricity in the US is generated by burning fossil fuels, electric cars aren't necessarily greener than gasoline-powered cars. The greenness argument appears valid, but it misses a key point: efficiency.

In the case of electric and gasoline-powered cars, the sequence of energy-conversion steps starts with a fossil fuel and ends in a moving vehicle. Both cases entail burning a fossil fuel to drive a mechanical device, either a power station's turbine or a car's internal combustion engine. The additional steps are different for the two types of car.

For an electric car, you need to convert kinetic energy into electricity, transmit the electricity to an outlet, charge the battery, and power the engine. For a gas-powered car, you need to refine the crude oil and transport the gasoline to a gas station.

I haven't been able to find figures about the efficiencies of all those steps, but everything I've read about oil refining says it consumes a lot of energy. Indeed, according to a 2004 study by the California Energy Commission, oil refineries are the biggest consumers of energy in California.

So my hunch is that even if you live in a state, such as Kentucky, that gets most of its electric power from coal-fired stations, running an electric car is still likely to be the greener option. And if scientists and engineers succeed in building a better battery, I expect my next car will be electric.

Charles Day

A physicist tackles the evolution of word order

2011-10-20T14:52:23Z

Murray Gell-Mann was awarded the 1969 Nobel Prize in Physics for explaining the diversity of baryons and mesons in terms of more rudimentary particles, which he named quarks. If you enter his name into Google Scholar, the citation-based search engine duly returns his classic papers. In the top slot is the 1964 Physics Letters paper that earned him the Nobel.

Gell-Mann's latest paper is not about quarks or complexity, the focus of his research for the past two decades. It's not even about physics. In the 18 October issue of the Proceedings of the National Academy of Sciences (PNAS), you'll find a paper by Gell-Mann and Stanford University linguist Merritt Ruhlen entitled "The origin and evolution of word order."

By word order, Gell-Mann and Ruhlen refer to the basic sequence of subject (S), verb (V), and object (O). They classify English as SVO, as demonstrated by their example, "The man (S) killed (V) the bear (O)." Other word orders are found among the world's 2000 or so languages. Welsh, the first language I studied in school, is VSO. The sentence about bear-killing reads "Fe laddodd (V) y dyn (S) yr arth (O)." Japanese, the last language I studied, is SOV, as in "男は(S) 熊を(O) 殺した (V)."

Gell-Mann and Ruhlen start their fascinating paper by noting that three lines of evidence—from genetics, archaeology, and linguistics—all indicate that humans suddenly started using sophisticated tools and making objects of art around 50 000 years ago. "The cause of this abrupt change has been attributed to the appearance of fully modern human language," they write in their introduction, "and this is a plausible conjecture."

The sudden arrival of modern language suggests a single origin, a linguistic Big Bang. Under that assumption, Gell-Mann and Ruhlen sought to identify the word order of that ancestral modern language. To find it, they looked at the word order of 2011 languages and at those languages' likely family trees. Their conclusion: The first modern language was SOV and that languages in general evolve in the order SOV → SVO → VSO. Welsh, it seems, is more evolved than English.

Gell-Mann isn't the first eminent physicist to study linguistics. Thomas Young (1773–1829) proved the wave nature of light, founded physiological optics, and elucidated elasticity and capillarity. He also helped to decipher the ancient Egyptian hieroglyphs on the Rosetta Stone.

What do physics and linguistics have in common that attracted Young, Gell-Mann, and perhaps others? My hunch is the quest to find order. The list of 2011 languages that Gell-Mann and Ruhlen included in their study is available on the PNAS website. The list is 45 pages long! Making sense of that diversity is a challenging and worthwhile goal.

Charles Day

Hydra, fruit flies, and stripy colonies of bacteria

2011-10-11T15:33:58Z

In 1952, two years before his untimely death at the age of 41, the mathematician Alan Turing wrote an influential paper entitled "The Chemical Basis of Morphogenesis." The paper tackled the problem of how limbs and other structural patterns arise in plants and animals that begin life as undifferentiated blobs of cells.

Turing's mechanism relies on the competition between a slow-diffusing chemical—a morphogen—that activates a reaction and a fast-diffusing chemical that inhibits the reaction. Nudging the reaction-diffusion system into a metastable state yields stable stripes, spots, and other patterns.

Judging by his paper's abstract, Turing was inspired, in part, by Hydra, a genus of simple, water-dwelling animals whose body plan consists of a single sticky foot, a stem, and 1–12 thin, neurotoxin-charged tentacles. Although his mechanism presumes a continuous, two-dimensional system, its basic premise—that pattern development is controlled by the concentration-dependent diffusion and inhibition of signaling molecules—is observed in three-dimensional, multicellular systems, notably in biologists' favorite fly, Drosophila melanogaster.

In common with other signaling molecules, morphogens initiate a complex chain of biochemical steps. For a flavor of that complexity, here's how the University of Tokyo's Testuya Tabata and Yuki Takei described the action of one Drosophila morphogen, Dpp, in a primer published in 2004:

The pathway that transduces the Dpp signal involves a combination of two types of serine/threonine kinase receptors, type I and type II. The activated type I receptor phosphorylates cytoplasmic transducers, so-called receptor-regulated Smads (named after the first-identified members of this family: Sma in C. elegans and Mad in Drosophila), which, upon phosphorylation, translocate into the nucleus and regulate the expression of target genes (Fig. 4A). In Drosophila wing development, Thickveins (Tkv) acts as a type I receptor; its constitutively active form (Tkv*), when ectopically expressed, can induce the expression of the target genes sal and omb (Fig. 4).

Each step in the Dpp pathway provides an opportunity for regulation, thereby helping to ensure that a larval fruit fly stays on course to develop properly functioning wings. Given the high biological stakes—a fly with malformed wings can't feed or breed—the complexity of the Dpp pathway is understandable and evolutionarily inevitable.

A paper published today in Science is noteworthy because it demonstrates a simpler, albeit artificial, route for pattern formation in a multicellular system. Jian-Dong Huang of the University of Hong Kong, Terence Hwa of the University of California, San Diego, and their collaborators genetically modified Escherichia coli so that the single-celled organism would lose its mobility when crowded with other cells from the same mutant strain. Left to proliferate at the center of a nutrient-rich dish, colonies of the mutant spontaneously formed stable, concentric stripes of alternating high and low density.

The genetic engineering that underlay the pattern formation involved three basic steps:

Appropriating the density-sensing gene from another bacterium, Vibrio fischeri. Once equipped with the gene, the mutant E. coli bacteria made and excreted a small molecule called AHL when they crossed a density threshold.
Controlling E.coli's mobility. Usually, when an E. coli bacterium senses a gradient in the concentration of a nutrient, it swims up the gradient. When it can't sense a gradient, it stops, momentarily tumbles, then swims off in a different, random direction. Knocking out a gene called cheZ deprives E. coli of its ability to swim. The Huang–Hwa team modified the genome of their E. coli so that cheZ would be suppressed in the presence of a molecule called CI.
Linking density-sensing to mobility. Another modification caused CI to be synthesized in the presence of AHL, the molecule secreted when the mutant E. coli is crowded.

The stripes result from the bacteria's density-dependent mobility. As a colony starts consuming nutrient and proliferating, the density of bacteria in the center rises and a front of low-density bacteria expands from the center into fresh nutrient. At the center, the proliferating bacteria cross the density threshold at which AHL, through the secretion of CI and the suppression of cheZ, deprives the bacteria of their swimming ability. Those central bacteria still eat and proliferate. As they do so, their density continues to rise until the nutrient is exhausted. The upshot is stable circular patch of high bacterial density.

The bacteria just beyond the central patch are still mobile. Some of them move inward and become trapped; others move outward, remain mobile, and create a second high-density region behind the still-expanding front. As before, when the nutrient runs out, a stable patch of high bacterial density is left behind—this time in the shape of ring. Between the two high-density regions lies a stable low-density region that marks the zone where inward- and outward- moving bacteria met different fates. The creation of ring-shaped stripes continues until the front reaches the edge of the dish and the nutrient runs out.

By formulating a mathematical model of stripe formation, the Huang–Hwa team could predict the conditions under which stripes form and whether they form at all. And by adding an extra genetic modification, one that allows the suppression of cheZ to be tuned, the researchers could test their model. It passed.

The Huang–Hwa team closes its paper by noting that the formation of stripy colonies of bacteria suggests that periodic structures can form autonomously in individual organisms without the intervention of a biological clock. To me, the stripy colonies suggest something else: That the complex pattern formation mechanisms in Drosophila and other higher organisms evolved from something akin to the genetically engineered mechanism in the bacteria.

Charles Day