Walking the halls of one of the world’s great art museums, it’s easy to regard familiar classic paintings as eternal and unchanging. But this is not the case. Paintings are a mix not only of color but of chemistry—and chemistry changes. In some of Vincent van Gogh’s works, the striking, sunny yellows have faded and turned brownish, robbing the Dutch master’s art of some of its trademark intensity. So a European team of scientists decided to find out exactly what was happening on those canvases.
Using sophisticated X-ray machines, they discovered the chemical reaction to blame — one never before observed in paint. Ironically, van Gogh’s decision to use a lighter shade of yellow paint mixed with white is responsible for the unintended darkening, according to a study published online Monday in the journal Analytical Chemistry. [Los Angeles Times]
Vincent loved yellow. In particular, he loved chrome yellow, a 19th century invention that shone brighter than previously available hues of paint. Art preservationists have known that the lead-based paint fades under intense sunlight, so they’ve done what they can to keep van Goghs and similar works out of intense light. What’s curious about his paintings, however, is that some yellows have faded while others have not.
It’s not like this week was the first appearance of the full-body X-ray scanners in American airports. Yet, thanks to the looming holiday travel season, leaked X-ray images that were supposed to be kept private, and high-profile rebellion by pilots’ organizations and disgruntled passengers, anger is rising against the Transportation Security Administration’s new airport rules. Under the policy, those chosen for extra screening face the dilemma of having their naked bodies revealed to TSA scanners or opting out and having agents feel them up in search of explosives.
But behind the outrage at being asked to surrender even more of our dignity just to get on a plane, there’s another full-body scanning issue simmering: the health dangers of radiation.
How much radiation, and where?
This was the main concern of the Allied Pilots Association. Pilots are already exposed to higher levels of radiation than nearly all professionals because they spend so much time at altitude and receive radiation from space; asking them to take an X-ray every time they get on a plane (even one that the TSA says is thousands of times less intense than a hospital chest X-ray) was asking too much. Popular Mechanics posted more details on pilot exposure.
So what about the rest of us, who fly perhaps only a few times per year? Back in May, professors at the University of California, San Francisco, led by John Sedat sent a letter to the Food and Drug Administration with a litany of red flags about using back-scatter X-ray with such frequency—mostly that the safety has not be independently proven. The FDA finally replied with a lengthy letter citing study after study that show full-body scanning is safe, the agency says.
Neanderthals, it would appear, grew up in a big hurry. In a new study in the Proceedings of the National Academy of Sciences this week, Harvard anthropologists who studied Neanderthal teeth samples say that the evidence captured in those teeth show the rate at which they developed. Compared with human children, Neanderthal kids raced though their developing years and into adulthood, the researchers say.
Tanya Smith and colleagues used advanced X-ray scans of the tooth fossils of Neanderthals and the humans who lived concurrently with them to discover the layers therein. She says such scans reveal “growth lines” that serve the same purpose as tree rings–they allow researchers to measure the individual’s development year by year, and to determine his or her exact age at death.
Even when compared to some of the earliest human teeth, taken from remains of humans who left Africa 90,000 to 100,00 years ago, the differences were clear. Human teeth grew more slowly, pointing to more leisurely periods of youth. “This indicates that the elongation of childhood has been a relatively recent development,” the study said. [AFP]
The results were so staggering that they stopped the study ahead of schedule to get the word out: A giant study by the National Cancer Institute of more than 50,000 heavy smokers has found a 20 percent reduction in deaths among patients who received a CT scan to catch potential cancer as opposed to a simple X-ray.
“This is huge,” said Dr. Reggie Munden, a University of Texas M.D. Anderson diagnostic radiologist who led the research conducted at the Houston cancer center, one of 33 sites nationally. “It’s a massive ray of hope that we can now offer a scientifically proven test to people at risk of lung cancer and pick up tumors before they’re considered lethal.” [Houston Chronicle]
Participants in the study, which began in 2002, had smoked about a pack a day for at least 30 years (or the equivalent—two packs for 15 years). They received a screening via either CT scan or X-ray three times a year. While the X-ray group lost 442 people to lung cancer, the CT group saw only 354 lung cancer deaths.
The Christmas Day airplane bombing attempt has renewed the debate over full body scanners at airports. The Transportation Security Administration in recent years has tried out a series of “whole-body imagers” to look for threats that typical metal detectors can’t find. These systems are the only way that smuggled explosives, like the one officials say was brought on the Christmas flight, can be reliably found [Wired.com].
Privacy advocates are calling the full body scanners a “digital strip search” (take a look at this TSA image of a full body scan and you’ll get the idea). But some security advocates say that either patting down every passenger or taking full body scans are the only options to ensure certain dangerous items are kept off airplanes.
Are CT scans putting thousands of people in unnecessary jeopardy for cancers and death? That was the suggestion by two new studies out this week, leaving radiologists scrambling to explain the true level of danger to worried patients.
A CT scan, also known as computed tomography, gives doctors a view inside the body, often eliminating the need for exploratory surgery. But CT scans involve a much higher radiation dose than conventional X-rays. A chest CT scan exposes the patient to more than 100 times the radiation dose of a typical chest X-ray [Reuters]. However, a study out of the University of California, San Francisco says, we might not have as good a handle on CT radiation as we thought. The researchers found that radiation differed greatly between machines, and some emitted 13 times more than others.
The elites of ancient Egypt had money, power, divine status in the case of the pharaohs, and also heart disease. In a study in today’s issue of The Journal of the American Medical Association, a team of researchers reports performing x-ray scans of 20 Egyptian mummies and finding them rife with cardiovascular disease like clogged arteries, one of the commonest ailments in modern American society.
On a visit to the Museum of Egyptian Antiquities in Cairo, one of the researchers had been intrigued by a nameplate on the remains of Pharaoh Merenptah, who died in 1,203BC. The plate said the pharaoh died at the age of 60 and suffered diseased arteries, arthritis and tooth decay [The Guardian]. So the scientists obtained permission to scan that mummy and others in the museum collection.
The common people of ancient Egypt weren’t mummified; only elites like royal families, their nursemaids, and priests got such a treatment. The elites ate salted fish, bread, and cheese like everyone else, but they also dined on rich foods such as cow, sheep, and goat meat, as well as honey and cakes with butter, says Abdel Nureldin, a professor of Egyptology at Cairo University, who worked on the investigation. At the same time, virtually no one in ancient times was sedentary, and that may have helped counteract their fatty diets [ScienceNOW Daily News].
Peeling a roll of ordinary sticky tape can generate 100 milliwatt pulses of X-rays, enough to capture a human finger on X-ray film, according to a new study by UCLA scientists. They claim to have found the cheapest way to produce X-rays of that scale. “At some point we were a little bit scared,” says Juan Escobar, a member of the research team. But he and his co-workers soon realized that the X-rays were only emitted when the kit was used in a vacuum [Nature News].
Their kit consisted of a vacuum-enclosed machine, reminiscent of a video casette player, that peeled a roll of Photo Safe 3M Scotch tape at a rate of 3 cm per second. Rapid pulses of X-rays, each about a billionth of a second long, emerged from very close to where the tape was coming off the roll. That’s where electrons jumped from the roll to the sticky underside of the tape that was being pulled away, a journey of about two-thousandths of an inch, Escobar said. When those electrons struck the sticky side they slowed down, and that slowing made them emit X-rays [AP]. This type of energy release is known as triboluminescence — the same principle behind the fun trick of crunching on Wint-O-Green Live Savers to produce blue sparks.
In a neat marriage of science and art, researchers used x-rays from a particle accelerator to reveal an early portrait of a woman by Vincent Van Gogh, which the impoverished artist later painted over with a meadow scene. The hidden image bears a striking resemblance to a series of somber portraits the artist produced in the Dutch town of Nuenen, where he composed “The Potato Eaters,” completed in 1885 and regarded as his first major work [Los Angeles Times].
An earlier analysis using conventional x-rays had shown the rough shape of a head hidden beneath the surface of a painting called “Patch of Grass,” but provided no details. To get a clearer image, the researchers used high-intensity x-rays from a particle accelerator in Hamburg, Germany to compile a two-dimensional map of the metallic atoms on the painting beneath “Patch of Grass.”… Knowing that mercury atoms were part of a red pigment and the antimony atoms were part of a yellow pigment, they were able to chart those colors in the underlying image. “We visualized — in great detail — the nose, the eyes, according to the chemical composition.” [researcher Joris] Dik said. Scanning a roughly 7-inch square of the larger portrait took two full days [AP].