Small World: Quantum Identity Crisis Observed

Small World: Quantum Identity Crisis Observed

A quantum enigma has been put to the test once again, but this time physicists have made the experiment smaller than it has ever been.

The classic double-slit experiment tests the behavior of light, electrons, atoms and some molecules as both particle-like and wave-like, a mysterious duality that has intrigued and puzzled scientists for more than a century.

Light or electrons are aimed at a solid plate with two parallel cuts in it, offering two choices: go through the slit on the left or the slit on the right. Subatomic particles will sometimes break the rules and go through both slits, just as a wave would.

The most bizarre aspect of this particle-wave duality is that it depends on how much an observer pays attention. The more carefully the observer measures whether it was the left or right slit, the more the object in question chooses a single slit, just as a particle would.

Now an international team of scientists has exhibited this quantum identity crisis using a single hydrogen molecule as their lab equipment.

In this case, an incoming X-ray beam strikes the hydrogen molecule, thereby liberating the two electrons that typically buzz around the molecule's two central nuclei. But before these electrons shoot off into the surrounding space, they make a quick pass by one of the nuclei, which act like left and right slits.

The researchers concentrated on the "fast electron" that carried away the majority of the energy. As expected, the fast electron acted sometimes like a wave and sometimes like a particle.

Interestingly, this behavior depended on the other "slow electron," which interacted very slightly with the fast electron and in so doing played the part of the "observer."

If the slow electron had little energy, it had trouble measuring the fast electron's movement. As a consequence, the fast electron went through both slits like a wave. But if the slow electron had more energy, it got a good look at the fast electron, which responded by choosing one slit like a particle.

The results, detailed in the Nov. 9 issue of the journal Science, give some insight into how a future quantum computer might work as it relies on the phenomena of "superposition" and "entanglement" to perform operations on data stored in units called quantum bits.  

 
After being freed from a hydrogen molecule by an X-ray (pink line), two electrons fly off into space but continue to interact with each other (as depicted by wavy yellow line). This interaction determines whether the electrons act more like particles or waves.

Scientists find fossil of enormous bug

Scientists find fossil of enormous bug

This was a bug you couldn't swat and definitely couldn't step on. British scientists have stumbled across a fossilized claw, part of an ancient sea scorpion, that is of such large proportion it would make the entire creature the biggest bug ever.

How big? Bigger than you, and at 8 feet long as big as some Smart cars.

The discovery in 390-million-year-old rocks suggests that spiders, insects, crabs and similar creatures were far larger in the past than previously thought, said Simon Braddy, a University of Bristol paleontologist and one of the study's three authors.

"This is an amazing discovery," he said Tuesday.

"We have known for some time that the fossil record yields monster millipedes, super-sized scorpions, colossal cockroaches, and jumbo dragonflies. But we never realized until now just how big some of these ancient creepy-crawlies were," he said.

The research found a type of sea scorpion that was almost half a yard longer than previous estimates and the largest one ever to have evolved.

The study, published online Tuesday in the Royal Society's journal Biology Letters, means that before this sea scorpion became extinct it was much longer than today's average man is tall.

Prof. Jeorg W. Schneider, a paleontologist at Freiberg Mining Academy in southeastern Germany, said the study provides valuable new information about "the last of the giant scorpions."

Schneider, who was not involved in the study, said these scorpions "were dominant for millions of years because they didn't have natural enemies. Eventually they were wiped out by large fish with jaws and teeth."

Braddy's partner paleontologist Markus Poschmann found the claw fossil several years ago in a quarry near Prum, Germany, that probably had once been an ancient estuary or swamp.

"I was loosening pieces of rock with a hammer and chisel when I suddenly realized there was a dark patch of organic matter on a freshly removed slab. After some cleaning I could identify this as a small part of a large claw," said Poschmann, another author of the study.

"Although I did not know if it was more complete or not, I decided to try and get it out. The pieces had to be cleaned separately, dried, and then glued back together. It was then put into a white plaster jacket to stabilize it," he said.

Eurypterids, or ancient sea scorpions, are believed to be the extinct aquatic ancestors of today's scorpions and possibly all arachnids, a class of joint-legged, invertebrate animals, including spiders, scorpions, mites and ticks.

Braddy said the fossil was from a Jaekelopterus Rhenaniae, a kind of scorpion that lived only in Germany for about 10 million years, about 400 million years ago.

He said some geologists believe that gigantic sea scorpions evolved due to higher levels of oxygen in the atmosphere in the past. Others suspect they evolved in an "arms race" alongside their likely prey, fish that had armor on their outer bodies.

Braddy said the sea scorpions also were cannibals that fought and ate one other, so it helped to be as big as they could be.

"The competition between this scorpion and its prey was probably like a nuclear standoff, an effort to have the biggest weapon," he said. "Hundreds of millions of years ago, these sea scorpions had the upper hand over vertebrates — backboned animals like ourselves."

That competition ended long ago.

But the next time you swat a fly, or squish a spider at home, Braddy said, try to "think about the insects that lived long ago. You wouldn't want to swat one of those." 

This is a computer generated image issued by the University of Bristol in England released on Tuesday Nov. 20, 2007 showing a size comparison between a human an ancient sea scorpion. A fossil found in Germany indicates...

 

Is Disease "Inheritance" More Random than Once Thought?

Is Disease "Inheritance" More Random than Once Thought?

Random and frequent cellular deactivation of one of two gene copies could potentially change a genetic outcome 

GOLD MARKS THE SPOT: Random inactivation of one of the two copies of genes passed on by parents is a more common occurrence than previously thought.

New research shows that cells often randomly deactivate one of a pair of gene copies or alleles, one of which they get from mom, the other from dad. This inactivation may potentially help explain why some children in a family may exhibit certain heritable disorders, whereas others do not.

Researchers at Massachusetts General Hospital (MGH) in Boston found that such disruptions may take place in as many as 1,000 genes in the autosomal genome (the part of our genetic repertoire that excludes sex cells), leading to different outcomes in the structures and levels of the proteins coded by these genes. These arbitrary alterations may, in some cases, clear a pathway for certain diseases such as Alzheimer's to manifest themselves.

"The general principle is that when a gene is turned on by a given cell or cell type that both alleles get expressed," says Harvard Medical School's Andrew Chess, a associate professor of medicine at MGH's Center for Human Genetic Research and co-author of the new study published in Science. "We've now found a large number of examples of an exception to that."

The finding could speak to more heterogeneity between individuals than can be accounted for by basic genetics. Though Chess and his colleagues do not know the mechanism by which alleles are silenced, the discovery that these events—called random monoallelic expression—occur so frequently suggests that epigenetic effects (influences on the activity of a gene that are not due directly to DNA mutations) may play a much more significant role in the development of some human diseases than previously believed.

Occurrences of allele inactivation are not new to researchers, although fewer than 1 percent of the genome undergoes a process called imprinting, in which an allele is transcribed into RNA and translated into a protein only if it comes from a specific parent. For instance, the IGF2 gene, which codes for the hormone insulinlike growth factor 2 in fetal liver cells, is only activated if it comes from the father. A version of monoallelic expression takes place in all female cells, where one of the two X chromosomes is randomly inactivated to eliminate redundancy. Genes that code for olfactory receptors, immunoglobulins (which produce antigens that trigger immune responses) and T cell receptors (that recognize antigens), also occur in populations of cells that express only one of their alleles, which actually results in a greater repertoire of antigens and receptors.

With the new work, the quantity of genes known to be vulnerable to this has ballooned to between 5 and 10 percent of the entire genome.

Chess's team took advantage of DNA microarray technology to survey the activity of certain gene variants in the genome of human B lymphocytes (white blood cells that, like T cells, help fight infection). By cataloguing point mutations in the genetic code, they could decipher when two different alleles were being transcribed from DNA into RNA (the template that provides the recipes to build specific proteins). They focused on a sample of just under 4,000 genes, nearly 400 of which appeared to undergo monoallelic expression.

Of those 400, several had previously been linked with human disorders, such as APP, the gene for amyloid beta precursor protein, which in excess quantities is believed to up the risk of Alzheimer's disease. Although no genes seemed immune to this process, researchers detected an abundance of cell receptor–coding genes in the mix. "The overabundance of receptors and other surface proteins suggests a role for monoallelic expression in each given cell's interactions with other nearby cells," the authors write in the Science paper.

Rolf Ohlsson, group leader of the mammalian epigenetics lab at Sweden's Uppsala University, wrote in an accompanying editorial that the findings may cause a shift in perspective on how scientists view illnesses believed to have a genetic component. "Anyone unfortunate enough to possess the 'wrong' set of monoallelically expressed genes might be susceptible to the earlier onset of a complex disease, such as Alzheimer's," his commentary read. "Considering the interplay among genotype, epigenotype and gene inactivation [these findings] will become more important in understanding developmental mechanisms and the penetrance of diseases in an individual as well as responses to medical treatments."

Next up: Chess says his lab will try to find triggers for monoallelic expression and probe whether genes can produce protein from one or both alleles at different times throughout a person's life span.

Our Evolving Present

Our Evolving Present

Human changes to the environment are accelerating evolution in many ecosystems

The cane toads go bump in the night. I hear them banging as they misjudge where my hotel door ends and the forest begins. The force of a large toad knocking wood is substantial. But the force with which the toads, which are native to Central America, have hit Australia is even greater. Brought to Queensland in 1935 to combat beetles infesting sugarcane fields, the toads have spread out from their point of entry like the shock waves of a bomb, warty legs and oversize tongues jettisoned into every conceivable ecological crack.

Recent research by Ben Phillips and his collaborators at the University of Sydney has shown that the toads are evolving as they spread, perfecting their ability to adapt to the Australian landscape. The toads at the front edge of the invasion now have smaller bodies, reduced toxicity and relatively longer legs, apparently because individuals with those traits were having greater success. The native fauna has evolved in response: the mouths of some snake species are getting smaller, for instance, because so many of the snakes with big mouths were eating the poisonous cane toads and dying off.

Such examples are changing scientists’ views of the speed of evolution. The process was long considered to be slow, even lumbering. Increasingly, though, researchers are observing evolution in action. You may be familiar with the examples of the evolution of drug-resistant bacteria or agricultural pests. Microbes and pests may change the fastest, but they are not unique.

We see rapid evolution most often where some force (often us) has given it a jump start by suddenly and dramatically altering an organism’s environment. Rats have developed smaller bodies when introduced to islands. Trophy fish have also adopted smaller body sizes in response to fishers’ preference for big fish (which, if killed, do not breed). Mayflies in streams where trout were released now forage at night to avoid the fast-swimming predators. Many hundreds of herbivorous species have switched to novel, sometimes toxic, food sources introduced by humans and have come to specialize in consuming those new resources. Various native species have evolved in response to newly arrived competitors. Cedar trees have begun making toxins to protect themselves from being eaten by deer now roaming in their formerly benign habitats. Mussels in New England have evolved the ability to detect invasive green crabs and produce thicker shells where the crabs are present.

Most of these changes appear to have resulted from natural selection: organisms that by chance had some genetic trait that helped them thrive in the face of a new stress were favored, and subsequently they reproduced successfully and spread the helpful trait to future generations. But some evolutionary changes we see may simply be the result of genetic drift (random genetic changes that accrue over time).

The more we look, the more we can observe evolutionary changes that are fast enough to be seen during the course of a single study. A Ph.D. student might, in the five or so years of a dissertation project, realistically see the development of new species, whether in real time or using genetic tools to reconstruct evolutionary history. As house mice and rats have spread with us around the world, they have speciated into forms best adapted to the different regions where they live. In the northeastern U.S., a species of fly has evolved to feed on a species of honeysuckle introduced to North America less than 250 years ago. Although the new fly is a hybrid between two existing species, it can mate with neither one and maintains viable populations of its own.

People tend to imagine evolution as acting only on long-extinct creatures such as the dinosaurs, but the flensing knives of natural selection and the random pushes and pulls of genetic drift are still at work today. We see a red oak tree in our backyard or a cane toad at our hotel-room door, but the names fool us. These species are not the same this year and next. Although the evolution we observe in real time will not suddenly give us dinosaurs, it is still a process to be reckoned with. Give natural selection a few individuals of any species, and it will work the same way in a waste pool as it does in Yellowstone National Park. Nature abhors a vacuum, but nearly anything else will do.

Earth's Moon is Rare Oddball

Earth's Moon is Rare Oddball

The moon formed after a nasty planetary collision with young Earth, yet it looks odd next to its watery orbital neighbor. Turns out it really is odd: Only about one in every 10 to 20 solar systems may harbor a similar moon.

New observations made by NASA's Spitzer Space Telescope of stellar dust clouds suggest that moons like Earth's are—at most—in only 5 to 10 percent of planetary systems.

"When a moon forms from a violent collision, dust should be blasted everywhere," said Nadya Gorlova, an astronomer at the University of Florida in Gainesville who analyzed the telescope data in a new study. "If there were lots of moons forming, we would have seen dust around lots of stars. But we didn't."

Gorlova and her team detail their findings in today's issue of the Astrophysical Journal.

Violent birth

Shortly after the sun formed about 4.5 billion years ago, scientists think a vagrant planet as big as Mars smacked into infant Earth and ripped off a chunk of our home's smoldering mantle. The rocky, dusty leftovers fell into orbit around our wounded planet, eventually coalescing into the moon we see today.

The scenario is unique among other moons in the solar system, which formed side-by-side with their planet or were captured by its gravity. Gorlova and her colleagues looked for the dusty signs of similar smash-ups around 400 stars, all about 30 million years old—roughly the age of our sun when Earth's moon formed.

Only one of all the stars they studied, however, displayed the telltale dust. Considering the frequency of planetary solar systems, the amount of time the dust should stick around and the window for moon-forming collisions to occur, the scientists were able to peg the frequency of extrasolar bodies that formed like our moon.

The estimate, however, is possibly a generous one.

"We don't know that the collision we witnessed around the one star is definitely going to produce a moon," said study co-author George Rieke, an astronomer at the University of Arizona in Tucson, "so moon-forming events could be much less frequent than our calculation suggests."

Odd moon out?

Planetary scientists like Gorlova and Rieke think infant solar systems can form moons between 10 and 50 million years after a star forms. That only a single star with collision-generated dust could be found in their latest research, the astronomers said, indicates that the 30 million-year-old stars in the study have finished making their planets.

"Astronomers have observed young stars with dust swirling around them for more than 20 years now," said Gorlova, noting that the dust could be collision-derived or primitive planet-forming material. "The star we have found is older, at the same age our sun was when it had finished making planets and the Earth-moon system had just formed in a collision."

While most the our type of moon may be rare, astronomers think there are billions of rocky planets out there with plenty of moons orbiting around them. The upshot for lunar lovers? There could be millions—or billions—of Earth-like moons drifting through the cosmos.