Three months after his bone marrow transplant, Chris Long of Reno, Nev., learned that the DNA in his blood had changed. It had all been replaced by the DNA of his donor, a German man he had exchanged just a handful of messages with...More worth reading at the link.
But four years after his lifesaving procedure, it was not only Mr. Long’s blood that was affected. Swabs of his lips and cheeks contained his DNA — but also that of his donor. Even more surprising to Mr. Long and other colleagues at the crime lab, all of the DNA in his semen belonged to his donor. “I thought that it was pretty incredible that I can disappear and someone else can appear,” he said...
Mr. Long had become a chimera, the technical term for the rare person with two sets of DNA. The word takes its name from a fire-breathing creature in Greek mythology composed of lion, goat and serpent parts. Doctors and forensic scientists have long known that certain medical procedures turn people into chimeras, but where exactly a donor’s DNA shows up — beyond blood — has rarely been studied with criminal applications in mind...He added that patients also sometimes ask him what it means for a man to have a woman’s chromosomes in their bloodstream or vice versa. “It doesn’t matter,” he said.
But for a forensic scientist, it’s a different story. The assumption among criminal investigators as they gather DNA evidence from a crime scene is that each victim and each perpetrator leaves behind a single identifying code — not two...
In 2004, investigators in Alaska uploaded a DNA profile extracted from semen to a criminal DNA database. It matched a potential suspect. But there was a problem: The man had been in prison at the time of the assault. It turned out that he had received a bone marrow transplant. The donor, his brother, was eventually convicted...
In 2008, he was trying to identify the victim of a traffic accident for the National Forensic Service in Seoul, South Korea. Blood showed that the individual was female. But the body appeared to be male, which was confirmed by DNA in a kidney, but not in the spleen or the lung, which contained male and female DNA. Eventually, he figured out that the victim had received a bone marrow transplant from his daughter.
A crippling strain of polio virus is no more. Officials confirmed Thursday that global health efforts have wiped it out, moving humanity one step closer to completely eradicating the highly infectious virus from the planet.
The obliterated strain—wild poliovirus type 3 (WPV3)—is one of only three wild strains of polio. It is the second to be globally eradicated. Health officials declared WPV2 eradicated in 2015. That leaves only one wild strain remaining: WPV1.
This “historic” announcement falls on World Polio Day and is based on the recent conclusion of the independent Global Commission for the Certification of Poliomyelitis Eradication, set up in part by the World Health Organization. The announcement comes after years of careful and painstaking global surveillance to certify that WPV3 no longer exists anywhere in the world, apart from specimens preserved in secure containment. The last known case of WPV3 occurred in northern Nigeria in 2012.
Mathematically, it's easy to demonstrate that a working general-purpose quantum computer can easily outperform classical computers on some problems. Demonstrating it with an actual quantum computer, however, has been another issue entirely. Most of the quantum computers we've made don't have enough qubits to handle the complex calculations where they would clearly outperform a traditional computer. And scaling up the number of qubits has been complicated by issues of noise, crosstalk, and the tendency of qubits to lose their entanglement with their neighbors. All of which raised questions as to whether the theoretical supremacy of quantum computing can actually make a difference in the real world.
Over the weekend, the Financial Times claimed that Google researchers had demonstrated "quantum supremacy" in a draft research paper that had briefly appeared on a NASA Web server before being pulled. But the details of what Google had achieved were left vague. In the interim Ars has acquired copies of the draft paper, and we can confirm the Financial Times' story. More importantly, we can now describe exactly what Google suggests it has achieved.
In essence, Google is sampling the behavior of a large group of entangled qubits—53 of them—to determine the statistics that describe a quantum system. This took roughly 30 seconds of qubit time, or about 10 minutes of time if you add in communications and control traffic. But determining those statistics—which one would do by solving the equations of quantum mechanics—simply isn't possible on the world's current fastest supercomputer.
The phenomenal success of our integrated circuits managed to obscure an awkward fact: they're not always the best way to solve problems. The features of modern computers—binary operations, separated processing and memory, and so on—are extremely good at solving a huge range of computational problems. But there are things they're quite bad at, including factoring large numbers, optimizing complex sets of choices, and running neural networks.
Even before the performance gains of current processors had leveled off, people were considering alternative approaches to computing that are better for some specialized tasks. For example, quantum computers could offer dramatic speed-ups in applications like factoring numbers and database searches. D-Wave's quantum optimizer handles (wait for it) optimization problems well. And neural network computing has been done with everything from light to a specialized form of memory called a memristor.
But the list of alternative computing architectures that have been proposed is actually larger than the list of things that have actually been implemented in functional form. Now, a team of Japanese and American researchers have added an additional entry to the "functional" category: probabilistic computing. Their hardware is somewhere in between a neural network computer and a quantum optimizer, but they've shown it can factor integers using commercial-grade parts at room temperature.
Due to complicated gravitational interactions from planets and other bodies, it's expected that our Solar System has ejected various small bodies like comets and asteroids. Since exosolar systems are likely to do the same, it's thought that the vast distances of interstellar space are sparsely populated by these small bodies. As such, we should expect one of these objects to wander through our Solar System, an expectation that was confirmed in 2017 with the arrival of 'Oumuamua, an odd, cigar-shaped object that shot through the Solar System at an extreme angle.
Now, just two years later, we seem to have our second. Officially termed C/2019 Q4 (Borisov), the comet is approaching the inner Solar System at an angle that almost certainly indicates it didn't originate here.
Right now, there's not much public information about C/2019 Q4 (Borisov). A press release from the Jet Propulsion Lab provides some basic details. Discovered on August 30, it takes its name from Gennady Borisov, who spotted it from an observatory in the Crimea. Since then, observations have firmed up its orbit, indicating that it will make its closest approach to the Sun in December, passing no closer than Mars' orbit.
Superconductivity came with a lot of unfulfilled promises. Power without loss? Sign me up. Superconducting magnetic resonance imaging magnets? They're, ahem, cool. And CERN couldn’t operate without buckets of liquid helium to keep its magnets superconducting.
But those examples highlight the problem: pretty much all practical applications for superconductivity require liquid helium temperatures. The search for high-temperature superconductors has taken us to many weird places, including strange substances that only form at high pressure. Now we can add another of those substances to the list: a hydride that only forms under protest. Once formed, though, it may be a superconductor way above room temperature.
Why are we still looking for superconductors?
The search for superconductors goes on because current superconductors come with a number of challenges. If the magnetic field is too strong, superconductivity vanishes. Likewise, if the current density exceeds a certain limit, the resistance appears, which heats the conductor, leading to rapid—and rapidly expanding—failure. And the liquid helium needed to keep things cool in the first place is expensive.
Up until the mid-20th century, light was pretty ordinary. Yes, it was both a particle and a wave, but it didn’t do anything very weird. Then scientists, under-employed after the end of World War II, started paying more attention to the properties of light. This was, in part, driven by the availability of surplus searchlights, which could be turned into cheap arrays of light detectors to measure the properties of stars.
That began the photon gold rush, with scientists identifying all sorts of interesting potential behaviors. But actually observing them would require having rather special light sources, which didn’t exist. Now, scientists have shown that our own Sun can be turned into one of these light sources.
A herd of identical photons
When two photons are indistinguishable, they can be made to play some unexpected tricks. The diagram below shows an example: two identical photons hit a partially reflective mirror at the same time. We cannot predict where they will go, but wherever it is, they go together. If the world was classical, we would expect that each behaves independently, and half the time, they would choose different directions. But we're in a quantum world, so this doesn't happen.
Design studio and research lab, Matter Design, partnered with CEMEX Global R&D to explore the idea of moveable concrete assemblages for possible use in hard to reach areas or situations where heavy machinery is not available or accessible.
In a project called Walking Assembly, Matter Design adds:
The mysterious knowledge surrounding the transportation and placement of megalithic structures of the past eludes contemporary building practices. Walking Assembly re-introduces the potentials of that ancient knowledge to better inform the transportation and assembly of future architectures. If a brick is designed for a single hand, and a concrete masonry unit (CMU) is designed for two, these massive masonry units (MMU) unshackle the dependency between size and the human body.
Intelligence of transportation and assembly is designed into the elements themselves, liberating humans to guide these colossal concrete elements into place. Structures that would otherwise rely on cranes or heavy equipment can now be intelligently assembled and disassembled with little energy. By using variable density concrete, the center of mass of the object is calibrated precisely to control the stable, but easy motion of the elements. This ensures that these massive elements successfully walk and assemble into place, creating the possibility for a crane-less tilt up construction method and turning our building sites into spectacles of play.
“More than one reality exists” screams the headline. Cue sighs of tired dread from physicists everywhere as they wonder what otherwise bland result has been spun out of control.
In this case, though, it turns out that the paper and the underlying theory are much more interesting than that takeaway. Essentially, modern physics tells us that two observers of the same event may never agree on the result, even if they have all possible knowledge. This is already accepted as part of special relativity, but now we have experimental proof that it applies to quantum mechanics as well.
What Galileo and Einstein tell us
Let’s start with the simplest possible example of how we typically resolve conflicting measurements. I am standing on a platform and measure the speed of an approaching train to be 180km/hr. You are on the train and measure the speed of the train to be 0km/hr. We can resolve the difference by making an additional measurement on our relative speeds. Afterward, we both know that we’ve measured the speed correctly relative to our own motion.
We as a species would be miserable without yeast. Baker's yeast has given us leavened bread for thousands of years. And I don’t even want to begin to imagine a world without beer and wine, which rely on yeast to convert sugar into alcohol.
Now researchers have turned to yeast to do something more improbable: manufacturing the cannabis compounds CBD and THC. By loading brewer’s yeast with genes from the cannabis plant, they’ve turned the miracle microbes into cannabinoid factories. It’s a clever scheme in a larger movement to methodically pick apart and recreate marijuana’s many compounds, to better understand the plant’s true potential.
SpaceX is set to launch a Falcon 9 rocket on Thursday night, and while it may not be the primary payload, a small Israeli lunar lander is by far the mission's most intriguing payload.
The 180kg Beresheet spacecraft, privately developed by SpaceIL in Israel and funded largely through philanthropy, will spend more than six weeks raising its orbit and becoming captured into lunar orbit before finally making the first private attempt to land on the Moon. Until now, only the US, Russian, and Chinese space agencies have ever successfully landed on the Moon.
This means there is a lot of pressure on the small Israeli team leading the mission, both in their native country and among the commercial lunar community, which wants to prove that private ventures can do what only nations have done before. "What it means to me is that the responsibility is very high," said Yoav Landsman, a senior systems engineer for the project, in an interview.
Late Tuesday night, scientists at NASA's Jet Propulsion Laboratory sent their final data uplink to the Opportunity rover on Mars. Over this connection, via the Deep Space Network, the American jazz singer Billie Holiday crooned "I'll Be Seeing You," a song that closes with the lines:
I'll find you in the morning sun
And when the night is new
I'll be looking at the moon
But I'll be seeing you
The scientists waited to hear some response from their long-silent rover, which had been engulfed in a global dust storm last June, likely coating its solar panels in a fatal layer of dust. Since then, the team of scientists and engineers has sent more than 835 commands, hoping the rover will wake up from its long slumber—that perhaps winds on Mars might have blown off some of the dust that covered the panels.
Hermit crabs use the scavenged shells of other animals as their homes. As the crabs grow, they periodically need to upgrade their housing to bigger shells. When a new shell appears on the beach, the cramped crabs will form a orderly queue nearby and then change shells all at once, with each crab moving into the next biggest shell just abandoned by its former occupant. This is possibly the most British thing I’ve ever seen an animal do…and the David Attenborough narration is the icing on top.Tags: David Attenborough video
The vast majority of our DNA—the chromosomes in the nucleus of each cell—is just what you’d expect: a mix of genetic material from both mother and father. But mitochondria are an exception. They contain a relatively tiny amount of DNA, and in nearly all mammals and even unicellular organisms, that DNA comes strictly from the mother. We've even used that fact to trace the spread of humanity around the globe.
But in 2002, researchers in Copenhagen reported a jaw-dropping finding. In an effort to work out why one of their patients had extreme fatigue during exercise despite seeming healthy in many respects, they started examining his mitochondria—the energy-generating power stations living in each cell. What they found floored them: the man had mitochondrial DNA (mtDNA) that matched both his father's and his mother's.
Since 2002, no other cases of paternally inherited mtDNA have been reported in humans, despite several research groups actively looking. But a paper in this week’s PNAS reports mtDNA inherited from both parents in 17 different people from three families. This kind of inheritance is still extremely rare and seems potentially linked to mitochondrial disease, but the robust confirmation of it in humans is huge news for biology and medicine.
The Johnson Indoor Track at MIT probably won't go down in history in the same way as Kitty Hawk has, but it was the scene of a first in powered flight. A team of researchers has managed to build the first aircraft powered by an ionic wind, a propulsion system that requires no moving parts. While the flight took place using a small drone, the researchers' calculations suggest that the efficiency of the design would double simply by building a larger craft.
In conventional aircraft, air is pushed around by moving parts, either propellers or the turbines within jet engines. But we've known for a while that it's also possible to use electrical fields to push air around.
The challenge is that air is largely made of uncharged molecules that don't respond to electric fields. But at sufficiently high voltages, it's possible to ionize the nitrogen and oxygen that make up our atmosphere, just as lightning does all the time. The electrons that are liberated speed away, collide with other molecules, and ionize some of them as well. If this takes place in an electric field, all those ions will start moving to the appropriate electrode. In the process, they'll collide with neutral molecules and push them along. The resulting bulk movement of atmospheric molecules is called an ionic wind.
People love taking online quizzes; just ask Buzzfeed and Facebook. A new study has sifted through some of the largest online data sets of personality quizzes and identified four distinct "types" therein. The new methodology used for this study—described in detail in a new paper in Nature Human Behavior—is rigorous and replicable, which could help move personality typing analysis out of the dubious self-help section in your local bookstore and into serious scientific journals.
Frankly, personality "type" is not the ideal nomenclature here; personality "clusters" might be more accurate. Paper co-author William Revelle (Northwestern University) bristles a bit at the very notion of distinct personality types, like those espoused by the hugely popular Myers-Briggs Type Indicator. Revelle is an adamant "anti-fan" of the Myers-Briggs, and he is not alone. Most scientists who study personality prefer to think of it as a set of continuous dimensions, in which people shift where they fall on the spectrum of various traits as they mature.
What's new here is the identification of four dominant clusters in the overall distribution of traits. Revelle prefers to think of them as "lumps in the batter" and suggests that a good analogy would be how people tend to concentrate in cities in the United States.
Pasta purists insist on plonking dry spaghetti into the boiling pot whole, but should you rebel against convention and try to break the strands in half, you'll probably end up with a mess of scattered pieces.
Now, two MIT mathematicians have figured out the trick to breaking spaghetti strands neatly in two: add a little twist as you bend. They outlined their findings in a new paper in the Proceedings of the National Academy of Sciences.
This isn't the first time scientists have been fascinated by the physics of breaking spaghetti. The ever-curious Richard Feynman famously spent hours in his kitchen one night in a failed attempt to successfully break spaghetti strands neatly in half. It should have worked, he reasoned, because the strand snaps when the curvature becomes too great, and once that happens, the energy release should reduce the curvature. The spaghetti should straighten out and not break any further. But no matter how hard he tried, the spaghetti would break in three or more pieces.
A couple months ago, an atmospheric study revealed that someone had started producing an ozone-depleting pollutant that had been banned under an international agreement to protect the ozone layer. The new source was preventing the chemical from dissipating on schedule. Although the researchers were careful about what they could conclude from regional measurements, they found that eastern Asia was likely the source.
Now, a UK-based NGO called the Environmental Investigation Agency (EIA) says that it has uncovered a number of Chinese companies that are responsible. If you’re expecting an elaborate infiltration and undercover sting... adjust your expectations. The investigation seems to have been shockingly easy, with the culprits’ representatives strangely amenable to detailing their illegal operations.
Mystery solved through Google
The EIA started with a simple Internet search, which turned up a few companies that were apparently advertising sales of the banned chemical, known as CFC-11. Like other CFCs, 11 can be used as a refrigerant or a propellant in aerosol spray cans. But it was also widely use to “inflate” foam insulation, and that seems to be the market where at least some of its illicit use has continued.
New research from Google's UK-based DeepMind subsidiary demonstrates that deep neural networks have a remarkable capacity to understand a scene, represent it in a compact format, and then "imagine" what the same scene would look like from a perspective the network hasn't seen before.
Human beings are good at this. If shown a picture of a table with only the front three legs visible, most people know intuitively that the table probably has a fourth leg on the opposite side and that the wall behind the table is probably the same color as the parts they can see. With practice, we can learn to sketch the scene from another angle, taking into account perspective, shadow, and other visual effects.
A DeepMind team led by Ali Eslami and Danilo Rezende has developed software based on deep neural networks with these same capabilities—at least for simplified geometric scenes. Given a handful of "snapshots" of a virtual scene, the software—known as a generative query network (GQN)—uses a neural network to build a compact mathematical representation of that scene. It then uses that representation to render images of the room from new perspectives—perspectives the network hasn't seen before.
Anyone who has tried to pull a late-night study session and wound up rereading the same pages of their textbook because they couldn't focus has experienced it. And countless studies confirm it: if you're sleep deprived, your brain starts functioning poorly. Your reaction times slip, you are more prone to careless actions, and you generally just get bad at things. But how is it your body registers "too little sleep"? It could be after you spend too much time awake. Or it could be the amount of sleep you get in a 24-hour period. Or it could be tracked in relationship to your body's internal 24-hour circadian clock.
A new study out this week suggests it's not just one of these things, and different aspects of our mental capacities are either more sensitive or less sensitive depending on how we end up short on sleep.
The challenge with separating out different aspects of sleep deprivation in the real world is that anything you do will involve multiple aspects of sleep. Get too little sleep during a 24-hour cycle, which means more awake time—and awake at times your circadian clock says you shouldn't be. So, the researchers behind the new work messed with people's clocks. They got a small group of people (because it would be hard to recruit a large one) to live at a sleep center for 32 days, cut off from any indication of outside time.
The Montreal Protocol—a 1987 international agreement to end production of ozone-destroying chemicals like freon—seems miraculous compared to the long struggle to achieve meaningful action on climate change. Even more astonishing is that the agreement has worked. Those chemicals (known as CFCs) take a long time to flush out of the atmosphere, but monitoring has shown that the flushing is proceeding largely according to plan.
That keeps the hole in the ozone layer on track to shrink over the coming decades. However, a new study shows that someone has been cheating in the last few years.
A group of researchers led by Stephen Montzka of the US National Oceanic and Atmospheric Administration had been tracking the progress of CFCs and noticed something off with CFC-11. This chemical has been used as a refrigerant, solvent, and propellant for aerosol spray cans, as well as in the production of styrofoam. As with the other CFCs, nations agreed to end production of CFC-11 entirely. While there may still be some older machines leaking CFC-11, these sources should gradually disappear over time, allowing the decline of its atmospheric concentration to accelerate.
Scientists studying data from NASA's Juno spacecraft have published a trove of papers in Nature this week, making a number of intriguing and surprising findings about the atmosphere of the largest planet in our Solar System. The papers are summarized and linked in this NASA news release.
Some of the most striking discoveries come from visible and infrared observations made by Juno during its first five science passes in its elongated orbit around Jupiter. (The spacecraft entered Jupiter's orbit on July 4, 2016. It will make its 11th pass on April 1.) In these initial passes, scientists found clusters of strange and long-lasting cyclones orbiting the north and south poles of Jupiter.