Archive for the ‘Uncategorized’ Category

by Steve Nadis

In January 1916, Karl Schwarzschild, a German physicist who was stationed as a soldier on the eastern front, produced the first exact solution to the equations of general relativity, Albert Einstein’s radical, two-month-old theory of gravity. General relativity portrayed gravity not as an attractive force, as it had long been understood, but rather as the effect of curved space and time. Schwarzschild’s solution revealed the curvature of space-time around a stationary ball of matter.

Curiously, Schwarzschild noticed that if this matter were confined within a small enough radius, there would be a point of infinite curvature and density — a “singularity” — at the center.

Infinities cropping up in physics are usually cause for alarm, and neither Einstein, upon learning of the soldier’s result, nor Schwarzschild himself believed that such objects really exist. But starting in the 1970s, evidence mounted that the universe contains droves of these entities — dubbed “black holes” because their gravity is so strong that nothing going into them, not even light, can come out. The nature of the singularities inside black holes has been a mystery ever since.

Recently, a team of researchers affiliated with Harvard University’s Black Hole Initiative (BHI) made significant progress on this puzzle. Paul Chesler, Ramesh Narayan and Erik Curiel probed the interiors of theoretical black holes that resemble those studied by astronomers, seeking to determine what kind of singularity is found inside. A singularity is not a place where quantities really become infinite, but “a place where general relativity breaks down,” Chesler explained. At such a point, general relativity is thought to give way to a more exact, as yet unknown, quantum-scale description of gravity. But there are three different ways in which Einstein’s theory can go haywire, leading to three different kinds of possible singularities. “Knowing when and where general relativity breaks down is useful in knowing what theory [of quantum gravity] lies beyond it,” Chesler said.

The BHI group built on a major advance achieved in 1963, when the mathematician Roy Kerr solved Einstein’s equations for a spinning black hole — a more realistic situation than the one Schwarzschild took on since practically everything in the universe rotates. This problem was harder than Schwarzschild’s, because rotating objects have bulges in the center and therefore lack spherical symmetry. Kerr’s solution unambiguously described the region outside a spinning black hole, but not its interior.

Kerr’s black hole was still somewhat unrealistic, as it occupied a space devoid of matter. This, the BHI researchers realized, had the effect of making the solution unstable; the addition of even a single particle could drastically change the black hole’s interior space-time geometry. In an attempt to make their model more realistic and more stable, they sprinkled matter of a special kind called an “elementary scalar field” in and around their theoretical black hole. And whereas the original Kerr solution concerned an “eternal” black hole that has always been there, the black holes in their analysis formed from gravitational collapse, like the ones that abound in the cosmos.

First, Chesler, Narayan and Curiel tested their methodology on a charged, non-spinning, spherical black hole formed from the gravitational collapse of matter in an elementary scalar field. They detailed their findings in a paper posted on the scientific preprint site in February. Next, Chesler tackled the more complicated equations pertaining to a similarly formed rotating black hole, reporting his solo results three months later.

Their analyses showed that both types of black holes contain two distinct kinds of singularities. A black hole is encased within a sphere called an event horizon: Once matter or light crosses this invisible boundary and enters the black hole, it cannot escape. Inside the event horizon, charged stationary and rotating black holes are known to have a second spherical surface of no return, called the inner horizon. Chesler and his colleagues found that for the black holes they studied, a “null” singularity inevitably forms at the inner horizon, a finding consistent with prior results. Matter and radiation can pass through this kind of singularity for most of the black hole’s lifetime, Chesler explained, but as time goes on the space-time curvature grows exponentially, “becoming infinite at infinitely late times.”

The physicists most wanted to find out whether their quasi-realistic black holes have a central singularity — a fact that had only been established for certain for simple Schwarzschild black holes. And if there is a central singularity, they wanted to determine whether it is “spacelike” or “timelike.” These terms derive from the fact that once a particle approaches a spacelike singularity, it is not possible to evolve the equations of general relativity forward in time; evolution is only allowed along the space direction. Conversely, a particle approaching a timelike singularity will not inexorably be drawn inside; it still has a possible future and can therefore move forward in time, although its position in space is fixed. Outside observers cannot see spacelike singularities because light waves always move into them and never come out. Light waves can come out of timelike singularities, however, making them visible to outsiders.

Of these two types, a spacelike singularity may be preferable to physicists because general relativity only breaks down at the point of singularity itself. For a timelike singularity, the theory falters everywhere around that point. A physicist has no way of predicting, for instance, whether radiation will emerge from a timelike singularity and what its intensity or amplitude might be.

The group found that for both types of black holes they examined, there is indeed a central singularity, and it is always spacelike. That was assumed to be the case by many, if not most, astrophysicists who held an opinion, Chesler noted, “but it was not known for certain.”

The physicist Amos Ori, a black hole expert at the Technion in Haifa, Israel, said of Chesler’s new paper, “To the best of my knowledge, this is the first time that such a direct derivation has been given for the occurrence of a spacelike singularity inside spinning black holes.”

Gaurav Khanna, a physicist at the University of Massachusetts, Dartmouth, who also investigates black hole singularities, called the BHI team’s studies “great progress — a quantum leap beyond previous efforts in this area.”

While Chesler and his collaborators have strengthened the case that astrophysical black holes have spacelike singularities at their cores, they haven’t proved it yet. Their next step is to make more realistic calculations that go beyond elementary scalar fields and incorporate messier forms of matter and radiation.

Chesler stressed that the singularities that appear in black hole calculations should disappear when physicists craft a quantum theory of gravity that can handle the extreme conditions found at those points. According to Chesler, the act of pushing Einstein’s theory to its limits and seeing exactly how it fails “can guide you in constructing the next theory.”

S. roeselii is shown here contracting down to where it’s holding onto a surface.

By Yasemin Saplakoglu

Tiny, brainless blobs might be able to make decisions: A single-celled organism can “change its mind” to avoid going near an irritating substance, according to new findings.

Over a century ago, American zoologist Herbert Spencer Jennings conducted an experiment on a relatively large, trumpet-shaped, single-celled organism called Stentor roeselii. When Jennings released an irritating carmine powder around the organisms, he observed that they responded in a predictable pattern, he wrote in his findings, which he published in a text called “Behavior of the Lower Organisms” in 1906.

To avoid the powder, the organism first would try to bend its body around the powder. If that didn’t work, the blob would reverse the movement of its cilia — hairlike projections that help it move and feed — to push away the surrounding particles. If that still didn’t work, the organism would contract around its point of attachment on a surface to feed. And finally, if all else failed, it would detach from the surface and swim away.

In the decades that followed, however, other experiments failed to replicate these findings, and so they were discredited. But recently, a group of researchers at Harvard University decided to re-create the old experiment as a side project. “It was a completely off-the-books, skunkworks project,” senior author Jeremy Gunawardena, a systems biologist at Harvard, said in a statement. “It wasn’t anyone’s day job.”

After a long search, the researchers found a supplier in England who had collected S. roeselii specimens from a golf course pond and had them shipped over to Gunawardena’s lab. The team used a microscope to observe and record the behavior of the organisms when the scientists released an irritant nearby.

First, they tried releasing carmine powder, the 21st century organisms weren’t irritated like their ancestors were. “Carmine is a natural product of the cochineal beetle, so its composition may have changed since [Jennings’] day,” the researchers wrote in the study. So they tried another irritant: microscopic plastic beads.

Sure enough, the S. roeselii started to avoid the beads, using the behaviors that Jennings described. At first, the behaviors didn’t seem to be in any particular order. For example, some organisms would bend first, then contract, while others would only contract. But when the scientists did a statistical analysis, they found that there was indeed, on average, a similar order to the organisms’ decision-making process: The single-celled blobs almost always chose to bend and alter the direction of their cilia before they contracted or detached and swam away, according to the statement.

What’s more, the researchers found that, if the organism did reach the stage of needing to contract or detach, there was an equal chance that they would choose one behavior over the other.

“They do the simple things first, but if you keep stimulating, they ‘decide’ to try something else,” Gunawardena said. “S. roeselii has no brain, but there seems to be some mechanism that, in effect, lets it ‘change its mind’ once it feels like the irritation has gone on too long.”

The findings can help inform cancer research and even change the way we think about our own cells. Rather than being solely “programmed” to do something by our genes, “cells exist in a very complex ecosystem, and they are, in a way, talking and negotiating with each other, responding to signals and making decisions,” Gunawardena said. Single-celled organisms, whose ancestors once ruled the ancient world, might be “much more sophisticated than we generally give them credit for,” he said.

The findings were published Dec. 5 in the journal Current Biology.

Neurons in the brain. Rather than implanting directly into the brain, the bionic neurons are built into ultra-low power microchips that form the basis for devices that would plug straight into the nervous system.

Scientists have created artificial neurons that could potentially be implanted into patients to overcome paralysis, restore failing brain circuits, and even connect their minds to machines.

The bionic neurons can receive electrical signals from healthy nerve cells, and process them in a natural way, before sending fresh signals on to other neurons, or to muscles and organs elsewhere in the body.

One of the first applications may be a treatment for a form of heart failure that develops when a particular neural circuit at the base of the brain deteriorates through age or disease and fails to send the right signals to make the heart pump properly.

Rather than implanting directly into the brain, the artificial neurons are built into ultra-low power microchips a few millimetres wide. The chips form the basis for devices that would plug straight into the nervous system, for example by intercepting signals that pass between the brain and leg muscles.

“Any area where you have some degenerative disease, such as Alzheimer’s, or where the neurons stop firing properly because of age, disease, or injury, then in theory you could replace the faulty biocircuit with a synthetic circuit,” said Alain Nogaret, a physicist who led the project at the University of Bath.

The breakthrough came when researchers found they could model live neurons in a computer program and then recreate their firing patterns in silicon chips with more than 94% accuracy. The program allows the scientists to mimic the full variety of neurons found in the nervous system.

Writing in the journal Nature Communications, the researchers describe how they fed the program with data recorded from two types of rat neuron, which were stimulated in a dish. The neurons were either from the hippocampus, a region that is crucial for memory and learning, or were involved in the subconscious control of breathing.

Armed with the program, the researchers claim they can now build bionic neurons based on any of the real nerve cells found in the brain, spinal cord, or the more distant reaches of the peripheral nervous system, such as the sensory neurons in the skin.

Because the artificial neurons both receive and send signals, they can be used to make implants that respond to neural feedback signals that are constantly coursing around the body.

“The potential is endless in terms of understanding how the brain works, because we now have the fundamental understanding and insight into the functional unit of the brain, and indeed applications, which might be to improve memory, to overcome paralysis and ameliorate disease,” said Julian Paton, a co-author on the study who holds posts at the Universities of Bristol and Auckland.

“They can be used in isolation or connected together to form neuronal networks to perform brain functions,” he added.

With development, trials and regulations to satisfy, it could be many years before the artificial neurons are helping patients. But if they prove safe and effective, they could ultimately be used to circumvent nerve damage in broken spines and help paralysed people regain movement, or to connect people’s brains to robotic limbs that can send touch sensations back through the implant to the brain.

Despite the vast possibilities the artificial neurons open up, Nogaret said the team was nowhere near building a whole brain, an organ which in a human consists of 86bn neurons and at least as many supporting cells. “We are not claiming that we are building a brain, there’s absolutely no way,” he said.

The scientists’ approach differs from that taken by many other peers who hope to recreate brain activity in computers. Rather than focusing on individual neurons, they typically model brain regions or even whole brains, but with far less precision. For example, the million-processor SpiNNaker machine at the University of Manchester can model an entire mouse brain, but not to the level of individual brain cells.

“If you wanted to model a whole mouse brain using the approach in this paper you might end up designing 100 million individual, but very precise, neurons on silicon, which is clearly unfeasible within a reasonable time and budget,” said Stephen Furber, professor of computer engineering at the University of Manchester.

“Because the approach is detailed and laboriously painstaking, it can really only be applied in practice to smallish neural units, such as the respiratory neurons described above, but there are quite a few critical small neural control circuits that are vital to keeping us alive,” he added.

by David Nield

Scientists researching a key aspect of biochemistry in living creatures have been taking a very close look at the tiny Caenorhabditis elegans roundworm. Their latest results show that when these nematodes get put under more biochemical stress early in their lives, they somehow tend to live longer.

This type of stress, called oxidative stress – an imbalance of oxygen-containing molecules that can result in cellular and tissue damage – seems to better prepare the worms for the strains of later life, along the same lines as the old adage that whatever doesn’t kill you, makes you stronger.

You might think that worm lifespans have no bearing on human life. And surely, until we have loads more research done in this field, it would be a big leap to say the same principles of prolonging one’s lifespan might hold true for human beings.

But there’s good reason to put C. elegans through the paces. This model organism has proven immensely helpful for researchers trying to better understand key biological functions present in worm and human alike – and oxidative stress is one such function.

The little wriggly creatures are known to have significant variations in their lifespan even when the whole population is genetically identical and grows up in the exact same conditions. So the team went looking for other factors that affect C. elegans’ longevity.

“The general idea that early life events have such profound, positive effects later in life is truly fascinating,” says biochemist Ursula Jakob from the University of Michigan.

Jakob and her colleagues sorted thousands of C. elegans larvae based on the oxidative stress levels they experienced during development – this stress arises when cells produce more oxidants and free radicals than they can handle. It’s a normal part of the ageing process, but it’s also triggered by exercise and a limited food supply.

One way to measure this stress is by the levels of reactive oxygen species (ROS) molecules an organism produces – simply put, this measurement indicates the biochemical stress an organism is under. In the case of these roundworms, the more ROS were produced during development, the longer their lifespans turned out to be.

To explain how this effect of ROS might come about, the researchers went looking for changes in the worms’ genetic regulation, specifically those genes that are known to be involved in dealing with oxidative stress.

While doing so, they detected a key difference – the nematodes exposed to more ROS during development appeared to have undergone an epigenetic change (a gene expression switch that can happen due to environmental influences) that increased the oxidative stress resistance of their body’s cells.

There are still a lot of questions to answer, but the researchers think their results identify one of the stochastic – or random – influences on the lifespan of organisms; it’s something that has been hypothesised in the field of the genetics of ageing. And down the line, it may turn out to be relevant for ageing humans, too.

“This study provides a foundation for future work in mammals, in which very early and transient metabolic events in life seem to have equally profound impacts on lifespan,” the researchers conclude.

The study has been published in Nature.

The remains of a Viking ship that was 52 to 56 feet (16 to 17 meters) long were found near a medieval church at Edøy, on the island of Smøla in Norway.

by Owen Jarus

The remains of a Viking ship have been discovered on a farm near a medieval church at Edøy, on the island of Smøla, in Norway.

The ship, which is 52 to 56 feet (16 to 17 meters) long, appears to be part of a burial mound, suggesting that it was used to bury someone important, said its discoverers, archaeologists Manuel Gabler and Dag-Øyvind Engtrø Solem, both with the Norwegian Institute for Cultural Heritage Research (NIKU).

They don’t know if there is a skeleton or multiple skeletons inside the boat.

The archaeologists used high-resolution georadar mounted on a cart to make the discovery. In fact, it was almost by chance they spotted the ship’s outline.

“We had actually finished the agreed-upon area, but we had time to spare and decided to do a quick survey over another field. It turned out to be a good decision,” Manuel Gabler, an archaeologist with NIKU, said in a statement.

The ship was found near this medieval church by archaeologists using georadar mounted on a cart. (Image credit: NIKU)

The ship dates back more than 1,000 years to the time of the Vikings or even a bit earlier, Knut Paasche, head of the Department of Digital Archaeology at NIKU and an expert on Viking ships, said in a statement.

Radar images had enough resolution to make out what was left of the fore and aft, which had been nearly destroyed in the past by farming plows. The hull seems to be in good shape, according to a news report by Ars Technica. The radar also revealed the remains of two houses, likely part of a Viking settlement, but the archaeologists aren’t sure of the structures’ age. Archaeologists and local authorities hope to do a larger survey of the area around the ship burial. It’s not certain when the ship itself will be excavated, although it won’t be done in the near future, said a spokesperson for NIKU.

The survey at Edøy was done as a collaboration between Møre and Romsdal County, Smøla municipality and NIKU. The Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology helped develop the georadar technology used in the survey.

Although it has been revealed in recent years that plants are capable of seeing, hearing and smelling, they are still usually thought of as silent. But now, for the first time, they have been recorded making airborne sounds when stressed, which researchers say could open up a new field of precision agriculture where farmers listen for water-starved crops.

Itzhak Khait and his colleagues at Tel Aviv University in Israel found that tomato and tobacco plants made sounds at frequencies humans cannot hear when stressed by a lack of water or when their stem is cut.

Microphones placed 10 centimetres from the plants picked up sounds in the ultrasonic range of 20 to 100 kilohertz, which the team says insects and some mammals would be capable of hearing and responding to from as far as 5 metres away. A moth may decide against laying eggs on a plant that sounds water-stressed, the researchers suggest. Plants could even hear that other plants are short of water and react accordingly, they speculate.

“These findings can alter the way we think about the plant kingdom, which has been considered to be almost silent until now,” they write in their study, which has not yet been published in a journal.

Previously, devices have been attached to plants to record the vibrations caused by air bubbles forming and exploding – a process known as cavitation – inside xylem tubes, which are used for water transport. But this new study is the first time that sounds from plants have been measured at a distance.

On average, drought-stressed tomato plants made 35 sounds an hour, while tobacco plants made 11. When plant stems were cut, tomato plants made an average of 25 sounds in the following hour, and tobacco plants 15. Unstressed plants produced fewer than one sound per hour, on average.

It is even possible to distinguish between the sounds to know what the stress is. The researchers trained a machine-learning model to discriminate between the plants’ sounds and the wind, rain and other noises of the greenhouse, correctly identifying in most cases whether the stress was caused by dryness or a cut, based on the sound’s intensity and frequency. Water-hungry tobacco appears to make louder sounds than cut tobacco, for example.

Although Khait and his colleagues only looked at tomato and tobacco plants, they believe other plants may make sounds when stressed too. In a preliminary study, they also recorded ultrasonic sounds from a spiny pincushion cactus (Mammillaria spinosissima) and the weed henbit dead-nettle (Lamium amplexicaule). Cavitation is a possible explanation for how the plants generate the sounds, they say.

Enabling farmers to listen for water-stressed plants could “open a new direction in the field of precision agriculture”, the researchers suggest. They add that such an ability will be increasingly important as climate change exposes more areas to drought.

“The suggestion that the sounds that drought-stressed plants make could be used in precision agriculture seems feasible if it is not too costly to set up the recording in a field situation,” says Anne Visscher at the Royal Botanic Gardens, Kew, in the UK.

She warns that the results can’t yet be broadened out to other stresses, such as salt or temperature, because these may not lead to sounds. In addition, there have been no experiments to show whether moths or any other animal can hear and respond to the sounds the plants make, so that idea remains speculative for now, she says.

If plants are making sounds when stressed, cavitation is the most likely mechanism, says Edward Farmer at the University of Lausanne, Switzerland. But he is sceptical of the findings, and would like to see more in the way of controls, such as the sounds of drying soil without plants in it.

Farmer adds that the idea moths might be listening to plants and shunning stressed ones is a “little too speculative”, and there are already plenty of explanations for why insects avoid some plants and not others.

Reference: bioRxiv, DOI: 10.1101/507590

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Peeling a banana doesn’t require the nimblest of fingers. It’s basically Nature’s version of a twist-off bottle cap. Anyone with any kind of digits can get to the tasty slip of sweetness inside. But what if even that was too much of a bother? Why not just chomp right through the skin and be done with it?

Well, some experts suggest you can do just that. As Australian dietitian Susie Burrell notes on her blog, eating the whole banana may go a long towards reducing food waste and upping your nutritional intake.

“You will increase your overall fibre content by at least 10 percent as a lot of dietary fibre can be found in the skin of the banana,” she writes. “You will get almost 20 percent more Vitamin B6 and almost 20 percent more Vitamin C and you will boost both your potassium and magnesium intake.”

But the real question is, would you like to bite into a whole banana? Or does the idea of eating a banana peel sound more like an insult you might sling at someone? Maybe you’re face is all puckered up right now at the very thought of it.

There’s an important caveat. Burrell, mercifully, doesn’t advise hunkering down on the whole banana. Instead, you’re going to want to remove that skin and cook it on its own — breaking down the tough cellular walls and making those nutrients more readily absorb-able (and the whole affair, perhaps a little less gag-able.)

Burrell is hardly alone in endorsing whole-banana consumption. As the site Treehugger points out, Americans devour 12 billion bananas per year. That’s 12 billion banana peels needless discarded — and maybe even 12 billion opportunities someone will slip and have a terrible accident.

It also represents a lot of nutrients and other potential benefits being chucked to the curb. According to a study published in the Journal of Immunology Research by scientists at Seoul National University, a typical yellow peel packs substantial amounts of potassium, dietary fiber, polyunsaturated fats and essential amino acids.

Those nutrients do a lot of good for a body — particularly all that potassium, which can regulate blood pressure and keep hearts and kidneys healthy.

Sure, there’s plenty of potassium already in nature’s sweetest candy — about 422 milligrams in the average serving. But with an added 78 milligrams of the stuff — along with so many other nutrients — why not eat the wrapper too?

Well, aside from a banana peel needing a little preparation to be fully digestible, there are also those agricultural ne’er-do-wells known as pesticides. The outer layers of fruits and vegetables tend to stockpile somewhat worrisome levels of pesticide residue, although federal bodies like the United States Department of Agriculture (USDA) and the Food and Drug Administration (FDA) were established to keep undue amounts of pesticides out of the food chain.

Still, as with just about anything you aim to put in your mouth, a banana peel needs careful washing. That’s likely to minimize any potential pesticide menace. Even better, if you’re going to try eating the skin, consider picking up the organic variety at your local farmers market.