星空女人频道: 2013-06-09

2013年6月15日星期六

Memory-boosting chemical identified in mice

The same biochemical pathway the molecule acts on might one day be targeted in humans to improve memory, according to the senior author of the study, Peter Walter, PhD, UCSF professor of biochemistry and biophysics and a Howard Hughes Investigator.

The discovery of the molecule and the results of the subsequent memory tests in mice were published in eLife, an online scientific open-access journal, on May 28, 2013.

In one memory test included in the study, normal mice were able to relocate a submerged platform about three times faster after receiving injections of the potent chemical than mice that received sham injections.

The mice that received the chemical also better remembered cues associated with unpleasant stimuli -- the sort of fear conditioning that could help a mouse avoid being preyed upon.

Notably, the findings suggest that despite what would seem to be the importance of having the best biochemical mechanisms to maximize the power of memory, evolution does not seem to have provided them, Walter said.

"It appears that the process of evolution has not optimized memory consolidation; otherwise I don't think we could have improved upon it the way we did in our study with normal, healthy mice," Walter said.

The memory-boosting chemical was singled out from among 100,000 chemicals screened at the Small Molecule Discovery Center at UCSF for their potential to perturb a protective biochemical pathway within cells that is activated when cells are unable to keep up with the need to fold proteins into their working forms.

However, UCSF postdoctoral fellow Carmela Sidrauski, PhD, discovered that the chemical acts within the cell beyond the biochemical pathway that activates this unfolded protein response, to more broadly impact what's known as the integrated stress response. In this response, several biochemical pathways converge on a single molecular lynchpin, a protein called eIF2 alpha.

Scientists have known that in organisms ranging in complexity from yeast to humans different kinds of cellular stress -- a backlog of unfolded proteins, DNA-damaging UV light, a shortage of the amino acid building blocks needed to make protein, viral infection, iron deficiency -- trigger different enzymes to act downstream to switch off eIF2 alpha.

"Among other things, the inactivation of eIF2 alpha is a brake on memory consolidation," Walter said, perhaps an evolutionary consequence of a cell or organism becoming better able to adapt in other ways.

Turning off eIF2 alpha dials down production of most proteins, some of which may be needed for memory formation, Walter said. But eIF2 alpha inactivation also ramps up production of a few key proteins that help cells cope with stress.

Study co-author Nahum Sonenberg, PhD, of McGill University previously linked memory and eIF2 alpha in genetic studies of mice, and his lab group also conducted the memory tests for the current study.

The chemical identified by the UCSF researchers is called ISRIB, which stands for integrated stress response inhibitor. ISRIB counters the effects of eIF2 alpha inactivation inside cells, the researchers found.

"ISRIB shows good pharmacokinetic properties [how a drug is absorbed, distributed and eliminated], readily crosses the blood-brain barrier, and exhibits no overt toxicity in mice, which makes it very useful for studies in mice," Walter said. These properties also indicate that ISRIB might serve as a good starting point for human drug development, according to Walter.

Walter said he is looking for scientists to collaborate with in new studies of cognition and memory in mouse models of neurodegenerative diseases and aging, using ISRIB or related molecules.

In addition, chemicals such as ISRIB could play a role in fighting cancers, which take advantage of stress responses to fuel their own growth, Walter said. Walter already is exploring ways to manipulate the unfolded protein response to inhibit tumor growth, based on his earlier discoveries.

At a more basic level, Walter said, he and other scientists can now use ISRIB to learn more about the role of the unfolded protein response and the integrated stress response in disease and normal physiology.

Additional UCSF study authors are Diego Acosta-Alvear, PhD, Punitha Vedantham, PhD, Brian Hearn, PhD, Ciara Gallagher, PhD, Kenny Ang, PhD, Chris Wilson, PhD, Voytek Okreglak, PhD, Byron Hann, MD, PhD, Michelle Arkin, PhD, and Adam Renslo, PhD. Other authors are Han Li, PhD, and Avi Ashkenazi, PhD, from Genentech; and, Karim Nader, PhD, Karine Gamache, and Arkady Khoutorsky, PhD, from McGill University. The study was funded by the Howard Hughes Medical Institute.

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Bioenergy potential unearthed in leaf-cutter ant communities

June 14, 2013 — As spring warms up Wisconsin, humans aren't the only ones tending their gardens.

At the University of Wisconsin-Madison Department of Bacteriology, colonies of leaf-cutter ants cultivate thriving communities of fungi and bacteria using freshly cut plant material.

While these fungus gardens are a source of food and shelter for the ants, for researchers, they are potential models for better biofuel production.

"We are interested in the whole fungus garden community, because a lot of plant biomass goes in and is converted to energy for the ants," says Frank Aylward, a bacteriology graduate student and researcher with the Great Lakes Bioenergy Research Center.

Aylward is the lead author of a study identifying new fungal enzymes that could help break down cellulosic -- or non-food -- biomass for processing to fuel. His work appears on the cover of the June 15 issue of the journal Applied and Environmental Microbiology.

"All the enzymes that we found are similar to known enzymes, but they are completely new; no one had identified or characterized them until now, " Aylward says.

Building on Aylward's previous study of these gardens, the researchers relied on genome sequencing provided by the U.S. Department of Energy Joint Genome Institute (JGI) and support from Roche Applied Science's 10 Gigabase Grant Program to understand the unique roles of fungi and bacteria. In addition to sequencing the genome of Leucoagaricus gongylophorous, the fungus cultivated by leaf-cutting ants, the researchers looked at the genomes of entire, living garden communities.

"We really tried as thoroughly as possible to characterize the biomass degrading enzymes produced," Aylward says. "Identifying all these new enzymes really opens the door to technological applications, because we could potentially mix and match them with others that we already know about to achieve even better biomass degradation."

In a symbiotic relationship, L. gongylophorous provides food for the leaf-cutter ant Atta cephalotes by developing fruiting bodies rich in fats, amino acids and other nutrients. To fuel production of these fruiting bodies, the fungus needs sugar, which comes in the form of long cellulose molecules packed inside the leaf clippings the ants deliver. To get at the sugars, the fungus produces enzymes that break the cellulose apart into glucose subunits.

After sequencing the L. gongylophorous genome, the researchers noticed that the fungus seemed to be doing the lion's share of cellulose degradation with its specialized enzymes. However, they also realized that it was by no means working alone: in fact, the gardens are also home to a diversity of bacteria that may help boost the fungus's productivity.

"We think there could potentially be a division of labor between the fungus and bacteria," says Garret Suen, co-author of the study and a UW-Madison assistant professor of bacteriology and Wisconsin Energy Institute researcher.

The researchers have a few leads in their investigation of the mysterious role of bacteria in leaf-cutter ant communities, which they are pursuing in collaboration with JGI. In addition to providing nitrogen and key vitamins, the bacteria appear to help the fungus access energy-rich cellulose by breaking apart other plant polymers that encase it, such as hemicellulose.

Accessing and deconstructing cellulose is also the goal of GLBRC researchers, who want to ferment the stored sugars to ethanol and other advanced biofuels. Enzymes such as those of the leaf-cutting ants' fungus specialize in breaking down leaves, but understanding how they work in the context of the ant community could help researchers create similar methods for processing cellulosic biofuel feedstocks, such as corn stalks and grasses.

The researchers are discovering, however, that both the beauty and the challenge of the leaf-cutter ant garden lie in its complexity. A peek into UW-Madison's resident colony in the Microbial Sciences Building reveals a metropolis of brown insects bustling around the pale, pitted surface of the fungus garden, many with leaf sections held aloft. The strong resemblance to a small city drives home the point that energy production in such a meticulously coordinated system would be difficult to replicate in a lab or a bio-refinery.

"In an industrial setting, you need a system that's reproducible, sustainable, controlled -- and that produces a consistent level of ethanol," Suen says.

A potential alternative to re-creating these natural processes is to extract, replicate and purify biomass-degrading enzymes synthetically. New enzymes could be added to known combinations and tested for their ability to break down biofuel feedstocks. However, this process can be time-consuming and costly.

To put their findings in perspective, the researchers plan to study other insects in addition to ants, including certain species of termites and beetles, which also act as gardeners in fungal communities. They hope that a better understanding of these complex systems will help them share their biomass-degrading secrets with bioenergy researchers.

"It's difficult to think that we can actually find a process that improves on nature," says Aylward, "so it probably makes sense to learn from it."

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AMS marks down 2013 revenue on order delays

LONDON – Analog IC and sensor company AMS AG, formerly known as Austriamicrosystems, has said it expects its lower sales in the second half of 2013 because ramp ups for some designed-in chips are now expected to occur late in 2013 or the first months of 2014.

The forecast given alongside the first quarter financial results on April 22, was that 2013 full year revenue growth would exceed 10 percent compared to 2012 with even stronger growth in profitability.

In the latest guidance AMS (Unterpremstaetten, Austria) said it still expects year-on-year revenue growth in 2013 but did not quantify this. AMS said it has several design wins for its chips in upcoming smartphone and tablet computer device platforms that are now expected to ramp in 2014. AMS said it will report second quarter and first half 2013 results including a business outlook for the third quarter 2013 on July 22.

Prior to the announcement of the 1Q13 financial results John Heugle, then CEO, had informed the supervisory board of the company that he would not extend his contract beyond February 2014 but that he would continue to serve with full commitment as CEO up until then. AMS subsequently announced that Heugle had agreed to step down from the position of CEO of the company with immediate effect and that Kirk Laney, head of the optical sensors and lighting business unit, had become interim CEO.

Related links and articles:

www.ams.com

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What's in a name? Plenty, says CEO of former austriamicrosystems

AMS nears production on ISO26262-standard products

Automotive chips drag AMS profit down

AMS sues Melexis over patents

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From the mouths of babes: Toddlers' speech is far more advanced than previously thought

June 14, 2013 — The sound of small children chattering away as they learn to talk has always been considered cute -- but not particularly sophisticated. However, research by a Newcastle University expert has shown that toddlers' speech is far more advanced than previously understood.

Dr Cristina Dye, a lecturer in child language development, found that two to three- year-olds are using grammar far sooner than expected.

She studied fifty French speaking youngsters aged between 23 and 37 months, capturing tens of thousands of their utterances.

Dr Dye, who carried out the research while at Cornell University in the United States, found that the children were using 'little words' which form the skeleton of sentences such as a, an, can, is, an, far sooner than previously thought.

Dr Dye and her team used advanced recording technology including highly sensitive hidden microphones placed close to the children, to capture the precise sounds the children voiced. They spent years painstakingly analysing every minute sound made by the toddlers and the context in which it was produced.

They found a clear, yet previously undetected, pattern of sounds and puffs of air, which consistently replaced grammatical words in many of the children's utterances.

Dr Dye said: "Many of the toddlers we studied made a small sound, a soft breath, or a pause, at exactly the place that a grammatical word would normally be uttered."

"The fact that this sound was always produced in the correct place in the sentence leads us to believe that young children are knowledgeable of grammatical words. They are far more sophisticated in their grammatical competence than we ever understood.

"Despite the fact the toddlers we studied were acquiring French, our findings are expected to extend to other languages. I believe we should give toddlers more credit -- they're much more amazing than we realised."

For decades the prevailing view among developmental specialists has been that children's early word combinations are devoid of any grammatical words. On this view, Cchildren then undergo a 'tadpole to frog' transformation where due to an unknown mechanism; , they start to develop grammar in their speech. Dye's results now challenge the old view.

Dr Dye said: "The research sheds light on a really important part of a child's development. Language is one of the things that makes us human and understanding how we acquire it shows just how amazing children are.

"There are also implications for understanding language delay in children. When children don't learn to speak normally it can lead to serious issues later in life. For example, those who have it are more likely to suffer from mental illness or be unemployed later in life. If we can understand what is 'normal' as early as possible then we can intervene sooner to help those children."

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Menopause may be an unintended outcome of men's preference for younger mates

Singh, an evolutionary geneticist, backed by computer models developed by colleagues Jonathan Stone and Richard Morton, has determined that menopause is actually an unintended outcome of natural selection -- the result of its effects having become relaxed in older women.

Over time, human males have shown a preference for younger women in selecting mates, stacking the Darwinian deck against continued fertility in older women, the researchers have found.

"In a sense it is like aging, but it is different because it is an all-or-nothing process that has been accelerated because of preferential mating," says Singh, a professor in McMaster's Department of Biology whose research specialties include the evolution of human diversity.

Stone is an associate professor in the Department of Biology and associate director of McMaster's Origins Institute, whose themes include the origins of humanity, while Morton is a professor emeritus in Biology.

While conventional thinking has held that menopause prevents older women from continuing to reproduce, in fact, the researchers' new theory says it is the lack of reproduction that has given rise to menopause.

Their work appears in the online, open-access journal PLOS Computational Biology.

Menopause is believed to be unique to humans, but no one had yet been able to offer a satisfactory explanation for why it occurs, Singh says.

The prevailing "grandmother theory" holds that women have evolved to become infertile after a certain age to allow them to assist with rearing grandchildren, thus improving the survival of kin. Singh says that does not add up from an evolutionary perspective.

"How do you evolve infertility? It is contrary to the whole notion of natural selection. Natural selection selects for fertility, for reproduction -- not for stopping it," he says.

The new theory holds that, over time, competition among men of all ages for younger mates has left older females with much less chance of reproducing. The forces of natural selection, Singh says, are concerned only with the survival of the species through individual fitness, so they protect fertility in women while they are most likely to reproduce.

After that period, natural selection ceases to quell the genetic mutations that ultimately bring on menopause, leaving women not only infertile, but also vulnerable to a host of health problems.

"This theory says that natural selection doesn't have to do anything," Singh says. "If women were reproducing all along, and there were no preference against older women, women would be reproducing like men are for their whole lives."

The development of menopause, then, was not a change that improved the survival of the species, but one that merely recognized that fertility did not serve any ongoing purpose beyond a certain age.

For the vast majority of other animals, fertility continues until death, Singh explains, but women continue to live past their fertility because men remain fertile throughout their lives, and longevity is not inherited by gender.

Singh points out that if women had historically been the ones to select younger mates, the situation would have been reversed, with men losing fertility.

The consequence of menopause, however, is not only lost fertility for women, but an increased risk of illness and death that arises with hormonal changes that occur with menopause. Singh says a benefit of the new research could be to suggest that if menopause developed over time, that ultimately it could also be reversed.

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Wild cheetah accelerate fast and reach speeds of up to 58 miles per hour during a hunt

The results, from the team at the Royal Veterinary College's Structure & Motion Laboratory, are published June 13, 2013 in Nature.

To date, measurements of cheetah locomotion mechanics have only been made on captive animals chasing a lure in a straight line, with few studies eliciting speeds faster than racing greyhounds. For wild cheetahs, estimates of speed have only ever been made from direct observation or film, in open habitat and during daylight hours.

The team, led by Professor Wilson, developed a tracking collar equipped with a GPS module and electronic motion sensors (accelerometers, magnetometers, gyroscopes) capable of delivering processed position and velocity data and sensitive to the animal's movements. The collar was powered by a combination of solar cells, rechargeable and non-rechargeable batteries.

Collar software monitored the accelerometers to create activity summaries and detect the brief hunting events and adapted collar operation to battery voltages and time of day, meaning that researchers only captured data during a hunt. Overall, researchers recorded data from 367 runs by three female and two male adult cheetahs over 17 months. An episode of feeding after a run indicated hunting success, and was identified in the activity data by consistent, low-magnitude acceleration.

Data revealed that wild cheetah runs started with a period of acceleration, either from stationary or slow movement (presumably stalking) up to high speed. The cheetahs then decelerated and manoeuvred before prey capture. About one-third of runs involved more than one period of sustained acceleration. In successful hunts, there was often a burst of accelerometer data after the speed returned to zero, interpreted as the cheetah subduing the prey -- in this case mainly Impala, which made up 75% of their diet.

The average run distance was 173m. The longest runs recorded by each cheetah ranged from 407 to 559 m and the mean run frequency was 1.3 times per day, so, even if some hunts were missed, high speed locomotion only accounted for a small fraction of the 6,040-m average daily total distance covered by the cheetahs.

The team was also able to identify factors that make up a successful hunt. Successful hunts involved greater deceleration on average, but there was no significant difference in peak acceleration, distance travelled, number of turns, or total turn angle. This indicates that outcome was determined in the final stages of a hunt rather than hunts being abandoned early to save energy or reduce risk of injury, and the higher deceleration values may reflect actual prey capture.

The greatest acceleration and deceleration values were almost double values published for polo horses and exceeded the accelerations reported for greyhounds at the start of a race. The acceleration power for the cheetahs was four times higher than that achieved by Usain Bolt during his world record 100 metres run, about double that for racing greyhounds and more than three times higher than polo horses in competition.

Grip and manoeuvrability, rather than top speed, were shown to be key to hunting success. Hunts involved considerable manoeuvring, with maximum lateral (centripetal) accelerations often exceeding 13ms^-2 at speeds less than 17ms^-1 (polo horses achieve 6ms^-2).

Professor Alan Wilson, said: "Although the cheetah is recognised as the fastest land animal, very little is known about other aspects of its notable athleticism, particularly when hunting in the wild. Our technology allowed us to capture what to our knowledge is the first detailed locomotor information on the hunting dynamics of a large cursorial predator in its natural habitat and as a result we were able to record some of the highest measured values for lateral and forward acceleration, deceleration and body mass.

"In the future, equivalent data for other wild cursorial species would enhance what we know about natural speed, agility and endurance, and provide detailed information on ranging behaviour in the wild. For example, information on habitat selection by endangered species detailing where animals are commuting, hunting and resting would be informative when attempting to evaluate wildlife-protected areas."

The cheetahs used in this study were part of a continuing study by Botswana Predator Conservation Trust in the Okavango Delta region of Northern Botswana.

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2013年6月14日星期五

Mellanox adds Danish firm to buying spree

LONDON – Mellanox Technologies Ltd., a supplier of interconnect solutions for servers and storage systems, is set to buy privately held IPtronics A/S, a designer of optical interconnect components for $47.5 million in cash, subject to certain adjustments.

The deal has been unanimously approved by both companies and is expected to close in the second half of 2013, subject to certain closing conditions.

Mellanox (Sunnyvale, Calif.) said the deal is complimentary to the previously announced plan to acquire Kotura Inc. for about $82 million and would provide the company with analog transceiver technology to complete end-to-end 100-Gbit per second optical communications.

IPtronics (Roskilde, Denmark) offers multichannel vertical cavity surface-emitting laser (VCSEL) drivers, modulator drivers (MD) and transimpedance amplifiers (TIA) with lower power consumption, richer feature sets and lower costs compared to other solutions, said Mellanox.Iptronics' transmitters and receivers are already embedded in Mellanox's solutions allowing data center customers to operate in Web 2.0, cloud, data center, database, financial services and storage environments.

Mellanox expects to establish its first R&D center in Europe at Iptronics' current location in Roskilde, Denmark, and further expand its customer support presence within Europe.

Related links and articles:

www.mellanox.com

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Can you feel me now? New array measures vibrations across skin, may help engineers design tactile displays

June 14, 2013 — In the near future, a buzz in your belt or a pulse from your jacket may give you instructions on how to navigate your surroundings.

Think of it as tactile Morse code: vibrations from a wearable, GPS-linked device that tell you to turn right or left, or stop, depending on the pattern of pulses you feel. Such a device could free drivers from having to look at maps, and could also serve as a tactile guide for the visually and hearing impaired.

Lynette Jones, a senior research scientist in MIT's Department of Mechanical Engineering, designs wearable tactile displays. Through her work, she's observed that the skin is a sensitive -- though largely untapped -- medium for communication.

"If you compare the skin to the retina, you have about the same number of sensory receptors, you just have them over almost two square meters of space, unlike the eye where it's all concentrated in an extremely small area," Jones says. "The skin is generally as useful as a very acute area. It's just that you need to disperse the information that you're presenting."

Knowing just how to disperse tactile information across the skin is tricky. For instance, people may be much more sensitive to stimuli on areas like the hand, as opposed to the forearm, and may respond best to certain patterns of vibrations. Such information on skin responsiveness could help designers determine the best configuration of motors in a display, given where on the skin a device would be worn.

Now Jones has built an array that precisely tracks a motor's vibrations through skin in three dimensions. The array consists of eight miniature accelerometers and a single pancake motor -- a type of vibrating motor used in cellphones. She used the array to measure motor vibrations in three locations: the palm of the hand, the forearm and the thigh. From her studies with eight healthy participants, Jones found that a motor's mechanical vibrations through skin drop off quickly in all three locations, within 8 millimeters from where the vibrations originated.

Jones also gauged participants' perception of vibrations, fitting them with a 3-by-3 array of pancake motors in these three locations on the body. While skin generally stopped vibrating 8 millimeters from the source, most people continued to perceive the vibrations as far away as 24 millimeters.

When participants were asked to identify specific locations of motors within the array, they were much more sensitive on the palm than on the forearm or thigh. But in all three locations, people were better at picking out vibrations in the four corners of the array, versus the inner motors, leading Jones to posit that perhaps people use the edges of their limbs to localize vibrations and other stimuli.

"For a lot of sensory modalities, you have to work out what it is people can process, as one of the dictates for how you design," says Jones, whose results will appear in the journal IEEE Transactions on Haptics. "There's no point in making things much more compact, which may be a desirable feature from an engineering point of view, but from a human-use point of view, doesn't make a difference."

Mapping good vibrations

In addition to measuring skin's sensitivity to vibrations, Jones and co-author Katherine Sofia '12 found that skin has a strong effect on motor vibrations. The researchers compared a pancake motor's frequency of vibrations when mounted on a rigid structure or on more compliant skin. They found that in general, skin reduced a motor's vibrations by 28 percent, with the forearm and thigh having a slightly stronger dampening effect than the palm of the hand.

The skin's damping of motor vibrations is significant, Jones says, if engineers plan to build tactile displays that incorporate different frequencies of vibrations. For instance, the difference between two motors -- one slightly faster than the other -- may be indistinguishable in certain parts of the skin. Likewise, two motors spaced a certain distance apart may be differentiable in one area but not another.

"Should I have eight motors, or is four enough that 90 percent of the time, I'll know that when this one's on, it's this one and not that one?" Jones says. "We're answering those sorts of questions in the context of what information you want to present using a device."

Roberta Klatzky, a professor of psychology at Carnegie Mellon University, says that measurements taken by Jones' arrays can be used to set up displays in which the location of a stimulus -- for example, a pattern to convey a letter -- is important.

"A major challenge is to enable people to tell the difference between patterns applied to the skin as, for example, blind people do when reading Braille," says Klatzky, who specializes in the study of spatial cognition. "Lynette's work sets up a methodology and potential guidelines for effective pattern displays."

Creating a buzz

Jones sees promising applications for wearable tactile displays. In addition to helping drivers navigate, she says tactile stimuli may direct firefighters through burning buildings, or emergency workers through disaster sites. In more mundane scenarios, she says tactile displays may help joggers traverse an unfamiliar city, taking directions from a buzzing wristband, instead of having to look at a smartphone.

Using data from their mechanical and perceptual experiments, Jones' group is designing arrays that can be worn across the back and around the wrist, and is investigating various ways to present vibrations. For example, a row of vibrations activated sequentially from left to right may tell a driver to turn right; a single motor that buzzes with increasing frequency may be a warning to slow down.

"There's a lot of things you can do with these displays that are fairly intuitive in terms of how people respond," Jones says, "which is important because no one's going to spend hours and hours in any application, learning what a signal means."

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From the mouths of babes: The truth about toddler talk

Dr Cristina Dye, a lecturer in child language development, found that two to three- year-olds are using grammar far sooner than expected.

She studied fifty French speaking youngsters aged between 23 and 37 months, capturing tens of thousands of their utterances.

They found a clear, yet previously undetected, pattern of sounds and puffs of air, which consistently replaced grammatical words in many of the children's utterances.

Dr Dye said: "Many of the toddlers we studied made a small sound, a soft breath, or a pause, at exactly the place that a grammatical word would normally be uttered."

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Flare star WX UMa becomes 15 times brighter in less than 3 minutes

June 14, 2013 — Astrophysicists at the University of Santiago de Compostela (Spain) and the Byurakan Observatory (Armenia) have detected a star of low luminosity which within a matter of moments gave off a flare so strong that it became almost 15 times brighter. The star in question is the flare star WX UMa.

"We recorded a strong flare of the star WX UMa, which became almost 15 times brighter in a matter of 160 seconds," explains the astrophysicist Vakhtang Tamazian, professor at the University of Santiago de Compostela. The finding has been published in the journal Astrophysics.

This star is in the Ursa Major constellation, around 15.6 light years from Earth, and it forms part of a binary system. Its companion shines almost 100 times brighter, except at times such as that observed, in which the WX UMa gives off its flares. This can happen several times a year, but not as strongly as that which was recorded in this instance.

Dr Tamazian and other researchers detected this exceptional brightness from the Byurakan Observatory in Armenia. "Furthermore, during this period of less than three minutes the star underwent an abrupt change from spectral type M to B; in other words, it went from a temperature of 2,800 kelvin (K) to six or seven times more than that."

Based on their spectral absorption lines, stars are classified using letters. Type M stars have a surface temperature of between 2,000 and 3,700 K; Type B between 10,000 and 33,000 K.

WX UMa belongs to the limited group of "flare stars," a class of variable stars which exhibit increases in brightness of up to 100 factors or more within a matter of seconds or minutes. These increases are sudden and irregular, practically random, in fact. They then return to their normal state within tens of minutes.

Scientists do not know how this flaring arises, but they know how it develops: "For some reason a small focus of instability arises within the plasma of the star, which causes turbulence in its magnetic field," explains Tamazian. "A magnetic reconnection then occurs, a conversion of energy from the magnetic field into kinetic energy, in order to recover the stability of the flow, much like what happens in an electric discharge."

Next, kinetic energy in the plasma transforms into thermal energy in the upper layers of the atmosphere and the star's corona. This significant rise in the temperature and brightness of the star enables astronomers to detect changes in the radiation spectrum.

"Photometric and spectroscopic monitoring of this kind of flare stars is very relevant because it provides us with information about the changing states and physical processes, which are in turn key to studying the formation and evolution of stars," Tamazian explains.

Additionally, in cases of binary systems such as that which unites WX UMa with its companion, "observation of flares acquires a special importance, because we can investigate whether there is any relation between the frequency of flares and the position of the pair of stars on their orbit, a question which remains open."

To carry out this study, in which flares in other binary systems (HU Del, CM Dra and VW Com) have also been analysed, the SCORPIO camera of the Byurakan Astrophysical Observatory was used. This camera enables both the spectrum and the brightness of these objects to be detected.

Flare stars are intrinsically weak, and can therefore only be observed at relatively short distances in astronomic terms, specifically in the vicinity of the Sun, up to a distance of a few tens of light years.

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