When astronomers refer to the temperature of a star, they are talking about the temperature of the gases in the photosphere, and they express those temperatures on the Kelvin temperature scale. On this scale, zero degrees Kelvin (written 0 K) is absolute (-273.2°C or -459.7°F), the temperature at which an object contains no thermal energy that can be extracted. Water freezes at 273 K and boils at 373 K (at sea-level atmospheric pressure). The Kelvin temperature scale is useful in astronomy because it is based on absolute zero and consequently is related directly to the motion of the particles in an object.
Now you can understand why a hot object glows, or to put it another way, why a hot object emits photons, bundles of electromagnetic energy. The hotter an object is, the more motion there is among its particles. The agitated particles, including electrons, collide with each other, and when electrons accelerate—change their motion—part of the energy is carried away as electromagnetic radiation. The radiation emitted by a heated object is called black-body radiation, a name translated from a German term that refers to the way a perfectly opaque object would behave. A perfectly opaque object would be both a perfectly efficient absorber and a perfectly efficient emitter of radiation. At room temperature, such a perfect absorber and emitter would look black, but at higher temperatures it would glow at wavelengths visible to a human eye. That explains why in astronomy and physics contexts you will see the term black-body referring to objects that glow brightly.
Black-body radiation is quite common. In fact, it is responsible for the light emitted by an incandescent light bulb. Electricity flowing through the filament of the bulb heats it to high temperature, and it glows. You can also recognize the light emitted by hot lava as black-body radiation. Many objects in the sky, including the sun and other stars, primarily emit black-body radiation because they are mostly opaque.
Gif credit: caucasianmale
If bats ever used a cell phone, they could forgo the version with caller ID: The mammals can identify each other by their voices, a new study says.
Bats aren’t the only mammals to use voice recognition—people do it, too. Even in the days before caller ID, a simple “Hi, it’s me,” from a close friend or loved one was usually enough to figure out who’s on the other end. Recognizing a person by voice, however, requires previous knowledge: We can’t identify a stranger on the phone by voice alone because we have never met them before.
People can, however, discriminate between a familiar voice and an unfamiliar one, even if they’ve never met the other person. We can also distinguish between two individuals by voice alone even if we’ve never met them before.
Hanna Kastein and colleagues at the University of Veterinary Medicine in Hannover, Germany, wanted to know whether bats could perform these same tasks.
“Bats are totally interesting mammals to study voice perception since they are dependent on their vocalizations for orientation and communication due to their nocturnal lifestyle. In addition, they are socially living animals that frequently communicate acoustically with other members of their species,” Kastein said.
Besides their social lifestyles, bats and people share a number of physical characteristics. Both produce sounds using a combination of the larynx, vocal cords, and nasal cavities. These structures work together with an animal’s physical makeup to produce an individual’s unique voice.
“In stressful situations, voices become higher pitched, or ‘squeaky,’ in bats as in humans. Also, each individual bat has a slightly different morphology, and thus its voice sounds different from any other individual, just as voices in humans differ individually,” Kastein said.
You Had Me at Hello
Kastein and colleagues wanted to know whether bats could use vocal calls to identify individuals with which they shared a roost, and whether they could use these same calls to distinguish between two different individuals.
The researchers worked with the greater false vampire bat (Megaderma lyra) because the species has a rich array of calls that it uses in several contexts.
The team observed two groups of bats kept in separate artificial roosts for two months. They hypothesized that bats that had the most body contact while roosting would form the closest relationships. Kastein and colleagues then recorded various vocal calls from both groups of bats.
When Kastein played the recording of a vocal call over a loudspeaker, bats in both roosts universally turned their heads toward the speaker regardless of whether the call was from a bat with which they had close body contact, a bat from the same roost, or a bat from the other roost.
Given that the artificial roosts had much lower rates of vocal calls, due to the lack of stimuli, the researchers thought that this response could be due to the novelty of hearing any type of vocalization.
So the team did a second set of experiments in which they had a bat listen to the call of their “friend” until the call didn’t create any type of behavioral response, such as turning the head. This means the listening bat had become habituated to the call, according to the study, published recently in the journal Animal Cognition.
Then, the scientists alternated playing a vocalization of the bat friend with that of an unfamiliar bat. The listening bats were significantly more likely to turn their heads toward the call of their friend—indicating both that they recognized their friend and that they could distinguish between individual vocalizations.
“In our study, we found that the … false vampire bat is able to discriminate between different voices, including both known or unknown individuals,” Kastein noted.
“However, to what extent bats are able to label an unknown bat as unknown, we cannot say.” She suspects that in real life, recognizing other bats by their voices is aided by smell and, to a lesser extent, vision.
The Earliest Days of NASA
Maria Popova, at Brain Pickings, happened upon a treasure trove of early NASA (and its airplane-only predecessor NACA) archive photos. They are really something. From biplanes to the Mercury capsule, pre-1950 aeronautics seemed to live by the motto of “If we build it, then we can go there.” That’s a sentiment we could use a bit more of.
The world’s most powerful artificial tornado is part of the Mercedes-Benz Museum in Stuttgart, Germany. Though popular enough with visitors that the staff will bring out smoke generators to make it visible, the tornado was not built as an attraction - It’s actually part of the building’s fire protection system. The modern open design of the museum meant that conventional smoke removal systems were inadequate. Instead vorticity is generated in the central lobby with 144 wall-mounted jets. The angular velocity created by the jets is strongest at the middle, in the vortex core, due to conservation of angular momentum - exactly the way a spinning ice skater speeds up by pulling his arms in. The core of the vortex is a low pressure area, which draws outside air toward it - this is how the tornado pulls in smoke when there is a fire. The fan on the ceiling provides the pressure draw necessary for the smoke to be pulled up and out of the building at a supposed rate of 4 tons per minute. See the tornado in action here. (Photo credit: Mercedes-Benz Passion; submitted by Ivan)
Einstein and Eddington (2008)
A tv movie about the lives of these two men against the background of WW1 and the beginning of the theory of relativity.
I have seen it recently. A very good film ! A fine performance by David Tennant as Arthur Eddington and Andy Serkis (Gollum, King Kong) plays a lively Einstein.
Stress Makes Glass Stronger
Alterations to the usual glass production process, such as putting the material under stress, can introduce effects that linger even after the material hardens. While manufacturers have long exploited this phenomenon to strengthen glass, a new theory aims to get closer to understanding why it happens.
Glass is not as well understood as most materials, because it straddles the line between liquid and solid. In typical crystalline materials, molecules assemble into a set structure over the span of the entire material as the substance solidifies from a disordered liquid form. Glass, on the other hand, retains a liquid-like disorder even after it hardens.
Read more: http://www.laboratoryequipment.com/news/2013/05/stress-makes-glass-stronger
As suicide rates climb steeply in the US a growing number of psychiatrists are arguing that suicidal behaviour should be considered as a disease in its own right, rather than as a behaviour resulting from a mood disorder.
They base their argument on mounting evidence showing that the brains of people who have committed suicide have striking similarities, quite distinct from what is seen in the brains of people who have similar mood disorders but who died of natural causes.
Suicide also tends to be more common in some families, suggesting there may be genetic and other biological factors in play. What’s more, most people with mood disorders never attempt to kill themselves, and about 10 per cent of suicides have no history of mental disease.
The idea of classifying suicidal tendencies as a disease is being taken seriously. The team behind the fifth edition of the Diagnostic Standards Manual (DSM-5) – the newest version of psychiatry’s “bible”, released at the American Psychiatric Association’s meeting in San Francisco this week – considered a proposal to have “suicide behaviour disorder” listed as a distinct diagnosis. It was ultimately put on probation: put into a list of topics deemed to require further research for possible inclusion in future DSM revisions.
Another argument for linking suicidal people together under a single diagnosis is that it could spur research into the neurological and genetic factors they have in common. This could allow psychiatrists to better predict someone’s suicide risk, and even lead to treatments that stop suicidal feelings.
Signs in the brain
Until the 1980s, the accepted view in psychiatry was that people who committed suicide were, by definition, depressed. But that view began to change when autopsies revealed distinctive features in the brains of people who had committed suicide, including structural changes in the prefrontal cortex – which controls high-level decision-making – and altered levels of the neurochemical serotonin. These characteristics appeared regardless of whether the people had suffered from depression, schizophrenia, bipolar disorder, or no disorder at all (Brain Research).
But there is no single neurological cause of suicide, says Gustavo Turecki of McGill University in Montreal. What is more likely, he says, is that environmental factors trigger a series of changes in the brains of people who are already genetically prone to suicide, contributing to a constellation of factors that ultimately increase risk. These factors include a history of abuse as a child, post-traumatic stress disorder, long periods of anxiety, or sleep deprivation.
The search for more of these factors is complicated by the rarity of brain samples from suicide victims and the lack of an animal model – humans are unique in their wilful ability to end their lives. But some studies are yielding insights. For example, when people with bipolar disorder who have previously attempted suicide begin taking lithium, they tend to stop attempting suicide even if the drug has no effect on their other symptoms. This suggests that the drug may be acting on neural pathways that specifically influence suicidal tendencies (Annual Review of Pharmacology and Toxicology).
In the genes?
There is also growing evidence that genetics plays a role. For example, according to one study, identical twins share suicidal tendencies 15 per cent of the time, compared with 1 per cent in non-identical twins (Journal of Affective Disorders). And a study of adopted people who had committed suicide found that their biological relatives were six times more likely to commit suicide than members of the family that adopted them (American Journal of Medical Genetics).
A number of individual genes have been linked to suicide, such as those involved in the brain’s response to mood-lifting serotonin, and a signalling molecule called brain-derived neurotrophic factor (BDNF), which regulates the brain’s response to stress. Both tend to be suppressed in the brains of people who committed suicide, regardless of what mental disorder they had. Other studies of post-mortem brains have found that people who commit suicide after a bout of depression have different brain chemistry from depressed people who die of natural causes.
A study by Turecki, published this month, compared the brains of 46 people who had committed suicide with those of 16 people who died of natural causes. In the first group, 366 genes, mostly related to learning and memory, had a different set of epigenetic markers – chemical switches that turn genes on and off (American Journal of Psychiatry). The results are complicated by the fact that many of the people who committed suicide suffered from mental disorders, but Turecki says that suicide, rather than having a mental disorder, was the only significant predictor for these specific epigenetic changes.
No one yet knows the mechanism through which environmental factors would alter these genes, although stress hormones such as cortisol may be playing a role.
Ultimately, biological and genetic markers might allow psychiatrists to better predict which patients are most at risk of suicide. But David Brent of the University of Pittsburgh, Pennsylvania, cautions that even if we can one day use biomarkers to predict if someone will make a suicide attempt, they do not tell us when. “If clinicians are keeping an eye on a patient, they need to know if there’s imminent risk,” he says.
However, knowing someone’s long-term suicide risk may have important implications for how a doctor chooses to treat that person, says Jan Fawcett of the University of New Mexico in Albuquerque.
For instance, a doctor may decide not to prescribe certain antidepressants to a patient with these biomarkers, as many drugs are thought to increase suicide risk. Another question would be whether to commit a person to a mental hospital – a major decision, he says, as people are most likely to commit suicide right after being released from hospital (Archives of General Psychiatry).
David Shaffer of Columbia University in New York, who was a member of the DSM-V working group, says that suicide behaviour disorder is “very much in the spirit” of the new Research Domain Criteria system that the US National Institute of Mental Health proposed as an alternative diagnosis standard to DSM-V. Rather than diagnosing people with depression or bipolar disorder, for example, the NIMH wants mental disorders to be diagnosed and treated more objectively using patients’ behaviour, genetics and neurobiology.
Ultimately, says Nader Perroud of the University of Geneva in Switzerland, if suicidal behaviour is considered as a disease in its own right, it will become possible to conduct more focused, evidence-based research on it and medications that treat it effectively. “We might be able to find a proper treatment for suicidal behaviour.”
The extraordinary Treasure of El Carambolo, which was found in El Carambolo, Spain, 1958 during renovations being made at a pigeon shooting society. The hoard was thought to be buried in the 6th century BCE.
The discovery of the Treasure of El Carambolo sparked interest in the Tartessos culture, though it is still under debate whether these treasures were a product of local culture, or of the Phoenicians.
Courtesy & currently located at the Archaeological Museum of Seville, Spain. Photos taken by José Luiz Bernardes Ribeiro.
This little company from Kenya makes toys from slippers that wash up on the beach.
Pictures by Ben Curtis
The company’s name is Ocean Sole: http://www.ocean-sole.com/
This is a photograph released by the U.S. government in 1960 that shows the Little Boy atom bomb, the type detonated over Hiroshima on Aug. 6, 1945. The bomb was 29 inches in diameter, 126 inches long and weighed 9,700 pounds with a yield equivalent to 20,000 tons of TNT explosive.
Mirjana Filipovic is still haunted by the land mine blast that killed her boyfriend and blew off her left leg while on a fishing trip nearly a decade ago. It happened in a field that was supposedly de-mined.
Now, unlikely heroes may be coming to the rescue to prevent similar tragedies:…