Friday, May 28, 2010


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Ball lightnings are circular light phenomena occurring during thunderstorms and there are a large class of reports by eyewitnesses having experienced such events. Scientists have been puzzled by the nature of these apparent fire balls for a long time. Now physicists at the University of Innsbruck have calculated that the magnetic field of long lightning strokes may produce the image of luminous shapes, also known as phosphenes, in the brain. This finding may offer an explanation for many ball lightning observations.

Physicists Josef Peer and Alexander Kendl from the University of Innsbruck have studied electromagnetic fields of different types of lightning strokes occurring during thunderstorms. Their calculations suggest that the magnetic fields of a specific class of long lasting repetitive lightning discharges show the same properties as transcranial magnetic stimulation (TMS), a technique commonly used in clinical and psychiatric practice to stimulate neural activity in the human brain.

Time varying and sufficiently strong magnetic fields induce electrical fields in the brain, specifically, in neurons of the visual cortex, which may invoke phosphenes. “In the clinical application of TMS, luminous and apparently real visual perceptions in varying shapes and colors within the visual field of the patients and test persons are reported and well examined,” says Alexander Kendl. The Innsbruck physicists have now calculated that a near lightning stroke of long lasting thunderbolts may also generate these luminous visions, which are likely to appear as ball lightning. Their findings are published in the journal Physics Letters A.

Ball lightnings are rather rare events. The majority of researchers agree that different phenomena are likely to be summarized under the collective term “ball lightning”. Over time, various theories and propositions about the nature of these experiences have been suggested. Other researchers have produced luminous fire balls in the laboratory, which appeared not completely unlike ball lightning and could explain some of the observations but were mostly too short lived. Other plausible explanations for some of observations are St. Elmo's fire, luminous dust balls or small molten balls of metal.

In which cases then, can a lightning bolt invoke a ball-shaped phosphene? “Lightning strokes with repetitive discharges producing stimulating magnetic fields over a period of a few seconds are rather rare and only occur in about one in one hundred events,“ reports physicist Kendl. “An observer located within few hundred metres of a long lightning stroke may experience a magnetic phosphene in the shape of a luminous spot.“ Also other sensations, such as noises or smells, may be induced. Since the term “ball lightning” is well known from media reports, observers are likely to classify lightning phosphenes as such.

Alexander Kendl’s hypothesis that in fact the majority of ball lightning observations are phosphenes is strongly supported by its simplicity: “Contrary to other theories describing floating fire balls, no new and other suppositions are necessary.”

(Photo: Uni Innsbruck)

University of Innsbruck


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Swimsuit season is almost upon us. For most of us, the countdown has begun to lazy days lounging by the pool and relaxing on the beach. However, for some of us, the focus is not so much on sunglasses and beach balls, but how to quickly shed those final five or ten pounds in order to look good poolside. It is no secret that dieting can be challenging and food cravings can make it even more difficult. Why do we get intense desires to eat certain foods? Although food cravings are a common experience, researchers have only recently begun studying how food cravings emerge.

Psychological scientists Eva Kemps and Marika Tiggemann of Flinders University, Australia, review the latest research on food cravings and how they may be controlled in the current issue of Current Directions in Psychological Science, a journal of the Association for Psychological Science.

We've all experienced hunger (where eating anything will suffice), but what makes food cravings different from hunger is how specific they are. We don't just want to eat something; instead, we want barbecue potato chips or cookie dough ice cream. Many of us experience food cravings from time to time, but for certain individuals, these cravings can pose serious health risks. For example, food cravings have been shown to elicit binge-eating episodes, which can lead to obesity and eating disorders. In addition, giving in to food cravings can trigger feelings of guilt and shame.

Where do food cravings come from? Many research studies suggest that mental imagery may be a key component of food cravings — when people crave a specific food, they have vivid images of that food. Results of one study showed that the strength of participants' cravings was linked to how vividly they imagined the food. Mental imagery (imagining food or anything else) takes up cognitive resources, or brain power. Studies have shown that when subjects are imagining something, they have a hard time completing various cognitive tasks. In one experiment, volunteers who were craving chocolate recalled fewer words and took longer to solve math problems than volunteers who were not craving chocolate. These links between food cravings and mental imagery, along with the findings that mental imagery takes up cognitive resources, may help to explain why food cravings can be so disruptive: As we are imagining a specific food, much of our brain power is focused on that food, and we have a hard time with other tasks.

New research findings suggest that that this relationship may work in the opposite direction as well: It may be possible to use cognitive tasks to reduce food cravings. The results of one experiment revealed that volunteers who had been craving a food reported reduced food cravings after they formed images of common sights (for example, they were asked to imagine the appearance of a rainbow) or smells (they were asked to imagine the smell of eucalyptus). In another experiment, volunteers who were craving a food watched a flickering pattern of black and white dots on a monitor (similar to an untuned television set). After viewing the pattern, they reported a decrease in the vividness of their craved-food images as well as a reduction in their cravings. According the researchers, these findings indicate that "engaging in a simple visual task seems to hold real promise as a method for curbing food cravings." The authors suggest that "real-world implementations could incorporate the dynamic visual noise display into existing accessible technologies, such as the smart phone and other mobile, hand-held computing devices." They conclude that these experimental approaches may extend beyond food cravings and have implications for reducing cravings of other substances such as drugs and alcohol.

The Association for Psychological Science


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Fish become feisty but fearful when facing themselves in a mirror, according to two Stanford biologists.

"It seems like something they don't understand," said Julie Desjardins, a post-doctoral researcher in biology and lead author of a paper to be published in Biology Letters describing the study. The paper is available online now. "I think this stimulus is just so far outside their realm of experience that it results in this somewhat emotional response."

Desjardins and coauthor Russell Fernald, professor of biology, arrived at their conclusion by comparing the behavior and brain activity of male African cichlid fish during and after one-on-one encounters with either a mirror or other another male of about the same size.

Cichlids grow to several inches in length and territorial males typically have bright blue or yellow body coloration.

Territorial male cichlids usually react to another male by trying to fight with it in a sort of tit-for-tat manner. Desjardins suspects the fish fighting their own reflections become fearful because their enemy in the mirror doesn't exhibit the usual reactions they would expect from another fish.

"In normal fights, they bite at each other, one after the other, and will do all kinds of movements and posturing, but it is always slightly off or even alternating in timing," Desjardins said. "But when you are fighting with a mirror, your opponent is perfectly in time. So the subject fish really is not seeing any sort of reciprocal response from their opponent."

The discovery that fish can discern a difference so subtle could prompt researchers to take a second look at how well other lower invertebrates can discriminate among various situations.

Desjardins and Fernald arranged 20-minute long sparing sessions for their fish. A clear wall across the middle of the tank kept the combatants apart when two fish were pitted against each other, so there was never any actual fish-to-fish contact. The fish invariably tried to fight with their foe – real or reflected – and their behavior during the dust-ups appeared consistent whether they were mirror-boxing or not.

When the researchers performed post-mayhem postmortems on the fish, they found that the levels of testosterone and another hormone associated with aggression circulating in the cichlids' bloodstreams were comparable regardless of whether the foe was a reflection or flesh.

But in dissecting a part of the fishes' brain called the amygdala, they found evidence of substantially more activity in that region in the mirror-fighting fish than in those tussling with real foes.

"The amygdala is a part of the brain that has been associated with fear and fear conditioning, not only in fish, but across all vertebrates," Desjardins said. So the fish appeared to feel an element of fear when confronted by an opponent whose behavior was off-kilter.

Although higher vertebrates such as humans have very elaborate amygdalas by comparison with fish, there is still a part of the more complex amygdalas that is analogous to what fish have and performs similar functions.

"The fact that we saw evidence of a really high level of activity in the amygdala, is pretty exciting," Desjardins said. "And surprising."

"I thought I might see a difference in the behavior and when I didn't see that, I was pretty skeptical that I would see anything different in the brain," she said.

But she thinks what they found is evidence of a negative emotional response and offered what she emphasized is a speculative comparison. Perhaps it is "like when you are a little kid and someone keeps repeating back to you what you have just said, that quickly becomes irritating and frustrating," she said. "If I was going to make that giant leap between humans and fish, it could be similar."

So what does this tell us about a fish's level of consciousness?

"It's difficult to say," she said. "But I think it certainly indicates that there is more going on cognitively than people have long assumed in most lower invertebrates."

Desjardins said many researchers who study the cognitive capabilities of lower vertebrates such as frogs, lizards and birds look at behavior and hormones, but rarely look at the brain.

"I think there is a lot that could be done with these types of techniques that has not been done in the past," she said. "This opens the door for us to better understand what is going on in the brain of non-mammalian animals."

(Photo: Todd Anderson/Stanford University)

Stanford University


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The world's biggest investigation on possible links between cell phone use and brain tumours is inconclusive, according to a Canadian scientist who collaborated on the Interphone International Study Group.

Jack Siemiatycki, a professor at the University of Montreal and an epidemiologist at the University of Montreal Hospital Research Center, says restricted access to participants compromised the validity of results of the study published in the May 18 International Journal of Epidemiology. "The findings of the Interphone Study are ambiguous, surprising and puzzling," he says.

The Interphone International Study Group, which examined whether cellular radio frequencies could be correlated to brain tumours, was coordinated by the International Agency for Research on Cancer. The investigation was led by 21 epidemiologists from Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden and the United Kingdom. Over 10,000 people took part in the study: cell phone users; non cell phone users; cell phone users who survived brain cancer as well as brain cancer survivors who had never used cell phones.

"If we combine all users and compare them with non-users, the Interphone Study found no increase in brain cancer among users. In fact, surprisingly, we found that when we combine users independently of the amount of use, they had lower brain cancer risks than non-users," says Dr. Siemiatycki, who teaches in the University of Montreal Faculty of Medicine. "However, the study also found heavy users of cell phones appeared to be at a higher risk of brain tumours than non-users."

Why the discrepancy? Simply put, scientists are unsure. Attention has focused on the methodology of the study and, in particular, on the representativeness of the study subjects who participated. With participation rates in the range of 50 percent to 60 percent of eligible subjects, it is possible that the participants did not provide an accurate portrait of cell phone usage among cancer cases and among healthy control subjects. Dr. Siemiatycki argues this problem arose because of constraints imposed on researchers by ethics committees intended to protect potential research subjects.

"Ethics reviews are now so rigid that scientists from Canada, the United States and Europe are losing the kind of access to medical databases and to study subjects that is needed to conduct studies such as this one. Ethics committees increasingly require that researchers work through treating physicians, professionals who are already overworked, to recruit their patients. This may work for clinical research exploring treatment of cancer, in which physicians often have a professional or personal interest, but it does not work for investigations into the causes of cancer. This flawed system can produce biased study results."

Despite the inconclusive results of the Interphone Study, consumers should not panic about possible risks related to cell phones, stresses Dr. Siemiatycki. "If there are risks, they are probably pretty small. Should anyone be concerned about potential dangers of cell phones, they can remedy the issue by using hands-free devices and avoid exposure to radio frequencies around their head."

(Photo: IStock)

University of Montreal


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One way that geologists try to decipher how cells functioned as far back as 3 billion years is by studying modern microbial mats, or gooey layers of nutrient-exchanging bacteria that grow mostly on moist surfaces and collect dirt and minerals that crystallize over time. Eventually, the bacteria turn to stone just beneath the crystallized material, thereby recording their history within the crystalline skeletons. Known as stromatolites, the layered rock formations are considered to be the oldest fossils on Earth.

Deciphering the few clues about ancient bacterial life that are seen in these poorly preserved rocks has been difficult, but researchers from MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS) and the Russian Academy of Sciences may have found a way to glean new information from the fossils. Specifically, they have linked the even spacing between the thousands of tiny cones that dot the surfaces of stromatolite-forming microbial mats — a pattern that also appears in cross-sectional slices of stromatolites that are 2.8 billion years old — to photosynthesis.

In a paper published in the Proceedings of the National Academy of Science, the researchers suggest that the characteristic centimeter-scale spacing between neighboring cones that appears on modern microbial mats and the conical stromatolites they form occurs as a result of the daily competition for nutrients between neighboring mats.

In addition to helping scientists put a better range on when photosynthesis started, the research provides a new technique for interpreting the patterns of these ancient fossils. By analyzing the length of the triangular patterns seen in an ancient stromatolite, for example, geologists can now infer more details about the environment in which the microbial mat lived, such as whether it lived in still or turbulent water.

Until now, no one had explored the consistent one-centimeter spacing that appears between the tiny cones featured on microbial mats and conical stromatolites that grow in the hot springs of Yellowstone National Park, and at other locations around the world. Lead author and EAPS graduate student Alexander Petroff and EAPS professors Daniel Rothman and Tanja Bosak proposed that the pattern was not coincidental and could pertain to a biophysical process, such as how the bacteria compete for nutrients.

By studying the physics of photosynthesis, the researchers formed a better understanding of how a mat consumes nutrients from its surroundings over the course of a day, and then metabolizes, or breaks down, those nutrients for energy.

During the daytime, a mat takes in nutrients like inorganic carbon from its immediate surroundings and uses energy from sunlight to build sugars and new bacteria. As these nutrients become locally depleted, the mat starts to consume nutrients from larger distances. At nighttime when it is dark and photosynthesis is not possible, nutrients return to the water immediately surrounding the mat.

The researchers reasoned that in order to avoid direct competition for nutrients, the spacing between mats must be influenced by diffusion, or how molecules spread out over time. In this case, diffusion is itself influenced by the amount of time a mat is metabolically active, which varies over the course of a day due to changes in sunlight. Therefore, the spacing between cones records the maximum distance that mats can compete with one another to metabolize nutrients that are spread by diffusion and later replenished at night. After testing this theory on cultures in the lab, the researchers confirmed their hypothesis through fieldwork in Yellowstone, where the centimeter spacing between mats corresponds to their metabolic period of about 20 hours.

That the spacing pattern corresponds to the mats' metabolic period — and is also seen in ancient rocks — shows that the same basic physical processes of diffusion and competition seen today were happening billions of years ago, long before complex life appeared. Petroff and his colleagues are currently researching why biological stromatolites form cones instead of other shapes.



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Most venomous snakes are legendary for their lethal bites, but not all. Some spit defensively. Bruce Young, from the University of Massachusetts Lowell, explains that some cobras defend themselves by spraying debilitating venom into the eyes of an aggressor.

Getting the chance to work with spitting cobras in South Africa, Young took the opportunity to record the venom spray tracks aimed at his eyes. Protected by a sheet of Perspex, Young caught the trails of venom and two things struck him: how accurately the snakes aimed and that each track was unique. This puzzled Young. For a start the cobra's fangs are fixed and they can't change the size of the venom orifice, 'so basic fluid dynamics would lead you to think that the pattern of the fluid should be fixed,' explains Young. But Young had also noticed that the snakes 'wiggled' their heads just before letting fly. 'The question became how do we reconcile those two things,' says Young, who publishes his discovery that the snakes initially track their victim's movement and then switch to predicting where the victim is going to be 200ms in the future in the Journal of Experimental Biology ( on 14 May 2010.

Young remembers that Guido Westhoff had also noticed the spitting cobra's 'head wiggle', so he and his research assistant, Melissa Boetig, travelled to Horst Bleckmann's lab in the University of Bonn, Germany, to find out how spitting cobras fine-tune their venom spray. The team had to find out how a target provokes a cobra to spit, and Young was the man for that job, 'I just put on the goggles and the cobras start spitting all over,' laughs Young.

Wearing a visor fitted with accelerometers to track his own head movements while Boetig and Westhoff filmed the cobra's movements at 500 frames/s, Young stood in front of the animals and taunted them by weaving his head about. Over a period of 6 weeks, the team filmed over 100 spits before trying to discover why Young was so successful at provoking the snakes.

Analysing Young's movements, only one thing stood out; 200 ms before the snake spat, Young suddenly jerked his head. The team realised that Young's head jerk was the spitting trigger. They reasoned that the snake must be tracking Young's movements right up to the instant that he jerked his head and that it took a further 200 ms for the snake to react and fire off the venom.

But Young was still moving after triggering the snake into spitting and the snake can't steer the stream of venom, so how was the cobra able to successfully hit Young's eyes if it was aiming at a point where the target had been 200 ms previously? Realigning the data to the instant when Young jerked his head, the team compared all of the snakes' head movements and noticed that the cobras were all moving in a similar way. They accelerated their heads in the same direction that Young's eyes were moving. 'Not only does it speed up but it predicts where I am going to be and then it patterns its venom in that area,' explains Young.

So spitting cobras defend themselves by initially tracking an aggressor's movements. However, at the instant that an attacker triggers the cobra into spitting, the reptile switches to predicting where the attacker's eyes will be 200 ms in the future and aims there to be sure that it hits its target.

The Company of Biologists




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