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Eye See You: Moving Retina in Jumping Spiders

⦿ Jumping spiders (Salticidae) don't use a web to catch prey. Instead they locate, stalk and mount a jumping ambush when they are 1-2 cm away. To do this, they need to detect and then evaluate objects so they don't confuse a potential mate as prey! Fortunately, jumping spiders have among the sharpest vision among invertebrates.

⦿ Unlike insects, spiders don't have compound eyes. Instead their 8 "simple" eyes point forward (for high focus) and sideways (to detect motion). Strategically, this is similar to the division of labor in our eyes: we detect peripheral vision at the edges of our retina with low resolution but wide field of view, and sharp images at the fovea in the center of the retina, which is packed with a high density of vision receptors, but has a limited field of view. Since the spider's large central eyes are set close together and have a limited field of view, they must be moved to point the fovea towards the object. How do they do this?

⦿ Involuntary leg movements are triggered by stimuli from the lateral eyes to reposition the body. However, the spider cannot swivel its whole eyeball as we do, because the lens is built into the carapace, or outer skeleton. Instead, a set of six muscles moves the retina: up and down, sideways and rotationally, while the lens stays fixed. In a transparent spider, you can see the unusual movements of the retina in the tube-like principle eyes. Just one more addition to the cuteness quotient of these tiny spiders! 

REF: M.F. Land (1969) Movements of the retinae of jumping spiders (Salticidae: Dendryphantinae) in response to visual stimuli. http://jeb.biologists.org/content/jexbio/51/2/471.full.pdf

Video Source: Yellow amycine jumping spider from Ecuador, https://www.youtube.com/watch?v=gvN_ex95IcE

GIF Source: http://gph.is/1n7n4aR
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Owl Be Seeing You

It's time for the #SuperbOwl and #ScienceSunday

Did you know that the eyes of an owl are 5% of its body weight? Imagine Peyton Manning with eyes the size of a baseball.. errr...football. Their large pupils dilate at night, harvesting more light to be captured by an abundance of rods, specialized for night vision. Their eyes don't have as many cone cells as we do, so their color vision is not that great. But they can see up to 100 times better than the Broncos at night! 

How does the owl rotate its head without wringing its neck? An owl has twice as many vertebrae compared to the 7 in humans, giving it a 270 degree flexibility, without tearing the delicate blood vessels in their necks and heads, and cutting off blood supply to their brains.. That's because unlike human vertebrae, the vertebrae of the owl have large cavities, about ten times the diameter of the vertebral artery that goes through, allowing for plenty of slack. The artery also enters the cervical vertebrae at a higher point, for more freedom of movement. It is heavily networked so that blood supply to the brain and eyes is not interrupted by twisting of the neck even if one route is blocked. Astonishingly, the blood vessels at the neck became wider as they branched, in contrast to that of mere humans, where they get smaller and narrower. 

Read More: http://goo.gl/hFUq2 Research by +Michael Habib  and colleagues at Johns Hopkins University on the mystery of the Owl's neck. This award winning study was featured in Science magazine and may be the first use of angiography, CT scans and medical illustrations to unravel the mystery of the magnificent owl. 

For +rare avis  who wanted to know about the #SuperbOwl :)
Image Source: Northern Hawk Owls  https://vimeo.com/17355313
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The Flight of the Hummingbird

A route of evanescence
With a revolving wheel
A resonance of emerald,
A rush of cochineal

With these words, the poet Emily Dickinson summed up the fleeting magic of the hummingbird.  

Hummingbirds are the only vertebrates capable of hovering in place. In addition to flying forwards, they can also fly backward and upside down! They are tiny: the smallest bee hummingbird of Cuba weighs less than 2 grams, less than a penny! Add to this their speed- they can clock up to 45 mph, and stamina- they can fly 18 straight hours, and you may appreciate their unusual metabolism. In fact, they have the highest metabolic rate of any warm blooded animal. 

With a heart beat of 1,200/min and wing beat of 200/sec during flight, hummingbirds generate a tremendous amount of heat. Because their muscles are only ~10% efficient, much of the energy they consume is released as heat. But their thick plumage of feathers keeps in the heat: useful when the bird wants to conserve body heat, but a problem during flight. 

Using infrared thermal photography, scientists have found that hummingbirds (and probably most birds) lose body heat from three areas seen as bright white spots in the gif below: the region around the eyes, at the shoulder where the wings meet the body, and the feet, which they can dangle downward to dissipate even more heat. 

Ref: http://rsos.royalsocietypublishing.org/content/2/12/150598
Video: https://www.youtube.com/watch?v=btuu_hDU7B4
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I am really worried about priorities..

❖ On a recent science post about the evolution of land plants, a community member worried: "what about poverty?? people are dying in hunger, lack of medical support, clean water and other simple things which can be fixed... but without fixing something for them we are trying to find water in Mars. I'm really worried about the priorities.."

❖ A similar comment lamented the cost of curiosity in the search for earth-like planets (http://goo.gl/9OUM0D). Physics professor Robert McNees had an awesome response:

❝ You posted your comment using technology that exists only because of a chain of discoveries and insights that began with fascination-driven research in the late 19th century.❞

❝ If Balmer hadn't studied spectral lines, Planck may not have proposed the quantum. Then Bohr may not have conceived his model of the atom, which means Heisenberg and Schrödinger wouldn't have developed their formulations of quantum mechanics. That would have left Bloch without the tools he needed to understand the nature of conduction in metals, and then how would Schottky have figured out semiconductors? It's hard to imagine, then, how Bardeen, Brattain, and Schockley would have developed transistors. And without transistors, Noyce and Kilbey couldn't have produced integrated circuits.❞

❝ Almost every major technological advance of the 20th and 21st centuries originated with basic research that presented no obvious or immediate economic benefit. That means no profit motive, and hence no reason for the private sector to adequately fund it. Basic research isn't a waste of tax dollars; it's a more reliable long-term investment than anything else in the Federal government's portfolio.❞

GIF: Johns Hopkins professor Andy Feinberg spent several days on NASA's zero gravity aircraft (known as "vomit comet") trying out different pipetting techniques for future experiments in space. It wasn't that easy with flying pipet tips and tubes! Andy did eventually figure out the best technique (using positive displacement pipets, seen in the second video in this link http://goo.gl/AFpnJq). Feinberg is leading one of ten experiments in NASA's Twin Study to examine epigenetics and other biological changes that affect astronauts in space. Samples from Scott Kelly, who is spending a year onboard the ISS, will be compared with those from his twin on earth, Mark. Feinberg credits NASA for funding this study. He says, “They're very curious people. They really want to know.”

Who knows, one day we may even grow potatoes on Mars! :)

Share your favorite example of the unexpected benefits of basic research! 

Shout out to +Gnotic Pasta  who made the GIF. Thanks, Dan! 
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Inferring from Infrared

Imagine if there was a way to know which watermelon is sweeter? When is that avocado going to ripen? How many calories, carbs or protein is in that shake? How your plants are doing? What's in those pills your taking? A new low-cost handheld sensor on the market promises all those answers and more, in real time (https://www.consumerphysics.com/myscio/scio). The technology is based on near infrared spectroscopy. How does it work?

Calorific Rays: We all know that a prism can separate ordinary light into the vibrant colors of the rainbow. Back in 1800, musician and astronomer William Herschel wanted to know the temperature of each color. By placing a thermometer with a blackened bulb along the spectrum, he discovered that the red end was warmer than the blue. To his surprise, a thermometer placed just beyond the visible red part of the spectrum was even warmer. He had discovered infrared rays, although he didn't realize it at the time. This is the same heat that you feel when you hold your hand near a fire.

Bond. Covalent Bond. Shaken and Stirred: Chemicals are arrangements of atoms, held together by bonds. You can think of these bonds as tiny springs in motion. They stretch, wiggle, rotate and twist. When they absorb energy, the natural vibrations of bonds increase. Because of quantum mechanical constraints, these increases occur only to discrete energy levels. Different bond types (C-O, or C-H) and different vibration modes result in a series of absorptions at different wavelengths. By looking at which wavelengths of light were absorbed by a compound, we can deduce what types of chemical bonds are in the sample. Absorbances in the near infrared region of the spectrum can be so complex that they give rise to unique fingerprints of different chemicals.

Citizen Science: Spectrometers built with near infrared technology used to be large, expensive and restricted to universities. That's changing! The handheld spectrometer transmits chemical signatures to a smartphone which checks the pattern against a huge library of compounds in the "cloud" and returns the analysis to you within seconds. When you use it, not only will you be learning more about the chemical world around you but you'll also be helping to build a database of knowledge of the stuff around us. Now that's citizen science! 

REF: An introduction to near infrared (NIR) spectroscopy. A.M.C. Davies. https://www.impublications.com/content/introduction-near-infrared-nir-spectroscopy

GIFS: All gifs are from Wikipedia and are in the public domain.
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The Peacock Problem

‘The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!’ So wrote Charles Darwin in a letter to his friend, expressing his frustration at not being able to explain how natural selection could drive the evolution of this extravagantly ornamental display. Not only was there an obvious lack of survival advantage to an awkwardly heavy appendage, it came with an energy cost and added vulnerability to predators. How then, did the peacock's tail evolve?

Once again, it was Darwin who came up with the idea of sexual selection, that depends, "not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring"
  
By flaunting his "handicap", the peacock signals to his potential mate that he has survived despite the negative consequences! The good gene hypothesis suggests that the ornament is a proxy for a healthy immune system and metabolic fitness. The peahen's preference for gaudy displays drives the evolution of the tail by positive feedback: when she mates with the most fashionable male, she passes his traits on to her sons who in turn, are assured of reproductive success! Choosy mothers produce sexy sons and over many generations, runaway evolution results in strange and beautiful ornamentations like the lion's mane, the antlers of a stag and the blue-footed booby. In the 20th century, Ronald Fisher, who is considered the greatest evolutionary biologist after Darwin, argued that the female's preference and the male's development of the ornament must advance together until practical or physical limits halt any further exaggeration (http://en.wikipedia.org/wiki/Fisherian_runaway). 

We've seen how sexual selection gives rise to the difference in appearance between male and female (sexual dimorphism). Animals that are monogamous show less sexual dimorphism. Interestingly, our pre-Homo ancestors may have been more dimorphic compared to modern humans suggesting that we have become more monogamous over time! 

REF:The sight of the peacock's tail makes me sick: the early arguments on sexual selection. (2000) Hiraiwa-Hasegawa M. http://www.ncbi.nlm.nih.gov/pubmed/10824193

#ScienceSunday  
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Coral Cohabiters: Time for a Status Update?

Symbiosis derives from the terms sym for together, and biosis for life. The coral reef appears to be a poster child for a lifetime of togetherness. The soft tissues of coral polyps are embedded with hundreds of single-celled, free-swimming dinoflagellates, captured from nutrient poor, crystal clear tropical waters. Photosynthesis by dinoflagellates provides 95% of the organic food used by the polyps. In return, the dinoflagellates are housed in a safe environment where their hosts supply them with carbon dioxide and minerals needed for photosynthesis. 

Friends with Benefits: Like a Facebook status, the relationship of coral symbionts is complicated. Clearly, the coral benefits: oxygen and sugars produced by trapped dinoflagellates enable these corals to grow as much as three times faster as those without symbionts. But the converse is not true: in the symbiotic relationship, it takes ~70 days for the dinoflagellates to double, in contrast to a mere 3 days outside the coral. So symbiosis has a fitness cost for the algae. In reality, the coral host is more like an active farmer, who lures and engulfs the free-living dinoflagellates into captive domestication. When the coral is stressed, it loses control of the delicate energy balance in this relationship and expels its colorful guests en masse. Coral bleaching devastates the entire reef ecology and is a symptom of climate change which brings warmer, more acidic, nitrogen rich waters.

● All relationships lie along a continuum: from truly mutualistic, where both partners benefit and the success of one is tied to the success of the other, to commensalism, where one partner benefits but the other is neither harmed nor helped, and the extreme cases of parasitism, in which one organism exploits and harms the other. Isn't there a parallel with human relationships as well? 

The more we learn about the diversity of life and the structure of genomes, the more it appears that much of the evolution of biodiversity is about the manipulation of other species—to gain resources and, in turn, to avoid being manipulated (John Thompson, 1999). True mutualism may be rare in nature. Evolutionary selection tends to maximize individual fitness and conflict of interests are inevitable!

REF: Is the coral-algae symbiosis really ‘mutually beneficial’ for the partners? S.A. Wooldridge (2010) Bioessays 32: 615-625

IMAGES: Check out more stunning coral photographs by +Daniel Stoupin at http://www.microworldsphotography.com/

#ScienceSunday  
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Daffodils and Dementia

✿ It's spring time in Maryland, and in the words of the poet Wordsworth, my heart dances with the daffodils. Through the long winter, I conjured up memories of these cheerful blooms in my mind:

For oft, when on my couch I lie
In vacant or in pensive mood,
They flash upon that inward eye
Which is the bliss of solitude;
And then my heart with pleasure fills,
And dances with the daffodils.

✿ But an estimated 44 million people world wide who suffer from Alzheimer's disease are robbed of their memories by a progressive dementia. As the 6th leading cause of death in the U.S., Alzheimer's cannot be cured or prevented. One of the handful of drugs available to improve memory loss in patients is galantamine, which is extracted from the leaves and bulbs of daffodils (Narcissus) and snowdrops (Galanthus). These extracts have been in use since ancient times. In Homer's Greek epic, Odysseus is said to have used snowdrops to clear his mind bewitched by Circe. In the 1950s, a pharmacologist observed inhabitants of a remote Bulgarian village rubbing the extracts on their forehead and shortly after, the drug was approved for medical use. Galantamine increases the action of the neurotransmitter acetylcholine in some parts of the brain, both by making the receptor more sensitive to its action and by slowing down its removal. The drug has other interesting properties: it is said to promote lucid dreaming, improve sleep quality, memory loss in brain damage, and some autistic symptoms (http://en.wikipedia.org/wiki/Galantamine).  

✿ No drug has yet stopped the inexorable progress of Alzheimer's. Early intervention is key to effective treatment: in my lab, for example, we are studying endosomal pathology which is the earliest sign of problems at the cellular level (http://goo.gl/DtVUFT). Yet lack of funding stifles productive research. As Newt Gingrich points out in his recent Op-Ed for New York Times, we spend only 0.8% of the estimated 154 billion dollars of annual medical costs related to Alzheimer's disease on research to cure or prevent it

News Story: Newt Gingrich: Double the NIH Budget. April 22, 2015 http://goo.gl/Fq4PAS 

Daffodil GIF: http://headlikeanorange.tumblr.com/

#ScienceSunday  
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Souring on Sweeteners: Why Diet Sugars Don't Work

Sweet Serendipity: It was 1878, when a beaker of coal tar compounds boiled over in the chemistry laboratory of Ira Remsen at the newly founded Johns Hopkins University. Researcher Constantine Fahlberg cleaned up the mess, but later at dinner, his hands tasted surprisingly sweet as he put a piece of bread in his mouth. And this is how the first artificial sweetener was discovered! Named saccharin, it was 300 times sweeter than sugar. Soon, it was being prescribed to President Theodore Roosevelt, to counter his corpulence. More low-calorie sweeteners followed: sucralose, stevia and neotame, the last one being 10,000 times sweeter than table sugar. Today, 30% of adults and 15% of children in the U.S. consume low calorie sweeteners. A sweet deal, right?

Caloric Contradictions: Unfortunately, counterintuitive to expectations, studies show that people who consume large amounts of artificially sweetened drinks gain more weight and body fat compared to those who don’t. Could this be a case of reverse causation? Perhaps, increased body weight encourages people to turn to non-caloric sweeteners. However, this has been ruled out by (i) controlling for baseline body weight at the start of the study and by (ii) looking at weight changes in people who are not overweight to begin with. Another possibility is cognitive distortion: because non-caloric sweeteners are perceived to be healthy, we take that as permission to consume more high-calorie foods. Imaging studies of the human brain reveal a metabolic cause: unlike ordinary sugar, non-caloric sweeteners do not trigger the reward circuits that initiate satiety and fail to activate normal pathways of insulin release needed to deal with caloric loads. 

Diet to Diabetes: New research in both mice and humans showed that artificial sweeteners also change our gut microbiome, leading to glucose intolerance, the first step to diabetes. Surprisingly, if the feces from saccharin-fed mice was transplanted into mice whose guts were first cleared of bacteria by antibiotics, the sugar handling defect could be induced in the healthy mice. Oh, expletive!

The Archies sang, ♫ Oh honey, sugar, sugar..you are my candy girl and you've got me wanting you
https://www.youtube.com/watch?v=0MiQzAo6Cp8

REF: Artificial sweeteners produce the counterintuitive effect of inducing metabolic derangements. Susanne Swithers (2013) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3772345/

News Story & Link to Nature paper: http://www.nature.com/news/sugar-substitutes-linked-to-obesity-1.15938

  #ScienceSunday  
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Champagne Science

If an estimated 360 million glasses of champagne will be toasted this New Year's Eve, how many bubbles would they release? To figure this fun fact, we've got to get back to basics. 

It's a Gas: In 1810, French chemist Joseph-Louis Gay Lussac determined that in fermentation, glucose is converted to equal parts of ethanol and carbon dioxide gas according to the equation: 

                   C6H12O6 --> 2C2H5OH + 2CO2

To make champagne, this basic wine is dosed again with glucose (typically 24 g/L) for a second round of fermentation, yielding 11.8 g/L of CO2. All that CO2 is dissolved, under pressure (as much as 90 psi), inside the champagne bottle. 

Don't Shoot Your Eye Out!: The American Assoc. of Ophthalmologists warn that a champagne cork can launch at 50 mph! Why is this? Henry's Law (1803), paraphrased, says that the amount of gas dissolved in a liquid is proportional to the pressure of that gas above the liquid. When a champagne bottle is uncorked, the CO2 in the space above the liquid escapes, forcing the dissolved gas to come to a new equilibrium. This results in release of about 5L CO2 per bottle. 

Fizzy Physics: Dr. Gérard Liger-Belair didn't care for the over-blown bubble estimates being bandied around the popular press. So, armed with plenty of free samples from Champagne Houses Pommery, and Veuve Clicquot Ponsardin, he buckled down for some serious science (it's a hard life for a noble cause, hic!). After considering such factors as the van't Hoff equation for temperature dependence,  the critical radius for bubble nucleation and ascending bubble dynamics, he published his findings in a recent issue of the Journal of Physical Chemistry. The answer to our question? If 100 ml of champagne is poured straight down the center of a vertically oriented crystal flute, about one million bubbles will form, "if you resist drinking from your flute".  But, who's resisting? :)

With that, I raise my glass to yours along with approximately 360 trillion other bubbles world wide, to wish you a Happy New Year! 

REF: How many bubbles in your glass of bubbly? (2014) Gérard Liger-Belair http://pubs.acs.org/doi/abs/10.1021/jp500295e

Pop Sci: Back story on champagne research via +Chad Haney http://www.rsc.org/chemistryworld/2012/05/raising-glass-champagne

      #ScienceEveryday   #HappyNewYear   
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