Why are there “dew drops” at the tips of leaf veins?

Why are there “dew drops” at the tips of leaf veins?

❦ Have you ever seen clear orbs of water glisten along a leaf edge? You may have mistaken them for dew drops, which are caused by moisture from the air condensing on cool surfaces. But these drops are only found at the edges of leaves and if you look around- they won’t be found on dead leaves. So what are they?

❦ Plants use a plumbing system of xylem tubes to move water and nutrients. During the day, transpiration (water evaporation) from leaves creates a vacuum that pulls the column of water up from the roots to the leaves. At night, the stomata (leaf pores) close, transpiration stops and salts accumulate in the xylem of roots, drawing in water from the surrounding soil by osmosis. The excess water rises up the xylem tubes and is forced out at the leaf tips through openings called hydathodes. This exudation of plant sap is known rather inelegantly as guttation, and only happens at night. The water pressure is not strong enough to rise beyond 3 feet, so guttation is not seen on tree leaves. The thermal image (inset) taken by infrared photography shows the cooler temperature (blue) in the guttation droplets.

❦ When the drops dry, they sometimes leave behind a residue of salts and minerals. This is not a problem, unless the soil is over-fertilized resulting in fertilizer burn of leaf tips. In the same way, guttation droplets in corn seedlings were shown to have high levels of neonicotinoid compounds, used as pesticidal coatings on the seed. These concentrations could be a lethal dose for honey bees that sip on guttation drops as a water source. While shedding toxins through guttation drops protects the plant, it may have repercussions – both beneficial and harmful, on insects and other animals. 

Inset of thermal image: http://thermal-imaging-blog.com/index.php/page/13/#.Vq1LIvkrLcs

REF on neonicotinoids in guttation droplets #openaccess: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4284396/

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The Flight of the Hummingbird

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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Gene Drives: Green Signal or Back Seat?

Should we use Gene Drive engineered mosquitoes to fight Malaria? Poll results: 972 votes on Google Plus, 11/2015

What is the deadliest animal on earth? If you’re thinking of the great white shark or a venomous snake, you could be wrong. Counting human deaths, it is the innocently named (Spanish for “little fly”) mosquito. Millions, mostly children in third world countries, are killed or sickened each year by malaria, dengue, yellow fever and encephalitis caused by parasites and viruses that are transmitted by mosquito bites. This happens despite billions of dollars spent, years of research and potential cures ranging from vaccines and drugs to public health management. 

Stop or Go, that is the Question: Imagine if the mosquito could kill the parasite before it has the chance to spread to its human victims. For example, the mosquito could be engineered to make antibodies against Plasmodium, killing the parasite soon after it enters the mosquito after a blood meal. Just like a vaccination, nearly all mosquitoes would need to carry this new trait to be effective. There is a way to do this and it is not a new idea. What used to be theory, however, has just become a reality. A new paper published in the journal PNAS has now changed the question from Can we do this? to Should we do this?

What are Gene Drives?: Normally, the chance that any gene trait is passed from parent to offspring is 50%, since only one of a chromosome pair is inherited from that parent. But some selfish genes can copy themselves so that both chromosomes carry the trait, which now affects 100% offspring. A gene drive consists of DNA sequences that provides the technical ability to do this. With the new CRISPR/Cas9 tool that precisely cuts and inserts any gene of interest, the gene drive has become a reality. 

Can Gene Drives work on Humans? Gene drives work best in fast reproducing species, like mosquitoes, that can be released in large numbers. For this reason, they are not going to be effective in spreading inadvertently through humans, or even commercial crops and animals which are bred by controlled processes like artificial pollination and insemination.  

Gene Drives are Natural: For example, a gene called P element swept through all fruit flies in the wild, but is not found in lab strains that were isolated before it spread. 

Gene Drives can be Reversed: For each gene drive that spreads a trait, a reverse gene drive can undo the genetic changes in the original strain. Such reversal drives should be tested in advance, and could be released to stop the spread of any unintended consequences.

What else can Gene Drives do? Besides targeting mosquitoes, gene drives could be used to eradicate invasive species, or reverse resistance to herbicides and pesticides. 

Take the Poll: A public conversation based on sound scientific information, weighing pros and cons, must be the starting point for developing policy. Engineered mosquitoes that could rapidly spread in the wild and eradicate the malarial parasite have been made. Here is the question: Should we use Gene Drive engineered mosquitoes to fight Malaria? 

FAQ on Gene Drives: http://goo.gl/V3Jmz1

Image: Matt Panuska

Pop Science Read: http://goo.gl/oROVBG

Advanced Read: http://goo.gl/uTN47v

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I am really worried about priorities..

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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Science Mystery Pix

Science Mystery Pix

Stomatal pores under a leaf? Sand dunes on Mars? Clams clamoring to be fed? Hint: the image illustrates an evolutionary adaptation. Take a guess, then read on!

Secret of Serotiny: In 1961, a fire destroyed 28,000 acres of forest in Montana. Since then, the lodgepole pine has established dominance over this vast acreage, with a density of tens of thousands of trees per acre. Yet, this pine normally does not spread its seed beyond a range of some 200 meters. How did the lodgepole pine achieve this remarkable biotic potential?

Its secret was serotiny: millions of seeds per acre were stored inside cones, high up at the canopy top of mature stands, for just this scenario. The heat of the fire melted the resin that kept the cones closed, releasing seeds to be carried by wind or gravity over several days, to land on burned but cooling ground. With little competition, more light, warmth and nutrients from ash, the seedlings flourished, making this pine an aggressive pioneer species.  

Serotiny is the adaptation by some plants that hold on to their seeds for decades after they are mature, releasing them only in response to a specific environmental trigger. The trigger could be dryness, water, or fire. Some desert plants have adapted to release seeds after rainfall, when the chances of successful germination are high. Other plants release seeds only after they die, a feature known as necriscence. Oddly, fire-survival strategies may be paired with fire-embracing adaptations, such as retaining dead (and flammable) branches instead of the more common practice of self pruning . Known as niche construction, this double strategy ensures removal of poorly adapted plants in regions susceptible to natural fires. 

The Fiery Cretaceous: Fire has been an effective agent of natural selection for at least 125 million years and possibly longer! The high oxygen levels (23-29% compared to today’s 21%) in Earth’s paleoatmosphere of the early Cretaceous fueled frequent fires, captured as charcoal in the fossil records. Since then, fire adapting traits in plants arose independently, many times.  Our Mystery Pix can now be revealed as the cone of a Banksia tree, endemic to Australia, with open seed pods after a bushfire. Photo via PinkRockAus’s Fotothing http://goo.gl/ZEfDHm

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Project 523: From Chinese Secrets to Nobel Gold

Project 523: From Chinese Secrets to Nobel Gold 

☯ On May 23, 1967 a secret military project was launched by the Chinese government. It was the height of the Vietnam war, and the communist north was losing more soldiers to the scourge of malaria than to the battlefield. An emergency plea was made to a powerful sympathizer, Chairman Mao Zedong, to find a cure. Code named Project 523 (after the date), more than 500 scientists were recruited from 60 military and civilian organizations, remarkably at the height of China’s Cultural Revolution which closed universities and banished scientists and intellectuals. One group of scientists was tasked with searching through ancient Chinese records of herbal remedies.

☯ 39 year old phytochemist, Youyou Tu, was sent to the sweltering rain forests of Hainan, an island in southern China, where she witnessed the devastation of malaria first hand. By then, many ancient herbal compounds had been tested. The extract of quinghao (green-blue wormwood) appeared to be effective, but success was sporadic. Tu carefully read the recipe of 4th century writing of Ge Hong: qinghao, one bunch, take two sheng [2 × 0.2 l] of water for soaking it, wring it out, take the juice, ingest it in its entirety. Tu reasoned that extraction by boiling might destroy the active ingredient. So she tested a cold ether extract of the plant and it worked. She even voluntarily consumed the extract to make sure it was safe, then tested it on human patients. Her results were published anonymously in 1977. Today, 84 year old Youyou Tu received the Nobel Prize for Medicine, which she shared with two other scientists, an Irishman and Japanese, who worked on treatment of other parasitic diseases. 

☯ The success of artemisinin as a modern day miracle cure for Plasmodium falciparum malaria (spread by mosquitoes, and blamed annually for 1 million deaths world wide), rests on the breakthroughs of hundreds of scientists. Those who discovered a richer source of the drug in Artemisia annua grown in Sichuan province, those who purified the drug away from toxic contaminants, who solved the new and unusual chemical structure, synthesized better and safer derivatives for the treatment of malaria. While celebrating her success as the first Chinese woman to receive a Nobel in Medicine, let us not forget that Youyou Tu’s Nobel represents an entire field of research. Tu herself is a modest individual who has drifted into obscurity despite receiving a Lasker Award, the so-called American Nobel, in 2011. At the time, she said, “I think the honor not only belongs to me but also to all Chinese scientists.”

Project 523: https://en.wikipedia.org/wiki/Project_523

Nobel Press Release: 

http://www.nobelprize.org/nobel_prizes/medicine/laureates/2015/press.pdf

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Falafel Faves and Favism

Falafel Faves and Favism

★ I flagged the Palestinian taxi driver with some relief: the streets were deserted, the restaurants in the old city of Jerusalem were shuttered for Shabbat and I was growing increasingly peckish. After I convinced him, with some effort and considerable diplomacy, that I did not want a tour of Bethlehem, he admitted defeat with good humor and took me to a little Palestinian restaurant where I had the most delicious falafels– golden nuggets of chickpea goodness drizzled with tangy tahini atop mounds of fluffy pita bread, still warm from the oven.

★ Did you know that falafels were originally made from fava beans by the Egyptian Copts, who become vegans during Lent? But fava beans can trigger life-threatening anemia in a fraction of people of Mediterranean descent, including Jews, so chickpeas have been used as a safer replacement. Known as favism, the disorder is due to inherited variants in the enzyme G6PD, which stands for glucose-6-phosphate dehydrogenase, a somewhat less tasty mouthful than falafel.

★ In red blood cells, G6PD replenishes an important anti-oxidant, glutathione that guards against damaging free radicals generated from certain compounds (like vicine and divicine) found in broad beans. People with G6PD deficiency, nearly all males since the gene is located on the X-chromosome, lack this protective mechanism and their damaged red cells gives them anemia, jaundice and occasional hemolysis. For extra credit: why did these harmful mutations persist in some populations instead of being weeded out by natural selection?  It turns out that G6PD mutations protect against malaria, likely by hastening clearance of red blood cells infected with the malarial parasite Plasmodium.

★ To make falafel, start with dry chickpeas. Fresh bought works best (save those fossilized pellets from the back of your pantry for ammunition in case of squirrel invasion). Soak the chickpeas overnight in generous excess of water and they will reward you by becoming pleasingly plump and doubling in quantity. One cup dry chickpeas should be plenty, two will feed a crowd. As any responsible scientist would do, I repeated my falafel experiment for n = 3 before publishing. Many thanks to my enthusiastic students for confirming the protocol and consuming the product! For the recipe see:  https://madamescientist.wordpress.com/2015/09/15/falafel-faves-and-favism/

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Falafel Faves and Favism

I flagged the Palestinian taxi driver with some relief: the streets were deserted, the restaurants in the old city of Jerusalem were shuttered for Shabbat and I was growing increasingly peckish. After I convinced him, with some effort and considerable diplomacy, that I did not want a tour of Bethlehem, he admitted defeat with good humor and took me to a little Palestinian restaurant where I had the most delicious falafels- golden nuggets of chickpea goodness drizzled with tangy tahini atop mounds of fluffy pita bread, still warm from the oven.

Falafels, made with chickpeas, Israeli style

Falafels, made with chickpeas, Israeli style

Back in the US, I succumbed to ordering falafel every time I saw it on a menu. Doomed to disappointment, I’ve endured pasty, tasteless balls of mush with poky exteriors and uncooked interiors. No matter, I would make my own. Foolishly, I picked up a cardboard box of falafel mix from the “middle eastern” aisle of my grocery store only to discover what was apparently cardboard on the inside as well. Next, I turned to a Food TV diva who pureed canned chickpeas in a food processor and attempted to “bind” the sorry mess with eggs and a punitive stint in the cooler. Fortunately, I stumbled upon the food blog of Tori Avey, who explained that cooked or canned chickpeas have too much moisture to achieve the right texture. Start with dry chickpeas. Fresh bought works best (save those fossilized pellets from the back of your pantry for ammunition in case of squirrel invasion). Soak the chickpeas overnight in generous excess of water and they will reward you by becoming pleasingly plump and doubling in size. One cup dry chickpeas should be plenty, two will feed a crowd.

Did you know that falafels were originally made from fava beans by the Egyptian Copts, who become vegans during Lent. But fava beans can trigger life-threatening anemia in a fraction of people of Mediterranean descent, including Jews, so chickpeas have been used as a safer replacement. Known as favism, the disorder is due to inherited variants in the enzyme G6PD, which stands for glucose-6-phosphate dehydrogenase, a somewhat less tasty mouthful than falafel.

__2974546_orig

Favism results from G6PD deficiency. Cartoon reproduced with permission from http://www.medcomic.com/050414.html

In red blood cells, G6PD replenishes an important anti-oxidant, glutathione that guards against damaging free radicals generated from certain compounds (like vicine and divicine) found in broad beans. People with G6PD deficiency, nearly all males since the gene is located on the X-chromosome, lack this protective mechanism and their damaged red cells gives them anemia, jaundice and occasional hemolysis.  For extra credit: why did these harmful mutations persist in some populations instead of being weeded out by natural selection?  It turns out that G6PD mutations protect against malaria, likely by hastening clearance of red blood cells infected with the malarial parasite Plasmodium.

Now that we’ve got the important part figured out, making falafel is deliciously simple.

  • Take a roughly chopped small onion, a couple cloves of garlic, and a packed cup of parsley and give them a whirr in the food processor, to mince. I like my falafel to have flavorful flecks of green, so I use plenty of parsley and/or cilantro.
  • Next, add the drained and soaked chickpeas to the processor and continue to process until the mixture takes on the crumbly appearance of moist couscous. Add a tablespoon or two of flour to bind. You can use white flour, but since I have a handy stash of besan or chickpea flour in my Indian pantry, I use the opportunity to intensify the nutty pea flavor. Do not over-process, or you’ll be serving hummus.
  • Remove, and mix with seasoning: salt and ground pepper to taste, a tsp of cumin powder, tbsp of coriander powder, a pinch or more of cayenne. I sneak in some turmeric because I like the mellow yellow contrast with parsley flecks. As always, experiment and make the recipe your own.

Falafels, tinted with a hint of turmeric and flecked with green parsley

Falafels, tinted with a hint of turmeric and flecked with green parsley

  • By now, you should have heated the oil (peanut or other) for frying.  If not, store your mix in the refrigerator until you’re ready. Use your palms and squeeze lightly to form round balls with the mixture, and set aside. Don’t worry if some liquid squeezes out, the falafel balls will be delicate but will quickly firm up on frying. I promise. Test the temperature by dropping one formed ball into the center. If it browns too quickly, the oil is too hot and you’ll end up removing them prematurely before the insides are cooked. They should take about 3 minutes to brown on one side, so you can roll them over for another 3 minutes. Drain on paper towels and taste-test one -or two, or three, all in the quest for perfection, of course.

Falafels should brown slowly, so that they are crunchy on the outside and tender but perfectly cooked on the inside.

Falafels should brown slowly, so that they are crunchy on the outside and tender but perfectly cooked on the inside.

I served the falafel with generous helpings of baba ganouj, my go to recipe with grilled eggplant in a creamy tahini sauce.

Baba ganoush is a creamy, tangy dip made with sesame seed paste (tahini) and mashed roasted eggplant, garnished with generous drizzles of olive oil and paprika.

Baba ganouj is a creamy, tangy dip made with sesame seed paste (tahini) and mashed roasted eggplant, garnished with generous drizzles of olive oil and paprika.

As any responsible scientist would do, I repeated this experiment for n = 3 before publishing. Many thanks to my enthusiastic students for confirming the protocol and consuming the product! 

2015-05-10 04.41.16

Hungry Hopkins students Donna, JP and David, who helped taste test the falafel recipe on a sunny spring Sunday …for Science!

Pots for the patio: mixing up petunias, coleius and dragon grass.

Pots for the patio: mixing up petunias, coleius and dragon grass.

2015-04-28 06.39.39

A prince amongst the coriander, waiting for a kiss?

Posted in FOOD, Humor, Middle Eastern, science, Travel, Vegetarian | Tagged , , , , | 10 Comments

Herbal Cancer Cure: Weeding out the Hype

Herbal Cancer Cure: Weeding out the Hype

A recent G+ post (https://goo.gl/pGDJUZ) claimed that artemisinin, derived from an ancient Chinese herb Artemisia annua, kills 98% of lung cancer cells in less than 16 hours. What’s wrong with this claim?

◈ The comments fell into two categories: some outright disbelief If this is factual, it’d be amazing and More pseudoscience, Geesh! More common were conspiracy theories from the predictable, The W.H.O., F.D.A., C.D.C., etc. Can’t patent it, so they can’t make money off of it. to the bizarre, Funny thing is that the government gets their money off of cancer so I wonder if they’ll make this illegal and claim it’s got a side-effect that makes people experience what they would if they used Marijuana. Idk, but the government’s gonna F it up somehow. Let’s examine the claims and counterclaims. 

98% of cancer cells are killed by artemisinin…..in a culture dish! It’s easy to kill cells in a dish -just ask my students 🙂 These are in vitro findings. How about in vivo? Experiments done in rodents are indeed promising and have been reviewed and reported. Unfortunately, we scientists are excellent mouse doctors, and many drugs that cure cancer in mice under controlled, ideal lab conditions fail in the clinic. Does it work on humans? There are a few case reports of using artemisinin in humans. But, these are anecdotal and of limited use, since the patients were under chemotherapy anyway. What is needed are large scale randomized clinical trials with placebo controls to check if this herb is effective against cancers. Such trials cost a billion dollars and have not yet been done. 

Artemisinin has been safely tested in over 4000 patients…this claim from a doctor in a popular video (https://youtu.be/_Or8xLOGBu8) probably refers to a Phase I trial where only safety is monitored. Notice the doctor does not say if the herb was effective against cancer in these 4000 patients. 

The FDA will never approve it….wrong, because it is already an FDA-approved antimalarial drug. In fact, artemisinin in combination with other drugs is the gold standard for treatment of Plasmodium falciparum malaria worldwide. The WHO has negotiated with Novartis and Sanofi-Aventis to obtain the drug at cost, with no profit. 

Bottom line: Both sets of comments are off the mark! The potential of artemisinin as a cancer chemotherapeutic should not be dismissed as pseudoscience until proven otherwise. As for the conspiracy theorists, they’re just wrong.

Wiki: https://en.wikipedia.org/wiki/Artemisinin #OpenAccess REF: Anticancer Effect of AntiMalarial Artemisinin Compounds. (2015) Das, AK http://www.ncbi.nlm.nih.gov/pubmed/25861527

#ScienceSunday  

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The Greening of Greenhouse Gas

The Greening of Greenhouse Gas

It’s a Gas: Driving through the Western Ghat mountains along the continental edge of the Deccan Plateau, I was charmed by this vista of sculpted terraces with verdant blades of rice emerging from submerged paddy fields. Little did I know then that paddy fields generate 50-100 million tonnes of methane each year, a potent greenhouse gas with 25 times the heat trapping potential of carbon dioxide. Although the flooded fields keep weeds at bay, microbes harbored under the warm, waterlogged soil feed on organic matter exuded by roots, releasing methane and accounting for about 20% of human-related production. In China, farmers have begun draining fields mid-season to interrupt methanogenic bacteria. But India is still responsible for nearly a third of the methane emissions. 

It’s Barley There: Now, thanks to genetic engineering, a new strain of rice yields more grain and produces less methane. Researchers spliced a gene from barley, encoding a master regulator (transcription factor) into rice. The gene, dubbed SUSIBA2 (acronym for “sugar signaling in barley 2”) increases the output of sugar and starch in the seeds, leaves and shoots of the rice plant, leaving less biomass in the root. This strongly decreased the methanogenic bacteria in the rhizosphere, or region around the root. In a 3-year field trial, methane emissions fell by 90%.

Rice, Rice, Baby: The making of starch is under the direction of a set of genes which carry in front of them stretches of DNA sequences (promoters) known as sugar responsive elements or SURE. Aren’t you loving the acronyms? When a little bit of sugar is made, SUSIBA2 is activated and it turns on genes that make even more sugar, to create a snowballing effect. The sugar is converted to starch, diverting carbon to the grains and away from the root, starving the methane producing bacteria of food. Now that’s a sweet way to cool down our planet!

This work was a collaboration between scientists at Universities and non-profit research Institutes in Sweden, China and the US. The authors have no competing financial interests. 

Paper (paywalled): http://www.nature.com/nature/journal/v523/n7562/full/nature14673.html 

#ScienceSunday  

 

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