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Rakesh Yadav
Works at Harvard-Smithsonian Center for Astrophysics
Attended Max-Planck institute for Solar System Research, Göttingen


Rakesh Yadav

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Do you do a lot of shopping on Amazon? has a sevice called "Amazon smile". If you use the link "" for your shopping, then Amazon will donate 0.5% of the purchase value to a charity of your choice. This will not cost you anything extra! Pretty cool stuff. You can chose your preferred charity in your Amazon account profile. Although 0.5% sounds small but something is better than nothing :-)
Amazon donates 0.5% of the price of your eligible AmazonSmile purchases to the charitable organization of your choice. AmazonSmile is the same Amazon you know. Same products, same prices, same service. Support your charitable organization by starting your shopping at Questions?
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Yep. They don't send out much in the way of advertisements, but I recall frequently seeing a pop up about it when I was on their website, so a couple of years ago I finally clicked on the pop up, read about the program, and have been supporting St. Judes Childrens hospital ever since. I even posted about it via my social media to make sure my friends and family were aware of it, some were, some weren't. Hmmmmm... Guess I should post about it again to help spread awareness or at least give a reminder.
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Rain, How you so big

In my last semester I attended a course on the physics of climate change. One of the lectures was on the physics of rain. I was really surprised to know that we still don't quite understand how raindrops form. Let me share with you what I have learned so far and where science is stuck.

The first step in the formation of raindrops is cloud formation. Air at a certain temperature can hold a certain amount of water, the warmer the air the more water it can hold. If we take a certain volume of moist air and cool it down the air has to loose some water to be equilibrium. Clouds are formed exactly when that happens: warm and moist air rises, it cools down at higher altitude where it looses some water by condensation on some particulate matter which is floating around.

Okay, we now have clouds. The droplets which make the cloud are rather small, with a typical diameter of about 10 microns (1 micron = 1/1000000 meters). These drops are too small to drop down since their falling speed is smaller than the typical speed of air motion inside a cloud. So, we have to grow them!

The mechanism through which a typical 10 micron sized cloud droplet grows to a typical raindrop with a diameter of about 1000 microns (or 1 millimetre) has been a thorny issue. One of the popular mechanism is called "Collision and Coalescence". Not every tiny cloud droplet has a size of 10 microns, some are somewhat smaller while others are a little bigger. These different sized drops are wiggling around with different speeds. Many drops collide and bounce back but some merge with each other and form even bigger drops. These bigger drops collide even further and become even bigger. In this way they can grow to bigger sizes. But, the problem is that this process is too slow and takes more than 1 hour to produce  raindrop sized droplets, while a typical rainy cloud stays only for about 30 minutes.

People seems to agree that this basic drop-merging mechanism should be at the root of raindrop formation. The effort right now is to identify additional factors which can speed up this process, e.g. clouds are very turbulent and turbulence does seem to speed this mechanism up by producing pockets of higher droplet density locally within a cloud. Higher droplet density means more collisions and faster drop merging. But, unfortunately, there is no consensus so far.

I shouldn't probably say that it is unfortunate that we don't understand the basic raindrop mechanism. Solving this mystery is giving a very good reason to many scientists to put on their science-hat and do science :)

Further reading:
You can also watch these nice online lectures:

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very cool!
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Interesting info-graphics providing a little perspective to the number of people killed by animals. Based on these numbers, the infamous sharks are actually the kindest animals!

I must say that it is a little ironic since technically speaking Humans are the deadliest animal on Earth in terms of number of animals killed by an animal species.

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Try to imagine a world beyond the shores of England.
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Scientifically correct "Art"

People usually complain that scientists often use rather boring way of showing their results, you know, lines and graphs and sort. But sometimes we also become a little artistic and play around with colours and other stuff to satisfy both our colleagues and general public (hopefully!).

Below is an artistic "star" which is a result of several months of number crunching on a supercomputer. The colours on this handsome star represent the velocity, blueish means plasma is coming towards you and orangish means it is going away from you. The curved lines coming out are magnetic field lines. 

We ran this simulation in order to explain a rather intriguing mystery. Our sun, even when it is most active, produces rather tiny sunspots (tiny as compared to the sun!). These sunspots produce certain amount of x-rays which we can measure. When scientists looked at other stars they found that other stars have much higher level of x-rays production. The consensus right now is that these stars have much larger spots, called "starspots", and much more as compared to the sun (imagine living in that star-system where your host star is spewing out x-rays like crazy). Well, there is not a solid simulation which actually produced big spots. If you look carefully at the simulation below, then you will see a dark patch in the upper half of the animation, which comes and goes. This is suppose to be a "starspot" which is rather huge as compared to what we see on sun. This is the first simulation which has produced such spots and I am genuinely excited about the results!

As always the simulation below have generated more questions than it answered. It will surely keep me busy for the coming months. Lets see what comes next...

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Recently a review article (; open access) was shared by +Jim Carver .  The article had a somewhat provocative title "Can We Say What Diet Is Best for Health?" and I was sucked into the trap.

Such review articles are very important as they try to paint a comprehensive picture of the field of research and ideally provide an un-biased analysis of the different studies conducted in the past. In lack of such articles a non-expert can easily be lost in the myriad of studies, sometimes reporting conflicting results. Anyway, I read the abstract, and then the introduction and then the whole thing. I found it very interesting and hence I am sharing the main points (from my perspective). The summary below is mostly a copy-paste text from the original article with some paraphrasing done for the sake of coherence. This is of course in no way a comprehensive summary. If you are intrigued by some aspects, then you should definitely read the article! 

The authors basically talk about popular dietary choices in current culture. Using scientific studies they try to narrow down on health-promoting foods. They examine 7 diets which are described below.

[Warning: brace yourself, a long one is coming]

Summary starts here 
Low carb diet 
Definition: total daily carbohydrate intake below 45% of total calories.

Interest in carbohydrate-restricted diets is long-standing, particularly in the context of diabetes management, and especially during the era before the advent of insulin therapy. It has become popular again in the context of weight control. Short to moderate intervention studies have shown efficacy in weight loss and favorably effects for quality of life. No long term intervention studies exist. Such studies cannot and do not, however, unbundle the effects of (a) carbohydrate restriction per se, on which the theory of the approach is predicated, and (b) calorie restriction, which is a virtually inevitable concomitant of choice restriction in general, and, perhaps especially, (c) restriction directed at carbohydrate, which constitutes the macronutrient class that provides the majority of calories for almost all omnivorous species. 

The basic principle for the diet is very general. For example the remaining calories can come from fat or protein, and, furthermore, these calories can be of plant of animal origin. The authors sum up by saying: The relevant literature remains equivocal, with most studies suggesting benefit from low-carbohydrate eating per se in comparison, generally, to either the typical Western diet or some version of a low-fat diet, with persistent concerns and uncertainty about longer-term effects on health outcomes.

Low-fat/vegetarian diet 
Definition: total daily fat intake below 20% of total calories.

Extensive body of literature exists. The diets of most primates are overwhelmingly plant based and low in total fat and are thought to be reflective of the earliest versions of the native human and prehuman diets, which evolved to include more meat in accord with hunting prowess. Intervention trials have long shown benefits from dietary fat restriction, ranging from weight loss to improvements in various biomarkers to reductions in cardiac events and mortality. Low-fat, plant-based eating has been associated with reductions in cancer and cardiometabolic disease. Uniquely, a very-low-fat diet has been shown to cause regression of coronary atherosclerosis (fat and plaque buildup on the walls of the arteries). High fiber intake in this (or others for that matter) diet might be crucial factor in their positive health effects. That said, there is no decisive evidence that low-fat eating is superior to diets higher in health-full fat in terms of health outcomes over the life span. When food choices are judicious in both contexts, the superiority of fat-restricted versus carbohydrate-restricted eating for weight loss and health is not reliably established.

Low-Glycemic diet
Definition: restricting/excluding foods with high-glycemic index

Clinical trial data are available and generally support efforts to reduce the glycemic load of the diet. Studies focused on this strategy have demonstrated benefits in the areas of weight loss, insulin metabolism, diabetes control, inflammation, and vascular function. Benefits have been seen in studies of both adults and children. Conversely, a high dietary glycemic load has been associated with adverse health effects. A recent meta-analysis concluded that high glycemic load and index are associated with increased risk of cardiovascular disease, especially for women. Most fruits are precluded by a preferential focus on the glycemic index as well. However, evidence that health benefits ensue from jettisoning fruits, or relatively high-glycemic-index vegetables, from the diet does not exist.

Often absent from discussions of low-glycemic diets is the consideration that, as with other dietary categories, there are various means to the same ends. McMillan-Price et al. studied alternative approaches to achieving a reduced glycemic load and demonstrated that a high-fiber, mostly plant-based approach offered metabolic advantages over a high-protein approach.

Mediterranean diet
Definition: based on the traditional dietary pattern that prevails in Mediterranean countries.

It has been associated with increased longevity, preserved cognition, and reduced risk of cardiovascular disease in particular, with some evidence for reduced cancer risk. However, longevity effects of diet, per se, are of course difficult if not impossible to unbundle from the effects of related lifestyle practices and cultural context. Adherence to a Mediterranean diet pattern is potentially associated with defense against neurodegenerative disease and preservation of cognitive function, reduced inflammation and defense against asthma, amelioration of insulin sensitivity, and relatively high scores of objectively measured overall diet quality. Studies have placed a particular emphasis on high intake of vegetables, fruits, nuts, olive oil, and legumes; moderate intake of alcohol; and limited consumption of meat. The contributions of cereal grains and fish are less apparent, perhaps because of lesser effects on health outcomes or less variation available for assessment.

Mixed, Balanced diet
Definition: it belongs to dietary patterns that include both plant and animal foods and conform to authoritative dietary guidelines, e.g. Dietary Recommendations of the World Health Organization

Such diets have figured prominently in the intervention trials of the National Institutes of Health (NIH). The Dietary Approaches to Stop Hypertension (DASH) diet is a salient example. Perhaps because of the ultimate accountability of the NIH to the tax-paying population at large, these federal diets have focused both on enhancements of nutrition and real-world applicability. Even so, efforts to translate the findings of intervention trials to community application have realized limited success. 

The DASH diet, as it has evolved, is a mostly plant-based diet inclusive of some animal products, with an emphasis on low-fat and nonfat dairy products. U.S. News & World Report has deemed DASH the most healthful diet in recent years. This designation, however, derives from the consensus opinion of a panel of expert judges rather than objective data. Data related to a direct comparison of DASH to other reasonable contenders for most healthful diet are lacking. There are some concerns about potential adverse effects of dairy intake that DASH-related literature tends to ignore. The Optimal Macronutrient Intake Trial for Heart Health has demonstrated short-term benefits for overall cardiovascular risk of several variations on the DASH diet theme - intake relatively high in carbohydrate, relatively high in protein, and relatively high in unsaturated fat - and suggested advantages to replacing some carbohydrate with either protein or fat. There are, however, no head-to-head comparisons of a DASH-style diet with other candidate dietary patterns to determine which produces the best long-term health effects.

Paleolithic diet
Definition: diet emulating pattern of our Stone Age ancestors with an emphasis on avoiding processed foods, and the intake of vegetables, fruits, nuts and seeds, eggs, and lean meats. In principle at least, dairy and grains are excluded entirely

Estimates of our Paleolithic dietary intake suggest that we are adapted to a high intake of plant foods and the nutrients they contain; a high intake of dietary fiber; and a fat intake of approximately 25% of total calories. One of the lesser challenges in reaching conclusions about the Paleolithic diet is variation in our ancestral dietary pattern and debate regarding its salient features. If Paleolithic eating is loosely interpreted to mean a diet based mostly on meat, no meaningful interpretation of health effects is possible. 

However even those emphasizing the role of hunting and meat suggest that some 50% of our Stone Age forebears’ calories came from gathered plant foods. Given the energy density of meat relative to most plants, even this translates to a diet that is, by bulk, mostly plants. Although superficially a departure from the other contending diets, a reasonable approximation of a true Paleolithic diet would in fact be relatively low in fat; low in the objectionable carbohydrate sources - namely, starches and added sugars; high in vegetables, fruits, nuts and seeds, and fiber; and low glycemic. An emphasis on lean meat remains distinctive, however, and may represent an advantage related particularly to satiety.

Vegan diet 
Definition: diets excluding all animal products - notably, dairy, eggs, and meats.

As with almost every other dietary approach, vegan eating can be done well or badly. Those committed to long-term veganism are typically well versed in the need to combine plant foods to achieve complete protein and in the role of select nutrient supplements. Those who adopt veganism for a short term, particularly adolescents seeking rapid weight loss, are not as reliably well informed. In general, vegan diets, when well constructed, are associated with health benefits. Intervention trials of short to moderate duration suggest benefits related to overall diet quality, inflammation, cardiac risk measures, cancer risk, anthropometry, and insulin sensitivity.

Intervention trials of vegan diets are limited to those willing to be assigned to such a diet for a span of weeks, months, or years. Given such constraints, data from intervention trials that are related to direct comparison of vegan diets with various other dietary patterns, that are defended from bias, and that examine long-term health effects are essentially nonexistent. This does not argue against vegan diets, but it does argue against overstating the basis for them in evidence related to human health outcomes.

A common message can be drawn from various studies conducted on various food habits: the case that we should, indeed, eat true food, mostly plants, is all but incontrovertible. Perhaps fortuitously, this same dietary theme offers considerable advantages to other species, the environment around us, and even the ecology within us.

The clutter of competing claims likely obscures the established body of knowledge and forestalls progress, much like the proverbial trees and forest. We need less debate about what diet is good for health, and much more attention directed at how best to move our cultures/societies in the direction of the well-established theme of optimal eating, for we remain mired a long way from it.
Summary ends here.

I hope this post motivates someone to read further and make responsible choices for themself. 

For +ScienceSunday,  curated by +Robby Bowles , +Allison Sekuler , +Rajini Rao , +Chad Haney , +Buddhini Samarasinghe , +Aubrey Francisco , and +Carissa Braun .


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Hehe, +Chad Haney . 
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Do other stars also have spots?

It has been a rather long time since I shared something on G+. Moving and research took its toll.

My recent research endeavors have led me to something really interesting which I would like to share. It is not so often that I get to summarize my research related content without spitting out scientific jargon :)

As you might know Sun is not a uniformly illuminated sphere of light. Every once in a while some strange things appear on the surface of the Sun which are darker and cooler as compared to the rest of the Sun. These darkish regions are called Sun spots.

Sun spots are a complex manifestation of interplay between turbulent plasma motions near the Sun's surface and strong magnetic fields which are generated in Sun's deep interior. Although strong magnetic fields don't give a damn when charged particles flow along them (this is why we get auroras near Earth's poles because magnetic field line are almost vertical and charged particles can enter our atmosphere unhindered ) they really don't like it when charged particles try to go across them. So, when strong magnetic fields pop-up near Sun's surface they interact with the charged plasma and drastically slow down the flow in that region. Since the plasma is not flowing with the same vigor as compared to the other parts of theSun it can not transfer much heat from the deep interior of the Sun. This region with strong magnetic field and suppressed plasma motions, called a Sunspot, acts like a plug which blocks heat from coming out. Less heat means that the gas in this region becomes less hot and shines less brightly. Hence as compared to the rest of the Sun's surface these regions appear darkish. This is why they are called "cool" spots. But don't be fooled, they are cool (at around 3000-4000K)  as compared to the rest of the sun which is at around 6000K.

Another interesting thing about these spots is that if you have a decent telescope you can identify these spots on Sun pretty easily. People have been keeping a record of the appears and disappearance of Sunspot for over two centuries! [EDIT: actually it's more than four centuries, people have been recording it since Galileo's time, including himself]  This observational record of Sunspots is the longest running experiment in human history. Pretty cool. But, hey, aren't we suppose to talk about star-spots? :)

The way through which these spotty features are produced on Sun is rather generic so it will not be surprising if these spots also exist on other stars. Many scientists expect that most of the stars in our universe have these spot on them. But what is the basis of such an expectation? What are the observational evidence we have to support this claim?

There are two ways in which we can infer that a star has spots on it. First one uses a star's light and the other uses the spectral line-profiles. I will talk about the second method later because it is somewhat involved. Lets see how the first method works.

Since stars are very veryyyyy far away we don't have the luxury of resolving their surface. Except for few nearby stars, all stars appear as point-sources of light. Unlike Sun where one can point a detector at southern or northern latitude and record different levels of light a far away star is just a point. A detector records one total value of its light. We can measure a star's light intensity at different times and construct a "light curve". The +NASA  Kepler satellite is nothing but a very sophisticated tool to make such light curves (very very precisely) for thousands of stars.

So we have one light-intensity value which is total sum of light projected towards us by that star. All stars rotate so this intensity value changes if a star has spots on it. Below you see an artificial light-curve (top panel) generated using an artificial star which for some reason has two square-shaped spots on it (yours truly is to blame for this :D). As the spot pass across the visible side of the star the visible intensity changes: it shows a dip when spot is visible. Such kind of variable visible-intensity is shown by most stars to some extent. This gives us a clue that most stars might have spots.
(There are also other stuff going on on stars which can produce variable intensity levels. For the sake of simplicity lets assume only spots are causing them.)

People also step further and try to infer back what kind of spots will produce an observed light-curve. It is like I give you the light curve which I have shown below and ask you to re-produce my rotating star with square-spots. Such an exercise will never give you a proper solution. In the example given below I assumed that I am watching the star such that its rotating poles are perpendicular us, i.e. I am watching it equator on. But unfortunately when we observe stars mostly we don't know the direction of the rotation axis of that star. This now becomes a free parameter in our reverse problem. The reverse problem also suffers one other drawback: spots on a star with one big spot and another star with two or three or more spots can be positioned in such a way that they both produce the same light-curve. Hence this reverse problem of inferring star spots from light-curves inherently produces multiple solutions which is not a good thing. We want unique predictions not vague ones which fit everything.

Inferring actual positions and size of star spots from their light-curve is a rather shaky business as you might have gathered. The second method which I mentioned above but didn't explain is much more robust. I will try to summarize that in near future.

Have a starry and spotty night everyone :)

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+Julian Gold , hmm....I see...Thanks for your indulgence. I need to keep this in mind while I am interpreting my simulation results in future.
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Radio Astronomy

Every year all of the PhD students in my institute take a week off and go for an educational retreat. These retreats are used for visiting places of scientific importance and also to learn something very different from what we usually do in our institute.

Last week was one such occasion and we had a couple of very nice introductory lectures on Radio Astronomy by a guest Professor. Since the Professor was an observational astronomer the lectures were heavy on the observational aspects of Radio Astronomy.

As it turns out Radio Astronomy was discovered accidentally by an engineer, Karl Jansky, at the Bell labs during 1930s. He was hired to investigate some problem in transmission caused by some unknown static source of radio waves. He found that radio waves being generated  in nearby/far thunderstorms were causing some problems to the company's transmission service. But, he also found a puzzling second source of radio waves. After more careful and long observations he found that the unknown source had some cyclic behaviour. It seemed to appear roughly every 24 hours. So, initially he though it was the Sun which was emitting Radio waves. But, after even closer inspection he found that the source was not appearing every 24 hours but rather every 23 hours and 56 minutes. He told these findings to his friend and the friend told him that this 23h56m is precisely the length of the sidereal day (day based on Earth's rotation rate about some fixed star in the sky, checkout wiki).

With this new information and after even more careful observations Jansky was able attribute the unkown source of radio waves to some location in the Sagittarius constellation in our galaxy. Jansky was unfortunately removed from this project by Bell labs and he discontinued this research. later Grote Reber build up on the work by Jansky and made many fundamental contributions.

As a part of our retreat we also visited the Effelsberg 100-meter radio telescope. I captured the time-lapse shown below when this behemoth was repositioning to observe another target. It is a very impressive engineering achievement. Built in around 1970, this telescope has a disk diameter of 100 meters and for almost 3 decades it was the largest steerable radio telescope. The deformities on the huge parabolic dish are of the order of a few millimetres!

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+David Loring , the engineering was pretty impressive. To add further, the dish of course deforms when the telescope turns, and the deformations are worse when the telescope is pointing close to horizon. To account for that the curvature of the dish deforms when the dish position shifts. Since it is old this adaptive deformation is not computer controlled but rather built into the dish hardware! Even smaller deformation due to wind and temperature difference in the disk can't be controlled by the main dish as it is too big. These wind and temperature errors are controlled by the secondary "mirror"  (the structure supported by the 3 beams inside the dish). This new mirror was installed later on and it is computer controlled.
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A very nice and interactive visualization of gender disparity in PhD graduates among different nations. By +Scientific American 

In the U.S., women are going to college and majoring in science and engineering fields in increasing numbers, yet here and around the world they remain underrepresented in the workforce. Comparative figures are hard to come by, but a disparity shows up in the number of Ph.D.s awarded to women and men. The chart here, assembled from data collected by the National Science Foundation, traces the gender gap at the doctoral level for 56 nations. The situation in individual countries varies widely, but as the numbers make clear, there are interesting exceptions to the global trend.

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Mighty Jupiter

Jupiter's magnetosphere is the largest structure inside our solar system (excluding the Sun of course). Jupiter has a rather strong magnetic field which is similar to Earth but about 10 times stronger.

To generate a magnetic field a planet needs a conducting fluid. Earth has molten iron core which does this job, while Jupiter has something called "metallic hydrogen". Theoretical and computational studies show that at the enormous temperature and pressure inside Jupiter hydrogen transforms into a conducting fluid state (hence the name "metallic" hydrogen). This should happen gradually as we go inside Jupiter, i.e. the fluid in Jupiter becomes more and more conducting as we go deeper and deeper.

You need to understand a small concept for the following part to make some sense. Good conductors (like metals) interact with magnetic fields while insulators (like plastic) do not.

When you look at Jupiter through telescope you will easily notice the "bands" of very strong east-west winds. This windy region does not interact with Jupiter's magnetic field because it is an insulator (like plastic or sand). But keep in mind that as we go inside Jupiter the fluid gradually becomes conducting, so at some depth these strong winds should start interacting with magnetic field. Very deep inside Jupiter, however, we have many reasons to believe that such winds can not exist.

Modelling the interaction of strong winds and inner magnetic field means modelling the highly conducting deep region of Jupiter as well as the outer surface layers where fluid starts to behave like an insulator. This was not possible in the past due to limited computational horsepower.

Recently, my colleagues simulated a model which does exactly this. These simulations are highly complex and take months on supercomputers! The image attached below shows how the magnetic field (grey tubes) looks like inside the simulation (a model Jupiter). The colours represent the magnetic field strength on various surfaces. In the very deep the magnetic field looks like mushed noodles and they come out near the poles of Jupiter. The interesting part is in the region which I have marked with a black arrow.  These grey tubes are trying to wrap around "Jupiter". This is because fast winds in this simulation are trying to go inside but magnetic field doesn't want that. In the outermost part of the simulation fluid is insulating and winds exist because it doesn't care about magnetic field. In the innermost part of the simulation fluid is highly conducting and it strongly interacts with magnetic field which kills these winds.

Twisty things happen when the fluid is not so conducting but not so insulating either. Here both winds and magnetic field reach a truce. In this region magnetic field wants to stay more-or-less parallel and winds also want to flow and wrap around. In this process of tug-of-war, magnetic field gets stretched like rubber bands and the strength of the winds gets reduced. This interesting feature was never seen in earlier simulations.

The awesome part is that +NASA's  Juno spacecraft due to arrive on Jupiter in 2016 will be able to detect these features in Jupiter's magnetic field if they exist! Confirmation from Juno will help us a lot in modelling magnetic fields in exo-planets and stars.

The simulation was done in my group (I am not involved though) and interested readers can refer to this paper "" for more info.

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Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK

This is one of those days when I get quirky and read stuff about the stuff we eat. I found an interesting paper (; open access) whose title is mentioned above. The paper tries to put some numbers on the greenhouse gas (GHG) emissions from different dietary practices, in UK. The following summary is mostly a copy-paste job with some paraphrasing here and there.

++++++Summary starts here++++++
When measured by consumption food is responsible for approximately one fifth of all GHG emissions attributable to the UK. There is considerable variation in the amount of GHG emissions related to different food groups, with animal-based products generally having much greater emissions than plant-based products per unit weight. Substantial reductions in GHG emissions can only be achieved through changes in consumption patterns and reduction in food waste. We use data on actual diets of vegans, vegetarians, fish-eaters and meat-eaters to estimate the difference in dietary GHG emissions attributable to these four diet groups. Previous estimates of dietary GHG emissions for self-selected dietary groups have not compared meat consumers with those who abstain from meat.

The analysis is based on data from participants in the EPIC-Oxford cohort, which consists of 65,000 (12,666 males and 42,838 females) participants generally aged 20 and over at recruitment between 1993 and 1999.

Diet groups:
High meat-eaters, 8286 people: those who consume >=100 g/day
Medium meat-eaters, 11971: meat consumptions 50 to 99 g/day
Low meat-eaters, 9332: meat consumption <50 g/day
Fish-eaters, 8123
Vegetarians, 15751
Vegans, 2041

A food-frequency questionnaire (FFQ) that estimates intake (frequency of consumption) of 130 different food items over the previous 12 months was completed at recruitment by most participants. Nutritional analysis of 130 food-item FFQ were based on nutritional data for 289 food codes taken from UK food composition tables. We estimated the GHG emissions associated with these 289 food codes. Carbon dioxide, methane and nitrous oxide emissions were incorporated. The data includes the life cycle of food commodities from the earliest stages of production to the retail distribution centre. We did not account for the cooking process (either at the industrial stage or at home) for any of the food codes.

Generally, there were significant trends towards lower total fat, saturated fat and protein consumption and higher carbohydrate, total sugar, fibre and fruit and vegetables consumption as animal-based food consumption decreased.

The highest dietary GHG emissions were found in high meat-eating men and the lowest dietary GHG emissions were found in vegan women. The mean observed values of dietary GHG emissions for meat-eaters (results reported for women and then men) was 46 % and 51 % higher than for fish-eaters, 50 % and 54 % higher than for vegetarians and 99 % and 102 % higher than for vegans. The results showed highly statistically significant differences in dietary GHG emissions between the six diet groups, with progressively higher emissions for groups with greater intakes of animal-based products.

After adjustment for sex and age, an average 2,000 kcal high meat diet had 2.5 times as many GHG emissions than an average 2,000 kcal vegan diet. Assuming that the average daily energy intake in the UK is 2,000 kcal, then moving from a high meat diet to a low meat diet would reduce an individual’s carbon footprint by 920kgCO2e every year, moving from a high meat diet to a vegetarian diet would reduce the carbon footprint by 1230 kgCO2e/year, and moving from a high meat diet to a vegan diet would reduce the carbon footprint by 1560 kgCO2e/year. For context, an individual travelling on an economy return flight from London to New York has an addition to their carbon footprint of 960kgCO2e. A family running a 10 year old small family car for 6000 miles has a carbon footprint of 2440 kgCO2e, roughly equivalent to the annual carbon saving of two high meat eating adults moving to a vegetarian diet.

Although the nutrient intakes estimated by the FFQ have been validated against food diaries and some biomarkers, the GHG emissions have not. Throughout the analysis presented here we have assumed that GHG emission related to food wastage is reasonably similar across all food groups, but this may not be the case. Estimates of food wastage in the UK suggest that wastage of fruit and vegetables is higher than for meat products, which could reduce the difference in GHG emissions between the dietary groups.

Analysis of observed diets shows a positive relationship between dietary GHG emissions and the amount of animal-based products in a standard 2,000 kcal diet. This work demonstrates that reducing the intake of meat and other animal based products can make a valuable contribution to climate change mitigation. Other work has demonstrated other environmental and health benefits of a reduced meat diet. National governments that are considering an update of dietary recommendations in order to define a ‘healthy, sustainable diet’ must incorporate the recommendation to lower the consumption of animal-based products.

++++++Summary ends here++++++

I hope this motivates people to read further about what they eat.

+ScienceSunday  #sciencesunday
+Rajini Rao  +Robby Bowles  +Buddhini Samarasinghe  +Allison Sekuler

Image taken from the cover of "Changing
what we eat" by the Food Climate Research Network.
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Rakesh Yadav

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A few good captures from St. Augustine, Florida. Really amazing beaches!
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When I lived in Jacksonville I used to surf near there in Guana River State Park. Really miss that place.
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Rakesh Yadav

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Some time back Dr. +Noah Diffenbaugh  shared an intriguing  graphic by +Mother Jones  which showed the water usage of few of the California's major crops. Post: . The +Mother Jones  articles was about California's dire drought situation, and it tried to put things in perspective about water usage.

I was a little surprised to note that the article didn't even mention the major players of water usage, i.e. livestock industry. Recently +Meiling hope  shared a post which contained a link to a very nice infographic post ( by +WWF Deutschland. The post was about the water usage of a typical Hamburger and it was shared on the occasion of world water day, but it was in German. I thought it might be worth sharing it with wider community so I translated the main parts of the infographic to English. 

Note: 1 Gallon =  3.8 Liters
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<< Less than 2% of the population experience general adverse reactions to foods – and 90% of all the problems come from just eight foodstuffs: nuts, including peanuts, nuts from trees such as walnuts and pecans, fish, shellfish, eggs, milk, soya and wheat. >> 

<< Food and Drug Allergies – Approximately 6% of allergy sufferers have food/drug allergies as their primary allergy. Food allergy is more common among children than adults. 90% of all food allergy reactions are cause by 8 foods:  milk, soy, eggs, wheat, peanuts, tree nuts, fish and shellfish. For drug allergies, penicillin is the most common allergy trigger. >> 
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  • Harvard-Smithsonian Center for Astrophysics
    PostDoc, 2015 - present
  • Max-Planck-Institute for Solar System Research
    PostDoc, 2015 - 2015
  • Indian Institute of technology, Kanpur, India
    Project Associate, 2011 - 2012
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  • Max-Planck institute for Solar System Research, Göttingen
    PhD, Computational Astrophysics, 2012 - 2015
  • University of Göttingen
    PhD, Computational Astrophysics, 2012 - 2015
  • Indian Institute of Technology Kanpur
    Integrated M. Sc., Physics, 2006 - 2011