How Your Digestive System Works?

Across the whole planet, humans eat on average between 1 and 2.7 kilograms of food a day. That's over 365 kilograms a year per person and more than 28,800 kilograms over the course of a lifetime. And every last scrap makes its way through the digestive system. 

Comprised of ten organs covering nine meters, and containing over 20 specialized cell types, this is one of the most diverse and complicated systems in the human body. Its parts continuously work in unison to fulfil a singular task: transforming the raw materials of your food into the nutrients and energy that keep you alive.

Spanning the entire length of your torso, the digestive system has four main components. First, there's the gastrointestinal tract, a twisting channel that transports your food and has an internal surface area of between 30 and 40 square meters, enough to cover half a badminton court.

Second, there's the pancreas, gallbladder, and liver, a trio of organs that break down food using an array of special juices. Third, the body's enzymes, hormones, nerves and blood all work together to break down food, modulate the digestive process and deliver its final products. Finally, there's the mesentery, a large stretch of tissue that supports and positions all your digestive organs in the abdomen, enabling them to do their jobs.

The digestive process begins before food even hits your tongue. Anticipating a tasty morsel, glands in your mouth start to pump out saliva. We produce about 1.5 litres of this liquid each day. Once inside your mouth, chewing combines with the sloshing saliva to turn food into a moist lump called the bolus. 

Enzymes present in the saliva break down any starch. Then, your food finds itself at the rim of a 25-centimetre-long tube called the oesophagus, down which it must plunge to reach the stomach. Nerves in the surrounding esophagal tissue sense the bolus's presence and trigger peristalsis, a series of defined muscular contractions. That propels the food into the stomach, where it's left at the mercy of the muscular stomach walls, which bound the bolus, breaking it into chunks.

Hormones, secreted by cells in the lining, trigger the release of acids and enzyme-rich juices from the stomach wall that starts to dissolve the food and break down its proteins. These hormones also alert the pancreas, liver, and gallbladder to produce digestive juices and transfer bile, a yellowish-green liquid that digests fat, in preparation for the next stage. 

After three hours inside the stomach, the once shapely bolus is now a frothy liquid called chyme, and it's ready to move into the small intestine. The liver sends bile to the gallbladder, which secretes it into the first portion of the small intestine called the duodenum. 

Here, it dissolves the fats floating in the slurry of chyme so they can be easily digested by the pancreatic and intestinal juices that have leached onto the scene. These enzyme-rich juices break the fat molecules down into fatty acids and glycerol for easier absorption into the body.

The enzymes also carry out the final deconstruction of proteins into amino acids and carbohydrates into glucose. This happens in the small intestine's lower regions, the jejunum and ileum, which are coated in millions of tiny projections called villi. These create a huge surface area to maximize molecule absorption and transference into the bloodstream.

The blood takes them on the final leg of their journey to feed the body's organs and tissues. But it's not over quite yet. Leftover fibre, water and dead cells sloughed off during digestion make it into the large intestine, also known as the colon. The body drains out most of the remaining fluid through the intestinal wall. What's left is a soft mass called stool. 

The colon squeezes this byproduct into a pouch called the rectum, where nerves sense it expanding and tell the body when it's time to expel the waste. The byproducts of digestion exit through the anus and the food's long journey, typically lasting between 30 and 40 hours, is finally complete.

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How Sugar Can Be So Addictive?

Picture warm, gooey cookies, crunchy candies, velvety cakes, waffle cones piled high with ice cream. Is your mouth watering? Are you craving dessert? Why? What happens in the brain that makes sugary foods so hard to resist?

Sugar is a general term used to describe a class of molecules called carbohydrates and it's found in a wide variety of food and drink. Just check the labels on sweet products you buy, Glucose, Fructose, Sucrose, Maltose, Lactose, Dextrose and Starch are all forms of sugar. So are high-fructose corn syrup, fruit juice, raw sugar, and honey. And sugar isn't just in candies and desserts, it's also added to tomato sauce, yoghurt, dried fruit, flavoured waters, or granola bars.

Since sugar is everywhere, it's important to understand how it affects our brain. What happens when sugar hits your tongue? And does eating a little bit of sugar make you crave more? 

So let's find answers to those question. You take a bite of cereal. The sugars it contains activate the sweet-taste receptors, part of the taste buds on the tongue, in your brain. These receptors send a signal up to the brain stem and from there, it forks off into many areas of your forebrain, one of which is the cerebral cortex.

Different sections of the cerebral cortex process different tastes: bitter, salty, umami and, in our case, sweet. From here, the signal activates the brain's reward system of your brain. This reward system is a series of electrical and chemical pathways across several different regions of the brain. It's a complicated network, but it helps answer a single, subconscious question: should I do that again?

That warm, fuzzy feeling you get when you taste a chocolate cake? That's your reward system saying, "Mmm, yes!" And it's not just activated by food. Socializing, sexual behaviour and drugs are just a few examples of things and experiences that also activate the reward system.

But overactivating this reward system kickstarts a series of unfortunate events for you. Like, loss of control, craving and increased tolerance to sugar.

Let's get back to our bite of cereal ok. It travels down into your stomach and eventually into your gut. And guess what? There are sugar receptors here, too. They are not taste-buds, but they do send signals telling your brain that you are full or that your body should produce more insulin to deal with the extra sugar you are eating. 

The major currency of our reward system is dopamine, an important chemical or neurotransmitter. There are many dopamine receptors in the forebrain, but they are not evenly distributed. Certain areas contain dense clusters of receptors, and these dopamine hot spots are a part of your reward system. 

Drugs like alcohol, nicotine or heroin send dopamine into overdrive, leading some people to constantly seek that high, in other words, to be addicted. Sugar also causes dopamine to be released, though not as violently as drugs. 

Sugar is rare among dopamine-inducing foods. Broccoli, for example, has no effect, which probably explains why it's so hard to for me to eat veggies, maybe it's true for you too.

Speaking of healthy foods, let's say you're hungry and decide to eat a balanced meal. You do and dopamine levels spike in your reward system hot spots. But if you eat that same dish many days in a row, your dopamine levels will spike less and less, eventually levelling out. That's because when it comes to food, our brain evolved to pay special attention to new or different tastes. Why?

Two reasons: first, to detect food that's gone bad for you. And second, because the more variety you have in your diet, the more likely you are to get all the nutrients you need. To keep that variety up, we need to be able to recognize new foods and more importantly, we need to want to keep eating new foods. And that's why the dopamine levels off when a food becomes boring.

Now, back to that meal. What happens if, in place of the healthy balanced dish, you eat sugar-rich food instead? If you rarely eat sugar or don't eat much at a time, the effect is similar to that of the balanced meal. But if you eat too much, the dopamine response does not level out. In other words, eating lots of sugar will continue to feel rewarding. In this way, sugar behaves a little bit like a drug.

It's one reason people seem to be hooked on sugary foods. So, think back to all those different kinds of sugar. Each one is unique, but every time any sugar is consumed, it kickstarts a domino effect in the brain that sparks a rewarding feeling. 

Too much, too often, and things can go into overdrive. So, yes, overconsumption of sugar can have addictive effects on the brain, but a wedge of cake once in a while won't hurt you. So do eat sweet, because you need it. Just don't eat too much.

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What Is Aerogel?

Aerogel is a synthetic porous ultralight material derived from a gel, in which the liquid component for the gel has been replaced with a gas. The result is a solid with extremely low density and low thermal conductivity. Nicknames include frozen smoke, solid smoke, solid air, solid cloud, blue smoke owing to its translucent nature and the way light scatters in the material.

Aerogels are a diverse class of porous, solid materials that exhibit an uncanny array of extreme materials properties. Most notably aerogels are known for their extremely low densities (which range from 0.0011 to ~0.5 g cm-3). In fact, the lowest density solid materials that have ever been produced are all aerogels, including a silica aerogel that as produced was only three times heavier than air, and could be made lighter than air by evacuating the air out of its pores.

An aerogel is the intact, dry, ultralow density, porous solid framework of a gel (that is, the part that gives a gel its solid-like cohesiveness) isolated from the gel’s liquid component (which takes up most of the volume in the gel).

The term aerogel does not refer to a particular substance, but rather to a geometry which a substance can take on–the same way a sculpture can be made out of clay, plastic, paper-mâché, etc.

Aerogels can be made of a wide variety of substances, including: silica, Most of the transition metal oxides (for example, iron oxide), Most of the lanthanide and actinide metal oxides (for example, praseodymium oxide), Several main group metal oxides (for example, tin oxide), Organic polymers (such as resorcinol-formaldehyde, phenol-formaldehyde, polyacrylates, polystyrenes, polyurethanes, and epoxies),  Biological polymers (such as gelatin, pectin, and agar agar), Semiconductor nanostructures (such as cadmium selenide quantum dots), Carbon, Carbon nanotubes, Metals (such as copper and gold).

Many aerogels boast a combination of impressive materials properties that no other materials possess simultaneously. Specific formulations of aerogels hold records for the lowest bulk density of any known material (as low as 0.0011 g cm-3), the lowest mean free path of diffusion of any solid material, the highest specific surface area of any monolithic (non-powder) material (up to 3200 m2 g-1), the lowest dielectric constant of any solid material, and the slowest speed of sound through any solid material. It is important to note that not all aerogels have record properties.

By tailoring the production process, many of the properties of an aerogel can be adjusted. Bulk density is a good example of this, adjusted simply by making a more or less concentrated precursor gel. The thermal conductivity of an aerogel can be also be adjusted this way since thermal conductivity is related to density. 

Typically, aerogels exhibit bulk densities ranging from 0.5 to 0.01 g cm-3 and surface areas ranging from 100 to 1000 m2 g-1, depending of course on the composition of the aerogel and the density of the precursor gel used to make the aerogel. Other properties such as transparency, colour, mechanical strength and susceptibility to water depend primarily on the composition of the aerogel.

For example, silica aerogels, which are the most widely researched type of aerogel, are usually transparent with a characteristic blue cast due to Rayleigh scattering of the short wavelengths of light off of nanoparticles that make up the aerogel’s framework. Carbon aerogels, on the other hand, are totally opaque and black. Furthermore, iron oxide aerogels are just barely translucent and can be either rust-coloured or yellow. 

As another example, low-density (<0.1 g cm-3) inorganic aerogels are both excellent thermal insulators and excellent dielectric materials (electrical insulators), whereas most carbon aerogels are both good thermal insulators and electrical conductors. Thus it can be seen that by adjusting processing parameters and exploring new compositions, we can make materials with a versatile range of properties and abilities.

Its unique properties have made aerogel popular with a range of industries. Silicon manufacturers, homebuilding materials manufacturers and space agencies have all put aerogel to use. Its popularity has only been hindered by cost, though there is an increasingly successful push to create aerogels that are cost-efficient. In the meantime, aerogels can be found in a range of products: Wetsuits, Firefighter Suits, Skylights, Windows, Rockets, Paints, Cosmetics, Nuclear weapons.

Because of aerogel's unique structure, its use as an insulator a no-brainer. The super-insulating air pockets with the aerogel's structure almost entirely counteract the three methods of heat transfer: convection, conduction and radiation. 

Even though aerogel is still quite expensive, the good news is that studies have shown that aerogel insulation used in wall framing and hard-to-insulate areas such as window flashing can save a homeowner up to $750 per year. In addition to helping homeowners save money, aerogel insulation can significantly reduce your carbon footprint.

Companies are racing to find a way to bring costs down, but for now, aerogels are more affordable for NASA than the general public. Still, aerogels are put to use by construction companies, power plants and refineries.

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Did The Big Bang Created All The Elements In Periodic Table?

My absolute favourite fact in the universe is that we are made of dead stars. And that's literally true. The atoms in our bodies were actually created inside the cause of stars that then exploded and died or unravelled into space. And so the question about the periodic table is very interesting. What was the periodic table like at the beginning of the universe, the moment of the Big Bang?

Well, one thing Astronomers say is that it was a lot simpler. The Big Bang, when it went off, produced basically three elements. Almost everything was hydrogen. There was a little bit of helium, and a tiny, tiny little smattering of lithium as well. So those three elements were around just a couple of minutes after the formation of the universe, but nothing else.

And that's actually not a theory. That's actually something we can observe. One of the wonderful things about being an astronomer is, as you look out into space, farther and farther away, the light has taken longer to get to you. And the farthest we can see is actually back to a time only about 400,000 years after the Big Bang.

At that time, there was nothing but very hot hydrogen gas, and a little bit of helium and lithium as well. So everything larger than that, every atom more complex had to be formed inside a star. Over time, stars like the sun are pretty good, over the life cycle, at producing things like carbon and oxygen. They don't really get much more far off the periodic table than that. 

If you want to go any farther than the element, iron, you actually need a very violent explosion, a supernova explosion. The cores of very massive stars and by that, I mean stars that are 10, 20, maybe even as much as 50 times the mass of the sun, their cores are much hotter, because the gravity crushes things down and the temperature goes up many, many millions of degrees hotter than inside the sun. So these stars can actually form bigger and bigger atoms.

The hotter the temperature, the denser the core, the more you can ram things together and actually, form bigger and bigger atoms over time. But there's a very special thing that happens when you get to the atom, iron. And it's something you have actually heard about but you may never have thought of.

When people think about getting energy out of a nuclear reaction-- you've heard about fusion reactions. So like a fusion bomb, actually, takes hydrogen, fuses it together to make helium and that creates energy. The sun also runs on that particular reaction, fusing hydrogen together.

Then you also heard that there's something called fission. And this is how, say, a uranium bomb would work. A uranium nucleus has many, many particles inside it you actually get energy out of breaking it up and forming two smaller nuclei that are actually a bit denser and they hold together better. And so you get energy out of breaking them apart.

So, the element, iron, is exactly halfway between those two processes. So you have been getting energy by fusing things together until you get to iron. And iron is the first nucleus where you don't get any energy out of fusing. From anything bigger, now, you get energy out of ripping apart, fission. 

So iron is what sets off a supernova explosion. When a star tries to fuse iron together, it absorbs energy. And that's not great for the star. The core collapses. And that huge collapse creates this giant wave of heat and the formation of many, many new elements after that. So anything heavier than iron has to be created in a supernova explosion.

Now, there are some elements, heavier still, that even supernova energies don't really get up quite high enough to make. And this is something we only found out recently, in the last couple of years. Elements like gold, platinum, bismuth and all the big things, like uranium and all of the really large atoms; they have to be formed by something that seems almost preposterous, but we have observed this happening-- two neutron stars colliding.

So neutron stars are the cores of dead stars. They are super-compressed. The density of a neutron star is about a Mount Everest worth of mass in every square centimetre. So think about crushing Mount Everest into a little cube. The entire star, which is only about 10 miles across, is actually that density. And that means you have a tremendous amount of nuclear components neutrons, protons really close together. And two neutron stars collide.

When that happens, you make all of these very heavy elements up, like gold, and platinum, uranium and all the big stuff. And again, this is not something that we just know theoretically. We actually have observed this happening. Recently, we observed two neutron stars colliding. And in that single explosion, 10,000 times the mass of the Earth in gold came out of that explosion. It was tremendous. So, we definitely know where those atoms come from now. We observed that happening. 

So to recap, at the beginning of the universe, you had three elements mostly hydrogen, a little bit of helium, a tiny bit of lithium. Now we have the entire periodic table. And a lot of those are formed in stars like the sun. Anything past iron has to be formed much more violently, in a supernova explosion or in the case of very large atoms, two colliding neutron stars. And over billions of years, we have filled out the periodic table that way.

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Pulsed Plasma Thrusters

While travelling in space, one of the hardest things to do is to stop or change direction. Without anything to push against or friction to slow things down, spacecraft need to do all the hard work of changing their speed or path by there thrusters. And sometimes they do that in ways you would never expect: like by vaporizing Teflon. They are called pulsed plasma thrusters and they can use the same stuff that’s on your frying pan to make spacecraft zoom around the universe. And they have been doing it since the 1960s.

To make basically any move in space, satellites rely on Isaac Newton’s famous Third Law of Motion, which is probably on a poster in every high school physics classroom: For every action, there is an equal and opposite reaction. Put another way: throw stuff backwards and you will go forward. In fact, you can boil down every rocket design, no matter how complicated, to this basic idea. When thinking of a rocket, you might normally imagine the chemical propulsion. That’s the “fire-coming-out-the-end” kind, which uses a controlled explosion to hurl material out the back of the rocket. 

But once in space, another kind, electromagnetic or EM propulsion, also becomes available. They are not strong enough to get rockets off the ground, but they are great once you are past most of Earth’s atmosphere. These rockets work kind of like railguns, accelerating charged particles or ions, out the back with electric or magnetic fields. Today, we have all kinds of EM thrusters, but pulsed plasma thrusters, or PPTs, were the first ones ever flown in space.

They were used in 1964 on the Soviet Zond 2 mission to Mars. Like some other engines, PPTs specifically use plasma to generate thrust, instead of a random collection of ions. Plasma is a super hot substance made of charged ions and it is the fourth state of matter. In some ways, it behaves kind of like gas, because its atoms are pretty spread out. But unlike the other states of matter, plasmas can be shaped and directed by electric and magnetic fields.

To generate its plasma, PPTs eat Teflon! Which is pretty awesome. A pulsed plasma thruster places a block of Polytetrafluoroethylene what we know as Teflon between a pair of metal plates. Then, connected wires charge up those plates with electricity until it arcs through the Teflon block, set off by a spark plug. That arc delivers thousands of volts into the block, vaporizing the nearby Teflon and ionizing it into a plasma. The sudden burst of plasma effectively creates a circuit connecting the metal plates, which allows electricity to flow like it is travelling through a wire.

One neat side effect of flowing electricity is that it generates a magnetic field. And everything in the thruster is already arranged so that this field pushes the plasma out into space. At this point Newton’s third law springs into action, pushing the spacecraft in the opposite direction of the departing particles.

Well, this kind of thruster produces a very tiniest bit of motion. A pulsed plasma thruster deployed by NASA in 2000 produced an amount of force equal to the weight of a single Post-it Note sitting on your hand. Which might not seem that exciting, but it has some big implications. Like other forms of electromagnetic propulsion, these engines require a lot of electricity to run, but in exchange, they offer incredible efficiency with their fuel.

Pulsed plasma thrusters can produce up to five times more impulse or change in momentum for every gram of fuel than a typical chemical rocket. They do it very, very slowly, but they get the job done. PPTs also offer exceptional simplicity and safety. The only “moving part” is a spring that constantly pushes the Teflon block forward and without the need to store pressurized liquid or gas fuel, there is no chance of explosion. So it makes sense then that pulsed plasma thrusters were so useful back in the 1960s. Since then, their lack of power has meant that most spacecraft main engines have remained chemical. And when companies really need some kind of EM drive like for the Dawn mission to the asteroid belt they will tend to choose more sophisticated designs. But that doesn’t mean we are done with these thrusters just yet.

Recently, their extreme simplicity has made them a natural fit for the most up-and-coming field of exploration: CubeSats. CubeSats are tiny, shoebox-sized satellites designed for simple missions and built on the smallest of budgets often by research labs or universities. Earth-orbiting CubeSats seem almost tailor-made for the strengths of pulsed plasma thrusters. Lots of sunlight gives them ample electric power, but since they are so small, space and weight are at an absolute minimum. And right now, most CubeSats typically don’t have any kind of propulsion system of their own.

So one solution is micro pulsed plasma thrusters, which can weigh just a few hundred grams and measure under 10 centimetres on a side. That might not sound like much, but even a tiny amount of thrust could double the useful life of some kinds of CubeSats. They will likely need to undergo more testing and development before they are ready for primetime, but someday, we could have a whole fleet of Teflon-eating satellites.

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How Submarines Work?

In all of World War Two, the world used about 5 megatons of explosives. But now, a single American Ohio Class submarine can carry 24 Trident II missiles. Only one Trident II missile capable of carrying 12 nuclear warheads together equivalent in power to about 5 megatons of explosives. A single submarine can carry a devastating, catastrophic, inconceivable amount of firepower. While in reality due to arms reduction treaties and practicality these boats often carry far less than their maximum armament. But submarines can still creep up anywhere, undetected, ready to unleash their firepower, more powerful than the entire arsenal of some countries, in an instant.

Submarines are different in purpose to some other elements of a navy. While an aircraft carrier, for example, is intended to be big, foreboding and noticeable as a means to display a nation’s power to the world, submarines are meant to be unseen & undetected, an invisible silent force that could or could not be anywhere at any time. In a way, submarines almost serve a purpose of psychological warfare an enemy can never know for sure whether a submarine is looming off its shore.

While dozens of countries operate submarines, the most powerful and often largest of these boats are those capable of firing ballistic missiles carrying nuclear warheads. Only six nations are confirmed to have these submarines are US, UK, France, India, Russia and China. In addition, analysts have found evidence suggesting that North Korea and Israel also each have nuclear-missile capable submarines.

Nowadays, there are essentially two different types of military submarines with two different missions. The attack submarine, the most common kind, is generally smaller and attacks other close-range targets like ships using torpedoes, shorter-range missiles and other armaments. The other, often larger type of submarine are those ballistic missile submarines which essentially serve the purpose of being a mobile, hidden launch platform for nuclear missiles. The idea is that, as a stealth launch platform, a country’s submarines would survive any nuclear first strike and therefore be able to retaliate against an aggressor.

Ballistic missile submarines are therefore crucial to the idea of mutually assured destruction, if anyone attacks with nuclear weapons, assuming those attacked had nuclear weapons that would survive a strike and they retaliated, both the attacker and those attacked would be destroyed. Therefore, many consider these nuclear missile equipped submarines to actually be a form of nuclear deterrence, they say they reduce the likelihood of others using nukes since they assure their subsequent destruction.

Considering that these submarines might survive when a country and its government do not, they, therefore, need the independent authority to use their missiles. While other operators likely have similar setups, it is known that the UK’s four ballistic missile submarines each have a letter locked in a safe instructing their commander on what to do if the UK is wiped out by a nuclear strike. These letters are written by each prime minister at the beginning of their term and destroyed,  unread, at the end.

Each PM essentially has to chose which of the four potential options they want to instruct the sub commanders to do (1)nothing, (2)to place themselves under the command of an ally like the US or Australia, (3)for the commander to use their judgment,(4) or to retaliate and launch nuclear missiles at the attacker.

What gives submarines their stealth is the blanket of water. American Ohio class submarines are publicly known to be able to go down as deep as 800 feet or 250 meters. In reality, it is believed they can go much further. As soon as a submarine surfaces, though, their stealth is lost especially in today’s era of satellite tracking. Therefore, it is important that submarines can stay underwater for long periods so that can dive underwater from one side of the world to the other undetected.

Of course, almost all of the world’s ballistic missile equipped submarines are nuclear-powered meaning they have virtually unlimited range. These boat’s reactor cores only need to be swapped every few decades. In addition, most submarines have oxygen generators and desalinators so, like nuclear-powered aircraft carriers, the only thing that really limits how long they can stay deployed is their food supply.

How it works on American nuclear submarine, which works similarly to those of other countries, is that each boat has two fully staffed crews at any given time the Blue and Gold crews. The Blue crew will first man the boat while on patrol which lasts, on average, 77 days. The different submarines different patrols are scheduled so that there are always submarines deployed. Despite this long patrol period, in the US Navy at least, submarines are actually known to have the best food of any vessel. 

Food is important to morale especially considering submarine duty is one of the Navy’s toughest jobs. Of course, fresh food can only last, at most, two weeks, so the meal quality deteriorates as the weeks go by. Eventually, the only ingredients left are canned, dried or frozen. The sign of food quality deteriorating does mean that the end of patrol is coming at which time the first crew, the Blue crew, would take the boat back to either its home port or an allied overseas port.

The Gold crew will then arrive and then both crews will work to complete a turnover, restocking and maintenance period of 25 days. Then, the Blue crew will fly home for vacation and subsequent training before the cycle repeats again. Most crew members keep this cycle going for years on end. Submariners even live their days in cycles as well. They work eight hours on then have sixteen off to train, conduct maintenance, work out, eat, and sleep.

It is important that submariners have things to do in their downtime considering they will spend three months without sunlight in a metal tube, but there just isn’t much space. The mess is really the only open space not devoted to work. Submarines tend to have gym equipment but it’s not usually consolidated in one room, more often it’s just spread out in different nooks and crannies. On large Ohio-class submarines, a submariners tiny bunk is their only true personal space. On smaller submarines, like the American Virginia-class, the number of sailors exceeds the number of bunks so the most junior sailors will have to share bunks, while one works the other sleeps and vice versa, and there’s no true personal space.

Compared to many surface Navy ships, which have phones, frequent mail deliveries and even internet, communication to the outside world is limited on submarines. Each submariner is given an email address that their family can send messages to. When the submarine is able to receive communications, all these messages are then sent electronically. Onboard, the messages are all reviewed by a dedicated crew member. They check through to be sure that no information is being sent that they don’t want to be known by the sailor. For example, they might choose to not pass on information of a family death in order to not affect crew morale.

How submarines communicate, though, is complicated because they do, of course, spend months underwater. Almost all radio waves can’t travel through saltwater but submarines do need communications to receive orders. Very low-frequency radio waves, though, do penetrate water to an extent. That’s why VLF radio forms the core of submarine communication systems. Different navies have large VLF transmitters—for example, the US has ones in Maine, Washington, Hawaii, and elsewhere; India has one on its southern coast and Australia has one in Western Australia.

These VLF signals are able to penetrate the ocean and be picked up by a submarine as deep as 60 feet or 20 meters. One major disadvantage of VLF, though, is that it is very low bandwidth. It can’t even transmit real-time audio signals—the most it can do is about 700 words per minute in text formate. When deeper, some submarines also have the capability to launch buoys to shallower depths to receive signals. Submarines also typically can’t respond with VLF frequencies since they don’t have large enough transmitters so they have to rise to shallow depths so they can have antennas sticking out of the water to respond. It’s at this depth that modern submarines will often have quick transmissions with satellites in order to download and upload information. There are a few other techniques used less commonly, some new technologies under development and some separate systems designed for use when the main systems are compromised, but VLF radio forms the bulk of communications with most submarines.

But the fact that submarines spend their time underwater in stealth also makes another crucial element difficult—navigation. Both GPS and Radar don’t work underwater since they use higher frequency waves that can’t make their way through any depth of water. What does work underwater is Sonar where the submarine essentially generates a sound and then listens to when and how the sound comes back to map out its surroundings but emitting this sound makes it quite easy for others to track a submarine. Therefore, when operating in stealth conditions, submarines can’t use active sonar. 

Rather, they use an inertial navigation system. These are essentially systems of accelerometers and gyroscopes that take the last-known accurate GPS position of a submarine and then tracks the submarines movements relative to that. It uses this to estimate position but of course, as time goes on from the last reliable reading, the accuracy of this system diminishes. 24 hours after the last reading, these will drift to only about 1.15 miles or 1.85 kilometres of accuracy.

Now, this technique combined with the consultation of maps is usually fine since most of the time the ocean is a big, wide open space but there are a few objects floating below the surface that submarines could collide with—submarines. Some modern submarines are so well cloaked that another submarine just feet away might not be able to detect it.

That's what happened on the night of February 3rd, 2009 when the British Navy’s HMS Vanguard submarine felt a resounding bump while sailing in the East Atlantic ocean. It had collided with the French submarine Le Triomphant seemingly just by chance. Luckily they were going at low speed and there were no injuries but, considering both these submarines were both equipped with nuclear warheads, one can only imagine the potential consequences of a more damaging collision.

Submarines are dangerous—even in peacetime. They are designed to disappear so after something does go wrong, they often do just disappear. Many submarine operating countries have rescue submarines that can hypothetically be used to save stranded submariners by going down, latching on and shuttling sailors to the surface. But in practice, these have never really had much action. Sometimes submarines sink, their systems fai, and nobody can get to them before oxygen runs out.

As submarines become better at masking themselves submarine tracking technology is simultaneously advancing. There is some thought that there will be a time when nothing can hide in the ocean’s depths but until then, submarines are a crucial aspect of any modern navy. 

Nowadays, just as they were in World War Two, even traditional, non-ballistic-missile submarines and their torpedos are effective and deadly. One of the best ways to track submarines is also by sonar equipped submarines so it’s a situation where countries need submarines because others have submarines. That’s why there are still hundreds of them somewhere, or anywhere, ready to strike at any moment.

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Biocompatible Soft Fluidic Strain and Force Sensors For Wearable Devices

Children born prematurely often develop neuromotor and cognitive developmental disabilities. The best way to reduce the impacts of those disabilities is to catch them early through a series of cognitive and motor tests. But accurately measuring and recording the motor functions of small children is tricky. As any parent will tell you, toddlers tend to dislike wearing bulky devices on their hands and have a predilection for ingesting things they shouldn't.

Harvard University researchers have developed a soft, non-toxic wearable sensor that unobtrusively attaches to the hand and measures the force of a grasp and the motion of the hand and fingers.

The research was published in Advanced Functional Materials and is a collaboration between The Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), The Wyss Institute for Biologically Inspired Engineering, Beth Israel Deaconess Medical Center, and Boston Children's Hospital.

One novel element of the sensor is a non-toxic, highly conductive liquid solution.

"We have developed a new type of conductive liquid that is no more dangerous than a small drop of salt water," said Siyi Xu, a graduate student at SEAS and first author of the paper. "It is four times more conductive than previous biocompatible solutions, leading to a cleaner, less noisy data."

Harvard's Office of Technology Development has filed a portfolio of intellectual property relating to the architecture of novel soft sensors and is seeking commercialization opportunities for these technologies.

The sensing solution is made from potassium iodide, which is a common dietary supplement, and glycerol, which is a common food additive. After a short mixing period, the glycerol breaks the crystal structure of potassium iodide and forms potassium cations (K+) and iodide ions (I-), making the liquid conductive. Because glycerol has a lower evaporation rate than water, and the potassium iodide is highly soluble, the liquid is both stables across a range of temperatures and humidity levels and highly conductive.

"Previous biocompatible soft sensors have been made using sodium chloride-glycerol solutions but these solutions have low conductivities, which makes the sensor data very noisy, and it also takes about 10 hours to prepare," said Xu. "We've shortened that down to about 20 minutes and get very clean data."

The design of the sensors also takes the need of children into account. Rather than a bulky glove, the silicon-rubber sensor sits on top of the finger and on the finger pad.

"We often see that children who are born early or who have been diagnosed with early developmental disorders have highly sensitive skin," said Eugene Goldfield, coauthor of the study and an Associate Professor in the Program in Behavioral Sciences at Boston Children's Hospital and Harvard Medical School and Associate Faculty Member of the Wyss Institute at Harvard University. "By sticking to the top of the finger, this device gives accurate information while getting around the sensitively of the child's hand."

Goldfield is the Principal investigator of the Flexible Electronics for Toddlers project at the Wyss Institute, which designs modular robotic systems for toddlers born prematurely and at risk for cerebral palsy.

Goldfield and his colleagues currently study motor function using the Motion Capture Lab at SEAS and Wyss. While motion capture can tell a lot about movement, it cannot measure force, which is critical to diagnosing neuromotor and cognitive developmental disabilities.

"Early diagnosis is the name of the game when it comes to treating these developmental disabilities and this wearable sensor can give us a lot of advantages not currently available," said Goldfield.

This paper only tested the device on adult hands. Next, the researchers plan to scale down the device and test it on the hands of children.

"The ability to quantify complex human motions gives us an unprecedented diagnostic tool," says Rob Wood, the Charles River Professor of Engineering and Applied Sciences at SEAS, Founding Core Faculty Member of the Wyss Institute, and senior author of the study. "The focus on the development of motor skills in toddlers presents unique challenges for how to integrate many sensors into a small, lightweight, and unobtrusive wearable device. These new sensors solve these challenges—and if we can create wearable sensors for such a demanding task, we believe that this will also open up applications in diagnostics, therapeutics, human-computer interfaces, and virtual reality."

Source: Advanced Functional Materials

Also Read:-High-Resolution Genome-Wide Functional Dissection Of Transcriptional Regulatory Regions And Nucleotides In Human

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High-Resolution Genome-Wide Functional Dissection Of Transcriptional Regulatory Regions And Nucleotides In Human

Approximately 98 percent of the human genome is made up of noncoding DNA, including enhancers, promoters, and other elements that regulate gene activity. The methods for studying these regions tend to be expensive, labor-intensive, and largely low-throughput.

To really understand the functional geography of the noncoding genome, however, researchers need a way to isolate and characterize thousands to millions of regulatory DNA elements within it simultaneously, rapidly, and at high resolution. The need is great, as more than 90 percent of variants identified in genome-wide association studies of traits and disease are located in noncoding DNA.

By merging two powerful sequencing-based assays with a machine learning-based tool, a research team led by Xinchen Wang and associate members Melina Claussnitzer and Manolis Kellis in the Broad's Metabolism and Epigenomics programs, respectively, have engineered a powerful new approach for measuring individual noncoding DNA segments' ability to control gene expression, and doing so at both massive scale and high resolution called HiDRA (for High-resolution Dissection of Regulatory Activity), the approach brings together a number of widely used tools:

1.ATAC-seq (Assay for Transposase-Accessible Chromatin with high-throughput sequencing), a technique developed by Broad associate member Jason Buenrostro that looks across the entire genome for unwound, transcribable regions of DNA

2.STARR-seq (Self-Transcribing Active Regulatory Region Sequencing), an assay developed by Kellis lab alum Alexander Stark for measuring noncoding DNA segments' expression-promoting activity

3.SHARPR-RE, a machine learning algorithm based on the SHARPR tool Kellis's lab developed to analyze data from massively-parallel reporter assays.

By building on these approaches, HiDRA lets researchers create massive libraries of regulatory DNA and study their influence over gene expression at nucleotide-level resolution.

As they reported in Nature Communications, the team applied HiDRA to a blood cell line to test about seven million noncoding DNA fragments for ones that regulate gene expression, ultimately identifying 65,000. These included segments clearly marked as enhancers and promoters as well as segments lacking such marks, suggesting that the genome may harbor additional kinds of expression-controlling elements that we have yet to discover.

In addition, the team used HiDRA to examine how disease risk DNA variants in regulatory elements affect gene expression compared to variants that do not raise risk—a boon for researchers seeking to study how minute sequence variations in promoters and enhancers can impact human traits and disease states.

The team's findings suggest that HiDRA is a generalizable method for dissecting the nuances of gene regulation and the roles various functional elements play in human disease.

Source: Nature Communications https://go.nature.com/2s6BeD1

Also Read:-Extraction Of The Landau-Migdal Parameter From The Gamow-Teller Giant Resonance In Sn132

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Extraction Of The Landau-Migdal Parameter From The Gamow-Teller Giant Resonance In Sn132

In 1973, Russian physicist A.B. Migdal predicted the phenomenon of pion condensation above a critical, extremely high—several times higher than that for the normal matter— nuclear density. Although this condensation has never been observed, it is expected to play a key role in the rapid cooling process of the core of neutron stars. These city-size heavy stellar objects are so dense that on Earth, one teaspoonful would weigh a billion tons.

Recently, researchers from the RIKEN Nishina Center for Accelerator-Based Science and Kyushu University, performing an experiment at the RIKEN RI Beam Factory on a very neutron-rich tin isotope, investigated whether this process could really occur in neutron stars having the mass of about 1.4 times that of our sun. Similar investigations were conducted previously on stable isotopes, such as 90Zr or 208Pb, but this time the researchers decided to study the case of 132Sn, an isotope of tin. This doubly magic unstable nucleus has a fairly simple structure that makes the theoretical calculations easily compared to other isotopes with similar mass. Furthermore, 132Sn with its large neutron excess (it consists of 50 protons and 82 neutrons) provides better conditions than the stable isotopes for extending this study toward the pure neutron matter in the neutron stars.

A secondary cocktail beam containing 132Sn was produced by projectile fragmentation of a uranium primary beam colliding with thick a beryllium target. Then, a liquid hydrogen target was irradiated with 132Sn. Resulting in the collective excitation of the neutrons and protons of the tin nuclei, with the neutron spin and proton spin oscillating out of phase. This excitation mode, called "giant resonance," is suitable for studying the short-range interactions that, while being crucial in the onset of pion condensation, are complex and extremely difficult to measure.

According to Masaki Sasano from RIKEN Nishina Center, who is one of the first authors of this study, their result, which was published in the Physical Review Letters journal, shows that the pion condensation should occur at around two times normal nuclear density, which can be realized in a neutron star with a mass of 1.4 times that of the sun. Sasano said that in order to understand the possibility of the pion condensation fully, they plan to extend these unique studies of giant resonances to other neutron-rich nuclei that are far beyond the stability line, having large neutron-proton asymmetry.

Source:Physical Review Letters

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Freezing Copper As A Noble Metal–Like Catalyst For Preliminary Hydrogenation

As a non-noble metal, copper oxidizes more easily to a positive valence (Cu+ or Cu2+) than same-family elements Au or Ag. In general, this chemical property is mainly determined by electron structure. Can we change the chemical properties of an element by regulating its electron structure? Can Cu act as a noble metal in catalytic reactions?

A team led by Dr. Sun Jian of the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) gives a positive answer. The team's recently published paper in Science Advances shows that the electron structure of Cu can be changed, assisted by high energy plasma, making Cu exhibit significantly different catalytic behaviours than normal Cu in selective hydrogenation reactions.

The dimethyl oxalate (DMO) hydrogenation reaction, a typical multistep catalytic reaction producing methyl glycolate (MG), ethylene glycol or ethanol, was selected as a probe reaction for copper. In this reaction, the common product over supported Cu/SiO2 catalysts is one of the latter two owing to the inevitable co-existence of Cu+ and Cu0 for deep hydrogenation.

The sputtered (SP) Cu, which is bombarded by high energy argon plasma, can be "frozen" at zero valences when exposed to oxidation or reaction atmosphere at a very wide range of temperature, presenting noble-metal-like behaviours.

In DMO hydrogenation, a high selectivity (87%) towards the preliminary hydrogenation product, MG, a high-value chemical, was observed. The molecule level free energy surface in various reaction pathways by DFT calculation also verifies that "frozen" Cu0 is crucial for preliminary hydrogenation.

Source: Science Advances 

Also Read:- Testing The Paradigm Of An Ideal Glass Transition: Dynamics Of An Ultrastable Polymeric Glass

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