Science News
Headlines
. New plastic that degrades in sea water
. Nutrients from sewage may harm coastal ecosystems
. Some bacteria can gobble up electricity
. The Parker Solar Probe is the first spacecraft to visit the sun’s atmosphere
. How sleep may boost creativity

Read more details below.

. New plastic that degrades in sea water
Plastics were invented just about a hundred years ago. Imagine a world in which there were no plastics. Buckets were made of (galvanised) iron, containers were made of metal or glass, and certainly no-one could buy food in a throw-away container! In just a hundred years, plastics are everywhere and we cannot do without them. But what do you do with plastic once its use is over? Broken buckets, containers, etc., can be melted down and re-made. But what about the plastic in computers, phones, washing machines, or even the bag you buy fruits and vegetables in. These get put into the garbage and either they are again dumped into landfills, or they get washed into the sea.
Most plastics take centuries to fully degrade in the ocean. That’s one reason plastics make up 80 percent of ocean trash. But that may change. Scientists have just designed a new plastic that can break down in sea-water within weeks, not even decades or centuries. To understand this, let us understand what plastics are usually made of.
Plastics and polymers
Plastics are polymers. That is, they are long chains of molecules, with repeating units. Each unit is called a mono-mer and the chain is called poly-mer. DNA in our cells is a natural polymer, but many synthetic polymers exist, which are used to make various products from clothes to machinery. This structure makes them strong and highly elastic, so that they do not have rigid shapes, unlike metals.
Traditional plastics ultimately break down in the presence of sunlight into smaller and smaller pieces. Plastic water or soft drink bottles, for instance, require approximately 450 years to decompose! Remember that the next time you buy one! Even if they do break up, the smaller pieces of plastic are just as harmful to the sea creatures.

Polylactide
In the 1930s, scientists created a plastic using natural corn and potato starch, called polylactide, or PLA. It was hoped that PLA would quickly break down in the environment. PLA was found to degrade quickly in compost pits, so it became very popular as use-and-throw plates and spoons. Unfortunately, it did not degrade in sea water. Even after three years in ocean water, PLA remains largely unchanged.
Timo Rheinberger from the Netherlands worked on modifying the joins in PLA so that they would break down sooner. Specifically, they weakened the links that joined up to 15 percent of a PLA’s monomers. Then, they soaked their samples in artificial seawater and measured how fast these modified PLA broke down.
As the team had hoped, seawater attacked the weakened links between monomers, ripping the polymer chain apart. The more breaking points the researchers added to the polymer, the faster the PLA broke down. When they weakened 15 percent of PLA’s monomer links, the polymer broke down entirely within just two weeks. When they weakened only 3 percent of the links, the breakdown took about 2 years. This suggests the team can design how quickly PLA will break down in water by adjusting how many weakened links it has. How did they get this idea? They were inspired by nature.
All living things contain DNA and RNA. Together, these molecules help make and operate living things. DNA stores the instructions. RNA uses those instructions to make things. Like PLA, both are polymers. But they are made of different monomers.
Since DNA is the ultimate instruction manual, it is made to last. RNA is not. Its molecules have a short life, since each RNA molecule is made for one job. When it’s done, the RNA breaks down, freeing its monomers for re-use. Rheinberger realised that groupings of hydrogen and oxygen atoms — called hydroxyls — are where the RNA breaks down. So he used these hydroxyl groups to link some of PLA's monomers. These are the weak links in the chain that cause the modified PLA to break down so quickly.
Of course, there are a lot more things to study. The plastic must not become so weak that it cannot be used for its original purpose. Also, they need to test the material in natural sea water. Of course, they also need to first produce a lot of the new material before they can test it. But it is exciting to think that there is a solution to the problem of plastic disposal in the near future.

. Nutrients from sewage may harm coastal ecosystems
Scientists knew for a long time that excess nutrients, such as nitrogen and phosphorus in fertilisers, wash off with excess water instead og staying in the soil. Ultimately, this ends up in the ocean.
Now, a new study looks at nitrogen from sewage in towns and cities. This comes mainly from human excrement, such as poop and pee. They studied the effect of this excess nitrogen due to excess nutrients, called eutrophication. This causes oxygen levels to decrease and so can harm or kill fish and other sea creatures. The impact is more widely seen in coastal areas which are already stressed due to climate change and pollution.
Coral reefs and seagrass beds are important ecosystems that are home to many creatures. Researchers at the University of California, Santa Barbara wanted to explore which coastal areas receive the most nitrogen and determine the risks to these key ecosystems. So they created a computer model. But there were many difficulties in finding the right inputs.
For instance, a study of the nitrogen content of sewers should be a good indication of the problem. But there are many places which do not have sewers! But the population and distribution of population across the world is well known. So the scientists studied what people eat around the world. Most nitrogen in waste water comes from protein. So by estimating how much protein people ate, they made a guess as to how much nitrogen is being excreted.
In many places, the reverse happens. Waste water and sewage is treated to remove nutrients such as nitrogen. So they had to account for this as well.
The researchers combined this data with a high-resolution map of watersheds worldwide. That showed where the nitrogen flows. Overall, they found that waste water that runs into the sea brings with it about 6.2 million tons of nitrogen. That’s equal to about 40 percent of the nitrogen that comes from agriculture, which was simply unexpected.
The new results suggest that 58 percent of coral reefs and 88 percent of seagrass beds receive wastewater nitrogen. See the figure for the global hot spots; India is certainly one. The model allows researchers to zoom in on specific areas. This could help guide conservation efforts, the authors suggest.

. Some bacteria can gobble up electricity
Bacteria are turning out to have more and more capabilities. Some can transform toxic materials into harmless sludge. Some can grow almost everywhere. A bacterium called Shewanella oneidensis can do both. But this microbe also has a much rarer superpower: It absorbs and produces electricity. In fact, new research suggests, these bacteria may be able to use energy collected from wind or solar sources to make fuels to run vehicles.
Electrons are negatively charged particles. A moving stream of them creates an electric current. Scientists already knew that Shewanella can move electrons back and forth across its cell wall. But they didn’t know exactly how the microbes controlled their current.
Annette Rowe from Ohio, USA, found that “the pathway for getting the electrons in and out of the cell is like a wire.” It allows current to flow from the inside to the outside and the other way around. The cell could store the energy to use later.
Rowe knew that Shewanella’s cellular “wire” had to be controlled by genes. But which ones?
Buz Barstow, Cornell University, USA, had made a list of nearly 4,000 of this bacterium’s genes. Within a cell, a gene can deleted. For the new study, Rowe and her colleagues tested groups of bacteria with groups of deleted genes. Their goal: to see which deleted genes allowed the bacteria to pull in electrons. These were likely genes involved in making the cell’s “wire.”
They grew the different bacteria on glass covered by a thin metal film. Then they attached a wire to the bacteria. When they sent an electric current through the wire, they could measure how much the bacteria absorbed or added. If electrons didn’t flow, the scientists knew the deleted genes must have been the ones needed for electron flow.
They found five such genes that Shewanella apparently uses to absorb electrons. Each gene tells the cell how to make a certain protein. Some of those proteins likely “grab” electrons and bring them into the cell. Others may send signals within the cell that guide the process. Still others can likely expel electrons from the cell.
Scientists see many ways to use electric microbes. One would be to make biofuels, which are an alternative to fossil fuels. The microbes don’t need dangerous metals, as a normal battery would. However, working with living organisms is complicated, and there may be ways to store energy that are much more efficient.

. The Parker Solar Probe is the first spacecraft to visit the sun’s atmosphere
The Sun is 147.22 million km away from us. For the first time, a spacecraft has made contact with the sun. During a recent flyby, NASA’s Parker Solar Probe entered the sun’s atmosphere. “We have finally arrived,” Nicola Fox, director of NASA’s Heliophysics Science Division in Washington, D.C., said. “Humanity has touched the sun.”
Parker is still many millions of kilometres away from the Sun. Why was this statement made, then? Parker has crossed the Alfvén critical surface. What is this surface?
We know that the Sun sends out steady streams of plasma (ionised gas). This plasma is so hot that at some point the most energetic charged particles can escape from the Sun's gravity and fly away, out into space. We call this plasma the solar wind because it blows out away from the Sun. The solar wind not only reaches the Earth, but also blows past all the planets and beyond. The Alfvén critical surface marks where packets of plasma can separate from the Sun and become part of the solar wind.
The solar wind can damage Earth's communication systems and satellites. So there is a lot of interest in understanding how this is created, at the Alfvén critical surface. Parker found the surface to be about 13 million kilometers above the Sun’s surface.
The Alfvén critical surface also may hold the key to one of the biggest solar mysteries: why the sun’s corona, its wispy outer atmosphere, is so much hotter than the sun’s surface. When you have water boiling in a saucepan, the air immediately around it is hot, and then it gets cooler and you go further away. But the Sun’s corona is at more than a million degrees Celsius, while the Sun's surface is only a few thousand degrees.
In 1942, physicist Hannes Alfvén proposed a solution to the mystery: A type of magnetic wave might carry energy from the solar surface and heat up the corona. Such waves were observed in the lower corona in 2009, but they didn’t carry enough energy to explain all the heat. Solar physicists have suspected that what happens as those waves climb higher and meet the Alfvén critical surface might play a role in heating the corona. But until now, scientists didn’t know where this frontier began.
As Parker crossed the invisible boundary, its instruments recorded a marked increase in the strength of the local magnetic field and a drop in the density of charged material. Out in the solar wind, waves of charged particles gush away from the sun. But below the Alfvén critical surface, some of those waves bend back toward the surface of the sun. The surface is not just a line, but has some structure to it. Perhaps this will influence the solar wind. The study is on-going.

. How sleep may boost creativity
Prolific inventor and catnapper Thomas Edison was rumored to chase those twilight moments. He was said to fall asleep in a chair holding two steel ball bearings over metal pans. As he drifted off, the balls would fall. The ensuing clatter would wake him, and he could rescue his inventive ideas before they were lost to the depths of sleep.
Delphine Oudiette at the Paris Brain Institute and colleagues brought 103 healthy people to their lab to solve a tricky number problem. The volunteers were asked to convert a string of numbers into a shorter sequence, following two simple rule.
The volunteers were not told that there was a trick to finding the solution: The second number in the sequence would always be the correct answer! Once a participant discovered this short-cut, they could solve the problem very quickly.
After doing 60 of these trials on a computer, the volunteers earned a 20-minute break in a quiet, dark room. They were asked to close their eyes and rest or sleep if they desired. All the while, electrodes monitored their brain waves.
About half of the participants stayed awake. Twenty-four fell asleep and stayed in the shallow, fleeting stage of sleep called N1. Fourteen people progressed to a deeper stage of sleep called N2.
After their rest, participants returned to their number problem. The researchers saw a stark difference between the groups: People who had fallen into a shallow, early N1 sleep were 2.7 times as likely to spot the hidden trick as people who didn’t fall asleep, and 5.8 times as likely to spot it as people who had reached the deeper N2 stage.
So it appears that people who had drifted off into a light sleep had better problem-solving power. The results help demystify the fleeting early moments of sleep and may even point out ways to boost creativity.
Such drastic differences in these types of experiments are rare. The researchers also identified a “creative cocktail of brain waves,” that seemed to accompany this twilight stage — a mixture of alpha brain waves that usually mark the relaxation phase, mingled with the delta waves of deeper sleep.
The study doesn’t show whether thinking about the problem cause N1 sleep, or whether N1 sleep allowed them to solve the problem better. More work is needed to untangle the connection between N1 and creativity. But perhaps it may be possible to produce creativity on demand.
Sources: Science News, Science News for Students, NASA, Wikipedia