Tag Archives: nucleus

Why raindrops are basically sky pearls

At the center of every raindrop there is an impurity (dust, clay, etc) – basically all raindrops have something like that at its core, just like pearls do. So in a way, raindrops form just like pearls. Let’s look at this phenomenon in more detail.

Image via UCSD.

In one form or another, water is always present in the atmosphere. However, water particles are simply too small to bond together for the formation of cloud droplets. They need another substance, a ‘seed’ with a radius of at least one micrometer (one millionth of a meter) on which they can form a bond. Those objects are called nuclei, or to be more exact, cloud condensation nuclei.

Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles typically 0.2 µm, or 1/100th the size of a cloud droplet on which water can condens. There are different types of seeds; it’s usually thin particles of dust or clay, but soot or black carbon from fires can also play this role. The ability of these different types of particles to form cloud droplets varies according to their size and also their exact composition, as the hygroscopic properties of these different constituents are very different. Some particles are better than others at seeding rain, while others can be better at seeding snow or ice. Temperature actually plays a key role.

Image via NOAA.

A cloud results when a block of air (called a parcel) containing water vapor has cooled below the point of saturation. As it moves higher and higher, it moves into areas of lower pressure and it expands. This requires heat energy to be removed from the parcel. As the parcel reaches saturation temperature (100% relative humidity), water vapor will condense onto the cloud condensation nuclei resulting in the formation of a cloud droplet – if there is a seed, of course.

Phytoplankton can also play a special role in seeding rain – some have supposed that it can actually act as a regulator mechanism for rain. It goes like this: Sulfate aerosol (SO42− and methanesulfonic acid droplets) act as CCNs. Large algal blooms in ocean surface waters occur in a wide range of latitudes and contribute considerable DMS into the atmosphere to act as nuclei. According to James Lovelock, author of The Revenge of Gaia, this happens because arming oceans are likely to become stratified, with most ocean nutrients trapped in the cold bottom layers while most of the light needed for photosynthesis in the warm top layer. Under this scenario, deprived of nutrients, marine phytoplankton would decline, as would sulfate cloud condensation nuclei, and the high albedo associated with low clouds. This is known as the CLAW hypothesis, but until now, it has not yet been thoroughly confirmed.

Phytoplankton bloom in the North Sea and the Skagerrak – NASA

The take-away message is that you don’t only need water for rain – you also need a seed.

Large Hadron Collider creates mini big bangs and incredible heat

The Large Hadron Collider at CERN has taken another step towards its goal of finding the so called ‘god particle‘: it recently produced the highest temperatures ever obtained through a science experiment. The day before yesterday, 7 November was a big one at the LHC, as the particle collider started smashing lead ions head-on instead of the proton – proton collisions that usually take place there.

Representation of a quark-gluon plasma

The result was a series of what is called mini big bangs: dense fireballs with temperatures of over 10 trillion Celsius degrees! At this kind of temperatures and energies, the nuclei of atoms start to melt in their constituend parts, quarks and gluons, and the result is called a quark-gluon plasma.

One of the primary goals of the Large Hadron Collider is to go back further and further in time, closer to the ‘birth’ of the Universe. The theory of quantum chromodynamics tells us that as we ‘travel’ in the past more and more, the strength of strong interactions drops fast and reaches zero; the process is called “asymptotic freedom”, and it brought David Politzer, Frank Wilczek and David Gross a Nobel Prize in 2004.

The quark-gluon plasma has been studied in great detail at the Relativistic Heavy Ion Collider (RHIC) at Upton, New York, which produced temperatures of 4 trillion degrees Celsius. These collisions will allow scientists to look at the world in a way they never could have before, showing how the Universe was about a millionth of a second after the big bang. One can only wonder what answers this plasma has to offer, and it already produced a huge surprise, acting like a perfect liquid instead of a gas, as expected. Still, one thing’s for sure: the Large Hadron Collider is producing more and more results each month, and whether it confirms current theories or proves them wrong, science will benefit greatly from this particle collider

First Detailed Map Of Nuclear Pore Complex Made

nucleusUnderstanding the mechanisms which take place is something scientists are have been trying to figure out for ages; because of it’s small size, maping it and understanding some things seems almost impossible, but this is a very important step in solving some molecullar puzzles. This would in fact speed up significantly the process of discovering and understanding of cells.

A cell’s membrane-bound nucleus vital components so it’s vital to be very careful about what enters and leaves this important zone. In order to do this, the cell uses hundreds to thousands of nuclear pores as its gatekeepers, selective membrane channels that are responsible for regulating the material that goes to and from a cell’s DNA and the signals that tell a cell what to do and how to do it. But understanding and visualizing these processes is virtually impossible with the existing methods. But according to Rockefeller scientists which published their studies in Nature the upper image would be the first complete molecular picture of this huge, 450-protein pore.

This provides valuable information and even gives a glimpse regarding how the nucleus evolved. The computer which does the job sorted through about 200,000 different configurations of the pore’s component proteins, finding about 1,000 possible, very similar structures that fully satisfied all the thousands of restraints provided by experimental data: restraints such as which protein could be next to which, or where that large protein had to be in relation to this small one. Scientists described this situation as a huge puzzle which had to be solved.

Evolution is a process of duplication and divergence,” Rout says. He and his colleagues saw clear evidence of this when they color-coded the proteins in the pore. One method of color coding revealed alternating stripes, like spokes on a wheel: For every protein, there was another one that looked quite similar. Color coding a different way showed the same pattern in the pore’s outer and inner rings, one of which appears to be a slightly modified duplication of the other. These are evidence of duplication events, Rout says, showing that the evolution of the complicated nuclear pore was a more straightforward affair than previously thought. “It’s made of many different variations of a theme of just one unit.”