Answers to last issue's Do You Know?

1. I plan to become a space scientist and explore Mars. Can one create a miniature Mars at home for studying it?
Ans: An interesting question. The difficulty is in simulating the environment of Mars. The temperature there is very low, the atmosphere is very thin, and the atmosphere is carbon dioxide, very different from the Earth’s atmosphere.
Think of how it is inside the freezer of a refregirator. It’s cold, not as cold as Mars, but certainly too cold for plants to grow. We can also simulate the low pressure by taking a small jar, putting water in it, boiling the water which will drive off the air, drive away the air, fill the atmosphere with water. We then seal that small jar and cool it. The water will condense creating pressures very much like the atmosphere of Mars. So, we can create a low pressure environment, put in the freezer, now you have low pressure and cold. We want to have carbon dioxide in that as well. We could try some carbonated drink. Then as it boils, it gives carbon dioxide, we seal it, and the water condenses creating a low pressure and there is a small amount of carbon dioxide left.
Keep in mind that like on Earth, the environment on Mars is not homogeneous, with cooler poles, and a warmer equator. 
Now about things that are different with Mars compared with the Earth:
Gravity: About 0.376 g at its equator.
Atmospheric Pressure: 0.0003 ATM to 0.011 ATM (compared to 1 ATM on Earth).
Temperature changes during the day: Min temp −143 °C, average temp −63 °C, max temp 35 °C.
Length of Year: a little under 2 Earth years.
Length of Day: About 1 day, plus 37 minutes (actually, that is pretty close to that on Earth, we can probably ignore the difference).
Sunlight: About half of the sunlight as on Earth.
The hardest thing to simulate on Earth would be low gravity, especially over an extended period of time. One can simulate higher gravity using a centrifuge. In Earth's orbit, one could get low gravity, then use a centrifuge to match the Martian gravity, 0.376g almost perfectly. However, one may also decide that this factor is not vital to the experiment, and far too expensive to simulate.
Atmospheric Pressure is a major issue for life, but relatively easy to deal with using a vacuum chamber (where a pump is used to pump out the air inside to get vacuum). The Martian atmosphere varies from 0.0003 ATM on Olympus Mons's peak, to 0.011 ATM in the depths of Hellas Planitia.
Your skin will still provide a generally good moisture barrier, but the Martian pressures would be extremely desiccating. Your mucous membranes, however, would boil away, and any cracks that could develop in the skin from the dryness would also boil away.
Microbes such as Amoebas, or even most bacteria would likely have problems with such a desiccating environment. Mature Trees have a thick bark, and the trunks may be able to withstand, or adapt to the low pressures. However, they depend on transpiration to pull moisture up from the roots and out of the needles and leaves. It is quite possible that they would have extreme difficulty adapting to the Martian environment, especially since they also need to absorb carbon dioxide and release oxygen so you couldn't just paint over the leaves. Immature trees would likely be even worse off.
Perhaps you could consider the water problem as being part of the desiccating problem from the low pressure mentioned. There is likely some subsurface, and polar water, but getting and keeping it in liquid form at the equator may be problematic.
Now about the minerals. Perhaps a good comparison would be fresh volcanic ash and volcanic lava, which would be sterile, never having had life in it before. But, it may be a good source of minerals required by life.
The atmosphere is about 95% carbon dioxide, with most of the rest being Argon and Nitrogen, and less than 1% oxygen. This may actually be good. The partial pressure of carbon dioxide on Mars may actually be greater than on Earth. So, if one could deal with the low pressure desiccation, plants might be able to respire the Martian carbon dioxide without supplementation.
Atmospheric oxygen, however, is low enough that aerobic microbes, and animals would be unable to survive. We can assume that oxides are common in the rocks, so one could potentially extract oxygen from rocks. But, still animals could not survive on such low oxygen.
Anyway, the best simulation of Mars would be built in a vacuum chamber, with "new" stone, or volcanic ash and lava for a substrate. Incorporate a freezer to simulate night, and an artificial sun. One could use natural sunlight with about a 50% shade. But, it may be easier to make artificial sunlight and heat.
Overall, however, one might plan to use surface greenhouses on Mars.
Another thing to consider with life is that subsurface organisms may perhaps be transferred to Mars without modification. Establishing life would be easiest a couple of km below the surface, with liquid water, moderate temperatures, and pressures. That is, assuming that subsurface life isn't already there on Mars!

2. We were discussing Spiderman recently. Can one actually mix human and spider DNA?
Ans: Mixing DNA really depends on how the genes are spliced. If we do it randomly, probably nothing would happen. Some time ago the genes responsible for making eyes in mice was spliced into a fly. The result was a perfectly normal fly eye. Even though the coding was for making a much more complex mammal eye, the genes still made an eye that the insect would use!
The chance of making a crime fighter like Spiderman would be very small, perhaps negligibly small. A human with the ability to spin spider silk would not have it coming out of his wrists. More likely it would be in his urine, even then it would just be the proteins to *make* spider silk rather than the silk itself. Gaining the ability to climb walls is also unlikely. Spiders are really light compared to humans. The things they use to climb walls would not work for something as heavy as a person. 
Suppose we try to mix spider and human DNA; we need to consider many issues.
DNA Compatibility: With few exceptions, a single DNA sequence will code for the same protein sequence, from humans to yeast. Many proteins have "cousins" in other species, from humans to flies, so introducing a second version of the same protein is likely to cause confusion during development stage.
DNA Delivery: When a spider bites, it injects a range of toxins to kill the target. But what is now needed is a kind of retrovirus which injects a genetic sequence into a cell, which is then incorporated into the cell's DNA (rather than immediately killing the cell, like most viruses).
DNA Regulation: The new genes must be turned on in just the correct cells, and all of the normal functions of those cells must be disabled. This means turning on silk production in just the wrist region (for example). There is a complex chain of controls within a cell, and a chain of enzymes needed to process the proteins, all of which must be enabled in the right cells.
DNA-Directed Organs: At the lowest level, the silk protein monomer is fairly simple, but to generate a fiber with the right mechanical properties requires polymerisation under the right conditions and mixture of additional compounds, formed in a complex organ with many specialised cell types, under control of the nervous system. Transposing the gene for spider silk into a silkworm was more successful than into goats, since the silkworm already has the organ structure for processing the silk monomer into a fiber.
Connecting the Organs: Unlike insects, spiders have up to 5 different types of silk for different purposes, including the structural framework of a web, and tying up prey. Each type has specific mechanical and chemical properties with a different amorphous / crystalline microstructure, produced in different silk glands. Producing silk is energetically demanding, so the blood supply would need to be redirected to support it. Also, the silk is produced and stored in large sacs, ready for use. So probably the wrist and forearm would not be the best location for Spiderman's silk glands.
DNA Inheritability: Adding one protein to the genome has been shown to be inheritable in goats and silkworms. However, if the DNA for the entire silk production process were added to the mammalian genome, the extra DNA would probably distort the structure of the DNA of mammals, making it hard to inherit the entire silk production chain.
Even if all this succeeds, none of this will let you shoot jets of silk to the top of the nearest skyscraper. Even spiders let their silk waft in the breeze until it makes contact with another object, at the start of their web construction.
So the project of producing Superman needs more than spider DNA!

3. I read that over-eating can cause memory impairment in old age. Is this true?
Ans: Researchers are in the early stages of linking caloric intake to mild cognitive impairment (MCI), the stage between normal age-related memory loss and early Alzheimer's disease.
Overeating has been linked to a litany of health problems — diabetes, high blood pressure and stroke, to name a few. Memory loss, dementia and even Alzheimer's may some day be added to that list.
In 2006 researchers chose a random sample of 1,233 people ages 70 to 89 years old (none previously diagnosed with dementia) and asked them to fill out a questionnaire describing their diets over the previous year. Researchers grouped the study participants into three categories: those whose daily caloric consumption was between 600 and 1,526 calories; between 1,526 and 2,143; and between 2,143 and 6,000. Each participant then underwent a series of MRI brain scans and cognitive tests.
Correlating caloric consumption with test performance, researchers concluded the odds of having MCI more than doubled for those in the highest calorie-consuming group compared with those in the lowest calorie group. There are several caveats to these findings, however. For instance, the report did not take into account the types of food and beverages consumed nor did it examine the rate at which food was eaten throughout a day.
Now, what is mild cognitive impairment?
With MCI, the person is not demented. The person is functioning well, but when you test them on certain memory tests they do poorly as compared to others their age. In the study, a daily caloric intake in excess of 2,143 was associated with a significant chance of having MCI. If one is consuming more than 2,143 calories per day, the odds of having MCI are twice that of somebody that consumes 1,526 calories per day.

4. Every time I ride a bicycle, this question occurs to me: why are bicycles much more stable in movement than when we try to keep still?
Ans: The bicycle is partly balanced by the action of its rider who, if he feels the vehicle falling, steers into the direction of fall. This makes the path of the cycle curved. The curved trajectory generates enough centrifugal force to correct the fall. So the stability depends on the proper steering of the front wheel. If the front forks cannot swivel (if they are locked, even dead ahead), the bicycle cannot be ridden. That is why, the faster a bicycle moves the easier it is to ride (because a smaller steering adjustment is needed to create the centrifugal correction). That is also why it cannot be balanced when stationary.
Also, a bicycle pushed and released without a rider will stay up on its own, travelling in a long curve and finally collapsing after about 20 seconds, compared to the 2 seconds it would take if stationary. Clearly the machine has a large measure of self-stability.
The more sophisticated explanation invokes the gyroscopic action of the front wheel. An example of this is a rolling hoop, which indeed can run stably for just this reason. A bicycle is thus assumed to be merely a hoop with a trailer.
Why does steering geometry matter? One obvious effect is seen by wheeling a bicycle along, holding it only by the saddle-seat. It is easy to steer the machine by tilting the frame, when the front wheel automatically steers inward . This is not a gyroscopic effect, because it occurs even if the bike is stationary. A little study shows that it occurs because the center of gravity of a tilted bicycle can fall if the wheel twists out of line. So here was a new theory of bicycle stability - the steering is so angled that as the bike leans, the front wheel steers into the lean to minimize the machine’s gravitational potential energy. 

5. In its later stage of life, when fusion stops and the star gets its carbon core, does all that pressure on the carbon core produce diamonds?
Ans: The general answer to this question might be difficult, but yes, scientists have indeed found such diamond in 2004.
Twinkling in the sky is a diamond star of 10 billion trillion trillion carats, astronomers discovered. The cosmic diamond is a chunk of crystallised carbon, 4,000 km across, some 50 light-years from the Earth in the constellation Centaurus. It is the compressed heart of an old star that was once bright like our Sun but has since faded and shrunk.
Astronomers decided to call the star "Lucy" after the Beatles song, Lucy in the Sky with Diamonds. 
The diamond star completely outclasses the largest diamond on Earth, the 546-carat Golden Jubilee which was cut from a stone brought out of the Premier mine in South Africa. The huge cosmic diamond - technically known as BPM 37093 - is actually a crystallised white dwarf. A white dwarf is the hot core of a star, left over after the star uses up its nuclear fuel and dies. It is made mostly of carbon.
For more than four decades, astronomers thought that the interiors of white dwarfs crystallised, but obtaining direct evidence became possible only recently.
The white dwarf is not only radiant but also rings like a gigantic gong, undergoing constant pulsations. By measuring those pulsations, they were able to study the hidden interior of the white dwarf, just like seismograph measurements of earthquakes allow geologists to study the interior of the Earth. They figured out that the carbon interior of this white dwarf has solidified to form the galaxy's largest diamond.
Astronomers expect our Sun will become a white dwarf when it dies about 5 billion years from now. Some two billion years after that, the Sun's ember core will crystallise as well, leaving a giant diamond in the centre of the solar system.
Our Sun will then become a diamond that truly is forever!
Source: Scientific American and science sites on the internet