Mars night sky - how many stars visible?

I'll add to Wayfaring Stranger's comments. In fact most of the time you would be able to see fewer stars in the night sky of Mars, than in a good dark night sky on Earth, because of dust obscuration.

Even in favourable conditions, the optical depth of the Martian atmosphere is usally somewhere between 0.5 and 1 per airmass. (Petrova et al. 2012; Lemmon et al. 2014) and is nearly wavelength independent. This corresponds to a reduction in flux to between 37% and 60% of its value above the atmosphere. This compares to a typical optical (V-band) extinction of around 0.1 magnitude at a good site on Earth, which allows 90% of the flux through. There are times when it can be much worse than this on Mars.

This means that the limiting magnitude on Mars would be somewhere between 0.44 and 0.96 magnitudes brighter than it is on a dark site on Earth and that all the stars would be fainter by these values.

As a rough guide to the effect this has I took the Hipparcos catalogue and made a frequency histogram of V-magnitude of the stars. If we define a Hipparcos magnitude of 6 as the limit you can see from a good dark site on Earth, then you would see 4559 stars (that's over the whole of the sky in both hemispheres). If that limit was reduced to 5.56 or 5.04, then this number decreases to 2745 or 1560 respectively. Thus there would be a reduction in the number of stars you could see by typically between a factor of 1.66 and 2.92.

solar system - What wavelength to best detect the "9th planet"?

There are two basic ways to detect such an object. First is to detect it through reflected sunlight. Second is from the heat that it produces. We already know that the reflected light of such an object likely would be around a 16.5 magnitude. To determine the infrared, we have to estimate the temperature

The temperature very much depends on the composition. For simplicity, let's assume a composition similar to Earth, and was created about the same time as the rest of the Solar System. These assumptions may not prove to be valid, but they are among the possibilities discussed. Earth's internal heat, in fact, is at least 50% from radioactive decay, according to Scientific America. Of course, that's the internal heat only, not all of that will make it to the surface.

This proposed planet is somewhat akin to a "Rogue Planet", where a small disk of gas collapsed into a planet without a star, or were ejected from their host system. A fair bit also depends on if there is a sizable moon of the object. If so, then tidal heating would dramatically increase the temperature of the object. Any such determination can't be made without observation, but it is possible. An atmosphere would also help to keep the planet from freezing. A paper for detecting rogue planets comes from Abbott and Switzer. They hypothesis that a 3.5 Earth Mass object could be detected if it comes within 1000 AU, specifically in the far infrared, with a surface temperature of about 50 K.

Bottom line, it would probably be wise to try to detect both in the far infrared, as well as the visible, although it might be difficult to detect, even then. Given parallax as the primary means of motion, the detection should be done at several points in Earth's orbit, probably the same spot should be searched about 90 days apart to give the maximum opportunity to move, as parallax would only be visible if the motion of the Earth was perpendicular to the location of the object.

biochemistry - Why 22 amino acids instead of 64?

With only 2 nucleotides per codon, a codon could only encode 16 amino acids (actually just 15, because you need at least one stop codon), which isn't enough to encode the 20 acids we require (actually 21). So 3 is the bare minimum. (Of course another option would have been to introduce two new nucleotides, but evidence suggests that just using 3 nucleotides per codon was easier)

Nature has a tendency to minimize everything (except entropy :D). And apparently evolution selected those who understand that:

Simplicity is the ultimate sophistication.
- Leonardo da Vinci

Perfection is finally attained not when there is no longer anything to add, but when there is no longer anything to take away.
- Antoine de Saint Exupéry

It's rather safe to assume that the 20 acids we use are the bare minimum we require to function and that's why we don't have more.
Ultimately, RNA/DNA is there to store amino acid sequences. So the number of nucleotides in a codon is determined by the number of acids that need to be encoded and not the other way round.

molecular biology - What is the fastest way to build an alanine scanning library?

The fastest will change as time passes and better technologies are developed.

I think the fastest method existing at the moment is Shotgun Mutagenesis (provided by Integral Molecular Inc).

This does not employ any new method of doing that. They just provide a set of plasmids, that has all the possible mutations. The set itself is generated by automated DNA synthesis.

So if you don't have a DNA synthesizer with you then simply order the kit from the company.

microbiology - How to understand influenza strain designations?

The sub-type is named for the broad classes of the hemagglutinin (HA) or neuraminidase (NA) surface proteins sticking through the viral envelope. There are 16 HA sub-types (designated H1 - H16) and 9 NA sub-types (designated N1 - N9). All of the possible combinations of these influenza A subtypes infect birds, but only those containing the H1, H2, H3, H5, H7 and H9 and the N1, N2 and N7 surface proteins infect humans, and of these, so far, only H1, H2, H3 and N1 and N2 do so to any extent.

Read more: http://www.fluwiki.info/pmwiki.php?n=Science.NamingInfluenzaViruses

neuroscience - Is it possible for any animals today to have more than one brain?

To some degree the answer depends on your definition of what counts as a brain.

Bilaterally symmetrical organisms tend to have some level of cephalization, which involves the concentration of sensory and inter-neurons at one end of the organism (the head).

This aggregation of neurons at the head is typically more complex than aggregations of neurons elsewhere in the body and so it gets designated as a brain whereas the others are designated as ganglia (if they are outside the central nervous system or nuclei if they are within the central nervous system).

In vertebrates, cephalization is very well developed so the brain is typically much more complex than the ganglia (although the enteric nervous system is pretty awesome, its not the brain). However in many invertebrates, the ganglia at the head of the organism (its brain) is not much more complex than the other ganglia around the body.

For this reason, many invertebrates can survive decapitation (at least for a while) and some like the flat worm, can famously survive and regenerate their head after decapitation.

spectra - Reference for broader spectral lines?

Both potassium (766.5+769.9 nm) and sodium (818.3+819.4 nm) have strong resonance lines (doublets) in this part of the spectrum. There are also the calcium triplet lines at 849.8+854.2+866.2 nm.

These are the strongest atomic absorption lines seen in the spectra of solar-type stars or cooler at 700-900 nm.

A more specific answer would require the spectral type of the star.

To do something more general and/or extensive you would need to get hold of a good line list (a line list alone cannot easily tell you which lines will appear strongest in a stellar spectrum) and a spectral synthesis programme like SME or MOOG.