observation - Why are distant objects observed in the near infrared?

I was reading an article that explains why JWST is a successor to Hubble and not a replacement for Hubble. They explained that Hubble's science pushed astronomers to look at longer wavelength. And then they said:

In particular, more distant objects are more highly redshifted, and their light is pushed from the UV and optical into the near-infrared.

So basically to observe the first galaxies, astronomers have to observe in infrared. My question is why distant objects require observations in the infrared?

Is it because they are at a very large distance from us, so the light has lost a lot of energy on its way so it's detectable in the infrared?

the sun - Are we still going to have rainbows if Sun is replaced by another star?

Rainbows would lack most blue, and some green for red stars.
For a blue star, the blue part of the rainbow would be more intense.

For more complex colors, the rainbow may show some gaps. A rainbow is essentially a spectrum of that star light portion, which is visible to our eyes, and to which the atmosphere is transparent.

Stars vary in brightness. A blue giant would be large and glaring, a red dwarf faint.

Colors in the rainbow would be blurred, hence closer to white, for large stars, and sharper, more distinct, for small stars, according to the angular size of the respective light source.

... This all assumes, that there is still rain. With small, red stars, it would get too cold for rain. With large blue stars, Earth would heat up too much.
To adjust for these effects, the distance to the star would need to be modified.
And of course, the length of a year, and the orbital velocity may change.
This could then cause different tides, changes in volcanism, etc.

Exchanging the star could cause various other effects, too, other polar lights, effects to the ionosphere, the ozone layer, atmospheric erosion, more...

big bang theory - The Fermi paradox

I think this too broad, but I'll offer the following:

The star Kepler 444 is orbited by several small, assumed to be rocky, exoplanets. Kepler 444 is estimated to be a very old star, perhaps 11 billion years old, with a metal content of about one third that of the Sun.

Whilst the planets around Kepler 444 are small, they are too hot to be "earth like", but there appears to be no reason why planets at larger orbital radii (that are much harder to detect by the transit technique) should not be there.

Thus the answer appears to be demonstrably, at least 11 billion years ago.

However, the limit cannot be much longer than this, since a certain time must elapse between the formation of the first stars in the Galaxy to the enrichment of the interstellar medium with metals. These metals (all elements heavier than He are referred to as such) are required to build a "rocky" planet. While Kepler 444 demonstrates you don't need a solar metallicity, you still need some.

The fastest place this enrichment took place in general was in the Galactic bulge. A burst of star formation probably enriched the ISM in much less than a billion years.

Thus in principle I would say less than a billion years after Galaxy formation and this is probably not much more than 11 billion years ago.

Kepler 444

http://en.m.wikipedia.org/wiki/Kepler-444

http://adsabs.harvard.edu/abs/2015ApJ...799..170C

The second part of your question is hard. It has taken 4.5 billion years "for life like ours" to evolve. Since we don't fully understand the factors that lead to this, the only realistic answer is that it is probable that it takes another 4.5 billion years after the formation of planets for life "exactly like ours" to emerge.

evolution - What are samples of "Outlaw Genes"

I read this in a paper

Keller and Ross describe their greenbeard gene as an ‘outlaw’.
Admittedly, the comment is only made in passing, but are they correct?
In this context an outlaw is usually defined as a gene whose action
favours itself, but opposes the reproductive interests of the
individual organism. Where there are outlaws, natural selection at
different loci is pulling the organism in different directions.
Theoretically speaking, green-beard genes...

Yes: http://www.sciencedirect.com/science/article/pii/S0140175083901562

Basically loving your children is outlaw because it makes you sacrifice resources for your children. However, if your interest is defined as maximizing the number of children, then it's just your stuff working properly. Outlaw genes will be something that makes you die for a cause or stuff like that I suppose.

Space time and aging - Astronomy

Einsteins general theory of relativity explains time dilation caused by gravity-emitting objects. As one experiences more gravity, time will flow slower. That means that "standing" on jupiter, which isn't possible due to the lack of surface, will cause you to move through time faster; But you do not age slower. Suppose your Lifespan is 80 years. On Jupiter you still would live 80 years but the time that has passed on earth during your 80 years would be slightly more than that. The same counts vice versa for the moon.

atmosphere - Why argon instead of another noble gas?

Doing a bit of reading up on this, I might have an answer, though credit where credit is due, the answer isn't really mine:

https://www.reddit.com/r/askscience/comments/3wsy99/why_is_neon_so_rare_on_earth/

When the planets coalesced, it's likely that there was very little ices/gas around the inner planets when they formed and the Earth's atmosphere and water (CH4, NH3, CO2 and H20 being the 4 most common outside the frost line ices). These likely came from asteroids and meteors that formed outside the frost line and later crashed onto earth.

Neon is the 5th most common element in the milky-way but because all noble gases have very low freezing points, it's likely not be very common even on comets or meteors for the same reason that water or CO2 aren't common inside the frost line, Neon, and other noble gases likely stay free and don't collect on comets or meteors in high amounts. (I looked, but couldn't find an article to verify that).

But if comets have low noble gas content, then we have to look for an alternate source. With that in mind, and going back to the first link, Argon is produced by radioactive decay of Potassium 40 and that would explain it's relative abundance compared to the more common noble gas, Neon. Helium (Alpha particles) is also produced inside the earth and Radon is is too in small amounts but Radon also decays - that's not related to your question though.

If Argon on planets comes primarily from Potassium 40, you should expect the amount of Argon to have a roughly similar ratio to the amount of potassium on a planet and not be relative to the percentage of atmosphere. A 2nd factor, how much gets blown off the planet over long periods of time is a factor too. Venus in general should be able to retain much of it's Argon based on atomic weight (40) similar to CO2 (44), but if it loses even a tiny percentage of it's Argon over time, that would be a factor too.

Now, to see if this is possible, I should run some numbers, but I warn you, my math can be a little rusty.

Potassium is the 7th most common element in the Earth's lithosphere at about 0.26% and about 0.0117% of that Potassium is Potassium 40. Using a very rough estimate of 2.3 x 10^19th tonnes for the Earth's crust, 2.3*10^19*2.5*10^-3*1.17*10-4 = about 6.7*10^12 or 6.7 trillion tons of Potassium 40 currently in the Earth's crust. (There's probably a fair bit more in the mantle, so these numbers are rough)

With a half life of about 1.248 billion years, that's sufficient time for over 3 half lives if we start after the late heavy bombardment, which suggests a bit over 7/8ths of the original Potassium 40 in the Earth's crust has decayed into Argon 40, so there should be, given the age of the Earth and abundance of Potassium 40, a bit over 7 times 6.7 trillion tons or, lets ballpark and say a bit over 50 trillion tons of Argon that formed on earth by Potassium decay. (I'm ignoring any that might have been produced prior to the late heavy bombardment, cause I assume that could have blown some of the atmosphere off the earth or heated the atmosphere enough for the sun to blow some of it off). Also, doing a bit of research, only 11% of the Potassium 40 decays in to Argon 40, 89% undergoes beta decay into Calcium 40, so for this to work, there would need to be a fair bit more Potassium in the earth than I estimated, but that's still likely the case.

The mass of the atmosphere is about 5,140 trillion tons, and 1.288% of that (By mass, not volume) = about 66 trillion tons, so the Argon we should expect from Potassium 40 decay and the amount of Argon in the atmosphere are pretty close. Some Argon gas might have escaped and some should still be trapped inside the earth but the numbers are close enough to work and I think that's very likely the answer. It also suggests that the Earth has lost relatively little Argon to space, which also fits with the Atmospheric Escape article.

A 2nd way to look at this is that Argon 40 makes up 99.6% of the Argon in the atmosphere and Stellar Nucleosis likely wouldn't account for a ratio anywhere close to that (not a typical stellar link but Wikipedia says Argon 36 is the most common isotope). The decay of Potassium 40 does explain the 99.6% Argon40 ratio.

If we apply a similar estimate to Venus, with Venus atmosphere about 94 times the mass of Earth's, and we assume a similar amount of Argon-40 being produced in Venus' crust we could roughly expect 1.28%/60 or about 0.02% Argon by mass in Venus's atmosphere or perhaps, if the Earth lost a pretty high share of it's lighter crust elements after the giant impact, we might expect a bit more than that on Venus, perhaps 0.03% or 0.04% as a rough estimate. Using your number of 0.007%, that's lower than I calculate it should be, but Venus could have lost a higher share of it's Argon than Earth and it also might be slower to release trapped gas inside it's crust than Earth because it doesn't have plate tectonics, so the number for Venus looks "about right" too. It's the Potassium 40 in the crust. I'm convinced.

Interesting question. I learned something researching it.

galaxy - What part of the milky way do we see from earth?

Fraser Cain:

We’re seeing the galaxy edge on, from the inside, and so we see the
galactic disk as a band that forms a complete circle around the sky.

Which parts you can see depend on your location on Earth and the time
of year, but you can always see some part of the disk.

The galactic core of the Milky Way is located in the constellation
Sagittarius, which is located to the South of me in Canada, and only
really visible during the Summer. In really faint skies, the Milky Way
is clearly thicker and brighter in that region.

If you want to know more, watch this video from Fraser Cain which explains it in details:

https://www.youtube.com/watch?v=pdFWbEwsOmA

You can find your answer in the first minute

What would night sky look like if Earth was made of antimatter

It's kind of a strange question but I'll give it a shot.

It depend, kind of obviously, on how much of the "space dust" hits the earth. Estimates vary pretty widely on how much dust from space hits the Earth anyway, by this site, between 5 and 300 metric tons per day.

Lets start with the low end estimate, 5 metric tons (5,000 KG) per day. Antimatter will meet with and turn into energy an equal amount of matter, so 10,000 KG per day turned into energy, presumably almost all gamma-rays, but a lot of that energy would reflect off the upper atmosphere, lets estimate 40% of it reaches the earth, so 4,000 KG of gamma ray energy hits Earth from Space every day.

4,000 KG, * C^2 (300,000,000^2) = 3.6*10^20 joules of energy per day.

The sun (I'll just borrow from this link rather than calculate). 1.6x10^22, so, the heat from the matter-anti matter interactions would be 2% of sunlight. That would be enough to warm the earth measurably. A 2% increase in energy form space could warm the Earth several degrees, maybe 10 degrees, maybe more. The Earth would be measurably warmer, but that would be the least of our problems.

I think we can bring the number down a bit, cause you said no meteors, or asteroids, and even if you hadn't, larger objects like that in a matter-antimatter interaction, the contact would be so hot that most of the meteor wouldn't have a chance to evaporate but would simply be exploded away from the Earth, so we can round the number down quite a bit, like maybe a few hundred KG per day gets converted to gamma-rays and travels through the Earth's atmosphere and hits the Earth. At this stage, the total heat the Earth gets is negligible enough at those levels, but would the sky glow visibly at night? Honestly, I don't know, but maybe.

Gamma rays aren't visible, but as the rays pass through the atmosphere you might get enough visibly hot atmosphere/visible thermal radiation that you might see it. I don't know how to begin to calculate that, but it seems possible. The gamma ray effect would be similar to what would happen to the Earth if it was hit by a gamma ray burst (from a non lethal, but perhaps uncomfortably close distance). Here's a description of what that would be like. We'd lose much of our ozone layer and the chemical composition of our atmosphere would change. over time, it could end much of the life on the Earth's land. Life in the oceans could survive, but life on land would have a hard time.

That's not the only effect though. As a few hundred tons of antimatter hits the upper atmosphere, the upper atmosphere would heat up and the Earth would lose it's atmosphere due to higher temperature much faster. Over thousands, perhaps millions of years the Earth would lose much of it's atmosphere, which wouldn't be fun.

A final effect is that antimatter would change chemistry. If an Oxygen atom is hit it becomes a Nitrogen, if a Nitrogen is hit it becomes a carbon (I think, unless the gamma ray energy of the evaporation causes further photo-disintigration), but you'd see chemical changes as a result, perhaps some of them toxic and some radioactive isotopes. So, no ozone layer, gamma ray radiation and toxic chemicals forming in the upper atmosphere - not exactly sunshine and puppies.

Teeny-Tiny amounts of antimatter hitting the Earth isn't an issue, but in the amount you propose it would probably make the earth pretty inhospitable pretty fast.

What decided how the Kepler space telescope was pointed?

The prime objective of the Kepler mission was to attempt to find "Earth-like" planets using the transit technique.

To establish that you definitely have a transiting planet requires, at a minimum, that you see three regularly spaced transits.

The Kepler mission (originally) was planned for 4 years. Thus to ensure the detection of 3 transits for planets in a 1-year orbit really requires that you observe a large set of stars continuously for that period (since the transits are quite brief).

In order to do this, you need to observe a field in which neither the Sun nor the Earth get in the way during the year. This requires you to look away from the ecliptic plane.

Then, to get a large number of stars in the fixed field of view, a direction was chosen that was close, but not in the Galactic plane and viewing along a spiral arm. I believe this was done to maximise the number of stars with $V<16$ for which Kepler would supply good photometry. Closer to the plane would have given even more stars, but many would have been faint and one runs into more difficulties in terms of resolving which star is actually the variable when there is too much confusion with many sources.

virology - What determines when a virus becomes a "new strain"?

I don't know if this is a comprehensive enough answer, but viruses are taxonomically broken down into order (-virales), family (-viridae), subfamily (-virinae), genus (-virus) and species. This system was developed by the ICTV and is concurrently used with the Baltimore System.

A lot of species contain variations called virus strains. There are two types, serotype and genotype.

In serotypes, the differences are detected by variation in antigens. Genotypes are detected by differences in genome sequence.(1).

The reason a vaccine is difficult to create for the common cold, or upper respiratory tract infections is not only because of the frequency of mutation but also due to the large number of serotypes present.(2),(3).

1. Virology: Principles and Applications - Carter.


2. Princuples and Practice of Infectious Diseases - Mendell, et al.


3. E.g. Olszewska, et al. Development of vaccines against common colds. Br Med Bull. 2002. 62(1):99-111.

black hole - Eternally collapsing objects?

With respect to "eternally collapsing", they are probably referrring to the fact that in the reference frame of an external observer, gravitational time dilation prohibits matter from ever reaching the event horizon (the "surface") of the black hole.

Denoting the radius of the event horizon $r_mathrm{S}$ (for "Schwarzschild radius"), time runs slower by a factor of $(1 - r_mathrm{S}/r)^{-1/2}$ for an observer at a distance of $r$. As $r$ approaches $r_mathrm{S}$, this factor goes to infinity, i.e. the observer will never reach $r_mathrm{S}$

However, this is only for the external observer; the falling observer would cross the horizon and reach the center in a finite time.

With respect to "not being stable", you're probably right that they are referring to Hawking radiation which presumably makes the black hole slowly "evaporate". Near $r_mathrm{S}$, pairs of virtual particles are being created and can be turned into real particles by the gravitational field. If they avoid falling into the black hole, energy is taken away from the hole, reducing its mass.

exoplanet - Are there any Stars we know don't have planets?

I am beginning to assume that our solar system is not unique and that every star has several planets.

Not quite, but indeed a study published in Nature in 2012 found that, based on our observations so far, roughly 17% of stars host Jupiter-mass planets, 52% host "Cool Neptunes" and 62% host Super-Earths. (Note that these percentages do not add up to 100%, because they are not mutually exclusive possibilities). This was particularly surprising, because half of all visible stars are believe to be in binary systems, which would make planetary systems very unstable, but some binary systems have been found to have planets too.

So indeed it seems the majority of stars have planets, but it's very unlikely that all of them do.

However, the exact answer to your question "do we know of any stars with no planets" has got to be "no", because there remains a possibility that they have planets that we simply haven't been able to detect, because of limitations in our techniques to detect them.

stellar evolution - Why do proto stars on the Hayashi track get dimmer as they contract?

The Hayashi track has an almost constant effective temperature. The pre main sequence star (not protostar) is powered by the release of gravitational potential energy caused by its contraction.

If the star is getting smaller at constant effective temperature, then of course it's luminosity ($propto R^2 T^4$) decreases.

So perhaps your question is why do PMS stars contract at constant temperature? In other words, why is the Hayashi track almost vertical in the HR diagram? The answer to this is derived in some detail on the relevant Wikipedia page and arises from the fact that low mass PMS stars are fully convective and have atmospheric opacity dominated by H- ions.

gravity - How does an absolute horizon form before the apparent horizon?

I guess you are talking about black hole formation here. If we take the Oppenheimer-Snyder model for the spherically symmetric collapse of a star, then an event horizon forms first followed later by an apparent horizon that is at, or interior to, the event horizon.

The event horizon is the surface behind which light rays will never reach an infinite distance from the black hole. The apparent horizon is the surface behind which outwardly directed light rays will move inward.

The two will coincide for a static black hole, but for a forming black hole with a growing mass, it is possible for an outwardly directed photon to be outside the apparent horizon, but inside the event horizon, because the black hole mass is inevitably larger in the future if some of its future mass is still beyond its final Schwarzschild radius. As the event horizon forms at the centre of the star and moves outwards, then it is clear that the apparent horizon, which is always interior to the event horizon, must form later.

In the very simplified Oppenheimer-Snyder model, featuring an initially uniform star comprising of pressureless "dust", the apparent horizon first forms just as the surface of the collapsing star coincides with the event horizon and the apparent horizon is therefore always coincident with the event horizon. In more realistic models the apparent horizon forms a little earlier and then moves outwards to coincide with the event horizon as the surface of the collapsing star moves inside the event horizon.

NB: Note that whilst the apparent horizon can be defined at any point in time, the "event horizon" referred to above is a theoretical ideal, since we cannot preclude that the black hole might accrete some more mass in the future!

supernova - Stellar mass limits for Neutron Star and Black Holes

A succinct summary of supernova types is given in the following image based on Heger et al. (2003):

^{Image courtesy of Wikipedia user Fulvio 314 under the Creative Commons Attribution-Share Alike 3.0 Unported license. The graph is based on the graph in Fig. 1 of the linked paper.}

The pair instability realm is upwards of ~100 solar masses, though it is metallicity-dependent (Question 3). As Figure 1 (below) shows, neutron stars form in the mass range of >9 solar masses - again, this is metallicity-dependent (Question 1a). Starting at around 25 solar masses, black holes will form (Question 1b).

I'm not aware of ways to form an astronomical black hole or neutron star not involving a Type I or Type II supernova without resorting to speculative possibilities like primordial black holes, but that doesn't make it entirely out of the question.

resource - A good website for laymen to share their discoveries?

This is a wonderful Q&A forum, but I'm wondering if anybody knows of a good website where someone can let other people interested in astronomy know about new things that they have become aware of:

For instance: Someone could inform others about what they have found out about the latest news event (ie: gravitational waves, the "megastructure" (probably not) found by Hubble, the possible new planet discovery, etc.) Another person could inform everybody about cool websites for people interested in astronomy (ie. ADS, SIMBAD, NASA's Kepler Datapage, Astrobiology On-Line Magazine, and countless others)

I just found out that there is a series of 40 full articles in "ADS" submitted from 2007 to the present titled "The HARPS search for southern extra-solar planets". If you read them in chronological order they are not only very informative, but you can see the history and evolution of the project.

I know there are numerous websites, but I am looking for one that is serious and not just an astronomy chat room.

bioinformatics - Introductory literature for synthetic / systems biology?

I'm a computer engineer (MsC Computer Engineering) who's looking to switch into the field of synthetic / systems biology.

I've got a comprehensive layman's understanding of evolution, genetics, transcription, etc, but my academic studies have been in the areas Informatics/Comp Sci/Comp Eng/Math.

Does anyone have a good recommendation for standard literature in the field, to get me up to speed?

human biology - How do the pharmacodynamics of the NSAIDs differ and are there "resistant" COX phenotypes?

This is a draft.

How do the pharmacodynamics of the NSAIDs differ - -?

Merck's manual ch. 36 to start little bit at an introductory level:

The anti-inflammatory activity of the NSAIDs is mediated chiefly
through inhibition of biosynthesis of prostaglandins (Figure 36–2).
Various NSAIDs have additional possible mechanisms of action,
including inhibition of chemotaxis, down-regulation of interleukin-1
production, decreased production of free radicals and superoxide,
and interference with calcium-mediated intracellular events. Aspirin
irreversibly acetylates and blocks platelet cyclooxygenase, while most
non-COX-selective NSAIDs are reversible inhibitors.

and see the coming answer below.
These questions should be answered together.
To split them can be confusing.

Is there any difference in the degree to which these drugs manipulate/inhibit the enzymes (I assume their affinities for COX-1 and COX-2 are at least somewhat different)?

Please, see ch 1.03.3 in Comprehensive Natural Products II: Chemistry and Biology: 10 Volume Set:

and their conclusions about the structure

and please, see the whole chapter of the book, since its about the topic - and I think good one.

From Katzung et al.

Selectivity for COX-1 versus COX-2 is variable and incomplete for
the older NSAIDs, but many selective COX-2 inhibitors have been
synthesized. The selective COX-2 inhibitors do not affect platelet
function at their usual doses.

On the other hand, selective COX-2 inhibitors may increase the
incidence of edema and hypertension.

To varying degrees, all newer NSAIDs are analgesic, anti-inflammatory, and antipyretic, and all (except the COX-2- selective
agents and the nonacetylated salicylates) inhibit platelet
aggregation. NSAIDs are all gastric irritants and can be associated
with gastrointestinal ulcers and bleeds as well, although as a group
the newer agents tend to cause less gas- trointestinal irritation than
aspirin.

In short, there must be differences to which these drugs manipulate/inhibit the enzymes.
Please, see

• Selinsky BS, Gupta K, Sharkey CT, Loll PJ. Structural analysis of
  NSAID binding by prostaglandin H2 synthase: time-dependent and time
  independent inhibitors elicit identical enzyme conformations. Biochemistry 40, 5172–5180 (2001).

Defining the COX Inhibitor Selectivity of NSAIDs: Implications for Understanding Toxicity. Expert Rev Clin Pharmacol. 2010;3(6):769-776. And see the chapter Expert Commentary which locates at the end of the publication there:

Not withstanding the caveats on the merit of IC50 values, in vitro
analyses of COX-1 and COX-2 selectivity of NSAIDs has driven the
concept that inhibition of COX-1 explains the predominant reduction in
synthesis of mucosal protective PGs and hence gastrointestinal
toxicity of NSAIDs relative to COX-2 inhibition, which plays a role in
ulcer healin

Merck's manual chapter 36

The discovery of two cyclooxygenase isoforms (COX-1 and COX-2) led to
the concept that the constitutive COX-1 isoform tends to be
homeostatic in function, while COX-2 is induced during inflammation
and tends to facilitate the inflammatory response. On this basis,
highly selective COX-2 inhibitors have been developed and marketed on
the assumption that such selective inhibitors would be safer than
nonselective COX-1 inhibitors but without loss of efficacy.

Inflammatory processes are expressed by both COX-1 and COX-2 differently.
This means that a change in the cell membrane expresses lysosomal enzymes differently:

The cell damage associated with inflammation acts on cell membranes to
cause leukocytes to release lysosomal enzymes; arachidonic acid is
then liberated from precursor compounds, and various eicosanoids are
synthesized.

Also, the cyclooxygenase (COX) pathway of arachidonate metabolism produces prostaglandins, which have a variety of effects on blood vessels, on nerve endings, and on cells involved in inflammation. (See Merck, ch. 18)

I like the Figure 36.2 in Merck's manual.
To better answer your question, one could label the arrows there with relevant enzymes in each processes and compare those between COX-1 and COX-2 and relate to corresponding publications (only few existing!).

Adrenaline and other compounds activate the cyclooxygenase pathway, COX-1 pathway for instance, and the conversion of arachidonate to PGs and TXs. [2, p. 67]
The classic law of mass action allows to describe the reversible binding:

begin{equation}
[Protein] + [L] rightleftharpoons^{k_{1}}_{k_{-1}} [Protein-L]
end{equation}

where $L$ is ligand, Protein-L the protein-ligand complex, $k_1$ the rate constant of the forward reaction, while $K_{-1}$ the rate constant of the reverse reaction.
This fine regulation differs between COX-1 and COX-2 at enzymatic level regulated by cytokines.

COX-1 becomes only little activated in inflammation, in comparison to COX-2.
COX-2 is present in macrophages (chronic inflammation! - cytokines), fibroblasts, endothelial cells, synovial fluids, and chondriocytes.

[A]re there “resistant” COX phenotypes?

I have not heard about this that there would not be.
There are so many components in PGHSs which can develop resistances.

[A]re there any known phenotypes of COX-1 and COX-2 enzymes that are present in the general population that affect the ability of these drugs to act?

Please, see for the phenotypes of COX-1 here, while about COX-2 much less has been research, see here - no known phenotypes, see this.
Please, note also that COX has at least two isoforms: COX-1 (PGHS-1) and COX-2 (PGHS-2).

COX-1 phenotypes

Is there any evidence as to whether the the NSAIDs collect in certain areas of the body in a compartmental fashion?

No.

Each disease has its own characteristics.
Gout, for instance, has swelling of syvovial joints and usage of NSAIDs with COX-2.
My professor of abdominal surgery answered to this question directly - impossible to answer generally which I agree with her. (17.10.2014)

I think the OP has in mind some antibiotics which concentrate in some parts of the body (such as 1st generation quinolones concentrating in the renal tubules and bladder, thus exerting local antibacterial effect).
There is no similar effect with NSAIDs.

Instead, NSAIDs have local and systemic effects, not because they are concentrating in some parts of the body, but because they have several mechanisms itself.
Please, see this thread about Effect of NSAIDS on stomach.

Are there differences in fat solubility, etc., between the different drugs?

Fat burner - of course, there are differences in fat solubility between different NSAIDs.
Please, see this publication Solubility of Nonsteroidal Anti-inflammatory Drugs (NSAIDs) in Aqueous Solutions of Non-ionic Surfactants.
I will update this part next week more.

Other sources

1. Basic and Clinical Pharmacology, 11th edition, 2009, Bertram Katzung.


2. My notes during Biochemistry classes in Tartu 2011-2013

neuroscience - Why do the brains of cocaine-users shrink faster than the brains of non-cocaine users?

The mechanism of action of cocaine is dependent on pre-existing dopamine production and secretion. Normally, secreted dopamine is cleared from the synapse via the dopamine transporter (DAT) located on presynaptic dopaminergic terminals. Cocaine inhibits
this reuptake of dopamine, increasing it's duration of action on post-synaptic dopamine receptors. Thus, cocaine's effect depends on neuronal dopamine production. Without intrinsic dopamine, cocaine would have no effect. This is actual not exactly true though because cocaine also inhibits serotonin and norepinepherine reuptake transporters as well but the same argument applies to those neurotransmitters as well.

The overall effect of cocaine on the nervous system is extremely complex as it prolongs the action of dopamine, serotonin and norepinephrine wherever those reuptake transporters are present. There is a particularly high density of DAT in the basal ganglia and nucleus accumbens. What these areas of the brain normally do is under intense study and debate. The accumbens may play a role in goal directed behavior and incentive salience, which is the attribution of value to various actions or objects in the environment. This is what naturally guides us to perform one action over another. The simplistic view is that cocaine "highjacks" this system such that cocaine itself acquires greater incentive salience than natural reinforcers such as food, sex, money etc.

Getting back to the original question regarding why cocaine causes brain atrophy. This appears to be a finding quoted from a paper by the original inquirer. It is not obvious to me what the mechanism of this atrophy would be. I suggest you look at the discussion section of the paper from which that abstract was quoted to see what the authors suggest. However, to my knowledge, such atrophy has not been widely discussed in the cocaine literature but I could be wrong.

For further information see Sulzer. 2011. How Addictive Drugs Disrupt Presynaptic Dopamine Neurotransmission.

coordinate - Protocol for establishing longitudinal meridians on other heavenly bodies

When we first observe a new heavenly body (it could be a new star, asteroid, etc., but let's say a minor planet in our own solar system), are there any procedures set in place for establishing a system of longitudinal meridians? Being that a prime meridian is an arbitrary concept that you can pick and establish anywhere, is a location decided based on a physical feature, or perhaps from the first points of data we gather when making detailed observations of a heavenly body for the first time? What about heavenly bodies with no easily discernible or non-stationary features (Gas Giants)? Also does the IAU regulate this process? I have always wondered if the USSR and the US shared common reference points for locations such as on the moon.

evolution - What is the benefit for cells having the ATP production regulated in mitochondria compared to being from the nucleus?

For starters, see this thread.

My understanding is that the ancient predecessors of mitochondria were free-living unicellular organisms. Supposedly at one point, these mitochondria-like cells developed an endosymbiotic relationship with a larger cell. This relationship was advantageous for both cells: the smaller cell could focus on energy production, leaving tasks like homeostasis, nutrient collection, etc, to the larger cell. Over evolutionary time, this endosymbiosis caused the smaller cell to lose all functions unrelated to energy production, while the larger cell (as we now know it) came to rely heavily on the mitochondria for energy production.

So it's possible that at one time the nucleus encoded machinery for ATP production, but apparently the modularity and separation of function provided by this ancient symbiosis turned out to be successful.

What does the surface of Mercury look like?

The MESSENGER probe was able to take many true-color pictures of Mercury. A full list can be found on JPL's Photojournal. It is clear that Mercury is light grey in color.

In terms of the actual surface, Mercury is very similar to the Moon. It's surface is speckled with craters, with some smaller craters inside them, as can be seen in some of the images above. The smoothness varies - note the inside of the larger crater in the first picture. It's quite smooth, save the smaller crater inside it.

See also this pdf.

Is there an objective difference between space expansion and reduction in speed of light

In physics the "speed" of anything depends on the coordinate system you choose, since speed is measured as change in coordinate position in some interval of coordinate time. Even in the special theory of relativity, which doesn't take into account gravity and hence involves no spacetime curvature, the notion that the speed of light is always equal to the same constant (labeled $c$ in physics and astronomy) would only true in a special class of coordinate systems known as inertial frames, it is quite possible to define a "non-inertial" coordinate system in special relativity such as Rindler coordinates in which the speed of light does not have the same value $c$. In the general theory of relativity, which models gravity in terms of mass/energy curving spacetime, you can only have "local inertial frames" defined on very small patches of spacetime (specifically, the limit as the size approaches zero)--see this article on the "equivalence principle" for the conceptual details of how local inertial frames can be defined by observers in freefall measuring events in their immediate neighborhood (like an observer looking at events within an elevator in freefall). Such observers will always measure the local speed of light within a vacuum in their local region to be equal to $c$, regardless of the larger-scale properties of the spacetime they're embedded in, like the "expansion of space".

But if you try to define a global coordinate system on a large region of curved spacetime, this coordinate system is always a non-inertial one, so there is no guarantee that the coordinate speed of light in this coordinate system will be equal to $c$, and indeed the coordinate speed of light may vary from one region of spacetime to another depending on what coordinate system you choose (the equations of general relativity work in all smooth coordinate systems, as long as you define the metric correctly relative to your chosen coordinate system). In the basic model of curved spacetime in cosmology (the FLRW model), the simplifying assumption is made that matter is a sort of uniform fluid filling all of space, so that if you pick the right definition of simultaneity (multiple definitions are always possible in relativity due to the relativity of simultaneity), you will find that the density of this fluid is identical at every point in space at any given moment of cosmic time. This obviously isn't completely true to life, but it's expected that on large scales the density of matter is close to uniform at any given cosmic time, so it's seen as a reasonable approximation. The expansion of space basically means that the density of the fluid gets lower as time passes, and that if two objects are at rest relative to the local fluid in their immediate neighborhood, then the proper distance between them will grow with time (proper distance corresponds to what you would measure if you laid a bunch of short rulers end-to-end between the two objects at a particular moment in time, and then added up the distances).

As it happens, this cosmological model has a further nice feature (as discussed in the 'proper distance' link above which is based on this paper, see p. 99 of the 'Full Refereed Journal' link). The most "natural" coordinate system to use in this model is one in which the time coordinate corresponds to the proper time measured by a set of observers who have been at rest relative to the cosmic fluid since the big bang, and the spatial coordinate is such that the coordinate distance between any such observers at a given time corresponds to their proper distance at that time. If you use such a system, it works out that the overall coordinate velocity of any object can be broken down into a sum of two velocities:

1. The "recession velocity" at any given space, which is the velocity that an observer at rest relative to the cosmic fluid would be moving (the rate that their proper distance from the origin of the coordinate system is growing as a function of time, where we can assume the origin corresponds to our own location in space).




2. The "peculiar velocity" of any object which is not at rest relative to the cosmic fluid, which is just the same as the velocity of that object as measured in the local inertial frame of an observer at the same location who is at rest relative to the cosmic fluid. So, the peculiar velocity of a light ray must always be $c$.

So, if we know the recession velocity $v_{rec}$ at some distant location in space, then a light ray emitted directly towards us from that location will have an overall velocity $v_{rec} - c$ in this coordinate system, and a light ray emitted directly away from us will have an overall velocity $v_{rec} + c$. So from the perspective of this coordinate system, it makes sense to say as a shorthand that the light itself always travels at $c$, but space is also expanding away from us and this accounts for why the light is redshifted, and also why light originally emitted at distance $d$ won't necessarily take a time of $d/c$ to reach our own location. But this neat way of describing things is specific to both the cosmological model being assumed and the coordinate system used, things may not work out so neatly in other choices of spacetime or other coordinate systems. The only really general statement you can make about the speed of light is the one I mentioned earlier, that regardless of what global coordinate system you use and what the speed of a light ray works out to be in that system, it's always true that in a local inertial frame defined on a small patch of spacetime, light traveling through that patch always has a speed of $c$ as measured in that local frame.

genetics - Why can't we breed watermelons without any remaining seeds in the flesh?

Watermelon is just starting to come in season in the northeastern U.S., and having a seedless watermelon is convenient. The only downside is, the "seedless" almost always still have the immature, sterile white seeds in them.

What is the mechanism for breeding these watermelons so that only these white seeds remain? What is the genotype that results? Could the genetics be modified so that there are virtually no seeds (short of any minor aberrations) left in the flesh of the fruit?

solar system - 9th planet location?

It's too dim to be seen during a normal survey during the majority of its
orbit.

Update: Scientists at the University of Bern have modeled a hypothetical 10 Earth mass planet in the proposed orbit to estimate its detectability with more precision than my attempt below.

The takeaway is that NASAs WISE mission would have probably spotted a planet of at least 50 Earth masses in the proposed orbit and that none of our current surveys would have had a chance to find one below 20 earth masses in most of its orbit. They put the planets temperature at 47K due to residual heat from formation; which would make is 1000x brighter in infrared than it is in visible light reflected from the sun.

It should however be within reach of the LSST once it is completed (first light 2019, normal operations beginning 2022); so the question should be resolved within a few more years even if its far enough from Batygin and Brown's proposed orbit that their search with the Subaru telescope comes out empty.

My original attempt to handwave an estimate of detectability is below.
The paper gives potential orbital parameters of $400-1500~textrm{AU}$ for the semi major axis, and $200-300~textrm{AU}$ for perihelion. Since the paper doesn't give a most-likely case for orbital parameters, I'm going to go with the extreme case that makes it most difficult to find. Taking the most eccentric possible values from that gives an orbit with a $1500~textrm{AU}$ semi-major axis and a $200~textrm{AU}$ perihelion has a $2800~textrm{AU}$ aphelion.

To calculate the brightness of an object shining with reflected light, the proper scaling factor is not a $1/r^2$ falloff as could be naively assumed. That is correct for an object radiating its own light; but not for one shining by reflected light; for that case the same $1/r^4$ scaling as in a radar return is appropriate. That this is the correct scaling factor to use can be sanity checked based on the fact that despite being similar in size, Neptune is $sim 6x$ dimmer than Uranus despite being only $50%$ farther away: $1/r^4$ scaling gives a $5x$ dimmer factor vs $2.25$ for $1/r^2$.

Using that gives a dimming of 2400x at $210~textrm{AU};.$ That puts us down $8.5$ magnitudes down from Neptune at perihelion or $16.5$ magnitude. $500~textrm{AU}$ gets us to $20$th magnitude, while a $2800~textrm{AU}$ aphelion dims reflected light down by nearly $20$ magnitudes to $28$ magnitude. That's equivalent to the faintest stars visible from an 8 meter telescope; making its non-discovery much less surprising.

This is something of a fuzzy boundary in both directions. Residual energy from formation/radioactive material in its core will be giving it some innate luminosity; at extreme distances this might be brighter than reflected light. I don't know how to estimate this. It's also possible that the extreme cold of the Oort Cloud may have frozen its atmosphere out. If that happened, its diameter would be much smaller and the reduction in reflecting surface could dim it another order of magnitude or two.

Not knowing what sort of adjustment to make here, I'm going to assume the two factors cancel out completely and leave the original assumptions that it reflects as much light as Neptune and reflective light is the dominant source of illumination for the remainder of my calculations.

For reference, data from NASA's WISE experiment has ruled out a Saturn-sized body within $10,000~textrm{AU}$ of the sun.

It's also likely too faint to have been detected via proper motion; although if we can pin its orbit down tightly Hubble could confirm its motion.

Orbital eccentricity can be calculated as:

$$e = frac{r_textrm{max} - r_textrm{min}}{2a}$$

Plugging in the numbers gives:

$$e = frac{2800~textrm{AU} - 200~textrm{AU}}{2cdot 1500~textrm{AU}} = 0.867$$

Plugging $200~textrm{AU}$ and $e = 0.867$ into a cometary orbit calculator gives a $58,000$ year orbit.

While that gives an average proper motion of $ 22~textrm{arc-seconds/year};,$ because the orbit is highly eccentric its actual proper motion varies greatly, but it spends a majority of its time far from the sun where its values are at a minimum.

Kepler's laws tell us that the velocity at aphelion is given by:

$$v_a^2 = frac{ 8.871 times 10^8 }{ a } frac{ 1 - e }{ 1 + e }$$

where $v_a$ is the aphelion velocity in $mathrm{m/s};,$ $a$ is the semi-major axis in $mathrm{AU},$ and $e$ is orbital eccentricity.

$$v_a = sqrt{frac{ 8.871 times 10^8 }{ 1500 } cdot frac{ 1 - 0.867 }{ 1 + 0.867 }} = 205~mathrm{m/s};.$$

To calculate the proper motion we first need to convert the velocity into units of $textrm{AU/year}:$

$$205 mathrm{frac{m}{s}}; mathrm{frac{3600 s}{1 h}} cdot mathrm{frac{24 h}{1 d}} cdot mathrm{frac{365 d}{1 y}} cdot mathrm{frac{1; AU}{1.5 times 10^{11}m}} = 0.043~mathrm{frac{AU}{year}}$$

To get proper motion from this, create a triangle with a hypotenuse of $2800~textrm{AU}$ and a short side of $0.043~textrm{AU}$ and then use trigonometry to get the narrow angle.

$$sin theta = frac{0.044}{2800}\ implies theta = {8.799×10^{-4}}^circ = 3.17~textrm{arc seconds};.$$

This is well within Hubble's angular resolution of $0.05~textrm{arc seconds};$ so if we knew exactly where to look we could confirm its orbit even if its near its maximum distance from the sun. However its extreme faintness in most of its orbit means that its unlikely to have been found in any survey. If we're lucky and it's within $sim 500~textrm{AU},$ it would be bright enough to be seen by the ESA's GAIA spacecraft in which case we'll located it within the next few years. Unfortunately, it's more likely that all the GAIA data will do is to constrain its minimum distance slightly.

Its parallax movement would be much larger; however the challenge of actually seeing it in the first place would remain.

gravity - What if we throw two solid objects parallel in space? Do those two objects have any chance to collide with each other?

It all depends on the direction you "throw them" and the space-time they find themselves in.

Case 1 - in a perfectly empty universe (other than your footballs) the two would eventually collide. It doesn't matter what initial velocity you give them. The only thing that matters is there separation and their mass. You can just use Newtonian gravity to compute the two footballs' acceleration toward one another -- and hence the time for them to collide.

Such an 'empty' universe as above is called a Minkowsky space-time.

If you put these footballs on a trajectory into our real universe, well we know that space-time is curved by the matter/energy (just energy density in general) that occupies it. Hence a trajectory that starts out parallel will invariably end up "not parallel". The balls will either collide or diverge depending on the geometry of the space-time they find themselves in. The "geometry of the space-time" is (again) completely dependent on the distribution of "stuff" (matter/energy) in the universe as related to the location of the footballs.

In short, the footballs will follow the geometry of the space-time they find themselves in. That geometry (in our real universe) means they will not remain on parallel paths.

water - Can a comet orbit a planet?

Its very unlikely for a comet to become a satellite of an inner solar system planet. Much less likely than it is for an asteroid. Most asteroids are on fairly circular orbits, and so the relative velocity between asteroids and planets is quite low. In comparison comets have very elliptical orbits, and their relative velocities to the planets are much larger.

For an asteroid to be captured it must lose momentum. This is possible, though rare. For example, a binary asteroid can be captured if it is separated by tidal forces. For an comet with much more momentum, the chance of being captured is much much lower. Asteroids are captured by the Earth moon system, but not into stable orbits, they don't stay long.

If it did occur, the comet would still be active, with a coma of gas, which would be visible just like a very nearby comet. It wouldn't be particularly bright, since the surface brightness of a comet doesn't depend on distance from the Earth.

Over time the comet would run out of volatiles and become more or less indistinguishable from a captured asteroid. If it were in the Earth's orbit it probably wouldn't last that long, as there are not many orbits that are stable in the long term around the Earth, due to perturbations from the moon.

The dust and gas, including water vapour, will initally remain in orbit, forming a faint ring. It will, over time, be disrupted, and either end up in the atmosphere, on the moon, or ejected from the system. A comet doesn't contain enough water to make a difference to the Earth's ecosystem.

planet - Is there any real evidence to prove or disprove the existence of alien civilizations?

Is there any REAL proof that alien civilizations exist in outer space?

No.

What if someone would say that Earth is the only inhabited planet in the whole Universe, how would you respond?

Depends on what their goal is. If their goal is to convince me of that, I'd just try to avoid the conversation. If their goal is to come to an understanding of the current body of scientific knowledge on the matter, I'd talk about how we don't know that that statement is true.

I need to write a 5 paragraph argumentative essay to prove that alien civilizations exist. I need to write an introduction, 3 paragraphs supporting my statement that aliens exist, and a conclusion. In each of the three "body" paragraphs I need to describe in detail a piece of evidence supporting my claim.

That will be difficult, given that there is no such proof. Best you could do is argue that alien civilizations likely exist, given a certain set of assumptions.

I don't even know where to start. I mean, I want to find out the opinion of some scientists who think that we are alone, and then disprove their claim in my essay.

That is not a good goal for an essay. Don't start with the goal of disproof. Start with the goal of understanding.

I need to know the latest scientific evidence on the existence of alien civilizations. I don't mean like alien abduction stories or any of that science fiction stuff. I need some real proof that will be convincing and not undermine my argument.

Look at the Drake Equation and recent research that concludes that there are many planets in the galaxy.

How can you know for sure if there are alien civilizations in outer space?

You would need observational evidence.

What do they look like? On which planets do they live? What kind of technology do they use?

All unknown.

Why are we not alone in the Universe?

This question presumes the conclusion that we are not alone. We might be alone.

What evidence disproves the claims of Earth chauvinists?

None.