zoology - If I put a cup over a spider, and leave it there for a day, will the spider survive?

To answer the first part of your question: it is extremely unlikely that the spider will die or be weakened after just one day.

Wolf spiders (Lycosids) are all predators. Due to variations in prey populations, and low efficiency of consumption at higher trophic levels, they are subject to inconsistent and unpredictable food supply (Greenstone and Bennett, 1980). They are very well adapted to this lifestyle and consequently, long periods of starvation often yield no behavioural changes (Persons, 1999). It is highly unlikely that the spider will die after just one day: Anderson, (1974) observed no changes in activity after starving Lycosa lenta (a species of wolf spider) for 30 days; and Tanaka and Ito, (1982) observed Pardosa astrigera (another species of wolf spider) living for up to 54 days of starvation. Age and sex of the spider are more likely to affect its behaviour and performance than food or oxygen availability (Persons, 1999).

As for oxygen consumption, Greenstone and Bennett, (1980) measure an oxygen consumption of 100µL/hr for wolf spiders. Assuming that your cup is of the size of the unit of volume of the same name, the cup (~0.237L), a small calculation (see figure) shows that there will be enough oxygen for the spider to survive for over 98 days. The oxygen concentration within the cup may decrease as it is used by the spider, however this is likely to have a minimal effect as a cup placed on a surface is unlikely to be hermetically sealed.

In short, oxygen availability is unlikely to have an effect on the spider before other limitations (such as food) are reached. However neither of these effects are likely to cause behavioural changes during the first month.

References

• Anderson, J.F., 1974. Responses to Starvation in the Spiders Lycosa Lenta Hentz and Filistata Hibernalis (Hentz). Ecology, 55(3), pp.576-585.


• Greenstone, M.H. & Bennett, A.F., 1980. Foraging Strategy and Metabolic Rate in Spiders. Ecology, 61(5), pp.1255-1259.


• Persons, M.H., 1999. Hunger effects on foraging responses to perceptual cues in immature and adult wolf spiders (Lycosidae). Animal Behaviour, 57(1), pp.81-88.


• Tanaka, K. & Itô, Y., 1982. Decrease in respiratory rate in a wolf spider,Pardosa astrigera (L. Koch), under starvation. Researches on Population Ecology, 24(2), pp.360-374.

What is Curved DNA? - Biology

I'm hardly an authority on this topic, but I distinctly recall an amazing report the mid-1990s of the co-crystal structure the yeast TATA binding protein in complex with DNA. The structure shows that TBP bends the DNA axis by approximately 80 degrees, presumably in order to expose bases and improve recognition. The structure is available at RCSB: http://www.rcsb.org/pdb/explore.do?structureId=1ytb . (Make sure you check out the Jmol view.)

Thermodynamically speaking, bending DNA would require energy. Therefore, DNA that was pre-bent (e.g., due to auxiliary binding proteins or composition bias) would improve binding.

So, I suspect that in the context DNA binding proteins, "curved" refers to the static curvature of unbound DNA or to the bending of DNA upon binding in order to facilitate recognition.

Tidal lock of earth and moon

The Earth and the Moon do interact, but because they have different sizes and masses the effect on each is different.

The Moon rotates once in its orbit around the Earth, causing it to constantly show the same face. This was the Earth's effect on the Moon due to tidal dragging by gravity.

It's pretty stable, the Moon will continue to show the same face to the Earth even as the tidal forces cause it to orbit farther and farther away.

We actually see slightly more than 50% of the Moon. The Moon's orbit causes its aspect to nod because its orbit is slightly elliptical and shimmy because it's not orbiting directly over the equator. Over time we actually see almost 60 percent of the surface of the Moon (an effect called libration).

The Moon's effect on the Earth has been to slow its daily rotation to 24 hours. In the past, the Moon was much closer to the Earth, and the day was much shorter. As time passes and the Moon moves into a wider orbit, the length of the Earth's day will increase (see e.g. this Scientific american post).

I've read that the Moon would recede to a certain point, then begin approaching the Earth again, but unfortunately the Sun will swell into a red giant before then and swallow the Earth and the Moon.

distances - Where can I look up the 3D positions of the closest stars?

You can determine the 3D position for a star, $p$, by using the distance from Earth, $R$, as well as the right ascension, $Omega$, and declination, $delta$, within the following formula.

$p = R begin{bmatrix} cos Omega cos delta \ sin Omega cos delta \ sin delta \ end{bmatrix}$

Note this will yield positions within the Earth-centered inertial reference frame.

molecular biology - In C. elegans, why does knock-down of cco-1 in some tissues increase lifespan, and knock-down of cco-1 in other tissues decrease lifespan?

Let us first answer the question: what is the effect of cco-1 knock-down in C. elegans. Durieux J., Wolff S. and Dillin A. in their paper "The cell-non-autonomous nature of electron transport chain-mediated longevity". Cell 144:79-91 (2011) provide the following explanation:

The life span of C. elegans can be increased via reduced function of
the mitochondria; however, the extent to which mitochondrial
alteration in a single, distinct tissue may influence aging in the
whole organism remains unknown.

So, by slowing-down the mitochondria function you manage to slow-down the normal wear-and-tear of the mitochondrial enzymes, which are normally responsible for the so-called respiratory chain -- one of the fundamental biological process for storing energy in cells (despite the common belief, ATP is rarely to store energy, but mostly to transfer it to the target!).

If we group the tissues where the knock-down leads to similar effects we will get muscle cells opposed by neurons and intenstine cells.

This is just my suggestion, but if we approach those groups with the idea of energy storage and re-use in mind, we'll see that muscle cells have much higher turnover of energy (for contraction and even more for dilation), whereas nerve and intestine cells are not that dependent upon energy and have much lower baseline of energy consumption and turnover.

Now we can suggest that cco-1 knock-down decreases the functions of mitochondria in muscle cells below the acceptable level and the decreased life span is due to depletion of mitochondrial energy storage under light stress conditions which would have been easily coped with under normal conditions. And vice versa, nervous/intenstine cells requiring a constant energy source at a much lower level just help the animal to cope with stress more effectively even during old age, leading to increased life span.

observation - Is stacking welder's glasses a safe way to watch at the eclipse?

You can find in many place on the Internet that welder's glass #14 is good for looking at an eclipse. Tomorrow (March, 20th 2015 at 10:45 CET) there's a solar eclipse and yesterday I could only find glasses #11 and #9. I tried briefly this morning, and combining a #11 and a #9 was giving me a good view of the sun. Using 2 #11 gave a too dark image. Now, I read different opinions on the internet.

Against (Perkins Observatory):
http://perkins.owu.edu/solar_viewing_safety.htm

Be careful that you use the right kind of glass! Welder's glass is
numbered from 1 to 14 with 14 being the darkest. It is only number 14
glass that is dark enough for solar viewing! And NO STACKING! A pair
of number 7's or a 10 and a 4 together DO NOT have the same protection
as a single piece of number 14 (see unsafe methods for more details).

Favorable (Royal Astronomical Society of Canada):
https://www.rasc.ca/tov/safety

If SN14 filter is not available, it is possible to combine lower shade
numbers to get roughly the same level of eye protection from solar
radiation, e.g. combining SN 6 and SN 8 filters. However the image
quality may be considerably poorer than that seen through the single
SN14 filter

I could not find a table or something explaining which kind of protection gives each number; according to the Canadian website, the only concern is about how much infrared light goes through, ultraviolet does not seem to be a problem in almost any case (I was surprised to read that).

Note: It's not my intention to open here the discussion on what could be other safe methods to watch the eclipse, this is well explained everywhere around. I read too late about the eclipse to order specific glasses.

Edit:
One of the answers here report the following formula: (more insight at this link)

13 or darker is safe enough. Also, you CAN add up welding glass, using
the formula S(sum) = S1 + S2 -1. S(sum) should be greater than or
equal to 13

fundamental astronomy - Finding Mass of Star with only Luminosity

Sounds like homework (correct me if that assumption is wrong, as you may want a somewhat different answer then.), so here is a hint:

Clean up the equation first, to something that looks more like an equation for mass:

$$frac{L}{L_{sun}} = left(frac{M}{M_{sun}}right)^{3.5}$$

$$left(frac{L}{L_{sun}}right)^{frac{1}{3.5}} = frac{M}{M_{sun}}$$