source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-2544 | semiconductor-physics
Title: Why holes in a semiconductor are associated with a net positive charge? I am clear with the idea that holes move in direction of electric field because of motion of bound electrons that get just some energy to jump into next hole.But i am confused with giving holes a positive charge.
I understood that in intrinsic semiconductor removal of electron is associated with less screening of some protons so their is a positive charge effect that can be made associated with location where electron left i.e hole ,so some people and textbook say hole has a net positive charge.like this shown in my book and answered to question Why Holes have an effective positive charge?
But my question is if we apply this positive charge to hole in p type semiconductor then semiconductor is no more neutral that is a contradiction to property given in my textbook.Please consider explaning how in this case we can assiciate the hole with a positive charge.
In this above picture we can see how neutral charge of semiconductor is affected when we associate postive charge with holes.(Note in picture already 10 protons are screened with 10 electrons so it shows +4)
picture of textbook that says semiconductor should be neutral. Well, think of it this way,
you've got a bunch of atoms all lined up and having equal number of protons and electrons (say, Si atoms) and hence are neutral as a whole
Now, you add a trivalent atom (which, by the way, is also neutral)-like Al-and this leaves a "space" in the arrangement, as seen in your textbook.
If an electron in the neighborhood jumps into the gap, it leaves a gap at the point where it originally was. Since the electron is no longer in the gap, the previously neutral region becomes a "positive gap", or what we call a hole.
But at the same time, the Al atom becomes negatively charged, as it has 14 electrons and 13 protons.
Therefore, the net charge on the Semiconductor adds up to is zero.
The following is multiple choice question (with options) to answer.
Positive charge is mostly found in what part of an atom? | [
"ions",
"electron shell",
"nucleus",
"neutrons"
] | C | Rutherford’s discoveries meant that Thomson’s plum pudding model was incorrect. Positive charge is not spread evenly throughout an atom. Instead, it is all concentrated in the tiny nucleus. The rest of the atom is empty space except for the electrons scattered through it. In Rutherford’s model of the atom, which is shown in the Figure below , the electrons move around the massive nucleus like planets orbiting the sun. That’s why his model is called the planetary model. Rutherford didn’t know exactly where or how electrons orbit the nucleus. That research would be undertaken by later scientists, beginning with Niels Bohr in 1913. New and improved atomic models would also be developed. Nonetheless, Rutherford’s model is still often used to represent the atom. You can see an animated version of the model at this URL: http://www. clickandlearn. org/gr9_sci/atoms/modelsoftheatom. html . |
SciQ | SciQ-2545 | optics, refraction, geometric-optics, lenses, telescopes
I've neglected the convex lens for the sake of simplicity.
It can be seen that the image $A'B'$ is formed at the midpoint of focal length on the same side of object $AB$ (image formed by the convex lens). I also verified it using the thin lens formula $\frac 1 v -\frac 1 u=\frac 1 f$. So for an object at the focal point of a diverging lens, the image forms midway between the object and the lens. But this is contradictory to what is being explained in my textbook, and in the answer linked above regarding Galilean telescopes.
In short, my question is - How does a diverging lens in a Galilean telescope form an image at infinity when its object is at its focal plane? The first (convex) lens produces an image that is to the right of the diverging lens i.e. this acts as a virtual object for the diverging lens. So the rays look like the diagram below. I've drawn a point object to keep the diagram simple. This could for example be an image of a distant star.
When we say there is a virtual object we mean that to the left of the lens the light rays are converging as if they were coming to a focus at the point where the virtual object is. I've drawn those converging rays as solid blur lines to the left of the lens and as dashed line to the right of the lens to show how they would come to a focus at the object if the diverging lens was not there.
Now the diverging lens makes the rays diverge, which in this case means it reduces their convergence. With the diverging lens in place the light rays look like this:
The following is multiple choice question (with options) to answer.
In the lens makers' equation, diverging lenses and virtual images are associated with what kinds of numbers? | [
"fractional numbers",
"negative numbers",
"positive numbers",
"variable numbers"
] | B | When using the lens makers equation, remember that real things get positive numbers and virtual things get negative numbers. Thus, diverging lenses and virtual images get negative numbers. The object distance is always positive. |
SciQ | SciQ-2546 | python, parsing, numpy, scipy
if 'electric' in producer.energy:
recipe = self.produce(cls, producer, **kwargs)
recipe.rates['Energy'] = energy
yield recipe
elif 'heat' in producer.energy:
recipe = self.produce(cls, producer, **kwargs)
recipe.rates['Heat'] = energy
yield recipe
elif 'burner' in producer.energy:
for fuel_name in producer.valid_fuel.split('+'):
fuel_name = fuel_name.strip().lower()
fuel = all_items[fuel_name]
fuel_value = parse_power(fuel.fuel_value)
new_kwargs = dict(kwargs)
if self.title:
title = self.title
else:
title = f'{self.resource} ({producer})'
new_kwargs['title'] = f'{title} fueled by {fuel_name}'
recipe = self.produce(cls, producer, **new_kwargs)
recipe.rates[fuel.title] = energy / fuel_value
yield recipe
else:
raise NotImplementedError()
tree_re = re.compile(r'(\d+) .*?\|([^}|]+)\}')
def wood_mining(self) -> Iterable[MiningRecipe]:
miners = tuple(
ManualMiner(tool)
for tool in all_items.values()
if tool.prototype_type == 'mining-tool'
)
for m in self.tree_re.finditer(self.resource.mining_time):
mining_time, source = int(m[1]), m[2]
for miner in miners:
yield self.produce(
MiningRecipe, miner,
mining_hardness=float(self.resource.mining_hardness),
mining_time=mining_time,
title=f'{self.resource} ({miner} from {source})')
The following is multiple choice question (with options) to answer.
What is another name for producers? | [
"autotrophs",
"rotifers",
"allergens",
"plants"
] | A | Producers are organisms that produce food for themselves and other organisms. They use energy and simple inorganic molecules to make organic compounds. The stability of producers is vital to ecosystems because all organisms need organic molecules. Producers are also called autotrophs. There are two basic types of autotrophs: photoautotrophs and chemoautotrophs. |
SciQ | SciQ-2547 | botany, terminology, fruit
Title: What is the name of this part in plants, fruits, vegetables? What is the name of this part of the plant, fruit, vegetable? The thing that the plant is connected with the tree and gets nutrients with? The part we usually cut out when eat fruit.
Examples below
Papaya
Banana
Mango 'Stalk' or 'pedicel' would be an appropriate term (see, for example, this paper or this one). Specifically, you could say 'terminal part of the stalk/pedicel', though I don't know if there is a word for that.
Note that the term pedicel is commonly used for the stalk of a flower; it makes sense to use it for fruits too as they are derived from flowers.
The following is multiple choice question (with options) to answer.
Consisting of a stigma, style, and ovary, the pistil of a flower is what type of organ? | [
"female neural organ",
"female respiratory organ",
"female immune organ",
"female reproductive organ"
] | D | The female reproductive organ in a flower is the pistil . It consists of a stigma, style, and ovary. The stigma is the top of the pistil. It is sticky to help it "catch" pollen. The style connects the stigma to the ovary. The ovary is where eggs form and seeds develop. As seeds develop, the ovary turns into a fruit . The fruit protects the seeds. It also attracts animals that may eat the fruit and help disperse the seeds. |
SciQ | SciQ-2548 | zoology, entomology, species-identification
Title: What flying insect is this?
Found in Russia. Approx. 7 cm. This is Crane fly, of the Tipulidae family. They don't bite humans, adults feed on nectar. Larvae prefer moist environments such as wet soil or decomposing vegetable matter and can consume roots and vegetation, damaging plants. Among others, bats and some Coleoptera are its predators.
Further informations can be found in the Wikipedia article linked above.
The following is multiple choice question (with options) to answer.
Chewing insects such as dragonflies and grasshoppers have how many sets of jaws? | [
"three",
"four",
"one",
"two"
] | D | If all three bulbs are set a full intensity, the person sees __________. |
SciQ | SciQ-2549 | solutions, phase, evaporation
Title: What is the relationship between solutions and changes to states of matter? For example, when liquid water evaporates, my instinct is to say that of course it's become gas, but I'm a bit unsure because, if I understand correctly, evaporation occurs because air dissolves the water, and it's not clear to me whether that counts as a phase change. Intuitively it seems like it should should water dissolves in the air or salt dissolved in water, etc. have different properties before and after being dissolved. And yet, the way I've always heard it explained, phase changes are specifically due to changes in temperature and/or pressure, not due to chemical interactions with another another substance.
On the other hand, from what I remember from chem 101 and 102, when we considered chemical reactions occuring between solids dissolved in a liquid (usually acids and bases dissolved in water), we usually just labeled them as aqueous, meaning "in solution", whereas for non-aqueous substances, we'd label them with the relevant state of matter, solid, liquid, or gas. Does that mean dissolved substances constitute their own state of matter? Or that it's simply not meaningful to talk about the state of the solute independent of the solvent?
I also saw this thread, Is it appropriate to say "solid-in-gas solution" and "liquid-in-gas solution"?, where someone says, "Whenever there is only one phase, but there are two or more chemical species, then you have a solution", which heavily implies there's a fundamental relationship between phase changes and solutions, but it also doesn't seem quite right Water vapour in air is a solution, but not in the same sense as solutions in water.
Water vapour in air is solution in sense of homogenous mixture, where molecules move freely and independently.
Salts in water dissociate (are dissociated by water) to ions. Having a net charge, they form a nonhomogeneous electrostatic gradient.Ions are hydrated by water molecules that have an electric dipole and therefore attracted to the center of such a gradient. So here we see strong interaction and dependent motion.
The following is multiple choice question (with options) to answer.
What kind of change occurs whenever matter changes into an entirely different substance with different chemical properties? | [
"reversible change",
"chemical change",
"carbon change",
"physical change"
] | B | A chemical change occurs whenever matter changes into an entirely different substance with different chemical properties. Burning is an example of a chemical change. |
SciQ | SciQ-2550 | life, replication
Title: What is the name of the smallest self-replicating thing? Some time last year, I found an article on Wikipedia about the smallest something to be able to reproduce.
I don't remember exactly what it was, but I am fairly certain that after the initial discovery another of the previous organism (this one slightly smaller) was discovered.
I think that the smallest something might have been the smallest self-replicating protein, or smallest self-replicating molecule, or something like that.
It was not mentioned in this thread: Which organism has the smallest genome length?
It had a strange, stand-out name and I believe it was discovered in the 90s. You're probably thinking of the Spiegelman Monster. It was actually discovered in 1965, but it was discovered that it became shorter over time in 1997.
It also wasn't included in that thread, and it has a strange name.
http://en.wikipedia.org/wiki/Spiegelman_Monster
The following is multiple choice question (with options) to answer.
What is a small, relatively simple single-celled organism called? | [
"eukaryote",
"ribosome",
"amoeba",
"prokaryote"
] | D | Even though large life forms have been very successful on Earth, most of the life forms on Earth today are still prokaryotes—small, relatively simple single-celled organisms. As it is difficult to identify, observe and study such small forms of life, most of these organisms remain unknown to scientists. Advancing technologies, however, do allow for the identification and study of such organisms. |
SciQ | SciQ-2551 | cell-biology, neuroscience, histology
Although the paper mainly talks of the sorting of axonal and somatodendritic vesicles as seen in the picture, they also seem to apply for the RER which actually are the basis for Nissl's granules.
This structure excludes not only somatodendritic vesicles but also larger organelles, such as the Golgi complex and the rough ER, in effect constituting the cytoplasmic boundary for the somatodendritic and axonal domains..... The exclusion of the rough ER and Golgi complex, in addition to somatodendritic vesicles, at the PAEZ suggests that a common restriction mechanism may operate for all of these organelles.
Well, as you might have understood by now, it's not a matter of the size of the axon/ dendrite since same sized vesicles are being diverted in either direction and as previously mentioned, even mitochondria enter the axon.
The following is multiple choice question (with options) to answer.
The golgi apparatus works like a mail room by receiving and sending what? | [
"particles",
"acids",
"proteins",
"enzymes"
] | C | The Golgi apparatus works like a mail room. The Golgi apparatus receives proteins from the rough ER and puts "shipping addresses" on them. The Golgi then packages the proteins into vesicles and sends them to the right place in the cell or to the cell membrane. Some of these proteins are secreted from the cell (they exit the cell); others are placed into the cell membrane. |
SciQ | SciQ-2552 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
Which part of the body has mucus and hair to trap dust and also warms and moistens air so to not harm lung tissue? | [
"the throat",
"the ear",
"the nose",
"the tongue"
] | C | In the nose, mucus and hairs trap any dust or other particles in the air. The air is also warmed and moistened so it won’t harm delicate tissues of the lungs. |
SciQ | SciQ-2553 | cell-biology, terminology
Title: What is the difference between cytosol and cytoplasm? I've generally seen cytosol defined as the solution inside cells minus the organelles, cytoskeleton, etc and cytoplasm as the cytosol plus the organelles, cytoskeleton, etc. This naturally leads to the impression that cytosol is the cytoplasm minus all the solids. The problem here is that there are all sorts of other large molecules in the cells which could be thought of as solid. Are they also part of the cytosol or are they suspended in it? (I.e. are they part of the cytosol or are they non-cytosol components of the cytoplasm?)
Basically, I'm asking if the precise definition of cytosol is just anything in the cell that's not behind an endomembrane (save the exoskeleton) or if the dividing line is something else.
Subquestion: things can get even more terminologically confused because the cytosol is sometimes called the matrix. What the heck is the preferred terminology with this stuff? IMO, the definitive answer to this question is given in a paper by J. S Clegg. He traced the origin of the term cytosol to a book chapter by H. A. Lardy, and confirmed by email that Lardy had indeed coined the term. Their definition of cytosol is as follows:
... that portion of the cell which is found in the supernatant fraction after centrifuging the homogenate at 105 000 x g for 1 hour.
The following is multiple choice question (with options) to answer.
What are the structures in the cytoplasm where proteins are made? | [
"chromosomes",
"nucleus",
"prokaryotes",
"ribosomes"
] | D | Ribosomes are structures in the cytoplasm where proteins are made. |
SciQ | SciQ-2554 | quantum-mechanics, soft-question, popular-science
The situation here is uncertain because of issues far displaced from chaos or quantum. The challenges arise because it is massively difficult to isolate the input factors and determine them.
School performance, for example, could esily be expected to be influenced by many different inputs. Family patterns, income, culture, etc. etc. It would be a chore to even list them all, never mind determine them and extract the effect. Thus, supposing there is an effect due to nutrition, it may be required to extract the effect from the effect of large numbers of other input factors. Each of which may be known to a different degree of accuracy.
This school uses this set of textbooks and that another set. It already begins to be difficult to extract results. This school runs for 7 hours per day and that one 9. This one starts students at age 6 and that at age 5. And so on and so on. This one is in the innner city and that one is far out in rural areas. All of these could easily be expected to have some effect, though in advance it would be difficult to know exactly what.
And it is also massively difficult to be confident in the output factors. It may be that different school systems do things very differently and so performance is a major challenge to extract and compare. This school uses numerical grades and that letter grades is just a trivial example. This school uses standardized state-wide tests, this one uses surprise quizzes, and that one uses interviews of the students. This one does a lot of written work with written tests, and that one does a lot of hands-on work with group presentations. It is a challenge to extract the results and present them in a manner that fairly compares them. Sometimes even for the same school from one year to the next.
And, even when two schools use the same method of evaluating performance, it is not instantly obvious that this method is a good predictor of the academic future of a given student. Written tests, for example, can be well correlated on average. But the individual student is subject to a huge collection of factors that may mean he does not align with the results his tests would suggest.
The following is multiple choice question (with options) to answer.
What is the key issue in the small-population approach? | [
"alternative variation",
"genetic variation",
"genetic mutation",
"disease variation"
] | B | |
SciQ | SciQ-2555 | fluid-dynamics, newtonian-gravity
$$d\approx\frac{h}{\frac{\rho_W}{\rho_B}-1}$$
but I'm almost certain that this will greatly overestimate your penetration depth: it says that your penetration depth will be much deeper than the dive tower is tall.
So you need at least one $d$ observation to work out the value of the unknown $C_D\,A$ - the "fudge factored" effective cross sectional area you present to the water. $C_D$ values for long thin objects are typically about 1. If your cross sectional area (cut through the anatomist's transverse plane) is $0.5\times 0.3=0.15{\rm m^2}$, your mass $90{\rm kg}$, your density with your breath drawn in is $950{\rm kg\,m^{-3}}$ and your drag co-efficient is $1$, then we get, for $d$ and $h$ measured in metres:
$$d=0.6\,\log\left(1+32\,h\right)$$
yielding $d=2.09{\rm m}$ for $h=1{\rm m}$, $d=2.74{\rm m}$ for $h=3{\rm m}$, $d=3.04{\rm m}$ for $h=5{\rm m}$, $d=3.28{\rm m}$ for $h=7.5{\rm m}$ and $d=3.46{\rm m}$ for $h=10{\rm m}$. These don't seem far off what one observes. These will be underestimates because I didn't correctly describe the "transition epoch" where your body is only partly steeped in the water, and therefore the buoyancy in particular is overestimated.
Moreover, surprisingly, these estimates are not far off tpg2114's answer. Certainly, $d$ is a very weak function of $h$ once $h$ rises above $1{\rm m}$, in keeping with the other answer.
The following is multiple choice question (with options) to answer.
What is the minimum depth in the aphotic zone? | [
"10 meters",
"450 meters",
"200 meters",
"150 meters"
] | C | The aphotic zone is water deeper than 200 meters. This is where too little sunlight penetrates for photosynthesis to occur. As a result, food must be made by chemosynthesis or else drift down from the water above. |
SciQ | SciQ-2556 | photosynthesis, cellular-respiration, energy, sugar
Basically, points 4-7 convey that Calvin-Benson cycle not only produces sugar but what it actually does is fix inorganic carbon (as CO2) to organic form (in the form of sugar). So, most (practically all) of the carbon that a photosynthetic plant has, comes from this carbon fixation process and that's how plants are photoautotrophic.
The following is multiple choice question (with options) to answer.
What is the process by which plants gain energy and produce sugar? | [
"chemosynthesis",
"glycolysis",
"respiration",
"photosynthesis"
] | D | 13 Photosynthesis 6 CO2 + 6 H2 O → C6 H12 O6 + 6 O2 • One of most important reactions in history of life: • source of atmospheric O2 • ultimately led to aerobic respiration and eukaryotes • Responsible for bulk of glucose production • Early experiments showed that mass of plant must be derived from substances in the air, not the soil • Experiments with isotopes showed that liberated oxygen comes from water • Experiments also showed that light is essential but that some reactions (e. , reduction of CO2 ) continue in the dark • Plants do two big, important things during photosynthesis: gain energy (absorb light) and build sugar (glucose). • Photosynthesis can be divided into two series of chemical reactions: the light (lightdependent) reactions and the dark (light-independent) reactions. In light reactions, light is absorbed; in dark reactions, sugar is built. • Occurs when plants, algae, and autotrophic bacteria absorb light energy and build glucose. |
SciQ | SciQ-2557 | molecular-biology, immunology
Title: A few questions regarding immunology I know that there is a variable region on antibodies which can recognize a wide variety of antigens, and that germinal centers create more "fit" antibodies to respond to an infection.
So I was just wondering:
The following is multiple choice question (with options) to answer.
What are embedded in the membranes of b cells and bind a variety of antigens through their variable regions? | [
"a.m. cell receptors",
"b cell receptors",
"b.a.p cell receptors",
"er cell receptors"
] | B | Figure 42.13 B cell receptors are embedded in the membranes of B cells and bind a variety of antigens through their variable regions. The signal transduction region transfers the signal into the cell. |
SciQ | SciQ-2558 | universe, laws-of-physics
But if you begin with the assumption of existence of some property (pattern) of your infinite chain of balls that is independent of where you start looking at it, and show that this predicts all other local patterns with as little additional assumptions, then that “law” is more fundamental. These are called symmetries of the system.
This is something amazing about the way nature is! Some laws that we conjured up to explain local behaviour somehow can be extrapolated to understand phenomena that the laws weren’t derived from, or to make new predictions that are then observed to be true!
The following is multiple choice question (with options) to answer.
A statement that describes what always happens under certain conditions in nature is also known as what? | [
"scientific motion",
"theory",
"hypothesis",
"scientific law"
] | D | Scientists think of nature as a single system controlled by natural laws. Scientists strive to increase their understanding of the natural world by discovering natural laws. Laws of nature are expressed as scientific laws. A scientific law is a statement that describes what always happens under certain conditions in nature. |
SciQ | SciQ-2559 | evolution, herpetology, dinosaurs
Title: Evolution of dinosaurs What did dinosaurs evolve from? Was it the reptiles that evolved from amphibians? I have been researching this but am very confused with who their direct predecessor was. Amphibians evolved from fish...reptiles from amphibians...dinosaurs from reptiles (?)...and birds from dinosaurs. That is my understanding, but it could be wrong. How are dinosaurs related to reptiles? And if they did evolve from reptiles, which kind of reptiles (such as lizards, crocodiles, or turtles for example)? Source of information
See the post The best free and most up to date phylogenetic tree on the internet? for info about how to find such information.
Generally speaking, you might be interested in an intro to phylogenetics such as the one provided in this answer for example.
Where are dinosaurs in the tree of life?
Dinosaurs fall within the Reptiliomorpha clade. Please note that Reptiliomorpha does not quite correspond to what we today call reptiles. Please see the post If dinosaurs could have feathers, would they still be reptiles?
Reptiliomorpha is the sister clade to Amphibia (from here) which contain all living amphibians.
If you look within the Amniota, you will find all of the following
Here, you see that turtles and mammals are an off-shoot of Diapsida. So dinosaurs are not mammals and there are not closely related to turtles. Now if you click on Diapsida you will find ...
the Archosauromorpha which contains all crocodiles, birds and dinosaurs. You can keep going to find Therapoda which contains many dinosaurs and birds. You can keep going like this for yourself and discover the entire tree of life!
Reacting to your sentences
What did dinosaurs evolve from?
When asking this question, please do not forget that no species evolved from an extant species. If this is unclear to you, you should have a look at this post.
Was it the reptiles that evolved from amphibians?
Well... the term reptile is a mess because it does not represent a monophyletic group (see this post). If you do not understand the term monophyletic, then you should have a look at this answer.
Amphibians evolved from fish...
The following is multiple choice question (with options) to answer.
What developmental stage do alligators lack that most other amphibians have? | [
"larval stage",
"Egg Stage",
"Tadpole stage",
"metamorphosis"
] | A | Young reptiles, like the baby alligator in Figure below , look like smaller versions of the adults. They don’t have a larval stage as most amphibians do. Baby reptiles are able to move and search for food but are at high risk of predation. Adult reptiles rarely provide any care for their offspring once the eggs are laid. The only exceptions are female alligators and crocodiles. They defend their eggs and hatchlings from predators and help them reach the water. |
SciQ | SciQ-2560 | human-biology, human-anatomy, human-physiology
Title: How can we move our lips even though they don't have any bones? How can we move our lips even though they don't have any bones?
We can move everything if it is attached to the bones. Example: Legs & Arms.
otherwise we can't move it. Because of the Orbicularis oris muscle, it's a complex of muscles in the lips that encircles the mouth, It forms the greater part of the substance of the lips, lying between the skin and the mucus membrane, and extending from the edge of each lip to its root.
The following is multiple choice question (with options) to answer.
What attaches a muscle to a bone? | [
"tendons",
"marrow",
"arteries",
"veins"
] | A | When skeletal muscles contract, bones move. But how do muscles make your bones move? A voluntary muscles usually works across a joint. It is attached to both the bones on either side of the joint by strong cords called tendons. A tendon is a tough band of connective tissue that connects a muscle to a bone. Tendons are similar to ligaments, except that ligaments join bones to each other. Muscles move the body by contracting against the skeleton. When muscles contract, they get shorter. By contracting, muscles pull on bones and allow the body to move. |
SciQ | SciQ-2561 | meteorology, wind, tropical-cyclone, storms, tornado
Title: Why is there no middle ground between tornadoes and hurricanes? A tornado has an effective area of destruction about the size of a city block.
A hurricane spans several hundred kilometers.
However, there doesn't seem to be a continuum between the two. Why are there no vortex windstorms on the scale of a city? Is it because tornadoes and hurricanes have different formation mechanisms? Or is there a reason why city-sized vortices would be so weak as to be un-newsworthy? Tornadoes are the result of small-scale effects such as the convergence of updraft/downdraft regions in a single thunderstorm, the stretching or entrainment of vertical vorticity, wind shear profiles, and even friction with the ground.
Hurricanes rely on massive amounts of latent heat release from an atmosphere moistened by warm ocean waters causing rising air and lower pressure over a wide area. This allows the Coriolis effect to act, sculpting airflow into a spiral pattern. Under normal conditions, the Coriolis effect is only applicable over a large area (don't get me started on the toilet myth).
There are some intermediate types of circulations. A mesocyclone is roughly city-sized (and these are often associated with tornadoes). A mesoscale convective vortex can form out of a thunderstorm complex and are roughly state-sized (usually more of an Indiana than a Texas). There have been very small hurricanes and typhoons (look up Tropical Storm Marco or Typhoon Tracy).
Extending the scale upward, the normal "synoptic" low pressure systems associated with cold and warm fronts and usually bigger than hurricanes, and upper-level circulations can be continent-sized.
The following is multiple choice question (with options) to answer.
What are two common weather characteristics of hurricanes? | [
"low winds and sandstorms",
"high winds and snowfall",
"small winds and rainfall",
"high winds and rainfall"
] | D | Volcanoes and earthquakes are common at active margins. Active margins are near plate boundaries. |
SciQ | SciQ-2562 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
What kind of organism causes the often fatal lung disease tuberculosis? | [
"pathogens",
"bacteria",
"algae",
"virus"
] | B | |
SciQ | SciQ-2563 | geophysics, plate-tectonics
Title: Equatorial bulge and tectonic plates It is well known that the Earth is not a sphere, but rather it bulges at the equator. Also it is well known that the Earth's crust is composed of 7 or 8 (depending on definition) major tectonic plates, which are able to move on top of the asthenosphere, the upper layer of the Earth's mantle.
Due to the equatorial bulge, it would seem as though plates near the equator should not be able to drift away from the equator, and plates away from the equator should not be able to drift near the equator, since they will not be of the right shape to fit over these portions of the Earth. So how are the plates able to drift to and from the equator when the surface of the Earth is shaped differently there? The plates are not as rigid as you think. You seem to be imagining the situation as something like this: I boil an egg and take the shell off in pieces, but I can't take a piece of shell from the end and make it lay flat on the side of the egg. However, rock is not that rigid on scales of thousands of kilometres and millions of years (I don't think there exists any material which would be that rigid). Also, Earth's equatorial bulge is tiny relative to its diameter -- less than 50km. Tectonic plates move very slowly, and there is plenty of time for them to deform as they move.
The following is multiple choice question (with options) to answer.
Where do plates move apart in oceans and on land? | [
"coastal zones",
"unsettled plate boundaries",
"divergent plate boundaries",
"volcanic ridges"
] | C | Plates move apart at divergent plate boundaries. This can occur in the oceans or on land. |
SciQ | SciQ-2564 | It would seem that you're making the mistake of assuming the pattern is linear. When you're finding all configurations of non-0 digits in the case in which m is 1, there should be just as many configurations of 0 digits in the case in which m is 9. So: $$xxxxxxxxx0,0xxxxxxxxx$$
If your linear calculation were accurate, then there should be 10000000000 ways to place that singular 0 digit! Hope that helps!
The following is multiple choice question (with options) to answer.
Zeros that appear in front of all of the nonzero digits are called what? | [
"significant digits",
"non-numbers",
"left-end zeros",
"zero sum game"
] | C | 3. Zeros that appear in front of all of the nonzero digits are called left-end zeros. Left-end zeros are never significant. A. 0.008 has one significant figure. |
SciQ | SciQ-2565 | photosynthesis
Title: Photosystem I and the ETC In the light reactions of photosynthesis, Photosystem I receives electrons from the ETC after Photosystem II sends them to the ETC. Then, when Photosystem I receives light, the electron becomes excited and passes the electron back to the ETC. This leads me to my question: In the following question, are both $B$ and $E$ correct?
Which of the following are directly associated with photosystem I?
$A)$ harvesting of light energy by ATP
$B)$ receiving electrons from the thylakoid membrane electron transport chain
$C)$ generation of molecular oxygen
$D)$ extraction of hydrogen electrons from the splitting of water
$E)$ passing electrons to the thylakoid membrane electron transport chain It appears the author of the question is trying to use "thylakoid electron transport chain" in an overly specific way. The chain from which PS I receives electrons has far more components and is different from the shorter chain to which PS I passes its electrons. But according to my copy of Biology, Campbell & Reece 7th edition, both are called "electron transport chains" and both reside in, or on, the thylakoid membrane. Perhaps the "directly" in the question refers to the fact that PS I's electron is first captured by a "primary receptor" before being passed to ferredixon, the first member of the chain to which PS I passes electrons. But, again according to Campbell, this primary acceptor is considered part of the photosystem.
I used to teach this stuff. I'd toss out the question.
The following is multiple choice question (with options) to answer.
What consists of thylakoid membranes surrounded by stroma? | [
"a chloroplast",
"a nucleus",
"a photon",
"a stem"
] | A | A chloroplast consists of thylakoid membranes surrounded by stroma. The thylakoid membranes contain molecules of the green pigment chlorophyll. |
SciQ | SciQ-2566 | power, battery, circuit
Regarding your bonus points, the other devices you've listed aren't power storage devices. They can run indefinitely, provided they're powered. A solar cell doesn't hold a charge, so it can't run anything for any amount of time if there's no sun. If there is sun, it can supply its rated power as long as the sun is out. Note again though rated power - you can't run a 5W robot on a 1W solar cell. Same applies for all other power supplies. The are power supplies, not power reserves like a battery.
The following is multiple choice question (with options) to answer.
Portable amplifiers have batteries that store what type of energy? | [
"carbon energy",
"kinetic energy",
"mechanical energy",
"chemical energy"
] | D | Amplifier: Tim Walker; Battery: Emilian Robert Vicol. Portable amplifiers have batteries that store chemical energy . Amplifier: CC BY 2.0; Battery: Public Domain. |
SciQ | SciQ-2567 | glaciology, antarctic, ice, sea-ice, ice-shelf
Title: Is this 70km crack in an ice shelf of Antarctica remarkable, or a regular occurrence? I've just seen the LiveScience article 70-Mile-Long Crack Opens Up in Anatarctica. I'm not sure if the title is a bit sensational or not, the crack is in an ice shelf, not the continent of Antarctica.
An ominous crack in an Antarctic ice shelf as wide as a football field is long takes on an otherworldly beauty in a new aerial image.
Snapped by scientists on NASA's IceBridge mission, the shot shows a rift in Larsen C, an ice shelf that is floating off the Antarctic Peninsula. When the crack eventually spreads across the entire ice shelf, it will create an iceberg the size of the state of Delaware, according to IceBridge. That's around 2,491 square miles (6,451 square kilometers).
As of Nov. 10, when the IceBridge scientists observed this crack, it was 70 miles (112 km) long and more than 300 feet (91 meters) wide. The dark depths of the crack plunge down about a third of a mile (0.5 km), all the way through the ice to the ocean below.
[...] Larsen C is Antarctica's fourth-largest ice shelf, and it holds back the land-based glaciers just behind it: Once the ice shelf goes, those slow-flowing glaciers have one less barrier in their journey toward the sea.
My primary question: is this a remarkable event, or something that over time happens regularly? Isn't this just a natural part of "those slow-flowing glaciers... journey toward the sea." ?
I'm also wondering 1) Is an iceberg the size of Delaware actually remarkable, or something that just happens from time-to-time? And 2) how they (actually) know the crack goes all the way to the ocean - can they actually see the water in images, or is this a hypothesis based on understanding of cracks of this length and width? I can ask as a separate questions if it's too much to ask here.
above: Image from here. "A huge crack can be seen in the Antarctic Peninsula's Larsen C ice shelf in this aerial image snapped on Nov. 10, 2016, as part of NASA's IceBridge mission. Credit: NASA/John Sonntag"
The following is multiple choice question (with options) to answer.
The movement of ice causes glaciers to have cracks referred to as? | [
"anomalies",
"slides",
"crevasses",
"fissures"
] | C | Because the ice is moving, glaciers have cracks called crevasses ( Figure below ). There is a large crevasse at the top of an alpine glacier called a bergshrund . Below the bergshrund, the ice is moving downhill. Above the bergshrund, the ice is stuck to the mountain. |
SciQ | SciQ-2568 | human-biology, human-physiology
Title: Is there muscle hyperplasia or hypertrophy after surgery? After exercise there is hypertrophy only. I am curious, if a surgery removes muscle, will there be hyperplasia or hypertrophy to restore it? It does not required much research to find the answer. After injury and surgery the muscle undergoes inflammation to clear up the debris. After that myogenic cells start to proliferate and differentiate, so as expected, there is hyperplasia by restoring injured muscle. Which means that the body can fully restore muscle function if the injury is not too severe.
Effective fiber hypertrophy in satellite cell-depleted skeletal muscle.
Cellular and Molecular Regulation of Muscle Regeneration
Regeneration of mammalian skeletal muscle. Basic mechanisms and clinical implications.
I investigated this a little bit further. Muscle regrowth is mediated by the BM (basement membrane) which is the extracellular matrix that sorrounds the muscle fiber. If that is badly damaged or the nerve is cut, then the muscle fiber won't grow back and we will get scar tissue instead. The muscle will compensate this at a certain level by hypertrophy. There is an interesting new treatment for severe muscle injury, which removes the scar tissue and adds pig extracellular matrix to regrow the muscle.
Implant Lets Patients Regrow Lost Leg Muscle
The following is multiple choice question (with options) to answer.
A muscle can return to its original length when relaxed due to a quality of muscle tissue called what? | [
"reach",
"elasticity",
"moisture",
"viscosity"
] | B | The muscles all begin the actual process of contracting (shortening) when a protein called actin is pulled by a protein called myosin. This occurs in striated muscle (skeletal and cardiac) after specific binding sites on the actin have been exposed in response to the interaction between calcium ions (Ca++) and proteins (troponin and tropomyosin) that “shield” the actinbinding sites. Ca++ also is required for the contraction of smooth muscle, although its role is different: here Ca++ activates enzymes, which in turn activate myosin heads. All muscles require adenosine triphosphate (ATP) to continue the process of contracting, and they all relax when the Ca++ is removed and the actin-binding sites are re-shielded. A muscle can return to its original length when relaxed due to a quality of muscle tissue called elasticity. It can recoil back to its original length due to elastic fibers. Muscle tissue also has the quality of extensibility; it can stretch or extend. Contractility allows muscle tissue to pull on its attachment points and shorten with force. Differences among the three muscle types include the microscopic organization of their contractile proteins—actin and myosin. The actin and myosin proteins are arranged very regularly in the cytoplasm of individual muscle cells (referred to as fibers) in both skeletal muscle and cardiac muscle, which creates a pattern, or stripes, called striations. The striations are visible with a light microscope under high magnification (see Figure 10.2). Skeletal muscle fibers are multinucleated structures that compose the skeletal muscle. Cardiac muscle fibers each have one to two nuclei and are physically and electrically connected to each other so that the entire heart contracts as one unit (called a syncytium). Because the actin and myosin are not arranged in such regular fashion in smooth muscle, the cytoplasm of a smooth muscle fiber (which has only a single nucleus) has a uniform, nonstriated appearance (resulting in the name smooth muscle). However, the less organized appearance of smooth muscle should not be interpreted as less efficient. Smooth muscle in the walls of arteries is a critical component that regulates blood pressure necessary to push blood through the circulatory system; and smooth muscle in the skin, visceral organs, and internal passageways is essential for moving all materials through the body. |
SciQ | SciQ-2569 | newtonian-mechanics, forces, everyday-life, biophysics, weight
All of this makes it very complicated because you need to isolate what type of stress is under consideration. However, we can make some general observations.
Any vertical position will maximize compressive stress on the backbone. So standing and sitting straight up should maximize compressive stress. Why sitting down is more than standing up is not clear. Perhaps it has to do with concentrated stress that the reaction force of the seat imposes on the bottom of the spine (tail bone). Or perhaps sitting down causes more curvature of the spine, though I’m not sure.
Any horizontal position will minimize compressive, tensile and bending stress. So lying down should be less “stressful” on the backbone than all the other positions.
Sitting and leaning over would probably be the most stressful since bending of the backbone is maximized. This results in both tensile and compressive stress on the backbone.
Hope this helps.
The following is multiple choice question (with options) to answer.
What feature of the spine helps with flexibility and strength? | [
"curves",
"arrangement",
"angle",
"shape"
] | A | Curvatures of the Vertebral Column The adult vertebral column does not form a straight line, but instead has four curvatures along its length (see Figure 7.20). These curves increase the vertebral column’s strength, flexibility, and ability to absorb shock. When the load on the spine is increased, by carrying a heavy backpack for example, the curvatures increase in depth (become more curved) to accommodate the extra weight. They then spring back when the weight is removed. The four adult curvatures are classified as either primary or secondary curvatures. Primary curves are retained from the original fetal curvature, while secondary curvatures develop after birth. |
SciQ | SciQ-2570 | biophysics, cell-membrane
Title: Why doesn't the cell membrane just...break apart? Forgive me if this is a silly question. I can't understand the basics. Why doesn't the cell membrane just break apart? What's keeping the layers in the phospholipid bilayer together? I know that the membrane is embedded with proteins and lipids, but I still can't wrap my head around the "why". Are the hydrophobic interactions in the middle "stronger" than the hydrophilic interactions on the outside? What's keeping the individual phosphate heads together instead of, say, one of them just drifting away due to a nearby water molecule? The membrane bilayer is held together by hydrophobic forces. This is an entropy driven process. When a greasy or hydrophobic molecule is suspended in water, the water molecules form an organized "cage" around the hydrophobic molecule. When two hydrophobic molecules come into contact, they force the water between them out. This increases the entropy because the freed waters don't need to be organized into the cage. Lipid bilayers have many many many hydrophobic lipids that squeeze out a lot of water and greatly increase entropy. The polar phosphates allow the water to interact with the surface of the membrane, without a polar head group the lipids would form a spherical blob instead of a membrane.
Read this section on wikipedia for more.
The following is multiple choice question (with options) to answer.
How does a cell's membrane keep extracellular materials from mixing with it's internal components? | [
"destroys extracellular materials",
"repels extracellular materials",
"provides a barrier",
"absorbs extracellular materials"
] | C | CHAPTER REVIEW 3.1 The Cell Membrane The cell membrane provides a barrier around the cell, separating its internal components from the extracellular environment. It is composed of a phospholipid bilayer, with hydrophobic internal lipid “tails” and hydrophilic external phosphate “heads. ” Various membrane proteins are scattered throughout the bilayer, both inserted within it and attached to it peripherally. The cell membrane is selectively permeable, allowing only a limited number of materials to diffuse through its lipid bilayer. All materials that cross the membrane do so using passive (non energy-requiring) or active (energy-requiring) transport processes. During passive transport, materials move by simple diffusion or by facilitated diffusion through the membrane, down their concentration gradient. Water passes through the membrane in a diffusion process called osmosis. During active transport, energy is expended to assist material movement across the membrane in a direction against their concentration gradient. Active transport may take place with the help of protein pumps or through the use of vesicles. |
SciQ | SciQ-2571 | neuroscience, neuroanatomy
Title: Why is the anterior pituitary not considered part of the diencephalon? According to the wikipedia page on the diencephalon, the posterior pituitary gland is considered part of the diencephalon, but the anterior is not. Is there a reason that these two lobes of the same gland are considered different enough not to be part of the same brain region? Worth going to the wikipedia page on the pituitary:
In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary, which is an extension of the hypothalamus.
The anterior pituitary arises from an invagination of the oral ectoderm (Rathke's pouch). This contrasts with the posterior pituitary, which originates from neuroectoderm.
The posterior lobe develops as an extension of the hypothalamus, from the floor of the third ventricle.
In other words, the different parts of the pituitary are, developmentally, entirely separate. The posterior lobe is actually part of the hypothalamus. The anterior lobe is not even part of the brain.
Lumping them together with one label happened because the anatomists who originally named the thing didn't know much about it, which is not surprising because anatomical names are quite old and understanding of the functions of any parts of the brain is quite new. Old names stick.
The following is multiple choice question (with options) to answer.
Respiratory development in the embryo begins around week 4. ectodermal tissue from the anterior head region invaginates posteriorly to form olfactory pits, which fuse with endodermal tissue of the developing pharynx. an olfactory pit is one of a pair of structures that will enlarge to become this? | [
"anal cavity",
"nasal cavity",
"eye cavity",
"fluid cavity"
] | B | Weeks 4–7 Respiratory development in the embryo begins around week 4. Ectodermal tissue from the anterior head region invaginates posteriorly to form olfactory pits, which fuse with endodermal tissue of the developing pharynx. An olfactory pit is one of a pair of structures that will enlarge to become the nasal cavity. At about this same time, the lung bud forms. The lung bud is a dome-shaped structure composed of tissue that bulges from the foregut. The foregut is endoderm just inferior to the pharyngeal pouches. The laryngotracheal bud is a structure that forms from the longitudinal extension of the lung bud as development progresses. The portion of this structure nearest the pharynx becomes the trachea, whereas the distal end becomes more bulbous, forming bronchial buds. A bronchial bud is one of a pair of structures that will eventually become the bronchi and all other lower respiratory structures (Figure 22.29). |
SciQ | SciQ-2572 | general-relativity, mass, mass-energy
Title: Mass - Unification of inertial and gravitational definitions As a kinetic definition, mass of a body is a measure of the translational inertia of the body. There is also the gravitational definition of mass. Can these definitions (inertial and gravitational) empirically be proved to be equivalent? Also, are these definitions applicable on a quantum scale? Finally, if the 2 definitions of mass are empirically equivalent, can a single definition be made to encompass the 2? A priori, they could have been different things. The Equivalence Principle - the hypothesis that they are actually the same - is a core input to the theory of General Relativity. To the extent that General Relativity is empirically validated, we have evidence that these really are the same.
There's no complete theory of quantum gravity, so I think we'd have to say that we don't know if the equivalence really holds all the way to the quantum scale.
The following is multiple choice question (with options) to answer.
Anything that occupies space and has mass is known as what? | [
"solid",
"matter",
"dense",
"opaque"
] | B | All living things are made of matter . In fact, matter is the “stuff” of which all organisms are made. Anything that occupies space and has mass is known as matter. Matter, in turn, consists of chemical substances. It is the carbons, hydrogens, oxygens and other elements that combine to form molecules, compounds, organelles, cells and eventually tissues, organs and organisms. In addition to being made of matter, all living organisms also need energy to survive. |
SciQ | SciQ-2573 | physical-chemistry, solubility, solutions
My confusion: Is $K_f$ solute dependent? If no, then why not?
I have this confusion because I'm used to solving problems in which if the solute is changed, then most of the constants related to various properties of the solution also changes. Some solutes form nearly ideal solutions up to moderate molalities, examples being glucose and sucrose in water. Such solutions allow fitting of freezing point temperature data to the following equation:
$$\mathrm{log}(1-x_s)=\frac{\Delta_{fus} H_m}{R}\left(\frac{1}{T_{m}}-\frac{1}{T}\right)$$
Taking various approximations which includes assuming that the heat of fusion is constant from $T$ to $T_m$ (the melting point of the pure solvent), that $x_s<<1$, and that $T_m\approx T$ you obtain the expression for the freezing point depression, $\Delta T = T_m - T$, in terms of the cryoscopic constant $K_f$ and solute molality $m_s$:
$$\Delta T = K_f m_s$$
where
$$K_f = \frac{M_wRT_m^2}{\Delta_{fus}H_m}$$
Since $K_f$ contains parameters that depend only on the solvent (not on the particular solute) the equation can (to within the limitations imposed by the above approximations) be applied to any solutes with which the solvent forms ideal solutions. Which is why you can determine $K_f$ with one solute only to use that same constant to later determine the concentration of another solute.
The following is multiple choice question (with options) to answer.
The temperature dependence of solubility can be exploited to prepare what solutions of certain compounds? | [
"supersaturated",
"isolated",
"instantiated",
"mineralized"
] | A | The temperature dependence of solubility can be exploited to prepare supersaturated solutions of certain compounds. A solution may be saturated with the compound at an elevated temperature (where the solute is more soluble) and subsequently cooled to a lower temperature without precipitating the solute. The resultant solution contains solute at a concentration greater than its equilibrium solubility at the lower temperature (i. , it is supersaturated) and is relatively stable. Precipitation of the excess solute can be initiated by adding a seed crystal (see the video in the Link to Learning earlier in this module) or by mechanically agitating the solution. Some hand warmers, such as the one pictured in Figure 11.18, take advantage of this behavior. |
SciQ | SciQ-2574 | inorganic-chemistry, crystal-structure, geochemistry, glass, minerals
You are correct. The main difference is that sand is crystalline and glass is not—it is amorphous.
The main component (> 95%) of common yellow sand is quartz (the mineral whose composition is SiO2). Note that not all sand is quartz. There are white sands containing calcite (CaCO3) and black sand (containing various heavy minerals). But the most common sand is indeed quartz sand: SiO2.
Glass, the type you see in your everyday life, on the other hand, is not composed of pure SiO2. It has a bunch of other additives such as Na, K, B, and others. This is done to modify the properties of the glass and make it more suitable for human use. It doesn't matter much though for our discussion.
So if they are made of the same thing, why the difference? The answer is cooling rate. If you cool molten SiO2 slow enough, the atoms have enough time to organize themselves into a crystalline structure. In the case of pure SiO2, this is a network of SiO4 tetrahedra: One silicon atom surrounded by four oxygens. If it cools too fast, then the crystalline structure does not form. It may be completely amorphous, or form into a sub-microscopic array of SiO2 crystals in various structures (CT-opal for example).
What determines the cooling rate? Well, in the case of glass it is a matter of minutes. You've seen glass making: The glass is molten and very quickly it solidifies to a solid. In contrast, most of the quartz sand you're seeing is actually broken fragments of rocks called granite. This type of rock has abundant quartz in it, and it forms deep underground (as in 10s of kilometers) at very slow cooling rates. While a glass maker can take his glass and let it cool in the atmosphere or in water, molten silicate magma ("glass") deep in the Earth is surrounded by rocks that are in the hundreds of degrees. This slow cooling facilitates crystallization of the SiO2 into quartz rather than glass. How slow is this? At least tens of years, more commonly hundreds or even thousands of years. This is much slower than the seconds and minutes in glass making.
The following is multiple choice question (with options) to answer.
Glasses are mixtures of oxides, the main component of which is silica (sio2). silica is called the glass former, while additives are referred to as this? | [
"addition modifiers",
"natural modifiers",
"glass modifiers",
"glass actors"
] | C | ♦ Glasses are mixtures of oxides, the main component of which is silica (SiO2). Silica is called the glass former, while additives are referred to as glass modifiers. The crystalline lattice of the glass former breaks down during heating, producing the random atomic arrangements typical of a liquid. Adding a modifier and cooling the melt rapidly produces a glass. How does the three-dimensional structure of the glass differ from that of the crystalline glass former? Would you expect the melting point of a glass to be higher or lower than that of pure SiO2? Lead glass, a particular favorite of the Romans, was formed by adding lead oxide as the modifier. |
SciQ | SciQ-2575 | biochemistry, metabolism, enzymes, human-physiology, fat-metabolism
[My de-emphasis of glycolysis]
To understand this requires one to consider the different functions of liver and adipose tissue and how they should respond to the fed and fasted state. Then one can appreciate that the differences in enzyme complement are one of the ways by which this is achieved. (The other is their differential responses to hormones.)
The role of the adipose tissue is to store fat (triglycerides) in the fed state and make it available for the other tissues in the body in the fasted state.
The role of the liver is to divert metabolism to the synthesis of fat in the fed state (at the appropriate stage) and to ensure that there is a supply of glucose in the fasted state for those tissues that depend on it (brain, erythrocytes) or a supply of ketone bodies for the brain.
The substrates for triglyceride synthesis are L-glycerol phosphate and fatty acids. There are two enzymes that can catalyse its production, glycerokinase (glycerol kinase) in the liver and glycerol 3-phosphate dehydrogenase in both liver and adipose tissue, as shown in my diagram below:
Fed State
The liver has surplus glucose so it can switch to fatty acid production from acetyl CoA (from pyruvate) and generate L-glycerol phosphate from the dihydroxyacetone phosphate intermediate of glycolysis, catalysed by glycerol 3-P dehydrogenase. This allows the synthesis of triglyceride, which is exported as lipoprotein.
When the triglyceride reaches the adipose tissue it is broken down to fatty acids and glycerol by the hormone-sensitive lipase. The glycerol cannot be used by the adipose tissue, but adipose tissue can synthesize L-glycerol phosphate itself in the same way as liver as there is glucose available for glycolysis in the adipose tissue. Hence the triglyceride can be resynthesized and stored.
Fasted State
The following is multiple choice question (with options) to answer.
What type of tissue produces and secretes several hormones involved in lipid metabolism and storage? | [
"hormonal tissue",
"somatic tissue",
"adipose tissue",
"metabolism tissue"
] | C | Adipose Tissue Adipose tissue produces and secretes several hormones involved in lipid metabolism and storage. One important example is leptin, a protein manufactured by adipose cells that circulates in amounts directly proportional to levels of body fat. Leptin is released in response to food consumption and acts by binding to brain neurons involved in energy intake and expenditure. Binding of leptin produces a feeling of satiety after a meal, thereby reducing appetite. It also appears that the binding of leptin to brain receptors triggers the sympathetic nervous system to regulate bone metabolism, increasing deposition of cortical bone. Adiponectin—another hormone synthesized by adipose cells—appears to reduce cellular insulin resistance and to protect blood vessels from inflammation and atherosclerosis. Its levels are lower in people who are obese, and rise following weight loss. |
SciQ | SciQ-2576 | organs, lifespan
Title: Organs lifespan out of the body What organ can be conserved outside of the body for the longest time and still function when reimplanted? Depends what you consider an organ. Typically though it's the cells which require the most metabolic activity which have the shortest life span. The kidney is the most of the major internal organs with up to 36 hours with liver coming second at up to 16 hours.
The following is multiple choice question (with options) to answer.
What is the process in which organ systems work to maintain a stable internal environment? | [
"organ balance",
"ketosis",
"homeostasis",
"homogeneity"
] | C | The process in which organ systems work to maintain a stable internal environment is called homeostasis. Keeping a stable internal environment requires constant adjustments. Here are just three of the many ways that human organ systems help the body maintain homeostasis:. |
SciQ | SciQ-2577 | history, autoimmune, diabetes-mellitus
Title: When was it determined that Type 1 Diabetes is an autoimmune disease? I just found out today that type 1 diabetes is an autoimmune disease. When was this discovered? This question has two answers: The difference was first described in 1936 by Harold Percival Himsworth, which described it in this article.
At this time it was established that there are two forms of Diabetes, one sensitive to insuline while the other is not.
The terms Diabetes type 1 and 2 where established somewhere between 1974 and 1976, for details see the review "The discovery of type 1 Diabetes".
The following is multiple choice question (with options) to answer.
What must people with type 1 and type 2 diabetes frequently check? | [
"blood density levels",
"blood glucose levels",
"muscle glucose levels",
"blood plasma levels"
] | B | You can greatly reduce your risk of developing type 2 diabetes by maintaining a healthy body weight. Some cases of type 2 diabetes can be cured with weight loss. However, most people with the disease need to take medicine to control their blood glucose. Regular exercise and balanced eating also help. Like people with type 1 diabetes, people with type 2 diabetes must frequently check their blood glucose. |
SciQ | SciQ-2578 | genetics, allele
Title: What is meant by 'identical alleles'? I read in my book that "two alleles are considered to be homozygous if they are identical". But at the same time I read the definition of allele to be:
genes which code for a pair of contrasting traits are called alleles
My doubt is that how can they be both contrasting (different) and identical (same) at the same time
What I think is that if homozygous is somehow a part of specific conditions in alleles then how can it be different from alleles itself. These are just issues with singular and plural and whether you refer to individual copies or categories/types.
Two of the same allele copies are the same allele (category/type). Two different alleles (copies) can also be different (categories/types).
In the context of a diploid individual, they have two instances of each gene so therefore two alleles; these alleles can be the same or different.
So you can say you have two "red flower" alleles, meaning two copies of the red flower allele. Or you can have a population that has two alleles for flower color: red flower alleles or white flower alleles.
The same is used in English for other things. You might say a farm grows two fruits, peaches and plums, and also that I have two fruits in my hand, both peaches. You need to use surrounding context to recognize whether copy or type is meant.
The following is multiple choice question (with options) to answer.
What is it called when two alleles are both expressed in the heterozygous individual? | [
"weak dominance",
"shared dominance",
"codominance",
"low dominance"
] | C | Codominance is when two alleles are both expressed in the heterozygous individual. |
SciQ | SciQ-2579 | species-identification, arachnology
Title: Can somebody identify this species of spider? I ran into this cool looking spider in my yard in Banjaluka, Bosnia and Herzegovina. It's about the size of a fingernail and unusually shaped (spherical). Could it be poisonous? The white cross on the body makes me think it could well be an Araneus diadematus. It is quite common and not dangerous for humans. It paralyzes its preys using some venom, though.
The following is multiple choice question (with options) to answer.
What part of a spider is equipped with poison glands? | [
"baleen",
"vacuole",
"chelicerae",
"pedipalps"
] | C | |
SciQ | SciQ-2580 | equilibrium, water, salt
Title: Would adding a water soluble salt (e.g. NaCl) affect a water sensitive reaction? Let's take for example a reaction that would benefit from having less water in it, ester formation from alcohol and acid. We know that the equilibrium can be shifted to the right (ester formation) if water is constantly removed through distillation. My question is: would adding an excess of NaCl affect the reaction and push the reaction to the right?
The water would solvate the NaCl and theoretically be "preoccupied." I would like to think that water adding back to the ester to form an alcohol and acid would be more energetically favourable, but I don't really have enough knowledge to answer that on my own. Any thoughts? Esterification
$\ce{R_1-COOH + HO-R_2 <=> R1-COO-R2 + H2O}$
has the equilibrium constant, expressed in compound activities:
$$K = \frac{a_\mathrm{ester} \cdot a_\mathrm{\ce{H2O}} }{ a_\mathrm{acid} \cdot a_\mathrm{alkohol}}$$
The water activity is decreased by dissolved salts by 2 ways:
decreasing the molar fraction of water by dissolved salt
decreasing its activity coefficient by bounding it by ion hydration.
As the result, dissolved salts decrease the numerator of the equilibrium expression and shift the equilibrium toward production of ester.
Present dissolved salts will partially affect activities of the acid and the alcohol as well, but in lesser extend.
The following is multiple choice question (with options) to answer.
Esters are neutral compounds that undergo what process, which is a reaction with water? | [
"cellular respiration",
"hydrolysis",
"replication",
"osmosis"
] | B | conditions. Esters are neutral compounds that undergo hydrolysis, a reaction with water. Under acidic conditions, hydrolysis is essentially the reverse of esterification. When carried out under basic conditions, the process is called saponification. Inorganic acids also react with alcohols to form esters. Some of the most important esters in biochemistry are those formed from phosphoric acid. Amines are nitrogen-containing organic molecules derived from ammonia (NH3). A primary (1°) amine (RNH2) has one organic group bonded to the nitrogen atom, a secondary (2°) amine (R2NH) has two organic groups bonded to the nitrogen atom, and a tertiary (3°) amine (R3N) has three organic groups bonded to the nitrogen atom. Amines are basic compounds that react with strong acids to produce ammonium (NH4+) salts. A cyclic compound in which the ring contains one or more noncarbon atoms is called a heterocyclic compound. There are many heterocyclic amines, including many physiologically important ones. Alkaloids are heterocyclic amines found in many plants. Caffeine, nicotine, and cocaine are familiar alkaloids. Organic compounds containing a carbonyl group bonded to a nitrogen atom are amides, and the carbon-to-nitrogen bond is an amide linkage (or a peptide linkage). Most amides are colorless and odorless, and the lighter ones are soluble in water. Because they are polar molecules, amides have comparatively high boiling points and melting points. Amides are synthesized from carboxylic acids and NH3 or amines. Amides are neutral compounds. They resist hydrolysis in water, but acids, bases, and enzymes catalyze the reaction. |
SciQ | SciQ-2581 | evolution
Title: How to define "evolution"? The standard answer found in intro course to evolutionary biology to the question:
what is evolution?
is:
It is a change in allele frequency over time!
I believe a complete definition should encompass the following concepts:
mutations
copy number variation (CNV)
codon usage
chromosome numbers
phenotypic change (whether heritable or not)
Complex phenotypic trait such as plasticity and developmental noise
maybe some other things...
My questions are:
Would it be worth it to talk about phenotype in a definition of evolution?
What are the alternative definitions that have been proposed?
What is your definition?
Note: I would rather talk about genetic evolution, but if you think it is worth making one definition for genetic and cultural (and some other stuff maybe) evolution, you're free to suggest it! What is evolution?
In a non-biological sense, evolution means change:
"a process of [...] change"
Biological evolution (seeing as this is Biology stack exchange) then needs to be tweaked to give a biologically specific context. Many textbooks etc. give definitions of evolution and here are a few good ones from across the history of evolutionary biology:
Charles Darwin:
"Descent with modification".
Mark Ridley1:
"Evolution means change, change in the form and behaviour of organisms between generations. ... When members of a population breed and produce the next generation we can imagine a lineage of populations, made up of a series of populations through time. Each population is ancestral to the descendant population in the next generation: a lineage is an ancestor-descendent series of populations. Evolution is then change between generations within a population lineage."
Brian and Deborah Charlesworth2:
"Evolution means cumulative change over time in the characteristics of a population of living organisms. ... All evolutionary changes require initially rare genetic variants to spread among the members of a population, rising to high frequency..."
All of these have a common theme. Biological information is moving through time, descending with a degree of directionality (e.g. parent $\rightarrow$ offspring), and the information is modified with time.
Personally I would define evolution as:
The following is multiple choice question (with options) to answer.
Evolution occurs because of changes in what over time? | [
"mitochondria",
"atoms",
"alleles",
"genomes"
] | C | We now know how variation in traits is inherited. Variation in traits is controlled by different alleles for genes. Alleles, in turn, are passed to gametes and then to offspring. Evolution occurs because of changes in alleles over time. How long a time? That depends on the time scale of evolution you consider. |
SciQ | SciQ-2582 | thermodynamics, physical-chemistry, chemical-potential, combustion
Title: How to thermodynamically understand process of burning a piece of coal? Let's imagine that I have a match in hand and nugget of coal on my desk. Then I light up the match and place it for few seconds near the coal so a tiny piece of nugget catches fire.
Then another piece catches fire, then another and soon all the nugget is burnt down.
How did it happen? I gave the nugget just enough heat to burn the first piece. Where does come energy to burn the rest of nugget from? It is called combustion, and it happens in materials which have a lower energy content when their component molecules join with the oxygen in the atmosphere, than when in a solid/liquid structure. When energy is given to start the fire the piece of coal burns and releases energy with excess enough to sustain the reaction and leave heat energy for use.
Combustion is a high-temperature exothermic chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke.
The following is multiple choice question (with options) to answer.
When does coal release most of its energy? | [
"when falling",
"when burning",
"when compressed",
"when forming"
] | B | To prepare coal for use, the coal is first crushed into powder and burned in a furnace. Like other fuels, coal releases most of its energy as heat when it burns. The heat from the burning coal is used to boil water. This makes steam. The steam spins turbines, which creates electricity. |
SciQ | SciQ-2583 | particle-physics, dimensional-analysis, elementary-particles
Title: Minimal size of physical entities I know that per current knowledge there are layers of size of physical entities going from elementary particles to molecules (and from molecules to molecular structures such as bricks or organism cells and further into a tools, buildings, machines and organism bodies).
I understand that the notion between human scientists is that the "size" or "scale" of elementary particles (whatever these will be) is finite;
that is: Elementary particles are the smallest physical entities in this universe and there can't be anything smaller than them in this universe.
Is there a theory according to which infinity for how small physical entities can be, is real?
I am not talking about a theory theorizing even more and smaller elementary particles than accepted, but rather a theory that its theoreticians are "irreverent" to suggest that there is no such thing as "elementary" particle by the sense that one could always go down in the "scale" of size.
One could be further irreverent to derive from such theory that because time passes faster in micro than in macro, entire universes could exist and might appear to an observing organism as a "particle" with a lifespan of way less than a millisecond.
Also, of course the opposite question (Can there be maximal size of physical entities?) is dependent on if the cosmos is finite or infinite, but the current question doesn't seem to me such.
Is there a theory according to which infinity for how small physical entities can be, is real?
You have to define what the definition of "small" is . If you means size, the standard model of particle physics has elementary particles as point particles, no size at all, so they fulfill already the "smallnes".
If you mean if their invariant mass can be very small, already the photon the gluon and maybe the graviton have zero mass in the mainstream models.
am not talking about a theory theorizing even more elementary particles than accepted, but rather a theory that its theoreticians are "irreverent" to suggest that there is no such thing as "elementary" particle by the sense that one could always go down in the "scale" of size.
The following is multiple choice question (with options) to answer.
What was once believed to be the smallest of all particles, as dalton's theory proposed? | [
"nucleus",
"neutron",
"atom",
"molecule"
] | C | Dalton’s theory was soon widely accepted. Most of it is still accepted today. The only part that is no longer accepted is his idea that atoms are the smallest particles. Scientists now know that atoms consist of even smaller particles. |
SciQ | SciQ-2584 | terminology, elements, rare-earth-elements
Title: Why are actinides not commonly included in rare earth metals? According to the German Wikipedia, the rare earth metals include all elements of the third side group except actinium, and all lanthanides.
Zu den Metallen der Seltenen Erden gehören die chemischen Elemente der 3. Nebengruppe des Periodensystems (mit Ausnahme des Actiniums) und die Lanthanoide – insgesamt also 17 Elemente.
The following is multiple choice question (with options) to answer.
The actinides are all what type of elements? | [
"multiple",
"nuclear",
"large",
"radioactive"
] | D | actinide: The actinides are the 14 elements from thorium (atomic number 90) to lawrencium (atomic number 103). The sublevel is in the process of being filled. The actinides are all radioactive elements and only the first four have been found naturally on Earth. |
SciQ | SciQ-2585 | species-identification, zoology, entomology
Title: Species identification; clusters of big plump red bugs in Taipei I saw these red insects in Taipei near XinBeitou MRT station in the last week of April 2017, around lunch time. They were fairly active and would keep checking each other out with their antennae for a moment and then move on to the next. What struck me was the wide range of sizes and development in the groups. I didn't notice any feeding or mating that I could recognize, just a lot of walking around and checking each other out.
There are plenty of birds around (this is quite a green area) but I didn't notice any interest by birds in eating them.
I've also included a screenshot from google maps so you can see the location and the trees growing in these concrete structures.
The body of the largest individual is probably 2.5 centimeters long. I'm fairly certain these true bugs belong to the species Leptocoris vicinus, and carry the nickname of "soapberry bugs", which is specific to the subfamily Serinethinae. They're quite common in urban areas of Southeast Asia, which coincides nicely with where you encountered them.
Also, you had mentioned,
There are plenty of birds around (this is quite a green area) but I didn't notice any interest by birds in eating them.
Soapberry bugs, as well as many other types of insects, are able to freely congregate in large numbers, and in such exposed places, due to their bright coloration. Having such a bright color may indicate to some predators that the prey in consideration is toxic, a phenomenon referred to as aposematism.
source
source
And then, here's a map of their distribution, with Taipei holding marker #37. (source)
An interactive version of this map can be found here.
The following is multiple choice question (with options) to answer.
What type of feeders are sea lilies and feather stars? | [
"bottom feeder",
"suspension feeders",
"silt feeders",
"deposit feeder"
] | B | Explore the sea star’s body plan (http://openstaxcollege. org/l/sea_star) up close, watch one move across the sea floor, and see it devour a mussel. Brittle stars belong to the class Ophiuroidea. Unlike sea stars, which have plump arms, brittle stars have long, thin arms that are sharply demarcated from the central disk. Brittle stars move by lashing out their arms or wrapping them around objects and pulling themselves forward. Sea urchins and sand dollars are examples of Echinoidea. These echinoderms do not have arms, but are hemispherical or flattened with five rows of tube feet that help them in slow movement; tube feet are extruded through pores of a continuous internal shell called a test. Sea lilies and feather stars are examples of Crinoidea. Both of these species are suspension feeders. Sea cucumbers of class Holothuroidea are extended in the oral-aboral axis and have five rows of tube feet. These are the only echinoderms that demonstrate “functional” bilateral symmetry as adults, because the uniquely extended oral-aboral axis compels the animal to lie horizontally rather than stand vertically. |
SciQ | SciQ-2586 | molecular-biology, cell-biology
This rate decreases dramatically as radius of the cell increases. For example a cell with double the diameter (2 micrometers) has a volume eight times larger, so collisions between any two molecules take 8 times ($2^3$) as long to occur (in other words, it takes molecules 8 times longer to "find" each other). This is one reason why there is a kind of upper limit on the size of an individual cell. Bigger organisms are bigger because they have more cells, not because they have larger cells.
The field of biology concerned with how likely it is for a reaction to occur is called enzyme kinetics. A related field, which deals with how frequently molecules collide is called statistical mechanics.
The following is multiple choice question (with options) to answer.
What are the proteins called that speed up biochemical reactions in cells? | [
"hormones",
"carbohydrates",
"enzymes",
"peptides"
] | C | Enzymes are proteins that speed up biochemical reactions in cells. Antibodies are proteins that target pathogens for destruction. |
SciQ | SciQ-2587 | dating
Title: Can we carbon-date the remains of homo floresiensis found in 2003? According to the Wikipedia article on the species Homo floresiensis, the remains discovered in 2003 consist of unfossilized bones. I would assume that means they are still composed of the original organic material left behind when the human specimen died thousands of years ago. Shoudn't that mean radiocarbon dating would be a good method to date the reamains?
Many articles on Homo floresiensis also discuss how the remains were originally dated to ~12,000 years ago, but that this estimate was later revised to 60–100,000 years ago. However, everything I can find indicates that mostly geological dating methods were used, not radiometric dating.
Why not? The Wikipedia entry on carbon dating says that it can only be used reliably to date specimens up to ~50,000 years, but could carbon dating then at least place a lower limit on the age of these remains? And why wouldn't it have been used back when they thought the specimens were only ~12,000 years old? ScienceMag says:
The following is multiple choice question (with options) to answer.
What isotope of carbon is typically used to date ancient items? | [
"carbon 12",
"nitrogen 14",
"uranium 14",
"carbon 14"
] | D | |
SciQ | SciQ-2588 | planet, solar-system
Title: Considering our methods of exploration, how likely is it that there are unfound planets (not dwarf planets) in our solar system? I think it's probably unlikely that there are more planets between Mercury and Mars, but out from Jupiter, there's lots of empty space between the planets. Could there be some small planet hidden out there? There are no undiscovered planets between the sun and Neptune.
Objects closer (to Sun) than Neptune that are large enough to be considered planets (and not dwarf planets) can't remain 'hidden'. If it's there, the light from the sun will bounce off it and we will see it. As it moves in its orbit, we will notice the position in the sky change, so we will know it isn't a star.
I would like to give a more broad answer to this question though:
What is the maximum size of an undiscovered solar system object and how does it change as you get further from the sun?
The further out a solar system object is, the harder it is to detect. The rate at which it gets harder is severe; the light we receive from an object scales roughly as $1/r^4 $.
($1/r^2$ for the light travelling from the Sun to the object, and again, $1/r^2$ for the light travelling from the object to us on earth).
We are able to detect some very small earth-crossing asteroids. Some as small as ~50 metres across. At a guess (and this is just based on my intuition, not any calculations), there are probably no undiscovered objects larger than 1 km close to earth.
As you travel to the outer solar system (Jupiter to Neptune), the number of bodies increases dramatically. There are currently ~700,000 known solar system bodies and most of them occur in this area. It is believed that all asteroids larger than 10 km have been found.
The following is multiple choice question (with options) to answer.
What two planets is the asteroid belt found between? | [
"Mars and Earth",
"Jupiter and Saturn",
"Jupiter and Earth",
"mars and jupiter"
] | D | Asteroids are irregularly-shaped, rocky bodies that orbit the Sun. Most of them are found in the asteroid belt, between the orbits of Mars and Jupiter. |
SciQ | SciQ-2589 | everyday-chemistry
Title: How does a fire start? I know that fire in a few words is the exothermic reaction of a fuel with an oxidizing agent, but I can't fully understand what exactly happens to piece of wood when it is ignited. How do molecules start producing a flame? In other words, what is the chemistry behind the production of flame? https://www.youtube.com/watch?v=B0E4PX3e3RE It feels somewhat weird to answer my own question but I think this video describes exactly what I wanted. As it supports, when heat is applied to a piece of wood, some bonds of the molecules that make up wood, break and thus different compounds are formed. These compounds are not held back by some force and so they are released in the air. When these compounds meet atmospheric oxygen, under heat (=energy), they burn and thus more heat is released along with carbon dioxide and water. That stage can be described as ignition. Finally, this produced heat is able to preserve the fire.
The following is multiple choice question (with options) to answer.
When wood is burned what kind of energy allows the wood to burn? | [
"physical",
"chemical",
"carbon",
"radiation"
] | B | Chemical energy is stored in wood and released when the wood burns. |
SciQ | SciQ-2590 | crystals
Title: What is the symmetry difference between simple-cube and body-centered-cube structures If the lattice types are categorized according to the point group symmetries, then what is the difference, for example, between sc and bcc structures? In 3D there are 7 lattice systems which are classes of lattices having the same point group. One of them is the class of cubic lattices. This class contains three different Bravais lattices which are distinguished by their translation group.
The following is multiple choice question (with options) to answer.
The cubic crystal system is composed of how many different types of unit cells? | [
"four",
"five",
"one",
"three"
] | D | Unit cells occur in many different varieties. As one example, the cubic crystal system is composed of three different types of unit cells: (1) simple cubic , (2) face-centered cubic , and (3) body-centered cubic . These are shown in three different ways in the Figure below . |
SciQ | SciQ-2591 | thermodynamics
$$\Delta G_{\text{total}} = \pu{1 mol }\int_0^1 \left[ \Delta_r G^\circ\text{(dissolution)} + R T \ln(x) dx \right] $$
Taking constants and constant factors out of the integral, we get:
$$\Delta G_{\text{total}} = \pu{1 mol } \Delta_r G^\circ\text{(dissolution)} + \pu{1 mol } R T \int_0^1 \ln(x) dx$$
The value of the integral is negative one, so overall we have:
$$\Delta G_{\text{total}} = \pu{1 mol } (\Delta_r G^\circ\text{(dissolution)} - R T) $$
3. Running the reaction at a constant concentration of 1 M
Here, we will use a process that keeps the glucose concentration constant. We place a semi-permeable membrane into the pure water, separating it into two compartments. At the beginning, one compartment (the one in contact with the solid glucose) has a volume of zero. As glucose dissolves, we move the membrane, increasing the volume of the compartment so that the glucose concentration remains at 1 mol/L. We keep doing that over the course of the dissolution reaction until the volume of solution is one liter at the end (and the volume of pure water is zero).
Because all species are at standard state at all time, we can use the standard Gibbs energy of reaction without a term correcting for concentration. This is one component of the total change in Gibbs energy. The other one is work against the osmotic pressure difference between pure water and 1 M glucose:
$$ w = \Pi \times V = \Delta c R T \times V = \pu{1 mol } R T$$
This work represents the difference between dissolving 1 mol glucose into pure water and dissolving 1 mol glucose into a 1 M glucose solution, so we have to add (or subtract?) it to get the Gibbs energy of our original process.
Which calculation is correct, and where are the problems with the other ones?
The following is multiple choice question (with options) to answer.
In which solution is the amount of dissolved material equal both inside and outside of the cell? | [
"hypotonic",
"isotonic",
"exothermic",
"supersaturated"
] | B | An isotonic solution is a solution in which the amount of dissolved material is equal both inside and outside of the cell. Water still flows in both directions, but an equal amount enters and leaves the cell. |
SciQ | SciQ-2592 | observable-universe
Title: What is the rarest stable element in the universe? I am making a hard sci-fi game with a focus on realism, in this game there is a need for a hard element to base money off of. Similar to how gold is used on earth.
I know there are lots of elements that only exist for seconds at a time that are technically rare but wouldn't work as a currency. What element in the universe would aliens be most likely to be trading back and forth? Within our solar system the least abundant, stable and non radioactive element is Tantalum, atomic number 73.
Its chemical inertness,
make it valuable for laboratory and industrial equipment such as reaction vessels and vacuum furnaces
Back in the 1970s and 1980s it was popular to make electronic capacitors using tantalum because they were smaller in size than the electronic capacitors that were made previously. This made them popular for use in hand held calculators and other similar small electronic devices.
Tantalum is dark (blue-gray), dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity. The metal is renowned for its resistance to corrosion by acids.
Element 43, Technetium, is very rare, radioactive and has a short half life. On Earth it is a synthetic material and wouldn't be suitable for your purposes.
Similarly, Promethium, element 61, is rare, but radioactive. The same applies for elements 84 through to 89.
The following is multiple choice question (with options) to answer.
What element is the most common element in the universe? | [
"nitrogen",
"hydrogen",
"helium",
"carbon"
] | B | An element is a pure substance. It cannot be separated into any other substances. There are more than 90 different elements that occur in nature. Some are much more common than others. Hydrogen is the most common element in the universe. Oxygen is the most common element in Earth’s crust. Figure below shows other examples of elements. Still others are described in the video below. |
SciQ | SciQ-2593 | mass, density, volume
Title: Confused about volume, density and mass, help! I got into an argument with my friend, which cast confusion on my understanding of density and its relationship to volume. I'm hoping to get some clarity. The argument involved describing density in terms of volume. Let's say you define a sphere in empty space. You choose a point, apply the formula for a sphere, and now you have a sphere. Not a sphere OF anything other than space, just a spacial, theoretical sphere. No particles, massless or otherwise (this is a thought experiment). What is the density of that sphere? Is it zero, or is it undefined? I know density can be defined as p = m/v. But in a theoretical sphere, which HAS volume, should we call mass zero, because there is none? Or is it undefined because a theoretical sphere really isn't related to mass at all? If it IS undefined, does that mean it makes no sense to relate density to volume because density is only a property of mass?
The answer, to me, seems to be that in fact it makes no sense to talk about the density of a massless object. Sorry if I answered my own question, but I would still like clarity. If someone could help guide me through the assumptions I'm making about reality and math and how they relate, I'd really appreciate it. Theoretically speaking, in order for something (usually particles) to be massless, it has to be travelling in the speed of light. In quantum theory, uncertainty principle states that the position and momentum of such particle cannot be accurately determined, therefore it is not possible to measure the volume of the particle. So it is generally assumed that the volume is too small and/or insignificant.
Regarding your question, I think that the simple answer would be; a massless object would have no volume nor density, or immeasurable. Take your pick.
The following is multiple choice question (with options) to answer.
What is the term for anything that has mass and volume? | [
"gass",
"matter",
"liquid",
"energy"
] | B | Matter is anything that has mass and volume. Mass is the amount of matter in a substance. Volume is the amount of space matter takes up. |
SciQ | SciQ-2594 | volcanology, volcanic-hazard
In any case, if you do manage to reach the last eruption site, don't walk on the lava flow crust in the hope to see some active lava. I did it with a group of visiting volcanologists, guided by local volcanologists who had been in the field every day for six months. They knew the site very well and we just followed their tracks. It can remain dangerous for months. I hope that you'll get to see this wonder of nature, but don't risk your life for it!
The following is multiple choice question (with options) to answer.
What is in danger of happening when thick magma is formed? | [
"continuous eruptions",
"earthquakes",
"explosive eruptions",
"focused eruptions"
] | C | Composite volcanoes are also called stratovolcanoes. This is because they are formed by alternating layers (strata) of magma and ash ( Figure below ). The magma that creates composite volcanoes tends to be thick. The steep sides form because the lava cannot flow too far from the vent. The thick magma may also create explosive eruptions. Ash and pyroclasts erupt into the air. Much of this material falls back down near the vent. This creates the steep sides of stratovolcanoes. |
SciQ | SciQ-2595 | thermodynamics, ideal-gas, reversibility
Title: Does $PV=nRT$ hold for the endpoints of an irreversible process? I have read the following:-
$PV=nRT$ holds throughout a reversible process
$PV=nRT$ does not hold throughout an irreversible process because the ideal gas law is only applicable for gases in equilibrium i.e. not suddenly expanding/compressing.
Now, my question is will $PV=nRT$ hold only for the initial and final states (i.e. endpoints) of an irreversible process? I feel this may be possible because the gas will be in equilibrium at the endpoints and not suddenly expanding/compressing. Sure. The processes considered in thermodynamics are always between a starting and a final equilibrium state. Even if the real process may be too fast to allow the system to remain close to equilibrium states, we implicitly assume that the initial state is an equilibrium state and that after the final state has been reached, enough time to equilibrate is given to the system.
The following is multiple choice question (with options) to answer.
The important equation pv = nrt holds true for substances in what state of matter? | [
"solids",
"liquids",
"products",
"gas"
] | D | PV = nRT This equation is known as the ideal gas law. An ideal gas is defined as a hypothetical gaseous substance whose behavior is independent of attractive and repulsive forces and can be completely described by the ideal gas law. In reality, there is no such thing as an ideal gas, but an ideal gas is a useful conceptual model that allows us to understand how gases respond to changing conditions. As we shall see, under many conditions, most real gases exhibit behavior that closely approximates that of an ideal gas. The ideal gas law can therefore be used to predict the behavior of real gases under most conditions. As you will learn in Section 10.8 "The Behavior of Real Gases", the ideal gas law does not work well at very low temperatures or very high pressures, where deviations from ideal behavior are most commonly observed. |
SciQ | SciQ-2596 | 4th dimension, now the boundary is 5904 and the interior 4096 - the boundary is now larger.
Even for smaller and smaller boundary lengths, as the dimension increases the boundary volume will always overtake the interior.
The best way to "understand" it (though it is IMHO impossible for a human) is to compare the volumes of a n-dimensional ball and a n-dimensional cube. With the growth of n (dimensionality) all the volume of the ball "leaks out" and concentrates in the corners of the cube. This is a useful general principle to remember in the coding theory and its applications.
The best textbook explanation of it is in the Richard W. Hamming's book "Coding and Information Theory" (3.6 Geometric Approach, p 44).
The short article in Wikipedia will give you a brief summary of the same if you keep in mind that the volume of a n-dimensional unit cube is always 1^n.
I hope it will help.
The following is multiple choice question (with options) to answer.
The measurement of the extent of something along its greatest dimension is its what? | [
"portion",
"length",
"depth",
"stretch"
] | B | Length is the measurement of the extent of something along its greatest dimension. The SI basic unit of length, or linear measure, is the meter (m). All measurements of length may be made in meters, though the prefixes listed in various tables will often be more convenient. The width of a room may be expressed as about 5 meters (m), whereas a large distance, such as the distance between New York City and Chicago, is better expressed as 1150 kilometers (km). Very small distances can be expressed in units such as the millimeter or the micrometer. The width of a typical human hair is about 20 micrometers (μm). |
SciQ | SciQ-2597 | newtonian-mechanics, pressure, fluid-statics, free-body-diagram, buoyancy
Title: What force does a floating object exert on the liquid it is floating on? When something floats, it is due to the buoyant force from the liquid onto the object, but what force does the object exert in response down on the liquid? I feel as if the object would have to exert a downward force on the liquid due to Newton's Third Law, but I haven't been able to figure out what it would be. At the bottom of the floating mass its weight would be pushing downwards on the water, and the water pressure on the bottom would be pushing upwards on the object. This would be the up and down action reaction pair from its buoyancy. There is also a sideways action reaction of water pressure on opposite sides of the object but they cancel each other out. As you know, a buoyant object displaces its weight in water so it will make the water level rise the same as adding its weight of water would.
The following is multiple choice question (with options) to answer.
What force explains why objects may float in water? | [
"warm force",
"gravity force",
"cool force",
"buoyant force"
] | D | What explains buoyant force? Recall from the earlier lesson "Pressure of Fluids" that a fluid exerts pressure in all directions but the pressure is greater at greater depth. Therefore, the fluid below an object exerts greater force on the object than the fluid above the object. This is illustrated in Figure below . Buoyant force explains why objects may float in water. No doubt you’ve noticed, however, that some objects do not float in water. If buoyant force applies to all objects in fluids, why do some objects sink instead of float? The answer has to do with their weight. |
SciQ | SciQ-2598 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Which organelle is made up of 5 to eight cup shaped, membrane covered stacks of discs known as cisternae? | [
"golgi apparatus",
"vacuole",
"nucleus",
"endoplasmic reticulum"
] | A | The Golgi apparatus is usually made up of five to eight cup-shaped, membrane-covered stacks of discs called cisternae (singular, cisterna ), as shown in Figure below . Both plant and animal cells have a Golgi apparatus. A typical mammalian cell will have 40 to 80 of these stacks. While plant cells can have up to several hundred Golgi stacks scattered throughout the cytoplasm. In plants, the Golgi apparatus contains enzymes that synthesize some of the cell wall polysaccharides. |
SciQ | SciQ-2599 | acoustics, air, displacement
You can see the derivation of the above at http://www.insula.com.au/physics/1279/L14.html and if you look for problem # W4 on that page you will find the calculation for a pressure level of 28 mPa at 1 kHz giving 11 nm displacement amplitude. Given that the limit of detectable sound level is about 1000x smaller, my numbers above are quite reasonable.
So the real answer to your "headline" question ("how much air needs to be displaced to generate an audible sound") is
The equivalent of one layer of atoms is more than enough
Impressive, how sensitive the ear is. And bats and dogs have even better hearing, I'm told.
The following is multiple choice question (with options) to answer.
How many bones does the mammalian middle ear have? | [
"twelve",
"four",
"three",
"two"
] | C | The mammalian middle ear has three tiny bones that carry sound vibrations from the outer to inner ear. The bones give mammals exceptionally good hearing. In other vertebrates, the three bones are part of the jaw and not involved in hearing. |
SciQ | SciQ-2600 | zoology, sensation
Title: Can animals that rely heavily on sonar sense colour? Apparently there're species around as rely heavily on sonar to sense the world around them.
E.g. Bat, Dolphin, Whale ...
The humans, and other terrestrial beings in a lighted world are capable of distinguishing colour in varying degrees of acuity. Is this ability to sense colour in our environment applicable to species (terrestrial, avian, and marine) that rely heavily on sonar? Any animal using sound cannot sense color though sonar directly, though these animals are not entirely blind and can probably see colors in the infrared we can't.
Even on the darkest night there is some light around and all bats use this. Old World fruit bats have colour vision, which is useful to them as they are often quite active in daytime, roosting on trees in exposed positions, rather than tucked away in dark crevices like most microbats, which can see only in black-and-white.
Dolphins have additional senses in addition to seeing they can sense electrical fields. So if an animal has its eyes covered, they will seem to be able to do things you would not expect. Its not the same as seeing the color though.
Such animals using sonar can additionally sense density and hardness as well as other material attributes which would cause the acoustic properties of the material as well as movement.
A hard-bodied insect produces a different quality of echo from one with a soft body, so bats can distinguish between some different groups of insects in this way. They can also determine the size of the object.
What's really interesting is that even human beings can experience this unusual sense. Blind people have learned to echolocate by making clicks with their mouth, and there is a movement to teach this skill.
Anyone can try it. In just an hour or two I was able to tell how close I was to a wall, whether the wall was concrete. I couldn't play video games (2:20 on the link) or see colors though.
The following is multiple choice question (with options) to answer.
What can echinoderms sense with their simple eyes? | [
"light",
"colors",
"electricity",
"shapes"
] | A | Echinoderms lack respiratory and excretory systems. Instead, the thin walls of their tube feet allow oxygen to diffuse in and wastes to diffuse out. Echinoderms also lack a centralized nervous system. They have an open circulatory system and lack a heart. On the other hand, echinoderms have a well-developed coelom and a complete digestive system. Echinoderms use pheromones to communicate with each other. They detect the chemicals with sensory cells on their body's surface. Some echinoderms also have simple eyes (ocelli) that can sense light. Like annelids, echinoderms have the ability to regenerate a missing body part. |
SciQ | SciQ-2601 | organic-chemistry, solutions, synthesis
Title: What does washing and drying a solution mean? After combining two solutions, a direction in a 1970s British chemistry book says to wash the new solution with a mixture of baking soda, table salt, and water. Then it says to dry it with anhydrous magnesium sulfate.
What does washing and drying mean? Do the chemicals get physically mixed together? Doesn't that contaminate the solution? This is standard for purifying substances.
To wash means to add your product solution to an aqueous solution (or just water, but frequently a saturated solution) to a separatory funnel. After shaking, you drain the lower layer (which is usually aqueous). This process removes water soluble impurities. This is frequently repeated.
Drying is accomplished by taking the organic solution of your product and mixing it with a desiccant (usually anhydrous sodium sulfate or anhydrous magnesium sulfate). This removes any water that was left from the washing in the above step. The desiccant may then be removed by filtration.
The following is multiple choice question (with options) to answer.
What do we call water that has been used for cleaning, washing, flushing, or manufacturing? | [
"Grey water",
"wastewater",
"groundwater",
"sewage"
] | B | Fresh water is also preserved by purifying wastewater. Wastewater is water that has been used for cleaning, washing, flushing, or manufacturing. It includes the water that goes down your shower drain and that is flushed down your toilet. Instead of dumping wastewater directly into rivers, wastewater can be purified at a water treatment plant ( Figure below ). When wastewater is recycled, waterborne diseases caused by pathogens in sewage can be prevented. What are some ways you can save water in your own house?. |
SciQ | SciQ-2602 | geophysics, sedimentology
Title: Does dirt compact itself over time? If so, how does this happen? If I were to bury something 10 feet (~3 metres) underground, with loose soil on top, would the ground naturally compact itself over time, until whatever I had buried has dirt tightly pressing against it on all sides?
What if I buried it 50 feet (~15 metres) underground?
If it exists, what is this compaction process called and how does it happen? Soil is a collection of various sized minerals grains, of various types of minerals produced by the weathering of rock. Typical soil minerals are clays, silts and sands.
The properties and behavior of different soil types depends of the composition of the soil: the proportion of clays, silts and sand in a soil. Sandy soils are well draining and clayey soils are sticky.
Between the grains of minerals that comprise a soil are spaces, called pores or pore spaces. The pores can be filled with either water or air, depending the location of water tables and wetting events like rain, snow melts or other forms of water inundation.
The density of a soil is dependent on the degree of compaction of the soil. For to a soil to be compacted, a stress has to be applied to the soil to realign the grains of soil which reduces the total volume of the pores and reduces the amount of air within the pores.
Consolidation of a soil occurs when pore space is reduced and water in a soil is displaced due to an applied stress.
Regarding having something buried and soil compacting around it over time, yes that will occur but it is a question of how much stress the soil experiences, the duration of time and the nature of the soil - sandy or clayey. Something buried for a day without any stresses not much will happen. But, something buried for thousands of years with people and animals walking over it, rain falling on the soil, vibrations from nearby human activity and an occasional earthquake all add to the stresses the soil will experience and increases the degree of compaction or consolidation over time.
The following is multiple choice question (with options) to answer.
What is the name for an area that is covered in water, or at least has soggy soil, during all or part of the year? | [
"a stream",
"coastal zone",
"a crater",
"a wetland"
] | D | Some of Earth’s freshwater is found in wetlands. A wetland is an area that is covered with water, or at least has very soggy soil, during all or part of the year. Certain species of plants thrive in wetlands, and they are rich ecosystems. Freshwater wetlands are usually found at the edges of steams, rivers, ponds, or lakes. Wetlands can also be found at the edges of seas. |
SciQ | SciQ-2603 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
Regulation of the reproductive system is a process that requires the action of hormones from which gland? | [
"adrenal gland",
"pituitary gland",
"thyroid gland",
"salivary gland"
] | B | Hormonal Regulation of the Reproductive System Regulation of the reproductive system is a process that requires the action of hormones from the pituitary gland, the adrenal cortex, and the gonads. During puberty in both males and females, the hypothalamus produces gonadotropin-releasing hormone (GnRH), which stimulates the production and release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary gland. These hormones regulate the gonads (testes in males and ovaries in females) and therefore are called gonadotropins. In both males and females, FSH stimulates gamete production and LH stimulates production of hormones by the gonads. An increase in gonad hormone levels inhibits GnRH production through a negative feedback loop. Regulation of the Male Reproductive System In males, FSH stimulates the maturation of sperm cells. FSH production is inhibited by the hormone inhibin, which is released by the testes. LH stimulates production of the sex hormones ( androgens) by the interstitial cells of the testes and therefore is also called interstitial cell-stimulating hormone. The most widely known androgen in males is testosterone. Testosterone promotes the production of sperm and masculine characteristics. The adrenal cortex also produces small amounts of testosterone precursor, although the role of this additional hormone production is not fully understood. |
SciQ | SciQ-2604 | evolution, dna, natural-selection
It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation.
My question:
Is this possible? Does any similar mechanism exist that we know of? If not, how can so many specific (advanced) evolutionary leaps be otherwise explained? This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed.
Long Story Short
Your question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" to evolve traits. Traits evolve through the biological processes of random mutation and natural selection.
Organisms do not "want" to evolve traits. (Well, OK, I'd love to evolve an extra pair of hands but that is not possible.) Natural selection works by modifying existing traits. Your turtle can stare all she wants at food out of reach but she will not evolve a longer neck. Instead, natural variation exists among neck lengths of the turtles because of variation of the genes that determine features related to overall boxy size. Those individuals with longer necks may be able to get a bit more food, live a little longer, and reproduce a little more. They will pass along their genes to their offspring, so perhaps more of their offspring will also have longer necks. Over many generations, the turtles may have somewhat longer necks.
A common misconception is that the traits of organisms are precisely adapted for a specific need. They are not, for a few reasons. First, natural selection occurs relative to the current environment. Adaptations that work well in one environment may not be so useful in another environment. Environments are rarely stable over evolutionary time so traits are subject to constant change.
Next, as mentioned above, natural selection can only work on what traits are present. While an extra set of arms would be handy, I am a tetrapod. My four appendages, along with the appendages of all other tetrapods, trace back to our common ancestor. The appendages of all tetrapods are modifications of that ancestral trait.
The following is multiple choice question (with options) to answer.
What occurs when organisms acquire and pass on new traits from one generation to the next generation? | [
"birth",
"evolution",
"phenomenon",
"variation"
] | B | Evolution occurs as organisms acquire and pass on new traits from one generation to the next generation. Its occurrence over large stretches of time explains the origin of new species and the great diversity of the biological world. Extant species are related to each other through common descent, and products of evolution over billions of years. Analysis of the DNA of different organisms indicates there is a similarity among very different organisms in the genetic code that help make proteins and other molecules. This genetic code is used by all known forms of life on Earth. The theory of evolution suggests that the genetic code was established very early in the history of life, and some studies suggest it was established soon after the formation of Earth. The timeline of the evolution of life, shown in Figure below , outlines the major events in the development of life. |
SciQ | SciQ-2605 | electrochemistry, water, electrolysis
To give the "method" you ask about some real world numbers,
at the very end of the Wiki page the energy efficiency for industrial water electrolysis is cited as usually between 50 and 80 %.
The paper then proposes to burn the gas in an internal combustion machine. As such a stationary process could be adjusted so that the engine is at its maximum efficiency, we may assume 1/3 or 35% efficiency here.
we then need a generator to convert the mechanical energy into electric energy. Fortunately, that step is rather efficient. Say, 95 %.
A fuel cell would be more efficient than the combustion - generator combination: ca. 40 - 60 % according to Wikipedia.
Unfortunately, also battery charging is not 100% efficient. Let's assume 80–90% (taken from Wikipedia on Li-ion batteries) For batteries that are charged with higher current (or current density) efficiency is less. Example would be lead-acid batteries as used in cars. Wiki quotes efficiencies between 50 and 80 %.
Taking these numbers together, I conclude that after going once through the cycle of the proposed "perpetuum mobile", 8 - 24 % of the energy are retained in a "useful state" while 76 - 92 % became heat. With fuel cell, we may be able to "boost" the energy efficiency to 43%.
Useful general knowledge (in addition to the law of energy conservation)
The US patent system is different from e.g. the German patent system in that here in Germany the patent application has to have commercial/industrial usability. This includes a technical argument why it works (according to the physical laws). A perpetuum mobile would be rejected on these grounds (of course the inventor could prove his case with a prototype). US patents do not have this technical check.
generators (mechanic -> electric conversion) are sources of current, while batteries (galvanic cells) are sources of voltage.
The following is multiple choice question (with options) to answer.
What process provides more than 99% of energy? | [
"nuclear fusion",
"photosynthesis",
"cellular respiration",
"glycolysis"
] | B | Plants and other autotrophs make food out of “thin air”—at least, they use carbon dioxide from the air to make food. Most food is made in the process of photosynthesis. This process provides more than 99% of the energy used by living things on Earth. Photosynthesis also supplies Earth’s atmosphere with oxygen. |
SciQ | SciQ-2606 | histology
Title: Why can't plasma proteins migrate from capillaries? Why can't plasma proteins shift from capillaries to connective tissue but WBCs can be very rich in connective tissue even though obviously the WBCs had to go through capillaries. Another example: in alveolar sacs neutrophils are there in the lumen despite the presence of epithelia of alveolar sacs, and it can only reach there via capillaries. So, how can they get into lumen despite the epithelia lining? Histology textbooks say that no plasma proteins can enter or leave capillaries, but WBCs (which are much larger than proteins) can move to connective tissue via capillaries? Cells of the endothelium are joined by tight cell junctions which are impermeable or selectively permeable. Generally, proteins can only migrate through the endothelium via active transcytosis.
Leukocytes (specifically neutrophils, lymphocytes and monocytes) express various adhesion molecules and cytokine receptors which allow them to interact with endothelial cells and facilitate their movement (diapedesis) either between (paracellular) or through (transcellular) the cells. The process of leukocytes leaving the endothelial lumen is known as extravasation.
Carman CV. 2009. Mechanisms for transcellular diapedesis: probing and pathfinding by `invadosome-like protrusions'. J Cell Sci 122:3025-3035.
(C,D) The process of diapedesis, whether during intravasation or extravasation, can occur by two distinct pathways: paracellular or transcellular. (C) Paracellular diapedesis. Leukocytes and endothelial cells coordinately disassemble endothelial cell-cell junctions and open up a gap between two or more endothelial cells (Muller, 2003). (D) Transcellular diapedesis. Leukocytes migrate directly through individual endothelial cells via a transient transcellular pore that leaves endothelial cell-cell junctions intact. Note that the two individual endothelial cells in C and D are distinguished by different shades of pink.
The following is multiple choice question (with options) to answer.
What tissue blocks entry of pathogens in mammals? | [
"dendritic",
"epithelial",
"pathological",
"esophageal"
] | B | |
SciQ | SciQ-2607 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
What in the axils of leaves and stems give rise to branches? | [
"meristems",
"chloroplasts",
"nodules",
"axillary buds"
] | D | |
SciQ | SciQ-2608 | particle-physics, dimensional-analysis, elementary-particles
Title: Minimal size of physical entities I know that per current knowledge there are layers of size of physical entities going from elementary particles to molecules (and from molecules to molecular structures such as bricks or organism cells and further into a tools, buildings, machines and organism bodies).
I understand that the notion between human scientists is that the "size" or "scale" of elementary particles (whatever these will be) is finite;
that is: Elementary particles are the smallest physical entities in this universe and there can't be anything smaller than them in this universe.
Is there a theory according to which infinity for how small physical entities can be, is real?
I am not talking about a theory theorizing even more and smaller elementary particles than accepted, but rather a theory that its theoreticians are "irreverent" to suggest that there is no such thing as "elementary" particle by the sense that one could always go down in the "scale" of size.
One could be further irreverent to derive from such theory that because time passes faster in micro than in macro, entire universes could exist and might appear to an observing organism as a "particle" with a lifespan of way less than a millisecond.
Also, of course the opposite question (Can there be maximal size of physical entities?) is dependent on if the cosmos is finite or infinite, but the current question doesn't seem to me such.
Is there a theory according to which infinity for how small physical entities can be, is real?
You have to define what the definition of "small" is . If you means size, the standard model of particle physics has elementary particles as point particles, no size at all, so they fulfill already the "smallnes".
If you mean if their invariant mass can be very small, already the photon the gluon and maybe the graviton have zero mass in the mainstream models.
am not talking about a theory theorizing even more elementary particles than accepted, but rather a theory that its theoreticians are "irreverent" to suggest that there is no such thing as "elementary" particle by the sense that one could always go down in the "scale" of size.
The following is multiple choice question (with options) to answer.
The existence of what tiny, fundamental particles of matter was first proposed in the 1960s? | [
"neutrons",
"atoms",
"quarks",
"molecules"
] | C | The existence of quarks was first proposed in the 1960s. Since then, scientists have done experiments to show that quarks really do exist. In fact, they have identified six different types of quarks. However, much remains to be learned about these tiny, fundamental particles of matter. They are very difficult and expensive to study. If you want to learn more about them, including how they are studied, the URL below is a good place to start. |
SciQ | SciQ-2609 | zoology, psychology
Title: Fear in elephants It has been noted that elephants trained for war, as was done occasionally in earlier times, have still shown a tendency to panic in battle much more often when compared to a war horse trained for the same purpose. However, is this due to an innate quality of elephant behavior, or a result of poorer training methods due to humans simply having less experience training elephants than horses? Are elephants naturally more fearful creatures than horses or other beasts of war? I doubt if a comparison between these two animals in war situation is in order. These two animals serve different roles.
Here is a reference to an article in Wikipedia on War Elephants. Elephants have been used in war for thousands of years pretty effectively till the enemies discover their weakness and use it to their advantage. Making the elephant panic is one of the ways to counter them. Here is a list of methods from the above article:
Elephants had a tendency to panic themselves: after sustaining painful wounds or when their driver was killed they would run amok
One famous historical method for disrupting elephant units was the war pig......
At the Megara siege during the Diadochi wars, for example, the Megarians reportedly poured oil on a herd of pigs, set them alight, and drove them towards the enemy's massed war elephants. The elephants bolted in terror from the flaming squealing pigs.
It is for sure that many horses also panic in war situations. However a panicked elephant can cause more havoc than a horse. It appears that to prevent a panicked elephant from running amuck back into the ranks
The driver, called a mahout, was responsible for controlling the animal. In many armies, the mahout also carried a chisel-blade and a hammer to cut through the spinal cord and kill the animal if the elephant went berserk.
In recent times elephants in temple festivals in india do occasionaly panic and run amuck when the high explosive fire works are set of. However most of the elephants seem to tolerate it.
The following is multiple choice question (with options) to answer.
Animals that defend their area are generally known as what kinds of animals? | [
"neutral",
"mutants",
"carnivores",
"territorial"
] | D | Some species of animals are territorial . This means that they defend their area. The area they defend usually contains their nest and enough food for themselves and their offspring. A species is more likely to be territorial if there is not very much food in their area. Animals generally do not defend their territory by fighting. Instead, they are more likely to use display behavior. The behavior tells other animals to stay away. It gets the message across without the need for fighting. Display behavior is generally safer and uses less energy than fighting. Male gorillas use display behavior to defend their territory. They pound on their chests and thump the ground with their hands to warn other male gorillas to keep away from their area. The robin displays his red breast to warn other robins to stay away ( Figure below ). |
SciQ | SciQ-2610 | thermodynamics, combustion
Title: Recovering mechanical energy from natural gas water boiler Is there any heat energy lost to the mechanical force of pushing a piston in a combustion engine?
In other words, would a natural gas burning as a flame produce more heat than the same amount of natural gas that was burned when driving a combustion engine?
The context of this question is around fuel efficiency of natural gas water boilers.
My current understanding is that a naked natural gas flame is burning inside the unit, and heats water that is contained within a series of pipes, which in turn is cooled in a heat exchanger, and that same heat exchanger heats the incoming cool water.
I'm wondering, would if it make any sense at all to burn that natural gas inside a combustion engine and use the heat of the combustion engine used to heat the water to the same extent as a naked flame.
More generally my goal is to solve the question, can we heat water the same extent by burning the same amount of natural gas and get free mechanical energy?
Thanks Check out combined heat and power systems... generates electricity and makes use of the waste heat to heat water - but is only really efficient when there is sufficient hot water demand ie heating load.
The following is multiple choice question (with options) to answer.
A boiler converts the chemical energy stored in fuel into what type of energy? | [
"atmospheric energy",
"Thermometric Energy",
"thermal energy",
"ultraviolet energy"
] | C | Water is heated in a boiler that burns a fuel such as natural gas or heating oil. The boiler converts the chemical energy stored in the fuel to thermal energy. |
SciQ | SciQ-2611 | water, crystals, freezing
Title: About observing crystal of ice While reading a paper about ice crystal growth, they use vapor and seed to create crystal. I thought that I could observe crystal just by freezing liquid water. Is there differences between just freezing liquid water and using vapor and seed? The seed is important. It is a small crystal that gets larger. It can be difficult for crystal growth to start. A tiny crystal about a nanometer across has a very large surface compared to its interior. Surface atoms have different bonds than interior atoms. Sometimes it takes more energy to be on the surface. This makes a tiny crystal energetically unfavorable.
Because of this, crystals tend to start growing on a surface rather than the center of a liquid or gas. This can happen multiple places. Then you get multiple crystals in different orientations.
Under controlled conditions, a seed ensures that only one crystal forms.
A liquid is either present or not. Gas can be present in high or low concentration. Concentration has an effect on how the crystal grows.
Snowflakes have many different forms. Which form is favored is determined by concentration and temperature. See http://www.snowcrystals.com/science/science.html
The following is multiple choice question (with options) to answer.
What are the ice crystals that form on the ground called? | [
"snow",
"granules",
"frost",
"sleet"
] | C | Deposition as a change of state often occurs in nature. For example, when warm moist air comes into contact with very cold surfaces—such as the ground or objects on the ground—ice crystals are deposited on them. These ice crystals are commonly called frost. Look at the dead leaf and blades of grass in the Figure below . They are covered with frost. If you look closely, you can see the individual crystals of ice. You can watch a demonstration of frost forming on the side of a very cold can at the URL below. (Click on the mulitmedia choice “Ice on a Can. ”). The ice in the can has been cooled to a very low temperature by adding salt to it. If you want to do the demonstration yourself, follow the procedure at the URL. http://www. middleschoolchemistry. com/lessonplans/chapter2/lesson4. |
SciQ | SciQ-2612 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
What is the largest organelle in a eukaryotic cell? | [
"mitochondria",
"nucleus",
"vacuole",
"ribosome"
] | B | The nucleus is the largest organelle in a eukaryotic cell. It contains most of the cell’s DNA. DNA, in turn, contains the genetic code. This code “tells” the cell which proteins to make and when to make them. You can see a diagram of a cell nucleus in Figure below . Besides DNA, the nucleus contains a structure called a nucleolus. Its function is to form ribosomes. The membrane enclosing the nucleus is called the nuclear envelope. The envelope has tiny holes, or pores, in it. The pores allow substances to move into and out of the nucleus. |
SciQ | SciQ-2613 | kinetics, theoretical-chemistry
Let us consider a thermodynamic system with first law $$\text{d}U = f_1\,\text{d}X_1 + f_2\,\text{d}X_2.$$ It is coupled to a reservoir, itself with first law $$\text{d}U' = f_1'\,\text{d}X_1' + f_2'\,\text{d}X_2' = -f_1'\,\text{d}X_1 - f_2'\,\text{d}X_2,$$ noting that $\text{d}X_i' = -\text{d}X_i$, because $X_i+X_i'$ is assumed fixed. A perturbation $\text{d}X_1^\text{pert}$ drives fluctuations $$\text{d}f_1^\text{fluc} = \frac{\partial f_1}{\partial X_1}\text{d}X_1^\text{pert} \quad \text{and} \quad \text{d}f_2^\text{fluc} = \frac{\partial f_2}{\partial X_1}\text{d}X_1^\text{pert}.$$ These fluctuations in intensive quantities themselves lead to responses $\text{d}X_1^\text{resp}$ and $\text{d}X_2^\text{resp}$. The signs of these responses can be determined by minimizing the total energy of the system and reservoir given the initial perturbation, $$\text{d}(U+U') = (f_1-f_1')\,\text{d}X_1^\text{resp} + (f_2-f_2')\,\text{d}X_2^\text{resp} = \text{d}f_1^\text{fluc}\text{d}X_1^\text{resp} +
The following is multiple choice question (with options) to answer.
What does the kinetic-molecular theory describe the behavior of? | [
"a compound",
"an ideal gas",
"a solid",
"a liquid"
] | B | The kinetic-molecular theory describes the behavior of an ideal gas. |
SciQ | SciQ-2614 | sociality, olfaction
Sexual Signaling:
In some species, apocrine gland secretions may play a role in sexual attraction and mate selection. The distinct scents emitted by individuals can serve as cues for potential mates to assess each other's fitness and genetic compatibility.
Developmental Timing:
Apocrine glands are not fully functional until puberty in humans. Their activation and development are influenced by hormonal changes during adolescence.
Associated with Hair Follicles:
Apocrine glands are associated with hair follicles, and their ducts open into the hair follicle canal. This is in contrast to eccrine glands, which release sweat directly onto the skin's surface.
Here's a ref from nature stating that human primates may use sweat pheromones to communicate:
https://www.nature.com/articles/npre.2008.2561.1.pdf
Primates, especially those living in social groups, rely heavily on communication to maintain social bonds, establish hierarchies, and coordinate group activities. Scent plays a crucial role in primate communication, and sweat scent could have evolved as a means for individuals to convey information about their identity, reproductive status, and emotional state to other members of their group.
mate selection in primates can be influenced by olfactory cues. Scent signals emitted through sweat may allow potential mates to assess each other's genetic compatibility, overall health, and reproductive fitness.
the scent-marking behavior using secretions from sweat glands may serve as a way to establish territorial boundaries and prevent conflicts with neighboring groups.
The odor produced by sweat may play a role in avoiding predators. For example, certain primate species may produce alarm pheromones through their sweat, signaling danger to other group members.
Sweat scent in primates could be a remnant of their ancestral heritage, where scent communication was crucial for survival and reproduction.
incidentally, horses, dogs, deer, they also have strong pheromones.
The following is multiple choice question (with options) to answer.
What kind of hormones are released into the environment for communication between animals of the same species? | [
"reactions",
"peptides",
"pheromones",
"hormones"
] | C | |
SciQ | SciQ-2615 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
What organ contributes about 60% of the volume of semen ? | [
"cilia",
"seminal vesicles",
"complete vesicles",
"long vesicles"
] | B | |
SciQ | SciQ-2616 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Eukaryotic cells contain what type of structures that possess special functions? | [
"chloroplasts",
"fibers",
"cell membranes",
"organelles"
] | D | Eukaryotic cells contain a nucleus and other organelles. They include the mitochondrion, endoplasmic reticulum, Golgi apparatus, vesicles, vacuoles, lysosomes, and—in animal cells—centrioles. Each type of organelle has a special function. |
SciQ | SciQ-2617 | ocean, oceanography, sea-level, tides
However, I'm really curious as which are the most important amongst them? Or is it even possible to guess the tide height if I know the Lunar phase and I have a good globe with sea depth? I don't know about the size of land masses, but their distribution and the shape of ocean basins definitely play a big role.
When considering the ideal case of an all-ocean globe, i.e. one with no land masses (equilibrium tidal theory), the combined effect of sun and moon give a theoretical tidal range of less than 1 m(1). As tidal ranges can be much larger than this, there are other effects that has a greater influence.
The Bay of Fundy for example, is one of the places with the largest difference between low tide and high tide, at about 16 m. The large difference in this location has to do with the shape of the bay. The bay has a natural frequency for waves that is about the same as the frequency of the tide itself, giving an amplification of the tidal amplitude. In addition there is a funnelling effect in the inner part of the bay, giving an additional contribution.(2)
Another example of large tidal differences is the English channel, particularly the French side. In this case the tides are large at least partly because the tide moves as a coastal trapped Kelvin wave. These are waves that propagate along land, with the land to the right when looking in the direction of propagation (on the Northern hemisphere, land to the right on SH). The amplitude of the wave is highest near the coast, decaying exponentially away from the coast. As the tide in the English channel moves northward, the largest tidal range is on the French side.
With regard to guessing the tidal range, this is not entirely straight forward.
First, when discussing tides, we generally split the tidal potential into a series of oscillations having different frequencies, mainly either diurnal (period of ~24 h) or semi-diurnal (period of ~12 h).
These given frequencies are obtained through trigonometric considerations, and depend on the latitude of the point, the declination of the moon or sun relative to the equator, and the hour angle.
(The hour angle is basically the longitudinal difference between the sub-lunar point and the point we consider.)
Each of these components can vary in time and space.
The following is multiple choice question (with options) to answer.
What is the common name for the midpoint between high and low tide? | [
"middle level",
"clouds level",
"sea level",
"floods level"
] | C | Sea level is the midpoint between high and low tide. It can vary around Earth. |
SciQ | SciQ-2618 | thermodynamics
Title: Does a gas condenses above its dew point? We all know that at temperatures much below the boiling point, evaporation occurs and liquid/vapor equilibrium exists.
So if we have steam at temperature greater than dew point, does it undergoes condensation at that temperature? Let's, for simplicity, consider a closed container with a liquid. In such closed system, evaporation and condensation happen simultaneously.
The rate of evaporation increases with temperature. The rate of condensation, which happens when vapor molecules hit the surface of the liquid, depends on the vapor pressure.
At equilibrium, the rates of evaporation and condensation are the same and the temperature is a dew point, by definition.
If the temperature is raised above that point, the rate of evaporation will exceed the rate of condensation, but, the condensation will still occur. This will continue until the new equilibrium is achieved, with the new temperature becoming a new dew point.
So, for a closed system, condensation does happen at temperatures above the dew point.
In an open environment, when the vapor does not come in contact with liquid, the condensation, generally, should not occur above the dew point.
The following is multiple choice question (with options) to answer.
What is formed when humid air near the ground cools below its dew point? | [
"weather",
"fog",
"steam",
"smoke"
] | B | Fog ( Figure below ) is a cloud on the ground. Fog forms when humid air near the ground cools below its dew point. Each type of fog forms in a different way. |
SciQ | SciQ-2619 | organic-chemistry, bond, covalent-compounds
Title: The difference between peptide bonds and the bonds between polypeptides? I was doing some tests for the multiple-choice final we've got ahead. And it was on me to count the peptide bonds in an Insulin hormone with 51 aminoacids arranged in two polypeptides with 30 and 21 aminoacids. (these are not true in reality) the number of bonds were 49, not 50, and that means the bond between two polypeptides doesn't count as a peptide bond. Additionally, I know that polypeptide bonds make the proteins' molecular structure, as it is now. (just look at that shape.) PEPTIDE COVALENT BONDS CAN NEVER cause that kind of 3d orientation in space. So there must be some fundamental difference between those bonds. What is it?
My research couldn't find any results as simple things have jammed the internet. Aside from covalent bonds (amide and disulfide), the sturcture of a protein is determined by hydrogen bonds, salt bridges, and less specific interactions such as hydrophobic and hydrophilic effects. Hydrophobic portions of the protein chain tend toward the interior of the folded protein and hydrophilic regions to the exterior, in aqueous solution.
The following is multiple choice question (with options) to answer.
When are peptide bonds between amino acids formed? | [
"process of migration",
"process of production",
"process of transcription",
"process of translation"
] | D | Amino acids can bond together through peptide bonds to form short chains called peptides or longer chains called polypeptides ( Figure below ). A peptide bond is a covalent bond formed from a condensation reaction between two molecules, causing the release of a molecule of water. This bond usually forms between two amino acids, hence forming a peptide or polypeptide. Peptide bonds between amino acids are formed during the process of translation. |
SciQ | SciQ-2620 | botany, plant-physiology, reproduction, plant-anatomy, life-history
In dimorphic cleistogamy CL and CH flower differ in the time or place
of production, with CL flowers produced in conditions (underground,
low light levels, early in the season) that are potentially
unfavorable for outcrossing.
In induced cleistogamy potentially CH flowers that experience conditions such as drought or low temperatures fail to open and self-pollinate, becoming, in effect, CL flowers.
You should check out the Culley and Klooster (available online if you make a jstor login) – they discuss complete cleistogamy which addresses your last question. They report several completely CL species in their Table 1, and give references.
More generally, many different plant groups maintain balances of self-pollination and outcrossing (i.e. "real sex"), through an even more diverse set of mechanisms.
Even more generally, many plants and some animals maintain balances of sexual reproduction and clonal reproduction, through an even more diverse set of mechanisms. For instance, vegetative reproduction (e.g., strawberry runners) is very common in many plant groups; facultative and obligate parthenogenesis in animals also occurs.
Culley, Theresa M. and Matthew R. Klooster (2007). The Cleistogamous Breeding System: A Review of Its Frequency, Evolution, and Ecology in Angiosperms. Botanical Review. Vol. 73, No. 1, pp. 1-30
The following is multiple choice question (with options) to answer.
Within the petals are two whorls of fertile floral organs that produce what? | [
"spores",
"leaves",
"fibers",
"toxins"
] | A | |
SciQ | SciQ-2621 | thermodynamics, temperature, cooling
Negative temperatures are hotter (have more energy) than positive temperatures; and
As you put more energy into a system with negative temperature, the temperature gets closer to zero.
So, in order of increasing energy, the temperature goes $$T = +0 \rightarrow T = \text{positive} \rightarrow T=+\infty \rightarrow T=-\infty \rightarrow T=\text{negative} \rightarrow T=-0.$$
Now, back to Newton's law of cooling. As you've written it, $${dT\over dt} = -k(T - T_a)$$ has three related assumptions buried in it which are relevant to this discussion:
Temperature increases as energy increases. (The equation is written in terms of temperature instead of energy)
Higher temperatures correspond to higher energies. (The minus sign on the right hand side)
The relationship between temperature and energy is linear. (The constant $k$ on the right hand side. Strictly speaking, $k$ accounts for the thermal coupling between the two systems, but making it temperature dependent could also deal with a nonlinear relationship between $T$ and $E$.)
Except for the pathological point at $n=N/2$, the first of these is satisfied regardless of the sign of the temperature, but the second fails if the two temperatures have different signs. The third assumption breaks down if you get close enough to the transition between positive and negative temperatures.
So, in the situation you've outlined ($T=-3, T_a = 3$) Newton's law of cooling will not work:
$(T - T_a)$ is negative,
so the right hand side is positive, which would mean that
$dT/dt$ is positive, so
the temperature would become less negative (move toward negative zero) over time, which would mean
energy would flow into the system from its environment.
In terms of entropy, the system has a negative temperature, so increasing its energy decreases its entropy, and
the environment has a positive temperature, so decreasing its energy decreases its entropy, so
this process would decrease the overall entropy of the universe, and
this is a violation of the 2nd law of thermodynamics.
The following is multiple choice question (with options) to answer.
Increasing or decreasing the temperature of a system in what state acts as a stress to the system? | [
"liquid",
"gaseous",
"equilibrium",
"nitrogen"
] | C | Increasing or decreasing the temperature of a system at equilibrium is also a stress to the system. The equation for the Haber-Bosch process is written again below, this time as a thermochemical equation. |
SciQ | SciQ-2622 | nomenclature, research-process
I suspect the reason that most materials don't discuss how this process really works is because it is really, really complicated and often pretty dry. You'll see plenty of examples of new names being coined in journals like Taxon. But doing taxonomy is often conceived as not very glamorous, so doesn't receive that much attention, even though it underpins most comparative fields like ecology and evolution.
As a final note, the reasons that a species will be included in a given genus, or split into its own genus, or several genera will be lumped together into one large genus, are more murky, and related to phylogeny, morphology, final size, etc. These decisions are often also left up to the discretion of the author, unless of course they conflict with the code.
The following is multiple choice question (with options) to answer.
The scientific name of an organism consists of its genus and what else? | [
"specimens",
"mammals",
"species",
"samples"
] | C | The scientific name of an organism consists of its genus and species. |
SciQ | SciQ-2623 | evolution
bacteria
cyanobacteria
archaea
protists
fungi
algae
plants
nematodes
arthropods
vertebrates
Bacterial and archaean colonisation
The first evidence of life on land seems to originate from 2.6 (Watanabe et al., 2000) to 3.1 (Battistuzzi et al., 2004) billion years ago. Since molecular evidence points to bacteria and archaea diverging between 3.2-3.8 billion years ago (Feng et al.,1997 - a classic paper), and since both bacteria and archaea are found on land (e.g. Taketani & Tsai, 2010), they must have colonised land independently. I would suggest there would have been many different bacterial colonisations, too. One at least is certain - cyanobacteria must have colonised independently from some other forms, since they evolved after the first bacterial colonisation (Tomitani et al., 2006), and are now found on land, e.g. in lichens.
Protistan, fungal, algal, plant and animal colonisation
Protists are a polyphyletic group of simple eukaryotes, and since fungal divergence from them (Wang et al., 1999 - another classic) predates fungal emergence from the ocean (Taylor & Osborn, 1996), they must have emerged separately. Then, since plants and fungi diverged whilst fungi were still in the ocean (Wang et al., 1999), plants must have colonised separately. Actually, it has been explicitly discovered in various ways (e.g. molecular clock methods, Heckman et al., 2001) that plants must have left the ocean separately to fungi, but probably relied upon them to be able to do it (Brundrett, 2002 - see note at bottom about this paper). Next, simple animals... Arthropods colonised the land independently (Pisani et al, 2004), and since nematodes diverged before arthropods (Wang et al., 1999), they too must have independently found land. Then, lumbering along at the end, came the tetrapods (Long & Gordon, 2004).
Note about the Brundrett paper: it has OVER 300 REFERENCES! That guy must have been hoping for some sort of prize.
References
The following is multiple choice question (with options) to answer.
What type of organism was the only able to live in the anoxic atmosphere of the first 2 billion years? | [
"anaerobic",
"aerobic",
"protists",
"mammals"
] | A | CHAPTER SUMMARY 22.1 Prokaryotic Diversity Prokaryotes existed for billions of years before plants and animals appeared. Hot springs and hydrothermal vents may have been the environments in which life began. Microbial mats are thought to represent the earliest forms of life on Earth, and there is fossil evidence of their presence about 3.5 billion years ago. A microbial mat is a multi-layered sheet of prokaryotes that grows at interfaces between different types of material, mostly on moist surfaces. During the first 2 billion years, the atmosphere was anoxic and only anaerobic organisms were able to live. Cyanobacteria evolved from early. |
SciQ | SciQ-2624 | population-genetics, conservation-biology
Where cloning can come in is it can be used to increase the gene pool, sometimes quite substantially. Consider the meta-population of a species, this could be allowed to include all of the wild sub-populations and all captive or managed (semi-captive) populations. For example, there are ~3900 wild tigers in the world, and ~5000 in captivity. Among all of those, only a subset contribute offspring to the next generation of wild animals, reducing the effective population size, and increase rates of inbreeding and genetic drift. For example, often very few males fertilise the females of a population with strong effects on the effective population size. What cloning could be used for (to various levels, depending on the specifics of the method) is to allow other individuals to contribute. For example, by cloning the members of a wild population that were unable to secure mates during a reproductive season (there is often high variance in mating success which reduces effective population), conservation managers can artificially re-inflate the effective population size to more closely resemble the census population size. In other cases, conservation managers may chose to clone particularly viable/fertile individuals that are approaching old age or nearing death, and are therefore at risk of being lost from the population. Conservation programs could use cloning of (semi-)captive individuals and introducing clones from (semi-)captive populations in to wild populations allowing genetic variation to be drawn from the gene pool of (semi-)captives in to the wild populations. Increasing the variance in the gene pool will increase the adaptive potential of the wild population. Another option is to clone wild animals in threatened areas (e.g. where populations are in decline as a result of poaching) and to put the clones in to safer areas such as national parks, or even zoos, to preserve genetic variation while conservation managers try to bring the other issues under control. Effectively this would act a bit like a seed bank.
The following is multiple choice question (with options) to answer.
Scientists utilize what natural process to teach cranes born in captivity to migrate along safe routes? | [
"neuroimaging",
"expediting",
"imprinting",
"natural selection"
] | C | |
SciQ | SciQ-2625 | mass, density, volume
Title: Confused about volume, density and mass, help! I got into an argument with my friend, which cast confusion on my understanding of density and its relationship to volume. I'm hoping to get some clarity. The argument involved describing density in terms of volume. Let's say you define a sphere in empty space. You choose a point, apply the formula for a sphere, and now you have a sphere. Not a sphere OF anything other than space, just a spacial, theoretical sphere. No particles, massless or otherwise (this is a thought experiment). What is the density of that sphere? Is it zero, or is it undefined? I know density can be defined as p = m/v. But in a theoretical sphere, which HAS volume, should we call mass zero, because there is none? Or is it undefined because a theoretical sphere really isn't related to mass at all? If it IS undefined, does that mean it makes no sense to relate density to volume because density is only a property of mass?
The answer, to me, seems to be that in fact it makes no sense to talk about the density of a massless object. Sorry if I answered my own question, but I would still like clarity. If someone could help guide me through the assumptions I'm making about reality and math and how they relate, I'd really appreciate it. Theoretically speaking, in order for something (usually particles) to be massless, it has to be travelling in the speed of light. In quantum theory, uncertainty principle states that the position and momentum of such particle cannot be accurately determined, therefore it is not possible to measure the volume of the particle. So it is generally assumed that the volume is too small and/or insignificant.
Regarding your question, I think that the simple answer would be; a massless object would have no volume nor density, or immeasurable. Take your pick.
The following is multiple choice question (with options) to answer.
What are mass, volume, and length an example of? | [
"extensive compounds",
"extensive properties",
"fantastic properties",
"dynamic properties"
] | B | Extensive properties vary according to the amount of matter present. Examples of extensive properties include mass, volume, and length. |
SciQ | SciQ-2626 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
Chelicerata are know for their first pair of appendages, also know as what? | [
"ambers",
"chelicides",
"maxillae",
"chelicerae"
] | D | Subphylum Chelicerata includes animals such as spiders, scorpions, horseshoe crabs, and sea spiders. This subphylum is [4] predominantly terrestrial, although some marine species also exist. An estimated 103,000 described species are included in subphylum Chelicerata. The body of chelicerates may be divided into two parts and a distinct “head” is not always discernible. The phylum derives its name from the first pair of appendages: the chelicerae (Figure 15.23a), which are specialized mouthparts. The chelicerae are mostly used for feeding, but in spiders, they are typically modified to inject venom into their prey (Figure 15.23b). As in other members of Arthropoda, chelicerates also utilize an open circulatory system, with a tube-like heart that pumps blood into the large hemocoel that bathes the internal organs. Aquatic chelicerates utilize gill respiration, whereas terrestrial species use either tracheae or book lungs for gaseous exchange. |
SciQ | SciQ-2627 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
What kind of reproduction generates new individuals without fusion of an egg and sperm? | [
"gametes",
"asexual",
"sexual",
"propagation"
] | B | |
SciQ | SciQ-2628 | states-of-matter
Title: Is there an inherent difference between solids, liquids, and gases? I know that at very large scales, solids behave like liquids, which is why planets are round, rather than knobbly. I also understand that you can pour some gases, and, if I have this right, that the air around the Earth is like a like an additional layer of liquid, but very much lighter. You can still be crushed by enough air.
This makes me wonder, are the differences between solids, liquids, and gases a human distinction that is merely useful under certain common circumstances, or are they actually inherently different concepts? In the case of liquids and gases, at least, there's no fundamental difference. To see this, take a look at Wikipedia's phase diagram for water.
Ignore the dotted lines for the moment, and note that the line between vapour (steam) and liquid stops at a certain point, called the critical point. What this means is that if you go through the following sequence of steps, you can turn liquid water into steam without ever noticing a sudden change:
increase the pressure above the critical point (about 218 atmospheres), keeping the temperature constant at a relatively high value, but less than $100^\circ C$
keeping the pressure constant at $>218$ atm, increase the temperature to above about $374^\circ C$
reduce the pressure back down to 1 atmosphere or below
reduce the temperature to somewhere closer to $100^\circ C$.
The following is multiple choice question (with options) to answer.
The properties of liquids are intermediate between those of gases and solids but are more similar to? | [
"oils",
"solids",
"gases",
"plasma"
] | B | The properties of liquids are intermediate between those of gases and solids but are more similar to solids. In contrast to intramolecular forces, such as the covalent bonds that hold atoms together in molecules and polyatomic ions, intermolecular forces hold molecules together in a liquid or solid. Intermolecular forces are generally much weaker than covalent bonds. For example, it requires 927 kJ to overcome the intramolecular forces and break both O–H bonds in 1 mol of water, but it takes only about 41 kJ to overcome the intermolecular attractions and convert 1 mol of liquid water to water vapor at 100°C. (Despite this seemingly low value, the intermolecular forces in liquid water are among the strongest such forces known!) Given the large difference in the strengths of intra- and intermolecular forces, changes between the solid, liquid, and gaseous states almost invariably occur for molecular substances without breaking covalent bonds. |
SciQ | SciQ-2629 | biochemistry, gas-laws
Title: What is the state of aggregation (gas, liquid) of oxygen in blood? Atmospheric oxygen is in O2 and a gas. Then we inhale the air, our efficient lungs do the magic to filter out the oxygen and push them into the blood stream.
When we say hemo and globin transport the oxygen using the iron ions. In what state oxygen is transported in the blood? as a gas or a liquid or an ion? It is hard for me to conceive of the idea that oxygen would be in gaseous form in the blood. "GAS in blood?" e.g. Arterial Blood Gas Test
Also, how does the lungs convert the gas into something that is compatible to be in blood?
References:
Amount of Oxygen in the Blood Regarding the state of oxygen in blood: It is in solution in the blood plasma (which mostly consists of water), in the form of single molecules. Think of water which you leave exposed to air: carbon dioxide will be captured and dissolved (along with the other gases in air), but these molecules are not gaseous or liquid, but rather "in solution", which is different from the "classical" states.
Back to oxygen: As your reference already states, most of the oxygen in solution will bind to hemoglobin. The actual state of oxygen in that complex has been debated, but it is believed to be reduced by the hemoglobin iron to the superoxide anion, coordinated to Fe$^{3+}$. See Wikipedia on this.
Also, the lungs do not "convert" the atmospheric oxygen to anything, they rather allow, due to their very large surface area, the quick exchange of oxygen/carbon dioxide in solution and in the air.
The following is multiple choice question (with options) to answer.
What does blood pickup from the lungs to be carried throughout the rest of the body? | [
"carbon",
"oxygen",
"white blood cells",
"platelets"
] | B | The blood picks up oxygen in the lungs and carries it to cells throughout the body. |
SciQ | SciQ-2630 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
The earliest types of what lacked flowers, leaves, roots and stems? | [
"clouds",
"plants",
"animals",
"houses"
] | B | Most modern plants, like the skunk cabbage, produce flowers. However, flowers evolved relatively late in the history of plants. The earliest plants not only lacked flowers. They also lacked leaves, roots, and stems. They probably resembled the alga in Figure below . |
SciQ | SciQ-2631 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
The nervous system is made up of these? | [
"fibers",
"blood cells",
"muscles",
"neurons"
] | D | Watch this video (http://openstaxcollege. org/l/vertebrate_evol) of biologist Mark Kirschner discussing the “flipping” phenomenon of vertebrate evolution. The nervous system is made up of neurons, specialized cells that can receive and transmit chemical or electrical signals, and glia, cells that provide support functions for the neurons by playing an information processing role that is complementary to neurons. A neuron can be compared to an electrical wire—it transmits a signal from one place to another. Glia can be compared to the workers at the electric company who make sure wires go to the right places, maintain the wires, and take down wires that are broken. Although glia have been compared to workers, recent evidence suggests that also usurp some of the signaling functions of neurons. There is great diversity in the types of neurons and glia that are present in different parts of the nervous system. There are four major types of neurons, and they share several important cellular components. |
SciQ | SciQ-2632 | human-biology, endocrinology, circadian-rhythms
Title: Which human body hormonal systems exhibit 24 hour diurnal cyclical activity? I'm researching the possible connection between the dream content and the activity of various organ or hormonal systems within the human body. I'm looking for information on biological cycles within the human body that occur on a 24 hour cycle and may influence the sleep cycle, dream content or the overall state of awareness.
So far I was able to find:
Adrenaline, cortisol, testesterone - circadian endogenous cycle.
leptin, glucose, insuline - peak with awakening, decline with bedtime
What else within the human body is functioning on a predictable 24 hour cycle?
Thank you for any information! The real answer is probably more than you want, but its easy to do better than the list above.
I took a look through GEO for human circadian expression data and surprisingly I only found 2.
Looking at GSE2703 - the rhesus circadian expression experiment, they have shown 355 genes that are rhythmically expressed. This is not a great experiment because they only looked over a single 24 hour period. Its only the adrenal gland. Nonetheless they found 355 genes which seemed to be circadian. the table is supplemental data to the article, listed below.
I see a fibroblast growth factor receptor, some hydrocarbon nuclear receptor components, sterol regulatory factors, bone morphogenic protein 2, glutamate receptor, thrombonspondin receptor, ryanodine receptor 3 (what is that?) , lysophosphatidic acid G-protein-coupled receptor 2, purinergic receptor P2Y, G-protein coupled. You might find more if you know what you are looking for.
The other circadian study was on human muscle, which will no doubt give different answers. I imagine circadian behavior is highly tissue dependent.
Reference: Lemos DR, Downs JL, Urbanski HF. Twenty-four-hour rhythmic gene expression in the rhesus macaque adrenal gland. Mol Endocrinol 2006 May;20(5):1164-76
The following is multiple choice question (with options) to answer.
What are regular changes in biology or behavior that occur in a 24 hour cycle? | [
"cognitive rhythm",
"auditory rhythm",
"circadian rhythm",
"life cycle"
] | C | Circadian rhythms are regular changes in biology or behavior that occur in a 24-hour cycle. In humans, for example, blood pressure and body temperature change in a regular way throughout each 24-hour day. |
SciQ | SciQ-2633 | evolution, adaptation
Title: What of Gould's contributions to evolutionary biology are still accepted in the mainstream? I have been reading Daniel Dennett's Darwin's Dangerous Idea, in which he picks apart many of Stephen Jay Gould's criticisms of neo-Darwinism, particularly in the chapter 'Bully for Brontosaurus'. Turns out Gould wrote a lengthy refutation back, and they ended up throwing slurs at each other for a few years afterwards.
I am interested to know what the current state of mainstream opinion is on Gould's interpretations, particularly on panadaptationism and gradualism. Has the field yet come to any firm conclusions on who was right after all? His main contribution was making biologist consider that population size affects how fast selection changes a population, but he tended to imply this was some form of categorical difference and not a spectrum. But this was greatly overblown my media into some sort of insistence that they could not be the same. large population slow change and small population fast change are both points on the same spectrum. Nobody was right becasue both sides were not really saying the other could not occur they just emphasised their own area. Gould main problem was the idea of stasis in punctuated equilibrium that large populations somehow did not keep evolving this was a point he contested without ever really being able to provide evidence for. His own evidence often fit both interpretations. Since then it has been pretty thoroughly refuted by genetic studies, better resolution*, and modeling of stabilizing selection, all populations change, large ones just change slower, often with less direction. Gould himself later accepted this, but insisted on keeping the terms punctuated equilibrium and more oddly "stasis" for these periods of reduced change, this led to more misunderstanding especially with the public and media. Many scientist felt it was a sign of being unwilling to truly accept the evidence.
The following is multiple choice question (with options) to answer.
Did darwin believe in punctuated equilibrium or gradualism? | [
"neither",
"gradualism",
"it depended",
"punctuated equilibrium"
] | B | Darwin thought that evolution occurs gradually. This model of evolution is called gradualism. The fossil record better supports the model of punctuated equilibrium. In this model, long periods of little change are interrupted by bursts of rapid change. |
SciQ | SciQ-2634 | ph, reaction-control, chemical-engineering
Depending on where you are, the conditions must be different.
Note also that the inflection point becomes less obvious when weak acids or bases are involved.
Finally, you might need to integrate also a temperature compensation since, depending on the $\Delta\epsilon$ you have set, the pH change with temperature will be to high.
In short, a PID might work in some specific system, but for a general purpose system you will probably need some more sophisticated control like a PLC.
The following is multiple choice question (with options) to answer.
What is the term for a solution that resists dramatic changes in ph? | [
"buffer",
"inert",
"neutral",
"stable"
] | A | As indicated in Section 12.4 "Strong and Weak Acids and Bases and Their Salts", weak acids are relatively common, even in the foods we eat. But we occasionally encounter a strong acid or base, such as stomach acid, which has a strongly acidic pH of 1.7. By definition, strong acids and bases can produce a relatively large amount of H+ or OH−ions and consequently have marked chemical activities. In addition, very small amounts of strong acids and bases can change the pH of a solution very quickly. If 1 mL of stomach acid [approximated as 0.1 M HCl(aq)] were added to the bloodstream and no correcting mechanism were present, the pH of the blood would decrease from about 7.4 to about 4.7—a pH that is not conducive to continued living. Fortunately, the body has a mechanism for minimizing such dramatic pH changes. The mechanism involves a buffer, a solution that resists dramatic changes in pH. Buffers do so by being composed of certain pairs of solutes: either a weak acid plus a salt derived from that weak acid or a weak base plus a salt of that weak base. For example, a buffer can be composed of dissolved HC2H3O2 (a weak acid) and NaC2H3O2 (the salt derived from that weak acid). Another example of a buffer is a solution containing NH3 (a weak base) and NH4Cl (a salt derived from that weak base). Let us use an HC2H3O2/NaC2H3O2 buffer to demonstrate how buffers work. If a strong base—a source of OH−(aq) ions—is added to the buffer solution, those OH− ions will react with the HC2H3O2 in an acid-base reaction:. |
SciQ | SciQ-2635 | material-science
Title: Wood: A Naturally Occurring Composite Material? In materials science texts, I see wood used an example of a naturally occurring composite material. One of the main components of wood is cellulose, which is a polymer. But what other component makes it a composite?
Thanks for any clarification. the two components of wood-as-a-composite are cellulose fibers and lignin, the resin in which the cellulose fibers are embedded. Cellulose furnishes strength in tension and the resin furnishes strength in shear.
The following is multiple choice question (with options) to answer.
Wood consists of mainly what kind of walls? | [
"secondary",
"primary",
"chaotic",
"aquatic"
] | A | |
SciQ | SciQ-2636 | evolution, biochemistry, plant-physiology, plant-anatomy, life
Title: Plants without bacteria? is it theoretically possible? I know from school, that all live on the Earth need bacteria as low-level "machines" that break down/extract/convert/produce chemical elements and combinations, other high-level organisms needed. But it is a natural way.
But is it possible to have a world with plants (without mammals or microorganisms and without bacteria) that could exist in the long term. Saying the atmosphere of these world has already enough nitrogen, oxygen and CO2, and of course there is water.
What could break this artificially created world with such conditions (say the world created not from low-level living structures)?
Could bacteria emerge in the world? This is the sort of question that should be considered from more than one perspective. Since this is speculation, take it as a given that there is a lot of 'what if' here.
I doubt most animals and plants can do entirely without bacteria - as you say most of the essential nutrients come from bacteria, who fix nitrogen. If only plants were left on earth, eventually the plants would use up all the nitrogen and they would have to find a way to fix more.
Can bacteria emerge from just a world of plants? I don't think viruses arise spontaneously, but since genomes often have viruses embedded in them, over the course of a billion years or so, its possible since bacteria and viruses continue to be impressed upon our genomes. Would it happen in time? Most would be skeptical whether that timing could work out.
In practice it would be hard to create a world like this. I would be interested to see whether you could sterilize the microorganisms off of seeds without killing the plant for instance. If you're asking about a small sterile environment with only plants, you could do it by adding the nutrients the plants need and giving them sunlight. Such self sustaining systems have been made with cyanobacteria and i'd be surprised if plants could not be included. But these are closed systems and judged by limited amounts of time, so whether this is an answer to your question is not clear. Here it looks like some water plants and fish have been done. If there was a plant that created CO₂ at an adequate rate its possible.
The following is multiple choice question (with options) to answer.
Viruses lack metabolic enzymes and equipment for making what? | [
"proteins",
"cells",
"acids",
"dna"
] | A | |
SciQ | SciQ-2637 | endocrinology
Excitement or stress response, including fast heart rate and breathing and anxiety: short term response: adrenaline; long-term response: cortisol
Appetite: ghrelin, leptin, adiponectin, cholecystokinin, insulin, glucagon-like peptide, gastrointestinal peptide...
Sexual drive: sex hormones, mainly testosterone and estradiol
Sleepiness: melatonin, cortisol
Depression: cortisol, sex hormones (mainly in women)
The point of this answer is to show that some of your feelings can be simply affected by hormones, which are note some ultimate forces, and that being aware of that can help you to control them to some extent.
The following is multiple choice question (with options) to answer.
What are non-steroid hormones made of? | [
"Molecules",
"proteins",
"amino acids",
"fats"
] | C | Non-steroid hormones are made of amino acids. They are not fat soluble, so they cannot diffuse across the plasma membrane of target cells. Instead, a non-steroid hormone binds to a receptor on the cell membrane (see Figure below ). The binding of the hormone triggers an enzyme inside the cell membrane. The enzyme activates another molecule, called the second messenger, which influences processes inside the cell. Most endocrine hormones are non-steroid hormones, including insulin and thyroid hormones. |
SciQ | SciQ-2638 | photons, quantum-electrodynamics, thermal-radiation, quantum-mechanics
Title: Deriving Planck's radiation law from microscopic considerations? In the usual derivation of Planck's radiation law, the energies or frequencies $\omega$ of the oscillators depend on the measurements $L$ of the black body. The model is such that the only characteristic energy is given by these oscillator excitations and in terms of the temperature $T$. Also, the oscillation amplitude vanishes on the walls. Specifically, the structure of the atom walls doesn't enter the computation. After all, that's pretty much the definition of a black body.
My question:
Are there computations (maybe QED + statistical physics?) for more realistic systems, which might model the interaction of photons with the wall atoms and which give results such that one can see the limiting case to an ideal black body?
The question came up when I wondered about the theory behind emission and absorptions of photons on the walls of a black body. Worrying about the walls can be misleading. See
A blackbody is not a blackbox
for an illuminating account of the derivation of the Planck spectrum without enclosing the field in a box. If you cant get the published version, see the arxiv version.
EDIT (25 March 2012)
Planck's Radiation Law: A Many Body Theory Perspective
discusses blackbody radiation from a many-body viewpoint. Note that they also consider interactions among the photons and electrons, and still show Planck's law is valid. This might perhaps be considered as arising from the interactions of the photons with the electrons in the walls, if you like. This paper is, of course, also referred to in the first paper I mentioned.
The following is multiple choice question (with options) to answer.
The german physicist max planck (1858–1947) used the idea that atoms and molecules in a body act like oscillators to absorb and emit this? | [
"convection",
"energy",
"radiation",
"blood"
] | C | Where is the quantization of energy observed? Let us begin by considering the emission and absorption of electromagnetic (EM) radiation. The EM spectrum radiated by a hot solid is linked directly to the solid’s temperature. (See Figure 29.3. ) An ideal radiator is one that has an emissivity of 1 at all wavelengths and, thus, is jet black. Ideal radiators are therefore called blackbodies, and their EM radiation is called blackbody radiation. It was discussed that the total intensity of the radiation varies as T 4 , the fourth power of the absolute temperature of the body, and that the peak of the spectrum shifts to shorter wavelengths at higher temperatures. All of this seems quite continuous, but it was the curve of the spectrum of intensity versus wavelength that gave a clue that the energies of the atoms in the solid are quantized. In fact, providing a theoretical explanation for the experimentally measured shape of the spectrum was a mystery at the turn of the century. When this “ultraviolet catastrophe” was eventually solved, the answers led to new technologies such as computers and the sophisticated imaging techniques described in earlier chapters. Once again, physics as an enabling science changed the way we live. The German physicist Max Planck (1858–1947) used the idea that atoms and molecules in a body act like oscillators to absorb and emit radiation. The energies of the oscillating atoms and molecules had to be quantized to correctly describe the shape of the blackbody spectrum. Planck deduced that the energy of an oscillator having a frequency f is given by. |
SciQ | SciQ-2639 | energy, condensed-matter, surface-tension, soft-matter
Title: Interface between two phases minima of the energy and interface between a minimum and a "vacuum" Cahn and Hilliard define the energy of an interface:
the difference per unit area of interface between the actual free
energy of the system and that which it would have if the properties of
the phases were continuous throughout
The following is multiple choice question (with options) to answer.
The process of microscope mountains and valleys on the surface of a material interacting with another material is called? | [
"vibration",
"friction",
"motion",
"tension"
] | B | Friction occurs because no surface is perfectly smooth. Even surfaces that look smooth to the unaided eye make look rough or bumpy when viewed under a microscope. Look at the metal surfaces in the Figure below . The aluminum foil is so smooth that it’s shiny. However, when highly magnified, the surface of metal appears to be very bumpy. All those mountains and valleys catch and grab the mountains and valleys of any other surface that contacts the metal. This creates friction. |
SciQ | SciQ-2640 | forces, weight
Title: Generating forces precisely When we like to produce known forces, we know that standard weights acting vertically on a object creates a known force. Now, what are the other methods to generate forces with accuracy? It is a 'do it yourself' experiment I would like to do, so any apparatus which uses simple devices like coils, motors, stepper/servo motors, or similar things would be great to try. A known mass tied to a thread will exert a constant force, proportional to its mass. That's the easiest of all.
A spring under a light load will create a constant force that is proportional to the extension. See Hooke's law.
A magnet and a piece of magnetic iron (or other magnet) tied to a known distance will do, too. If it is an electro-magnet, the force can be easily controlled by changing the current.
The servomotors I know usually move to a known position, and they do the force needed (up to a limit) to overcome whatever is needed to get to that position. So they will not, in general, produce a constant force.
However, if you attach a servomotor to a spring, you may get a controllable force. The details will depend on what exactly you are trying to do.
The following is multiple choice question (with options) to answer.
What do you call any device that makes work easier by changing a force? | [
"battery",
"invention",
"machine",
"technology"
] | C | A machine is any device that makes work easier by changing a force. Work is done whenever a force moves an object over a distance. The amount of work done is represented by the equation:. |
SciQ | SciQ-2641 | organs, lifespan
Title: Organs lifespan out of the body What organ can be conserved outside of the body for the longest time and still function when reimplanted? Depends what you consider an organ. Typically though it's the cells which require the most metabolic activity which have the shortest life span. The kidney is the most of the major internal organs with up to 36 hours with liver coming second at up to 16 hours.
The following is multiple choice question (with options) to answer.
In what organ is food remains turned into solid waste for excretion? | [
"non-transverse intenstine",
"large metabolism",
"large intestine",
"large tissue"
] | C | Recall that carbon dioxide travels through the blood and is transferred to the lungs where it is exhaled. In the large intestine, the remains of food are turned into solid waste for excretion. How is waste other than carbon dioxide removed from the blood? That is the role of the kidneys. |
SciQ | SciQ-2642 | immunology, cancer, immunosuppression
Title: Normal cells and the immune system Normal or healthy cells have a natural ability to avoid being attacked by the immune system.
So if a cancer cell has all inherited 'strategies' for avoiding the immune system (that are from their earlier pre-cancerous states) does this make them hard to detect or be affected by the immune system. The development of cancer has various reasons. For example in more than 50% of tumors, p53 is mutated. p53 among other things regulates mitosis and forces the cell to arrest in a specific growth state if other systems detected a mutation in the DNA.
But in your special case we have to look at major histocompatibility complexes (MHCs) and NLRC5. There are two types of MHC, namely MHC class I and class II. MHC II presents mostly bacterial peptides to CD4+ T cells causing a immune response. However, MHC I presents viral peptides and peptides from your own body. These peptides are detected by CD8+ T cells which are cytotoxic T cells initializing apoptosis. Without these own peptides natural killer (NK) cells are activated because of a missing-self signal causing apoptosis, too.
The following is multiple choice question (with options) to answer.
What is the type of cancer where bone marrow produces abnormal white blood cells? | [
"liver",
"anemia",
"leukemia",
"kidney"
] | C | Leukemia is a type of cancer in which bone marrow produces abnormal white blood cells. The abnormal cells can’t do their job of fighting infections. Like most cancers, leukemia is thought to be caused by a combination of genetic and environmental factors. It is the most common cancer in children. |
SciQ | SciQ-2643 | cell-biology
Title: Structure of Cell Are cells spheres or ovals/circles bound by phospholipidbilayer?
If they are spherical how are we able to see the nucleus through the phospholipid bilayer under a microscope? Not exactly. That is a stereotype of cells. Muscle cells are not round nor oval, but rather elongated rods. If you were to look up epithelia cells, you can quickly see that cells are grouped based on their physical characteristics; simple (round/oval & single layer), columnar, and cuboidal to name a few. Cells come in many shapes and sizes. As Hans stated, stains are vital in viewing cellular components. There is a diverse amount of stains used - which all carry a purpose and benefit in a specific application.
The following is multiple choice question (with options) to answer.
What cells are typically characterized by the polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces? | [
"epithelial cells",
"mast cells",
"nerve cells",
"connective tissue"
] | A | The Epithelial Cell Epithelial cells are typically characterized by the polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces. Particular structures found in some epithelial cells are an adaptation to specific functions. Certain organelles are segregated to the basal sides, whereas other organelles and extensions, such as cilia, when present, are on the apical surface. Cilia are microscopic extensions of the apical cell membrane that are supported by microtubules. They beat in unison and move fluids as well as trapped particles. Ciliated epithelium lines the ventricles of the brain where it helps circulate the cerebrospinal fluid. The ciliated epithelium of your airway forms a mucociliary escalator that sweeps particles of dust and pathogens trapped in the secreted mucous toward the throat. It is called an escalator because it continuously pushes mucous with trapped particles upward. In contrast, nasal cilia sweep the mucous blanket down towards your throat. In both cases, the transported materials are usually swallowed, and end up in the acidic environment of your stomach. |
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