source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-6744 | coordination-compounds, color, crystal-field-theory
$\ce{Cu(NCS)_2}$ is black probably because of ligand to metal charge transfer (the same reason $\ce{Fe(III)NCS}$ is blood red) - i.e. on absorption you transiently form $\ce{Cu(I)}$ and $\ce{NCS}$ from $\ce{Cu(II)}$ and $\ce{NCS–}$. It's more complex that that for sure, but I think it's fair to say no one knows yet, because we only worked out the structure two years ago.
If you want a lot more information about $\ce{Cu(NCS)_2}$ we published on it here https://journals.aps.org/prb/abstract/10.1103/PhysRevB.97.144421 (on the arxiv at https://arxiv.org/abs/1710.04889).
The following is multiple choice question (with options) to answer.
What compound gives tarnished copper it's green color? | [
"brass",
"zinc",
"bronze",
"copper carbonate"
] | D | A: The copper has become tarnished. The tarnish—also called patina—is a compound called copper carbonate, which is green. Copper carbonate forms when copper undergoes a chemical reaction with carbon dioxide in moist air. The green patina that forms on copper actually preserves the underlying metal. That’s why it’s not removed from the statue. Some people also think that the patina looks attractive. |
SciQ | SciQ-6745 | evolutionary-algorithms, neat, fitness-functions, fitness-design
But this blows up the score too much and now the food quality is not respected and they just gulp on anything slightly above 0. A human analogy can help you here (a variance).
Initialize all the agents with an initial value $x$; we will call this energyUnits. I Will talk later more about this.
Now, add some value, as an incentive, whenever the agent eats good food, to the energyUnits. You need to add a function that will keep decrementing the value of the agent's energyUnits, as humans degrade energy (calories) with time. We will call this function normalDegrade. This is the core part of the solution for your problem.
Now, for the bad (or poisonous) food you can be more creative with. You can simply subtract a given value whenever an agent eats poisonous food. Or you can extend your normalDegrade function with a very high downward slope. In this case, the energy units (value) of the agent will fall very rapidly. This will force the agent to look for good food to survive.
Since the ratio of food is 9:1 with poisonous, you need to initialize the value of $x$ (energyUnits) very high. You need to do some trial and error to find the right fit for you here.
Also, I am assuming that the agent is being removed from the population whenever the value of $x$ is zero or some negative value (which depends). This is important, as it makes sure that the algorithm is not wasting time in processing bad agents.
Because of this, another problem arises of the population coming to extinction. For this, you need to keep generating new agents for which any of the genetic algorithms will do. A new population with better parents of the already present generation will keep the population fit and efficient.
A good fitness function is a core to solving any problem of this kind, and sometimes it is hard to find. You might need to do some trial and error with different values to look for the right fit.
The following is multiple choice question (with options) to answer.
As the population grows, competition for food does what? | [
"decreases",
"stagnates",
"grows",
"stays the same"
] | C | inviability because the hybrid organisms simply are not viable. In another postzygotic situation, reproduction leads to the birth and growth of a hybrid that is sterile and unable to reproduce offspring of their own; this is called hybrid sterility. Habitat Influence on Speciation Sympatric speciation may also take place in ways other than polyploidy. For example, consider a species of fish that lives in a lake. As the population grows, competition for food also grows. Under pressure to find food, suppose that a group of these fish had the genetic flexibility to discover and feed off another resource that was unused by the other fish. What if this new food source was found at a different depth of the lake? Over time, those feeding on the second food source would interact more with each other than the other fish; therefore, they would breed together as well. Offspring of these fish would likely behave as their parents: feeding and living in the same area and keeping separate from the original population. If this group of fish continued to remain separate from the first population, eventually sympatric speciation might occur as more genetic differences accumulated between them. This scenario does play out in nature, as do others that lead to reproductive isolation. One such place is Lake Victoria in Africa, famous for its sympatric speciation of cichlid fish. Researchers have found hundreds of sympatric speciation events in these fish, which have not only happened in great number, but also over a short period of time. Figure 18.21 shows this type of speciation among a cichlid fish population in Nicaragua. In this locale, two types of cichlids live in the same geographic location but have come to have different morphologies that allow them to eat various food sources. |
SciQ | SciQ-6746 | electrostatics, solid-state-physics
The trick? The "head" of this thing is polar, but it's covalently bonded to these tails which are these nonpolar hydrocarbon chains. In water, all of the hydrocarbon chains want to get away from the water, so these things naturally twist around to form surfaces where the polar "heads" point outwards and the nonpolar "tails" point inwards. We say that they "self-assemble" into a bilayer, literally the water would rather be around other water so much that it accidentally kicks these things together until the phosphate groups are on the outside--these, it doesn't kick so hard. You really have to imagine the microscopic world as a constant storm of particles bashing up against each other to understand this self-assembly process!
Then the cell will often embed all sorts of other junk inside these cool boundaries by giving that junk a fatty center with polar outsides, so that it wants to "stick" inside the layer. This might include a channel to let water in or out, or how the injector needles that malicious bacteria can use to infect your cells are embedded within their walls -- or any number of other things like that! Cells often have "hairs" sticking out that help hold water molecules nearby or sometimes help them crawl around their environments.
So when your skin is touching the table, it's actually a layer of dead skin cells and hairs and such, with lots of room for air gaps, touching the table. Even if your cells themselves touched, they probably have a lot of stuff around them which keeps their actual phospholipids from touching the cell. And even if those touch the table and some of them get left behind, the rest of the ones on the nearest cell will spontaneously want, in any wet condition (and your body is one big wet condition!) to "fix" that wall.
It's just added layers of complexity atop these basic ideas that "molecules stay together more than they stick to other molecules, and some molecules attract these other molecules with a different strength than they stick to those other molecules." If you can master those basic physics ideas, then the rest is biology.
The following is multiple choice question (with options) to answer.
What is the property by which water molecules stick together? | [
"cohesion",
"plasticity",
"tension",
"vitality"
] | A | Water has some unusual properties due to its hydrogen bonds. One property is cohesion , the tendency for water molecules to stick together. The cohesive forces between water molecules are responsible for the phenomenon known as surface tension . The molecules at the surface do not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. For example, if you drop a tiny amount of water onto a very smooth surface, the water molecules will stick together and form a droplet, rather than spread out over the surface. The same thing happens when water slowly drips from a leaky faucet. The water doesn't fall from the faucet as individual water molecules but as droplets of water. The tendency of water to stick together in droplets is also illustrated by the dew drops in Figure below . |
SciQ | SciQ-6747 | 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 is the main sex hormone in males called? | [
"testosterone",
"methane",
"estrogen",
"caffeine"
] | A | Testosterone is the main sex hormone in males. Hormones are chemicals that control many body processes. Testosterone has two major roles:. |
SciQ | SciQ-6748 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
What is the name of the tube that joins the mouth to the digestive and respiratory tracts? | [
"fallopian tube",
"esophagus",
"larynx",
"pharynx"
] | D | Pharyngeal slits : Pharyngeal slits are located in the pharynx. The pharynx is the tube that joins the mouth to the digestive and respiratory tracts. |
SciQ | SciQ-6749 | botany, plant-physiology, plant-anatomy
Title: Sporophyte and gametophyte
My textbook says that in both groups of seedless plants (vascular plants, non-vascular plants) the gametophyte is a free-living plant, independent of the sporophyte.
I don't understand this statement and am now wondering if the sporophyte and gametophyte are stages in a plant's lifecycle, or are they individual parts of the plant, or are the sporophyte and the gametophyte different plants altogether? Secondly, does this differ depending on the organism?
Different plants or different structures that make up the same organism? The sporophtye is the diploid stage in the life cycle. In comparison, with humans, you and I would be sporophytes.
The Gametophyte is the haploid stage in the life cycle. In comparison, with humans, spermatozoids and ovules are gametophytes.
The following is multiple choice question (with options) to answer.
Unlike bryophyte and fern spores (which are haploid cells dependent on moisture for rapid development of gametophytes), seeds contain a diploid embryo that will germinate into what? | [
"sporophyte",
"sperm",
"gametophyte",
"ovary"
] | A | Seeds and Pollen as an Evolutionary Adaptation to Dry Land Unlike bryophyte and fern spores (which are haploid cells dependent on moisture for rapid development of gametophytes), seeds contain a diploid embryo that will germinate into a sporophyte. Storage tissue to sustain growth and a protective coat give seeds their superior evolutionary advantage. Several layers of hardened tissue prevent desiccation, and free reproduction from the need for a constant supply of water. Furthermore, seeds remain in a state of dormancy—induced by desiccation and the hormone abscisic acid—until conditions for growth become favorable. Whether blown by the. |
SciQ | SciQ-6750 | aqueous-solution
Title: Does Calcium Carbonate dissolve in an aqueous solution of sodium bicarbonate? A countertop company (Wilsonart) advises the use of sodium bicarbonate to remove limescale (solid calcium carbonate) from the worktop surface. Acidic solutions are contraindicated because the countertop (which is solid laminate, probably phenolic resin) is sensitive to acid. But, does sodium bicarbonate increase the solubility of calcium carbonate, at room temperature? (It does not seem to work)
If not, are there any other ways of increasing the solubility of calcium carbonate without resorting to acid (or other things that would damage a laminate countertop)? The chemical common sense says that the sodium bicarbonate is not going to make the limescale much more soluble.
On the other hand, the same sodium bicatrbonate is widely used as a mild abrasive (when not fully dissolved in water). This may or may not help in your case (probably not in an aestetically acceptable manner).
On the third hand, whatever your countertop is made of (it is not marble, is it?), it will likely not be vulnerable to the ordinary food-rated acids, e.g. vinegar or lemon juice. This is what you can try with little risk and a great probability of success.
The following is multiple choice question (with options) to answer.
Limestone is insoluble in water, so what can dissolve it? | [
"acid",
"dioxide",
"calcium",
"oxygen"
] | A | An element is a substance that cannot be broken down into chemically simpler components. Compounds can be broken down into simpler substances. |
SciQ | SciQ-6751 | ionic-compounds, oxidation-state, terminology
Something like the oxalate anion $\ce{C2O4^2-}$ is a multinuclear anion. Its ionic charge is $2-$, as evident by the superscript. However, you cannot always determine the constituent elements’ oxidation states a priori — the only thing you do know is that the sum of the oxidation states must equal the charge number. In oxalate, carbon has $\mathrm{+III}$ as you correctly mentioned and oxygen has $\mathrm{-II}$, as it should be of no surprise to you. Added up, this leaves us with:
$$2 \times (+3) + 4 \times (-2) = +6 + -8 = -2$$
And $2-$ is the ionic charge as we already know. This rule goes both ways, so you can use the (known) ionic charge of a multinuclear ion to determine an element’s oxidation state if the other oxidation states are known: in $\ce{SO3^2-}$ oxygen has $\mathrm{-II}$, so sulphur can only have $\mathrm{+IV}$.
The following is multiple choice question (with options) to answer.
Monatomic ions have an oxidation number equal to their what? | [
"size",
"charge",
"cost",
"length"
] | B | Monatomic ions have an oxidation number equal to their charge. Li + has an oxidation state of +1, Ba 2+ has an oxidation state of +2, I - has an oxidation state of -1, and so on. |
SciQ | SciQ-6752 | species-identification
Title: Identification of a lifeform There's a video I found on Facebook and I'm unable to figure out what the creature featured happens to be.
Adding images that have been taken from the video itself, apologies in advance since they're not high qualify images.
Can anybody shed any light on what it is?
The video was shot near Ratan Babu Ghat which is situated along the bank of Hooghly river, Kolkata, West Bengal, India. Here to be precise. This is a polyclad flatworm.
Here is a video of notoplana vitrea moving similarly to the one in the video that you linked:
https://www.asturnatura.com/especie/notoplana-vitrea.html
Here is a gallery of polyclad flatworms observed in India:
https://inaturalist.ca/observations?place_id=6681&subview=grid&taxon_id=52318
A number of the images in this gallery look similar to the one in your video, but very few of them are identified beyond this order taxon of polyclad flatworm.
The following is multiple choice question (with options) to answer.
Some flatworms are free-living carnivores that live mainly in which type of habitats? | [
"freshwater",
"Deciduous forest",
"Desert",
"aquatic"
] | D | Many flatworms are parasites with vertebrate hosts. Some are free-living carnivores that live mainly in aquatic habitats. |
SciQ | SciQ-6753 | cell-division
Title: Why doesn't cellular, replicative senescence (or the hayflick limit) constrain the normal development of an organism? The wikipedia article on cellular senescence states:
Cellular senescence is the phenomenon by which normal diploid cells cease to divide. In culture, fibroblasts can reach a maximum of 50 cell divisions before becoming senescent. This phenomenon is known as "replicative senescence", or the Hayflick limit.
The following is multiple choice question (with options) to answer.
Characterized by a short lifespan, what begin with production in the bone marrow under the influence of csfs and interleukins? | [
"solutes",
"erythrocytes",
"pathogens",
"leukocytes"
] | D | Lifecycle of Leukocytes Most leukocytes have a relatively short lifespan, typically measured in hours or days. Production of all leukocytes begins in the bone marrow under the influence of CSFs and interleukins. Secondary production and maturation of lymphocytes occurs in specific regions of lymphatic tissue known as germinal centers. Lymphocytes are fully capable of mitosis and may produce clones of cells with identical properties. This capacity enables an individual to maintain immunity throughout life to many threats that have been encountered in the past. |
SciQ | SciQ-6754 | newtonian-mechanics, newtonian-gravity, centripetal-force
Title: A question on uniform circular motion and minimum tangential velocity I've had a bit of a crisis in my understanding of circular motion and I'm hoping to clear it up here.
Would it be correct to say that the condition for a particle to be in uniform circular motion is that there is a net force $\mathbf{F}$ acting on the particle such that $$\mathbf{F}=-\frac{mv^{2}}{r}\hat{\mathbf{r}}$$
Furthermore, if an object is is in uniform circular motion along a vertical path such that, in the critical case, the only force acting on it is gravity, then what stops gravity from making the object fall towards the ground instead of continuing to follow its circular path? (I get that it is the fact that the object has a large enough tangential speed)
By requiring that $ \frac{GMm}{R^{2}}=\frac{mv^{2}}{r}$ is this because we wish to know the conditions that must be satisfied for this object to continue in a circular path (as opposed to taking to the ground due to gravity) under the influence of gravity. Circular motion is characterised by the net force satisfying $F= \frac{mv^{2}}{r}$, and so this relationship must hold in the case in which gravity is the only force acting in order for the object to maintain circular motion?! Something that is left out of (or insufficiently emphasized in) a lot of textbook treatments of centripetal acceleration/force is how physicist use this fact.
In introductory treatments, uniform circular motion plays a very similar role to equilibrium.
You are expected to read a problem, notice that some object (say a ladder with a fireman on it) is not accelerating and then proceeded to use take advantage of the equations of static equilibrium $\sum_i F_i = 0$ and $\sum_i \tau_i = 0$ to work the problem.
The following is multiple choice question (with options) to answer.
What force is perpendicular to velocity and causes uniform circular motion? | [
"centripetal force",
"circular friction",
"centripetal torque",
"tangential force"
] | A | Figure 6.11 The frictional force supplies the centripetal force and is numerically equal to it. Centripetal force is perpendicular to velocity and causes uniform circular motion. The larger the F c , the smaller the radius of curvature r and the sharper the curve. The second curve has the same v , but a larger. |
SciQ | SciQ-6755 | thermodynamics, definition
Title: Definition of "intensive" and "extensive" properties Today I was asked what does it mean for a physical property of a system to be intensive.
My first answer, loosely speaking, was:
"It is a property that is local."
I was specifically thinking about density and, by "local", I meant "that is unaffected by the dimension of the system".
Ofcourse this is a very ambiguous answer, so after that I said (shifting to extensivity's definition):
"A property is extensive if it depends on the volume of the system observed."
To be honest, I said if it's proportional to the volume, but I'm not sure the this is correct. Now, that I'm still thinking about it, I've come to the conclusion that a good definition could be:
"A property is extensive if it depends on the quantity of matter of the system observed."
Looking on wikipedia I realized that this is exactly the definition given. But I'm somewhat still uncomfortable with that: if a gas is kept in a recipient of volume $V$ at a temperature $T$, his pressure is function of the number of moles of the gas:$$p=n(RT/V).$$
And, as we know, pressure is an intensive property. So (to me) it is not really clear what does "does not depend on the quantity of matter" mean.
I also thought that one could use an operational definition (if this is the good term) of extensivity/intensivity: one example might be:
"Suppose to measure a quantity $q(S)$ relative to a system $S$. Now reproduce a copy of $S$ and measure the same quantity for the system $S+S$ given by the two identicaly systems joined. If $q(S+S)=q(S)$, then $q$ is an intensive quantity."
This seems to give a more precise sense to the "does not depend on the quantity of matter" in the above definition, but there are gaps to fill. Maybe I will try to develop better this in a second time. Now, ofcourse, the question is: what is the definition of extensivity/intensivity in rigorous and unambiguous terms? Personally, your last example is exactly how I would define intensive quantities:
The following is multiple choice question (with options) to answer.
What are physical properties that do not depend on the substance present called? | [
"internal properties",
"intensive properties",
"multilateral properties",
"extensive properties"
] | B | Physical properties that do not depend on the amount of substance present are called intensive properties . Intensive properties do not change with changes of size, shape, or scale. Examples of intensive properties are as follows in the Table below . |
SciQ | SciQ-6756 | h. Evaluate C.
i. Compute Q(7), the amount of glucose produced during the day.
Exercise 10.3.5 “Based on studies using isolated animal pancreas preparations
maintained in vitro, it has been determined that insulin is secreted in a biphasic manner in response to a marked increase in blood glucose. There is an initial burst of insulin secretion that may last 5-15 minutes, a result of secretion of preformed insulin secretory granules. This is followed by more gradual and sustained insulin secretion that results largely from biosynthesis of new insulin molecules. ” (Rhoades and Tanner, P 710)
a. A student eats a candy bar at 10:20 am. Draw a graph representative of the rate of insulin secretion between 10:00 and 11:00 am.
b. Draw a graph representative of the amount of serum insulin between 10:00 and 11:00. Assume that insulin is degraded throughout 10 to 11 am at a rate equal to insulin production before the candy is eaten, and that serum insulin at 10:00 was Iq.
CHAPTER 10. THE FUNDAMENTAL THEOREM OF CALCULUS
468
c. Write an expression for the amount of serum insulin, I(t), for t between 10:00 and 11:00 am.
Exercise 10.3.6 Equal quantities of gaseous hydrogen and iodine are mixed resulting in the reaction
which runs until I 2 is exhausted [H 2 is also exhausted). The rate at which I 2 disappears is ^°’^ 2 gm/sec. How much I 2 was initially introduced into the mixture?
a. Sketch the graph of the reaction rate, r(t) = jp^yi-
b. Approximately how much I 2 combined with H 2 during the first second?
c. Approximately how much I 2 combined with H 2 during the second second?
d. Let Q(x) be the amount of I 2 that combines with H 2 during time 0 to 2; seconds. Write an integral that is Q(x).
e. What is Q\x)l
f. Compute W'{x) for W(x) = =^.
g. Show that there is a number, C, for which Q(x) = W(x) + C.
h. Show that C = 0.2 so that Q(x) = 0.2 – g.
The following is multiple choice question (with options) to answer.
What does the secretion of the hormone cholecystokinin stimulate the release of? | [
"urea",
"insulin and pepsin",
"pancreatic juices, bile",
"sweat, saliva"
] | C | Secretion of the hormone cholecystokinin, which stimulates release of pancreatic juices and bile. |
SciQ | SciQ-6757 | electrostatics, charge
Title: How does a corona wire charge a printer drum? I understand how a laser printer works and some of the principles of static electricity, such as how objects gain a charge by electron transfer but don't understand how a high voltage corona wire can give the printer drum a net charge? A small-diameter high voltage corona wire is surrounded by an extremely high voltage field gradient immediately next to the surface of the wire. for a small enough wire diameter and a high enough (negative) voltage, it becomes possible to pluck electrons out of the wire surface and propel them away from the wire, creating a space charge surrounding the wire consisting of air molecules which have picked up one of these free electrons.
If we place the toner drum surface close by, and give it a positive charge, then it attracts the negatively-charged ions which then impinge upon its surface and build up there as a net surface charge.
The following is multiple choice question (with options) to answer.
What term is used to describe the electrostatic process used by most copy machines? | [
"microphotography",
"xerography",
"electrography",
"titanomachy"
] | B | Xerography Most copy machines use an electrostatic process called xerography—a word coined from the Greek words xeros for dry and graphos for writing. The heart of the process is shown in simplified form in Figure 18.39. A selenium-coated aluminum drum is sprayed with positive charge from points on a device called a corotron. Selenium is a substance with an interesting property—it is a photoconductor. That is, selenium is an insulator when in the dark and a conductor when exposed to light. In the first stage of the xerography process, the conducting aluminum drum is grounded so that a negative charge is induced under the thin layer of uniformly positively charged selenium. In the second stage, the surface of the drum is exposed to the image of whatever is to be copied. Where the image is light, the selenium becomes conducting, and the positive charge is neutralized. In dark areas, the positive charge remains, and so the image has been transferred to the drum. The third stage takes a dry black powder, called toner, and sprays it with a negative charge so that it will be attracted to the positive regions of the drum. Next, a blank piece of paper is given a greater positive charge than on the drum so that it will pull the toner from the drum. Finally, the paper and electrostatically held toner are passed through heated pressure rollers, which melt and permanently adhere the toner within the fibers of the paper. |
SciQ | SciQ-6758 | immunology, virology
Title: Why do people dying of immune deficiency diseases appear sick? Please forgive the obviously silly appearance of this question, and/or of the tenor which may come across as flippant or dismissive of real world suffering. My intention is none of the above.
As a layperson, I have always understood that the expression of our various colds/flus etc, while frequently mis-understood as being caused by the virus, are actually just manifestations of our own immunity fighting same. In other words, all the snot, and fever and inflammation are not caused *by the virus, they are a reaction *to the virus, as we fight it off.
My question then is why do people with AIDS (or similar immunity destroying affliction) appear sick? If they have weak or non-existent immune systems, following the above logic, would one expect to see them passing away while looking entirely healthy? Many of the symptoms of disease are indeed related to inflammation, but inflammation depends heavily (though not solely) on the innate immune response. Patients with AIDS and some of the other immunodeficiencies lose their adaptive immune response, not their innate response. Therefore they are capable of mounting an inflammatory response that is not effective in clearing pathogens (because it doesn't have help from the adaptive immune system) but can still cause symptoms.
More importantly, many symptoms of disease are not caused by the inflammatory response, but are related to organ and tissue damage caused by the infection. A patient with pneumonia may have a reduced inflammatory response but will still have difficulty breathing and signs of reduced oxygen supply simply because the lung tissue has been damaged by the pathogen.
The following is multiple choice question (with options) to answer.
Symptoms of viral diseases result from what kind of response to a virus? | [
"mutation",
"pathogenic",
"infection",
"immune"
] | D | Steps of Virus Infections A virus must use cell processes to replicate. The viral replication cycle can produce dramatic biochemical and structural changes in the host cell, which may cause cell damage. These changes, called cytopathic (causing cell damage) effects, can change cell functions or even destroy the cell. Some infected cells, such as those infected by the common cold virus known as rhinovirus, die through lysis (bursting) or apoptosis (programmed cell death or “cell suicide”), releasing all progeny virions at once. The symptoms of viral diseases result from the immune response to the virus, which attempts to control and eliminate the virus from the body, and from cell damage caused by the virus. Many animal viruses, such as HIV (human immunodeficiency virus), leave the infected cells of the immune system by a process known as budding, where virions leave the cell individually. During the budding process, the cell does not undergo lysis and is not immediately killed. However, the damage to the cells that the virus infects may make it impossible for the cells to function normally, even though the cells remain alive for a period of time. Most productive viral infections follow similar steps in the virus replication cycle: attachment, penetration, uncoating, replication, assembly, and release (Figure 21.8). Attachment A virus attaches to a specific receptor site on the host cell membrane through attachment proteins in the capsid or via glycoproteins embedded in the viral envelope. The specificity of this interaction determines the host—and the cells within the host—that can be infected by a particular virus. This can be illustrated by thinking of several keys and several locks, where each key will fit only one specific lock. |
SciQ | SciQ-6759 | quantum-mechanics, particle-physics
Title: Anything special about the internal structure of Carbon-12? In trying to understand the various structures carbon forms, I'm wondering what, if anything, is so special about having 6 neutrons and 6 protons in the nucleus. I'm aware there are permutations possible (in general) with respect to the specific arrangement of nucleons.
On the surface of the issue it seems like there is something about the internal structures possible that is peculiar... It isn't a rational train of thought but it is tempting to ask if there is something more to the internal structure - a lot of 3's and 2's appearing suggesting a geometric or numeric answer...
I've tried to think of it as a sphere packing problem, knowing that the analogy wouldn't be entirely appropriate, haven't gotten far yet. Also wondering if there is any relation to icosahedra, having 12 vertices and a plethora of interesting geometrical properties.
In short, is there anything to be said about the internal structure of Carbon-12 that's remarkable or distinct to that isotope? Carbon-12 is an "alpha-cluster nucleus," with even proton number $Z$, even neutron number $N$, and $N=Z$. The alpha-cluster nuclei up to argon or so are slightly more stable than than their "mirror nuclei" neighbors at $Z-2,N+2$, and tend to be concentrated in stellar nucleosynthesis.
Nuclear structure is a big subject where lots of different approaches are good at explaining various phenomena.
The cluster model is one approach (or at least, a phenomenon that should arise from a good microscopic nuclear model).
The shell model follows the same sort of four-quantum-number ruleset that leads to the electron structure of the periodic table. For subtle reasons the nucleon shells fill differently that electron shells do: the noble gases have $2,10,18,36,\cdots$ electrons, while the "magic nuclei" have $8,20,28,50,\cdots$ protons and/or neutrons.
For heavy nuclei you can kind of gloss over the details of what's happening inside and model the nucleus as a liquid drop.
The following is multiple choice question (with options) to answer.
The most common carbon atoms have six protons and six neutrons in their what? | [
"neuron",
"ribosomes",
"nuclei",
"membrane"
] | C | E XA MP L E 1 1. The most common carbon atoms have six protons and six neutrons in their nuclei. What are the atomic number and the mass number of these carbon atoms?. |
SciQ | SciQ-6760 | molecular-biology, circadian-rhythms, gene-regulation
Title: High frequency human genetic oscillators? The most well studied genetic oscillators in human genomes are involved in regulating the circadian clock (which operates on an approximately 24-hour cycle) and cell cycle activity (with single cycles usually lasting several hours to many days). Are there any known genetic oscillators in humans (or other mammals) that operate on shorter timescales? Here are some examples:
electric oscillators:
neural activity
cardiac automatism (0.8 ... 1 Hz)
mechanical oscillators (as a result of neural activity):
heart beats
breathing (0.2 ... 0.3 Hz)
intestinal peristaltic waves
vocal chords activity (up to a few kHz)
muscular spasm (pathological)
chemical oscillators:
insulin variation in concordance with glucose intake
endocrine oscillations
menstruation
feedback enabled metabolic pathways
See this Wikipedia page too: http://en.wikipedia.org/wiki/Oscillation#Human
When it comes to genetic oscillators, some of them follow circadian rhythm.
A typical proliferating human cell divides on average every 24 h. This division timing allows cells to synchronize with other physiological processes and with the environment. The circadian clock, which orchestrates daily rhythms, directly regulates the cell division cycle and is a major synchronizing factor [5].
Immune system:
In every single cell an oscillator goes ticking through a molecular clock operated by transcriptional/translational feedback loops driven by the rhythmic expression of circadian genes. This clock gene machinery steers daily oscillations in the regulation of immune cell activity, driving the periodicity in immune system function [1].
Glucose homeostasis:
The master circadian clock, localized in suprachiasmatic nucleus (SCN), regulates multiple metabolic pathways, while feeding behavior and metabolite availability can in turn regulate the circadian clock [2].
Retina:
The following is multiple choice question (with options) to answer.
What type of organisms have internal clocks that regulate cyclic processes? | [
"fungi",
"endogenous",
"protozoa",
"eukaryotic"
] | D | |
SciQ | SciQ-6761 | 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.
How often does condensation occur in your cells? | [
"daily",
"never",
"constantly",
"weekly"
] | C | Condensation occurs in your cells constantly. It occurs in the form of a chemical reaction. These condensation reactions involve the formation of a water molecule from two other molecules. Water forms when two molecules, such as amino acids or monosaccharides, are joined together. The amino acids join together to form peptides (or polypeptides or proteins) and the monosaccharides join together to form disaccharides or polysaccharides. |
SciQ | SciQ-6762 | ecology
Title: Do invasive species cause long-term damage to ecosystems they invade? Growing up in the U.S., I was warned at various times of the dire consequences of a variety of introduced pests (usually insects).
Japanese beetles, gypsy moths, and most recently the brown marmorated stink bug are all introduced pests that, at various times, were described as serious threats to our ecology.
These threats aren't confined to arthropods, either. The giant African land snail is causing a stir in Florida (indeed, Florida seems to suffer from an excessive variety of introduced species.
"Lack of native predators" is frequently cited as the primary reason many invasive species are considered such a risk to the ecology.
I understand that these introduced species can place tremendous pressure on native species that fill similar ecological niches, and may even push these species out of the region due to competition for food and habitat. However, do the overall ecologies that these species are introduced to adjust over long periods of time?
The numbers of Japanese beetles and gypsy moths don't seem anywhere as high as when I was a child. Has the ecosystem adjusted, or has the overpopulation self-corrected as the species ran low on food through over-consumption? Or are the populations still just as problematic now as they were 30 years ago, and I just am not seeing the bigger picture?
What is the long-term impact that we've seen from invasive, introduced species? Is there a significant difference on the long-term impact between introduced flora, arthropods, or mammals? The answer really depends on how you think of invasive. One extreme answer is to say that all things are relative, and that the concepts of local and invasive are all relative. This matters to a certain extent because ecologists draw a fuzzy line between invasive and naturalized. You could start with some basic species that we all think of as either good, local, or neutral. Take the earthworm. Most people think of it as a common native species, but the earthworm is actually an invasive species that has radically changed much of North America that came over with the Europeans. Similarly, brown trout are also invasive, coming to the US in the 1800's.
The following is multiple choice question (with options) to answer.
Overharvesting is a serious threat particularly to which species? | [
"aquatic species",
"amphibious species",
"terrestrial species",
"aerial species"
] | A | Overharvesting Overharvesting is a serious threat to many species, but particularly to aquatic species. There are many examples of regulated fisheries (including hunting of marine mammals and harvesting of crustaceans and other species) monitored by fisheries. |
SciQ | SciQ-6763 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
What are the cells that break down inorganic molecules to supply energy for the cell, and use carbon dioxide as a carbon source? | [
"fluctuations",
"Sediments",
"chemoautotrophs",
"staurikosaurus"
] | C | Chemoautotrophs are cells that break down inorganic molecules to supply energy for the cell, and use carbon dioxide as a carbon source. Chemoautotrophs include prokaryotes that break down hydrogen sulfide (H 2 S the “rotten egg” smelling gas), and ammonia (NH 4 ). Nitrosomonas , a species of soil bacterium, oxidizes NH 4 + to nitrite (NO 2 - ). This reaction releases energy that the bacteria use. Many chemoautotrophs also live in extreme environments such as deep sea vents. |
SciQ | SciQ-6764 | radiation, x-rays, cosmic-rays
Wouldn't those different types of waves have different properties?
Matter responds differently to the different wavelengths of photons, due to the increasing energy they carry which is proportional to their frequency and inversely proportional to their wavelength.
The column on the far right gives the energy of the photon. A micron wavelength is in the electron Volt range and can affect molecular distances and cohesion and living matter. Below that the interaction with matter is in bulk, not individual molecules and cells after the Ultraviolet level. The electromagnetic radiation that can affect health is ultraviolet and smaller wavelengths. The smaller the wavelength the larger the possibility of destruction of living cells which is the study of health physics: by, as the frequency increases, heating in depth,breaking of chemical bonds, ionizing, and finally destroying complete cell structures when going to MeV energies.
The following is multiple choice question (with options) to answer.
Each type of electromagnetic radiation has a characteristic range of wavelengths. the longer the wavelength (or the more stretched out it appears), the less energy is carried. short, tight waves carry what? | [
"sound",
"most energy",
"heat",
"kinetic energy"
] | B | Each type of electromagnetic radiation has a characteristic range of wavelengths. The longer the wavelength (or the more stretched out it appears), the less energy is carried. Short, tight waves carry the most energy. This may seem illogical, but think of it in terms of a piece of moving rope. It takes little effort by a person to move a rope in long, wide waves. To make a rope move in short, tight waves, a person would need to apply significantly more energy. The sun emits (Figure 5.10) a broad range of electromagnetic radiation, including X-rays and ultraviolet (UV) rays. The higher-energy waves are dangerous to living things; for example, X-rays and UV rays can be harmful to humans. |
SciQ | SciQ-6765 | the-sun, solar-system, earth, star-formation, planetary-formation
Earth Composition
Iron 32.1%
Oxygen 30.1%
Silicon 15.1%
Magnesium 13.9%
Sulfur 2.9%
Nickel 1.8%
Calcium 1.5%
Aluminum 1.4%
Other 1.2%
A couple things I notice. The sun is quite homogenous compared to earth! It is mostly composed of just two elements whereas on earth no single element makes up more than 32% of the planet's mass.
Also, there is extremely little overlap in the elements: hydrogen and helium are the only game in town on the sun, but are nearly nonexistent on earth.
This makes me very curious! What aspect of the process of the formation of the solar system was responsible for essentially segregating these elements? Is it simply that the heavier elements were "burned" away in the hotter environment of the sun, or is there some other explanation? The composition of the Sun is close to the composition of the universe as a whole. It's the Earth that's the outlier. If you look up the elemental composition of the universe as a whole, you'll see numbers for hydrogen and helium almost identical with the ones for the Sun. Theory can predict the elemental ratios. The universe started out as entirely hydrogen, and helium and a few light elements like lithium were created in the big bang. Heavier elements like oxygen and iron were made in stars, and elements heavier than iron are largely from supernovae. But enough background, let's answer your question.
Earth, along with the other planets, formed from the same cloud of dust and gas as the Sun. The cloud started out with the same elemental composition as the Sun. The cloud collapsed under the force of gravity, and somehow chunks of material (called planetesimals) started to coalesce into planets (nobody is really certain how this process worked). The proto-Sun started to emit light and warm up the surroundings. The regions closer to the Sun, where the Earth was forming, got hot enough that light elements like hydrogen evaporated from the planetesimals. Left behind were heavier elements like oxygen, silicon (which make up most rocks) and iron. The lighter elements ended up further out, which is why Jupiter has a hydrogen-rich atmosphere.
The following is multiple choice question (with options) to answer.
What are clouds on earth made of? | [
"ozone",
"carbon dioxide gas",
"water vapor",
"rain"
] | C | Clouds on Earth are made of water vapor. Venus's clouds are a lot less pleasant. They are made of carbon dioxide, sulfur dioxide, and large amounts of corrosive sulfuric acid! Scientists think the color of sunlight on Venus is reddish-brown. |
SciQ | SciQ-6766 | thermodynamics, definition
Title: Definition of "intensive" and "extensive" properties Today I was asked what does it mean for a physical property of a system to be intensive.
My first answer, loosely speaking, was:
"It is a property that is local."
I was specifically thinking about density and, by "local", I meant "that is unaffected by the dimension of the system".
Ofcourse this is a very ambiguous answer, so after that I said (shifting to extensivity's definition):
"A property is extensive if it depends on the volume of the system observed."
To be honest, I said if it's proportional to the volume, but I'm not sure the this is correct. Now, that I'm still thinking about it, I've come to the conclusion that a good definition could be:
"A property is extensive if it depends on the quantity of matter of the system observed."
Looking on wikipedia I realized that this is exactly the definition given. But I'm somewhat still uncomfortable with that: if a gas is kept in a recipient of volume $V$ at a temperature $T$, his pressure is function of the number of moles of the gas:$$p=n(RT/V).$$
And, as we know, pressure is an intensive property. So (to me) it is not really clear what does "does not depend on the quantity of matter" mean.
I also thought that one could use an operational definition (if this is the good term) of extensivity/intensivity: one example might be:
"Suppose to measure a quantity $q(S)$ relative to a system $S$. Now reproduce a copy of $S$ and measure the same quantity for the system $S+S$ given by the two identicaly systems joined. If $q(S+S)=q(S)$, then $q$ is an intensive quantity."
This seems to give a more precise sense to the "does not depend on the quantity of matter" in the above definition, but there are gaps to fill. Maybe I will try to develop better this in a second time. Now, ofcourse, the question is: what is the definition of extensivity/intensivity in rigorous and unambiguous terms? Personally, your last example is exactly how I would define intensive quantities:
The following is multiple choice question (with options) to answer.
What do extensive properties depend on the amount of? | [
"sample temperature",
"matter in a sample",
"independent variables",
"experimental controls"
] | B | Normally, electric charge is transferred when electrons leave the outer orbits of the atoms of one body (leaving it positively charged) and move to the surface of another body (causing the new surface to gain a negative net charge). In a plasma all electrons are stripped from the atoms, leaving positively charged ions and free electrons. |
SciQ | SciQ-6767 | units, notation, unit-conversion
These are just a few examples where electrical engineering is chock full of "A rate of something happening in a time period of one second" is basically defined as that something multiplied by time, as opposed to divided by time as in the case of velocity.
As far as I can tell the phrasing is effectively equivalent, but mathematically, the difference is profound, and very, very confusing. Can someone explain the difference between the two? Velocity, $m/s$, is a measure of the rate at which something moves. I guess you could define displacement as velocity-seconds, a measure of how far something moves at a given rate over a second. In your examples, it is not rates being defined, but the effect of going at a certain rate over a period of time. Amps are Coulombs per second, so you can define Coulombs as the amount of charge moved over a second at a rate of one amp. If you multiply the rate at which something happens by how long that something happens, you will get how much of that something happened.
The following is multiple choice question (with options) to answer.
What is the term for the rate at which velocity changes? | [
"transmission",
"acceleration",
"stability",
"compression"
] | B | Acceleration is a measure of the change in velocity of a moving object. It measures the rate at which velocity changes. Velocity, in turn, is a measure of the speed and direction of motion, so a change in velocity may reflect a change in speed, a change in direction, or both. Both velocity and acceleration are vectors. A vector is any measurement that has both size and direction. People commonly think of acceleration as in increase in speed, but a decrease in speed is also acceleration. In this case, acceleration is negative and called deceleration. A change in direction without a change in speed is acceleration as well. |
SciQ | SciQ-6768 | genetics, biochemistry, proteins, rna
Title: Where do amino acids get attached to tRNA and where is it synthesized? Some very basic parts of transcription/translation seem to be left out in various literature. I can't find the answer to this anywhere:
How exactly is tRNA synthesized? I realize that mRNA is synthesized through transcription and I know a lot about that. However tRNA is supposedly synthesized the same way but every time you read about transcription they just talk about how the mRNA then gets this and that...?
Where do the amino acids get attached? Is it in the nucleus or outside the nucleus?
Thanks. A pre-tRNA is transcribed from tRNA genes in DNA by RNA polymerase III. Processing occurs in the nucleus, where a 5' sequence is cleaved by RNase P, the 3's CCA motif is added, and ~10% of the nucleotides are substituted. The tRNA are transported out via the pore complexes. Aminoacyl-tRNA synthetase enzymes attach amino acids in the cytoplasm in a 2-step reaction that requires ATP. You'll find there's a unique splicing mechanism in tRNA that additionally splices out an anticodon intron which is abesnt in mature tRNA's:
The wikipedia article notes RNA Pol III generally recognizes internal control elements rather than upstream control elements as in a normal gene.
Source: Qiagen
Source: Molecular Cell Biology. 4th edition.
Addendum: I said in my post that tRNA is charged in the cytoplasm, this is somewhat true. In mammalian cells, we also see that tRNA are charged in the nucleus as well, and it might aid in the export of some of these charged tRNAs. (Source)
The following is multiple choice question (with options) to answer.
What determines which codon in the mrna the trna will bind to? | [
"exon",
"anticodon",
"amnion",
"gene"
] | B | The tRNA structure is a very important aspect in its role. Though the molecule folds into a 3-leaf clover structure, notice the anticodon arm in the lower segment of the molecule, with the amino acid attached at the opposite end of the molecule (acceptor stem). It is the anticodon that determines which codon in the mRNA the tRNA will bind to. |
SciQ | SciQ-6769 | dna, dna-sequencing, genomes, human-genome, mouse
I hope this is understandable, if you need any clarification on terms, please ask :)
The following is multiple choice question (with options) to answer.
What is the term for the complete set of genes and alleles within a population? | [
"the chromosomal pool",
"the biodiversity pool",
"the gene pool",
"the ancestral pool"
] | C | Since natural selection acts on the phenotype, if an allele causes death in a homozygous individual, aa , for example, it will not cause death in a heterozygous Aa individual. These heterozygous Aa individuals will then act as carriers of the a allele, meaning that the a allele could be passed down to offspring. People who are carriers do not express the recessive phenotype, as they have a dominant allele. This allele is said to be kept in the population's gene pool. The gene pool is the complete set of genes and alleles within a population. |
SciQ | SciQ-6770 | gas-laws, kinetic-theory-of-gases
The size of the force will be proportional to the product of the number of molecules /unit area and the size of the inward force. Both of these will be be proportional to the density ($Nm/V$) or equivalently molar concentration. The reduction in pressure can thus be written as $-a(n/V)^2$ where $a$ is a positive constant that depends on the gas and is determined only by experiment.
The following is multiple choice question (with options) to answer.
What unit of pressure is named for the scientist whose discoveries about pressure in fluids led to a law of the same name? | [
"pascal",
"newton",
"joule",
"ohm"
] | A | In the above equation for pressure, force is expressed in Newtons (N) and area is expressed in square meters (m 2 ). Therefore, pressure is expressed in N/m 2 , which is the SI unit for pressure. This unit is also called the Pascal (Pa) . It is named for the scientist Blaise Pascal whose discoveries about pressure in fluids led to a law of the same name. Pressure may also be expressed in the kilopascal (kPa), which equals 1000 Pascals. For example, the correct air pressure inside a mountain bike tire is usually about 200 kPa. |
SciQ | SciQ-6771 | inorganic-chemistry, redox
Coming to the rust question. Rust has puzzled chemists and engineers for decades because it causes millions of dollars of losses every year. Your equation is a very simplistic way of thinking that rust forms in a single step.
$$\ce{4Fe^0(s) + 3 O2(g) + 2n H2O(l) -> 2 Fe2O3·nH2O(s)}$$
It does not proceed in a single step. Our atmospheric chemistry is very complex, you have carbon dioxide, you have sulfur dioxide, nitrogen oxides, ozone, water vapors, sunlight, plenty of free radicals and plenty of minor trace components. Then there are different phases of rust too. You can have a quick look at Google Scholar and one such representative abstract [1].
In short, people still do PhD in this field and one can only imagine how complex corrosion science is.
References
The following is multiple choice question (with options) to answer.
Oxygen and what are required for rust to form? | [
"carbon",
"water",
"air",
"pressure"
] | B | Metallic Iron"). Instead, the rust continually flakes off to expose a fresh metal surface vulnerable to reaction with oxygen and water. Because both oxygen and water are required for rust to form, an iron nail immersed in. |
SciQ | SciQ-6772 | magnetic-fields, ferromagnetism
Title: Technical Term for Material That is Only Magnetic Next to A Magnet I was wondering what the technical term is for some metal(like a refrigerator door) that is not magnetic on its own like neodymium but when there is a magnet in its vicinity, it attracts to the magnet. Neodymium has a polarity but these metals don't have one, they just stick to a magnet. Is it called ferromagnetism? As far as I know there is no single term to refer to a material that is attracted by magnetism but not a magnet. Rather, there are terms that describe a material's magnetic behaviour regardless of its magnetized state.
There are a few versions. Ferromagnetic, paramagnetic, and diamagnetic.
Ferromagnetic is like iron it will be attracted to other magnets, but can also be magnetized and turned into a permanent magnet.
Paramagnetic and diamagnetic materials can't be turned into permanent magnets. The difference might be considered nitty gritty and I'm not qualified to comment.
But it sounds like you're asking for a specific term for a material that is ferromagnetic, but not currently magnetized. I don't know of one.
The following is multiple choice question (with options) to answer.
What is the process called in which a magnet loses its magnetic properties? | [
"polarization",
"demagnetization",
"diffusion",
"vectorization"
] | B | If you stroke an iron nail with a bar magnet, the nail will become a permanent (or at least long-lasting) magnet. Its magnetic domains will remain aligned even after you remove it from the magnetic field of the bar magnet. Permanent magnets can be demagnetized, however, if they are dropped or heated to high temperatures. These actions move the magnetic domains out of alignment. |
SciQ | SciQ-6773 | paleontology
Title: How to start studying dinosaurs and pre-historic mammals/sea creatures I'm kind new to this hole thing of dinosaurs that I'm really interested in, are there any good books/websites/webpages to study the biology of pre-historic creatures? Dinosaurs, mammals, fishes, anything that is not alive anymore. Also, any good books about the history of how these species evolved and the history behind them would be appreciated. Here's what it takes to really study this: you need to go through the whole bachelor program for geoscientists, that includes fundamental geodynamics like plate tectonics, magmatism, volcanism, volcanic and metamorphic rocks and generally the cycles that make up earth's internal dynamics.
Then there is the huge field of external factors, like sediment geology (that's really complicated stuff), weathering and transport and how soils come to being, diagenesis and the structures sediments can form and their classifications. Role of the ocean (that's where it starts, before all) and the atmosphere, of course.
When through that, usually 4 semesters or so, you can start to specialize. For paleontolgy you need knowledge of earth history, of course, it's subdivision, and the conditions at certain times as far as they are known. Once that's done, then comes real paleontology: Animals (invertebrates and vertebrates), plants, and their development, biological evolution (that's frequently underrated, I find), taphonomy, ... For a sturdy base count another 2-4 semesters.
You may see that even a bunch of websites, maybe all of them together, cannot replace actual study. I am not aware of any site that even gives a reasonable overview of the field. Geoscience, and thus paleontology, touch many fields of natural science.
That said, when asked "How to learn about animal paleontology ?" I allways mention Micheal Benton, Vertebrate Paleontology. It needs a basic understanding of geoscience, evolution and skeleton anatomy. Functional morphology, phylogeny and an overview over sediment geology and earth history also won't harm, but you could give it a try. Some things are explained in between.
The following is multiple choice question (with options) to answer.
The earliest animals were which kind of invertebrates? | [
"mammals",
"dinosaurs",
"insects",
"aquatic"
] | D | The partial geologic time scale in Figure below shows when some of the major events in animal evolution took place. The oldest animal fossils are about 630 million years old, so presumably animals evolved around that time or somewhat earlier. The earliest animals were aquatic invertebrates. The first vertebrates evolved around 550 million years ago. By 500 million years ago, most modern phyla of animals had evolved. The first terrestrial animals evolved about 50 million years after that. |
SciQ | SciQ-6774 | statistical-mechanics, atmospheric-science, density
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake waters, forming a gas cloud that can suffocate wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can be a trigger for such phenomenon. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes.
Picture 1: one of a number of cattle killed by a limnic eruption at Lake Nyos, Cameroon.
We can occasionally prevent the buildup of carbon dioxide by degassing the body of water.
Picture 2: a siphon used by French scientists to de-gas Lake Nyos. The carbon dioxide emerges from its deposits and bubbles into the water, floating to the top.
The following is multiple choice question (with options) to answer.
A lake is an example of what type of biome? | [
"organic biome",
"wet biome",
"natural biome",
"freshwater biome"
] | D | A lake is an example of a freshwater biome. Water in a lake generally forms three different zones based on water depth and distance from shore. |
SciQ | SciQ-6775 | electromagnetism, waves, electromagnetic-radiation, fourier-transform
Title: Does there exist some other type of electromagnetic waves? When I learned about electromagnetic waves, I was told that some accelerating charge, specifically oscillating, produces electromagnetic waves, in a way like this:
It produces a changing magnetic field, which in turn produces a changing electric field, which in turn produces a changing magnetic field, which keeps on propagating in space, and called an electromagnetic wave.
Then I was told these fields are in form of sine and cosine waves, so it clicked like this, via the differentiation loop:
$$
{+\sin}
\longrightarrow {+\cos}
\longrightarrow {-\sin}
\longrightarrow {-\cos}
\longrightarrow \cdots
.
$$
If charge oscillates as $\sin$, then magnetic field as $\cos$, electric field as $-\sin$, re-magnetic-field as $-\cos$, and so on.
But, we know about one more differentiation loop: $e^x \longrightarrow e^x \longrightarrow \cdots$. So if charge accelerates exponentially, will it produce an electromagnetic wave?? Your qualitative understanding of EM waves is based on some facts, but it is too vague to allow you to make speculations.
EM waves are described by wave solutions of Maxwell's equations. Translation in words of the precise mathematical content of the equations and their solutions can be done, but with some care, to avoid to convey something which is not in the formulae. In particular, it could be source of misunderstanding to insist too much on a causal-relation of a magnetic field creating an electric one, creating a magnetic one ... and so on. Magnetic and electric field in an EM plane wave are exactly in phase and, at a fixed point of the space they vanish or get the maximum intensity at the same time.
The following is multiple choice question (with options) to answer.
What kinds of waves are composed of various oscillating electric and magnetic fields? | [
"tidal",
"electromagnetic",
"elastic",
"seismic"
] | B | Figure 27.45 illustrates how the component of the electric field parallel to the long molecules is absorbed. An electromagnetic wave is composed of oscillating electric and magnetic fields. The electric field is strong compared with the magnetic field and is more effective in exerting force on charges in the molecules. The most affected charged particles are the electrons in the molecules, since electron masses are small. If the electron is forced to oscillate, it can absorb energy from the EM wave. This reduces the fields in the wave and, hence, reduces its intensity. In long molecules, electrons can more easily oscillate parallel to the molecule than in the perpendicular direction. The electrons are bound to the molecule and are more restricted in their movement perpendicular to the molecule. Thus, the electrons can absorb EM waves that have a component of their electric field parallel to the molecule. The electrons are much less responsive to electric fields perpendicular to the molecule and will allow those fields to pass. Thus the axis of the polarizing filter is perpendicular to the length of the molecule. |
SciQ | SciQ-6776 | temperature, sun, light, equator, insolation
Title: Why does the intensity of sunlight depend on your latitude? People at the equator get to bask in more sunlight than Santa Clause and other inhabitants of the arctic regions. Not quite as pronounced, but they get more than me too.
Why is the sunlight more intense closer to the equator and less intense farther away from it?
When I posted this question, I was not thinking about the possible ambiguities, such as "Are you talking about the exposure across a surface area with some non-perpendicular angle to the sun," or "Are you talking about the light gathered by an optic facing the sun?" There is a difference. Since "basking in sunlight" was the example use case, let us assume exposure across a surface area which is lying on the ground. As noted in the comments, this answer applies to things like sun-bathing and solar panels, but it does not apply so much to a specific point-receptor like an eyeball. If all objects in question are pointing directly at the sun, then the angle of incidence is equal for all of them and this answer does not apply.
For an optic facing its target, the amount of atmosphere that the light passes through is a very large influencer. At higher latitudes, the sun is not directly overhead, and so the light is not coming straight down through the path of least atmosphere. Instead, it comes in at an angle, passing through more of the atmosphere before it gets to you.
For sun-bathers, solar panels, and the ground in general, the sunlight absorbed and reflected does depend very much on what is described in this answer. For that reason, more expensive solar panels are mounted on devices which alter their angle to face the sun for increased light exposure. And a sun-bather could likewise increase their exposure by mounting their platform at an angle. This is the direction the rest of the answer will take.
The answer is similar to the answer to some other questions, such as "Why does the solar power intensity change with the season?" and "Why does the solar intensity change with the height of the sun in the sky (ie: with the time of day)?"
The very short, non-technical version (tl;dr)
Each unit (think "beam of sunlight") is spread over a larger area.
That might not seem intuitive at first, but that is the answer in a nutshell. To see why, continue to the long version.
The following is multiple choice question (with options) to answer.
When is the sun directly over the equator? | [
"Midsummer",
"equinox",
"Fall",
"Winter"
] | B | Solstice refers to the position of the Sun when it is closest to one of the poles. At equinox, the Sun is directly over the Equator. |
SciQ | SciQ-6777 | biochemistry, dna, rna
Title: Can a dNTP be built into a RNA strand? DNA consists of deoxyribonucleotides, RNA consists of ribonucleotides. They differ mainly (apart from the uracil / thymine difference) in the sugar part, the deoxyribose and the ribose. Those two molecules differ in the hydroxy group in the ribose which is only a single proton in the deoxyribose. This part of the sugar molecule is not directly involved in binding reactions, nevertheless it causes the whole difference in RNA and DNA.
I wonder: could a dNTP be used in an RNA strand (or vice versa)? Is it chemically possible that we have a RNA molecule that contains a dNTP next to its NTPs? This is rather easy to do if you synthesize oligonucleotides chemically and not enzymatically. This is typically done using phosphoramidite chemistry, and it allows for the synthesis of chimeric RNA/DNA oligos. You can even incorporate modified nucleosides like 2'-O-Me or LNA.
This is typically done if you want to change the properties of an oligo, e.g. if you want to make it resistant to degradation by enzymes.
The following is multiple choice question (with options) to answer.
What does the base of a nucleotide within dna consist of? | [
"protein",
"nitrogen",
"ribosomes",
"hydrogen"
] | B | It was known that DNA is composed of nucleotides , each of which contains a nitrogen-containing base, a five-carbon sugar (deoxyribose), and a phosphate group. In these nucleotides, there is one of the four possible bases: adenine (A), guanine (G), cytosine (C), or thymine (T) ( Figure below ). Adenine and guanine are purine bases, and cytosine and thymine are pyrimidine bases. |
SciQ | SciQ-6778 | as near as we please. A Trapezium or a trapezoid is a quadrilateral with at least one pair of parallel sides (Bases). The parallel sides are called the bases of the trapezoid and the other two sides are called the legs or the lateral sides. Centroid, Area, Moments of Inertia, Polar Moments of Inertia, & Radius of Gyration of a Isosceles Trapezoid If your isosceles triangle has legs of length l and height h, then the centroid is described as: G = (l/2, h/3) Centroid of a right triangle. An isosceles trapezoid is a trapezoid in which the base angles are equal so c=d. Find below formula for the centroid of trapezoid located a distance of x, Question 1: Find the centroid of trapezoid with the given dimensions; a = 12′ ; b = 5′ ; h = 5′, x = $\frac{5 + 2 \times 12}{3(12 + 5)}$ × 5. I'll let you discover it. The above isosceles trapezoid property calculator is based on the provided equations and does not account for all mathematical limitations. The centroid lies between the parallel bases. To do this, I need to first find the geometric centroid of the trapezoid. Next, we want to find the coordinates of the centroid, $(\bar{x},\bar{y})$. Centroid of an isosceles triangle. The legs may or may not be parallel to each other. The corresponding rules are given in Figure 10. A trapezoid is a 4 sided polygon that has at least one pair of sides parallel. Area… The centroid, as the name indicates, lies at the centre of a trapezoid. Centre of Mass (Centroid) for a Thin Plate. Trapezoids The trapezoid or trapezium is a quadrilateral with two parallel sides. I'll let you discover it. Ans: The centroid of a trapezoid formula can be found on Vedantu’s website. (a) 2 cm from the side whose length is 4 cm, (b) 2 cm from the side whose length is 8 cm, (c) 3 cm from the side whose length is 4 cm,
The following is multiple choice question (with options) to answer.
Which bones are flat and triangular and located at the back of the pectoral girdle? | [
"vertebrae",
"laminae",
"cochlea",
"scapulae"
] | D | The clavicles are S-shaped bones that position the arms on the body. The clavicles lie horizontally across the front of the thorax (chest) just above the first rib. These bones are fairly fragile and are susceptible to fractures. For example, a fall with the arms outstretched causes the force to be transmitted to the clavicles, which can break if the force is excessive. The clavicle articulates with the sternum and the scapula. The scapulae are flat, triangular bones that are located at the back of the pectoral girdle. They support the muscles crossing the shoulder joint. A ridge, called the spine, runs across the back of the scapula and can easily be felt through the skin (Figure 38.11). The spine of the scapula is a good example of a bony protrusion that facilitates a broad area of attachment for muscles to bone. The Upper Limb The upper limb contains 30 bones in three regions: the arm (shoulder to elbow), the forearm (ulna and radius), and the wrist and hand (Figure 38.12). |
SciQ | SciQ-6779 | javascript
// when 4 elements are same integer value
if (element1 == element2 && element2 == element3 && element3 == element4)
{
//Note that each element has it's own predefined css class e.g element1 has element1-css class
equalElementDictionary = this.fourEqualElementsCss('element1-css', 'element2-css', 'element3-css', 'element4-css')
}
else if ((element1 == element2 && element2 === element4)) { // when 3 elements are equal.
equalElementDictionary = this.threeEqualElementsCss('element1-css', 'element2-css', 'element4-css')
}
else if ((element1 == element3 && element3 === element4)) {
equalElementDictionary = this.threeEqualElementsCss('element1-css', 'element3-css', 'element4-css')
}
else if ((element2 == element3 && element3 === element4)) {
equalElementDictionary = this.threeEqualElementsCss('element2-css', 'element3-css', 'element4-css')
}
else if (element4 == element1) { // when 2 elements are equal.
equalElementDictionary = this.twoEqualElementsCss('element4-css', 'element1-css')
}
else if (element2 == element1) {
equalElementDictionary = this.twoEqualElementsCss('element2-css', 'element1-css')
}
else if (element4 == element3) {
equalElementDictionary = this.twoEqualElementsCss('element4-css', 'element3-css')
}
else if (element4 == element2) {
The following is multiple choice question (with options) to answer.
What always has the same elements in the same ratio? | [
"cell",
"mitochondria",
"compound",
"component"
] | C | A compound always consists of the same elements in the same ratio. If the same elements combine in different ratios, they form different compounds. |
SciQ | SciQ-6780 | reproduction, endocrinology, pregnancy, ovulation
The decline of the corpus luteum is correlated with a decline in serum levels of ovarian hormones including progesterone, estradiol, and inhibin A. Release from negative feedback provided by these hormones at the level of the hypothalamus and pituitary permits FSH to rise, and the cycle begins again.
You should now be able to see that:
Around the time of ovulation, the uterine lining is not fully developed and is stable due to the hormonal milieu. Menstruation does not occur.
Around the time of menstruation, FSH and LH are suppressed in a way that is not conducive to ovulation.
In theory, yes, of course there would be a lower chance of initiating a viable pregnancy (implantation rather than conception is the most obvious problem) were the endometrial lining to be unstable at the time of ovulation. The problem of luteal phase deficiency is along these lines. In this condition, the corpus luteum does not produce adequate progesterone during the luteal phase to develop the endometrial lining in such a way as to support a healthy pregnancy. However, ovulation and menstruation are still time-separated events for the reasons outlined above.
*Note that the first term is with respect to the endometrium; the second is with respect to the ovary.
Abbreviations:
GnRH - Gonadotropin Releasing Hormone; LH - Luteinizing Hormone; FSH - Follicule Stimulating Hormone
References
1. Anatomy & Physiology, Connexions Web site. Illustration is also from here.
2. Jerome Strauss, Robert Barbieri. Yen & Jaffe's Reproductive Endocrinology. September, 2013. Saunders.
The following is multiple choice question (with options) to answer.
Prior to ovulation, ovarian steroid hormones stimulate the uterus to prepare for support of what? | [
"embryo",
"childbirth",
"fetus",
"fertilization"
] | A | |
SciQ | SciQ-6781 | bond
Title: Types of bonds in a molecule For example in dinitrogen pentoxide, $\ce{N2O5}$, covalent as well as coordinate bonds (type of covalent bonds) are present, but it appears that it contains only covalent bond.
What is a proper method to find out which type of bonds are present in a molecule? Electrovalent bonds are easiest to identify. If a compound is made up of a metal and non-metal/non-metallic radical (like carbonate), then, 99.99% times, it contains electovalent bond. If a compound is made up of 2 or more non-metals/non-metallic radicals, then it contains covalent bond. Coordinate covalent bonds appear mostly with compounds containing Hydrogen element. To identify the coordinate covalent bonds, you can draw the branched structural formula of the compound and see if the shared pair of electrons are coming from the same molecule.
The following is multiple choice question (with options) to answer.
All polar compounds contain what type of bonds? | [
"weak",
"balanced",
"polar",
"strong"
] | C | Polar compounds, such as water, are compounds that have a partial negative charge on one side of each molecule and a partial positive charge on the other side. All polar compounds contain polar bonds (although not all compounds that contain polar bonds are polar. ) In a polar bond, two atoms share electrons unequally. One atom attracts the shared electrons more strongly, so it has a partial negative charge. The other atom attracts the shared electrons less strongly, so it is has a partial positive charge. In a water molecule, the oxygen atom attracts the shared electrons more strongly than the hydrogen atoms do. This explains why the oxygen side of the water molecule has a partial negative charge and the hydrogen side of the molecule has a partial positive charge. |
SciQ | SciQ-6782 | meteorology, severe-weather
The lack of rich low-level moisture is due in large part to the lack of accessibility from warmer moisture sources, particularly the Gulf of Mexico; the Rockies provide a barrier to much of the moisture reaching further west.
As you note, parts of Wyoming and Montana do see supercells and tornadoes a bit more often... but on a good topographic map, fair parts of those states are east of the Continental Divide, and so still on an "upsloping" area and thereby not blocked by sinking regions which prevent full moisture progress. They're still less-tornado prone due to elevation and increased distance from moisture, but it does happen.
The desert southwest also does manage to get monsoon moisture sneaking around the terrain further south... but further north that monsoon moisture sees additional blocking by the more elevated terrain across Nevada and Utah. (And in the southwest, a different key ingredient in tornadic supercell development is typically missing in the summer monsoon: upper-air winds sufficient for supercell development)
The Pacific Coast does see a few occasional tornadoes. But from what I've seen, they typically form from smaller storms with much less classical and intense mesocyclones. As you mention, they're a bit more in line with cold-core setups, which usually produce weaker short-lived tornadoes than classic supercells of the Plains and on east. If you plug in the events you speak of into SPCs Severe Weather Events archive, [pick the date, then click Obs and Mesoanalysis on the left, then use the dropdowns to find various parameters]
you can see that CAPE was typically very meager (well short of 1000 J/kg) and the storm structure quite weak in reflectivity in comparison to a classic supercell, more indicative of such cold-core setups.
Capping inversions may be helpful to "keep the lid on the pot" if you have strong CAPE (and therefore quality moisture) and intense updrafts to erode the cap during the day. But as it is, there isn't enough moisture typically for the cap to be a positive factor.
The following is multiple choice question (with options) to answer.
What often occurs on steep slopes in dry climates? | [
"earthquakes",
"landslides",
"tsunamis",
"volcanoes"
] | B | Landslides often occur on steep slopes in dry or semi-arid climates. The California coastline, with its steep cliffs and years of drought punctuated by seasons of abundant rainfall, is prone to landslides. Wet soil becomes slippery and heavy. Earthquakes often trigger landslides. The shaking ground causes soil and rocks to break loose and start sliding. |
SciQ | SciQ-6783 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
What kind of organisms have many different types of specialized cells with particular jobs? | [
"intricate",
"monocellular",
"crude",
"multicellular"
] | D | All living cells have certain things in common. Besides having the basic parts described above, all cells can perform the same basic functions. For example, all cells can use energy, respond to their environment, and reproduce. However, cells may also have special functions. Multicellular organisms such as you have many different types of specialized cells. Each specialized cell has a particular job. Cells with special functions generally have a shape that suits them for that job. |
SciQ | SciQ-6784 | quantum-mechanics, statistical-mechanics, double-slit-experiment, probability
Title: Probabilistic vs Statistical interpretation of Double Slit experiment Why is it assumed that the results seen in the double slit experiment are probabilistic and not just a statistical result of some unknown variable or set of variables within the system.
Ever since the origination of quantum mechanics, some theorists have searched for ways to incorporate additional determinants or "hidden variables" that, were they to become known, would account for the location of each individual impact with the target.
Wikipedia
In my opinion, the "were they to become known" is the tricky bit (to put it mildly). And, as things stand, for prediction purposes one might as well assume an inherently probabilistic nature.
(I'll add to this later.)
The following is multiple choice question (with options) to answer.
Part of the scientific process, these are statistical probabilities rather than certainties? | [
"results",
"Hypothesis",
"predictions",
"assumptions"
] | C | |
SciQ | SciQ-6785 | bioinformatics, ecology, theoretical-biology
Title: What are the basic skills required to pursue future studies in theoretical ecology? I am a student and just about to choose a project for my Master's thesis in biology. I want to pursue studies in theoretical ecology in the future. Between field ecology and computational biology (as my two possible choices) what would be the best option to go for? Suggestions are needed as soon as possible . Theoretical ecology
From wikipedia
Theoretical ecology is the scientific discipline devoted to the study of ecological systems using theoretical methods such as simple conceptual models, mathematical models, computational simulations, and advanced data analysis. Effective models improve understanding of the natural world by revealing how the dynamics of species populations are often based on fundamental biological conditions and processes. Further, the field aims to unify a diverse range of empirical observations by assuming that common, mechanistic processes generate observable phenomena across species and ecological environments. Based on biologically realistic assumptions, theoretical ecologists are able to uncover novel, non-intuitive insights about natural processes. Theoretical results are often verified by empirical and observational studies, revealing the power of theoretical methods in both predicting and understanding the noisy, diverse biological world.
The field is broad and includes foundations in applied mathematics, computer science, biology, statistical physics, genetics, chemistry, evolution, and conservation biology. Theoretical ecology aims to explain a diverse range of phenomena in the life sciences, such as population growth and dynamics, fisheries, competition, evolutionary theory, epidemiology, animal behavior and group dynamics, food webs, ecosystems, spatial ecology, and the effects of climate change.
Theoretical ecology has further benefited from the advent of fast computing power, allowing the analysis and visualization of large-scale computational simulations of ecological phenomena. Importantly, these modern tools provide quantitative predictions about the effects of human induced environmental change on a diverse variety of ecological phenomena, such as: species invasions, climate change, the effect of fishing and hunting on food network stability, and the global carbon cycle.
Computational Biology
from wikipedia
The following is multiple choice question (with options) to answer.
Ecology is a major branch of what higher-level "classification" of science? | [
"biology",
"geology",
"physics",
"chemistry"
] | A | Ecology is the study of how living things interact with each other and with their environment. It is a major branch of biology, but has areas of overlap with geography, geology, climatology, and other sciences. The study of ecology begins with two fundamental concepts in ecology: the ecosystem and their organisms. |
SciQ | SciQ-6786 | life, extremophiles
Title: How close to Earth's core can organisms live? We don't to know much about organisms living deep below the Earth's crust. Recently a team led by S. Giovanni discovered some microbes 300 m below the ocean floor. The microbes were found to be a completley new and exotic species and apparently they feed off hydrocarbons like methane and benzene. Scientists speculate that life may exist in our Solar System far below the surface of some planets or moons. This raises some questions:
What is the theoretical minimum distance from Earth's core where life can still exist. Please explain how you came up with this number. For example, there are temperature-imposed limits on many biochemical processes.
Is there the potential to discover some truly alien life forms in the Earth's mantle (by this I mean, life which is not carbon based, or life which gets its energy in ways we have not seen before, or non DNA-based life, or something along these lines)?
What is the greatest distance below the Earth's crust that life has been discovered? I believe it is the 300 m I cited above, but I am not 100% sure. There's a lot we don't know about life in deep caves, but we can bound the deepest living organism to at least 3.5 kilometers down, and probably not more than 30 kilometers down.
The worms recovered from deep mining boreholes are not particularly specifically adapted to live that far down: they have similar oxygen/temperature requirements as surface nematodes.
The Tau Tona mine is about 3.5 kilometers deep and about 60˚ C at the bottom. Hydrothermal vent life does just fine up to about 80˚C, and the crust gets warmer at "about" 25˚C per kilometer. It's entirely reasonable to expect life to about 5 kilometers down, but further than that is speculation.
Increasing pressure helps to stabilize biological molecules that would otherwise disintegrate at those temperatures, so it's not impossible there could be life even deeper. It may even be likely, given that the Tau Tona life breathes oxygen.
I am certain no life we might recognize as life exists in the upper mantle.
The following is multiple choice question (with options) to answer.
What is necessary for organisms to survive in the deepest parts of the ocean? | [
"competition",
"mutation",
"adaptations",
"reflexes"
] | C | There are few organisms that live in the deepest ocean. The ones that do have amazing adaptations to the exceptionally harsh conditions. |
SciQ | SciQ-6787 | entomology
Title: Constantly wiggling moth pupa - will it emerge soon? Today I found a moth pupa in the soil in my garden in western Sweden. It's about 15 mm long.
I have found similar ones before, but this one is wiggling a lot more, even after I put it down and put a bit of dirt over it. It's been moving for more than an hour now, but less now than in the beginning.
I was hoping to see it emerge, but if it will take more than a day or so, I will probably put it back. So, what I'm wondering is if this wiggling is any indication of how soon it will emerge. Or if there are other ways to tell.
Update: an hour later it has stopped moving. Maybe it was just very disturbed by my presence. I'm keeping it in a jar with soil and a stick for climbing up on, and I'll decide what to do with it tomorrow.
Update: 12 hours later and it seems very still. But I'm letting the question remain since I really want to know if there are any signs to look for.
Final update: After 16 days it had turned almost black, and was still very active when handled.
And after 17 days this moth came out: I posted the same question on tumblr and got an answer:
It depends on the species. This one looks like a Noctuid. I’d give it
two weeks to a month or so. You may be able to see its wings showing
through the darkening pupal case when the time draws near! Just make
sure you give it somewhere to climb up and expand its wings when it
ecloses.
After keeping it until the moth emerged, I now know that wiggliness is not an indication of maturity, but turning dark is.
The following is multiple choice question (with options) to answer.
What is the process of larva becoming an adult called? | [
"synthesis",
"parthenogenesis",
"evolution",
"metamorphosis"
] | D | After hatching, most arthropods go through one or more larval stages before reaching adulthood. The larvae may look very different from the adults. They change into the adult form in a process called metamorphosis. During metamorphosis, the arthropod is called a pupa. It may or may not spend this stage inside a special container called a cocoon. A familiar example of arthropod metamorphosis is the transformation of a caterpillar (larva) into a butterfly (adult) (see Figure below ). Distinctive life stages and metamorphosis are highly adaptive. They allow functions to be divided among different life stages. Each life stage can evolve adaptations to suit it for its specific functions without affecting the adaptations of the other stages. |
SciQ | SciQ-6788 | circulatory-system, lymphatic-system, veins
Title: How does most of lymph get back into the blood stream? (I don't mean the lymphatic system) I once read that it was because of osmotic pressure that it returns to the blood stream, by entering the venules. But why? If lymph originated as plasma how come that the solute concentration is higher in the venule? Doesn't plasma contain solutes such as salts, nutrients, oxygen, etc. ? Technically 'lymph' is used to refer to the fluid found within the lymphatic system. If it's not in the lymphatic system, it is not lymph fluid. Thus, your question is really asking about interstitial fluid or the plasma that was filtered out of blood capillaries.
The answer to your question is based on the Starling equation. Normally fluid leaves a capillary due to a net pressure that favors the interstitium. This net pressure is based on the hydrostatic pressure within the capillary being greater than the interstitial pressure of the surrounding tissues, and the oncotic pressure of the capillary (that draws fluid in) being weaker than the hydrostatic pressure of the capillary (that pushes fluid out). At the venule end of this system, the capillary oncotic pressure is stronger than the capillary hydrostatic pressure, drawing fluid back into the circulatory system.
Remember that albumin is the most important component which establishes the oncotic pressure within a vessel, and that this protein is normally NOT released out of a vessel during filtration. Thus, it passes from the capillary into its corresponding venule directly.
The following is multiple choice question (with options) to answer.
Capillaries rejoin to form venules, which convey blood to what? | [
"glands",
"extremities",
"arteries",
"veins"
] | D | |
SciQ | SciQ-6789 | everyday-chemistry, biochemistry, food-chemistry, terminology
Vitamin D is not strictly a vitamin, rather it is the precursor of one
of the hormones involved in the maintenance of calcium homeostasis and
the regulation of cell proliferation and differentiation, where it has
both endocrine and paracrine actions.
The name vitamin D1 was originally given to the crude product of irradiation of ergosterol,
which contained a mixture of ergocalciferol with inactive lumisterol (an isomer of ergosterol) and suprasterols. When ergocalciferol was identified
as the active compound, it was called vitamin D2. Later, when cholecalciferol was identified as the compound formed in the skin and found in foods, it was
called vitaminD3.
Remarks
The "Vitamin B" naming of these compounds must have been through discovery, and no clear experiments had accurately produced identity of these compounds, there were named as they were discovered but since they have been identified they they now have systematic names
abeit vitamin B still being used today and are formulated as "vitamin B complexes" in pharmaceutical products (perhaps to avoid confusion) hence systematic names are used (folic acid, pantonthenic acid, biotin, thiamin, niacin, cobalamin etc) I have never come across complexes of other Vitamins. Remember for a compound to be named a vitamin it must fit the description above, but I am not disputing the fact that other compounds with similar biological activities exist as "K" group.
References
Nutritional Biochemistry of Vitamins (Bender)
Nutritional biochemistry (Brody)
Modern Nutrition in Health and Disease (Rosset al)
The following is multiple choice question (with options) to answer.
Although it is not vital to humans, calcitonin is important for calcium homeostasis in adults of some species in what group characterized by backbones? | [
"invertebrates",
"vertebrates",
"mammals",
"reptiles"
] | B | |
SciQ | SciQ-6790 | gravity, orbital-motion, planets
Title: How could I calculate the exact amount of force I need to apply to a mass to get it to orbit around another mass? I am currently taking AP Physics, and we are learning about gravitational forces in planets. We know the equation for gravity:
$$F_g=\frac {Gm_1 m_2} {r^2}$$
But, with this equation alongside the relevant equations in mind, how would one go about finding how much force to apply to a planet, given all the needed properties? For an object of mass $m$ to maintain a circular orbit you need an inward force $F_\mathrm{inward}=\frac{mv^2}{r}$. This force is now gravity $F_\mathrm{inward}=F_\mathrm{gravity}=G\frac{mM}{r^2}$. Sovling for $v$, you obtain $$ v=\sqrt{\frac{MG}{r}}$$.
It is worth noting that this result is independent on the mass $m$ of the orbiting object. Now, time for your question: how can you reach this velocity $v$? The physical property that you want is momentum $p=mv$. Momentum is what you gain, when a force $F$ is acting on you in a time $\Delta t$: $$\Delta p =m\Delta v =F \Delta t$$.
So if you start from $v=0$, you need to apply the force $F=\frac{mv}{\Delta t}$ over the time $\Delta t$.
The following is multiple choice question (with options) to answer.
What force holds planets in their orbits? | [
"Big Bang",
"gravity",
"centrifuge",
"magnetism"
] | B | Planets are held in their orbits by the force of gravity. What would happen without gravity? Imagine that you are swinging a ball on a string in a circular motion. Now let go of the string. The ball will fly away from you in a straight line. It was the string pulling on the ball that kept the ball moving in a circle. The motion of a planet is very similar to the ball on a string. The force pulling the planet is the pull of gravity between the planet and the Sun. |
SciQ | SciQ-6791 | mechanical-engineering, structural-engineering, solid-mechanics, elasticity
Title: Does gold have elastic behavior? I know structural steel is considered to have an elastic behavior and after a certain deformation, it has a plastic behavior.
How about gold metal? Gold has a Young's modulus of 79 GPa which is very similar to silver, but significantly lower than iron or steel.
https://www.totalmateria.com/page.aspx?ID=CheckArticle&site=ktn&LN=NO&NM=230#:~:text=The%20Young%27s%20modulus%20of%20elasticity,lower%20than%20iron%20or%20steel.
The following is multiple choice question (with options) to answer.
The nature of what gives metals the properties of being ductile and malleable? | [
"liquid bonds",
"magneticism",
"metallic bonds",
"titanium bonds"
] | C | Because of their freely moving electrons, metals are good conductors of electricity. Metals also can be shaped without breaking. They are ductile (can be shaped into wires) and malleable (can be shaped into thin sheets). Metals have these properties because of the nature of their metallic bonds. |
SciQ | SciQ-6792 | 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 are the special compartments that are surrounded by membranes inside eukaryotic cells called? | [
"chloroplasts",
"organelles",
"vacuoles",
"ribosomes"
] | B | Eukaryotic cells contain special compartments surrounded by membranes, called organelles. For example, notice in this image the mitochondria, lysosomes, and Golgi apparatus. |
SciQ | SciQ-6793 | geology, rocks, mineralogy
Title: What is this Lake Michigan rock? Rock found along northern Lake Michigan, (Charlevoix, MI). Made up of very thin crystalline layers. There are small, round bubble like bumps that protrude from the surface. Doesn't show well in the picture, but the rock has a sugary appearance. I can't be definite but my three best guesses are Travertine, Agate and maybe Halite, if it fizzes in mild acid it's Travertine, a form of Limestone, if it dissolves in hot water it's Halite, or Rocksalt, otherwise if it's more or less inert it's probably Agate, an amorphous silicate. I find Halite unlikely, the other two are probably pretty equally likely in that location.
The following is multiple choice question (with options) to answer.
Molds and casts usually form in which type of rock? | [
"sedimentary",
"crystalline",
"metamorphic",
"igneous"
] | A | Molds and casts are another way organisms can be fossilized. A mold is an imprint of an organism left in rock. The organism's remains break down completely. Rock that fills in the mold resembles the original remains. The fossil that forms in the mold is called a cast ( Figure below ). Molds and casts usually form in sedimentary rock. With compression ( Figure below ), an organism's remains are put under great pressure inside rock layers. This leaves behind a dark stain in the rock. |
SciQ | SciQ-6794 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What is a hole that is dug or drilled through the ground down to an aquifer called? | [
"well",
"canal",
"ditch",
"moat"
] | A | Most groundwater does not flow out of an aquifer as a spring or geyser. So to use the water that's stored in an aquifer, people must go after it. How? They dig a well. A well ( Figure below ) is a hole that is dug or drilled through the ground down to an aquifer. |
SciQ | SciQ-6795 | newtonian-mechanics, forces, kinematics, free-body-diagram, inertia
Title: Newton's $1$st law question A long time since I posted it, still did not get a satisfactory solution. So I restate the problem -
Why does not an object attached to a string which is attached to the roof of an accelerating bus does not stay in it's initial position for an indefinite amount of time(and causing the string to stretch so much so as to break it)? In other words what is the time for which the object stays in its initial position? I expect it to stay stationary at that point, since it does initially, when a sudden change in velocity occurs.
One can still see unedited form of the question from the question history (You might want to give it a look, since it differs significantly, but the question is quite the same). Assume the object hangs vertically before the bus starts to accelerate. When the bus starts to accelerate there is instantaneous relative movement of the object relative to the bus seen by observers both on the bus and on the ground. To the observer on the bus, the bus is not moving and the object moves due to the fictitious force present in the accelerating (non-inertial) reference frame attached to the bus. To the observer on the ground (inertial reference frame), the object is stationary and the bus moves.
In both cases the relative motion of the object relative to the bus is the same and the object continues to move relative to the bus until a component of the tension force (a) counters the fictitious force for the observer on the bus and, equivalently, (b) equals the acceleration of the bus for the observer on the ground. The object moves until it reaches a new equilibrium position. If the object is "tapped" (slightly displaced from equilibrium), it acts as a pendulum about the equilibrium position. See Time period of a simple pendulum in an accelerated frame.
The following is multiple choice question (with options) to answer.
When is a moving car said to be in dynamic equilibrium? | [
"at homeostasis",
"when accelerating",
"zero net force",
"at rest"
] | C | Figure 9.3 This car is in dynamic equilibrium because it is moving at constant velocity. There are horizontal and vertical forces, but the net external force in any direction is zero. The applied force F app between the tires and the road is balanced by air friction, and the weight of the car is supported by the normal forces, here shown to be equal for all four tires. |
SciQ | SciQ-6796 | physical-chemistry, reaction-mechanism, free-energy
How does it come, that in one case the activity of the whole product AB is important and in another the single activities of the components of the product?
Equation (1) refers to a molar free energy of formation of $\ce{AB}$ from reagents $A$ and $B$, all under the same constant (P,T, composition) conditions, whereas (2) refers to the free energy of formation of a solid solution of $n_A$ moles of A and $n_B$ moles of B from pure components. Equation (1) refers to combination of A and B at a 1:1 mole ratio, or equivalently reaction to form 1 mole of $\ce{AB}$ from $n_A=n_B=\pu{1 mol}$. Reaction (2) refers to mixture of A and B at any arbitrary ratio or total number of moles. Therefore equation (2) is in a way more general. Also, equation (1) refers to a differential process (transformation to form 1 mole of product under contant conditions) whereas (2) refers to an integral (mixing) process.
For the given reaction:
$$\Delta G = \Delta G^⦵ + RT\ln{\frac{a_\ce{AB}}{a_\ce{A}\cdot a_\ce{B}}} $$
Since all components are pure solid substances, all activities equal 1 and therefore, $\Delta G = \Delta G^⦵$.
The following is multiple choice question (with options) to answer.
Every chemical reaction between molecules involves breaking and forming of what? | [
"ions",
"bonds",
"orbits",
"atomic pathways"
] | B | |
SciQ | SciQ-6797 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
The mass percentage of a solution component is defined as the ratio of the component’s mass to ________? | [
"liquid's mass",
"enough ’ s mass",
"solvent's mass",
"solution ’ s mass"
] | D | Mass Percentage Earlier in this chapter, we introduced percent composition as a measure of the relative amount of a given element in a compound. Percentages are also commonly used to express the composition of mixtures, including solutions. The mass percentage of a solution component is defined as the ratio of the component’s mass to the solution’s mass, expressed as a percentage: mass percentage =. |
SciQ | SciQ-6798 | python, algorithm, programming-challenge, python-3.x, time-limit-exceeded
pos+=1
proteins = mutated
print(proteins) I encourage you to abandon your present approach.
Instead, try expressing each of your A/B/C/D proteins as integer numbers. Then express those integer numbers in binary form, and see if you can determine the operation(s) underlying the very, very regular pattern visible in the table given in the problem.
If you transcode the "protein sequences" to a series of 2-bit numbers, I believe you can profitably perform your mutations at a high rate of speed.
The following is multiple choice question (with options) to answer.
Harmful instances of what can result in errors in protein sequence that yield non-functional proteins? | [
"radiation",
"infection",
"mutation",
"bioaccumulation"
] | C | Harmful mutations can result in errors in protein sequence, creating partially or completely non-functional proteins. |
SciQ | SciQ-6799 | acid-base, lewis-structure
For sodium hydroxide, one must realize that in an aqueous medium, the two ions will fully dissociate. The hydroxide anion will act as a Lewis base, but the sodium cation with its full outer electron shell will hardly act as an acid.$^3$
The following is multiple choice question (with options) to answer.
When dissolved in water, the base sodium hydroxide (naoh) produces sodium ions with what charge? | [
"negative",
"positive",
"constant",
"similar"
] | B | An acid also produces negative ions, and a base also produces positive ions. For example, the acid hydrogen chloride (HCl), when dissolved in water, produces negative chloride ions (Cl - ) as well as hydrogen ions. The base sodium hydroxide (NaOH) produces positive sodium ions (Na + ) in addition to hydroxide ions. These other ions also combine when the acid and base react. They form sodium chloride (NaCl). This is represented by the equation:. |
SciQ | SciQ-6800 | organic-chemistry
Title: What are the minimal chemical requirements for a food which we all can eat? I've been puzzled by the following though experiment for the past few days:
I want to make my own food from scratch, but I do not know where to start from.
I want to be 100% sure that what I eat will never contains something that can damage my body. For example: If you buy something from the local market you can not be 100% sure that it's safe to eat. (99.9 % maybe... but that's not 100%)
I want to ask you to tell me, how can I make a food that I can eat, or should I say - live on it, for the rest of my life, that's 100% safe, I can control every aspect of it's creation and has many combinations of taste because I love diversity.
Thank you for your time : )
Edit:
Because I realized my question is very broad and indeed is a little... too much scientific I want to close it. But before I do so, here's what I had in mind:
I wanted to take some chemical elements, put them in a jar, run some electricity, heat, whatever through it, filter it, do some additional processing and eat it.
I wanted to know if the stomach can take it, because I was going to eat food that's not hard to digest. Considering the three basic biomolecules used by the body are carbohydrates, lipids, and proteins, you would need to consume these three molecules only. Now we can choose three substances.
Glucose, one of the most basic carbohydrates, is needed for ATP production, so that would be a food choice there.
Any oil or butter will provide lipids.
Protein comes from a variety of sources. Meat is typically though of as the best, but nuts are a pretty good source too.
Since nuts satisfy proteins and lipids, I'd say honey roasted peanuts are the most basic food you could live off of, if you replace pure glucose for the honey.
The following is multiple choice question (with options) to answer.
What precious resource allows us to grow food as well as materials we turn into clothing and medicine? | [
"gasoline",
"petroleum",
"mercury",
"soil"
] | D | Soil is a precious resource. It allows us to grow food and the materials we use to make everything from the shirt you have on to the medicine you took this morning. Soil is made up of small pieces of rock that have broken down over hundreds, if not thousands, of years. Soil is also partly made up of the remains of plants and animals, and is home to many organisms, from earthworms to ants. But soil can be damaged by unsustainable farming practices and clear-cut logging. In this chapter, you will learn how soil forms, what it contains, and how to protect it. |
SciQ | SciQ-6801 | human-biology
Title: Is urine dirty as soon as it leaves the human body? Human urine is sterile as long as it is in the human body. But is it dirty after leaving the human body? Could you get sick from it, if you drink it or don't wash your hands, for example? It was believed for a long time that urine stored in the urinary bladder is sterile. However, Wolfe et al(1). recently found evidence of bacterial presence in the urine extracted from bladders of healthy women. In an article just published, Hilt et al. found that at least some bacteria found in the bladder of healthy women are viable and can be grown in a laboratory after extraction from the bladder).2 (Paywall). They expect that the same is the case for men.
From the Hilt et al. paper:
Thirty-five different genera and 85 different species were identified
by EQUC. The most prevalent genera isolated were Lactobacillus (15%),
followed by Corynebacterium (14.2%), Streptococcus (11.9%),
Actinomyces (6.9%), and Staphylococcus (6.9%). Other genera commonly
isolated include Aerococcus, Gardnerella, Bifidobacterium, and
Actinobaculum.
Note that these species for the most part (Actinobaculum being one exception, as a possible uropathogen) appear to be part of the normal microbiome (collection of microorganisms) in healthy people in the same way as bacteria inhabit other parts of healthy persons. Additionally, the recovered organisms required special care to achieve growth:
Most of the bacteria isolated required either increased CO2 or
anaerobic conditions for growth, along with prolonged incubation, and
they often were present in numbers below the threshold of detection
used in routine diagnostic urine culture protocols.
The following is multiple choice question (with options) to answer.
In what part of the body do escherichia coli bacteria live? | [
"your brain",
"your kidneys",
"your urethra",
"your intestines"
] | D | There are many different types of symbiotic interactions between organisms. Clockwise from top left: Escherichia coli bacteria live inside your intestines in a mutualistic relationship: the bacteria produce Vitamin K for you, and they get their food from what you eat. Clownfish that live among the tentacles of sea anemones protect the anemone from anemone-eating fish, and in turn the stinging tentacles of the anemone protect the clownfish from its predators (a special mucus on the clownfish protects it from the stinging tentacles). Similar to the E. coli , this bee has a mutualistic relationship with the flower, the bee feeds from the flower, and the flower gets pollinated by the bee. Lions are predators that feed on other organisms such as this Cape buffalo. |
SciQ | SciQ-6802 | entropy
Title: Entropy of solid, liquid, and gas at triple point of water
At the triple point of water how do the entropies of solid,
liquid, and gas compare?
I think that either they will be equal or it will be that gas > liquid > solid.
I don't know if entropy is influenced by the fact that it will be at the triple point. Can someone please elaborate? Triple point defines a situation of simultaneous equilibrium between the solid, the liquid and the gas phases.
For such an equilibrium, you simply write:
$$
\Delta S= \frac{\Delta H}{T}
$$
that rises from the fact that $\Delta G=0$.
Considering water molar ($m$) enthalpies for each phase transition at $273\,K$:
$$
\Delta H_{melting,m}=6.01\,kJ\,mol^{-1}
$$
$$
\Delta H_{vaporisation,m}=45.05\,kJ\,mol^{-1}
$$
$$
\Delta H_{sublimation,m}=51.06\,kJ\,mol^{-1}
$$
one realises that
the entropy of the gas phase is higher than the entropy of the liquid phase.
the entropy of the liquid phase is higher than the entropy of the solid phase
In this respect the triple point has no peculiar behaviour compared to other points where a two-phase equilibrium is established.
The following is multiple choice question (with options) to answer.
Which state of matter has an intermediate level of entropy between solid and gas? | [
"metal",
"plasma",
"water",
"liquid"
] | D | As expected, the entropy values for solids are low, the values for gases are high, and the ones for liquids are intermediate. Another observation can be made by looking at the three hydrocarbon gases at the end of the table. For similar molecules, a higher molecular weight generally leads to a larger standard entropy value. Although this is a drastic oversimplification, we can think of this in terms of the electrons that make up each molecule. A larger molecular weight generally means more protons, which also means more electrons. There are more ways to arrange a large number of electrons within a molecule than there are to arrange a smaller number. Although these arrangements are heavily constrained by the positions of the various nuclei, there is still an overall trend for larger molecules to have higher entropy values. |
SciQ | SciQ-6803 | atmospheric-chemistry
But some researchers have argued it does make a notable contribution in the lower atmosphere, but indirectly. There doesn't appear to be a consensus on how big this effect is (and the Wikipedia reference is old and obsolete). The argument for ozone being a notable contributor is based on the following. Hydrocarbon pollution in the lower atmosphere (often from vehicle emissions) leads to a variety of undesirable reactions some of which lead to the production of ozone (as well as many other irritating components of smog). We really don't want too much smog or ozone in the lower atmosphere because it is bad for health. Some have estimated that it also adds to the warming caused by hydrocarbon emissions (exacerbating the warming potential of methane, for example).
It is hard to judge the estimates of its contribution to warming not least because they rely on models of complex reactions caused indirectly by other pollutants. Also, the big issue with emissions leading to ozone are not its contribution to warming but its contribution to pollution which causes direct harm to people in the short term. In fact regulations around emissions has been striving to reduce those emissions since before we started worrying about global warming. And, many countries have sharply reduced them (this is a major reasons why most western countries insist on catalytic converters in their vehicles). We should reduce ozone pollution by reducing the other emissions that cause it and we have been doing that for decades.
I would argue that ozone is essentially irrelevant to global warming. We should strive to reduce it in the lower atmosphere even if we were not worried by global warming. So even if we can't agree on how big its contribution to warming is (which the literature isn't clear on) we should be reducing it as much as we can for more direct reasons.
And, even if we wanted to report its contribution to warming, the best place to account for it is to add it to the contribution of other emissions (eg methane) rather than to account for it separately as we don't directly emit it from anything.
The following is multiple choice question (with options) to answer.
In recent years, it has been hypothesized that molecules in the environment also act as? | [
"homeostasis disruptors",
"catalysts",
"pathogens",
"endocrine disruptors"
] | D | |
SciQ | SciQ-6804 | botany, terminology, nomenclature
Regnum Animale: the animals;
Regnum Vegetabile: the plants;
Regnum Lapideum: the minerals (you read it right).
Note that, in this classification, "animals" correspond to what nowadays we call animals and protozoans, and "plants" correspond to what nowadays we call plants, algae, fungi and bacteria.
You have to keep in mind that this book was first published in 1735, well before the evolutionary biology being proposed in the XIX century and established in the XX century. Therefore, it is a book published when fixism was the current paradigm, full of mentions to the scala naturae.
So, the plants (as well as the animals) showed a continuum of species, going to the lower plants (the bacteria) to the higher plants (the flowering ones). It's worth mentioning again that, by that time, bacteria were plants: Phylum Schyzophyta, to be more precise.
Thus, we have "lower plants" and "higher plants", "lower animals" and "higher animals", as well as "lower minerals" and "higher minerals"!
Unfortunately, this terminology is so embedded in the biological sciences that even today, as I mentioned, we struggle to get rid of it.
Just drop "higher plants", whatever it means
As your Wikipedia link says, "higher plants" is a synonym of vascular plants. However, there are a lot of problems here:
First, this is a remnant of the scala naturae and, just because of that, should be avoided. Think of it as a meaningless term, just like "more evolved organism".
Second, there is no clear and indisputable definition of what is a "higher" plant. Some authors used to define the "higher plants" as the Angiosperms only, or the seed plants (Angiosperms + Gymnosperms), or the vascular plants (Angiosperms, Gymnosperms and Pteridophyta).
For instance, in lusophone biology books, it was very common a division in three groups:
lower plants: bacteria and algae;
intermediate plants: bryophytes and pteridophytes;
higher plants: gymnosperms and angiosperms.
The following is multiple choice question (with options) to answer.
What is the diversity of living things called? | [
"biodiversity",
"adaptation",
"ecosystem",
"habitat"
] | A | The diversity of living things is called biodiversity. |
SciQ | SciQ-6805 | biochemistry, molecular-biology, cell-biology, cell-membrane
Title: Why should phospholipid non-polar tails be "protected" in the membrane bilayer?
lipids are arranged within the membrane with polar head towards the outer side and non polar tails towards inner side, this ensures that the non polar tail is protected from aqueous environment.
My question is why should we protect non polar part ,will it destroy in contact with polar part?
What should be the correct reason for bilayer arrangement?
What should be the correct reason for bilayer arrangement?
I'll answer your second question first, but there is an almost identical question on this site already: Why do cells have a bilayer?
There is water on the extracellular and intracellular side of the membrane. What's actually happening at a molecular dynamics level is the self-association of the hydrophobic lipid tail groups driven entropically by water. In other words the polar (hydrophilic) head-groups "prefer" interacting with the water (called the interfacial region) and the the hydrophobic tail groups "prefer" not interacting with the water. With those two preferences in play, the lipid bilayer formation we know and love emerges.
why should we protect non-polar part, will it destroy in contact with
polar part?
To directly address the first part of the question: no, nothing would be destroyed. The word "protect" isn't appropriate (it's a bit too anthropomorphic for my taste!). Here is a video showing the bilayer spontaneously assemble in a molecular dynamics simulation. Read the more thorough 2003 journal article for an idea of early MD simulations of the bilayer formation. As you can see nothing "bad" happens when the water collides with the lipid tails and the lipids aren't destroyed.
Interesting read: MEMBRANE LIPIDS OF THE PAST AND PRESENT. Good animations and explanations of different membrane formations.
For an academic perspective, I'd recommend a couple of reviews: Cournia et al., 2015 and Gerit et al., 2008.
The following is multiple choice question (with options) to answer.
All lipids have two distinct domains, a hydrophobic and a what? | [
"covalent",
"hydroceptive",
"hydrophilic",
"hydroaversive"
] | C | Membrane boundaries and capturing energy In which we consider how the aqueous nature of biological systems drives the formation of lipidbased barrier membranes and how such membranes are used to capture and store energy from the environment and chemical reactions. We consider how coupled reactions are used to drive macromolecular synthesis and growth. Defining the cell’s boundary A necessary step in the origin of life was the generation of a discrete barrier, a boundary layer, that serves to separate the living non-equilibrium reaction system from the rest of the universe. This boundary layer, the structural ancestor of the plasma membrane of modern cells, serves to maintain the integrity of the living system and mediates the movement of materials and energy into and out of the cell. Based on our current observations, the plasma membrane of all modern cells appears to be a homologous structure derived from a precursor present in the last common ancestor of life. So what is the structure of this barrier (plasma) membrane? How is it built and how does it work? When a new cell is formed its plasma membrane is derived from the plasma membrane of the progenitor cell. As the cell grows, new molecules must be added into the membrane to enable it to increase its surface area. Biological membranes are composed of two general classes of molecules, proteins (which we will discuss in much greater detail in the next section of the course) and lipids. It is worth noting explicitly here that, unlike a number of other types of molecules we will be considering, such as proteins, nucleic acids, and carbohydrates, lipids are not a structurally coherent group, that is they do not have one particular basic structure. Structurally diverse molecules, such as cholesterol and phospholipids, are both considered lipids. While there is a relatively small set of common lipid types, there are many different lipids found in biological systems and the characterization of their structure and function(s) has led to a new area of specialization known as lipidomics.214 All lipids have two distinct domains: a hydrophilic (circled in red in this figure →) domain characterized by polar regions and one or more hydrophobic/hydroapathetic domains that are usually made up of C and H and are non-polar. Lipids are amphipathic. In aqueous solution, entropic effects will drive the hydrophobic/hydroapathetic parts of the lipid out of aqueous solution. But in contrast to totally non-polar molecules, like oils, the hydrophobic/hydroapathetic part of the lipid is connected to a hydrophilic domain that is soluble in 214. |
SciQ | SciQ-6806 | evolution, neuroscience
Several types of molecules are used as neurotransmitters; their evolutionary deployment in different synapse types across animals is fascinating and still poorly understood. Many are used widely in eukaryotes for intercellular communication, but some of the biogenic amines may be present in animals as a result of the late horizontal transfer of synthesis enzymes from bacteria(Iyer et al. 2004). For instance, epinephrine and norepinephrine are important neurotransmitters in vertebrates but not in protostomes (but see Bauknecht & Jekely 2017), whereas the opposite is true of octopamine and tyramine (Figure 4). Cnidarians make a set of neurotransmitters similar to those in vertebrates (Kass-Simon & Pierobon 2007), but Nematostella expresses most nonpeptide types in the endoderm near the pharynx and testes—only peptide transmitters are found in neurons(Oren et al. 2014)
Intriguingly, ctenophores seem to use a much more restricted set, as glutamate is the only well-validated neurotransmitter (Moroz et al. 2014). This is consistent with the theory that neurons arose independently in ctenophores and planulozoans because vertebrates and most protostomes use acetylcholine at the NMJ [neuromuscular junction I assume -my edit]. However, arthropods use glutamate at the NMJ, just as ctenophores do ( Jan & Jan 1976), and cnidarians probably use neuropeptides (Oren et al. 2014). Although sponges do not have true synapses, they use γ-aminobutyric acid (GABA), glutamate, and nitric oxide to coordinate contractions (Elliott & Leys 2010). Trichoplax individuals also lack synapses,but their secretory flask cells label for FMRFamide, suggesting a conserved role in transmission for this peptide class (Smith et al. 2014).
The following is multiple choice question (with options) to answer.
Oxytocin, which stimulates the contractions of labor, is a type of what? | [
"metabolite",
"hormone",
"steroid",
"inhibitor"
] | B | A common sign that labor will be short is the so-called “bloody show. ” During pregnancy, a plug of mucus accumulates in the cervical canal, blocking the entrance to the uterus. Approximately 1–2 days prior to the onset of true labor, this plug loosens and is expelled, along with a small amount of blood. Meanwhile, the posterior pituitary has been boosting its secretion of oxytocin, a hormone that stimulates the contractions of labor. At the same time, the myometrium increases its sensitivity to oxytocin by expressing more receptors for this hormone. As labor nears, oxytocin begins to stimulate stronger, more painful uterine contractions, which—in a positive feedback loop—stimulate the secretion of prostaglandins from fetal membranes. Like oxytocin, prostaglandins also enhance uterine contractile strength. The fetal pituitary also secretes oxytocin, which increases prostaglandins even further. Given the importance of oxytocin and prostaglandins to the initiation and maintenance of labor, it is not surprising that, when a pregnancy is not progressing to labor and needs to be induced, a pharmaceutical version of these compounds (called pitocin) is administered by intravenous drip. Finally, stretching of the myometrium and cervix by a full-term fetus in the vertex (head-down) position is regarded as a stimulant to uterine contractions. The sum of these changes initiates the regular contractions known as true labor, which become more powerful and more frequent with time. The pain of labor is attributed to myometrial hypoxia during uterine contractions. |
SciQ | SciQ-6807 | genetics
General rule
The general rule is to indicate the dominant allele with a upper-case letter and the recessive allele with a lower-case letter.
The most commonly used letter is the first letter of the alphabet. The two possible alleles are a and A and the four possible genotypes here are therefore aa, aA, Aa and AA. Only aa has blue eyes in your example. Note that it is very common to merge together Aa and aA (that is to not consider whether the A allele was inherited from the father or from the mother) and just call it Aa.
More than 2 alleles OR no clear dominance relationship
It is quite common to use A1 and A2 as well but when doing so, we don't implicitly indicate a relationship of dominance. This notation also has the advantage to be able to deal with cases where there are more than two alleles segregating in the population (A1,A2,A3). Note that in reality perfect dominance is quite rare.
More than 1 locus
When dealing with more than one locus, we generally use A/a for the first locus, B/b for the second locus, C/c for the third etc... However, in general when dealing with several loci, authors don't have identical loci ad therefore they directly name them and use appropriate letters. For example, in models of recombination under control of a modifier locus, the modifier locus can often take the values M and m, while a random linked locus under purifying selection would take the letters A and a.
The following is multiple choice question (with options) to answer.
When represented by a single letter dominant alleles are represented by what case letter? | [
"uppercase",
"numeral",
"mixed letters",
"lowercase"
] | A | |
SciQ | SciQ-6808 | soil
Caliche generally forms when minerals leach from the upper layer of the soil (the A horizon) and accumulate in the next layer (the B horizon), at depths around 3 to 10 feet under the surface. It generally consists of carbonates in semiarid regions—in arid regions, less-soluble minerals form caliche layers after all the carbonates have been leached from the soil. The deposited calcium carbonate accumulates—first forming grains, then small clumps, then a discernible layer, and finally, a thicker, solid bed. As the caliche layer forms, the layer gradually becomes deeper, and eventually moves into the parent material, which lies under the upper soil horizons.
However, caliche also forms in other ways. It can form when water rises through capillary action. In an arid region, rainwater sinks into the ground very quickly. Later, as the surface dries out, the water below the surface rises, carrying up dissolved minerals from lower layers. This water movement forms a caliche that tends to grow thinner and branch out as it nears the surface. Plants can contribute to the formation of caliche, as well. Plant roots take up water through transpiration, and leave behind the dissolved calcium carbonate, which precipitates to form caliche. It can also form on outcrops of porous rocks or in rock fissures where water is trapped and evaporates. In general, caliche deposition is a slow process, but if enough moisture is present in an otherwise arid site, it can accumulate fast enough to block a drain pipe.
(photo from http://www.naturephoto-cz.com/karst-cave-photo-24442.html)
The following is multiple choice question (with options) to answer.
What do loess deposits form? | [
"diagonal cliffs",
"rotational cliffs",
"horizontal cliffs",
"vertical cliffs"
] | D | When the wind drops fine particles of silt and clay, it forms deposits called loess ( Figure below ). Loess deposits form vertical cliffs. Loess can become a thick, rich soil. That’s why loess deposits are used for farming in many parts of the world. |
SciQ | SciQ-6809 | electricity, electromagnetic-radiation, magnetic-fields, electric-fields
Title: Why is electricity not transmitted wirelessly? Why is electricity not transmitted wirelessly such that we don't need to span cables on the earth's surface? As in: electricity is transmitted wirelessly from the power plant to the household. Electricity is the flow of electrical charge - generally electrically charged particles called electrons in a wire. It can't flow through air, except in the form of electrically charged particles of air - as in a spark or lightning stroke.
Magnetic fields can travel in air, so you can send electricity by using it to make a magnetic field and then using the magnetic field at the other end to make electricity. This is how a transformer works - but it only works efficiently if the two sets of wire making the magnetic field are very close.
You can use it for sending small amounts of electricity a short distance where a wire (or connector) would be difficult, such as charging an electric toothbrush - but it's not efficent for large amounts or a long distance.
The following is multiple choice question (with options) to answer.
Electrical messages are carried by chemicals called what? | [
"receptors",
"Biotoxins",
"amino acids",
"neurotransmitters"
] | D | tiny gap between two adjacent neurons across which electrical messages are carried by chemicals called neurotransmitters. |
SciQ | SciQ-6810 | climate-change, atmosphere, climatology, aerosol
It is widely accepted that the general tendency of "global dimming"
(due to increased aerosol emissions) has been reversed above most
regions since the 1980s-1990s, i.e. there has been "global
brightening" [see Wild (2012) or IPCC (2013)]. If we accept that dimming mainly has a cooling effect,
then despite big emitters having this "shield" as you nicely put it,
the trend during recent decades is a weakening of this "shield",
i.e. a warming effect. That is: there is less warming compared to a
hypothetical absence of heavy load of aerosols above these regions,
but there is more warming compared to their own past conditions (and
as is known, the most worrying aspect of global warming is not the
high absolute temperatures, but their wildly unnatural and quickly
increasing trend).
The effect of dimming and brightening, due to
increasing and decreasing aerosols in the atmosphere respectively,
is not always cooling and warming respectively. The type of aerosols
responsible for these trends plays an important role. Reflecting
aerosols in general have a cooling effect, because they allow less
solar radiation to enter the Earth's energy balance, but absorbing
aerosols (e.g. black carbon) do not necessarily have such a cooling effect: the solar
radiation blocked by them does not reach the planetary surface, but
is nevertheless absorbed by the atmosphere, and thus contributes to
the energy balance (simply put, the energy that you do not get on
the ground, you still get in the atmosphere and thus you have no cooling
effect). [See NASA (2010)]
While generally, as you said, aerosols don't spread
evenly over the planet, it has been hypothesized that there is a
saturation aspect in their dimming effect. I.e. when large
concentrations are present an increase has a small effect, while
over places with low concentrations small increases have a
comparatively larger dimming effect. The hypothesis is that, because aerosols cause dimming not only directly, but also indirectly by acting as nuclei for cloud formation, and because cloud characteristics are more heavily affected by increases of such nuclei when their absolute levels are low than when they are already high (i.e. there is a logarithmic relation), small increases in aerosol levels over low-pollution areas can have a significant dimming effect. [See again Wild (2012)]
The following is multiple choice question (with options) to answer.
Another major cause of extinction is global warming , which is also known as? | [
"regional climate change",
"global climate change",
"sudden climate change",
"rapid climate change"
] | B | Another major cause of extinction is global warming , which is also known as global climate change. During the past century, the Earth's average temperature has risen by almost 1°C (about 1.3°F). You may not think that is significant, but to organisms that live in the wild and are constantly adapting to their environments, any climate change can be hazardous. Recall that burning fossil fuels releases gasses into the atmosphere that warm the Earth. Our increased use of fossil fuels, such as coal and oil, is changing the Earth’s climate. Any long-term change in the climate can destroy the habitat of a species. Even a brief change in climate may be too stressful for an organism to survive. For example, if the seas increase in temperature, even briefly, it may be too warm for certain types of fish to reproduce. |
SciQ | SciQ-6811 | human-biology, cell-biology, immunology, virus
Title: What is the name of the property of viruses can activate a second time, with different symptoms? The Varicella zoster virus causes chickenpox in children and shingles in adults.
It appears after the initial infection, it can go dormant in the nerve, and reactivate itself decades later.
In chickenpox - the symptoms are:
characteristic skin rash that forms small, itchy blisters, which eventually scab over. It usually starts on the chest, back, and face then spreads to the rest of the body
In shingles - the symptoms are:
a painful skin rash with blisters involving a limited area. Typically the rash occurs on either the left or right of the body or face in a single stripe.
My question is: What is the name of the property of viruses can activate a second time, with different symptoms? Viral latency is the best term to use for viruses that can lie dormant.
I have not come across a specific term for latent viruses that recur with different symptoms. This is probably because "different" is very subjective. Many pathogens can cause several different forms of disease depending on factors such as the route of exposure (i.e. where and how the pathogen got to its destination). Obviously the latent infection has a different pathophysiology to chickenpox. Due to its latency in dorsal root ganglia, shingles typically results in a localised rash, but there are less common disseminated forms of shingles that can look very similar to chickenpox.
The following is multiple choice question (with options) to answer.
What shape rash is formed from a skin infection caused by trichophyton? | [
"ring-shaped",
"rod-shaped",
"polka dot",
"striped"
] | A | skin infection caused by the fungus Trichophyton that causes a characteristic ring-shaped rash. |
SciQ | SciQ-6812 | bond, metal, ionic-compounds, covalent-compounds
Title: Metallic character of bonds? Why in discussions of percent character of bonds, are only ionic and covalent bondings discussed? Do bonds not have a partial metallic character, and are either metallic and ionic-covalent? One could think of the Fermi surface and conduction bands as an expression of the degree of metallic bonding, where metals such as aluminum or silver have overlapping empty and filled bands, allowing for electrical conduction, while semiconductors have a small gap between filled and conduction bands, offering more resistance.
As @Mithoron states, metallic bonding is a bulk property. Metals behave differently as nanoparticles -- for example, bulk silver is reflective, but nanometer particles of it are black, as in photographs.
The following is multiple choice question (with options) to answer.
What type of bonds only form in metals? | [
"metallic bonds",
"optical bonds",
"liquid bonds",
"friction bonds"
] | A | Special bonds form in metals that do not form in other classes of elements. They are called metallic bonds. The bonds explain some of the unique properties of elements in the metals class. |
SciQ | SciQ-6813 | climate-change, ice-age
Title: Was there a period of global warming before the start of the last ice age? I am curious to know if there was a period of global warming that took place before the start of the last ice age and I would like to know how long this period of global warming lasted. There was an interglacial befor the last glaciation:
glacial–interglacial cycles last ~100,000 years (middle, black line) and consist of stepwise cooling events followed by rapid warmings, as seen in this time series inferred from hydrogen isotopes in the Dome Fuji ice core from Antarctica
NOAA
The following is multiple choice question (with options) to answer.
The last major ice age took place in which era? | [
"miocene",
"pleistocene",
"pliocene",
"cenozoic"
] | B | The last major ice age took place in the Pleistocene. This epoch lasted from 2 million to 14,000 years ago. Earth’s temperature was only 5° C (9° F) cooler than it is today. But glaciers covered much of the Northern Hemisphere. In Figure below , you can see how far south they went. Clearly, a small change in temperature can have a big impact on the planet. Humans lived during this ice age. |
SciQ | SciQ-6814 | human-biology, digestive-system, immune-system, microbiome
All of these immune cells also respond to diffused chemical signals called cytokines. These molecules are secreted by some cells and are received by receptors on the host cells. Sometimes the secretion is by another immune cell, sometimes it is from a non-immune system host cell, and sometimes these molecules can be secreted by the bacteria, fungi, or worms themselves.
Depending on the chemical signals that are secreted, and how the cells are interacting at the time of the message, and which cells are receiving the message, will determine the response to the message. It is contextual. Think of the phrase "You're killing me." If someone says it, while laughing, to a good friend who is telling jokes, it means one thing. If it is screamed as someone is being choked by an attacker, it means something very different.
To summarize, the immune cells are surveilling the environment and trying to pick up what is friend and what is foe and they try to respond accordingly.
Over time and coevolution, our microbiomes have developed ways of communicating with our immune system to let it know that these microbes do not mean any harm. They are able to "train" the immune cells using chemical signaling to temper the immune systems response to them (15), and this is how they are able to coexist within our body and with an immune system that is constantly on seek an destroy missions. Also because of the mucus, our microbiome usually isn't in direct contact with our cells, so it is a different kind of interaction than if an infecting pathogen were to breech the barriers and gain access to sterile areas where no bacteria or fungi should be found, and as a result, the immune system reacts differently.
The following is multiple choice question (with options) to answer.
What signals the secretion of gastric acid? | [
"hormone",
"pepsin",
"gastrin",
"leptin"
] | C | Gastrin, which signals the secretion of gastric acid. |
SciQ | SciQ-6815 | botany, reproduction
Title: Are the seeds in a single capsicum fruit genetically identical? Hopefully not a too-basic question for the venue. I'm a chile pepper growing hobbyist and have spent some time searching around and reading up on pepper (angiosperm) reproduction, but I'm not getting a clear picture of the details.
It seems like flowers have multiple ovules and it seems like one pollen-grain landing on the stigma leads to fertilization of a single ovule. And it seems like that process produces a single seed.
But that fertilization also prompts fruit growth and flower death and capsicum fruits have many seeds, never just one (that I've ever seen).
So, does each seed have a potentially different father? Or are the multiple seeds generated through a reproductive/cloning process that I'm not seeing written about? Or something else? No, the seeds are not genetically identical. Each seed come from the fertilization of an ovum with a sperm from a separate pollen grain. Since each pollen grain can come from a different plant, the seeds will generally differ from one another.
Additionally, even ova from a single plant will not usually be genetically identical to one another. This is because the process that creates the ova (meiosis) shuffles the genes of the parent plant on then places only half into the ovum. The same kind of shuffling goes on in the creation of pollen grains.
In the chili pepper genus (Capsicum), plants are predominantly self-pollinating. This means the majority of the pollen for the seeds in a fruit will come from the very same plant. This generally reduces the amount of variation seen in the offspring compared to complete cross-plant pollination. Some cross-pollination can nevertheless occur if there are other varieties in the neighborhood. The fruit will not show the effects of the new genetic combinations present in its seed, but only a plant grown from the seed will make the differences evident.
The following is multiple choice question (with options) to answer.
Each microspore develops into a pollen grain containing a male what? | [
"gametophyte",
"sperm",
"progesterone",
"zygote"
] | A | |
SciQ | SciQ-6816 | physical-chemistry, equilibrium, kinetics
Now, for the aqueous components, the activity is expressed in terms of their concentration in the solvent. For the gaseous component, we express it in terms of its partial pressure. Substituting these conditions, we get:
$$K = \frac{P_\mathrm{C}[\mathrm{D}]}{[\mathrm{A}][\mathrm{B}]}$$
An example of where this is used is in electrochemistry.
A galvanic cell may be made which has a heterogenous reaction in which solid, aqueous and gaseous components may be given.
The Nernst equation used to calculate the EMF of such a cell is given as:
$$E_\mathrm{cell} = E^\circ_\mathrm{cell}-\frac{2.303RT}{nF}\log_{10}Q$$
Here, $Q$ is the reaction quotient. Using this, we calculate the EMF taking all the activities into consideration.
Note: The activity of a solid or the solvent is taken to be $1$ in such cases.
The following is multiple choice question (with options) to answer.
What is used to describe gas concentrations of a solution? | [
"atom fractions",
"mole fractions",
"mesh fractions",
"fixation fractions"
] | B | There are several different ways to quantitatively describe the concentration of a solution. For example, molarity was introduced in as a useful way to describe solution concentrations for reactions that are carried out in solution. Mole fractions, introduced in , are used not only to describe gas concentrations but also to determine the vapor pressures of mixtures of similar liquids. Example 4 reviews the methods for calculating the molarity and mole fraction of a solution when the masses of its components are known. |
SciQ | SciQ-6817 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
What type of organism has many different specialized cells that work together to carry out life processes? | [
"sequenced organism",
"mutated organism",
"multicellular organism",
"single-celled organism"
] | C | A multicellular organism consists of many cells and has different types of cells that are specialized for various functions. All the cells work together and depend on each other to carry out the life processes of the organism. Individual cells are unable to survive on their own. |
SciQ | SciQ-6818 | bond, ions, metal
Title: Can we picture metallic bonding as an equilibrium between electrons and cations? Can we picture metallic bonding as an equilibrium between electrons and cations?
Suppose:
$$\ce{Al^3+ + 3e- <=> Al}$$ In metals, electrons are non-localized, forming a "sea" of electrons, rather than having them localized, as in the $\ce{Na+Cl-}$ lattice of crystalline salt. See Metallic bonding for a more complete description.
It is, of course, a matter of degree, as covalent, ionic and metallic bonding can "blend" from one to the other. A bond can be considered partially ionic and covalent, for example; see these helpful graphics
The following is multiple choice question (with options) to answer.
What types of bonds hold together positive metal ions and their valence electrons? | [
"covalent bonds",
"metallic bonds",
"ionic bonds",
"toxic bonds"
] | B | Metallic bonds are the force of attraction between positive metal ions and the valence electrons that are constantly moving around them. The ions form a lattice-like structure held together by the metallic bonds. |
SciQ | SciQ-6819 | cosmology, energy-conservation, space-expansion, dark-energy, virtual-particles
So in the far future all observers in the universe will have a cosmological event horizon at around 16 billion light years and they will never be able to see farther into the universe than that. However within this distance everything behaves normally.
There is a (wildly speculative) idea that the dark energy density can increase with time eventually driving the Hubble parameter to infinity. This is called the Big Rip. This will in effect tear everything apart and destroy everything, however there is currently no evidence that this will happen.
A couple of final points. Firstly energy is not conserved in the expansion of the universe. This is the case no matter how the universe is expanding and doesn't require dark energy to do anything weird like a Big Rip. See for example:
The following is multiple choice question (with options) to answer.
The once compressed universe expanded rapidly after what nicknamed event billions of years ago? | [
"big bust",
"big bang",
"big explosion",
"good bang"
] | B | About 13.7 billion years ago, the entire universe was packed together. Everything was squeezed into a tiny volume. Then there was an enormous explosion. After this “big bang,” the universe expanded rapidly ( Figure below ). All of the matter and energy in the universe has been expanding ever since. Scientists have evidence this is how the universe formed. One piece of evidence is that we see galaxies moving away from us. If they are moving apart, they must once have been together. Also, there is energy left over from this explosion throughout the universe. The theory for the origin of the universe is called the Big Bang Theory . |
SciQ | SciQ-6820 | inorganic-chemistry
Title: Why do metals tend to lose electrons, as opposed to maintaining electric neutrality? Metals tend to lose electrons to obtain the stable noble gas configuration of 8 valence electrons.
Why do they want to obtain this configuration, and how does the strength of their "desire" to obtain this configuration compare with the "desire" to maintain neutral charge. If the answer depends on the chemical, I'm happy for you to provide some examples.
Thanks. Firstly, atoms "want" to achieve the noble gas configuration of 8 valence electrons because it is the most stable form. All that means is that it doesn't tend to react under normal conditions that we experience on Earth, therefore it will stay in that configuration for quite a while and are less likely to react. There is a more complex quantum physical answer for that but you'll have to go elsewhere for than.
The main force that keeps electrons in atoms is the electrical attraction between the electrons and the protons in the nucleus and so, if it is more energetically favourable to lose that electron in order to form a bond, then that is what will happen.
Focusing on the Alkali metals as an example, as you move down the group, they get more and more reactive. This is because of two main reasons that are a result of the electrons being further away from the nucleus:
Because they're further away, the attraction between the protons and the outer most electron is less
Secondly, taking Rubidium as an example, it has 37 electrons and 37 protons. From the perspective of the outer-most electron, there are 36 electrons repelling it, and 37 protons attracting it, therefore acting as a net charge of 1. However, if you take into account the first point, the repulsion of the closer electrons is stronger than the attraction of the protons so it could even be less than one
The following is multiple choice question (with options) to answer.
Do metals tend to gain electrons or lose electrons in chemical reactions? | [
"gain electrons",
"lose electrons",
"develop electrons",
"same number of electrons"
] | B | Metallic character refers to the level of reactivity of a metal. Metals tend to lose electrons in chemical reactions, as indicated by their low ionization energies. Within a compound, metal atoms have relatively low attraction for electrons, as indicated by their low electronegativities. By following the trend summary in the figure below, you can see that the most reactive metals would reside in the lower left portion of the periodic table. The most reactive metal is cesium, which is not found in nature as a free element. It reacts explosively with water and will ignite spontaneously in air. Francium is below cesium in the alkali metal group, but is so rare that most of its properties have never been observed. |
SciQ | SciQ-6821 | 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.
Living things evolve what characteristics that make them better suited for their environment? | [
"mutations",
"instincts",
"reflexes",
"adaptations"
] | D | As living things evolve, they generally become better suited for their environment. This is because they evolve adaptations. An adaptation is a characteristic that helps a living thing survive and reproduce in a given environment. Look at the mole in Figure below . It has tentacles around its nose that it uses to sense things by touch. The mole lives underground in the soil where it is always dark. However, by using its touch organ, it can detect even tiny food items in the soil in total darkness. The touch organ is an adaptation because it helps the mole survive in its dark, underground environment. |
SciQ | SciQ-6822 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
Where are the two tonsils located? | [
"nose",
"throat",
"sinus",
"tooth"
] | B | The two tonsils are located on either side of the throat. They trap pathogens that enter the body through the mouth or nose. |
SciQ | SciQ-6823 | periodic-table, elements
Title: Do isotones share any similarities? A trivial research in atoms and their basic theories led me to this term: "isotones"
Nuclides sharing the same number of neutrons but different atomic numbers.
A simple request or shall I say, quest:
please indicate me to any feasible similarities existing between isotones and please, DO NOT use jargon. Chemistry is determined entirely by electron interactions. Since the number of electrons in an atom is determined by the number of protons in the nucleus, the atomic number (number of protons) is what defines the chemical behavior of a given element. This means that in terms of chemical properties, isotones would have no similarities unless they happened to be in the same group (column) of the periodic table, but that would be a coincidence and would have nothing to do with the number of neutrons.
As DavePhD and ron said, the nuclear stability could be similar, since nuclear stability has a lot to do with the total number of nucleons (neutrons + protons) as well as the relative proportion of protons to neutrons. The wikipedia article on isotones discusses stability in a little more detail.
The following is multiple choice question (with options) to answer.
The chemistry of each element is determined by its number of what? | [
"electrons and neutrons",
"protons and electrons",
"nuclei and neutrons",
"protons and neutrons"
] | B | assigned a unique one-, two-, or three-letter symbol. The names of the elements are listed in the periodic table, along with their symbols, atomic numbers, and atomic masses. The chemistry of each element is determined by its number of protons and electrons. In a neutral atom, the number of electrons equals the number of protons. |
SciQ | SciQ-6824 | forces, pressure, continuum-mechanics, stress-strain
Title: Why is a force distributed over an area? Why couldn't the stress be directly equal to the force? So, my question might seem silly. I know in real life when we apply a force with our hand and push on lets say a cylinder , we know the force will be distributed over the cross section of the area, so if we had a wider area, we need more force, and if we had smaller area, then we need less force to push the cylinder a certain distance.
So its intuitive. The stress will be the force divided by the given area.
But why? like what happens at the micro-scale, and what makes the force be divided?
Thanks. Actually as @trula said the external force you apply acts only at the contact point but since all atoms are connected to each other via "interatomic forces" , your external force gets distributed all along the surface and so we need to define force per unit area viz. Stress.
The spring model of atomic structure is quite self explanatory about the interatomic force distribution.
The following is multiple choice question (with options) to answer.
What is defined as the amount of force acting on a given area? | [
"power",
"resistance",
"density",
"pressure"
] | D | Pressure is defined as the amount of force acting on a given area. It measures how concentrated a force is. |
SciQ | SciQ-6825 | energy, potential-energy
Also note that this doesn't apply to the "rest mass energy" introduced in special relativity ($E=mc^2$), which is characteristic for a given particle and which is always measured in the same reference frame as the object (at rest, no velocity). In other words, it is not relative nor arbitrary.
The following is multiple choice question (with options) to answer.
Which type of energy is the energy of anything in motion? | [
"residual engergy",
"physiological engergy",
"diffuse energy",
"kinetic engergy"
] | D | Kinetic energy is the energy of anything in motion. Your muscles move your leg, your foot kicks the ball, and the ball gains kinetic energy ( Figure below ). The kinetic energy was converted from potential energy that was in your leg before the kick. The action of kicking the ball is energy changing forms. The same is true for anything that involves change. |
SciQ | SciQ-6826 | climate-change, glaciology, ice-sheets
Title: Can ice caps reform if they disappear? Excuse my ignorance. I'm under the impression that there are various types of ice at the poles, but I don't know the difference or the significance of each type, so, in terms of whatever is actually melting in these areas as a result of climate change, is it possible that it could come back if greenhouse gas emissions were eliminated or something like that? Basically, I'm assuming that the ice caps are necessary in order to maintain the habitability of the planet for humans, so is there some sort of threshold of melting that would essentially count as a point of no return or is there always the possibility of seeing the ice caps return to safe levels? Yes, polar ice can melt -- significantly, if not completely, with substantial effects on human civilization. And it can stabilize and recover, but the question is at what pace relative to human civilization.
There are generally three types of polar ice:
Ice sheets: "An ice sheet is a mass of glacial land ice extending more than 50,000 square kilometers (20,000 square miles). The two ice sheets on Earth today cover most of Greenland and Antarctica."
Ice shelves: "Permanent floating sheets of ice that connect to a landmass."
Sea ice: "Sea ice is frozen ocean water. It forms, grows, and melts in the ocean. In contrast, icebergs, glaciers, and ice shelves float in the ocean but originate on land."
Sea ice is usually 1-2 meters thick; shelf ice is 100-200 meters thick; sheet ice is one to several kilometers thick.
The poles differ significantly. It's often pointed out that the Arctic is an ocean surrounded by land and the Antarctic is land surrounded by ocean. The North Pole is occupied by sea ice, about half of which melts every summer and reforms every winter.
At the other extreme are the ice "caps," more or less the ice sheets in Greenland and Antarctica that extrude ice in the form of glaciers and ice shelves that continuously flow into the ocean, breaking apart and melting.
To take just Greenland: Greenland has had some degree of glaciation for ~38 million years, but lost much or almost all of its ice during a warming period about 400,000 years ago, suggesting that the current ice sheet was created in that time.
The following is multiple choice question (with options) to answer.
What are large sheets of ice that cover relatively flat ground called? | [
"cellular glaciers",
"land glaciers",
"continental glaciers",
"rocky glaciers"
] | C | Continental glaciers are large ice sheets that cover relatively flat ground. These glaciers flow outward from where the greatest amounts of snow and ice accumulate. |
SciQ | SciQ-6827 | population-dynamics, population-biology
Title: Spread of a benign virus in a population over time This is a somewhat difficult (for me) population dynamics question and I wonder if someone with experience in this area could suggest a reasonable approach?
My simplifying assumptions: As a gross oversimplification, let p(k) be the world's population at generation k, and assume a smooth exponential curve that models p(k) from $k=0$ at 10,0000 B.C.E to generation $k=600$ in 2000 C.E. A generation is 20 years, and in acc. with this Wiki there are about 4 million individuals at $k=0$ and 6070 million at $k=600.$
(Of course the exponential model is bad, as world population growth appears to have been sluggish before recorded history.)
Now assume a benign virus infects 120 individuals in $k=0.$ It benignly infects all individuals who have at least one infected parent. Perhaps unimportantly, it also continues to infect 30 new individuals per million in each generation (because its found in the soil), but would not infect those already exposed.
Call infected individuals II and non-infected NI. They are indistinguishable without clinical tests--which are not done, since the virus is harmless. Since II individuals are almost certain to mate with NI individuals, in earlier generations, the number of II will grow very quickly. For a time the growth rate of II will exceed that of p(k). At some point it will be unlikely that an II individual will encounter an NI mate, however a few NI persons will still pair with NI mates--for a while.
My question is, after 600 generations, what is a reasonable estimate of the percentage of II in the population? Is is possible that there would be any NI individuals left? Or would we have some sort of dynamic equilibrium between II and NI in which (I think) the former would strongly dominate?
FWIW, the population growth model is $p(k)=4e^{0.012 k}$ with $p(k)$ in millions. For simplicity, I denote the population of non-infected individuals by $N$ and the infected ones by $I$.
Model without soil infection
The following is multiple choice question (with options) to answer.
What is the accelerating pattern of increasing population size called? | [
"reproducing growth",
"exponential growth",
"limited growth",
"induced growth"
] | B | Exponential Growth Charles Darwin, in his theory of natural selection, was greatly influenced by the English clergyman Thomas Malthus. Malthus published a book in 1798 stating that populations with unlimited natural resources grow very rapidly, and then population growth decreases as resources become depleted. This accelerating pattern of increasing population size is called exponential growth. The best example of exponential growth is seen in bacteria. Bacteria are prokaryotes that reproduce by prokaryotic fission. This division takes about an hour for many bacterial species. If 1000 bacteria are placed in a large flask with an unlimited supply of nutrients (so the nutrients will not become depleted), after an hour, there is one round of division and each organism divides, resulting in 2000 organisms—an increase of 1000. In another hour, each of the 2000 organisms will double, producing 4000, an increase of 2000 organisms. After the third hour, there should be 8000 bacteria in the flask, an increase of 4000 organisms. The important concept of exponential growth is that the population growth rate—the number of organisms added in each reproductive generation—is accelerating; that is, it is increasing at a greater and greater rate. After 1 day and 24 of these cycles, the population would have increased from 1000 to more than 16 billion. When the population size, N, is plotted over time, a J-shaped growth curve is produced (Figure 45.9). The bacteria example is not representative of the real world where resources are limited. Furthermore, some bacteria will die during the experiment and thus not reproduce, lowering the growth rate. Therefore, when calculating the growth rate of a population, the death rate (D) (number organisms that die during a particular time interval) is subtracted from the birth rate (B) (number organisms that are born during that interval). This is shown in the following formula:. |
SciQ | SciQ-6828 | charge, plasma-physics, states-of-matter, ions
Title: Can plasma be formed entirely by ions? Plasma can be formed by an altogether combination of ions, free electrons, atoms, and molecules. Searching a little bit on the internet I found that plasma can't be formed entirely by electrons, because they will fly apart. I wanted to know if plasma can be formed by ions only, as in, cations and anions, but no free electrons or neutral atoms/molecules.
Edit: Seems like electron plasma are also possible. In principle this is achievable, and is known as an ion-ion, or simply an ion plasma. In practice (that is, in the lab), however, there is always some small level of contamination, which may or may not be meaningful. Have a look at this paper, where a hydrogen ionic plasma with a fractional electron concentration of $n_e/n_{+} \sim 10^{-2}$ is produced via the use of a control grid for electron removal. The resulting ionic plasma is composed almost purely of negative and positive ions, containing molecular ions.
The following is multiple choice question (with options) to answer.
Ions can be formed when atoms lose what other particles? | [
"neutrons",
"electrons",
"shells",
"protons"
] | B | By losing an electron, the sodium atom becomes a sodium ion. It now has more protons than electrons and a charge of +1. Positive ions such as sodium are given the same name as the element. The chemical symbol has a plus sign to distinguish the ion from an atom of the element. The symbol for a sodium ion is Na + . |
SciQ | SciQ-6829 | desert
Title: When was the first not-icy desert formed? For how long have deserts existed and which one would be the first to be created? I'm talking about arid, dry deserts, not the Antarctic or Arctic or any other icy deserts. Deserts have existed since at least the Permian period (299-251 million years ago) when the world's continents had combined into the Pangaea supercontinent. Stretching from pole to pole, this land mass was large enough that portions of its interior received little or no precipitation, according the University of California Museum of Paleontology.
Pangaea broke into smaller land masses which were moved across the surface by tectonic forces, a process that both changed global climate patterns and the climate those continents were exposed to. As a result, current desert regimes date back to no more than 65.5 million years, according to this Encyclopedia Britannica article:
The desert environments of the present are, in geologic terms,
relatively recent in origin. They represent the most extreme result of
the progressive cooling and consequent aridification of global
climates during the Cenozoic Era (65.5 million years ago to the
present), which also led to the development of savannas and scrublands
in the less arid regions near the tropical and temperate margins of
the developing deserts. It has been suggested that many typical modern
desert plant families, particularly those with an Asian centre of
diversity such as the chenopod and tamarisk families, first appeared
in the Miocene (23 to 5.3 million years ago), evolving in the salty,
drying environment of the disappearing Tethys Sea along what is now
the Mediterranean–Central Asian axis.
Which would put the oldest of "modern" desert somewhere in the region of what later became North Africa or South Asia.
The following is multiple choice question (with options) to answer.
Deserts are generally dry ecosystems having very little what? | [
"mountains",
"snowfall",
"heat",
"rainfall"
] | D | frequent algal blooms d. little or no vegetation 12. Which of the following is an example of a weather event? a. The hurricane season lasts from June 1 through November 30. The amount of atmospheric CO2 has steadily increased during the last century. A windstorm blew down trees in the Boundary Waters Canoe Area in Minnesota on July 4, 1999. Deserts are generally dry ecosystems having very little rainfall. Which of the following natural forces is responsible for the release of carbon dioxide and other atmospheric gases? a. the Milankovitch cycles b. volcanoes c. solar intensity d. burning of fossil fuels. |
SciQ | SciQ-6830 | It doesn't really matter, I think this is all be above me.
Melody Apr 5, 2015
#22
0
Hi All,
I was intrigued by the answer Melody gave and would like to comment on it. See the approach of diving people into groups of same sizes is a pretty standard one. For example if you want ot divide a group of 8 people into pairs (i.e. all equal sizes) the standard approach shall be 8!/(((2!)^4)*4!), i.e divide 8! by 2!*2!*2!*2! and multiply the whole with 1/4! (since there are 4 groups of equal sizes) and it returns the same answer as 105. This can be used for anything. (3N as well). Say N people need to be distributed in 2 groups of 2 and 1 group of 3, then it is N!/2!*2!*3!*2! (i.e. 2! -> since 2 items belon to one group, 2! -> since 2 items belon to one group,3! -> since 2 items belon to one group, 2! -> since 2 groups are identical in size.)
Now that concept out of the way, the thing that intrigued me is its application in geometrical figures, like the one discussed. I think it has happened because in such a scenario we fix one group namely AB and then form 3 paired groups, and since it is a square all the 8 arrangements will be identical, hence giving us the formula (2k-1)!/2^k-1*3!
i.e. (2k)!/(2k*((2!)^3)*3!)
I think that is the case. But definitely for sure such a formula wouldnt work out in other geometrical figures or if the numbers werent 8 for example, i.e we have 6 persons and there are 8 places.
Guest Nov 25, 2015
#23
+5
After all these discuession, i just wanna post the correct answer just to make it clear.
There are 8! ways to place the people around the table, but this counts each valid arrangement 4 times (if you move each person 2, 4, or 6 places clockwise you get the same arrangement). The answer is 8!/4 = 10080.
The following is multiple choice question (with options) to answer.
The average number of individuals per unit of area can be expressed as what? | [
"the percent of population",
"percent density",
"total density",
"population density"
] | D | Population density just gives the average number of individuals per unit of area or volume. Often, individuals in a population are not spread out evenly. Instead, they may live in clumps or some other pattern (see Figure below ). The pattern may reflect characteristics of the species or its environment. Population distribution describes how the individuals are distributed, or spread throughout their habitat. |
SciQ | SciQ-6831 | fluid-dynamics, water
Title: Mysteries of the water meter Recently, I got an exceptionally high bill for water consumption. I went to check my water meter, and saw that it rotates in a pace of about 200 cc per minute, even though all the faucets in my home are closed. So, I concluded that there is probably a hidden leakage somewhere in my home.
But then I did the following experiment: I closed the main faucet (the one just next to the water meter). The water meter immediately stopped rotating. I waited for 1 minute, and then opened the main faucet again. At that second, the water meter rotated very fast - it made about 400 cc in a second! After that second, it returned to its previous pace of 200 cc per minute.
Is there a physical explanation for this phoenomenon?
(Some details that may be relevant: I live in the 2nd floor in a 3-floor house. We get our water from the urban pool, located at the top of the hill in the center of town). Yes, you have a leak. The fact that there is no obvious pool of water somewhere means that the leaking water is going down the drain.
The most likely culprit is the plunger at the bottom of the toilet tank. If it leaked a little, the float valve would be open just a bit on average. In effect, the toilet bowls would be constantly "filling", but doing it so slowly that you might not notice and so there wouldn't be any gratuitous flushes. This also explains the fast water flow after having been off for a while. While the main valve was off, the toilet tank got drained a bit. When the water got turned back on again, the float valve was well open because the tank level was low.
To test this theory, close the shutoff valve for the toilet and see if the slow drain shown by the meter stops.
The following is multiple choice question (with options) to answer.
The top 200 meters of water is called what zone? | [
"the subterranean zone",
"the photic zone",
"the stratosphere",
"the biotic zone"
] | B | The top 200 meters of water is the photic zone. Producers here include seaweeds and phytoplankton. Other organisms are plentiful. They include zooplankton and animals such as fish, whales, and dolphins. |
SciQ | SciQ-6832 | solutions, molecules, structural-formula, mixtures, colloids
Title: Is there a way to find the mixture type with just the molecular formulas and masses of the solute and solvent? If you had the molecular formula and molar mass of a solvent and a solute and no other specific information about the two, could one deduce the type of mixture (suspension, colloid, solution) they would create? Formula alone does not give you the structure. But if you have the structure of the molecules, there are molecular/thermodynamic models which take into account group contributions for every section of a molecule. These can help calculate and predict phase behaviour and mixture type. See PC-SAFT as an example.
The following is multiple choice question (with options) to answer.
A homogeneous mixture with tiny particles in it is known as what? | [
"plasmid",
"element",
"solution",
"structure"
] | C | A solution is a homogeneous mixture with tiny particles. An example is salt water. The particles of a solution are too small to reflect light. As a result, you cannot see them. That’s why salt water looks the same as pure water. The particles of solutions are also too small to settle or be filtered out of the mixture. |
SciQ | SciQ-6833 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
What is the term for decomposers that consume dead leaves, animal feces, and other organic debris collected on the ground or at the bottom of water? | [
"detritivores",
"consumers",
"recyclers",
"scavengers"
] | A | Detritivores are decomposers that consume dead leaves, animal feces, and other organic debris that collects on the ground or at the bottom of a body of water. Examples of detritivores include earthworms and catfish. You can see another example in Figure below . |
SciQ | SciQ-6834 | thermodynamics, pressure
Title: What is pressure energy in a closed system? Let's consider a gas inside a closed cylinder with a piston. This can be considered a closed system. The First Law of Thermodynamics (FLD) for a closed stationary system can be given as
Q = U + W
where,
Q is the heat out of the system
U is the change in internal energy of the system
W is the work done on the system
Now I can compress this gas by doing some work on it. If I compress the gas isothermally, there is no change in the internal energy of the system, and the work done on the system will equal the heat out of the system, i.e., Q = W. In this case, the pressure of the system increases due to compressing the gas isothermally.
Question: The energy into the system due to work done on it is equal to the energy out of the system in the form of heat. But the pressure of the system increases, which has the 'capacity to do work'. This increase in pressure seems to store energy, like a compressed spring. Where is this energy, stored as pressure, coming from?
Ref: https://chemistry.stackexchange.com/questions/154236/does-entropy-contribute-work
This increase in pressure seems to store energy, like a compressed spring.
It seems to, but for an ideal gas, it doesn’t (store internal energy, that is); it stores negative entropy in the form of a smaller available volume to explore.
Unlike the physical spring, whose stiffness is enthalpic (with atoms raised to higher energy levels upon deformation), the stiffness of the ideal gas is solely entropic.
Note that in both cases, the Gibbs free energy—which depends on both the enthalpy and the (negative) entropy—increases, meaning we do indeed gain the capacity to extract work.
The following is multiple choice question (with options) to answer.
If a gas in a closed area experiences increases in pressure and decreases in temperatures, what other attribute of the gas will be affected? | [
"temperature",
"volume",
"gravity",
"velocity"
] | B | Both the increase in pressure and the decrease in temperature cause the volume of the gas sample to decrease. Since both changes are relatively small, the volume does not decrease dramatically. |
SciQ | SciQ-6835 | entomology
Title: What is the name of this tiny creature? It looks like a tiny piece of moving cotton? By chance, I saw this tiny insect on my bag a few days ago in Sydney. Am I the first person who has pinpointed this animal?! If not can you please let me know its name? From your image, it looks like it might be a woolly aphid. I just did a bit of cursory research, and it looks like they're often described as floating pieces of fluff, that seem to wander instead of directly heading somewhere. The fluff on their back is actually wax produced as a defense mechanism from predators and the like. I hope this is what you were looking for!
The following is multiple choice question (with options) to answer.
What is the term for the hard covering that protects insects, crustaceans, and spiders? | [
"exoplate",
"endoskeleton",
"endoplate",
"exoskeleton"
] | D | Most animals have an exoskeleton, including insects, spiders, scorpions, horseshoe crabs, centipedes, and crustaceans. Scientists estimate that, of insects alone, there are over 30 million species on our planet. The exoskeleton is a hard covering or shell that provides benefits to the animal, such as protection against damage from predators and from water loss (for land animals); it also provides for the attachments of muscles. As the tough and resistant outer cover of an arthropod, the exoskeleton may be constructed of a tough polymer such as chitin and is often biomineralized with materials such as calcium carbonate. This is fused to the animal’s epidermis. Ingrowths of the exoskeleton, called apodemes, function as attachment sites for muscles, similar to tendons in more advanced animals (Figure 33.3). In order to grow, the animal must first synthesize a new exoskeleton underneath the old one and then shed or molt the original covering. This limits the animal’s ability to grow continually, and may limit the individual’s ability to mature if molting does not occur at the proper time. The thickness of the exoskeleton must be increased significantly to accommodate any increase in weight. It is estimated that a doubling of body size increases body weight by a factor of eight. The increasing thickness of the chitin necessary to support this weight limits most animals with an exoskeleton to a relatively small size. The same principles apply to endoskeletons, but they are more efficient because muscles are attached on the outside, making it easier to compensate for increased mass. |
SciQ | SciQ-6836 | human-biology, respiration
Title: Why does inert gas asphyxiation trigger unconsciousness almost immediately? According to an official safety bulletin from the U.S. Chemical Safety and Hazard Investigation Board:
"Breathing an oxygen deficient atmosphere can have serious and immediate effects, including unconsciousness after only one or two breaths."
Most people can hold their breath for at least 30 seconds and sometimes up to several minutes; clearly, breathing an oxygen-deficient inert gas will affect a person far sooner than simply holding one's breath.
An inert gas like nitrogen is not inherently toxic, so why does breathing a concentrated inert gas cause unconsciousness almost immediately? Does it replace the oxygen that would otherwise remain in the body while holding one's breath? One reason you can hold your breath for 30 or more seconds is that you are not denying your body oxygen during that time. Wikipedia says:
After exhaling, adult human lungs still contain 2.5–3 L of air, their functional residual capacity or FRC. On inhalation, only about 350 mL of new, warm, moistened atmospheric air is brought in and is well mixed with the FRC. Consequently, the gas composition of the FRC changes very little during the breathing cycle.
The following is multiple choice question (with options) to answer.
What gas is expired out of the body during exhalation? | [
"carbon monoxide",
"carbon dioxide",
"oxygen",
"hydrogen"
] | B | Introduction Breathing is an involuntary event. How often a breath is taken and how much air is inhaled or exhaled are tightly regulated by the respiratory center in the brain. Humans, when they aren’t exerting themselves, breathe approximately 15 times per minute on average. Canines, like the dog in Figure 39.1, have a respiratory rate of about 15–30 breaths per minute. With every inhalation, air fills the lungs, and with every exhalation, air rushes back out. That air is doing more than just inflating and deflating the lungs in the chest cavity. The air contains oxygen that crosses the lung tissue, enters the bloodstream, and travels to organs and tissues. Oxygen (O2) enters the cells where it is used for metabolic reactions that produce ATP, a high-energy compound. At the same time, these reactions release carbon dioxide (CO2) as a by-product. CO2 is toxic and must be eliminated. Carbon dioxide exits the cells, enters the bloodstream, travels back to the lungs, and is expired out of the body during exhalation. |
SciQ | SciQ-6837 | botany
All
142
45.01± 5.23
2306
45.64± 4.95
18 124
46.85± 3.98
3754
47.88± 3.49
For an algal estimate, see here:
Carbon is obtained from the post-carbon-capture flow and compressed to 1 MPa for transport and supply to the growth volume (requiring 248 kJ/kg of gas). Carbon uptake efficiency is 79%. The algal biomass productivity is 82.5 t/ha-yr (23.8 g/m2-d) with an elemental composition consisting of 48% carbon, 6.3% nitrogen, and 0.6% phosphorus (Huntley et al., 2015).
The following is multiple choice question (with options) to answer.
Through this process, algae provide glucose for the ecosystem? | [
"photosynthesis",
"glycolysis",
"GLUCOPHAGE",
"spermatogenesis"
] | A | In a marine ecosystem, algae are the producers. Through photosynthesis, they provide glucose for the ecosystem. So, can too much algae be a bad thing? Eutrophication is an over-enrichment of chemical nutrients in a body of water. Usually these nutrients are the nitrogen and phosphorous found in fertilizers. Run-off from lawns or farms can wash fertilizers into rivers or coastal waters. |
SciQ | SciQ-6838 | human-biology, hair
In most people this receptor functions as intended, and melanocytes in the skin produce varying degrees of brown-black eumelanin (the extent of which depending on one's ethnic background) while pheomelanin is switched on in the few key areas listed above. When both copies of the MC1R gene inherited from each of your parents are disfunctional, this switching mechanism no longer works and your melanocytes will produce primarily pheomelanin ubiquitously across your body. This is what we know as 'redheads'.
What isn't immediately obvious is that red-haired individuals are not unique in just the aspect of their hair. Their whole body presents with a deficiency in eumelanin and as such they also carry a pale/rosy complexion as well as an inability to tan and a propensity to sunburn easily. This is a consequences of the fact that eumelanin is our primary defense against UV radiation.
While melanocytes in the skin and eyes are responsible for the production of melanin, the melanin in one's hair gets there as a result of a handoff between melanocytes and the keratin producing keratinocytes. Melanin within melanocytes is produced and stored within organelles known as melanosomes and, through a complex formed by the 3 genes MYO5A, RAB27A, and MLPH, the transfer of these melanosomes through the tendrils of the melanocytes to the keratinocytes is facilitated. Defects in any of these 3 genes can result in a condition known as Griscelli syndrome (types 1, 2, and 3, respectively) where the transfer of melanin from melanocytes to keratinocytes is impaired.
The following is multiple choice question (with options) to answer.
What determines your hair color trait? | [
"cells",
"genes",
"chromosomes",
"Heredity"
] | B | There are variations in the traits of a population. For example, there are lots of variations in the color of human hair. Hair can be blonde, brown, black, or even red. Hair color is a trait determined by genes. |
SciQ | SciQ-6839 | 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.
What layer of skin is directly under the epidermis? | [
"hypodermis",
"sweat glands",
"the dermis",
"the aponeurosis"
] | C | The dermis is the layer of skin directly under the epidermis. It is made of a tough connective tissue. The dermis contains hair follicles, sweat glands, oil glands, and blood vessels ( Figure above ). It also holds many nerve endings that give you your sense of touch, pressure, heat, and pain. |
SciQ | SciQ-6840 | newtonian-mechanics, acceleration, friction
Title: Why maximum acceleration a man can get on walking along a rough surface is $μ$g? Suppose a Man is running on a road which is a rough surface with friction coefficient $μ$. Why will the maximum acceleration of man which he can get is $μ$? Why not from himself by internal body mechanism he cant get a max acceleration greater than $μg$ ? [My thoughts if he is running and is not slipping with respect to ground then the FBD of man will always have friction as a force which can provide him acceleration and that cant be maximum than the limiting friction value which is $μ_s mg$, hence max acc is $μg$? ] [If he was running with slipping then he might have greater accelration due to his body ?] The only external force acting forward on the man is the friction force by the ground which is equal to and opposite to the force the man exerts backwards on the ground per Newton’s third law. The maximum possible static friction force before slipping occurs is $\mu_{s} mg$. Where $\mu_s$ is the coefficient of static friction. That equals the maximum acceleration of the man or $\mu_{s} mg=ma$ and $a=\mu_{s} g$.
In effect, the external static friction force does positive work on the man since its direction is the same as the directly of the man’s motion. More importantly, unlike kinetic friction, static friction is not dissipative, i.e., it does not result in energy loss due to heating.
But once the maximum possible static friction force is reached, friction transitions from static to kinetic and slipping occurs where $\mu_k$ is now the coefficient of kinetic friction and in general $\mu_{k}<\mu_s$. Now the kinetic friction force is constant and opposes the sliding motion between the foot and ground. In effect kinetic friction does negative work since its force is opposite the direction of the sliding motion between the foot and the ground. The negative work done by friction takes energy away from the work done pushing back on the ground on for a net work of zero and the energy dissipated as heat (which does not occur with static friction). The end result after slipping occurs is the man continues, but at constant velocity.
The following is multiple choice question (with options) to answer.
What is caused by bodies sliding over rough surfaces? | [
"vibration",
"heat loss",
"friction",
"tension"
] | C | Friction is caused by bodies sliding over rough surfaces. |
SciQ | SciQ-6841 | optics, visible-light, electromagnetic-radiation
... I don't feel it's in any way meaningful ...
is an intrinsic feature of the problem, because to be able to express the visible range as a fraction of the EM spectrum, you need a measure on the latter, and there is no natural way to do this.
The closest you can get is to assign a measure that is uniform in logarithmic scale, with long- and short-wavelength cutoffs at the size of the universe and at the Planck energy, but that essentially implies that there is an equal amount of interesting phenomena happening at photon energies vastly larger than anything than we've ever had access to, as in the ranges where we do have access, as well as a large almost-bottomless well of wavelengths that don't even fit inside our own galaxy. Physics, of course, doesn't care ─ but we, as humans, do.
All of which is to say: there is no unique answer that comes from physics. If you want an answer that's relevant to humans, then you should base your measure on cutoffs which come from human considerations. I would personally go with a logarithmically uniform measure with cutoffs at about ${\sim}10\:\rm TeV$ (about the highest energies we can reach in particle accelerators, hence about the highest gamma photon energies we can control) and at about ${\sim}1:\rm Hz$ (from the ELF radio band). But, again, that's ultimately a subjective choice.
The following is multiple choice question (with options) to answer.
The electromagnetic spectrum represents the full range of frequency of what type of wave? | [
"mechanical",
"transverse wave",
"seismic",
"electromagnetic"
] | D | Electromagnetic waves vary in their frequencies and wavelengths, and waves with higher frequencies have greater energy. The electromagnetic spectrum represents the full range of frequencies of electromagnetic waves. |
SciQ | SciQ-6842 | sequence-homology
NP_418577.1 63 CGSCGMMVNNVPKLACKTFLR--DYTDGMKVEALANFPIERDLVVDMTHF 110
|||..|.:|...:|||||.:: |.:..:.|||:...|:|:||:|||..|
WP_036312822. 81 CGSDAMRINGRNRLACKTLIKDLDISKPIYVEAIKGLPLEKDLIVDMDPF 130
NP_418577.1 111 IESLEAIKPYIIGNSRTADQGTNIQTPAQMAKYHQFSGCINCGLCYAACP 160
.||...::|::...|.........|:....|.|...:.||.|..|.::||
WP_036312822. 131 FESFRDVQPFLQPKSAPEPGKERFQSIKDRAVYDDTTKCILCAACTSSCP 180
NP_418577.1 161 QFGLNPEFIGPAAITLAHRYNEDSRDHGKKERMAQLNSQNGVWSCTFVGY 210
.|..:.::.|||||..|||:..||||.....|:..||.:.|||.|.....
WP_036312822. 181 VFWTDGQYFGPAAIVNAHRFIFDSRDDAADVRLDILNDKEGVWRCRTTFN 230
NP_418577.1 211 CSEVCPKHVDPAAAIQQGK 229
|:|.||:.::...||.:.|
WP_036312822. 231 CTEACPRGIEITKAIAEVK 249
The following is multiple choice question (with options) to answer.
Distinguishing between homology and analogy is critical in reconstructing what? | [
"phylogenies",
"proteases",
"phylums",
"residues"
] | A | |
SciQ | SciQ-6843 | human-biology, digestive-system, immune-system, microbiome
All of these immune cells also respond to diffused chemical signals called cytokines. These molecules are secreted by some cells and are received by receptors on the host cells. Sometimes the secretion is by another immune cell, sometimes it is from a non-immune system host cell, and sometimes these molecules can be secreted by the bacteria, fungi, or worms themselves.
Depending on the chemical signals that are secreted, and how the cells are interacting at the time of the message, and which cells are receiving the message, will determine the response to the message. It is contextual. Think of the phrase "You're killing me." If someone says it, while laughing, to a good friend who is telling jokes, it means one thing. If it is screamed as someone is being choked by an attacker, it means something very different.
To summarize, the immune cells are surveilling the environment and trying to pick up what is friend and what is foe and they try to respond accordingly.
Over time and coevolution, our microbiomes have developed ways of communicating with our immune system to let it know that these microbes do not mean any harm. They are able to "train" the immune cells using chemical signaling to temper the immune systems response to them (15), and this is how they are able to coexist within our body and with an immune system that is constantly on seek an destroy missions. Also because of the mucus, our microbiome usually isn't in direct contact with our cells, so it is a different kind of interaction than if an infecting pathogen were to breech the barriers and gain access to sterile areas where no bacteria or fungi should be found, and as a result, the immune system reacts differently.
The following is multiple choice question (with options) to answer.
What do many mollusks secrete for their protection? | [
"calcareous shell",
"sedimentation shell",
"microscopic shell",
"mucus"
] | A | 15.4 Mollusks and Annelids The phylum Mollusca is a large, mainly marine group of invertebrates. Mollusks show a variety of morphologies. Many mollusks secrete a calcareous shell for protection, but in other species, the shell is reduced or absent. Mollusks are protostomes. The dorsal epidermis in mollusks is modified to form the mantle, which encloses the mantle cavity and visceral organs. This cavity is distinct from the coelomic cavity, which the adult animal retains, surrounding the heart. Respiration is facilitated by gills known as ctenidia. A chitinous scraper called the radula is present in most mollusks. Mollusks are mostly dioecious and are divided into seven classes. The phylum Annelida includes worm-like, segmented animals. Segmentation is both external and internal, which is called metamerism. Annelids are protostomes. The presence of chitinous hairs called chaetae is characteristic of most members. These animals have well-developed nervous and digestive systems. Polychaete annelids have parapodia that participate in locomotion and respiration. Suckers are seen in the order Hirudinea. Breeding systems include separate sexes and hermaphroditism. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.