source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-3344 | pharmacology, toxicology, vitamins
Now the effects. Indeed, hair loss is one of the symptoms of heavy vitamin A-deficiency, and logically, that symptom can be cured with vitamin A. That does not mean that more results in more. While retinoids are important therapeutic agents for the management of many skin diseases, notably acne vulgaris, psoriasis, ichthyosis, and palmoplantar keratoderma, there exists something like retinoid-induced effluvium which is a side effect of such medication with tretinoin (ATRA).
The following is multiple choice question (with options) to answer.
Acne results from a blockage of sebaceous glands by what? | [
"fat",
"sebum",
"progesterone",
"mucous"
] | B | Chapter 5 1 The epidermis provides protection, the dermis provides support and flexibility, and the hypodermis (fat layer) provides insulation and padding. 3 Figure 5.6 These cells have desmosomes, which give the cells their spiny appearance. 5 D 7 C 9 C 11 D 13 B 15 A 17 C 19 C 21 C 23 B 25 The pigment melanin, produced by melanocytes, is primarily responsible for skin color. Melanin comes in different shades of brown and black. Individuals with darker skin have darker, more abundant melanin, whereas fair-skinned individuals have a lighter shade of skin and less melanin. Exposure to UV irradiation stimulates the melanocytes to produce and secrete more melanin. 27 Eccrine sweat glands are all over the body, especially the forehead and palms of the hand. They release a watery sweat, mixed with some metabolic waste and antibodies. Apocrine glands are associated with hair follicles. They are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis. They release a thicker sweat that is often decomposed by bacteria on the skin, resulting in an unpleasant odor. 29 Sweating cools the body when it becomes warm. When the body temperature rises, such as when exercising on a hot day, the dermal blood vessels dilate, and the sweat glands begin to secrete more sweat. The evaporation of the sweat from the surface of the skin cools the body by dissipating heat. 31 Acne results from a blockage of sebaceous glands by sebum. The blockage causes blackheads to form, which are susceptible to infection. The infected tissue then becomes red and inflamed. Teenagers experience this at high rates because the sebaceous glands become active during puberty. Hormones that are especially active during puberty stimulate the release of sebum, leading in many cases to blockages. |
SciQ | SciQ-3345 | proteins, gene
Title: One Gene and many proteins Imagine a gene with $n$ exons and $m$ introns. How many proteins are possible from that gene? Would all the proteins be isoforms? I might be wrong, but aren't numbers $n$ and $m$ are connected as $n=m+1$?
Answer seems to be combinatorial: how many combinations of $n$ objects can be assembled under certain restrictions? Namely, how many isoforms certain gene can have.
Restrictions include: how many exon-intron junctions on codon (or precisely between codons), how many exons are actually contain protein-coding sequence of mRNA (some exons are coding untranslated region, 3'- or 5'-UTR, for example), how certain gene processes alternative splicing.
So, as you can see, answer will highly depend on sequence of given gene. As far as I know, maximum number of isoforms is limited by 5, even though there are genes with hundreds of exons.
The following is multiple choice question (with options) to answer.
Just as millions of different words are spelled with our 26-letter english alphabet, millions of different proteins are made with the 20 common what? | [
"peptides",
"amino acids",
"mutation acids",
"enzymes"
] | B | Just as millions of different words are spelled with our 26-letter English alphabet, millions of different proteins are made with the 20 common amino acids. However, just as the English alphabet can be used to write gibberish, amino acids can be put together in the wrong sequence to produce nonfunctional proteins. Although the correct sequence is ordinarily of utmost importance, it is not always absolutely required. Just as you can sometimes make sense of incorrectly spelled English words, a protein with a small percentage of “incorrect” amino acids may continue to function. However, it rarely functions as well as a protein having the correct sequence. There are also instances in which seemingly minor errors of sequence have disastrous effects. For example, in some people, every molecule of hemoglobin (a protein in the blood that transports oxygen) has a single incorrect amino acid unit out of about 300 (a single valine replaces a glutamic acid). That “minor” error is responsible for sickle cell anemia, an inherited condition that usually is fatal. |
SciQ | SciQ-3346 | cellular-respiration, fermentation
Fermentation: An ATP-generating process in which organic compounds act as both donors and acceptors of electrons. Fermentation can take place in the absence of O2. Discovered by Louis Pasteur, who described fermentation as “la vie sans l’air” (“life without air”).
So the biochemical lawyers have produced a definition that very few readers will be able to take in at first sight. What is this business about electron donors and acceptors? Well what it means in relation to the fermentation process in which lactic acid is produced (note my legalistic choice of words) is that one organic compound is reduced (glyceraldehyde 3-phosphate) — by NAD+ — and one organic compound is oxidized (pyruvate) — by NADH. And as the production of ATP is included in the definition this means that Berg et al. include glycolysis in this definition of fermentation.
…except that on the same page there is the following statement:
pyruvate is converted, or fermented, into lactic acid in lactic acid fermentation or into ethanol in alcoholic fermentation
So here it seems that the word is being used for the conversion of pyruvate to lactate or ethanol, i.e. it excludes glycolysis.
Pasteur managed to talk about fermentation without being aware of glycolysis or ATP, and it is clear to me that you can write whatever carefully phrased definitions you like, but people are going to continue to use venerable terms like fermentation in whatever way seems natual to them.
The following is multiple choice question (with options) to answer.
Anaerobic respiration takes place without what? | [
"oxygen",
"nitrogen",
"carbon",
"movement"
] | A | Aerobic respiration , which takes place in the presence of oxygen, evolved after oxygen was added to Earth’s atmosphere. This type of respiration is useful today because the atmosphere is now 21% oxygen. However, some anaerobic organisms that evolved before the atmosphere contained oxygen have survived to the present. Therefore, anaerobic respiration , which takes place without oxygen, must also have advantages. |
SciQ | SciQ-3347 | star, planet, exoplanet, habitable-zone
Title: Detecting habitable planets From my understanding we detect planets by measuring dips in light intensity from the star the habitable planet is orbiting when it passes by it.
There are 2 things I don’t understand about this method:
Planets in a solar system tend to orbit their star in one disc like plane. Can we only detect planets if this plane is in-alignment with our sensors here on earth/ space. I assume if someone looked at our sun from the ‘bottom’ they would never see a planet cross it. If so this would exclude a big portion of the stars we are looking at?
Our orbit is 1 year. I assume the orbits of habitable plants can vary and having a short/ close to 1 year orbit is not a criteria for habitability. Even so we have to measure 1 dip every year or 10. How can we tell that this a planet with a regular yearly orbit or just anything passing between the star and us. So maybe a better question to ask for number 2 is what can we find out from these dips?
Yes and yes. Transit detection is only effective for that (small) fraction of planets that pass between the star and our line of sight. Most planets will go undetected by this method.
Also correct. The detection of multiple transits is required to find planets. Even then the dips can be caused by other things (e.g. grazing eclipse binary star systems). This means to find Earthlike planets in Earthlike orbits would require years of observation. But habitable zones around less luminous stars are closer-in and have shorter orbital periods. It is these stars that planet-hunting missions like TESS are focused on.
The following is multiple choice question (with options) to answer.
Which other planet in the solar system is the easiest to observe from earth? | [
"Mercury",
"mars",
"Jupiter",
"Pluto"
] | B | Mars is the easiest planet to observe. As a result, it has been studied more than any other planet besides Earth. People can stand on Earth and observe the planet through a telescope. We have also sent many space probes to Mars. In April 2011, there were three scientific satellites in orbit around Mars. The rover, Opportunity, was still moving around on the surface. No humans have ever set foot on Mars. NASA and the European Space Agency have plans to send people to Mars. The goal is to do it sometime between 2030 and 2040. The expense and danger of these missions are phenomenal. |
SciQ | SciQ-3348 | 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 in the inside of your mouth and nose instead of skin? | [
"mucous membranes",
"scales",
"gums",
"cuticle layer"
] | A | The mouth and nose are not lined with skin. Instead, they are lined with mucous membranes . Other organs that are exposed to the outside world, including the lungs and stomach, are also lined with mucous membranes. Mucous membranes are not tough like skin, but they have other defenses. |
SciQ | SciQ-3349 | botany, ecology, energy
Title: Why do plants create enough energy for the entire ecosystem? In my environmental class, we were recently learning about the $10\%$ law that basically says only $10\%$ of the energy goes from one trophic level to the next.
This got me thinking about why energy flows from one level to the next. Specifically, why do plants create enough energy for the entire ecosystem? Wouldn't they do fine without us, and wouldn't that save them the work of creating all that excess energy? Plants collect energy for themselves via photosynthesis, not for others.
It is used for it's own growth and survival.
It's energy is then redistributed to other organisms when either the plant dies and decomposes or when it is consumed. Many organism cannot collect their energy like plants do, and thus must feed on organisms (like plants) that are able to collect and store energy. This is in many cases detrimental to the plant (it should be intuitive why being eaten might be bad), and many, many plants do have traits to discourage other organisms from eating them (plants with toxins, thorns, etc.).
The following is multiple choice question (with options) to answer.
While matter is recycled, ecosystems need a constant input of what? | [
"light",
"food",
"heating",
"energy"
] | D | In all biomes, ecosystems need a constant input of energy. Matter, on the other hand, is constantly recycled in ecosystems. |
SciQ | SciQ-3350 | quantum-gravity, physical-constants
Title: What is the smallest existing thing in theory and law? What is the smallest existing thing in theory and law?
"What is the smallest existing thing in theory and law?"
The Merriam Webster Dictionary defines a "thing" as:
: an object or entity not precisely designated or capable of being
designated
a: an inanimate object distinguished from a living being
b: a separate and distinct individual quality, fact, idea, or usually
entity
c: the concrete entity as distinguished from
...
A Photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). Mass: 0 < 1×10−18 eV/c^2.
The photon has zero rest mass and always moves at the speed of light within a vacuum. Since the Photon is a Point Particle and has a size of zero you might say it's not a thing, nothing; that leaves us with:
The smallest real thing is the Neutrino. Mass: ≤ 0.120 eV/c^2.
The smallest theoretical thing is the Planck Particle. Radius: 5.72947×10−35 m, Mass: 3.85763×10−8 kg.
The following is multiple choice question (with options) to answer.
What is term for the smallest particle of an element that still has the properties of said element? | [
"nucleus",
"atom",
"proton",
"molecule"
] | B | Atoms are the building blocks of matter. They are the smallest particles of an element that still have the element’s properties. Elements, in turn, are pure substances—such as nickel, hydrogen, and helium—that make up all kinds of matter. All the atoms of a given element are identical in that they have the same number of protons, one of the building blocks of atoms (see below). They are also different from the atoms of all other elements, as atoms of different elements have different number of protons. For an entertaining introduction to atoms by Bill Nye the Science Guy, watch the video at this URL:. |
SciQ | SciQ-3351 | biochemistry, transition-metals, oxidation-state, proteins
15. Goddard, W. A., III; Olafson, B. D. Ozone Model for Bonding of an O2 to Heme in Oxyhemoglobin. Proc. Natl. Acad. Sci. 1975, 72 (6), 2335–2339. DOI: http://10.1073/pnas.72.6.2335.
16. Chen, H.; Ikeda-Saito, M.; Shaik, S. Nature of the Fe−O2 Bonding in Oxy-Myoglobin: Effect of the Protein. J. Am. Chem. Soc. 2008, 130 (44), 14778–14790. DOI: 10.1021/ja805434m.
17. Grinstaff, M. W.; Hill, M. G.; Labinger, J. A.; Gray, H. B. Mechanism of catalytic oxygenation of alkanes by halogenated iron porphyrins. Science 1994, 264 (5163), 1311–1313. DOI: 10.1126/science.8191283.
18. Wilson, S. A.; Kroll, T.; Decreau, R. A.; Hocking, R. K.; Lundberg, M.; Hedman, B.; Hodgson, K. O.; Solomon, E. I. Iron L-Edge X-ray Absorption Spectroscopy of Oxy-Picket Fence Porphyrin: Experimental Insight into Fe–O2 Bonding. J. Am. Chem. Soc. 2013, 135 (3), 1124–1136. DOI: 10.1021/ja3103583
19. Wilson, S. A.; Green, E.; Mathews, I. I.; Benfatto, M.; Hodgson, K. O.; Hedman, B.; Sarangi, R. X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin. Proc. Natl. Acad. Sci. 2013, 110 (41), 16333–16338. DOI: 10.1073/pnas.1315734110.
The following is multiple choice question (with options) to answer.
What is the protein that carries iron that binds with oxygen in red blood cells? | [
"potassium",
"insulin",
"keratin",
"hemoglobin"
] | D | The trillions of red blood cells in blood plasma carry oxygen. Red blood cells contain hemoglobin , a protein with iron that binds with oxygen. Red blood cells are made in the marrow of long bones, rib bones, the skull, and the vertebrae. These cells survive for about 120 days, and then they are destroyed. Mature red blood cells lack a nucleus and other organelles, allowing for more hemoglobin, and therefore more oxygen to be carried by each cell. |
SciQ | SciQ-3352 | symmetry, atoms
Title: Is hydrogen the same everywhere? Silly thought. Feel free to shoot it down
Does a hydrogen atom undergo any kind of change subject to it's environment?
If one were to study a hydrogen atom on the surface of Mercury, another above Earth, and a third in interstellar space - would they exhibit any difference/s? This is quite far from a silly thought although this is not apparent at first sight. Apart from a couple of details which are well understood and have firm physics behind them - such as the fact that deuterium and tritium exist in some proportion and the hyperfine-structure distinction between ortho- and parahydrogen, as far as we can tell all hydrogen atoms are exactly the same. This is in fact the case for all atoms and molecules: all iron atoms are exactly replaceable (so long as you take the right isotope) and nitrogen molecules are all the same (so long as you take them in the correct electronic, nuclear and spin states), and so on.
This is one of the most profound symmetries in nature and it holds irrespective of geographical / astronomical position, chemical history, temperature, and so on. How can we tell? Well, the very fact that we can do chemistry with atoms is why - the basic tenet is that the world is made of a finite set of "blocks" and that combinations of them make the interesting materials around us. The success of chemistry as a discipline means that there's something to that basic tenet.
How can we tell that atoms in places we haven't been are the same as here? Of course, our evidence for that is not as strong, but it's built on the fact that astrophysics works just using physics of different kinds we can see experimentally here on Earth. We can do spectral analysis of the solar corona, for example, and if we see energy levels slightly displaced then we can explain that as Doppler shifts or magnetic fields that let us explore a richer and (as far as we can tell) fully consistent physical picture. We can do chemistry on the atmospheres of other planets and, though it's rather hard, come up with consistent chemical explanations for all our observations. We can link the nuclear physics we observe in accelerators and reactors to explain our observations of our Sun and other stars and see that they match what we do here.
The following is multiple choice question (with options) to answer.
What branch of science is based on the modern atomic theory, which states that all matter is composed of atoms? | [
"psychology",
"physics",
"chemistry",
"biology"
] | C | Chemistry is based on the modern atomic theory, which states that all matter is composed of atoms. |
SciQ | SciQ-3353 | electrophysiology, ichthyology, bioenergetics, energy, limnology
Containment
They also, as an aside, have to be careful to not electrocute themselves and stop their own hearts, and they have to take care not to electrocute each other. The father will keep his fry in his mouth, and signal them as to where they should go to be safe, when he performs a shock.
For those reasons, if you did use electric eels for power, you'd have to be careful how you contained them, so they had enough space to not electrocute themselves or each other.
The following is multiple choice question (with options) to answer.
Why do sharks sense low levels of electricity? | [
"to locate mates",
"to sleep",
"to reproduce",
"to locate prey"
] | D | Fish also have a centralized nervous system with a brain. Fish brains are small compared with the brains of other vertebrates, but they are large and complex compared with the brains of invertebrates. Fish also have highly developed sense organs that allow them to see, hear, feel, smell, and taste. Sharks and some other fish can even sense the very low levels of electricity emitted by other animals. This helps them locate prey. |
SciQ | SciQ-3354 | photosynthesis
Title: Photosystem I and the ETC In the light reactions of photosynthesis, Photosystem I receives electrons from the ETC after Photosystem II sends them to the ETC. Then, when Photosystem I receives light, the electron becomes excited and passes the electron back to the ETC. This leads me to my question: In the following question, are both $B$ and $E$ correct?
Which of the following are directly associated with photosystem I?
$A)$ harvesting of light energy by ATP
$B)$ receiving electrons from the thylakoid membrane electron transport chain
$C)$ generation of molecular oxygen
$D)$ extraction of hydrogen electrons from the splitting of water
$E)$ passing electrons to the thylakoid membrane electron transport chain It appears the author of the question is trying to use "thylakoid electron transport chain" in an overly specific way. The chain from which PS I receives electrons has far more components and is different from the shorter chain to which PS I passes its electrons. But according to my copy of Biology, Campbell & Reece 7th edition, both are called "electron transport chains" and both reside in, or on, the thylakoid membrane. Perhaps the "directly" in the question refers to the fact that PS I's electron is first captured by a "primary receptor" before being passed to ferredixon, the first member of the chain to which PS I passes electrons. But, again according to Campbell, this primary acceptor is considered part of the photosystem.
I used to teach this stuff. I'd toss out the question.
The following is multiple choice question (with options) to answer.
What membrane is populated by two types of photosystems that cooperate in the light reactions of photosynthesis? | [
"thylakoid",
"chloroplasts",
"subcutaneous",
"choroid"
] | A | |
SciQ | SciQ-3355 | ecology
I have tried to find explanatory texts both in this and other books without any success so my question is how's this balanced state achieved in both types of successions (the answer is hinted in the first paragraph which I don't quite understand)?
Related to my last post. The author is saying that 1) Mature ecosystems tend to have a balance between production (=P) and use (=R, respiration) of biomass. This is actually tautological because the author would probably define a mature ecosystem as one where this is true (P=R).
If it starts out P > R, the autotrophs are dominant: more biomass is being produced than used up. It is possible, for a time, that P will increase as, for example, plants grow more leaves, but R is growing too, and there is an eventual limit on P, which at maximum depends on the light available to the ecosystem. As biomass grows, so does the amount of biomass to potentially decay, so eventually R will always catch up to P, until there is balance.
If it starts out P < R, that means you are using up biomass faster than you are creating it. This case is even simpler: you will gradually run out of biomass, and R will decrease.
In either case, when the author is talking about P = R, this is going to be in relative terms; there might still be variations between them, for example seasonal variation, but on average over years or decades you would expect P = R in a mature, stable ecosystem.
The following is multiple choice question (with options) to answer.
At what point can nutrients enter or exit an ecosystem? | [
"Longest Point",
"any point",
"Largest Population Point",
"Hottest Point"
] | B | Nutrients can enter or exit an ecosystem at any point and can cycle around the planet. |
SciQ | SciQ-3356 | human-biology, molecular-biology, human-physiology, immune-system, history
Title: Which landmark paper first described the differentiation of T-cells? T-cells are distinguished from B cells in part by their locus of differentiation/maturation (thymus). This is textbook knowledge, but I was wondering which particular person or people were responsible for making this discovery. I'd appreciate any links to their original papers/works. Thanks a lot! This paper appears to be a history of the discovery of B/T differentiation and the role of the thymus. I believe that you should find a number of important references therein.
It describes specifically a series of publications in the 1950s and 1960s that may be relevant (section "Identification of T and B cells"), such as this one by Gowans.
The following is multiple choice question (with options) to answer.
B cells and t cells are examples of what type of cells? | [
"cancer cells",
"skin cells",
"white blood cells",
"heart cells"
] | C | There are two different types of specific immune responses. One type involves B cells. The other type involves T cells. Recall that B cells and T cells are types of white blood cells that are key in the immune response. Whereas the immune system's first and second line of defense are more generalized or non-specific, the immune response is specific. It can be described as a specific response to a specific pathogen, meaning it uses methods to target just one pathogen at a time. These methods involve B and T cells. |
SciQ | SciQ-3357 | rna, transcription, mrna
And don't worry, Gilson pipettes are pretty good. I have used now more or less all brands on the market and I still prefer them. They only need some service from time to time.
The following is multiple choice question (with options) to answer.
There are three different types of rna. all three types are needed to make what? | [
"lipids",
"proteins",
"Blood",
"acids"
] | B | There are three different types of RNA. All three types are needed to make proteins. |
SciQ | SciQ-3358 | zoology, ecology, species-distribution, migration
Title: How do animals end up in remote areas? I was thinking specifically about random marshy water holes on farmers fields. It seems that you can visit just about any one of these and you will find frogs if you look hard enough.
They usually don't seem to be connected to each other. If it were any other land animal I would figure they walk from one spot to another, but in the case of frogs, I don't imagine their range is very vast. But often these marshy spots can be separated by fairly large distances to a frog.
So this brings me to my question: how do each of these spots end up with frogs in them? I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it? This question pertains to organism dispersal, which is a very active field of study with relation to it's impact on conservation efforts. Much of what I will say below has been covered in this wiki.
Definition: From the Wiki
Technically, dispersal is defined as any movement that has the
potential to lead to gene flow.
It can be broadly classified into two categories:
Density dependent dispersal
Density independent dispersal
The question of frogs and fishes both refer to Density independent dispersal, while an example of density independent dispersal can be the competition for habitat space between big cats and humans (this is a WWF pdf)
From the wiki:
Density-independent dispersal
Organisms have evolved adaptations for dispersal that take advantage
of various forms of kinetic energy occurring naturally in the
environment. This is referred to as density independent or passive
dispersal and operates on many groups of organisms (some
invertebrates, fish, insects and sessile organisms such as plants)
that depend on animal vectors, wind, gravity or current for dispersal.
Density-dependent dispersal
Density dependent or active dispersal for many animals largely depends
on factors such as local population size, resource competition,
habitat quality, and habitat size.
Currently, some studies suggest the same.
This study in particular studied the movement and habitat occupancy patterns within ephemeral and permanent water bodies in response to flooding. They found that during flooding these frogs moved out to flooded ephemeral water bodies and later on moved back again to the permanent ones.
Other suggested readings for those highly interested in the subject may include this (a phd thesis) and this (a project report)
The following is multiple choice question (with options) to answer.
Niche and habitat are concepts related to what broader term? | [
"community",
"ecosystem",
"biome",
"population"
] | B | 7. Compare and contrast the ecosystem concepts of niche and habitat. |
SciQ | SciQ-3359 | electromagnetism, charge
You may ask why it is then so contrary to speak that two opposite charges cancel each other. No objection. All I want you to remember is that it is the net charge that is zero. Individually the charges are not zero. Take the example of an ionic crystal, say $NaCl$, where $Na^+$ and Cl^-$ ions are tightly held together by electrostatic attraction. Both ions have equal and opposite charges. If the interaction between the two lead to the individual destruction of charges (losing property as a charge), then how the solid continues to be so brittle. There is always interaction between the two ions. This means the interaction between the two charges do not cause the charges to lose their charge. It's the effective charge that is zero. We then speak about a system, not about individual charges.
The following is multiple choice question (with options) to answer.
What do opposite charges do to one another? | [
"attract",
"weaken",
"repel",
"strengthen"
] | A | Opposite charges attract, and like charges repel. |
SciQ | SciQ-3360 | ocean, thermohaline-circulation, salinity
Title: Thermohaline Circulation in the Oceans I'm slightly confused by how thermohaline circulation works in the Earth's oceans. Is it different for surface water as opposed to deep water? I thought that warm water from the equator is transported to the poles, cools down, and then returns to lower latitudes. Is my thinking incorrect? Isn't water denser near the equator because of higher salinity? How does this impact the ocean circulation?
Thanks! Salinity and temperature both affects the density of sea water. When water with a fixed salinity cools down, it becomes heavier and sinks. In the same way, when vapor or ice removes water from sea water, the remains is more saline and heavier.
Thermohaline circulation can work as you describe. Surface water in the tropics is saline, due to evaporation, but warm due to high temperature in the atmosphere and therefor low density. As it reach colder climate (less solar energy per area), it cools down and the high salinity makes it sink. Surface water in polar regions also get heavier as ice is formed of water and leave the salt behind in the sea.
This is very simplified model, you can read more on the topic here and here.
The following is multiple choice question (with options) to answer.
What is the name for the sinking of the dense, salty seawater in cold climates? | [
"downwelling",
"jet stream",
"tidal activity",
"cyclones"
] | A | Water becomes more dense when it is colder and when it has more salt. In the North Atlantic Ocean, cold winds chill the water at the surface. Sea ice grows in this cold water, but ice is created from fresh water. The salt is left behind in the seawater. This cold, salty water is very dense, so it sinks to the bottom of the North Atlantic. Downwelling can take place in other places where surface water becomes very dense (see Figure below ). |
SciQ | SciQ-3361 | thermodynamics, ideal-gas, heat-engine, heat-conduction
Title: Confusion in first law of thermodynamics Our teacher while explaining first law of thermodynamics showed us an example of a piston inside a chamber. He said when heat is applied the particles move, i.e the kinetic energy increases. Due to this velocity the molecules put some pressure on piston. Due to which the piston moves.
He said that some part of the energy supplied (heat) goes in increasing kinetic energy and other in doing work due to which the piston moves.
$$ dQ= dU + dW $$
My doubt is that how is the heat affecting the pressure applied directly. The heat affects the velocity of gas molecule which then increases the pressure on piston due to which it moves.
He also said that if there was no piston then the total heat will go into increase in kinetic energy. Which doesn't make sense how does the heat or molecules know when to take some energy when when to not?
But how is heat directly effecting the work done? I believe that heat goes fully in to vibrating/increasing kinetic energy of particle. If no heat was entering or escaping from the container, and it had fixed walls, we could assume that the energy of the molecules, ($\frac{1}{2} mv^2 = \frac{p^2}{2m}$) after each bounce on the walls was conserved, and temperature was constant.
If there is an expanding piston, and doing work outside, the energy comes from the molecules that lose some of its own after bouncing on the piston surface.
If there was no heat input the gas cooled. Depending on the amount of heat flow, it can expand the piston and increase the gas temperature.
The following is multiple choice question (with options) to answer.
When gas particles heat up and gain energy, what do they do? | [
"move faster",
"move slower",
"go up",
"stop"
] | A | When gas particles heat up and gain energy, they move faster. This increases their collisions with each other and their container, causing greater pressure. |
SciQ | SciQ-3362 | biochemistry, cell-biology, metabolism, photosynthesis
Title: How are ions 'pumped' across a membrane during electron transport? A number of sites (including this one) that provide descriptions of photosynthesis state that high energy electrons 'pump' ions across a membrane. What is the actual 'pumping' mechanism? I've looked at Wikipedia and at a number of YouTube lectures/tutorials but so far have only found statements as to the where and when but not the how of this important process. Short answer:
Electrons flow through membranes by floating through kind of channels made out of iron-sulfur clusters.
Long answer:
Let's take a look at the electron transport chain in the inner mitochodrial membrane. There is a proton gradient across the membrane building up a potential difference by pumping protons across the membrane as electeons flow through the respiratory chain. They (electrons) like to flow throught the respiratory chain because they can go from enzyme to enzyme each with a lower standart free energy. These enymes together form one big complex within the inner membrane with Fe-S clusters enabeling electrons to flow through the membrane by giving them a kind of a power stroke (see here).
This as an simplyfied answer on a example.
The following is multiple choice question (with options) to answer.
Ion pumps, the biological machines responsible for the selective transport of metal ions, are complex assemblies of what? | [
"minerals",
"acids",
"proteins",
"cells"
] | C | Ion Transport The Na+, K+, Mg2+, and Ca2+ ions are important components of intracellular and extracellular fluids. Both Na+ and Ca2+ are found primarily in extracellular fluids, such as blood plasma, whereas K + and Mg2+ are found primarily in intracellular fluids. Substantial inputs of energy are required to establish and maintain these concentration gradients and prevent the system from reaching equilibrium. Thus energy is needed to transport each ion across the cell membrane toward the side with the higher concentration. The biological machines that are responsible for the selective transport of these metal ions are complex assemblies of proteins called ion pumps. Ion pumps recognize and discriminate between metal ions in the same way that crown ethers and cryptands do, with a high affinity for ions of a certain charge and radius. Defects in the ion pumps or their control mechanisms can result in major health problems. For example, cystic fibrosis, the most common inherited disease in the United States, is caused by a defect in the transport system (in this case, chloride ions). Similarly, in many cases, hypertension, or high blood pressure, is thought to be due to defective Na+ uptake and/or excretion. If too much Na+ is absorbed from the diet (or if too little is excreted), water diffuses from tissues into the blood to dilute the solution, thereby decreasing the osmotic pressure in the circulatory system. The increased volume increases the blood pressure, and ruptured arteries called aneurysms can result, often in the brain. Because high blood pressure causes other medical problems as well, it is one of the most important biomedical disorders in modern society. For patients who suffer from hypertension, low-sodium diets that use NaCl substitutes, such as KCl, are often prescribed. Although KCl and NaCl give similar flavors to foods, the K + is not readily taken up by the highly specific Na+-uptake system. This approach to controlling hypertension is controversial, however,. |
SciQ | SciQ-3363 | proteins, muscles, amino-acids, protein-binding
It is possible for people on unusual protein diets, either because they are avoiding animal products or using incomplete protein supplements, to develop a particular amino acid deficiency. Otherwise, as long as all amino acids are supplied, there is no difference on health or muscles to consuming "low quality" vs "high quality" proteins.
The following is multiple choice question (with options) to answer.
Lack of proper food over a period of time can lead to what condition, where the body is not getting enough nutrients to grow and stay healthy? | [
"malnutrition",
"bulimia",
"anemia",
"mortality"
] | A | Refusing one meal won't stunt your growth. But lack of proper food over a period of time can lead to malnutrition. That means, the body is not getting enough nutrients to grow and stay healthy. Kids who are malnourished may not grow as tall as they would otherwise. |
SciQ | SciQ-3364 | water, molecular-structure, polarity, dipole
Now let's take water. The central atom (Oxygen) has a valence configuration of $2s^22p^4$, that is, 6 electrons. In water, since we have two single bonds, we have one $\sigma$ bond each (and no $\pi$ bonds). So we have total two $\sigma$ bonds.
But this leaves us with $6-2=4$ unpaired valence electrons. These form two "lone pairs" (pairs of electrons which do not bond). With two lone pairs and two $\sigma$ bonds, $x=4$. This gives us a tetrahedral structure (third in the balloon diagram). Two of the four points in the tetrahedron are occupied by the lone pairs, and two by bonds:
(Note that the angle 104.5 is not the same as the angle in perfect tetrahedra, 109.25--this is due to the lone pairs repelling each other)
So finally, we have the following "bent" structure for water:
From the structure, as shown above, it is very easy to check if the molecule has a dipole moment.
The following is multiple choice question (with options) to answer.
Two water molecules contain 4 hydrogen atoms and how many oxygen atoms? | [
"2",
"4",
"1",
"6"
] | A | Two water molecules contain 4 hydrogen atoms and 2 oxygen atoms. A mole of water molecules contains 2 moles of hydrogen atoms and 1 mole of oxygen atoms. |
SciQ | SciQ-3365 | genetics, evolution, natural-selection, sexual-selection, sexual-dimorphism
"We find that females from populations selected for larger male
mandibles have lower fitness, whereas females in small-mandible
populations have highest fitness, even though females never develop
exaggerated mandibles."
One thing that is really quite cool about that experiment is that the response came in a non-equivalent trait, i.e. it was not female mandibles but other traits that evolved. There is generally less prior probability that there will be a cross-sex cross-trait covariance unless the traits have clear links.
The following is multiple choice question (with options) to answer.
The carrying angle is larger in females to accommodate their what? | [
"cranium",
"narrower pelvis",
"broader shoulders",
"wider pelvis"
] | D | the ulna and radius bones. The small, rounded area that forms the distal end is the head of the ulna. Projecting from the posterior side of the ulnar head is the styloid process of the ulna, a short bony projection. This serves as an attachment point for a connective tissue structure that unites the distal ends of the ulna and radius. In the anatomical position, with the elbow fully extended and the palms facing forward, the arm and forearm do not form a straight line. Instead, the forearm deviates laterally by 5–15 degrees from the line of the arm. This deviation is called the carrying angle. It allows the forearm and hand to swing freely or to carry an object without hitting the hip. The carrying angle is larger in females to accommodate their wider pelvis. |
SciQ | SciQ-3366 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
Examples of organ systems in a human include the skeletal, nervous, and what? | [
"reproductive systems",
"immune systems",
"affecting systems",
"nervous systems"
] | A | Organ system : Group of organs that work together to perform a certain function. Examples of organ systems in a human include the skeletal, nervous, and reproductive systems. |
SciQ | SciQ-3367 | human-biology
Title: Stopping the effect of hormone Many hormones released by endocrine organs travel down in the blood and bind to specific receptors on the target cells. What then breaks that binding of the molecule with the receptor ? ( thus inactivating further stimulation of the target cell ) The binding is reversible typically; part of the potency of a drug is ow well and for how long it binds to its target. There's a natural equilibrium of binding and dissociation. Many drugs, once bound to their cognate receptor, cause a down regulation of their cognate receptor on the target cell. The bound/activated downstream signalling pathways may be inhibited by ubiquitination of the downstream signals themselves or upregulation of antagonists etc. The hormone itself has a half life, which is very important, thus levels naturally decrease and for some hormones this is incredibly rapid. Levels may decrease due to breakdown or excretion. Increase of binding hormones may decrease free hormone thus it's effect also.
The following is multiple choice question (with options) to answer.
Most hormones are controlled by what type of feedback, which causes the hormone to decrease its own production? | [
"positive",
"neutral",
"unusual",
"negative"
] | D | Most hormones are controlled by negative feedback in which the hormone feeds back to decrease its own production. This type of feedback brings things back to normal whenever they start to become too extreme. Positive feedback is much less common because it causes conditions to become increasingly extreme. |
SciQ | SciQ-3368 | pregnancy, children
Title: What happens to the umblical cord inside the mother? After giving birth to a child, the umblical cord is cut (and stored if they want). The end connected to the child's navel will fell off eventually but what happens to the end inside the mother?
Will it be removed right after birth by doctors or what happens? Labor is typically divided into 3 stages:
Stage 1: From the onset of contractions (true labor pains) to full dilatation of the cervix (which is about 10 cm) - this takes about 12 to 18 hours
Stage 2: From full dilatation of cervix to expulsion of fetus - This takes about ~ 30 minutes
Stage 3. From expulsion of fetus to expulsion of placenta - this takes about ~ 15 minutes. During the third stage, the umblical cord which is attached to placenta is expelled along with the placenta. This would be the answer to your question.
Source:Hympath.com
The following is multiple choice question (with options) to answer.
What is the stage called for babies that are in the first year of life after birth? | [
"primary stage",
"adolescence",
"original stage",
"infancy"
] | D | Infancy is the first year of life after birth. Infants are born with a surprising range of abilities. For example, they have well-developed senses of touch, hearing, and smell. They can also communicate their needs by crying. During their first year, they develop many other abilities, including those described below. For a video of major milestones in the first year of life, go to this link: http://www. youtube. com/watch?v=5_Ao_3hTS6I . |
SciQ | SciQ-3369 | cell-biology, terminology
Title: What is the difference between cytosol and cytoplasm? I've generally seen cytosol defined as the solution inside cells minus the organelles, cytoskeleton, etc and cytoplasm as the cytosol plus the organelles, cytoskeleton, etc. This naturally leads to the impression that cytosol is the cytoplasm minus all the solids. The problem here is that there are all sorts of other large molecules in the cells which could be thought of as solid. Are they also part of the cytosol or are they suspended in it? (I.e. are they part of the cytosol or are they non-cytosol components of the cytoplasm?)
Basically, I'm asking if the precise definition of cytosol is just anything in the cell that's not behind an endomembrane (save the exoskeleton) or if the dividing line is something else.
Subquestion: things can get even more terminologically confused because the cytosol is sometimes called the matrix. What the heck is the preferred terminology with this stuff? IMO, the definitive answer to this question is given in a paper by J. S Clegg. He traced the origin of the term cytosol to a book chapter by H. A. Lardy, and confirmed by email that Lardy had indeed coined the term. Their definition of cytosol is as follows:
... that portion of the cell which is found in the supernatant fraction after centrifuging the homogenate at 105 000 x g for 1 hour.
The following is multiple choice question (with options) to answer.
What forms a barrier between the cytoplasm and the environment outside the cell? | [
"epidermis",
"plasma membrane",
"cuticle",
"cell wall"
] | B | The plasma membrane forms a barrier between the cytoplasm and the environment outside the cell. The plasma membrane has selective permeability. |
SciQ | SciQ-3370 | thermodynamics, atoms, phase-transition
But let's look at how the states change. In a solid, you have a bunch of atoms that can be thought of as masses connected by springs. As heat is added to the system, the atoms begin to vibrate in the lattice of springs. As more heat is added, they vibrate enough to break the springs. This is when the solid begins to melt and turn to a liquid.
Now you have a liquid where the atoms are all moving around but they aren't free to move wherever they want. More heat is added to the system and the atoms begin to translate faster and faster. Eventually they translate fast enough to overcome the forces that are holding them together in a liquid. Now they fly free and are a gas.
So ultimately, heat is energy that makes atoms and molecules move in some way. They may translate, rotate, vibrate, or the electrons may begin moving around depending on how much heat is there and what configuration the molecule has.
The following is multiple choice question (with options) to answer.
Over time, what changes solid rock into pieces? | [
"weathering",
"creep",
"leaching",
"metamorphosis"
] | A | Weathering changes solid rock into pieces. These pieces are called sediments. Sediments are described in the chapter Earth's Materials and Crust . Sediments are different sizes of rock particles. Boulders are sediments; so is gravel. At the other end, silt and clay are also sediments. Weathering may also cause the minerals at the Earth’s surface to change form. The new minerals that form are stable at the Earth’s surface. There are two types of weathering, mechanical and chemical. These are discussed in the next two concepts. |
SciQ | SciQ-3371 | cell-biology, mitochondria, mitosis
Title: Are cells guaranteed to get at least one mitochondrion when they divide? If mitochondria exist at random within a cell, isn't there a possibility that cell division will result in a daughter cell with no mitochondria? If not, what is the process for guaranteeing at least one is present in each daughter cell? If so, what happens to that cell?
Isn't there a possibility that cell division will result in a daughter
cell with no mitochondria?
Yes, there is always the possibility. However, there must be a strong negative selection pressure against eukaryotic life that cannot achieve the proper partitioning of mitochondria, so you can imagine that there are mechanisms in place to prevent this case.
Mitochondria are both passively and actively partitioned to daughter cells. This is understood to occur through the cytoskeleton and with the control of mitochondrial fusion and fission at key stages of the cell cycle, prior to mitosis and cytokinesis!
Here is a great review from several years ago that addresses your question well.
The following is multiple choice question (with options) to answer.
Eukaryotic cells undergo what kinds of divisions that more primitive cells do not? | [
"mitosis",
"meiosis",
"homologous",
"budding"
] | A | Mitosis , or division of the nucleus, occurs only in eukaryotic cells. By the time mitosis occurs, the cell’s DNA has already replicated. Mitosis occurs in four phases, called prophase, metaphase, anaphase, and telophase. You can see what happens in each phase in Figure below . The phases are described below. You can also learn more about the phases of mitosis by watching this video: https://www. youtube. com/watch?v=gwcwSZIfKlM . |
SciQ | SciQ-3372 | human-biology, human-anatomy, human-physiology
Title: How can we move our lips even though they don't have any bones? How can we move our lips even though they don't have any bones?
We can move everything if it is attached to the bones. Example: Legs & Arms.
otherwise we can't move it. Because of the Orbicularis oris muscle, it's a complex of muscles in the lips that encircles the mouth, It forms the greater part of the substance of the lips, lying between the skin and the mucus membrane, and extending from the edge of each lip to its root.
The following is multiple choice question (with options) to answer.
The orbicularis oris is a circular muscle that moves the lips, and the orbicularis oculi is a circular muscle that does what? | [
"closes the eye",
"moisturizes the eye",
"pressure the eye",
"opens the eye"
] | A | The orbicularis oris is a circular muscle that moves the lips, and the orbicularis oculi is a circular muscle that closes the eye. The occipitofrontalis muscle moves up the scalp and eyebrows. The muscle has a frontal belly and an occipital (near the occipital bone on the posterior part of the skull) belly. In other words, there is a muscle on the forehead ( frontalis) and one on the back of the head ( occipitalis), but there is no muscle across the top of the head. Instead, the two bellies are connected by a broad tendon called the epicranial aponeurosis, or galea aponeurosis (galea = “apple”). The physicians originally studying human anatomy thought the skull looked like an apple. The majority of the face is composed of the buccinator muscle, which compresses the cheek. This muscle allows you to whistle, blow, and suck; and it contributes to the action of chewing. There are several small facial muscles, one of which is the corrugator supercilii, which is the prime mover of the eyebrows. Place your finger on your eyebrows at the point of the bridge of the nose. Raise your eyebrows as if you were surprised and lower your eyebrows as if you were frowning. With these movements, you can feel the action of the corrugator supercilli. Additional muscles of facial expression are presented in Figure 11.8. |
SciQ | SciQ-3373 | biochemistry, botany
Title: Ripening bananas artificially: What is the biological theory behind? I am a resident of the tropical island of Sri Lanka, and we have a strange traditional method to ripen our banana harvest quickly.
What we do is this: We dig a pit in earth that is enough to put the whole banana cluster in. Then, after safely laying the bananas in the pit, we cover up the pit with a sheet such that only a small hole from a side remains: visualize a small 3-4 inch door to the pit.
After that, we light a fire with semi-dry leaves just outside the pit's door. (Semi-dry leaves are used to get as much smoke as possible. Dry leaves do not give that much smoke, because they completely oxidize quickly). And the smoke is sent through the door by blowing it with the aid of a bamboo.
This sends a good amount of smoke and warms the inside of the pit considerably. And by experience I can tell you that this makes the bananas to ripen really quickly. I have done a controlled experiment where half of the cluster was not put into the pit. Bananas in the pit ripen overnight and the control sample took days to ripen.
Can anybody explain what are the bio-mechanisms that are working here? Ripening of bananas (and other fruits) is induced by acetylene and ethylene (Ethyne and Ethene) (see reference 1), which acts as a hormone and induces the ripening process. The incomplete combustion of the leaves produces ethylene, additionally the warmth of the process will help the enzymes as well. There is even a paper about this technique (although it is unfortunately not accessible), see reference 2 for more information. Smoking Chambers are routinely used in this process, see reference 3 and 4.
References:
Role of Ethylene in Fruit Ripening
Effects of smoking on some physiological changes in bananas.
Fruit Ripening
Technology for ripening fruits as important as marketing them
The following is multiple choice question (with options) to answer.
What may have developed to help our ancestors distinguish between ripe and unripe fruits? | [
"fine motor skills",
"acute hearing",
"night vision",
"color vision"
] | D | McKay Savage. Color vision may have developed to help our ancestors distinguish between ripe and unripe fruits . CC BY 2.0. |
SciQ | SciQ-3374 | botany, mathematical-models, statistics, biostatistics, migration
Title: Biostatistics: Pollen dispersal directionality What Information am I looking for?
Think about a tree that is sending pollen all over the place. Because of wind, most pollen grain will go toward one direction. Imagine, we split the 2D area around the tree where pollen grains fall into two half disks of equal size. We chose the disks so that the number of pollen grains falling into one half-disk is minimized and the quantity of pollen falling in the other half-disk is maximized.
The information I need is what proportion of pollen grain falls into each disk? Is it $\frac{0.5}{0.5}$ (in which case the wind would have no effect) or is it something like $\frac{0.8}{0.2}$?
Where to get the information from?
I was reading this paper about pollen dispersal directionality and was trying to extract the info I need.
On pages 4 and 5 they explain their analysis under the section statistical procedure. More specifically, in the first paragraph of the 5th page, they seem to describe the meaning of the parameters that are trying to estimate. One of them is the so-called directionality parameter $\delta$. I don't understand how to interpret this parameter $\delta$. This parameter is part of a logistic regression I think (although the authors do not characterize it as such) of "mating success" $y$ against variables $d$ ("distance") and $h$ ("height") and an angular variable $a = \cos(\alpha_0 - \alpha)$. ($\alpha_0$ is the "presumed prevailing direction of effective pollen dispersal," which apparently is not estimated from these data.) The corresponding parameters of the model are $\beta$, $\gamma$, and $\delta$, respectively, hence
$$\phi_j = \Pr(y_j = 1) = \frac{\exp\left(\beta d_j + \gamma h_j + \delta a_j\right)}{\sum_{k=1}^r \exp\left(\beta d_k + \gamma h_k + \delta a_k\right)}$$
The following is multiple choice question (with options) to answer.
Which stage is specialized for dispersal & reproduction? | [
"adult stage",
"cocoon stage",
"larval stage",
"fetal stage"
] | A | |
SciQ | SciQ-3375 | geophysics, seismology, instrumentation
Title: How can I calculate the sensitivity of a seismometer? I would like to know if a specific seismometer can measure 1 micron/sec velocity. I have a few specs from the datasheet but I'm not a seismologist and am trying to figure out how to relate the specs to one another.
I have:
Velocity output band: 30s (0.03Hz) to 100 Hz
Output Sensitivity: 2400 V/m/s
Peak/Full scale output: Differential: +- 20V
Sensor dynamic range: 137 dB @ 5 Hz
Thanks in advance! This is a partial answer because I'm not an expert and because I don't know what the dynamic range of 137 dB means. Hopefully you can add a little more information.
tl;dr: if 137 dB is the dynamic range in power, then it's 68.5 dB in voltage and velocity which sounds more plausible, and makes the velocity sensitivity well below 1 micron per second. However we don't yet know what the noise and bandwidth of your signal are yet so we can't evaluate that.
I have a few specs from the datasheet...
The more information you share from the data sheet the better although I've now just noticed that the question is about three years old.
Also, there may be some helpful insight at How sensitive are typical seismometers?
The following is multiple choice question (with options) to answer.
What three parameters do seismographs measure? | [
"aging , length and distance",
"trouble , length and distance",
"strength, length and distance",
"height, width and distance"
] | C | Seismograms contain a lot of information about an earthquake: its strength, length and distance. Wave height used to determine the magnitude of the earthquake. The seismogram shows the different arrival times of the seismic waves ( Figure below ). The first waves are P-waves since they are the fastest. S-waves come in next and are usually larger than P-waves. The surface waves arrive just after the S-waves. If the earthquake has a shallow focus, the surface waves are the largest ones recorded. |
SciQ | SciQ-3376 | image-processing, local-features, pattern
These are then used as templates for a procedural pattern generation technique I am developing. Images are randomly generated, generation settings that produce high similarity are kept to be further tweaked. The procedurally generated images could be anything from random pixels to intricate shapes, slowly converging at the image of highest possible similarity. A classification of the repertoire of the patterns that can be exhibited by reaction diffusion models has been attempted and this map might already be close to what you are after.
Other than this, if you absolutely have to create a metric of similarity that emerges from the images themselves then my suggestion would be to look at some form of invariant or universal feature.
You could for example look at Mutual Information between the two images and more specifically, LZ Complexity (which is not reciprocal, so $f(x,y) \neq f(y,x)$ where $f$ is the metric). The difference here is that mutual information essentially characterises the differences between the distributions that give rise to signals (therefore, the processes where they came from).
Also, looking at the sort of "shapes" the model creates, it seems to swing between relatively broad line strokes and point / circle structures. So, you could apply a simple threshold to the resulting image and then run a Hough Transform on it and try to estimate a ratio of "line-icity" (i.e. amount of sharp tall points in the image) to "circleicity" (double pairs of points at a specific configuration). I am not sure how sensitive or accurate would that be for a small change in the model's parameters though.
Hope this helps.
The following is multiple choice question (with options) to answer.
What topographic feature does a circle with inward hatches represent on a contour map? | [
"a lake",
"vegetation",
"a depression",
"a mountain"
] | C | On a contour map, a circle with inward hatches indicates a depression. |
SciQ | SciQ-3377 | thermodynamics, statistical-mechanics, statistics
Mathematically, this is the right result, but... why does this have to be like this? Intuitively, I expected all the particles on the excited state.
My professor said "no, this can only be the case with negative temperatures", making this whole concept even more obscure. Particles in the environment have, on average, energy of about $k_{\textrm{B}}T$. If $k_{\textrm{B}}T \gg \mathcal{E}$, the two internal states of the system are essentially degenerate, as far as the environment is concerned. In other words, it costs essentially no energy (relative to $k_{\textrm{B}}T$) for the system to change state. Therefore, in each "collision" of a particle in the environment with a particle in the system, the outcome of the collision is essentially random: the system particle will be in either of its internal states with equal probability.
The following is multiple choice question (with options) to answer.
Which temperatures cause particles of reactants to have more energy? | [
"reducing",
"lower",
"non-existant",
"higher"
] | D | When the temperature of reactants is higher, the rate of the reaction is faster. At higher temperatures, particles of reactants have more energy, so they move faster. They are more likely to bump into one another and to collide with greater force. For example, when you fry an egg, turning up the heat causes the egg to cook faster. The same principle explains why storing food in a cold refrigerator reduces the rate at which food spoils (see Figure below ). Both food frying and food spoiling are chemical reactions that happen faster at higher temperatures. |
SciQ | SciQ-3378 | photosynthesis, chloroplasts
Title: Chloroplasts in an animal cell What would happen if we inject a chloroplast organelle into an animal cell?
Will the animal cell destroy it? Or is it possible that the chloroplast will somehow survive, and even replicate? Could there be photosynthesis in such a cell, or will some of the necessary mechanisms be missing? To answer your bigger question:
Yes, most of this is possible - under some conditions -, and animals and animal cells can acquire chloroplasts, and use them.
E.g.: see Elysia chlorotica whose cells actively take up chloroplasts and use them, and keep them alive (though not replicating). - Though some genes of algae are also contained in the Elysia chlorotica genome - which may be considered as partial replication.
Also there are salamanders that have replicating algae within them (since embryogenesis) - even algae (with chloroplasts) within animal cells - though here the algae might be rather understood as symbionts or "cell types", and the animal cells don't have the chloroplasts by themselves.
The following is multiple choice question (with options) to answer.
Not all cells of a leaf carry out photosynthesis. cells within the middle layer of a leaf have chloroplasts, which contain the photosynthetic what? | [
"wires",
"structure",
"apparatus",
"pipes"
] | C | Figure 5.7 Not all cells of a leaf carry out photosynthesis. Cells within the middle layer of a leaf have chloroplasts, which contain the photosynthetic apparatus. (credit "leaf": modification of work by Cory Zanker). |
SciQ | SciQ-3379 | genetics, homework
Title: law of independent assortment Self fetilization of F1 dihybrids, following independent assortment of alleles result in:
a) 3/16 Tall-rounds ; 3/16 dwarf-wrinkled
b) 9/16 Tall-wrinkled ; 3/16 dwarf-round
c) 9/16 Tall-round ; 3/16 dwarf-round
d) 3/16 Tall-wrinkled ; 3/16 dwarf-round
This question was asked in MCAT exam in Pak for which I'm preparing this year.... no genetic arcitecture was mentioned in question... The above mentioned is original format of question.... in ans-key, the ans is D but I am confused why it can't be C. In real life, round and tall are dominant traits in pea plants, which would make C and D both correct. I don't think people are expected to memorize the traits of pea plants, so the question ought to tell you somewhere which traits are dominant. There must be an error in the question as printed.
The following is multiple choice question (with options) to answer.
What is the advantage of selecting for certain genetic traits for crops? | [
"promotes productivity",
"protection from pests",
"improves taste",
"Faster growth"
] | A | Improving crops by selecting for certain genetic traits. The desired traits promote productivity. Recently, genetically engineered crops have been introduced. |
SciQ | SciQ-3380 | botany
Title: Do plants absorb toxins from the soil? Consider a plant like Aloe Vera that grows up in a toxic environment where the concentration of pesticides, and materials like lead, mercury, cadmium, arsenic etc is very high(e.g. Marshland dumping yard ). Would that mean that the extract from these plants would contain all these toxic elements. Not "all of them". But yes, plants suck up water from the soil, with everything dissolved in this water - nutrients, heavy metals, poisons. And also they breathe air, and absorb stuff via this route.
There probably are some toxins which will not enter the plant, because their molecules are too large and/or fragile. For example, should a plant root come in contact with snake venom, I cannot imagine that any venom will end up stored in the plant leaves.
Plants also have their own metabolism, so they will change/deactivate some toxins. I've seen claims that some plants "purify" formaldehyde, although I don't trust the sources enough to be sure of that.
But the smaller the poison molecule, and the less similar to stuff which is usually digested in nature, the more likely that it will enter the plant and stick around instead of being broken down. The heavy metals you mentioned are prime candidates. If they are present in the groundwater - or also lead from air pollution, before we banned leaded gasoline - they end up in plants, including food plants. And mushrooms are even more at risk.
Growing food near waste dumps is a known problem in farming, and sometimes makes the news, for example here:
http://bigstory.ap.org/article/mafia-toxic-waste-dumping-poisons-italy-farmlands
The following is multiple choice question (with options) to answer.
What is given off from plants and taken in by animals? | [
"oxygen",
"sulfur",
"methane",
"nitrogen"
] | A | |
SciQ | SciQ-3381 | history, units, physical-constants, si-units, absolute-units
The international system of units, the SI, is the system of units in which
the unperturbed ground state hyperfine splitting frequency of the caesium 133 atom $\Delta v(^{133}\text{Cs})_{\text{hfs}}$ is exactly $9\text{ }192\text{ }631\text{ }770$ hertz,
the speed of light in vacuum $c$ is exactly $299\text{ }792\text{ }458$ metre per second,
the Planck constant $h$ is exactly $6.626\text{ }069\text{ }57\times10^{-34}$ joule second,
the elementary charge $e$ is exactly $1.602\text{ }176\text{ }565\times10^{-19}$ coulomb,
the Boltzmann constant $k$ is exactly $1.380\text{ }648\text{ }8\times10^{-23}$ joule per kelvin,
the Avogadro constant $N_\text{A}$ is exactly $6.022\text{ }141\text{ }29\times10^{23}$ reciprocal mole,
the luminous efficacy $K_\text{cd}$ of monochromatic radiation of frequency $540\times 10^{12}$ hertz is exactly $683$ lumen per watt,
The following is multiple choice question (with options) to answer.
What is the simplest unit that has the fundamental chemical properties of an element? | [
"neutron",
"cell",
"nucleus",
"atom"
] | D | Covalent Molecules and Compounds Just as an atom is the simplest unit that has the fundamental chemical properties of an element, a molecule is the simplest unit that has the fundamental chemical properties of a covalent compound. Some pure elements exist as covalent molecules. Hydrogen, nitrogen, oxygen, and the halogens occur naturally. |
SciQ | SciQ-3382 | bacteriology, ph, gut-bacteria
Any one of these is enough to have a bactericidal or bacteriostatic effect! This is also why cells that do live in slightly alkaline or acidic environments have to specialize, and they have narrow windows of pH that they can survive under, because they have to compensate so much to counteract the protonation or lack-thereof in their environments.
The following is multiple choice question (with options) to answer.
Bacteria are what kind of cell? | [
"protists",
"prokaryotes",
"eukaryotes",
"blood"
] | B | The rod-shaped organisms in Figure below are bacteria called Salmonella . Bacteria (bacterium, singular) are prokaryotes in the Bacteria Domain. The word Salmonella may sound familiar. That's because Salmonella is a common cause of food poisoning. Many other types of bacteria also cause human diseases. But not all bacteria are harmful to people. In fact, we could not survive without many of the trillions of bacteria that live in or on the human body. You'll learn why when you read this lesson. |
SciQ | SciQ-3383 | biochemistry
Alright so this is the oxidation of one mole of glucose equation (Without the ATPs) but till now I don't exactly know the correct answer for this question, but to not create any confusion this question is related to the Aerobic respiration (Glycolysis, Krebs Cycle and Electron transport chain).
Here's how I approached this question:
(a) is obviously not correct because the products of glycloysis are 2 pyruvate molecules and 2 ATP molecules so I checked off this choice.
(b) However seems correct because the products of 2 Krebs cycle is 4 CO2 and there is already 2CO2 when the pyruvate acid formed the 2 acetyl CoA molecules so in total that's 6CO2, but still what about the 6 Water molecules?
(c) is a very debating choice because when there is a "Complete occurrence of oxidative phosphorylation process" so that means 2 Krebs cycles had already occurred and formed the 6CO2, and during the oxidative phosphorylation process Water molecules are formed. and ATPs too? I don't exactly know about the ATPs, but aren't they supposed to be in the equation's products in order for this choice to be correct?
(d) This choice indicates to Krebs cycle but the water molecules only are formed during oxidative phosphorylation only.
So basically all the choices seems very debating and confusing and if I were to choose then I'll go with (C) because it's the only choice that makes sense for the water molecules (and the question asks for water), but I want someone to please answer this question with a brief explanation to why he chose this answer,
Thanks :) This reaction only means complete oxidation of glucose to 6 molecules of carbon dioxide and 6 molecules of water.
Reaction presented in question is very generalized, but the presence of six water molecules only means complete cellular respiration. Check out the actual biochemical pathways which take place to oxidize one glucose molecule.
And other options do not represent the complete cellular respiration, so there will not be formation of six water molecules, only option C means complete oxidation of glucose.
The following is multiple choice question (with options) to answer.
What is the first stage of cellular respiration? | [
"glycolysis",
"Krebs cycle",
"gluconeogenesis",
"decarboxylation"
] | A | The first stage of cellular respiration is glycolysis. It does not require oxygen. |
SciQ | SciQ-3384 | volcanology, measurements, volcanic-hazard, field-measurements
Title: How are data from tiltmeters used to monitor volcanic activity? I've just learned in this answer that tiltmeters (which I assume measure changes in tilt) are used near active volcanos. (Saw a mention in item 4. here also.)
What kind of geological (volcanological?) information can be learned from tilt data? Can it also offer predictive benefits, trigger evacuation warnings? Tiltmeters placed on the flanks of an active volcano can measure changes in the slope angle of the flank. These changes are often inferred to be related to changes in the shape and activity of the magma chamber.
This article provides a quick and dirty example of how these instruments can be used, as well as their limitations.
In this case, the tiltmeters were able to capture the deflation of an erupting magma chamber, but not the precursory inflation. This leads to some inferences about the nature of the magma's ascent through the subsurface.
The article also references studies that were able to detect magma chamber inflation as well.
These kinds of observations definitely add to the body of evidence volcanologists use to assess risk of an eruption, but it's far from a slam dunk.
Here are some examples from that paper, both the long-term trend, and a higher time resolution display during a small eruption:
Fig. 2. Tiltmeter data from V-net (KRMV, KRHV) and Hi-net (MKNH, SUKH) stations during the period from January 23 to February 2, 2011. From here.
Fig. 10. Enlarged view of tiltmeter data during the period from 0:00 to 21:00 on January 26, 2011. Vertical line shows the occurrence time of the small eruption at 7:31 and the beginning of the sub-Plinian eruption, when the amplitude of the seismic tremor increased at 14:49. From here.
The following is multiple choice question (with options) to answer.
Who study volcanoes to be able to predict when a volcano will erupt? | [
"vocologists",
"volcanologists",
"virologists",
"ornithologists"
] | B | Volcanic eruptions can be devastating, particularly to the people who live close to volcanoes. Volcanologists study volcanoes to be able to predict when a volcano will erupt. Many changes happen when a volcano is about to erupt. |
SciQ | SciQ-3385 | electricity, electric-circuits, electric-current, semiconductor-physics
Title: Why does current have to flow in the same direction? If current is just the movement of charged particles, why do the all have to move in the same direction?
For example, if you reverse-bias a diode (connect the positive terminal to the n-type side and the negative terminal to the p-type side), the positive "holes" are attracted to the negative terminal and the electrons are attracted to the positive terminal.
Firstly, if positive holes moving towards the negative terminal corresponds to electrons moving the opposite way (since "holes" aren't real, they're just a lack of electrons). So on both sides of the diode, electrons are moving in the same direction. I don't quite understand how this doesn't correspond to a current flowing.
Not even looking that deep into it, if positive charges are moving one way and negative charges the other, why does it matter if they cross the PN junction? Moving charges = electricity, right?
On top of all this, the battery creates an electric field that goes through all the wires, so why is there no current in the circuit? Electrons don't even move that fast (I've heard drift speed is on the order of cm/s), so "current" is localized in the sense that an electron on one side of a circuit may never even reach the other side. So why aren't localized electric fields enough to create a circuit? All charges don't move in the same direction. It's the net effect that we see. I think you're missing the fact that conventially current was thought to be the flow of positive charges.
Let's consider an example (something less complex than the diode example you've mentioned)
Consider an area element of a conductor and view it in a direction along its plane.
Let there be both positive and negative charges (yes, these are electrons (for a metallic conductor) but for the time being let them be positive and negative charges) to the left and right of the element.
The following is multiple choice question (with options) to answer.
What is the term for electric current that keeps reversing direction? | [
"magnetic current",
"alternating current",
"direct current",
"AC/DC"
] | B | The Figure below shows the direction of the current that is generated by a moving magnet. If the magnet is moved back and forth repeatedly, the current keeps changing direction. In other words, alternating current (AC) is produced. Alternating current is electric current that keeps reversing direction. |
SciQ | SciQ-3386 | lab-techniques, mutations, biostatistics, protein-engineering
NNK = 32 combinations, 50 mutants (n=32, k=50): $p_{all}$ < 0.07%
NNK = 32 combinations, 100 mutants (n=32, k=100): $p_{all}$ < 25.5%
NNK = 32 combinations, 200 mutants (n=32, k=200): $p_{all}$ < 94.6%
As you can see there's a sharp transition as the coverage count increases.
Important caveat: the theoretical value may not give you what you want. In the paper I linked above, we used two degenerate primers with 18 N bases to inject 36bp of random material, which means we had $4.7x10^{21}$ possible combinations and should never have seen a repeat --- except that sequencing showed that we did indeed get several repeats out of only a few hundred colonies. Thus, biases in the biology may lead your statistics to be skewed from what the theory suggests.
The following is multiple choice question (with options) to answer.
How many alleles comes from each parent? | [
"two",
"one",
"none",
"three"
] | B | When gametes unite during fertilization, the resulting zygote inherits two alleles for each gene. One allele comes from each parent. |
SciQ | SciQ-3387 | kinematics, measurements, error-analysis, data-analysis
$s$: the measured distance
$t$: the measured time
and the accompanied uncertainties $\sigma_t$ and $\sigma_s$. In addition, the above formula is only valid if we consider random changes and not systematic errors (which is often called bias). Hope this helps.
The following is multiple choice question (with options) to answer.
How close a measurement is to the correct value for that measurement is known as what? | [
"temperature",
"accuracy",
"rate",
"frequency"
] | B | Accuracy and Precision of a Measurement Science is based on observation and experiment—that is, on measurements. Accuracy is how close a measurement is to the correct value for that measurement. For example, let us say that you are measuring the length of standard computer paper. The packaging in which you purchased the paper states that it is 11.0 inches long. You measure the length of the paper three times and obtain the following measurements: 11.1 in. , 11.2 in. , and 10.9 in. These measurements are quite accurate because they are very close to the correct value of 11.0 inches. In contrast, if you had obtained a measurement of 12 inches, your measurement would not be very accurate. The precision of a measurement system is refers to how close the agreement is between repeated measurements (which are repeated under the same conditions). Consider the example of the paper measurements. The precision of the measurements refers to the spread of the measured values. One way to analyze the precision of the measurements would be to determine the. |
SciQ | SciQ-3388 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
What pigment is required for photosynthesis to occur? | [
"xanthophyll",
"chroma",
"chlorophyll",
"carotene"
] | C | |
SciQ | SciQ-3389 | reproduction
Excerpts from the references that lead to the short answer above:
In the developing female fetus, oogonia become primary oocytes that begin the first division of meiosis. However, this division is not completed and the primary oocytes remain “frozen” in the prophase stage of the first meiotic division.
At birth, oogonia are no longer present. Each primary oocyte is surrounded by a single layer of squamous epithelial cells called follicular cells. The primary oocyte together with its follicular cells is called a primordial follicle. There are about two million primordial follicles with their primary oocytes in the ovaries at birth suspended in the first division of meiosis.
As the female grows, primary oocytes begin to die and disappear with their follicular cells. This process continues until puberty when there are only about 400,000 primordial follicles left in the ovaries. The primary oocytes continue the process of oogenesis after puberty begins.[Source]
The total number of primary oocytes at birth is estimated to vary from 700,000 to2 million. During childhood most oocytes become atretic; only approximately400,000 are present by the beginning of puberty, and fewer than 500 will be ovulated.[Source]
Primary oocytes reach their maximum development at ~20[6] weeks of gestational age, when approximately seven million primary oocytes have been created; however, at birth, this number has already been reduced to approximately 1-2 million.Recently, however, two publications have challenged the belief that a finite number of oocytes are set around the time of birth.[Source]
In the human embryo, the thousand or so oogonia divide rapidly from the second to the seventh month of gestation to form roughly 7 million germ cells.[Source]
REFERENCES:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008772
The following is multiple choice question (with options) to answer.
What begins approximately six weeks after fertilization in an embryo? | [
"elongation",
"ossification",
"incubation",
"calcification"
] | B | Development of Bone Ossification, or osteogenesis, is the process of bone formation by osteoblasts. Ossification is distinct from the process of calcification; whereas calcification takes place during the ossification of bones, it can also occur in other tissues. Ossification begins approximately six weeks after fertilization in an embryo. Before this time, the embryonic skeleton consists entirely of fibrous membranes and hyaline cartilage. The development of bone from fibrous membranes is called intramembranous ossification; development from hyaline cartilage is called endochondral ossification. Bone growth continues until approximately age 25. Bones can grow in thickness throughout life, but after age 25, ossification functions primarily in bone remodeling and repair. |
SciQ | SciQ-3390 | bond
Title: Is energy required to form bonds [phase change] My question is if any energy is required to form bonds, for instance when there is a phase change?
If I am correct, energy might be required in the beginning, to make the reaction start and then release a bigger amount of energy than it was putted in. However, in terms of molecular behaviour in a phase change, I think there should not be any energy required to make the molecules to form bonds, if they are placed in a system which has a lower temperature than the molecules. Would they not lose the kinetic energy after a specific time? Bond formation always lowers the energy of the system (or bond formation is a consequence of lower energy, take your pick.)
Indeed, you may have to add energy, because presumably certain bonds must break in order to rearrange the atoms.
Adding energy won't guarantee formation of much higher energy isomers, because the atoms have a large amount of kinetic energy, and so they can just as easily turn around and go back whence they came.
Sometimes the kinetic energy can be dissipated by solvent, collisions with inert gasses, etc. and then you may end up with a measurable quantity of the higher energy species.
The following is multiple choice question (with options) to answer.
What do you call the energy that must be overcome in order for a chemical reaction to occur, or the minimum energy required to start a chemical reaction? | [
"expression energy",
"phase energy",
"kinetic energy",
"activation energy"
] | D | Regardless of whether reactions are exothermic reactions or endothermic reactions , they all need energy to get started. This energy is called activation energy . Activation energy is like the push you need to start moving down a slide. The push gives you enough energy to start moving. Once you start, you keep moving without being pushed again. Activation energy is defined as the energy that must be overcome in order for a chemical reaction to occur, or the minimum energy required to start a chemical reaction. The concept of activation energy is illustrated in Figure below . |
SciQ | SciQ-3391 | taxonomy, mammals, cladistics
Title: Why aren't mammals and reptiles considered amphibians? We've all heard it: birds descend from dinosaurs, so they're dinosaurs too. But this got me thinking: doesn't this mean that, for instance, all terrestrial vertebrates – including humans – are technically fish? A recent video by MinuteEarth and the Wikipedia article for "Fish" confirmed my shower thought hypothesis.
Interesting. But... all amniotes, i.e. reptiles (and, by extension, birds) and mammals, descend from amphibians, right? If so, then why aren't they considered amphibians too? Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend from Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).
The following is multiple choice question (with options) to answer.
Frogs and toads, salamanders and newts, and caecilians are the three orders of what group of animals? | [
"amphibians",
"marsupials",
"mammals",
"reptiles"
] | A | There are about 6,200 known species of living amphibians. They are classified into three orders: frogs and toads, salamanders and newts, and caecilians. |
SciQ | SciQ-3392 | energy, biophysics, soft-matter
Title: Why is the energy required to bend a flat bilayer membrane to vesicle independent of its radius? Imagine that we have a flat bilayer sheet (let it be a disc-shaped bilayer) lipid membrane. When I naively think about this system being bent to form a vesicle (closed bilayer membrane), my intuition says that the larger the radius (surface area) of the membrane, the easier it is for the flat bilayer to close to a vesicle form. But it seems that the bending energy required for the flat membrane to close to a vesicle seems to be independent of the radius of the vesicle.[1,2] Why is the energy required to bend a flat bilayer membrane to vesicle independent of its radius?
[1]: Mechanics of the cell by David Boal, section 7.5.1
The following is multiple choice question (with options) to answer.
What are vesicles made of? | [
"filaments",
"cells",
"membranes",
"phospholipids"
] | D | A vesicle. Because vesicles are made of phospholipids, they can break off of and fuse with other membraneous material. This allows them to serve as small transport containers, moving substances around the cell and to the cell membrane. |
SciQ | SciQ-3393 | human-biology
Title: Does sweat contain DNA information? I was reading this article : Perspiration
The first question which came to my mind after reading the composition of sweat was whether it contains any information about the DNA or not?
I haven't had much interaction with biology since 12th grade (2010), so kindly answer in layman's terms and detail as well. The Wikipedia page you linked says that sweat is composed of a liquid similar to blood plasma. As all DNA in humans is stored in the nucleus of a cell, it seems unlikely that the sweat itself would contain any DNA.
However, when someone sweats significantly, I can't imagine that no skin cells end up in the sweat. In any case in which this occurs, then the DNA in the cell is in the sweat. Additionally, with small amounts of sweat, I can't imagine how it would be collected without getting any skin cells in it.
This source confirms that sweat contains DNA in some form. Additionally, I think the following quote from here shows that it is stored in cells:
In every case, what is being tested is the DNA contained in cells of human tissue
The following is multiple choice question (with options) to answer.
Deoxyribonucleic acid (dna) is nucleotide that stores what type of information? | [
"variation",
"mononucleus",
"genetic",
"mutation"
] | C | Nucleic Acids The nucleic acids differ in their type of pentose sugar. Deoxyribonucleic acid (DNA) is nucleotide that stores genetic information. DNA contains deoxyribose (so-called because it has one less atom of oxygen than ribose) plus one phosphate group and one nitrogen-containing base. The “choices” of base for DNA are adenine, cytosine, guanine, and thymine. Ribonucleic acid (RNA) is a ribose-containing nucleotide that helps manifest the genetic code as protein. RNA contains ribose, one phosphate group, and one nitrogen-containing base, but the “choices” of base for RNA are adenine, cytosine, guanine, and uracil. The nitrogen-containing bases adenine and guanine are classified as purines. A purine is a nitrogen-containing molecule with a double ring structure, which accommodates several nitrogen atoms. The bases cytosine, thymine (found in DNA only) and uracil (found in RNA only) are pyramidines. A pyramidine is a nitrogen-containing base with a single ring structure Bonds formed by dehydration synthesis between the pentose sugar of one nucleic acid monomer and the phosphate group of another form a “backbone,” from which the components’ nitrogen-containing bases protrude. In DNA, two such backbones attach at their protruding bases via hydrogen bonds. These twist to form a shape known as a double helix (Figure 2.29). The sequence of nitrogen-containing bases within a strand of DNA form the genes that act as a molecular code instructing cells in the assembly of amino acids into proteins. Humans have almost 22,000 genes in their DNA, locked up in the 46 chromosomes inside the nucleus of each cell (except red blood cells which lose their nuclei during development). These genes carry the genetic code to build one’s body, and are unique for each individual except identical twins. |
SciQ | SciQ-3394 | ornithology, reptile, cladistics
Title: If dinosaurs could have feathers, would they still be reptiles? I just finished watching a video where it was mentioned that nowadays birds are dinosaurs and non-avians dinosaurs could have feathers.
I confirmed this from wikipedia:
Birds are highly advanced theropod dinosaurs, characterised
by feathers, a beak with no teeth, the laying of hard-shelled eggs, a
high metabolic rate, a four-chambered heart, and a lightweight but
strong skeleton.
And:
Direct fossil evidence of feathers or feather-like structures has
been discovered in a diverse array of species in many non-avian
dinosaur groups, both among saurischians and ornithischians.
And this family tree of reptiles mentions:
Archosauriformes (crocodiles, birds, dinosaurs and extinct relatives)
And later in the Mesozoic era:
The dinosaurs also developed smaller forms, including the feather-bearing smaller theropods.
The following is multiple choice question (with options) to answer.
What two basic types of feather does a bird have? | [
"flight and down",
"up and down",
"carrying and down",
"flight and landing"
] | A | Feathers help birds fly and also provide insulation and serve other purposes. Birds actually have two basic types of feathers: flight feathers and down feathers. Both are shown in Figure below . Flight feathers are long, stiff and waterproof. They provide lift and air resistance without adding weight. Down feathers are short and fluffy. They trap air next to a bird’s skin for insulation. |
SciQ | SciQ-3395 | geology, fossil-fuel, petroleum
For some transport applications, the energy density is still a winning attribute of hydrocarbons: most notably, powered flight for freight and travel.
We already have two routes to non-fossil hydrocarbons: biological sources, and direct chemical synthesis. Each involves capturing atmospheric CO2, and combining with water, to generate a blend of hydrocarbons.
Now, we already have means of creating hydrocarbons suitable for flight (e.g. Jet-A and Jet-A1 fuels). And there are already demonstration plants that have closed-loop generation of synthetic hydrocarbons, for use in electricity-grid-balancing, by using surplus electricity to synthesise methane, which is then burnt in gas turbines when required. Similarly, Tony Marmont's team have been synthesising petrol (gasoline) from air, water, and electricity.
However, none of those things mean that hydrocarbons necessarily have much of a future, beyond plastics production. Because hydrocarbon-powered aviation has a lot of environmental problems beyond just CO2 emissions, in particular it makes other contributions to exacerbating global warming. And there are lots of options for energy storage within the electricity supply chain.
The following is multiple choice question (with options) to answer.
Which fuels provide most of the world’s energy? | [
"pattern fuels",
"coal fuels",
"artificial fuels",
"fossil fuels"
] | D | Figure below shows the mix of energy resources used worldwide in 2006. Fossil fuels still provide most of the world’s energy, with oil being the single most commonly used energy resource. Natural gas is used less than the other two fossil fuels, but even natural gas is used more than all renewable energy resources combined. Wind, solar, and geothermal energy contribute the least to global energy use, despite the fact that they are virtually limitless in supply and nonpolluting. |
SciQ | SciQ-3396 | electrochemistry, redox
Please help me understand this. I have asked experts -> I am right. The common convention is to label the physical electrodes as cathode/anode based on discharge even though that will be backwards when the battery is charging. That is a poor, confusing, and illogical naming convention, but it is what it is.
The more clear and logical naming convention would be to name the physical electrodes either positive or negative since those labels apply in both charge/discharge directions. Some people use this logical naming convention, but the illogical convention seems more prevalent.
The following is multiple choice question (with options) to answer.
The cathode and anode collectively are the electrodes of what? | [
"photo cell",
"circuit cell",
"voltaic cell",
"switch cell"
] | C | One application of redox reactions requires that they be physically separated. Even though the two half reactions are physically separated, a spontaneous redox reaction still occurs. However, in this case, the electrons transfer through the wire connecting the two half reactions; that is, this setup becomes a source of electricity. Useful work can be extracted from the electrons as they transfer from one side to the other—for example, a light bulb can be lit, or a motor can be operated. The apparatus as a whole, which allows useful electrical work to be extracted from a redox reaction, is called a voltaic (galvanic) cell. Each individual system that contains a half reaction is called a half cell. The half cell that contains the oxidation reaction is called the anode, while the half cell that contains the reduction reaction is called the cathode. The cathode and anode collectively are the electrodes of the voltaic cell. Because electrons are coming from the anode, the anode is considered the negative electrode of the cell, while the cathode is considered the positive electrode of the cell. Finally, because electrons are moving from one half cell to the. |
SciQ | SciQ-3397 | biochemistry, temperature, carbohydrates
Abstract
'Resistant starch' (RS) is defined as starch and starch degradation products that resist the action of amylolytic enzymes. The effect of multiple heating/cooling treatments on the RS content of legumes, cereals and tubers was studied. The mean RS contents of the freshly cooked legumes, cereals and tubers (4.18%, 1.86% and 1.51% dry matter basis, respectively) increased to 8.16%, 3.25% and 2.51%, respectively, after three heating/cooling cycles (P< or =0.05) with a maximum increase of 114.8% in pea and a minimum of 62.1% in sweet potato (P< or =0.05). Significant positive correlations were observed between the RS content and amylose (y=0.443x-5.993, r=0.829, P< or =0.05, n=9) as well as between the percentage increase in RS and insoluble dietary fiber content (y=2.149x-24.787, r=0.962, P< or =0.05, n=9). A differential scanning calorimeter study showed an increase in the T(0), T(p), T(c) and DeltaH values of the repeatedly autoclaved/cooled starches. The intact granular structure was also observed disappear, as studied using scanning electron microscopy.
The following is multiple choice question (with options) to answer.
What part of the sweet potato store sugar from photosynthesis as starch? | [
"plants",
"skin",
"shrubs",
"roots"
] | D | Secondary growth of sweet potato roots provides more space to store food. Roots store sugar from photosynthesis as starch. What other starchy roots do people eat?. |
SciQ | SciQ-3398 | electric-circuits, potential, electrical-resistance, capacitance, batteries
Title: Physical interpretation of circuit with battery charging capacitor In the picture below, we are charging up the capacitor, by connecting it (and the resistor to a battery of voltage $V_0$, at time $t = 0$). In terms of what is happening physicially, how would you interpret the given equation $$V_0 = \frac{Q}{C} + IR?$$
Given that the potential difference accross the battery is $V_0$, and it charges the capacitor (which then has it's own potential difference $\frac{Q}{C}$), which produces an electric field along the conductors (wires) in a different direction to that of the battery, would it be correct to say that $V_0 - \frac{Q}{C}$ is then the net potential difference accross the battery which drives the current $I$. Hence using ohms law we have $V_0 - \frac{Q}{C} = IR$? Is this what is happening in this equation, or is it at least close?
Thanks. In effect, yes, that's about right. The equation is the result of applying Kirchhoff's voltage law to the circuit. This law states that the sum of the potential differences across each of the components of a given loop in a circuit should sum to zero.
In this case we have three components, the battery, the capacitor, and the resistor. The voltage across the battery is given as $V_0$. The voltage across a capacitor at any instant is equal to $\frac{Q}{C}$. And lastly, the voltage across the resistor can be expressed as $IR$. You can imagine starting the loop at the battery, at which point the potential difference is high. Then as you move around the circuit, the capacitor and the resistor work together to 'use up' the potential difference. In this way you can see that the capacitor and resistor potential differences should have the opposite sign to the battery voltage. Then, by the voltage law, we have
$
V_0 - \frac{Q}{C} - IR = 0
$
The following is multiple choice question (with options) to answer.
What is the ratio of charge on a capacitor to potential difference across it called? | [
"velocity",
"resonance",
"electromagnetism",
"capacitance"
] | D | When a capacitor is placed in a circuit, current does not actually travel across it. Rather, equal and opposite charge begins to build up on opposite sides of the capacitor --- mimicking a current --- until the electric field in the capacitor creates a potential difference across it that balances the voltage drop across any parallel resistors or the voltage source itself (if there are no resistors in parallel with the capacitor). The ratio of charge on a capacitor to potential difference across it is called capacitance. |
SciQ | SciQ-3399 | biophysics, cell-membrane
Title: Why doesn't the cell membrane just...break apart? Forgive me if this is a silly question. I can't understand the basics. Why doesn't the cell membrane just break apart? What's keeping the layers in the phospholipid bilayer together? I know that the membrane is embedded with proteins and lipids, but I still can't wrap my head around the "why". Are the hydrophobic interactions in the middle "stronger" than the hydrophilic interactions on the outside? What's keeping the individual phosphate heads together instead of, say, one of them just drifting away due to a nearby water molecule? The membrane bilayer is held together by hydrophobic forces. This is an entropy driven process. When a greasy or hydrophobic molecule is suspended in water, the water molecules form an organized "cage" around the hydrophobic molecule. When two hydrophobic molecules come into contact, they force the water between them out. This increases the entropy because the freed waters don't need to be organized into the cage. Lipid bilayers have many many many hydrophobic lipids that squeeze out a lot of water and greatly increase entropy. The polar phosphates allow the water to interact with the surface of the membrane, without a polar head group the lipids would form a spherical blob instead of a membrane.
Read this section on wikipedia for more.
The following is multiple choice question (with options) to answer.
What substances that primarily comprise plasma membranes form a bilayer? | [
"enzymes",
"phospholipids",
"steroids",
"amino acids"
] | B | Plasma membranes are primarily made up of phospholipids (orange). The hydrophilic ("water-loving") head and two hydrophobic ("water-hating") tails are shown. The phospholipids form a bilayer (two layers). The middle of the bilayer is an area without water. There can be water on either side of the bilayer. There are many proteins throughout the membrane. |
SciQ | SciQ-3400 | newtonian-mechanics, forces, kinematics, friction
Title: Why Do Objects move? Let's imagine a block resting on horizontal table. When We apply a force which is greater than frictional force it moves.
But why does this happen? Why can't friction withstand any force? As we know that one cause of friction is due to interlocking of irregularities, I think there is a opposing force as irregularities apply a normal force .
So why if applied force is increased the normal force can't withstand the increased force? Also is there any possibility that in a situation the frictional force could always cancel the applied force? Your image shows what is going on at the microscopic level between two surfaces. To understand why friction works, you have to look smaller, at the atomic level: and when you get to that point you're no longer taking about "friction" as we know it, but about physiochemical interactions between atoms and molecules. Those interactions are mediated by electromagnetic force and tend to be quite weak at the boundaries between two solid objects. As one example demonstrating the fundamentally chemical nature of the interactions, note that the reason it's easier to grip paper if your fingers are slightly damp is because the polar water molecules form bonds between your skin, the paper and each other, somewhat "gluing" everything together.
The following is multiple choice question (with options) to answer.
What type of friction is friction that acts on objects when they are sliding over a surface? | [
"rolling friction",
"spreading friction",
"sliding friction",
"static friction"
] | C | Sliding friction is friction that acts on objects when they are sliding over a surface. Sliding friction is weaker than static friction. That’s why it’s easier to slide a piece of furniture over the floor after you start it moving than it is to get it moving in the first place. Sliding friction can be useful. For example, you use sliding friction when you write with a pencil. The pencil “lead” slides easily over the paper, but there’s just enough friction between the pencil and paper to leave a mark. |
SciQ | SciQ-3401 | human-biology, nutrition
Title: Do we know a complete list of nutrients that humans must ingest to live? When the people who are making "nutritionally complete" foods like Soylent are developing their product, how do they know that they've covered all their bases? You need to have protein, carbohydrates, fats etc., but what about vitamins or minerals?
Has science produced a commonly accepted list of all the nutrients that humans need to live? For babies there is certainly a formula available for a complete menu for survival: formula*
Here are the nutrition facts from Nestlé's "Good Start":
Formula nutrition facts. source: Nestlé
Comparable lists are available for people that cannot eat normally (e.g. people in a comatose state) and are fed enteral or parenteral nutrition.
*. Remember though, breast is best :)
The following is multiple choice question (with options) to answer.
Billions of what inside the human digestive tract help us digest food, make vitamins and play other important roles? | [
"red blood cells",
"bacteria",
"viruses",
"neurons"
] | B | There are billions of bacteria inside the human digestive tract. They help us digest food. They also make vitamins and play other important roles. We use bacteria in many other ways as well. For example, we use them to:. |
SciQ | SciQ-3402 | This is possible. For given correlations among three variables $$\sigma$$, $$\tau$$, and $$\rho$$, there is a range of values that $$\rho$$ can take (within some bounds) depending on the other two correlations.
$$\sigma\tau - \sqrt{(1-\sigma^2)(1-\tau^2)} \le \rho \le \sigma\tau + \sqrt{(1-\sigma^2)(1-\tau^2)}$$
So this can make that for some data the effect of $$x$$ in a linear relation is significant for both $$b$$ and $$d$$, but still $$b$$ is not a significant effect in a linear relation for $$d$$. (In this case, when some weak correlation is present, then it might be the case that more measurements, a larger sample, will show a significant effect)
The following is multiple choice question (with options) to answer.
In a controlled scientific study, what do you call a factor that can take on different values? | [
"output",
"variable",
"vector",
"input"
] | B | An experiment is a controlled scientific study of specific variables. A variable is a factor that can take on different values. For example, the speed of an object down a ramp might be one variable, and the steepness of the ramp might be another. |
SciQ | SciQ-3403 | ecology, biogeography
Edit in response to comments
Comment about biome scale
The reason behind the scale comment is that typically we observe succession for a given habitat. Part of this stems from the origin of the succession ideas, where Frederic Clements posited that climate was the major driving factor of successional trajectories (Clements 1916). This would actually fit well with the biome view of succession, however in order for this model to explain all the variation we see in the world (eg. why a tree grows in location X but not location Y 4 metres away), you devolve into splitting the world into infinitesimally small micro-climates. Henry Gleason proposed a more individualistic model, which suggested that climate was just one influence, and that each plant species responds to a myriad of different environmental cues (Gleason 1927). The sum of these responses results in the community at a given location. This seems to fit better with our current understanding of succession but is not without problems. In a Gleasonian model, any variation can be expected to result in a different community. Since it would be strange for the pampas region to be homogeneous over 1.2 million km2, there are likely distinct communities within the biome, each developing as a result of factors like soil moisture, soil chemistry, climate, wind exposure, and herbivore use. One can still talk about succession at a biome scale, but at that scale we would be thinking about what factors lead the pampas region to become a grassland, rather than what factors lead grass X, tree Y and forb Z to coexist next to each other.
Factors maintaining grassland type ecosystems are fairly uniform globally. You need some sort of event that will kill woody vegetation but not kill grasses and forbs. Fire and grazing are natural examples (Briggs et al. 2002), but mowing would also maintain grassland (Fidelis et al. 2012). Earthquakes are unlikely to maintain grassland as trees and shrubs are likely to survive earthquakes.
Comment about global pampas
The following is multiple choice question (with options) to answer.
What is a group of similar ecosystems with the same general abiotic factors and primary producers called? | [
"population",
"ecological environment",
"biome",
"ecoculture"
] | C | Sahara Desert in northern Africa (left). Rainforest in northeastern Australia (right). Two very different biomes are pictured here. A biome is a group of similar ecosystems with the same general abiotic factors and primary producers. Both are found at roughly the same distance from the equator. |
SciQ | SciQ-3404 | geophysics, earthquakes, plate-tectonics, geography
Title: Why is the Ring of Fire there? The Ring of Fire goes through the places that have the most earthquakes. Why is the Ring of Fire there, not somewhere else?
Any help would be appreciated! This question is very similar to: Why does the "Ring of Fire" pretty much define "Pacific Rim"
The high levels of volcanoes and earthquakes are primarily due to subduction. So why is the Pacific surrounded by subduction zones?
Think back to Pangaea. This was a supercontinent that formed in the late Palaeozoic. Virtually all of the Earth's land masses were concentrated in one large supercontinent. When this broke up, the new continents moved away from each other. Fast forward 200Ma or so, and you find that the continents have moved so far apart that they are now converging on a point on the other side of the planet - the continents are moving towards each other! Hence the remains of the super ocean (which was actually multiple ocean plates - today's Pacific & Nazca plates, plus the Farrallon plate (RIP),etc ) is shrinking as the continental plates move towards it. This destruction of the ocean plate(s) occurs at subduction zones.
This is a big picture generalisation. Not all of the Pacific's boundaries are marked with subduction zones (e.g. North America has two large strike slip systems + a new spreading ridge). Also, not all of the continents are converging on each other. Africa is doing a pirouette, India is moving northwards, etc.
The following is multiple choice question (with options) to answer.
Since 1900, four of the five earthquakes of the greatest magnitude occurred near what appropriately nicknamed pacific location? | [
"ring of fire",
"seismic zone",
"quake epicenter",
"shower of fire"
] | A | Earthquakes with a magnitude in the 9 range are rare. The United States Geological Survey lists five such earthquakes on the moment magnitude scale since 1900 (see Figure below ). All but one, the Great Indian Ocean Earthquake of 2004, occurred somewhere around the Pacific Ring of Fire. |
SciQ | SciQ-3405 | thermodynamics, energy, heat, enthalpy
The equation that your teacher has given you is actually an equation for heat transfer, not for enthalpy change. However because enthalpy equals heat transfer in most cases, it is commonly said that enthalpy change also equals to that equation. However the one mistake is that there shouldn't be a minus in the equation for enthalpy change. The equation for heat transfer and enthalpy should both be the same.
The following is multiple choice question (with options) to answer.
All chemical changes involve a transfer of what? | [
"oxygen",
"fuel",
"energy",
"pressure"
] | C | Describe ways protists are important to humans. |
SciQ | SciQ-3406 | 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.
What is the most common type of capillary? | [
"ending",
"channels",
"continuous",
"large"
] | C | Continuous Capillaries The most common type of capillary, the continuous capillary, is found in almost all vascularized tissues. Continuous capillaries are characterized by a complete endothelial lining with tight junctions between endothelial cells. Although a tight junction is usually impermeable and only allows for the passage of water and ions, they are often incomplete in capillaries, leaving intercellular clefts that allow for exchange of water and other very small molecules between the blood plasma and. |
SciQ | SciQ-3407 | waves, acoustics, reflection, resonance, harmonics
Title: Are there physics, theories that predict standing wave harmonic deviations in curved tubes? For cylinders, it's widely documented how to predict the harmonic frequencies given the length of the tube, the end conditions and the speed of sound which is in turn determined by what gas is in the cylinder and at what temperature.
This principle of standing wave harmonics, resonance seems to be always illustrated, discussed in terms of straight tubes.
I suppose the tube doesn't necessarily have to be straight, that standing waves can still be excited, but also guess there is some limitation to how much curvature can be tolerated before the harmonics shift in frequency or become distorted in some manner.
Are there physics, theory that can address such deviations; equations
that take into account curvature?
I would further venture to guess something similar to what light does in a fiber - total internal reflections and the like. This paper by Felix and Delmont (2012) may be helpful.
The authors refer to a second paper which show that curved ducts have a lower inertance than their straight counterparts,
$$\mathcal{L}_{bend} = \alpha \ \mathcal{L}_{straight}$$
where
$$\alpha = \frac{\frac{1}{2} \kappa^2}{1 - \sqrt{1 - \kappa^2}}$$
with $\kappa = a/R_{0}$ describing the curvature as follows:
In the paper they outline a theoretical approach and test against experiment.
The following is multiple choice question (with options) to answer.
What is the bending of waves around a corner called? | [
"propulsion",
"diffraction",
"absorption",
"reflection"
] | B | Diffraction is the bending of waves around a corner. |
SciQ | SciQ-3408 | bond, electrons, lewis-structure, valence-bond-theory
Title: Why do unbonded electrons exist in pairs? Basically the term which we use to refer them is lone pair. In Lewis structure why we represent those unbonded electron in pairs. Like here (structure of SO2)
Here if we assume both the unbonded electrons to be existing in pairs then it's geometry will be different from what we would observe in case when both electrons exists freely (without pair).
So why we basically consider those electrons to be existing in pair? Is it any kind of observation or any theory or both?
Why unbonded electrons exits in pair
Unbonded, non-bonded or lone pair electrons are terms used to describe electrons that surround an atom, but don't play a direct role in bond formation. Importantly, these electrons do not always exist as lone pairs where the electrons reside in a common orbital. Sometimes they exist as single non-bonding electrons residing in separate orbitals.
Let's compare the non-bonding electrons in water to those in molecular oxygen. Here is an illustration of the molecular orbital arrangement for water. As we fill the orbitals with electrons according to the Aufbau Principle we arrive at the point where we have two electrons remaining and the next available molecular orbital is the $\ce{1b_1}$ orbital. According to Hund's Rule, we must place these two electrons into this orbital with their spins paired. The result is that we have two non-bonding electrons paired up in the same orbital - a lone pair of electrons.
The following is multiple choice question (with options) to answer.
In what kind of bond does one atom contribute both of the electrons in the shared pair? | [
"an ionic bond",
"a covalent bond",
"a metallic bond",
"a valence bond"
] | B | The carbon monoxide molecule is correctly represented by a triple covalent bond between the carbon and oxygen atoms. One of the bonds is a coordinate covalent bond , a covalent bond in which one of the atoms contributes both of the electrons in the shared pair. |
SciQ | SciQ-3409 | optics, visible-light, geometric-optics, optical-materials
Title: Focal plane of ideal thin lenses and spherical mirrors Recently I was studying about optical instruments and in my book I came across a point which stated that
When non axial parallel rays are incident on an ideal spherical mirror at a small angle or a parabolic mirror, the rays meet at a point on the focal plane rather than the focus point.
Also in the section about refracting telescopes, diagrams drawn show that the non axial parallel rays meet at a point on the focal plane.
Please note that I'm talking about concave mirrors and convex lenses and aberration and other non idealities are ignored.
I looked at some of the websites like this and this to understand why it is the case but an explanation is lacking everywhere.
I mean, can we show that non axial parallel rays will always converge at a point on the focal plane?
I tried to proceed by attempting to find the equation for the focal plane but I don't think that will work at all.
Could anybody please tell me a way to do this?
How do we guarantee that a group of parallel (non axial) rays incident on a spherical mirror or a lens will always converge at the focal plane (assuming ideality)?
I also saw this SE post and tried to follow the "Physics Teacher" link mentioned in comments but couldn't reach it.
Any kind of approach, either geometric or mathematical will help.
Thanks for any suggestions. This sketch may give you an idea for the case of the ideal thin lens: The ray AC will continue in a straight line (going through the center of the lens), while BD, which passes through focal point F, will refract to become parallel after the lens. Simple construction shows that the point where these lines intersect is the focal plane.
A spherical mirror M can be thought of as a part of a sphere - and when you are incident “at an angle to your mirror” you could equally say you are hitting “another part of the sphere”, mirror M’. As such, the rays would go through the “original” focal point F; if we consider the “actual” focal point F’ for the segment of the mirror at an angle, we see that F and F’ lie approximately (but not exactly) in the focal plane of M’ (cyan dashed line). I indicate the error (aberration) in my diagram with $\epsilon$.
The following is multiple choice question (with options) to answer.
Mirrors and lenses are used in optical instruments to reflect and refract what? | [
"light",
"electricity",
"mass",
"gravity"
] | A | Mirrors and lenses are used in optical instruments to reflect and refract light. Optical instruments include microscopes, telescopes, cameras, and lasers. |
SciQ | SciQ-3410 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
The zygote undergoes many cell divisions before it implants in the lining of what? | [
"pelvis",
"ovaries",
"uterus",
"vagina"
] | C | The zygote undergoes many cell divisions before it implants in the lining of the uterus. |
SciQ | SciQ-3411 | everyday-chemistry, vapor-pressure
How about using seltzer water (or Perrier? or Diet Coke!) as the source of CO2? I estimate that the pressure of CO2 is about 45 psi in the unopened bottle, and if you attach a balloon to a freshly opened bottle and let it outgas slowly, the balloon will fill up and be essentially pure CO2. If a latex balloon is unsuitable or too hard to handle, a mylar balloon ($1 at the Dollar Store) will work just as well. The gas will be saturated with water vapor.
The following is multiple choice question (with options) to answer.
What are carbonated beverages pressurized with? | [
"helium",
"co2",
"hydrogen",
"dioxide"
] | B | NaN3 is 1.847 g/cm . What is the volume of the gas produced compared to the solid reactant? Suggest a plausible reason to explain why skin burns can result from the inflation of an airbag during an automobile accident. Under basic conditions, the reaction of hydrogen peroxide (H 2O2) and potassium permanganate (KMnO4) produces oxygen and manganese dioxide. During a laboratory exercise, you carefully weighed out your sample of KMnO4. Unfortunately, however, you lost your data just before mixing the KMnO 4 with an H2O2 solution of unknown concentration. Devise a method to determine the mass of your sample of KMnO4 using excess H2O2. Carbonated beverages are pressurized with CO 2. In an attempt to produce another bubbly soda beverage, an intrepid chemist attempted to use three other gases: He, N 2, and Xe. Rank the four beverages in order of how fast the drink would go “flat” and explain your reasoning. Which beverage would have the shortest shelf life (i. , how long will an unopened bottle still be good)? Explain your answer. ♦ Urea is synthesized industrially by the reaction of ammonia and carbon dioxide to produce ammonium carbamate, followed by dehydration of ammonium carbamate to give urea and water. This process is shown in the following set of chemical equations:. |
SciQ | SciQ-3412 | sexual-reproduction
So when it's not maintained -- when there's no selection pressure on two populations -- inevitably there will be genetic drift that will randomly disrupt this fine-tuned system. If a population of, say, voles is isolated on an island, they will continue to have pressure to be able to interbreed with other voles on the island, but if they can't interbreed with those on the mainland there won't be any consequences, and so over long enough time they'll drift and lose that ability -- just as many apes, not suffering any consequences from not synthesizing vitamin C, gradually lost that ability from random drift.
There's another side to it. Two populations in the same location may be positively selected to not be able to interbreed. Think about two groups of finches, one with small fine beaks that eat tiny seeds deep inside pine cones, and one with heavy beaks that crush and eat thick-shelled nuts. They each do fine, but they can interbreed and produce offspring that have intermediate beaks -- too thick to reach the fine seeds that one parent eats, but too delicate to crush the nuts that the other parent eats. Those intermediate offspring will die off, and both parents will have wasted their resources raising them. Both parents would be better off not breeding with each other, but only breeding with their own kind to produce specialized and efficient offspring. There is now selection pressure on the birds to recognize their own kind (perhaps through songs or mating displays) and ultimately to be inter-sterile, so they never waste resources on the un-fit offspring. There's a gradation of separation over time, in which the different populations become more and more distinct. Eventually, at some arbitrary point, humans start calling them "species", but that's just us, not biology.
"Species" is an important concept, but it's not special in evolution; speciation is just one aspect of natural selection, there's nothing magical about it.
The following is multiple choice question (with options) to answer.
Which principle states that two species cannot occupy the same niche in a habitat? | [
"competitive exclusion",
"tough exclusion",
"produce exclusion",
"complete exclusion"
] | A | Competitive Exclusion Principle Resources are often limited within a habitat and multiple species may compete to obtain them. All species have an ecological niche in the ecosystem, which describes how they acquire the resources they need and how they interact with other species in the community. The competitive exclusion principle states that two species cannot occupy the same niche in a habitat. In other words, different species cannot coexist in a community if they are competing for all the same resources. An example of this principle is shown in Figure 45.24, with two protozoan species, Paramecium aurelia and Paramecium caudatum. When grown individually in the laboratory, they both thrive. But when they are placed together in the same test tube (habitat), P. aurelia outcompetes P. caudatum for food, leading to the latter’s eventual extinction. |
SciQ | SciQ-3413 | physical-chemistry, experimental-chemistry, reaction-control
Title: Why do some reactions need to be maintained at a particular temperature for prolonged periods of time? Some reactions require that temperatures of 70–100 °C to be maintained for periods of time as long as 24 hours. Why is this so? Quite simply, reactions happen faster at higher temperatures (because who likes waiting), and some may not proceed at all until heated. From a statistical viewpoint, you are giving more reactant molecules more energy, which thereby increases the number of collisions, which in turn increases the number of successful collisions (those which produce product). A typical way to attain such conditions is to place a reaction under reflux.
The following is multiple choice question (with options) to answer.
What happens to the rate of chemical reactions in higher temperatures? | [
"they increase",
"they become erratic",
"they stop",
"they decrease"
] | A | The temperature of a region is the other important part of climate. The rate of chemical reactions increases with higher temperatures. The rate doubles for every 10°C increase in temperature. Plants and bacteria grow and multiply faster in warmer areas. |
SciQ | SciQ-3414 | evolution
Add in the process of culturally modified selection pressure, and it
seems to me that even an "unfit" male would end up having a couple of
offspring. The fittest male (or female) is no better off than his or
her contemporaries because of this "leveling" effect.
"Culturally modified selection pressure", as you call it, is still selection pressure. Cultural factors can change what it means to be "the fittest" but there is no objective gold standard of "fitness". While it may be true that in modern human society, different characteristics are selected for than was the case with early Homo sapiens, this does not mean that "evolution is not occurring". On the contrary, it is occurring but perhaps it is moving in a new direction. In fact, this is essentially a circular argument. By definition, "fittest" means most likely to survive and reproduce. It does not mean strongest or fastest or prettiest. It just means whoever is better at reproducing. If that happens to be those individuals who are best at square dancing, then it is they who are the fittest.
Take the example of a modern human with diabetes. Medicine allows diabetics to lead fully productive and largely normal lives. So, perhaps diabetes is no longer a selective criterion. This does not mean that the diabetic cannot be selected for or against based on their fitness on other scales.
Whatever the selective pressure, whatever it may be that defines a "good mate", if selection is present then so is evolution. The only way to remove a species from the process of selection would be to have all (or none) individuals of each and every generation reproducing at the same rate. This is clearly not the case with humans. Surely not everyone around you has, or will have, children? There you go, selection!
UPDATE:
In answer to your comment, yes indeed, in order for a selective pressure to make itself felt and affect phenotype (at the species level), it needs to be constant across several generations. However, even the absence of selective pressure affects evolution. As others have mentioned below, active selection is not the only mechanism of evolution.
Your main question however seems to be the following: If modern society (medicine etc) allows individuals that would not survive in the wild to reproduce, how does that affect evolution? The main points in my answer, and all others here, are:
The following is multiple choice question (with options) to answer.
An alternative to inclusive fitness is group selection, a type of what scenario where small groups of organisms of the same species are effectively acting as single (perhaps colonial) organisms? | [
"evolutionary",
"molecular",
"introductory",
"combination"
] | A | Group selection A proposed alternative to inclusive fitness (sometimes known as kin selection) is the concept of group selection. In this type of evolutionary scenario, small groups of organisms of the same species are effectively acting as single (perhaps colonial) organisms. It is the reproductive success of the group (rather than individuals within the group), compared to other groups of the organism that is the basis of selection. Groups that display cooperative and altruistic traits have a selective advantage over groups that do not. Again, the mathematical analysis is similar (and it has been claimed that mathematically group and kin selection are equivalent).169 The costs of a trait must be offset by the benefits, but now the key factor is membership in a particular group (and typically, members of a group tend to be related to one another). The life cycle of the bacterium Myxococcus xanthus provides an example of this type of behavior. When environmental conditions are harsh, the cells aggregate into dense, 100 μm diameter, “fruiting bodies”, each containing ~100,000 stress resistant spores. When the environment improves, and prey becomes available, the spores are released en mass and return to active life. They move and feed in a cooperative manner through the release of digestive enzymes, which because they are acting in a quorum mode, can reach high levels.170 A well-coordinated group is expected to have a significant reproductive advantage over more anarchic collection of individuals. |
SciQ | SciQ-3415 | genetics, gene-expression, mrna, protein-expression, microarray
Postscript for the Poster
I have tried to make this answer general, to be of use to more people. As the poster is not a biologist she may still have difficulty in understanding the background to the biological experiments that generated the data she is analysing.
The biological system of interest is gene expression, which encompasses the whole series of events from transcription of genes to mRNA and their translation into protein. The background to this is that there are some genes that are (almost) always expressed, irrespective of physiological circumstances because they are needed to maintain the structure and everyday functions of the cell. This is termed constitutive expression, examples being expression of the genes for cytoskeletal actins or ribosomal proteins. Other genes are expressed (‘switched on’) only when needed (and may be termed inducible). The question here would appear to be whether the genes for the enzymes involved in DNA repair are expressed all the time (constitutively) to deal with normal ‘wear and tear’ of DNA, or whether their expression only occurs in response to some insult knwn to damage DNA, such as gamma irradiation.
As I mentioned, as an experimental scientist, one approach that can be adopted here is to look at the expression of one or two well characterized proteins that are known to be involved in DNA repair. However, there may be proteins involved in this process that you are unaware of, so the modern methods of looking at the expression of all the genes in an organism (if the DNA sequence is known) — oligonucleotide microarrays or, better, RNASeq. These methods measure relative quantities of mRNA in a cell. This is not a proxy for amount of protein or rate of its synthesis (the term ‘protein activity’ is meaningless and is not and should not be used), it is what it is, but is also a reflection of the expression of the genes that encode the mRNAs. No expression, no mRNA.
The following is multiple choice question (with options) to answer.
The complement system is a series of proteins constitutively found in the what? | [
"organs",
"nucleus",
"blood plasma",
"platelets"
] | C | Complement System The complement system is a series of proteins constitutively found in the blood plasma. As such, these proteins are not considered part of the early induced immune response, even though they share features with some of the antibacterial proteins of this class. Made in the liver, they have a variety of functions in the innate immune response, using what is known as the “alternate pathway” of complement activation. Additionally, complement functions in the adaptive immune response as well, in what is called the classical pathway. The complement system consists of several proteins that enzymatically alter and fragment later proteins in a series, which is why it is termed cascade. Once activated, the series of reactions is irreversible, and releases fragments that have the following actions: • Bind to the cell membrane of the pathogen that activates it, labeling it for phagocytosis (opsonization) • Diffuse away from the pathogen and act as chemotactic agents to attract phagocytic cells to the site of inflammation • Form damaging pores in the plasma membrane of the pathogen Figure 21.13 shows the classical pathway, which requires antibodies of the adaptive immune response. The alternate pathway does not require an antibody to become activated. |
SciQ | SciQ-3416 | nomenclature, ionic-compounds, history-of-chemistry
Title: How did Halogens become known as Halogens? They are not the only elements that form salts! Having never given it a though before, I recently discovered (in a different context) that the prefix halo- actually means 'salt' or 'sea' and the suffix -gen means 'to form' or 'to generate'. So the Halogens are the elements that 'form salts'. But there are salts that do not have halogens in them, like $\ce{Na2S}$ or $\ce{(NH4)2SO4}$. Was it known at the time that other salts existed, and what other names for this group might have been considered?
On a side note, why aren't Group I metals called halogens? Doesn't it take two to tango (I mean, to form salts?) This seems like a bit of a rhetorical question, so this isn't a terribly formal or authoritative answer, but anyhow - a lot of chemical nomenclature is like lava flow. It solidified and people just worked around it.
The halogens are so named because they have a rich chemistry of ionic compounds (fluorine through iodine, anyhow). However, both the halogens and the group I metals can form a wide range of things that aren't salts. The noble gases can form compounds with elements of low birth. The rare earth elements aren't particularly rare. Oxygen ('acid-former') is not a necessary component of acids. Technetium ('artificial' + ium) is produced in nature in significant quantities.
In addition, a lot of chemistry defies our human efforts to succintly categorise things, so at some point chemists have tried their best to find pragmatic general descriptors that unite groups of elements or molecules on the basis of the properties or constitution. The divide between organic and inorganic chemistry and the resulting exceptions and edge cases in classification (such as mellitic anhydride) is a good example of this. The map is not the territory.
The following is multiple choice question (with options) to answer.
What are cations simply named after? | [
"the scientist",
"the body part",
"the parent element",
"the cell structure"
] | C | The cations are simply named as the parent element. The sodium cation is still called “sodium. ” Often, the charge would be attached for clarity, so the sodium cation might be referred to as “sodium one plus. ”. |
SciQ | SciQ-3417 | inorganic-chemistry
Read this well written Wikipedia article: https://en.wikipedia.org/wiki/PH#cite_note-2
The following is multiple choice question (with options) to answer.
Inorganic chemistry refers to the study of materials *not* containing which element? | [
"helium",
"oxygen",
"hydrogen",
"carbon"
] | D | Inorganic chemistry is the study of chemicals that do not, in general, contain carbon. Inorganic chemicals are commonly found in rocks and minerals. One current important area of inorganic chemistry deals with the design and properties of materials involved in energy and information technology. |
SciQ | SciQ-3418 | human-biology, physiology, cardiology, anatomy
Title: Can humans live without their right atrium? The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins, and pumps it into the right ventricle through the tricuspid valve.
Can humans survive without right atrium? In this condition blood would fill the right ventricle directly, comparable to some animals like frogs, toads, snakes and lizards. What advantages does the normal human heart have to this anatomy ? If we had this anatomy, where would the best place for pacemakers be, like the sinus node? This is an interesting theoretical question, but several things would need to be clarified:
Does removing the R atrium relocate the SA node to the R ventricle or remove it completely from the picture?
Does the remaining R ventricle have a tricuspid valve?
Technically, the R atrium is the home of the sino-atrial node, which provides natural pacing of the human heart between 60-80 beats/min. Without this natural pacing, our hearts would rely on back-up pacer systems such as atrioventricular node, His-Purkinje systems or the intrinsic but ectopic pacing of individual atrial or ventricular cells.
The following is multiple choice question (with options) to answer.
How many chambers does an amphibian heart have? | [
"four",
"one",
"two",
"three"
] | D | Amphibians have a relatively complex circulatory system with a three-chambered heart. Their nervous system is also rather complex, allowing them to interact with each other and their environment. Amphibians have sense organs to smell and taste chemicals. Other sense organs include eyes and ears. Of all amphibians, frogs generally have the best vision and hearing. Frogs also have a larynx , or voice box, to make sounds. |
SciQ | SciQ-3419 | electrons, charge, quasiparticles, leptons
Title: How do electrons get a charge? Electrons belong to a group of elementary particles called leptons. There are charged and neutral leptons. And electron is the charged one. But how come it got charged?
The negative or positive charges were assigned by convention. But it is a fact that electrons are charged. My question is why electrons? and not neutrons?
Also while reading http://en.wikipedia.org/wiki/Electron, I saw that "Independent electrons moving in vacuum are termed free electrons. Electrons in metals also behave as if they were free. In reality the particles that are commonly termed electrons in metals and other solids are quasi electrons, quasiparticles, which have the same electrical charge, spin and magnetic moment as real electrons but may have a different mass ( or Effective mass - extra mass that a particle seems to have while interacting with some force )."
What does this mean? Your question touches the question of ontology in particle physics. Historically we are used to be thinking of particles as tiny independent entities that behave according to some laws of motion. This stems from the atomistic theory of matter, which was developed some two thousand years ago from the starting point of what would happen if we could split matter in ever smaller parts. The old Greeks came to the conclusion that there had to be a limit to that splitting, hence the atom hypothesis was born.
This was just a philosophical idea, of course, until around the beginning of the 19th century we learned to do chemistry so well that it became obvious that the smallest chunks that matter can be split into seemed to be the atoms of the periodic table. A hundred years later we realized that atoms can be split even further into nuclei and electrons. What didn't change was this idea that each chunk had its own independent existence.
This idea ran into a deep crisis during the early 20th century when we discovered the first effects of quantum mechanics. It turns out that atoms and nuclei and electrons do not, at all, behave like really small pieces of ordinary matter. Instead, they are behaving radically different, so different, indeed, that the human imagination has a hard time keeping up with their dynamic properties.
The following is multiple choice question (with options) to answer.
Electrons in the "outer shell" are also known as what kind of electrons? | [
"static",
"charged",
"valence",
"intermediate"
] | C | Determine the total number of valence (outer shell) electrons. For cations, subtract one electron for each. |
SciQ | SciQ-3420 | mechanical-engineering, fluid-mechanics, turbines, turbomachinery
Title: Does the turbine outlet affect the power generated by the turbine ? In my text book , it is written
"Power generated by the turbine can be increased by using a gradual expansion at the turbine outlet"
The picture below explains the meaning of gradual expansion at the turbine outlet
i.e the cross sectional area of the pipe at the turbine outlet is increasing gradually m, causing gradual expansion..
How does this thing cause the power generated by the turbine to increase ? The turbine referred to, in your text book must be a specific type of turbine, namely reaction turbine. Reaction turbines utilise mainly the pressure energy of flowing water to produce Power. The flowing fluids consist of both pressure energy(a function of fluid pressure) and kinetic energy(a function of flow velocity). The reaction turbines are rotated by the pressure difference of water on both sides of turbine blades. The reaction turbines convert most of the pressure energy to mechanical power, but they are unable to convert much of the kinetic energy in such a way. So the kinetic energy brought in by the water is left to flow away through the outlet
But if a pipe whose diameter is small at first and then increasing slowly is used at outlet, then the pressure at the pipe beginning will be lowered significantly. This happens due continuity conditions and Bernoulli's principle.
According to continuity equation if the cross sectional area of a flow decreases the flow velocity increases. But according to Bernoulli's principle if flow velocity increases the pressure decreases, given there is no change in elevation, losses, external work etc.
Thus the pressure at outlet side of turbine decreases and the pressure difference between both sides of the turbine increases. Thus the driving force increases and hence the power. So such A pipe actually converts some of the kinetic energy into pressure energy for better utilisation in reaction turbines.
Now, the water cannot flow outside if its pressure remains below atmospheric pressure. So in order to increase the pressure the diameter is increased slowly. In this case also Bernoulli's principle is utilised. The increase in diameter of the outlet pipe is kept gradual to avoid losses (eg: Eddy formation due to sudden expansion). Such pipes with gradually increasing diameters used in reaction turbines are called Draft Tubes.
The following is multiple choice question (with options) to answer.
What is created when energy turns a turbine? | [
"electricity",
"force",
"torque",
"light"
] | A | 4. Electricity is made when some type of energy turns a turbine. Explain how this happens and give two examples. |
SciQ | SciQ-3421 | star, galaxy, history, definition, stellar-structure
Title: Metallicity of Celestial Objects: Why "Metal = Non-metal"? Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium.
Note: The other elements may or may not be actual metals in the true sense of their defintion.
The following is multiple choice question (with options) to answer.
Where in the periodic table of elements are the nonmetals located? | [
"top left",
"bottom right",
"bottom left",
"top right"
] | D | As described in Section 1.7 "Introduction to the Periodic Table", the metals are on the bottom left in the periodic table, and the nonmetals are at the top right. The semimetals lie along a diagonal line separating the metals and nonmetals. In most cases, the symbols for the elements are derived directly from each element’s name, such as C for carbon, U for uranium, Ca for calcium, and Po for polonium. Elements have also been named for their properties [such as radium (Ra) for its radioactivity], for the native country of the scientist(s) who discovered them [polonium (Po) for Poland], for eminent scientists [curium (Cm) for the Curies], for gods and goddesses [selenium (Se) for the Greek goddess of the moon, Selene], and for other poetic or historical reasons. Some of the symbols used for elements that have been known since antiquity are derived from historical names that are no longer in use; only the symbols remain to remind us of their origin. Examples are Fe for iron, from the Latin ferrum; Na for sodium, from the Latin natrium; and W for tungsten, from the German wolfram. Examples are in Table 1.4 "Element Symbols Based on Names No Longer in Use". As you work through this text, you will encounter the names and symbols of the elements repeatedly, and much as you become familiar with characters in a play or a film, their names and symbols will become familiar. |
SciQ | SciQ-3422 | history, autoimmune, diabetes-mellitus
Title: When was it determined that Type 1 Diabetes is an autoimmune disease? I just found out today that type 1 diabetes is an autoimmune disease. When was this discovered? This question has two answers: The difference was first described in 1936 by Harold Percival Himsworth, which described it in this article.
At this time it was established that there are two forms of Diabetes, one sensitive to insuline while the other is not.
The terms Diabetes type 1 and 2 where established somewhere between 1974 and 1976, for details see the review "The discovery of type 1 Diabetes".
The following is multiple choice question (with options) to answer.
How many different main types of diabetes are there? | [
"three",
"ten",
"two",
"four"
] | C | |
SciQ | SciQ-3423 | zoology, ecology, species-distribution, migration
Title: How do animals end up in remote areas? I was thinking specifically about random marshy water holes on farmers fields. It seems that you can visit just about any one of these and you will find frogs if you look hard enough.
They usually don't seem to be connected to each other. If it were any other land animal I would figure they walk from one spot to another, but in the case of frogs, I don't imagine their range is very vast. But often these marshy spots can be separated by fairly large distances to a frog.
So this brings me to my question: how do each of these spots end up with frogs in them? I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it? This question pertains to organism dispersal, which is a very active field of study with relation to it's impact on conservation efforts. Much of what I will say below has been covered in this wiki.
Definition: From the Wiki
Technically, dispersal is defined as any movement that has the
potential to lead to gene flow.
It can be broadly classified into two categories:
Density dependent dispersal
Density independent dispersal
The question of frogs and fishes both refer to Density independent dispersal, while an example of density independent dispersal can be the competition for habitat space between big cats and humans (this is a WWF pdf)
From the wiki:
Density-independent dispersal
Organisms have evolved adaptations for dispersal that take advantage
of various forms of kinetic energy occurring naturally in the
environment. This is referred to as density independent or passive
dispersal and operates on many groups of organisms (some
invertebrates, fish, insects and sessile organisms such as plants)
that depend on animal vectors, wind, gravity or current for dispersal.
Density-dependent dispersal
Density dependent or active dispersal for many animals largely depends
on factors such as local population size, resource competition,
habitat quality, and habitat size.
Currently, some studies suggest the same.
This study in particular studied the movement and habitat occupancy patterns within ephemeral and permanent water bodies in response to flooding. They found that during flooding these frogs moved out to flooded ephemeral water bodies and later on moved back again to the permanent ones.
Other suggested readings for those highly interested in the subject may include this (a phd thesis) and this (a project report)
The following is multiple choice question (with options) to answer.
Where do most amphibians live, salt water or fresh water? | [
"deserts",
"saltwater",
"aquariums",
"fresh water"
] | D | Most amphibians live in fresh water, not salt water. Their habitats can include areas close to springs, streams, rivers, lakes, swamps and ponds. They can be found in moist areas in forests, meadows and marshes. Amphibians can be found almost anywhere there is a source of fresh water. Although there are no true saltwater amphibians, a few can live in brackish (slightly salty) water. Some species do not need any water at all, and several species have also adapted to live in drier environments. Most amphibians still need water to lay their eggs. |
SciQ | SciQ-3424 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
Foliation, which forms layers in rocks during metamorphism, is caused by what? | [
"Pulling",
"push",
"power",
"pressure"
] | D | During metamorphism a rock may change chemically. Ions move and new minerals form. The new minerals are more stable in the new environment. Extreme pressure may lead to physical changes like foliation . Foliation forms as the rocks are squeezed. If pressure is exerted from one direction, the rock forms layers. This is foliation. If pressure is exerted from all directions, the rock usually does not show foliation. |
SciQ | SciQ-3425 | material-science, physical-chemistry
Title: Melting and Boiling Points of Odd Materials In Chemistry, I was taught that there are three main states of matter: solid, liquid, and gas, and that heat and pressure determine that state. For some substances, the line is blurry between them.
Some materials don't seem intuitively to do this--nor have I been able to find data on them. For example, what is a reasonable estimate of a melting point for brick? What is the boiling point of paper? When will a carpet sublimate?
The common theme seems to be that these are all composite materials. Certainly all the elements have melting points (as applicable) and boiling points. Many compounds do too. However, something like cardboard is a mixture of fiber, glue, pigment, and possibly other things. Each of these might be made up of several compounds, with each compound having its own boiling point.
My suspicion is that for composite materials, individual compounds would exhibit properties roughly individually--so to melt wood, the water would boil off first, and then maybe it would start melting into a glucose-protein slag. Is this truly the right idea for what happens? This is an interesting question, because there is no simple answer - many different things are going on. A quick answer is that many materials don't exhibit clear melting points because heating turns them into something else before they can melt. Here are a couple of examples:
Generally, pure substances have simple, well-defined melting and boiling points. But there are many exceptions. A key example is gypsum - CaSO4 . 2H2O - calcium sulfate dihydrate. When it's heated, it first dehydrates in two steps. Initially it loses 1.5 of the water molecules as vapor, then in a second phase it loses the last 1/2 water molecule as vapor. When this dehydration is complete, the remaining compound is not the compound that we started with - it is now CaSO4. And if heating is continued, much of the CaSO4 will decompose - producing CaO (solid) and SO3 (vapor). Eventually, some melting will be observed, but the melted material will actually be a mixture of CaO and CaSO4.
The following is multiple choice question (with options) to answer.
What type of compounds tend to have high melting points and boiling points? | [
"particle",
"ionic",
"liquid",
"soluble"
] | B | Ionic compounds tend to have high melting points and boiling points. |
SciQ | SciQ-3426 | plate-tectonics, crust, mantle, cavern
Title: How likely are caverns inside the mantle? Almost everyone wrongly assumes that the Earth's mantle is liquid, but it isn't (only the outer core is). Is it possible then that there are hollow spaces within the mantle, similar to caves in the crust? What could they look like and up to how much of the mantle could be hollow? What might be inside mantle caverns? Would they be filled with gas or rather vacuum? It is extremely unlikely that any hollow volumes exist in the mantle.
The mantle is a convecting solid which can deform over long timescales. Let's assume that such a cavern did somehow form. Whatever it is filled it, would be of lower density than the surrounding rock. It would slowly rise upwards through the solid-yet-deformable mantle until it reaches a place where the rocks are brittle, not ductile. That place is the crust. And as you know, the crust is full of caverns and there is no problem with that.
The following is multiple choice question (with options) to answer.
What is the molten material deep within the earth? | [
"magma",
"volcanic mass",
"crystals",
"lava"
] | A | Cooling and forming crystals. Deep within the Earth, temperatures can get hot enough to melt rock. This molten material is called magma. As it cools, crystals grow, forming an igneous rock. The crystals will grow larger if the magma cools slowly, as it does if it remains deep within the Earth. If the magma cools quickly, the crystals will be very small. |
SciQ | SciQ-3427 | rotational-dynamics, reference-frames
Now suppose that the particles are indeed stuck together to form a rigid body. We see that the body is moving so that: 1) the CofM remains fixed, 2) all the distances between the particles are fixed. (This second condition is what is meant by a $rigid$ body after all).
A motion with these two properties, (1) and (2), is precisely what is meant by the phrase ``a rotation about the CofM''
The following is multiple choice question (with options) to answer.
Objects in motion that return to the same position after a fixed period of time are said to be in what type of motion? | [
"dynamic",
"harmonic",
"curving",
"circular"
] | B | Objects in motion that return to the same position after a fixed period of time are said to be in harmonic motion. Objects in harmonic motion have the ability to transfer some of their energy over large distances. They do so by creating waves in a medium. Imagine pushing up and down on the surface of a bathtub filled with water. Water acts as the medium that carries energy from your hand to the edges of the bathtub. Waves transfer energy over a distance without direct contact of the initial source. In this sense waves are phenomena not objects. |
SciQ | SciQ-3428 | everyday-life, torque, power, combustion
Title: Does the depth that the accelerator pedal is depressed correspond more closely to the force or the power that the engine delivers to a car? Consider a car that only moves directly forward without turning (so that we can model its trajectory as motion in one dimension), and assume we can neglect both air resistance and the frictional torque on the axle, so that its trajectory is determined solely by its engine (i.e. it doesn't brake). The engine exerts a force $F(t)$ on and delivers a power $P(t)$ to the car. Supplemented with initial conditions, either of these two functions determines the car's trajectory $x(t)$ via the differential equations $m \frac{d^2x}{dt^2} = F(t)$ or $F(t) v(t) = m \frac{d^2x}{dt^2} \frac{dx}{dt} = P(t)$.
For real-world car designs, if the accelerator pedal is depressed by a fixed amount, does that correspond to the engine delivering a fixed force/torque or a fixed power to the car? I assume that the force/power delivered to the car may in general be a nonlinear, though monotonic, function of the depression angle, but let's eliminate that complication by assuming that the pedal depression is held fixed over time. Does this more closely correspond to $F(t) = $ const. or $P(t) = $ const.? (I assume in real life it's very complicated because there are a lot of effects at play and neither approximation is exact, but I suspect that one of them is reasonably accurate. Also, if we consider the engine in isolation then it's more natural to talk about its delivered torque than force, but I'm holding the rest of the car design constant so that we can lump all those car-specific details into a fixed effective axle radius that converts between the two quantities.)
If it's fixed force $F_\text{engine}$, then we get uniformly accelerator motion at constant acceleration $a = F_\text{engine}/m_\text{car}$.
But if it's fixed power $P_\text{engine}$, then we get
$$\begin{align*}
The following is multiple choice question (with options) to answer.
What function of the car is affected by the pedal that controls the amount of gas the engine gets? | [
"braking",
"acceleration",
"shifting",
"transmission"
] | B | The car pedal on the right controls the amount of gas the engine gets. How does this affect the car’s acceleration?. |
SciQ | SciQ-3429 | electrons, nuclear-physics, atomic-physics, protons, binding-energy
Title: Why can atoms only gain or lose electrons and not protons? I know that an object can become net negative or net positive by losing or gaining electrons, and having more or fewer protons than electrons but why can't protons be transferred too? The energy required to remove an electron from an atom is called its ionization energy. Typical ionization energies are five or ten electron-volts. A visible-light photon carries an energy somewhere under $\rm3\,eV$ and cannot ionize most free atoms. There is enough ultraviolet light in sunlight that atoms on Earth can be preferentially ionized during the daytime, which drives lots of interesting chemistry. However typical temperatures on Earth $(T=\rm300\,K$, $k_BT = \frac{1}{40}\rm eV)$ are low enough that atoms typically don’t ionize spontaneously. The relative stability of atoms against ionization allows stable molecules to exist.
The energy required to remove a proton from a nucleus is called the proton separation energy. Typical proton separation energies are five or ten million electron-volts. In an environment where proton separation was happening, there would be so much energy kicking around that all of the nuclei would be completely ionized, with no bound electrons at all. If you, a biological person made of molecules like DNA and protein, were to visit such an environment, you wouldn’t be made of molecules any more after your visit, and you would therefore have forgotten your question.
It’s not that protons can’t be transferred. It’s just that if we lived in a place where proton transfer was common, we would have a very different perspective on chemistry.
You may actually be aware of some consequences of one nucleon-transfer reaction. Energetic radiation from outer space can cause spallation when interacting with the Earth, either with the atmosphere or with the heavier nuclei under Earth’s surface. Some of the spallation products are free neutrons, which thermalize and behave like a (very tenuous) component of Earth’s atmosphere. The most common species in the atmosphere is nitrogen-14, which interacts with thermal neutrons by
$$
\rm
^{14}N + n \to p + {}^{14}C
$$
The following is multiple choice question (with options) to answer.
An atom that gains or loses electrons is called what? | [
"ion",
"isotope",
"photon",
"quark"
] | A | An atom that gains or loses electrons is an ion. |
SciQ | SciQ-3430 | machine-learning, statistics
Title: How to test hypothesis? I have a table named app_satisfaction which has user_id, satisfaction, # of people they've invited.
I've grouped by satisfaction and found that on averge.
people in satisfaction ="BAD" group invted 2.25 people,
"GOOD" group invited 2.09 people, and
"EXECELLENT" group invited 1.89 people.
So my hypothesis is people who dislike the app are more likely to invite people since inviting people gives them free coupon and they do not like to spend their own money on app they dislike.
I have a problem, just by looking at average invite in each group it seems unreasonable to draw conclusion. Also there are more people in "GOOD", "EXCELLENT" group compared to "BAD" group.
How can I test my hypothesis? what are the approaches one might take in real world problems? As far as I understand, you have factors ("bad, "good" etc) and continuous "invitations". If you want to compare two groups you could use a t-test (e.g. Wilcoxon). If you want to compare all of the groups, you could use a simple linear regression of form:
$$ invitations = \beta_0 satisfaction_1 + \beta_1 satisfaction_2 + ... + u.$$
R example:
library("e1071")
iris = iris
table(iris$Species)
#iris = iris[!(iris$Species=="versicolor"),]
library(dplyr)
iris %>%
group_by(Species) %>%
summarise_at(vars(Sepal.Length), funs(mean(., na.rm=TRUE)))
Result (means):
# A tibble: 3 x 2
Species Sepal.Length
<fct> <dbl>
1 setosa 5.01
2 versicolor 5.94
3 virginica 6.59
Compare two groups:
# Two-samples Wilcoxon test
wilcox.test(iris$Sepal.Length[iris$Species=="setosa"], iris$Sepal.Length[iris$Species=="virginica"])
# The p-value is less than the significance level alpha = 0.05. We can conclude that Sepal Length is significantly different
The following is multiple choice question (with options) to answer.
What do you require to test a hypothesis? | [
"conclusion",
"estimates",
"data",
"opinion"
] | C | Testing a hypothesis requires data. Data can be gathered by observations or by experiments. |
SciQ | SciQ-3431 | thermodynamics, energy, work, entropy
Title: Proof of $dE = T dS − P dV + µdN$ I'm following this book. The author states The First Law of Thermodynamics as follows:
$$dE = đQ + đW + đC$$ , (3.50)
where
– đQ = energy put into the system thermally by an environment, such
as a stove;
– đW = mechanical work performed on the system by forces arising
from pressure, electromagnetism, etc.;
– đC = energy brought into the system, either by particles that arrive
as a result of environmental changes, or by the environment itself.
This includes large-scale potential energy, such as that due to gravity
when we are treating a large system such as an atmosphere.
where $dE$ is the infinitesimal increase in a system’s internal energy.
Then he goes on to replace $đQ$ with $TdS$ using the following argument:
In Section 3.8 we found that entropy is extensive: the total entropy of a
set of interacting systems is always the sum of the systems’ individual entropies, even though this total entropy grows as the systems evolve toward
equilibrium. Indeed, at constant volume and particle number (i.e., for thermal interactions only), the First Law says $dE = đQ$, whereas (3.141) says
$dE = T dS$. We infer that $T dS$ is the desired replacement for $đQ$ that makes
for an exact-differential-only quasi-static version of the First Law. Replacing the “heat into the system”, $đQ$, with $T dS$ is something that we already
saw and used in the discussion around Figure 3.13. We might replace dE
with $đQ$ in that discussion and observe that, whereas we certainly can write
$đQ_1 = T_1 dS_1$ and $đQ_2 = T_2 dS_2$
, we cannot write “$đQ = T dS$” for the entire
evolving system. So, the quasi-static version of the First Law using only exact
differentials applies individually to each subsystem, but not to the combined
system, because it is only the subsystems that are always held very close to
equilibrium.
The following is multiple choice question (with options) to answer.
The first law of thermodynamics deals with the total amount of energy in what? | [
"organism",
"springs",
"galaxy",
"universe"
] | D | Only radioactive isotopes have half-lives. |
SciQ | SciQ-3432 | geography, mantle, crust, mining, cavern
6.Record absolute depth under sea level a person has reached "on foot".
If you consider Vescoso to have been "on foot", he wins again. If not, and you consider miners going to their jobs as being "on foot", then it would be the Canadian miners (2.65 km below see level). If you are strict against both, my first thougth is then maybe port workers (note a submariner won't win in this case neither), or maybe a spelunker, but user Semidiurnal Simon clarifies it on comments. I was wrong (I said I made the estimations quickly) as: "For the strictest "on foot", it won't be port workers, it'll be somebody in a below-sea-level basin (e.g. by the Dead Sea), or possibly a low-altitude mine that has a drift (slanted corridor) entry and so doesn't require an elevator."
7.Record absolute depth under surface by drilling.
Sending machines from the surface (by borehole) rather than humans, the Kola Superdeep Borehole is the deepest (12km).
8.Record closest drill to Earth's Center.
The Ocean Drilling Program could have this record, but I cannot determine where. Average seabed deep rounds -4.000 m. and the Arctic Ocean is not a deep ocean in comparison with the Pacific and Atlantic. So the Kola Borehole may well have this record too.
The following is multiple choice question (with options) to answer.
What type of vehicles is able to go to the deepest ocean floor? | [
"remote-control vehicles",
"autonomous controlled airplanes",
"all-terrain vehicles",
"off road vehicles"
] | A | Today, remote-control vehicles, called remotely operated vehicles (ROVs) go to the deepest ocean floor. They don’t have any people on board. However, they carry devices that record many measurements. They also collect sediments and take photos. |
SciQ | SciQ-3433 | newtonian-mechanics, water, rotation, speed, inertia
Title: Warship cannons influence on speed/direction I've been looking at great warships like the Iowa or equivalent ww2 warships, and I raised question.
This kind of war is pretty much only about strategic placements, accuracy and fire power. Hence the race to stack as many cannons as possible. Manage weight and size for manoeuverability vs fire power and range for example. And in the end it's all about having each ship perform it's specific role.
And with all that i was simply wondering if all the cannons would actually influence the ship's speed/heading each time they're fired. In one hand they're pretty massive, on the other hand the boat is pretty heavy and wide.
Would a 45 degree shot actually help the ship turn ? Or 180 give a small speed increase ? Would that be actually used to be more manoeuverable ? That would be pretty cool :o
I am sure there is some kind of influence, the ship won't obviously stay static, but I was wondering how much. Would it actually turn the ship say, 10 deg each time it fires or more something like 0.2. (For example). Anyway, my curiosity strikes again ! To answer your questions, would a 90 degree shot turn the ship, in theory yes, due to the conservation of angular momentum law. As long as the cannon was not exactly amidships , in which case it would push, or more probably just cause a list, to port or starboard.
And would a 180 degree shot (aftwards) increase the speed of the ship, again, in theory yes, due to the conservation of linear momentum law.
But in practice, how much effect they would have depends on ratio of the momentum of the ship (mass by velocity) versus the momentum of the shell, as well as other factors. The smaller this ratio, which would be pretty small in the first place, unless the cannon were all fired simultaneously, the more difficult it would be to measure.
You should think of having a go at this yourself.
Lots of great physics in it.
Variables : mass of ship, momentum of cannon shell, density of water, water viscosity etc.
The following is multiple choice question (with options) to answer.
What is the turning effectiveness of a force? | [
"velocity",
"gravitational pull",
"intake",
"torque"
] | D | • Torque is the turning effectiveness of a force. In this case, because F is perpendicular to r , torque is simply we multiply both sides of the equation above by r , we get torque on the left-hand side. That is, rF = mr 2α. |
SciQ | SciQ-3434 | taxonomy, mammals, cladistics
Title: Why aren't mammals and reptiles considered amphibians? We've all heard it: birds descend from dinosaurs, so they're dinosaurs too. But this got me thinking: doesn't this mean that, for instance, all terrestrial vertebrates – including humans – are technically fish? A recent video by MinuteEarth and the Wikipedia article for "Fish" confirmed my shower thought hypothesis.
Interesting. But... all amniotes, i.e. reptiles (and, by extension, birds) and mammals, descend from amphibians, right? If so, then why aren't they considered amphibians too? Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend from Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).
The following is multiple choice question (with options) to answer.
What are the 3 orders of amphibians? | [
"bees, caddisflies, antilions",
"frogs, salamanders, caecilians",
"monotremata, artiodactyla, rodentia",
"hagfish, lampreys, acanthodii"
] | B | There are only about 6200 known species of amphibians. They are placed in three orders: frogs, salamanders, and caecilians. Table below shows a picture of an amphibian in each order. It also provides additional information about the orders. |
SciQ | SciQ-3435 | gas-laws, vapor-pressure, humidity
$$PV=nRT$$
What would I had use as the total pressure? Therefore I'm trapped. Is there any way to find what it is being asked?
Edit:
Following the indications by the answer I did the following:
The number of moles of water vapor at $\pu{30 ^\circ C}$ can be found from using the equation of ideal gas:
$\left(0.9\times 32\,mmHg\right)(6.24\,L)=n_{water}(62.4\frac{mmHg\cdot L}{mol\cdot K})(30+273)K$
$n_{water}=0.009505\,mol$
Then the number of moles of water vapor at $\pu{27 ^\circ C}$:
$\left(27\,mmHg\right)(6.24\,L)=n_{water}(62.4\frac{mmHg\cdot L}{mol\cdot K})(27+273)K$
$n_{water}=0.009\,mol$
Then:
$\Delta n_{water}=0.009505-0.009=0.000505\,mol$
From this quantity the grams of water and volume can be obtained using density of water and the formula weight.
$V=0.000505\,mol\times\frac{18\,g}{1\,mol\,\pu{H_{2}O}}\times\frac{1\,mL}{1g}=0.009090\,mL$
The following is multiple choice question (with options) to answer.
The sum of the pressures of the hydrogen and the water vapor is equal to what? | [
"adjacent pressure",
"moon pressure",
"precipitation pressure",
"atmospheric pressure"
] | D | The atmospheric pressure is converted from kPa to mmHg in order to match units with the table. The sum of the pressures of the hydrogen and the water vapor is equal to the atmospheric pressure. The pressure of the hydrogen is found by subtraction. Then, the volume of the gas at STP can be calculated by using the combined gas law. |
SciQ | SciQ-3436 | respiration
Here is what happens at the molecular level.
The $\rm CN^-$ ions diffuse into the mitochondria. They have high affinity to the ferrous ion of the mitochondrial enzyme cytochrome c oxidase involved in the electron transport chain (ETC), one of the phases of cellular respiration where $\rm ATP$ is generated from $\rm NADH$ and $\rm FADH_2$. And it is this process that actually requires oxygen. The inhibited cytochrome c oxidase is of no good in transporting electrons, thus no $\rm ATP$ molecules are generated. The oxygen molecules waiting for those electrons remain empty handed resulting in the increase in the concentration of molecular oxygen. Remember, ETC occurs in almost all living cells except a few like RBC which get their major share of ATP from the highly inefficient anaerobic glycolysis. Also, $\rm ATP$ is the energy currency of our body and is required in a wide variety of bodily processes like osmotic balance, nerve impulse transmission, muscle contraction etc. With no $\rm ATP$ your heart and respiratory muscles can't contract, your medulla can't regulate breathing, your kidneys can't concentrate urine and the list goes on. Death is imminent if a high concentration of cyanide gets into your blood.
The symptoms of panic like tachypnea and tachycardia (that result due to low oxygen in blood) are not usually seen unless the victim himself knows he is poisoned. The end effects like cardiac and respiratory arrest, seizures and coma, however, are similar to those of suffocation.
For further read:
The Mechanism of Cyanide Intoxication and its Antagonism
The following is multiple choice question (with options) to answer.
What is cellular respiration that proceeds in the presence of oxygen known as? | [
"aerobic respiration",
"digestive respiration",
"anaerobic respiration",
"kinetic respiration"
] | A | Cellular respiration that proceeds in the presence of oxygen is aerobic respiration. |
SciQ | SciQ-3437 | metabolism, human-anatomy, pharmacology, liver
Title: Circulation through the liver in light of drug metabolism I have a lingering question which stems from an answer that I gave to What hydrolyses aspirin within the digestive tract and blood stream?
When a drug or any other substance is absorbed into the bloodstream in the stomach or small intestine, it ultimately passes through the hepatic portal vein and into the liver sinusoids, where it is processed by hepatocytes and introduced into the general circulation via the vena cava. In terms of metabolism, this is what causes a "first-pass" effect for drugs that are ingested.
For drugs that are delivered either by intravenous, intramuscular, or sub-lingually (as in the other Biology.SE question), this first-pass effect is avoided, and the drug is introduced into the general circulation without being metabolized by the liver first.
Even though the first pass is avoided, the blood in the body still makes its way back through the liver eventually via the hepatic artery, which is a branch off of the celiac artery.
The issue I still have is, does the incoming blood from the hepatic artery merge with the blood from the hepatic portal vein? If not, does the blood from the hepatic artery still interact with the hepatocytes in some way? (it makes sense that it does, and I have also read that one of the main functions of the hepatic artery was to deliver blood supply for the liver's metabolic needs) If this is not the case, where in the body would these drugs that were introduced via IV, etc., be metabolized? Yes, the blood from the hepatic artery (proper) and the portal vein mix in the sinusoids of the liver. The hepatic vein supplies about 75% of the blood to the liver, and the hepatic artery the remaining 25%. Because the portal vein provides such a large part of the blood supply to the liver, then any disease that causes the blood to build up can cause portal hypertension.
The hepatic artery carries oxygen-rich blood from the heart. The portal vein is part of the portal system and connects the capillary beds of the gastrointestinal tract to those of the liver. Because of the larger volume through the portal vein, I think that each vessel carries about half the oxygen supply to the liver.
The following is multiple choice question (with options) to answer.
Blood enters the kidney through the which artery? | [
"cardiac artery",
"renal artery",
"jugular",
"vas deferens"
] | B | Blood enters the kidney through the renal artery , which branches into capillaries. When blood passes through capillaries of the glomerulus of a nephron, blood pressure forces some of the water and dissolved substances in the blood to cross the capillary walls into Bowman’s capsule . |
SciQ | SciQ-3438 | thermodynamics, energy-conservation, electrical-resistance, power
The thing is, when I then try some simple model like using specific
heat (I used the old thing from first year chemistry $Q = mc\Delta
> T$)I get rather large numbers for temperature increase, on the order
of thousands of degrees for a 120 V circuit.
The following is multiple choice question (with options) to answer.
Besides increasing the potential, how else can you increase current in a circuit? | [
"decreasing the heat",
"increasing the resistance",
"decreasing the resistance",
"increasing the heat"
] | C | There are two ways to control the current in a circuit. Since the current is directly proportional to the potential difference and inversely proportional to the resistance, you can increase the current in a circuit by increasing the potential or by decreasing the resistance. |
SciQ | SciQ-3439 | 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 kingdom in the domain eukarya that includes molds, mushrooms, and yeasts called? | [
"bacteria",
"proteins",
"acids",
"fungi"
] | D | Fungi are a kingdom in the domain Eukarya that includes molds, mushrooms, and yeasts. |
SciQ | SciQ-3440 | physical-chemistry, hydrogen-bond
Title: Volatile nature due to hydrogen bonding Why does intramolecular hydrogen bonding make an organic (or possibly inorganic as well(?)) compound volatile.
What I think is that it might be due to decrease in the solubility of the compound as intermolecular hydrogen bonding cannot be done after that. "Volatile" usually refers to ease of evaporation, high vapor pressure, so it is a property of a pure substance while solubility is a property of the combination of two or more substances.
An intramolecular hydrogen bond makes a compound more volatile because the charge imbalances are offset internally instead of by forming an interaction with another molecule.
Interactions between different molecules of the substance would lower volatility, but intramolecular hydrogen bonds prevent the hydrogen bond donor and acceptor of one molecule from interacting with another molecule.
The following is multiple choice question (with options) to answer.
An excellent solvent that holds heat well and allows hydrogen bonds, what substance has many properties critical to life? | [
"water",
"blood",
"liquid",
"plasma"
] | A | 2.2 Water Water has many properties that are critical to maintaining life. It is polar, allowing for the formation of hydrogen bonds, which allow ions and other polar molecules to dissolve in water. Therefore, water is an excellent solvent. The hydrogen bonds between water molecules give water the ability to hold heat better than many other substances. As the temperature rises, the hydrogen bonds between water continually break and reform, allowing for the overall temperature to remain stable, although increased energy is added to the system. Water’s cohesive forces allow for the property of surface tension. All of these unique properties of water are important in the chemistry of living organisms. The pH of a solution is a measure of the concentration of hydrogen ions in the solution. A solution with a high number of hydrogen ions is acidic and has a low pH value. A solution with a high number of hydroxide ions is basic and has a high pH value. The pH scale ranges from 0 to 14, with a pH of 7 being neutral. Buffers are solutions that moderate pH changes when an acid or base is added to the buffer system. Buffers are important in biological systems because of their ability to maintain constant pH conditions. |
SciQ | SciQ-3441 | geophysics, seismology, core
Title: Why does seismic activity shed light on the inner core rigidity? Reading Introduction to Geology (MIT 2005) and Wikipedia's article on Earth's inner core, it is specified that:
Earth was discovered to have a solid inner core distinct from its liquid outer
core in 1936, by the seismologist Inge Lehmann, who deduced its presence from observations of earthquake-generated seismic waves that reflect off the boundary of the inner core and can be detected by sensitive seismographs on the Earth's surface.
Why does seismic activity would result in the conclusion that the inner core is rigid? What is the link between seismism and inner core? The question that Azzie Rogers linked to: How can we determine the size and composition of Earth's inner core?
Does answer the theory part of the question, but I will extrapolate a little more to answer the question.
The question becomes, what kind of waves travel through what? Both shear and compressional seismic waves can travel through solids, but as it turns out, you cannot shear a liquid. As you look at teleseismic raypaths (waves traveling far from the source) you can see that the wave must travel deep into the earth and then back up again. The wave forms, and directions of these wavepaths will be altered by the different compositions of Earth's layers as it travels through: a wave just traveling through the mantle will have both its shear and compressional component. A wave traveling through the mantle and outer core will lose its original shear component, and either develop a new one as it leaves the core (but distinct from the wave that travels through the mantle only) or not have one at all. And finally, a wave that travels through the mantle, outer core and inner core will have distinct wave patters as well. Its by this comparison of waveforms that we realize that the earth not only has different compositional layers, but phase boundaries as well. I am not sure seismology alone would lead to a solid inner core, but there is abundant evidence supporting that fact. When you combine Seismology, rare bits of geochemistry, the calculation of Earth's gravity , and perhaps the most important part, the magnetic dynamo generating our magnetic field, we see a fairly clear ( albeit incomplete) story.
The following is multiple choice question (with options) to answer.
Which part of the earth is made of the rigid, brittle, solid crust and uppermost mantle? | [
"troposphere",
"lithosphere",
"atmosphere",
"thermosphere"
] | B | The lithosphere is made of the rigid, brittle, solid crust and uppermost mantle. |
SciQ | SciQ-3442 | # Mathematical Physics: Differential equation of a raindrop
I hope this is a suited question for this site since it contains a mix of physics and mathematics. In case I should post this on the physics stackexchange site, please let me know.
A spherical raindrop is falling from the sky. Because of the humid atmosphere the raindrop will gain mass during his fall. The increase in mass per time is proportional to the current surface area.
1. Find an equation for the radius of the drop as a function of time ($r(t)$). ($r(0) =r_0$)
2. Find and solve the equation of motion for the raindrop. The equation of motion should depend on $r_0$
My work so far:
Mass: $m(t)=\frac{4}{3} \pi r(t)^3 \rho$
Sufrace Area: $A(t)=4\pi r(t)^2$
\begin{aligned} & \implies \frac{dm(t)}{dt}=\frac{d}{dt}(\frac{4}{3}\pi r(t)^3 \rho)=4 \pi r(t)^2 r'(t)\rho\\ & \iff 4 \pi \rho r(t)^2 r'(t)=\lambda 4 \pi r(t) ^2 \iff r'(t)=\frac{\lambda}{\rho} \iff \frac{dr}{dt}=\frac{\lambda}{\rho} \\ & \iff \int dr = \frac{\lambda}{\rho} \int dt \iff r(t)=\frac{\lambda}{\rho}t+c \\ & \color{blue}{\implies r(t)=\alpha t+r_0} \space \space \space \space \space \space \space \space \space \space \space \text{where}\space \space\alpha=\frac{\lambda}{\rho} \end{aligned}
Equation of motion:
Gravitational Force: $mg$
The following is multiple choice question (with options) to answer.
What is liquid water falling from the sky called? | [
"clouds",
"evaporation",
"snow",
"rain"
] | D | |
SciQ | SciQ-3443 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
The two general functions of roots in plants are to anchor and to do what else? | [
"grow",
"absorb",
"generate",
"photosynthesis"
] | B |
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