source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-6344 | redox
Title: Is it possible to write a redox reaction with two oxidations and one reduction together? Let's take the Redox reaction between ${MnO_4}^-, {C_2O_4}^{2-}$ and ${SO_3}^{2-} $
Is it possible to write the complete reaction as below or do I need to consider the two reactions separately?
$\ce{4MnO4- + 5C2O4^{2-} + 5SO3^{2-} -> 4Mn^2+ + 10CO2 + 5SO4^{2-}}$ I wouldn't try to combine these reactions. You would want to consider both reactions and maybe look up the standard reduction potentials of all reactants and products involved to give yourself an idea of what is oxidizing what and what is reducing what. In general, you should let the SRP's be a guide for trying to figure out what actually happens in these reactions.
The reaction you wrote doesn't really describe anything chemically. We have to make sure not only the math works out, but also the chemistry. Also, your charge balance is wrong, so even if the chemistry did work out, the reaction would be impossible. You seem to have 24 (-) on the reactants side and net 2 (+) on the products side.
Remember to always check BOTH your mass (MB) and charge balance (CB) work out when you're doing REDOX problems.
The following two reactions are the acidic balanced REDOX reactions for the the species you have written. Of course, these may not actually be the real reactions that would occur. For that, you would have to look things up in tables in your book.
$\ce{6 H+ + 2MnO4- + 5SO3^2- -> 5SO4^2- + 2Mn^2+ + 3H2O} \quad\text{(CB: -6 : -6)}$
$\ce{16 H+ + 2 MnO4- + 5C2O4^2- -> 10 CO2 + 2Mn^2+ + 8 H2O} \quad\text{(CB +4 : +4)}$
The following is multiple choice question (with options) to answer.
What term describes a type of redox reaction in which the same substance is both oxidized and reduced? | [
"misappropriation",
"disapprobation",
"interposition",
"disproportion"
] | D | Disproportion is a type of redox reaction in which the same substance is both oxidized and reduced. Identify the element that is disproportionating and indicate the initial and final oxidation numbers of that element. 2CuCl(aq) → CuCl2(aq) + Cu(s) Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-6345 | gene, genetics
Title: How long does it take for a person to lose all offsprings due to inheritance? From this I know we will only inherit some genetic informations from parents, which is about 50 percent. But the problem is, gene has finite size, after some generations a person leaves only $0.5 \times 0.5 \times 0.5$ parts of genes to the offsprings, and it will be casted into zero. My question is, how long does it required for a person to lose all genetic information in the world? I think your question conveys some misunderstanding.
A child is related to each parent by a factor of ½. Humans have a diploid genome, meaning they have two copies of each chromosome (see: autosome). When two humans reproduce, they each contribute one copy of each chromosome to the offspring, in other words, they contribute a haploid genome to make a diploid child. Genetic information is not "lost" - the genome is not shrinking by a factor of ½ every generation.
However, relatedness does decrease from generation to generation. You are related to each of your parents by a factor of ½, each of your grandparents by a factor of ½ $\times$ ½, your great-grandparents by a factor of ½ $\times$ ½ $\times$ ½... You are also related to your children by a factor of ½, you are related to your grandchildren by a factor of ½ $\times$ ½... You get the picture, right?
For example, imagine the genome carries just one gene. Your father carries alleles $AA$ at that locus, and your mother $aa$. You would then be $Aa$ and, because half of your alleles came from your father and the other half from your mother, be related to each by a factor of ½, but all three of you have the same number of genes (1) and that gene is the same length (in nucleotides, barring mutations) in all three.
The following is multiple choice question (with options) to answer.
Each organism inherits one of what item for each gene from each parent? | [
"molecule",
"allele",
"cell",
"phenotype"
] | B | |
SciQ | SciQ-6346 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
What term is used to refer to the external female reproductive structures collectively? | [
"cervix",
"vulva",
"uterus",
"vagina"
] | B | External Female Genitals The external female reproductive structures are referred to collectively as the vulva (Figure 27.10). The mons pubis is a pad of fat that is located at the anterior, over the pubic bone. After puberty, it becomes covered in pubic hair. The labia majora (labia = “lips”; majora = “larger”) are folds of hair-covered skin that begin just posterior to the mons pubis. The thinner and more pigmented labia minora (labia = “lips”; minora = “smaller”) extend medial to the labia majora. Although they naturally vary in shape and size from woman to woman, the labia minora serve to protect the female urethra and the entrance to the female reproductive tract. The superior, anterior portions of the labia minora come together to encircle the clitoris (or glans clitoris), an organ that originates from the same cells as the glans penis and has abundant nerves that make it important in sexual sensation and orgasm. The hymen is a thin membrane that sometimes partially covers the entrance to the vagina. An intact hymen cannot be used as an indication of “virginity”; even at birth, this is only a partial membrane, as menstrual fluid and other secretions must be able to exit the body, regardless of penile–vaginal intercourse. The vaginal opening is located between the opening of the urethra and the anus. It is flanked by outlets to the Bartholin’s glands (or greater vestibular glands). |
SciQ | SciQ-6347 | exoplanet, density
Title: What is the least dense exoplanet? An exoplanet with density 0.31 grams per cubic centimeter has been found. Is this the least dense exoplanet we know of? The article you link to refers to Borsato et al. 2019, which attempted to rectify discrepancies in the measured properties of planets in the Kepler-9 system between transit timing variation measurements and radial velocity measurements. They arrived at $\rho\sim0.31^{+0.05}_{-0.06}\text{ g cm}^{-3}$ for Kepler-9c. However, Borsato et al.'s Figure 10 shows that there are other exoplanets in this mass regime with substantially lower densities, e.g. WASP-107b, which comes in at about $\rho\sim0.19\text{ g cm}^{-3}$:
Even WASP-107b, however, doesn't hold the record for the least dense exoplanet. The three planets in the Kepler-51 system, Kepler-51b, Kepler-51c, and Kepler-51d, may hold that record. Multiple groups (Masuda 2014, Roberts et al.) have found densities of around $\rho\sim0.03\text{ - }0.06\text{ g cm}^{-3}$ for both planets.
The following is multiple choice question (with options) to answer.
Which state of matter has the lowest density? | [
"fluids",
"solids",
"liquids",
"gases"
] | D | Gases have much lower densities than liquids and solids. For example, liquid water is over 1000 times more dense than water vapor at STP. |
SciQ | SciQ-6348 | cell-biology
Title: Structure of Cell Are cells spheres or ovals/circles bound by phospholipidbilayer?
If they are spherical how are we able to see the nucleus through the phospholipid bilayer under a microscope? Not exactly. That is a stereotype of cells. Muscle cells are not round nor oval, but rather elongated rods. If you were to look up epithelia cells, you can quickly see that cells are grouped based on their physical characteristics; simple (round/oval & single layer), columnar, and cuboidal to name a few. Cells come in many shapes and sizes. As Hans stated, stains are vital in viewing cellular components. There is a diverse amount of stains used - which all carry a purpose and benefit in a specific application.
The following is multiple choice question (with options) to answer.
Skeletal, cardiac, and smooth are the three types of what cells and possess morphologies correlated with their functions? | [
"muscle",
"bone",
"organ",
"cartilage tissue"
] | A | 4.4 Muscle Tissue and Motion The three types of muscle cells are skeletal, cardiac, and smooth. Their morphologies match their specific functions in the body. Skeletal muscle is voluntary and responds to conscious stimuli. The cells are striated and multinucleated appearing as long, unbranched cylinders. Cardiac muscle is involuntary and found only in the heart. Each cell is striated with a single nucleus and they attach to one another to form long fibers. Cells are attached to one another at intercalated disks. The cells are interconnected physically and electrochemically to act as a syncytium. Cardiac muscle cells contract autonomously and involuntarily. Smooth muscle is involuntary. Each cell is a spindle-shaped fiber and contains a single nucleus. No striations are evident because the actin and myosin filaments do not align in the cytoplasm. |
SciQ | SciQ-6349 | human-biology
Title: Why do we sweat after drinking water and running? Why do we sweat after running?
Also we sweat sometime after drinking lots of water. Why it is so?
Can someone please enlighten me in this regard? Exercise, such as running, increases muscle activity. This increases the energy demand of these tissues, which increases the rate of cellular respiration. Respiration releases heat as a by-product, therefore the body is hotter during and after exercise.
Sweating is a homoeostatic mechanism to keep core body temperature constant. It is a response to lower the body temperature. When the body becomes too hot, sweat is released onto the surface of the skin. The water from the sweat then takes some of the excess heat energy from the body and uses it to evaporate. Because water has a relatively large specific heat capacity a lot of heat can be carried away by this method.
The following is multiple choice question (with options) to answer.
What do glands in the skin produce to cool down the body? | [
"saliva",
"sweat",
"mucus",
"lactic acid"
] | B | glands in the skin that produce sweat, a salty fluid that helps cool down the body. |
SciQ | SciQ-6350 | 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.
The only obvious difference between boys and girls at birth is what type of organs? | [
"reproductive",
"respiratory",
"nervous",
"digestive"
] | A | The only obvious difference between boys and girls at birth is their reproductive organs. However, even the reproductive organs start out the same in both sexes. |
SciQ | SciQ-6351 | sensation, olfaction
http://www.comeaddestrareuncane.com/blog/tag/cani-molecolari/
In the dog, the surface of the olfactory mucosa varies between 70 and 150 cm2 - in this tissue the number of olfactory receptors varies from 250 to 280 million - In 1962, Becker et al. showed that dogs are able to recognize substances in dilutions from 1/100 to 1/10.000.000.
- http://milano.corriere.it/milano/notizie/cronaca/12_febbraio_19/cani-olfatto-parere-esperto-1903358352720.shtml
Have you noticed how a dog sniffs the urine of a female "tasting it"? It is the same action that makes the viper when it follows the track of the mouse: it evertes the tongue and carries on it the odorous particles in the buccal cavity, and this organ has a function in the middle between the olfactory and gustatory ones. "Pointing dogs" is as pointing "the wild" taste the smell.
"Eat the scent", in the jargon, because savored, not only in terms of smell, the smell of the wild. The Jacobson's organ is then a second organ capable of perceiving odors, the first we've said is represented ciliated epithelium of the mucous membrane of the nose.
But there is a third organ called the "Rodolfo-Masera" which also serves to sense the emanations chemical (not yet known which), that way you could explain a specialization of these organs to perceive certain groups of biochemicals than others.
- http://www.laciotola.net/Cani/la-funzione-olfattiva-del-cane.html
The following is multiple choice question (with options) to answer.
Mammals have a number of kinds of thermoreceptors, each specific for a particular what? | [
"temperature range",
"weight range",
"electrical range",
"oxygen range"
] | A | |
SciQ | SciQ-6352 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
With a shape that specially suits its function of sending nerve signals to other cells, the human nerve cell is an example of what? | [
"maturation",
"specialization",
"adaptation",
"evolution"
] | B | The human nerve cell in Figure below is a good example of a specialized animal cell. Its shape suits it for its function of sending nerve signals to other cells. A nerve cell couldn’t take this shape if it were surrounded by a rigid cell wall. |
SciQ | SciQ-6353 | polymers
Title: What do people mean with "per unit volume" in polymer solutions theory? I am reading Modern Theory of Polymer Solutions by Hiromi Yamakawa and in the context of the virial expansion the following puzzles me a bit:
"...expanded in terms of solute concentration $c$ (in gramms per unit volume)...
"...Thus, by use of the relation $ρ = N_A c/M$ with $N_A$ the Avogadro number, $c$ the solute concentration (g/cc), and $M$ the solute molecular weight..."
What exactly does unit volume mean in this context? And how can I interpret the unit g/cc? Unit volume is a volume equal to 1 standard volume unit in the system of units you are using.
In most contexts (like this one) it shows up as "per unit volume". In this case it is because we are discussing density. Density is mass "per unit volume".
In your question they give the units $\frac{g}{cc}$. This is a bit confusing if you don't know much about unit labeling. "$cc$" is one way to say "cubic centimetres" (probably more common some places than others, in Canada I rarely see it that way besides in the medical community and engine sizing). I find it far less confusing to keep it as $cm^3$, as then it's obviously cubic centimeters.
You can also have "unit mass" and "unit time" for example, and things are often measured in "per unit mass" and "per unit time".
I can think of a couple very common and good reasons to use "unit values". Often times materials and situations can be expressed in a way where they scale linearly with some variable. Mass of an object scales linearly for an object with uniform density (mass per unit volume). This means that if you know the density of a material, and it's volume, you can calculate the weight.
The following is multiple choice question (with options) to answer.
What is defined as the mass per unit volume of a substance? | [
"density",
"weight",
"height",
"diameter"
] | A | As you know, density is defined as the mass per unit volume of a substance. Since gases all occupy the same volume on a per mole basis, the density of a particular gas is dependent on its molar mass. A gas with a small molar mass will have a lower density than a gas with a large molar mass. Gas densities are typically reported in g/L. Gas density can be calculated from molar mass and molar volume. |
SciQ | SciQ-6354 | equilibrium, water
Title: Can water synthesis and decomposition be in a dynamic equilibrium? When heated at extreme temperatures, water can spontaneously decompose.
According to Wikipedia (https://en.wikipedia.org/wiki/Water_splitting):
In thermolysis, water molecules split into their atomic components hydrogen and oxygen. For example, at 2200 °C about three percent of all H2O are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H2, O, O2, and OH. Other reaction products like H2O2 or HO2 remain minor. At the very high temperature of 3000 °C more than half of the water molecules are decomposed, but at ambient temperatures only one molecule in 100 trillion dissociates by the effect of heat.[15] The high temperatures and material constraints have limited the applications of this approach.
The following is multiple choice question (with options) to answer.
What reaction means, literally, “splitting with water"? | [
"aqueous",
"hydroxis",
"fission",
"hydrolysis"
] | D | Esters are neutral compounds, unlike the acids from which they are formed. In typical reactions, the alkoxy (OR′) group of an ester is replaced by another group. One such reaction is hydrolysis, literally “splitting with water. ” The hydrolysis of esters is catalyzed by either an acid or a base. Acidic hydrolysis is simply the reverse of esterification. The ester is heated with a large excess of water containing a strong-acid catalyst. Like esterification, the reaction is reversible and does not go to completion. |
SciQ | SciQ-6355 | particle-physics, electrons, elementary-particles, protons, subatomic
Title: Are protons bigger than electrons? In every text/ physics book that I've read, Protons are mentioned as particles that are bigger, way bigger 2000 times to be precise, than electrons...I believed that until a few minutes ago when I googled "what is the radius of an electron" and then I read somewhere that it was 2.5 times bigger than the radius of a PROTON...the radius of an ELECTRON is bigger than that of a PROTON. Which goes completely against every physics text book that I've read...Any help towards explaining why protons are 2000 times bigger while its radius is 2.5 times smaller than that of an electron will be valued...thanx in advance Quantum mechanical particles have well-defined masses, but they do not have well-defined sizes (radius, volume, etc) in the classical sense. There are multiple ways you could assign a length scale to a particle, but if you think of them as little balls with a well-defined size and shape, then you're making a mistake.
de Broglie Wavelength: Particles which pass through small openings exhibit wavelike behavior, with a characteristic wavelength given by
$$\lambda_{dB} = \frac{h}{mv}$$
where $h$ is Planck's constant, $m$ is the particle's mass, and $v$ is the particle's velocity. This sets the length scale at which quantum effects like diffraction and interference become important. It also turns out that if the average spacing between particles in an ideal gas is on the order of $\lambda_{dB}$ or smaller, classical statistical mechanics breaks down (e.g. the entropy diverges to $-\infty$).
Compton Wavelength: One way to measure the position of a particle is to shine a laser on the region where you think the particle will be. If a photon scatters off of the particle, you can detect the photon and trace it's trajectory back to determine where the particle was. The resolution of a measurement like this is limited to the wavelength of the photon used, so smaller wavelength photons yield more precise measurements.
However, at a certain point the photon's energy would be equal to the mass energy of the particle. The wavelength of such a photon is given by
The following is multiple choice question (with options) to answer.
Approximately how much larger is the radius of an atom than that of its nucleus? | [
"10 times",
"1000 times",
"100 times",
"1 times"
] | A | The radius of an atom is approximately 10 times larger than the radius of its nucleus. If the radius of the nucleus were 1.0 cm, what would be the radius of the atom in centimeters? in miles?. |
SciQ | SciQ-6356 | human-biology, biophysics, skin, light, uv
Title: Can UV radiation be safe for the skin? It is well known that UV radiation can damage the DNA and generally harm our skin.
We also know that UV radiation helps on the production of melanin and Vitamin D.
From what I could find, the DNA absorption spectrum goes to almost zero for wavelengths higher than 300 nm. This seems to suggest that we would be safe to use UV radiation between 300 and 340 nm in our skin (as long as the power or exposure is not too high/long to make burns), for therapeutic purposes such as the stimulation of Vitamin D production.
Is this assumption correct? Are there any evidences that we could use this UV wavelength range safely? You're talking about long-wave UV, or UV-A radiation. In the 80s, experts claimed that this was a safe wavelength. Protection against UV-A was not part of sunscreen in the early days. Consequently, UV-A was (and still is) used in tanning beds due to its perceived safety over UV-B. However, a lot of research has been done since.
UV-A is well understood now to also be unsafe in unreasonable amounts. Currently, UV-A protection is a typical feature of sunscreen and tanning beds are still not a healthy alternative to moderate, healthy doses of sun. Here is a recent review covering some of the aspects comparing different UV range effects on skin. I really suggest you put a search engine to good use here; it makes little sense for us to expound on the literature when it is so clear and easily available.
In summary,
UVA certainly contributes to the development of skin cancer.
UVA penetrates deeper into the skin than UV-B (which is largely responsible for 'burning' of the topmost layer of skin, without directly affecting the deeper layers). For this reason, UV-B is associated primarily with burning and UV-A is primarily associated with aging and aging diseases like cancer.
It is important to note that 95% of UV light in every day life is UV-A, because it does not vary seasonally and can penetrate clouds and windows. Therefore, in spite of the fact that short wavelengths carry more energy per photon, the ratios of UV-A and UV-B exposure are far from equal.
These are only a few of the explanations as to why we observe an incidence of aging and skin damage and disease upon UV-A exposure.
The following is multiple choice question (with options) to answer.
What can be worn to protect hands and skin from harm? | [
"masks",
"gloves",
"splints",
"filters"
] | B | |
SciQ | SciQ-6357 | human-anatomy
In the wrist, you can have palmar flexion, dorsiflexion (extension), ulnar flexion (abduction) and radial flexion (adduction) (Teachmeanatomy).
In the ankle, you can have plantar flexion, dorsiflexion (extension), inversion (inward rotation, adduction) and eversion (outward rotation, abduction). (ScienceDirect).
In the shoulder and hip, raising a limb to the same side as the limb is, is abduction (lateral extension) and raising it to the opposite side is adduction.
Moving the thumb toward the palm (in the same plane as palm) is flexion (adduction) and moving it away from it is extension (abduction).
You can read about flexion and extension and other movements here: Types of Body Movements (BCcampus)
The following is multiple choice question (with options) to answer.
What type of movements are produced when the angle between the bones of a joint changes? | [
"oblong",
"angular",
"circular",
"microscopic"
] | B | The wide range of movement allowed by synovial joints produces different types of movements. Angular movements are produced when the angle between the bones of a joint changes. Flexion, or bending, occurs when the angle between the bones decreases. Moving the forearm upward at the elbow is an example of flexion. Extension is the opposite of flexion in that the angle between the bones of a joint increases. Rotational movement is the movement of a bone as it rotates around its own longitudinal axis. Movement of the head as in saying “no” is an example of rotation. |
SciQ | SciQ-6358 | neuroscience, neurophysiology, hearing, human-ear, senses
Title: Depolarization and hyperpolarization in stereocilia of the inner ear It’s a well mentioned fact that when the stereocilia of the cochlear hair cells bend in one direction, the hair cell depolarizes, and when the stereocilia bend in the other direction, the cell hyperpolarizes. When the basilar membrane vibrates, the stereocilia are bent back and forth, creating depolarizations in the hair cells followed by hyperpolarizations. What I’m having trouble understanding is why this is significant. This does not determine the frequency of the sound wave, as that is determined by the location along the basilar membrane that the wave impinges on. I don’t see how this would determine amplitude either, seeing as a greater amplitude would only create more drastic bending of a greater number of hair cells. Can anyone shed some light on this? There are roughly two modes of pitch coding in the cochlea: place-coding and temporal coding. The place-theory is the most prevalent accepted model of how the cochlea realizes pitch coding (e.g., Zwislocki, 1991). Basically, it is based on a frequency-to-place Fourier transformation on the incoming sound, where each frequency is coded on a different place on the basilar membrane, as described accurately in the question.
However, there is another, much overlooked way of coding pitch, namely temporal coding. Up until about 1 kHz, spiral ganglion cells in the auditory nerve and acoustical brain stem regions (such as the inferior colliculus) have been found to respond in a phase-locked pattern (Du et al., 2011). Electrophysiology in auditory nerve fibers illustrates the phase-locked activity in response to low-frequency sounds (Fig. 1). This phase-locking behavior of neurons in the auditory system is called the frequency-following response (FFR).
The following is multiple choice question (with options) to answer.
What senses the movement of liquid in ear canals? | [
"hair cells",
"Brain Cells",
"Ear Drum",
"muscle cells"
] | A | This bottle of water models the semicircular canals in your ears. When you tip the bottle, the water moves up or down the sides of the bottle; when you tip your head, the liquid inside the semicircular canals moves up and down the sides of the canals. Tiny hair cells lining the canals sense the movement of liquid and send messages to the brain. |
SciQ | SciQ-6359 | endocrinology
Excitement or stress response, including fast heart rate and breathing and anxiety: short term response: adrenaline; long-term response: cortisol
Appetite: ghrelin, leptin, adiponectin, cholecystokinin, insulin, glucagon-like peptide, gastrointestinal peptide...
Sexual drive: sex hormones, mainly testosterone and estradiol
Sleepiness: melatonin, cortisol
Depression: cortisol, sex hormones (mainly in women)
The point of this answer is to show that some of your feelings can be simply affected by hormones, which are note some ultimate forces, and that being aware of that can help you to control them to some extent.
The following is multiple choice question (with options) to answer.
What part of the brain regulates certain hormones associated with reproduction during breeding seasons? | [
"hypothalamus",
"hippocampus",
"frontal lobe",
"thalamus"
] | A | |
SciQ | SciQ-6360 | materials, plastics
Title: Which material to use for athletic accessories? I'm looking for some guidance in selecting the right material for dance shoes heels and women's self-defense accessories.
I'm looking for a material that 1) has a superb strength-to-weight ratio, can withstand punishing and frequent impact, and very light (like plastic).
The part for the shoe will be very, very slender (stiletto heel), but will have to be able to endure hours of jumping, sliding, stomping, spinning, and skidding dancers… is compression strength the right term?
2) The material must also be safe to use as jewelry, so nothing toxic. Also, I am looking for something that tends to snap, rather than shatter, when it fails under pressure.
3) Lastly, it would be great if this material can be 3D printed, although that is not a must.
An inexpensive material would be ideal, of course, but I am open to learning about a fuller range of materials, including the more expensive ones. I am willing to consider a higher priced material if it will offer substantial value to the accessories in terms of strength, quality, and safety. For plastics, my first instinct for the first two properties would be a polycarbonate plastic. Polycarbonates are known to be very strong plastics (tensile strength up to ~70 MPa) and deform without breaking under many conditions, which is why they're commonly used in things like safety glasses and bullet-resistant glass. It also looks very interesting as it's quite optically clear. PC is 3D printable, I've seen a few people using it in hobby printers (http://www.protoparadigm.com/blog/2011/12/printing-polycarbonate/) and in very high end StrataSys printers, but it's not a super common material so it might take some experimenting.
Another option is a nylon. There are a number of different types available and many have similar properties to polycarbonates (minus the optical clarity). Nylons seem to be a bit more popular for 3D printing and I've heard good things about the Taulman filaments.
The following is multiple choice question (with options) to answer.
What is any nonmetallic, inorganic solid that is strong enough for use in structural applications called? | [
"metallic",
"ceramic",
"tissue",
"glass"
] | B | Ceramics A ceramic is any nonmetallic, inorganic solid that is strong enough for use in structural applications. Traditional ceramics, which are based on metal silicates or aluminosilicates, are the materials used to make pottery, china, bricks, and concrete. Modern ceramics contain a much wider range of components and can be classified as either ceramic oxides, which are based on metal oxides such as alumina (Al2O3), zirconia (ZrO2), and beryllia (BeO), or nonoxide ceramics, which are based on metal carbides such as silicon carbide (carborundum, SiC) and tungsten carbide (WC), or nitrides like silicon nitride (Si 3N4) and boron nitride (BN). All modern ceramics are hard, lightweight, and stable at very high temperatures. Unfortunately, however, they are also rather brittle, tending to crack or break under stresses that would cause metals to bend or dent. Thus a major challenge for materials scientists is to take advantage of the desirable properties of ceramics, such as their thermal and oxidative stability, chemical inertness, and toughness, while finding ways to decrease their brittleness to use them in new applications. Few metals can be used in jet engines, for example, because most lose mechanical strength and react with oxygen at the very high operating. |
SciQ | SciQ-6361 | the-sun, solar-system, earth, star-formation, planetary-formation
Earth Composition
Iron 32.1%
Oxygen 30.1%
Silicon 15.1%
Magnesium 13.9%
Sulfur 2.9%
Nickel 1.8%
Calcium 1.5%
Aluminum 1.4%
Other 1.2%
A couple things I notice. The sun is quite homogenous compared to earth! It is mostly composed of just two elements whereas on earth no single element makes up more than 32% of the planet's mass.
Also, there is extremely little overlap in the elements: hydrogen and helium are the only game in town on the sun, but are nearly nonexistent on earth.
This makes me very curious! What aspect of the process of the formation of the solar system was responsible for essentially segregating these elements? Is it simply that the heavier elements were "burned" away in the hotter environment of the sun, or is there some other explanation? The composition of the Sun is close to the composition of the universe as a whole. It's the Earth that's the outlier. If you look up the elemental composition of the universe as a whole, you'll see numbers for hydrogen and helium almost identical with the ones for the Sun. Theory can predict the elemental ratios. The universe started out as entirely hydrogen, and helium and a few light elements like lithium were created in the big bang. Heavier elements like oxygen and iron were made in stars, and elements heavier than iron are largely from supernovae. But enough background, let's answer your question.
Earth, along with the other planets, formed from the same cloud of dust and gas as the Sun. The cloud started out with the same elemental composition as the Sun. The cloud collapsed under the force of gravity, and somehow chunks of material (called planetesimals) started to coalesce into planets (nobody is really certain how this process worked). The proto-Sun started to emit light and warm up the surroundings. The regions closer to the Sun, where the Earth was forming, got hot enough that light elements like hydrogen evaporated from the planetesimals. Left behind were heavier elements like oxygen, silicon (which make up most rocks) and iron. The lighter elements ended up further out, which is why Jupiter has a hydrogen-rich atmosphere.
The following is multiple choice question (with options) to answer.
What is the outer layer of the sun made up of? | [
"plasma",
"nitrogen",
"gas",
"oxygen"
] | A | outermost layer of the sun, made up of a plasma that extends millions of kilometers into space. |
SciQ | SciQ-6362 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
Viruses may damage or kill cells by causing the release of hydrolytic enzymes from where? | [
"lipids",
"glands",
"lysosomes",
"capillaries"
] | C | |
SciQ | SciQ-6363 | evolution
Title: Is there any genetic similarity that defy evolution theory? For example,
say species A is common ancestor of B, and C. Species B is a common ancestor of D and E.
We would expect that there will be more genetic similarity between D and E than D and C. And those genetic similarity must exist in B.
In other word, we won't expect genetic similarity that don't "cross" the common ancestor or the evolutionary tree.
The exception is probably genetically engineered bacteria.
That being said, am I correct?
Some people say that we have similarity with pigs and chimps even though our common ancestors may be to far off. That won't happen right?
To summarize
I expect that evolutionary tree will form a well, tree. Genetic similarity would infect "nearby" trees and can't jump between trees without connectors, such as common ancestors.
Is that what we observe for ALL species? You have an excellent answer from Remi.b already but I just wanted to add/emphasise this (because there is always more than one way of explaining something and IMO the site benefits from having many answers to the questions)...
The tree we construct does not necessarily accurately reflect what happened in evolution. If B & C evolved from A, and D & E came from B, we would create this tree if we measured using the correct indicator. But the methods we have are not perfect. The first evolutionary trees were based on morphological descriptions etc. and clearly some of the classifications were going to be wrong. These days we use molecular methods, which are probably more accurate but could also be wrong some times. For example if we based our phylogeny on one SNP variant we could have some idea about the phylogeny between a few species, but if we based it on millions of SNPs we would have a much better idea - as technology & models improve that is becoming more realistic. The key point here being there is a difference between the trees we can draw from evidence, and the real evolutionary tree.
The following is multiple choice question (with options) to answer.
Species that have diverged from their common ancestors have greater differences in what? | [
"dna sequence",
"immunology",
"cell structure",
"life span"
] | A | Evidence from the fossil record can be combined with data from molecular clocks. A molecular clock uses DNA sequences (or the proteins they encode) to estimate relatedness among species. Molecular clocks estimate the time in geologic history when related species diverged from a common ancestor. Molecular clocks are based on the assumption that mutations accumulate through time at a steady average rate for a given region of DNA. Species that have accumulated greater differences in their DNA sequences are assumed to have diverged from their common ancestor in the more distant past. Molecular clocks based on different regions of DNA may be used together for more accuracy. |
SciQ | SciQ-6364 | electrochemistry, redox, electrons, electricity
I was a bit baffled by the "electrons are energy" remark - this seems at best poetic. He seems to be conflating electrical potential energy with electrons, but these aren't the same thing. If electrons actually "were" the electrical potential energy in a battery, wouldn't that imply that the compound at the cathode would never actually be reduced, since all energy, and therefore all electrons that "flowed" through the circuit, would be lost after depletion of the battery's potential energy? My understanding is that electrons can have energy but are not themselves energy. Although I have a very low level of knowledge regarding this topic, I've done a few hours of research and found that the common notion of electricity as a flow of electrons akin to a river is wrong, and that although electrons do move very slowly through a circuit, the flow of energy is due to electromagnetic fields associated with charged particles.
Unfortunately, I could not find any sources that directly answered this question, so I would greatly appreciate direct answers to this question from experts on this topic. Very bad explanation in the email response.
The explanation reads..
"Thus, the battery has the same number of protons and neutrons, but
less electrons. This also means more unreactive metal cations exist in
a used battery."
The following is multiple choice question (with options) to answer.
In a fuel cell, energy is not stored; electrical energy is provided by what? | [
"carbon reaction",
"consumption reaction",
"chemical reaction",
"fusion reaction"
] | C | called an alkaline battery when adapted to operate under alkaline conditions. Button batteries have a high output-to-mass ratio; lithium–iodine batteries consist of a solid electrolyte; the nickel– cadmium (NiCad) battery is rechargeable; and the lead–acid battery, which is also rechargeable, does not require the electrodes to be in separate compartments. A fuel cell requires an external supply of reactants as the products of the reaction are continuously removed. In a fuel cell, energy is not stored; electrical energy is provided by a chemical reaction. |
SciQ | SciQ-6365 | mineralogy, hydrogeology, mars
Despite active transport into Earth’s mantle, water has been present on our planet’s surface for most of geological time. Yet water disappeared from the Martian surface soon after its formation. Although some of the water on Mars was lost to space via photolysis following the collapse of the planet’s magnetic field, the widespread serpentinization of Martian crust suggests that metamorphic hydration reactions played a critical part in the sequestration of the crust. Here we quantify the relative volumes of water that could be removed from each planet’s surface via the burial and metamorphism of hydrated mafic crusts, and calculate mineral transition-induced bulk-density changes at conditions of elevated pressure and temperature for each. The metamorphic mineral assemblages in relatively FeO-rich Martian lavas can hold about 25 per cent more structurally bound water than those in metamorphosed terrestrial basalts, and can retain it at greater depths within Mars. Our calculations suggest that in excess of 9 per cent by volume of the Martian mantle may contain hydrous mineral species as a consequence of surface reactions, compared to about 4 per cent by volume of Earth’s mantle. Furthermore, neither primitive nor evolved hydrated Martian crust show noticeably different bulk densities compared to their anhydrous equivalents, in contrast to hydrous mafic terrestrial crust, which transforms to denser eclogite upon dehydration. This would have allowed efficient overplating and burial of early Martian crust in a stagnant-lid tectonic regime, in which the lithosphere comprised a single tectonic plate, with only the warmer, lower crust involved in mantle convection. This provided an important sink for hydrospheric water and a mechanism for oxidizing the Martian mantle. Conversely, relatively buoyant mafic crust and hotter geothermal gradients on Earth reduced the potential for upper-mantle hydration early in its geological history, leading to water being retained close to its surface, and thus creating conditions conducive for the evolution of complex multicellular life.
does serpentinization just refer to the formation of some hydrated minerals that happen to be of a class that is historically been referred to as serpentinite or it's subgroup
The following is multiple choice question (with options) to answer.
What substance comes toward earth's crust through mantle plumes? | [
"rocks",
"magma",
"water",
"gas"
] | B | Some volcanoes form over active hot spots . Scientists count about 50 hot spots on the Earth. Hot spots may be in the middle of a tectonic plate. Hot spots lie directly above a column of hot rock called a mantle plume . Mantle plumes continuously bring magma up from the mantle towards the crust ( Figure below ). |
SciQ | SciQ-6366 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
A plant is composed of two main types of tissue: meristematic tissue and what other kind of tissue? | [
"permanent tissue",
"synovial tissue",
"nonvascular tissue",
"muscle tissue"
] | A | CHAPTER SUMMARY 30.1 The Plant Body A vascular plant consists of two organ systems: the shoot system and the root system. The shoot system includes the aboveground vegetative portions (stems and leaves) and reproductive parts (flowers and fruits). The root system supports the plant and is usually underground. A plant is composed of two main types of tissue: meristematic tissue and permanent tissue. Meristematic tissue consists of actively dividing cells found in root and shoot tips. As growth occurs, meristematic tissue differentiates into permanent tissue, which is categorized as either simple or complex. Simple tissues are made up of similar cell types; examples include dermal tissue and ground tissue. Dermal tissue provides the outer covering of the plant. Ground tissue is responsible for photosynthesis; it also supports vascular tissue and may store water and sugars. Complex tissues are made up of different cell types. Vascular tissue, for example, is made up of xylem and phloem cells. |
SciQ | SciQ-6367 | solubility, solvents
Title: Solubility in homogenous mixtures of solvents Alcohol and water are miscible. I am coming across some chemicals that are soluble in alcohol and insoluble in water. If I know solubility in two solvents separately, is solubility in a mixture of the two always straightforward, or are there confounding variables?
E.g., if some chemical will dissolve to 100g/L alcohol at 25°C, then will its solubility in a 50/50 mixture by volume of water and alcohol at 25°C always be 50g/L?
Does this generalize to all miscible solvents? The complication comes from solubility of the solvents with each other whilst simultaneously having some solvation power of a solute. I have made a compound before that was so water soluble that it caused sodium chloride to precipitate out. A real example was of an organic compound that had 1%w/v solubility in ethanol but around 6.5%w/v in toluene. In a 50:50 mixture, the compound had solubility of 13%w/v. A completely non-linear result! The solubility was even higher in 90:10 toluene-ethanol. So, the complex nature of three way interactions mean it would be very difficult to predict these solubility graphs just using two data points of the two pure solvents.
If we asked the same question of boiling points, we would point straightaway to azeotropes. So, analogously, other properties exhibit this behaviour. However, in this instance the nature of the solute as a third component makes it too complicated to predict without having the wealth of property data available for all components. If this is known and you have the software, you may have a chance.
The following is multiple choice question (with options) to answer.
The smallest and lightest alcohols (methanol, ethanol, propanol) are completely soluble in? | [
"argon",
"water",
"gasoline",
"oil"
] | B | The smallest and lightest alcohols (methanol, ethanol, propanol) are completely soluble in water in all proportions. In a solution, the hydroxyl groups of alcohol molecules and the water molecules form hydrogen bonds with each other, resulting in complete miscibility. However, as the length of the carbon chain increases, the solubility decreases. The solubility of 1-butanol is 7.4 g per 100 g of water, while that of 1-pentanol is 2.7 g per 100 g water, and 1-octanol is 0.06 g per 100 g water. The carbon chain portion of the larger alcohol molecule is nonpolar and leads to the decreased solubility of the overall compound. |
SciQ | SciQ-6368 | genetics, cell-biology, chromosome, meiosis, mitosis
https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/phases-of-meiosis
So, during metaphase I, homologue pairs—not individual
chromosomes—line up at the metaphase plate for separation.
The following is multiple choice question (with options) to answer.
In which stage do chromosomes line up one on top of each other along the middle of the cell, similar to how they line up in mitosis? | [
"cyclohexane ii",
"chromosome ii",
"hectase ii",
"metaphase ii"
] | D | Metaphase II: The chromosomes line up one on top of each other along the middle of the cell, similar to how they line up in mitosis. The spindle is attached to the centromere of each chromosome. |
SciQ | SciQ-6369 | waves, frequency, interference, oscillators, superposition
On a note,I understand that superpositioned wave in first medium,Reflected wave and transmitted wave must have common frequency,But I can't understand why this common frequency must equal frequency of incident wave
This is the link of animation stated in question
https://surendranath.org/GPA/Waves/TWRT/TWRT.html (please select thinner to thicker option in website above) Because you have assumed a linear time invariant medium. A linear time invariant medium is described by a linear time-invariant operator whose eigenfunctions are pure sinusoids that are characterized by their amplitude, frequency and phase. Only amplitude and phase may be changed by such system, meanwhile frequency stays the same between input and output. This is true for lumped as well as for distributed systems, such as RLC circuits or dielectric crystals, resp. This is not really physics. The physics question is rather why a material medium through which an EM wave propagates, for example glass or crystalline dielectric, is linear and time invariant? In practice, nothing is truly linear nor time invariant. For large enough EM intensities in the nonlinear regime you get as minimum harmonics and may also unplanned for nonlinear modulation on the incoming wave and thus shift or spread its fundamental frequency.
If the medium is nonlinear and/or time varying the frequency of the transmitted wave will change. For example, a linear time varying medium is a crystal in which acoustic waves (sound) modulate the density and thus the dielectric permittivity of the medium and when light is scattered off the acoustic wave the the scattered light suffers frequency shift that can be used to measure the the acoustic frequency (an instantaneous spectrum analyzer, see 1.
The following is multiple choice question (with options) to answer.
If the frequency of the electromagnetic wave is the same as the natural frequencies of the system, the transfer of what is much more efficient? | [
"energy",
"sound",
"heat",
"light"
] | A | 24.4 Energy in Electromagnetic Waves Anyone who has used a microwave oven knows there is energy in electromagnetic waves. Sometimes this energy is obvious, such as in the warmth of the summer sun. Other times it is subtle, such as the unfelt energy of gamma rays, which can destroy living cells. Electromagnetic waves can bring energy into a system by virtue of their electric and magnetic fields. These fields can exert forces and move charges in the system and, thus, do work on them. If the frequency of the electromagnetic wave is the same as the natural frequencies of the system (such as microwaves at the resonant frequency of water molecules), the transfer of energy is much more efficient. Connections: Waves and Particles The behavior of electromagnetic radiation clearly exhibits wave characteristics. But we shall find in later modules that at high frequencies, electromagnetic radiation also exhibits particle characteristics. These particle characteristics will be used to explain more of the properties of the electromagnetic spectrum and to introduce the formal study of modern physics. Another startling discovery of modern physics is that particles, such as electrons and protons, exhibit wave characteristics. This simultaneous sharing of wave and particle properties for all submicroscopic entities is one of the great symmetries in nature. |
SciQ | SciQ-6370 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
When are nutrients absorbed into the body? | [
"during digestion",
"after excretion",
"before digestion",
"after digestion"
] | A | |
SciQ | SciQ-6371 | earth-rotation, seasons, time
Title: Are the length of seasons the same globally? Is the length of time, say months, for each season the same all over the world or can it vary? As has been noted in a comment, it depends on how you define seasons (see https://earthscience.stackexchange.com/a/2603/111).
If seasons are defined in astronomical terms, then they have the same length everywhere on the planet. This is simply down to geometry.
However, the effects of astronomical seasons vary geographically in a number of ways. The magnitude of seasonal changes, for example changes in day/night lengths, is more pronounced in higher latitudes, so the effect of (for example) winter might be noticeable for a shorter time period in the tropics than the arctic, and hence some people might reasonably consider winter to be shorter there. There are other, less systematic variations that depend on local climate and weather. In weather terms, not everywhere in the world has the same 4-season cycle that temperate zones tend to experience - so when defining seasons in terms of observable effects one often has, for example, a wet season and a dry season rather than spring /summer /etc.
The following is multiple choice question (with options) to answer.
What happens to the length of the days in the fall? | [
"they change randomly",
"they get longer",
"they stay the same",
"they get shorter"
] | D | For example, in the fall, when the days start to get shorter, the trees sense that there is less sunlight. The plant is stimulated, and it sends messages telling the leaves to change colors and fall. This is an example of photoperiodism , the reaction of organisms, such as plants, to the length of day or night. Photoperiodism is also the reaction of plants to the length of light and dark periods. Many flowering plants sense the length of night, a dark period, as a signal to flower. Each plant has a different photoperiod, or night length. When the plant senses the appropriate length of darkness, resulting in an appropriate length of daylight, it flowers. Flowering plants are classified as long-day plants or short-day plants. Long-day plants flower when the length of daylight exceeds the necessary photoperiod, and short-day plants flower when the day length is shorter than the necessary photoperiod. Long-day plants include carnations, clover, lettuce, wheat, and turnips. Short-day plants include cotton, rice, and sugar cane. |
SciQ | SciQ-6372 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
Of the nine classes of vertebrates, how many are fish? | [
"three",
"one",
"five",
"four"
] | C | Of course. But what type? Of the nine classes of vertebrates, five are fish. Each of the five classes has distinguishing characteristics that allow members to be classified appropriately. Stingray are cartilaginous fish, related to sharks. |
SciQ | SciQ-6373 | 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.
After fertilization is complete, no other sperm can enter. the fertilized ovule forms the seed, whereas the tissues of the ovary become this? | [
"fruit",
"wheat",
"plant",
"vegetables"
] | A | events in angiosperms are known as double fertilization (Figure 32.18). After fertilization is complete, no other sperm can enter. The fertilized ovule forms the seed, whereas the tissues of the ovary become the fruit, usually enveloping the seed. |
SciQ | SciQ-6374 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
What is a fluid-filled body cavity that is completely enclosed by mesoderm called? | [
"pseudocoelom",
"coelom",
"choroid",
"hymenium"
] | B | Later, a true coelom evolved. This is a fluid-filled body cavity that is completely enclosed by mesoderm. The coelom lies between the digestive cavity and body wall. You can see it in the invertebrate in Figure below . Modern invertebrates with a coelom include mollusks (Phylum Mollusca) and annelids (Phylum Annelida). |
SciQ | SciQ-6375 | exoplanet, density
Title: What is the least dense exoplanet? An exoplanet with density 0.31 grams per cubic centimeter has been found. Is this the least dense exoplanet we know of? The article you link to refers to Borsato et al. 2019, which attempted to rectify discrepancies in the measured properties of planets in the Kepler-9 system between transit timing variation measurements and radial velocity measurements. They arrived at $\rho\sim0.31^{+0.05}_{-0.06}\text{ g cm}^{-3}$ for Kepler-9c. However, Borsato et al.'s Figure 10 shows that there are other exoplanets in this mass regime with substantially lower densities, e.g. WASP-107b, which comes in at about $\rho\sim0.19\text{ g cm}^{-3}$:
Even WASP-107b, however, doesn't hold the record for the least dense exoplanet. The three planets in the Kepler-51 system, Kepler-51b, Kepler-51c, and Kepler-51d, may hold that record. Multiple groups (Masuda 2014, Roberts et al.) have found densities of around $\rho\sim0.03\text{ - }0.06\text{ g cm}^{-3}$ for both planets.
The following is multiple choice question (with options) to answer.
Which is the least massive outer planet? | [
"jupiter",
"mars",
"uranus",
"venus"
] | C | Uranus is the least massive outer planet. Its mass is only about 14 times the mass of Earth. Like all of the outer planets, Uranus is much less dense than Earth. Gravity is actually weaker than on Earth’s surface. If you were at the top of the clouds on Uranus, you would weigh about 10 percent less than what you weigh on Earth. |
SciQ | SciQ-6376 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
The nervous system is characterized by electrical signals that are sent from one area to another. whether those areas are close or very far apart, the signal must travel along this? | [
"axon",
"hairs",
"tendons",
"axial"
] | A | 12.4 The Action Potential The nervous system is characterized by electrical signals that are sent from one area to another. Whether those areas are close or very far apart, the signal must travel along an axon. The basis of the electrical signal is the controlled distribution of ions across the membrane. Transmembrane ion channels regulate when ions can move in or out of the cell, so that a precise signal is generated. This signal is the action potential which has a very characteristic shape based on voltage changes across the membrane in a given time period. The membrane is normally at rest with established Na+ and K+ concentrations on either side. A stimulus will start the depolarization of the membrane, and voltage-gated channels will result in further depolarization followed by repolarization of the membrane. A slight overshoot of hyperpolarization marks the end of the action potential. While an action potential is in progress, another cannot be generated under the same conditions. While the voltage-gated Na+ channel is inactivated, absolutely no action potentials can be generated. Once that channel has returned to its resting state, a new action potential is possible, but it must be started by a relatively stronger stimulus to overcome the K + leaving the cell. The action potential travels down the axon as voltage-gated ion channels are opened by the spreading depolarization. In unmyelinated axons, this happens in a continuous fashion because there are voltage-gated channels throughout the membrane. In myelinated axons, propagation is described as saltatory because voltage-gated channels are only found at the nodes of Ranvier and the electrical events seem to “jump” from one node to the next. Saltatory conduction is faster than continuous conduction, meaning that myelinated axons propagate their signals faster. The diameter of the axon also makes a difference as ions diffusing within the cell have less resistance in a wider space. |
SciQ | SciQ-6377 | optics, reflection, geometric-optics
Title: Reflection of light rays A set of light rays emitted from a point of an orange hits a smooth and flat surface. My question is: The angles of incidence are different, light rays are reflected towards different directions, why is a distorted image not formed? Why is this not an example of diffuse reflection? That's precisely why a single sharp image is formed. Extend all three reflected rays back below the surface to see where the light seems to come from. If your drawing is precise enough, you'll find that they intersect at a single point, which is precisely the mirror image of the object.
The point of specular reflection is that the light seems to come from the mirror image. You already get divergent rays from each point even from the original object, and the mirror image does the same. You'll only get parallel rays, if the incident rays were parallel (e.g. from an object that is effectively infinitely far away).
The following is multiple choice question (with options) to answer.
What occurs when light reflects off a very smooth surface and forms a clear image? | [
"projection",
"absorption",
"refraction",
"regular reflection"
] | D | Regular reflection occurs when light reflects off a very smooth surface and forms a clear image. Diffuse reflection occurs when light reflects off a rough surface and forms a blurry image or no image at all. |
SciQ | SciQ-6378 | dna, dna-sequencing
Except for Red Blood Cells, every somatic cell contains two copies of the autosomal chromosomes and a pair of sex chromosomes, either XX or XY (Assuming an average human being) One set is maternal and one is paternal
Some lymphocytes actually recombine their chromosomes, so their DNA will be functionally different to all of the other somatic cells in the body.
Gametes undergo Meiosis and will be haploid, only containing one copy of each autosomal chromosome and one of the sex chromosomes
Cells accumulate mutations over time. The closest you could probably come to an exact clone of a person is if you harvested one of the cells from the eight-cell stage of development. The other seven are able to go on and produce a viable and healthy person. The harvested cells DNA would be the closest to the DNA that combined in the fertilization of the egg. The next closest would likely be stem cells from cord blood. Then probably neurons, as they tend to divide the least.
As the link you posted said, ATCG can be represented in a two bit code, so for about 6 billion bases, you would need about 1.5GB of storage (You need to capture both sets of chromosomes in order to produce a person).
The following is multiple choice question (with options) to answer.
The head of the sperm contains what, which holds the chromosomes? | [
"eggs",
"fiber",
"nucleus",
"nerve cells"
] | C | The head of the sperm contains the nucleus. The nucleus holds the chromosomes. In humans, the nucleus of a sperm cell contains 23 chromosomes. The acrosome on the head contains enzymes that help the sperm penetrate an egg. |
SciQ | SciQ-6379 | human-biology, physiology
Title: Why should or shouldn't we allow the human body to take its natural course? For example, when you are sick but don't feel thirsty, this could be due to baroreceptor reflex that is attempting to readjust salt and water balancing.
Why shouldn't a patient be left thirsty and let the body to adjust until he or she feels thirsty again? I am assuming that your question is: "why can a human intervention improve health?". Let me know if I misunderstood your question.
Why can a human intervention improve health?
Let's first avoid going into the details of your example. It is quite obvious that human intervention can often improve health in a way that your body alone cannot. To me, an intuitive way to classify the reasons why human intervention are important to improve health into two categories.
The body does not always react in an adaptive manner.
Example: Anaphylaxis is a serious and sudden allergic reaction that may cause death. An allergic reaction is what is happening when your immune system recognize a chemical as a infectious element while it is not. The reaction of the body is not adaptive and taking medication such as an anti-histaminic can force the body to stop this "stupid" reaction.
Note: There are reasons why the body cannot be always perfect but it is a bit long to make an overview here. There is stochasticity in the developmental processes, there is genetic variation for example due to always occurring deleterious mutations, there is also an arms race between parasites and host. This arm race leads parasites to take advantage of normal host physiological pathways. There are tons of other reasons that relate to the stochasticity and to the physic and physiological constraints of evolutionary processes.
The body sometimes cannot (physical constraint) produce the action that is required to be performed to improve health.
Example: If you have an important wound, then a human-made compression can by far improve your chance of the survival. The body is not able by itself to simulate this external compression to prevent blood to exit the body through the wound.
The following is multiple choice question (with options) to answer.
What system is responsible for defending your body against sickness? | [
"circulatory system",
"nervous system",
"immune system",
"digestion system"
] | C | Infectious diseases are diseases that spread from person to person. They are caused by pathogens such as bacteria, viruses or fungi. What can you do to avoid infectious diseases? Eating right and getting plenty of sleep are a good start. These habits will help keep your immune system healthy. With a healthy immune system, you will be able to fight off many pathogens. The next best way is to avoid pathogens. Though this is difficult, there are steps you can take to limit your exposure to pathogens. |
SciQ | SciQ-6380 | population-dynamics, population-biology
Title: Spread of a benign virus in a population over time This is a somewhat difficult (for me) population dynamics question and I wonder if someone with experience in this area could suggest a reasonable approach?
My simplifying assumptions: As a gross oversimplification, let p(k) be the world's population at generation k, and assume a smooth exponential curve that models p(k) from $k=0$ at 10,0000 B.C.E to generation $k=600$ in 2000 C.E. A generation is 20 years, and in acc. with this Wiki there are about 4 million individuals at $k=0$ and 6070 million at $k=600.$
(Of course the exponential model is bad, as world population growth appears to have been sluggish before recorded history.)
Now assume a benign virus infects 120 individuals in $k=0.$ It benignly infects all individuals who have at least one infected parent. Perhaps unimportantly, it also continues to infect 30 new individuals per million in each generation (because its found in the soil), but would not infect those already exposed.
Call infected individuals II and non-infected NI. They are indistinguishable without clinical tests--which are not done, since the virus is harmless. Since II individuals are almost certain to mate with NI individuals, in earlier generations, the number of II will grow very quickly. For a time the growth rate of II will exceed that of p(k). At some point it will be unlikely that an II individual will encounter an NI mate, however a few NI persons will still pair with NI mates--for a while.
My question is, after 600 generations, what is a reasonable estimate of the percentage of II in the population? Is is possible that there would be any NI individuals left? Or would we have some sort of dynamic equilibrium between II and NI in which (I think) the former would strongly dominate?
FWIW, the population growth model is $p(k)=4e^{0.012 k}$ with $p(k)$ in millions. For simplicity, I denote the population of non-infected individuals by $N$ and the infected ones by $I$.
Model without soil infection
The following is multiple choice question (with options) to answer.
What effect occurs when a few individuals start, or found, a new population? | [
"pioneer",
"founder",
"convergent",
"divergent"
] | B | Founder effect occurs when a few individuals start, or found, a new population. By chance, allele frequencies of the founders may be different from allele frequencies of the population they left. An example is described in the Figure below . |
SciQ | SciQ-6381 | human-evolution
Title: Why do humans retain two kidneys? If one kidney can function just as well as two, why do humans have two kidneys? The cost of growing two kidneys must surely be quite high, especially since one kidney is all that is really needed. One of the easiest answers to the question; "Why do we have ____?" is "Because our ancestors did". This is not trivial or flippant, as it is a significantly important answer that is so often overlooked. Humans are members of Bilataria; a deep branch of the animal tree that is characterized by bilateral symmetry. Humans are typical of other vertebrates in having two kidneys. Selective pressure to reduce to one of two organs is typical in snakes, whose body form favors reduction. But even snakes have two kidneys. Natural selection does not reduce features we don't need unless such a reduction would increase fitness.
The following is multiple choice question (with options) to answer.
Each kidney is supplied by a renal artery and what else? | [
"brain vein",
"coronary artery",
"spinal cord",
"renal vein"
] | D | Each kidney is supplied by a renal artery and renal vein. |
SciQ | SciQ-6382 | photosynthesis, cellular-respiration, energy, sugar
Basically, points 4-7 convey that Calvin-Benson cycle not only produces sugar but what it actually does is fix inorganic carbon (as CO2) to organic form (in the form of sugar). So, most (practically all) of the carbon that a photosynthetic plant has, comes from this carbon fixation process and that's how plants are photoautotrophic.
The following is multiple choice question (with options) to answer.
What cell structures capture light energy from the sun and use it with water and carbon dioxide to produce sugars for food? | [
"fibroblasts",
"ribosomes",
"nuclei",
"chloroplasts"
] | D | Chloroplasts capture light energy from the sun and use it with water and carbon dioxide to produce sugars for food. Chloroplasts look like flat discs and are usually 2 to 10 micrometers in diameter and 1 micrometer thick. A model of a chloroplast is shown in Figure below . The chloroplast is enclosed by an inner and an outer phospholipid membrane. Between these two layers is the intermembrane space. The fluid within the chloroplast is called the stroma , and it contains one or more molecules of small, circular DNA. The stroma also has ribosomes. Within the stroma are stacks of thylakoids , sub-organelles that are the site of photosynthesis. The thylakoids are arranged in stacks called grana (singular: granum). A thylakoid has a flattened disk shape. Inside it is an empty area called the thylakoid space or lumen. Photosynthesis takes place on the thylakoid membrane. |
SciQ | SciQ-6383 | biochemistry
Title: Is hydrolysis of polypeptides and polysaccharides "anabolic" or "catabolic" When a polysaccharide or polypeptide is hydrolyzed into mono-saccharides or amino acids, the building blocks can be oxidized to release energy. The oxidation is considered to be catabolic since it reduces the building blocks to simple compounds: carbon dioxide, water, ammonia, and releases energy.
Is the process of hydrolysis that breaks up polypeptides and polysaccharides a net endothermic or exothermic process?
Do the free amino acids and monosaccharides have more or less stored energy than the polypeptide or polysaccharide that they were broken down from?
Is it proper to call the isolated process of "hydrolysis" of proteins and polysaccharides "catabolic"?
Are protein synthesis, glycogen synthesis, (and triglyceride formation), by dehydration synthesis processes that require energy or release energy. I think that they release energy which is semantically interesting since protein and glycogen synthesis are the main examples of anabolism in the body but may actually release energy which is a key component of the definition of catabolism. Even if the energy released from protein synthesis is not generating ATP directly, wouldn't the heat produced conserve ATP in the long run.
1) Is the process of hydrolysis that breaks up polypeptides and polysaccharides a net endothermic or exothermic process?
Under physiological conditions, it is a process that goes forward, i.e. the Gibbs energy is negative. As a consequence, it can happen outside of cells in the absence of ATP. When we eat, the hydrolysis of polysaccharides starts in our mouths, while the hydrolysis of proteins occurs under harsher (acidic) conditions in the stomach and continues in the intestine (slightly basic conditions).
For warmblooded animals like us, exothermic or endothermic is less important, but you could look it up.
2) Do the free amino acids and monosaccharides have more or less stored energy than the polypeptide or polysaccharide that they were broken down from?
The following is multiple choice question (with options) to answer.
What is released when catabolic pathways break down complex molecules? | [
"oxygen",
"energy",
"hydrogen",
"food"
] | B | |
SciQ | SciQ-6384 | mass, density, volume
Title: Confused about volume, density and mass, help! I got into an argument with my friend, which cast confusion on my understanding of density and its relationship to volume. I'm hoping to get some clarity. The argument involved describing density in terms of volume. Let's say you define a sphere in empty space. You choose a point, apply the formula for a sphere, and now you have a sphere. Not a sphere OF anything other than space, just a spacial, theoretical sphere. No particles, massless or otherwise (this is a thought experiment). What is the density of that sphere? Is it zero, or is it undefined? I know density can be defined as p = m/v. But in a theoretical sphere, which HAS volume, should we call mass zero, because there is none? Or is it undefined because a theoretical sphere really isn't related to mass at all? If it IS undefined, does that mean it makes no sense to relate density to volume because density is only a property of mass?
The answer, to me, seems to be that in fact it makes no sense to talk about the density of a massless object. Sorry if I answered my own question, but I would still like clarity. If someone could help guide me through the assumptions I'm making about reality and math and how they relate, I'd really appreciate it. Theoretically speaking, in order for something (usually particles) to be massless, it has to be travelling in the speed of light. In quantum theory, uncertainty principle states that the position and momentum of such particle cannot be accurately determined, therefore it is not possible to measure the volume of the particle. So it is generally assumed that the volume is too small and/or insignificant.
Regarding your question, I think that the simple answer would be; a massless object would have no volume nor density, or immeasurable. Take your pick.
The following is multiple choice question (with options) to answer.
Mass and volume are examples of what kind of properties? | [
"extensive properties",
"dynamic properties",
"varied properties",
"exclusive properties"
] | A | Mass and volume are examples of extensive properties. |
SciQ | SciQ-6385 | zoology, entomology
Title: How do insects know what is edible? What is the current scientific consensus on how insects innately know what is food and not food? If they are introduced to new food sources do they experiment with eating the new food? Could you teach a preying mantis to eat beef? Insect feeding behaviour is generally triggered by one or more conditions which may include colour, shape, chemical traces or temperature.
Insects generally locate food based on some combination of olfactory, thermal and visual queues (colour and shape). If their minimum criteria are met to specified tolerance, they will attempt to feed on whatever is nearby using their usual feeding method.
When these conditions appear on the 'wrong' target, it attracts insects and triggers feeding attempts. Insects can be triggered to feed on atypical food sources if the relevant aspects of their environment match those of their normal feeding environments. For example, here is a report from a professor of entomology recollecting his observations of being bitten by pea aphids while handling plants, which he assumes is because of the scent on his hands.
We can exploit this in various ways for research. One is for artificial blood-feeding of insects: most systems, like the Hemotek membrane feeding system, warm blood to the body temperature of the host. They do not normally resemble a target host in any other way. Some blood-feeding insects have very specific requirements for temperature (for example they will only feed on blood if it is heated to the body temperature of birds; the same blood heated to mammalian body temperature will be ignored) but we do not need to make the target look or smell like the natural host. Other species may need olfactory cues, which can be provided by researchers rubbing the membranes on their forearms before placing them on the feeding system, or by breathing on cages as you add the food.
A second way we exploit this is for insect traps. Although not all traps work this way, some work by mimicking the host and attracting insects that are looking for a meal. This can be via olfactory/chemical mimicry (for example carbon dioxide baited traps - try Googling "CO2-baited traps") or visual. Different degrees of visual 'deception' may be needed; for instance to attract tsetse flies, colour is important but shape is not:
The following is multiple choice question (with options) to answer.
What technique is used by insects and birds to find food, mates, and safety from predators? | [
"mating",
"sleeping",
"playing",
"flying"
] | D | Other than insects, virtually no other animals can inhabit the airy world. Flying is a sure-fire way to escape from all but the quickest nonflying predators. Flying also gives birds a good view for finding food and mates. |
SciQ | SciQ-6386 | thermodynamics, heat
Title: Calculating Heat Release from Bomb calorimeter
When $0.400\ \mathrm g$ $\ce{CH4}$ is burned in excess oxygen in a bomb calorimeter that has a heat capacity of $3245\ \mathrm{J/^\circ C}$ a temperature increase of $6.795\ \mathrm{^\circ C}$ is observed. What is the value of $Q_V$?
I thought it was the regular $Q=mc\Delta T$ problem but it isn't and not only that I did the equation but it didn't work.
I am not sure what to do right here at the moment
Using the data determine standard enthalpy change for the combustion of methane
Also I would like the definition of the standard enthalpy change and what it tells you and the purpose of it. Heat of combustion is the amount of heat (enthalpy) liberated when 1 mole $\ce{CH4}$ reacts (combusts) with oxygen.
In other words, what is the heat of reaction in this case?
$\ce{CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l)}$
Then you must ask yourself, what happens after the heat is produced i.e. where does it go? It quickly turns into an accounting problem...
Take a look at: Constant Volume Calorimetry
The following is multiple choice question (with options) to answer.
What property of food is determined by burning the food and measuring the heat released? | [
"nutrients",
"acidity",
"additives",
"calories"
] | D | Food calories are determined by burning the food and measuring the heat released. |
SciQ | SciQ-6387 | classical-mechanics
Title: Help me find flaws on my simple machines invention I have a work to make an invention on simple machines. First of all I am sorry if my English is not very good or clear. As we all know, simple machines are used to simplify things in life and use less work (mechanical advantage). My concept is using a pulley to pull things up, but I want to use like a machine that needs to be stepped (lever type 3) to move the pulley. But I feel like there is a flaw to my invention, and feel very frustated. This is my concept visualization:
P.S: Sorry for the language usage (Image is semi-English and semi-Indonesian language)
Thank you for the help. The idea of simple machines is usually "sacrifice length to gain force". Or the opposite, but more rarely. You have incorporated a level and pulleys in your design. Let's analyze those.
The lever
The first problem is that you have made a lever that, if you step on it, the weight will go down. But, it would already go down by gravity, this is not useful. You probably want to counteract gravity and make it go up, so something like this:
The other problem is the general idea of using a level with your foot. The thing is, you can't move your foot much. This means do not really have length to sacrifice to gain force. So, to use a lever with your foot, you have to either:
Use it to lift something very light with a single motion of the foot. It's hard to find a use for this, though. Also, it means that the edge of the lever would be really long a take much space.
Use it to lift a heavy weight, but your foot won't have enough room. To gain multiple times one floor's height, you'd probably want to jump from some roof:
Now that we got the lever "solved", let's discuss the pulley (which is much easier for you to do without being unrealistic).
Note that just having a pulley somewhere doesn't provide you an advantage. You have to use something like a snatch block:
This will indeed allow you to use a long rope to raise the weight with less effort:
The following is multiple choice question (with options) to answer.
What simple machine works with a wheel and axle in a wheelbarrow? | [
"blade",
"lever",
"hammer",
"pulley"
] | B | Look at the wheelbarrow in the Figure below . It is used to carry heavy objects. It consists of two simple machines: a lever and a wheel and axle. Effort is applied to the lever by picking up the handles of the wheelbarrow. The lever, in turn, applies upward force to the load. The force is increased by the lever, making the load easier to lift. Effort is applied to the wheel of the wheelbarrow by pushing it over the ground. The rolling wheel turns the axle and increases the force, making it easier to push the load. |
SciQ | SciQ-6388 | gazebo
Title: What are the various joint types available in gazebo?
Revolute, prismatic, continuous and what else?
Could somebody point me to the right resource to look at to get such information.
Thanks.
Originally posted by pmaini on Gazebo Answers with karma: 33 on 2014-12-09
Post score: 3
You can find the joint types supported by SDF in the SDF documentation:
The type of joint, which must be one
of the following: (revolute) a hinge
joint that rotates on a single axis
with either a fixed or continuous
range of motion, (gearbox) geared
revolute joints, (revolute2) same as
two revolute joints connected in
series, (prismatic) a sliding joint
that slides along an axis with a
limited range specified by upper and
lower limits, (ball) a ball and socket
joint, (universal), like a ball joint,
but constrains one degree of freedom,
(piston) similar to a Slider joint
except that rotation around the
translation axis is possible.
Originally posted by NickDP with karma: 186 on 2014-12-09
This answer was ACCEPTED on the original site
Post score: 6
The following is multiple choice question (with options) to answer.
What type of joint has the greatest range of motion? | [
"Pivot",
"ball-and-socket",
"Gliding",
"Hinge"
] | B | There are a variety of types of movable joints, which are illustrated in Figure below . The joints are classified by how they move. For example, a ball-and-socket joint, such as the shoulder, has the greatest range of motion, allowing movement in several directions. Other movable joints, including hinge joints such as the knee, allow less movement. |
SciQ | SciQ-6389 | diffusion
The reverse process is also happening with molecules diffusing from right to left at a rate proportional to their concentration in the right side solution. As the concentration on the right side increases to be equal to the concentration on the left, so the diffusion rates become equal and there is zero nett diffusion and the system approaches equilibrium.
Note that this assumes a "perfect" system where there is no chemical reaction occurring between the solutes or between the solutes and the membrane. In practice this means that either the interaction between solutes A and B is the same as the interaction between the solutes and the solvent or that the solute molecules are so greatly outnumbered by the solvent molecules that the solute-solute interactions are not significant.
The rate of diffusion of solute A may be different from B (i.e. the proportionality constant between rate and concentration may be different). This means that before reaching equilibrium the relative concentrations of A and B may change but at equilibrium, the relative concentration will be the same as initially.
If we define "reaching equilibrium" as having some fraction (say 99.99%) of the final concentration then increasing the initial global concentration will increase the lag for both solutes equally and will not change their relative concentrations.
The following is multiple choice question (with options) to answer.
What is the movement of molecules from an area of high concentration of the molecules to an area with a lower concentration? | [
"condensation",
"secretion",
"diffusion",
"absorption"
] | C | Diffusion is the movement of molecules from an area of high concentration of the molecules to an area with a lower concentration. The difference in the concentrations of the molecules in the two areas is called the concentration gradient . Diffusion will continue until this gradient has been eliminated. Since diffusion moves materials from an area of higher concentration to the lower, it is described as moving solutes "down the concentration gradient. " The end result of diffusion is an equal concentration, or equilibrium , of molecules on both sides of the membrane. |
SciQ | SciQ-6390 | cardiology, implantation
Title: About a mechanical aid to the heart I saw a news story a few years ago (I think) about a girl with a poor heart having a device implant that took over only some of the functioning of her heart ( I think they called it a piggy-back device , or something like that). The extraordinary thing is that it not only helped her live but all the heart functions started to improve. It was as if giving part of the heart a chance to 'rest' allowed the whole heart to improve. If this procedure works could it be applied to other organs? Could a Piggy-Back device be made for the liver taking over only some of its functions for instance? Could such a thing help the liver functions to 'regenerate'? The function of heart is just to pump blood and nothing else. Though, it is a vital organ, its functions are limited. The device that you are talking about is a battery powered mechanical pump that performs the same function as heart.
Liver, however has a more complex function. One of its function is to synthesize and secrete certain molecules. A small artificial device cannot do that (you would need a bioreactor !!!).
We still haven't developed and artificial cell. Perhaps a consortium of bacteria can do some of the liver's functions but to culture them in right proportions and implant them without the risk of infection or their elimination is almost impossible as of now. You can clearly see that there are too many steps to be optimized.
The following is multiple choice question (with options) to answer.
Light-weight air-filled bones and a large four-chambered heart helps a bird do what? | [
"swim",
"digest",
"run",
"fly"
] | D | Bird organ systems are adapted for flight. For example, they have light-weight air-filled bones and a large four-chambered heart. |
SciQ | SciQ-6391 | biochemistry, biophysics, muscles, protein-folding
Now, returning to the main point (results & discussion sections):
The equilibrium and rates of transition between the Strong-ADP and the Rigor states vary greatly among different myosin isoforms and predominantly determine how long a myosin motor can remain bound to actin in the absence of load. This kinetic tuning must be achieved by structural differences in the regions that we have seen to change in our Strong-ADP structure as well as regions involved in stabilizing the lever arm position...Our structures show that the Loop 1 conformation alters in the transition from Strong-ADP to Rigor. Thus, different sequences likely favor one conformation over the other, or promote the transition from the ADP-bound conformation to the Rigor conformation, providing a structural basis for this kinetic tuning.
For myosins, such as myosin V, that function in a cell as two-headed, processive motors, the length of processive runs and the initiation of processive runs are both enhanced by “gating” of the heads. For a two-headed molecule with both heads simultaneously attached to actin, gating refers to the fact that a lead head is essentially stalled in an ADP state strongly bound to actin, until the rear head is detached from actin by binding MgATP. This gating is attributable to the strain dependence of MgADP release. Although we do not know whether some of the subdomains of myosin may be deformed by strain, our Strong-MgADP actomyosin structure clearly reveals that strain must prevent the rearrangement of the $\beta$-sheet from the Strong-MgADP conformation to the Rigor conformation, based on the data presented in Results. Preventing this rearrangement is thus the basis of gating.
For better understanding, you should also see this video (same website) which shows animation of different conformations of myosin in different stages of the cycle:
The following is multiple choice question (with options) to answer.
The myod protein deserves its designation as a master regulatory what? | [
"hormone",
"gene",
"protein",
"enzyme"
] | B | Some organisms can reproduce sexually or asexually. Under what conditions might each type of reproduction be an advantage?. |
SciQ | SciQ-6392 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
When flagellated sperm must swim to the egg, sexual reproduction requires the presence of what substance? | [
"nitrogen",
"air",
"water",
"sunshine"
] | C | The male gametophyte produces flagellated sperm that must swim to the egg formed by the female gametophyte. For this reason, sexual reproduction must happen in the presence of water. Therefore, nonvascular plants tend to live in moist environments. Though the life of a nonvascular seedless plant is a cycle, this can be considered the initial step in the life cycle. |
SciQ | SciQ-6393 | genetics, cell-biology, chromosome, meiosis, mitosis
https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/phases-of-meiosis
So, during metaphase I, homologue pairs—not individual
chromosomes—line up at the metaphase plate for separation.
The following is multiple choice question (with options) to answer.
What consists of these five stages: prophase, prometaphase, metaphase, anaphase, and telophase? | [
"mitosis",
"germination",
"meiosis",
"evolution"
] | A | 6.2 The Cell Cycle The cell cycle is an orderly sequence of events. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages. In eukaryotes, the cell cycle consists of a long preparatory period, called interphase. Interphase is divided into G1, S, and G2 phases. Mitosis consists of five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis is usually accompanied by cytokinesis, during which the cytoplasmic components of the daughter cells are separated either by an actin ring (animal cells) or by cell plate formation (plant cells). Each step of the cell cycle is monitored by internal controls called checkpoints. There are three major checkpoints in the cell cycle: one near the end of G1, a second at the G2–M transition, and the third during metaphase. |
SciQ | SciQ-6394 | muscles, lungs, human-physiology
Title: Why is there smooth muscle in our bronchioles? Having muscle tissue in our bronchioles that can constrict seems like a poor choice for tissue. Why would our airway want to ever close up? Wouldn't it be more beneficial for our bronchioles to just remain open? There are at least two things to consider.
First, ability to limit airflow is a defense mechanism for animal. Imagine getting into area of some sort of toxic evaporation, e.g. CO2 cloud near volcano , then it makes sense to decrease delivery of toxin via lungs to minimum. As I understand, that is what an allergic asthma attack. (Sorry for not providing good enough source of that)
Secondly, you are incorrect in assuming that normal state is "dilated". Dilation of branchioles is sympathetic ("fight-and-fly") response of the nervous system to something like danger, that requires short-term boost in energy production. That is, by default, your airflow is limited. Probably, to limit amount of energy you effectively burn via oxygenation. But most importantly, you leave yourself a reserve in terms of oxygen supply for critical moments.
Some more information you might find here.
The following is multiple choice question (with options) to answer.
What is the name of the muscle at the end of the esophagus? | [
"sphincter",
"throat",
"neck",
"intestine"
] | A | From the pharynx, the food moves into the esophagus. The esophagus is a long, narrow tube that passes food from the pharynx to the stomach by peristalsis. The esophagus has no other digestive functions. At the end of the esophagus, a muscle called a sphincter controls the entrance to the stomach. The sphincter opens to let food into the stomach and then closes again to prevent food from passing back into the esophagus. |
SciQ | SciQ-6395 | waves, oscillators, string
Is the principal the same as for the transverse waves? There is a few reasons why I can't really see that working: the rotational waves in this case are sometimes so large that the flat part goes vertical (i.e. against the wind) or even rotates by multiple revolutions.
The most important one: Why is the wavelength of the rotation waves (i.e. the separation of the nodes as can be seen in the picture) so much lower than for the transverse waves? This is an observation that is not obvious from the picture, but usually there are only like 3 or 4 oscillations nodes for the transverse ones and like 30 for the rotational ones.
The question will get too broad if I ask more questions about this, so let's focus on the above. I am generally interested in this phenomenon and there are other questions I can't quite answer (e.g. when it is not very windy there aren't any oscillations and sometimes when the wind is weak oscillations come and go. So why is there a "critical wind speed" at which they start resonating up?). I'm having a problem visualizing the transverse waves with 3 or 4 nodes you mention. All videos I've found show standing waves with only two nodes, the slackline moving up and down between the anchor points (or between an anchor point and the person walking the slackline).
The rotation waves I saw (maybe torsion oscillation is a better name) also had only two nodes. The "nodes" in the picture aren't actual nodes, they are points where the twist angle corresponds to the viewing angle. If the middle of the line makes (a bit more than) seven complete rotations, you'll have 14 positions on the left and on the right where the rotation is a multiple of 180 degrees, giving you 28 visual points. Their number indicates the amplitude of the torsional oscillation rather than the number of nodes.
The following is multiple choice question (with options) to answer.
What do you call the high and low points of transverse waves? | [
"bands and troughs",
"crests and troughs",
"echos and troughs",
"waves and troughs"
] | B | In a transverse wave, such as a wave in a rope, the medium vibrates at right angles to the direction that the wave travels. The high points of transverse waves are called crests, and the low points are called troughs. |
SciQ | SciQ-6396 | 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.
For each initial glucose molecules, two pyruvate molecules will enter where? | [
"the mitochondria",
"Golgi apparatus",
"the plasma",
"the nucleus"
] | A | Aerobic respiration begins with the entry of the product of glycolysis, pyruvate, into the mitochondria. For each initial glucose molecules, two pyruvate molecules will enter the mitochondria. Pyruvate, however, is not the molecule that enters the Krebs cycle. Prior to entry into this cycle, pyruvate must be converted into a 2-carbon acetyl-CoenzymeA (acetyl-CoA) unit. The conversion of pyruvate into acetyl-CoA is referred to as the pyruvate dehydrogenase reaction. It is catalyzed by the pyruvate dehydrogenase complex. This process produces one NADH electron carrier while releasing a CO 2 molecule. This step is also known as the link reaction or transition step, as it links glycolysis and the Krebs cycle. Of course, as two pyruvates result from glycolysis, two acetyl-CoAs are produced as are 2 NADH molecules. |
SciQ | SciQ-6397 | 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.
Through which artery does blood enter the kidneys? | [
"jugular",
"thoracic artery",
"cerebral artery",
"renal artery"
] | D | 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-6398 | waves, electromagnetic-radiation
(Image Credit: https://www4.uwsp.edu/physastr/kmenning/Phys202/Lect16.html)
The following is multiple choice question (with options) to answer.
Where do radio waves lie on the electromagnetic spectrum? | [
"far right",
"top",
"far left",
"middle"
] | C | Courtesy of NASA. Radio waves lie at the far left of the electromagnetic spectrum . Public Domain. |
SciQ | SciQ-6399 | ecology, population-dynamics, ecosystem, antipredator-adaptation, predation
I would also like to talk about other things that might be of interest in your model (two of them need you to allow evolutionary processes in your model):
1) lineage selection: predators that eat too much end up disappearing because they caused their preys to get extinct. This hypothesis has nothing to do with some kind of auto-regulation for the good of species. Of course you'd need several species of predators and preys in your model. This kind of hypothesis are usually considered as very unlikely to have any explanatory power.
2) Life-dinner principle. While the wolf runs for its dinner, the rabbit runs for its life. Therefore, there is higher selection pressure on the rabbits which yield the rabbits to run in average slightly faster than wolves. This evolutionary process protects the rabbits from extinction.
3) You may consider..
more than one species of preys or predators
environmental heterogeneity
partial overlapping of distribution ranges between predators and preys
When one species is absent, the model behave just like an exponential model. You might want to make a model of logistic growth for each species by including $K_x$ and $K_y$ the carrying capacity for each species.
Adding a predator (or parasite) to the predator species of interest
... and you might get very different results.
The following is multiple choice question (with options) to answer.
What links the trophic levels from producers to top carnivores? | [
"environments",
"fuel chains",
"ecosystems",
"food chains"
] | D | |
SciQ | SciQ-6400 | botany, ecology, digestion, climate-change
The timing of residence times and flux rates (i.e., movement from one place to another) dictate whether a reservoir acts as a source or sink.
CO2 (carbon dioxide) and CH4 (methane) are quite different in the reactions from which they are generated (see Would fewer cows mean less methane emission?), the rate at which they are generated, and ultimately in their chemistry. This last point has drastic impacts on residence times, flux rates, and ultimately their their climate warming impacts:
Both molecules differ in their residence times in the atmosphere as well as their magnitude of radiative forcing. From MIT:
methane immediately begins to trap a lot of heat—at least 100 times as much as the CO2. But the methane starts to break down and leave the atmosphere relatively quickly. As more time goes by, and as more of that original ton of methane disappears, the steady warming effect of the CO2 slowly closes the gap. Over 20 years, the methane would trap about 80 times as much heat as the CO2. Over 100 years, that original ton of methane would trap about 25 times as much heat as the ton of CO2.
Note, also, that some of the atmospheric methane will eventually be chemically converted to carbon dioxide. From here.
Methane enters the atmosphere and eventually combines with oxygen (oxidizes) to form more CO2. Methane converts to CO2 by this simple chemical reaction.
Regarding methane production of cows and rates of release of greenhouse gasses, please see my other recently-answered BIO.SE post: Would fewer cows mean less methane emission?
Regarding carbon storage:
As stated above, understanding the carbon cycle requires both an understanding of residence times and flux rates. To determine the carbon storage ability of one biome or environment vs another, we typically measure the biomass of the organic matter (with interest in determining the C:N ratio) as well as flux rates in/out of our target carbon reservoir (e.g., plants such as crops or trees). Regarding flux rates, of particular interest are rates of carbon sequestration.
Ultimately, any community of plants that is capable of sequestering more carbon into large amounts of high-C:N biomass will result in larger carbon storage. The longer-lived those plants (i.e., the less labile their carbon), the longer that community of plants acts as a carbon sink.
The following is multiple choice question (with options) to answer.
The waste of cows releases a lot of which type of gas? | [
"methane",
"sulphur",
"carbon dioxide",
"oxygen"
] | A | Volatile organic compounds (VOCs) are carbon compounds such as methane. VOCs are released in many human activities, such as raising livestock. Livestock wastes produce a lot of methane. |
SciQ | SciQ-6401 | zoology, ecology
Giraffes' this is an energy saving feature. Giraffes don't need to use muscles to hold their neck. They just use when flexing their necks down, when drinking water etc.
According to Wikipedia, for an alternative hypothesis Ouranosaurus have a hump. (Other hypothesis is display sail or termoregulation sail of course. Also spinosaurus have this kind of alternative hypotesis but this hypothesis not accepted much as sail. and spinosaurus' spine different from bisons. Bison spines concentrating at shoulder but spinosaurs' not at the shoulder. You can find spinosaurus info from this page.)
The following is multiple choice question (with options) to answer.
What allows giraffes to reach leaves that other ground animals cannot? | [
"long horns",
"camouflage pattern",
"long necks",
"long tongue"
] | C | African Giraffes. Giraffes feed on leaves high in trees. Their long necks allow them to reach leaves that other ground animals cannot. |
SciQ | SciQ-6402 | acid-base, ionic-compounds, erratum
Title: Are all ionic compounds salts? According to Wikipedia:
A salt is an ionic compound that can be formed by the neutralization
reaction of an acid and a base.
Are all ionic compounds salts? Are all salts ionic compounds? Interestingly, IUPAC states that a "salt" is "a chemical compound consisting of an assembly of cations and anions". Under this definition, all ionic compounds are salts, and all salts are ionic compounds.
Therefore, something like sodium hydroxide ($\ce{Na+OH-}$, definitely an ionic compound) could actually be correctly called a salt. This clashes with the commonly taught high-school level definition of a salt ("the product of an acid-base reaction"), unless you consider very general definitions of acids and bases such as the Usanovich definition, whereby sodium metal $\ce{Na^0}$ is an electron donor (and therefore a base) and water is an electron acceptor (and therefore an acid).
That said, the high-school definition is too simplistic. It is common for compounds to be an acid, a base and a salt all at the same time; consider for example sodium bicarbonate ($\ce{Na+HCO3-}$). It is made of cations and anions, and therefore is definitely a salt. Furthermore, it can act as both a Brønsted–Lowry acid ($\ce{NaHCO3 + OH- -> H2O + Na+ + CO3^2-}$) and as a Brønsted–Lowry base ($\ce{NaHCO3 + H+ -> Na+ + H2CO3}$). Another amusing example is hydrazinium sulfate, a salt, acid and base, where both the cation and anion are also both acids and bases!
The following is multiple choice question (with options) to answer.
Chemical formulas for ionic compounds are called what? | [
"magnetic formulas",
"electronic formulas",
"ionic formulas",
"velocity formulas"
] | C | Chemical formulas for ionic compounds are called ionic formulas. A proper ionic formula has a cation and an anion in it; an ionic compound is never formed between two cations only or two anions only. The key to writing proper ionic formulas is simple: the total positive charge must balance the total negative charge. Because the charges on the ions are characteristic, sometimes we have to have more than one of a cation or an anion to balance the overall positive and negative charges. It is conventional to use the lowest ratio of ions that are needed to balance the charges. For example, consider the ionic compound between Na+ and Cl−. Each ion has a single charge, one positive and one negative, so we need only one ion of each to balance the overall charge. When writing the ionic formula, we follow two additional conventions: (1) write the formula for the cation first and the formula for the anion next, but (2) do not write the charges on the ions. Thus, for the compound between Na+ and Cl−, we have the ionic formula NaCl (Figure 3.5 "NaCl = Table Salt"). The formula Na2Cl2 also has balanced charges, but the convention is to use the lowest ratio of ions, which would be one of each. (Remember from our conventions for writing formulas that we don’t write a 1 subscript if there is only one atom of a particular element present. ) For the ionic compound between magnesium cations (Mg2+) and oxide anions (O2−), again we need only one of each ion to balance the charges. By convention, the formula is MgO. For the ionic compound between Mg2+ ions and Cl− ions, we now consider the fact that the charges have different magnitudes, 2+ on the magnesium ion and 1− on the chloride ion. To balance the charges with the lowest number of ions possible, we need to have two chloride ions Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-6403 | electromagnetism, electromagnetic-radiation, magnetic-fields, dimensional-analysis, unit-conversion
%\Rightarrow
\textrm{max. power in the range [0, 1.6]GHz} &: -90dBm/MHz \cdot (1.6 - 0)GHz = \ldots
\\
\textrm{max. power in the range [1.6, 2.7]GHz} &: -85dBm/MHz \cdot (2.7-1.6)GHz = \ldots \\
\ldots
\end{align}
The following is multiple choice question (with options) to answer.
What term is used to describe the full range of electromagnetic waves? | [
"mechanical spectrum",
"electromagnetic scale",
"electromagnetic spectrum",
"electromagnetic series"
] | C | Electromagnetic waves vary in their wavelength, frequency, and energy. The full range of electromagnetic waves makes up the electromagnetic spectrum. |
SciQ | SciQ-6404 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
How many lobes is each hemisphere of the cerebrum divided into? | [
"5",
"9",
"4",
"2"
] | C | Each hemisphere of the cerebrum is divided into four parts, called lobes. The four lobes are the:. |
SciQ | SciQ-6405 | hematology, cardiology, blood-circulation, red-blood-cell, veins
Veins are not like impermeable rubber tubes, they are 'living' structures requiring, like all cells, Oxygen and glucose to survive. Smaller veins get the O2 from diffusion, while the larger veins need help from vasa vasorum, small blood bessels that bring blood to the walls of the veins.
The innermost cells lining veins are epithelial cells. They also line valves.
In the picture you posted, blood is not circulating well behind valves. The cause of hypoxia is that epithelial cells are continually removing O2 from the blood.
When enough O2 is removed to cause hypoxia, the endothelial cells may become damaged by the lack of O2, causing inflammation and (possibly) potentiating clot formation.
Activation of endothelial cells by hypoxia or possibly inflammatory stimuli would lead to surface expression of adhesion receptors that facilitate the binding of circulating leukocytes and microvesicles. Subsequent activation of the leukocytes induces expression of the potent procoagulant protein tissue factor that triggers thrombosis.
Mackman N. (2012). New insights into the mechanisms of venous thrombosis. The Journal of clinical investigation, 122(7), 2331–2336. doi:10.1172/JCI60229
The following is multiple choice question (with options) to answer.
Varicose veins are veins that become enlarged because the valves no longer do this? | [
"open properly",
"close properly",
"enlarge properly",
"shrink properly"
] | B | Blood travels through the bicuspid valve to the left atrium. Both the aortic and the pulmonary valves are semilunar valves. The mitral valve is an atrioventricular valve. Figure 40.17 Varicose veins are veins that become enlarged because the valves no longer close properly, allowing blood to flow backward. Varicose veins are often most prominent on the legs. Why do you think this is the case?. |
SciQ | SciQ-6406 | intermolecular-forces, boiling-point, dipole
Title: Why are the dispersion forces in CS2 stronger than the dipole-dipole forces in COS? London dispersion forces supposedly have the least strength out of all the intermolecular forces. But $\ce{CS2}$, which has only dispersion forces, has a higher boiling point (and thus stronger intermolecular forces) than $\ce{COS}$, which has dipole-dipole attraction in addition to dispersion forces. Why is this?
I suppose that it has something to do with $\ce{CS2}$ having a thicker/more inducible electron shell, but then a new question arises: how would you know if the dispersion forces in one molecule are stronger that the dipole-dipole forces in another?
(Theoretically, without using boiling points or other experimental data. Also, this is based on question 4a from the 2018 AP chemistry free response.) Although individual dispersion forces are weak, they are cumulative, and increase with molar mass. As a general rule, boiling point increases with molar mass.
Polar molecules will have higher boiling points when compared to molecules with similar molar masses. For example, ethanol($\ce{CH3CH2OH}$) has a higher boiling point than dimethyl ether ($\ce{CH3OCH3}$).
$\ce{CS2}$ is ~16 g/mol heavier than COS.
The following is multiple choice question (with options) to answer.
Liquids with strong intermolecular forces have higher what than liquids with weaker forces? | [
"freezing point",
"temperature",
"surface tension",
"melting point"
] | C | Liquids with strong intermolecular forces have higher surface tensions than liquids with weaker forces. |
SciQ | SciQ-6407 | earthquakes, plate-tectonics, volcanoes, tectonics
Title: What tectonic mechanisms cause the North and South Islands of New Zealand to be so geologically different? New Zealand is a very active seismic and volcanic region of the Pacific Ring of Fire, on the boundary of the Australian and Pacific Plates; however, there is a difference between the 2 islands: volcanoes and earthquakes on the North Island and earthquakes only on the South Island (see maps below):
Location of New Zealand volcanoes
(Image source)
New Zealand Earthquake Map
(Image Source)
What are the tectonic features that account for the difference between the North and South Islands?
Additionally, how will this boundary develop in the future (geologically speaking)? New Zealand sits along an oblique convergent plate boundary, where the Pacific and Australia Plates meet. The boundary between the two plates is shown in your second figure as the grey line, with the Pacific Plate to the east and the Australia Plate to the west of it. In terms of relative movement, we can think of the Australia Plate as being stationary and the Pacific Plate having a west to south-west direction of movement. The angle at which the Pacific Plate moves into the Australia plate changes along the length of New Zealand - this is what causes the differences in tectonic style and thus differences in volcanism and earthquake occurance (and motion) between North and South Islands. The angle changes from north to south due to:
a clockwise rotation of the Pacific Plate, and
Pacific and Australia plates meeting at varying angles.
The following is multiple choice question (with options) to answer.
What kind of volcanoes often form along divergent plate boundaries? | [
"dome",
"composite",
"crest",
"shield"
] | D | Shield volcanoes often form along divergent plate boundaries. They also form at hotspots, like Hawaii. Shield volcano eruptions are non-explosive. |
SciQ | SciQ-6408 | notation, formal-charge
For the historical perspective, see the corresponding article by Jensen [2]:
In contrast, the German chemist, Walther Nernst, in his equally influential 1893 textbook of theoretical chemistry, chose to place an appropriate number of superscripted $+$ or $−$ signs directly above the ion’s atomic symbol (4), a practice which was soon modified by placing them instead to the immediate right of the symbol, as in $\ce{Ba^{++}}$ and $\ce{PO4^{---}}$(5).
The IUPAC guide to Quantities, Units and Symbols claims that yet a third “algebraic” method of indicating ionic charges was also used in the past in which the charge preceded the numerical value, as in $\ce{Ba^{+2}}$ and
$\ce{PO4^{-3}},$ even though this particular sequence of symbols was originally intended to represent the inherent sign of a number or exponent and not the number of signs (6). However, inspection of nearly three dozen general, inorganic, and analytical textbooks, spanning the period 1909–1975, revealed that the vast majority employed the modified Nernst notation, with a smaller number — mostly of European or Russian origin — using the Ostwald notation instead. Rather surprisingly, very few examples of texts using the algebraic notation could be found, all of them post-1970 (7).
Since at least the 1950s IUPAC has ruled that ionic charges or “charge numbers,” as they are now officially called, should be written instead with the number preceding the charge sign, as in $\ce{Ba^2+}$ and $\ce{PO4^3-}$
(6, 8, 9). There are several reasons for this decision. It is more concise than the typographically inelegant Nernst approach and more physically meaningful than the Ostwald notation. Unlike the algebraic notation, it
avoids confusion with the conventional symbolism for inherently positive and negative numbers and maintains consistency in how we count physical entities.
References
The following is multiple choice question (with options) to answer.
An element symbol without a charge written next to it is assumed to be what? | [
"dead atom",
"corroborate atom",
"surfactants atom",
"uncharged atom"
] | D | Third, there are some exceptions to the previous point. A few elements, all metals, can form more than one possible charge. For example, iron atoms can form 2+ cations or 3+ cations. Cobalt is another element that can form more than one possible charged ion (2+ and 3+), while lead can form 2+ or 4+ cations. Unfortunately, there is little understanding which two charges a metal atom may take, so it is best to just memorize the possible charges a particular element can have. Note the convention for indicating an ion. The magnitude of the charge is listed as a right superscript next to the symbol of the element. If the charge is a single positive or negative one, the number 1 is not written; if the magnitude of the charge is greater than 1, then the number is written before the + or − sign. An element symbol without a charge written next to it is assumed to be the uncharged atom. Naming an ion is straightforward. For a cation, simply use the name of the element and add the word ion (or if you want to be more specific, add cation) after the element’s name. So Na+ is the sodium ion; Ca2+ is the calcium ion. If the element has more than one possible charge, the value Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-6409 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
What is the fundamental unit of structure and function in all living organisms? | [
"the vessels",
"the spinal cord",
"the cell",
"the backbone"
] | C | the cell is the fundamental unit of structure and function in all living organisms,. |
SciQ | SciQ-6410 | newtonian-mechanics, forces, fluid-dynamics, reference-frames, drag
Title: Is drag force in the direction of particle motion or opposite to motion? Suppose water is flowing in horizontal direction (positive $x$-direction) and a particle immersed in that water is also moving in the same direction.
In this case, is the drag force $F_D$ in the direction of particle motion or opposite to it?
I get from wikipedia that drag force is a frictional force and hence is opposite to particle motion, but then what is the force that is making the particle move. Because in one journal paper, I see that drag force $F_D$ is shown as force in the direction of particle motion.
This is a sketch from the paper, you can see that flow velocity and drag force are both in the same direction. Drag force opposes the motion of a body relative to the surrounding fluid. In this case the surrounding fluid moves to the right and relative to that the solids move to the left.
The drag force is opposing the motion to the left, hence it is towards the right. The solids are being swept away by the fluid.
The following is multiple choice question (with options) to answer.
What characteristic of particles determines how they are carried by flowing water? | [
"size",
"texture",
"color",
"density"
] | A | The size of particles determines how they are carried by flowing water. This is illustrated in Figure below . |
SciQ | SciQ-6411 | cardiology, implantation
Title: About a mechanical aid to the heart I saw a news story a few years ago (I think) about a girl with a poor heart having a device implant that took over only some of the functioning of her heart ( I think they called it a piggy-back device , or something like that). The extraordinary thing is that it not only helped her live but all the heart functions started to improve. It was as if giving part of the heart a chance to 'rest' allowed the whole heart to improve. If this procedure works could it be applied to other organs? Could a Piggy-Back device be made for the liver taking over only some of its functions for instance? Could such a thing help the liver functions to 'regenerate'? The function of heart is just to pump blood and nothing else. Though, it is a vital organ, its functions are limited. The device that you are talking about is a battery powered mechanical pump that performs the same function as heart.
Liver, however has a more complex function. One of its function is to synthesize and secrete certain molecules. A small artificial device cannot do that (you would need a bioreactor !!!).
We still haven't developed and artificial cell. Perhaps a consortium of bacteria can do some of the liver's functions but to culture them in right proportions and implant them without the risk of infection or their elimination is almost impossible as of now. You can clearly see that there are too many steps to be optimized.
The following is multiple choice question (with options) to answer.
What term refers to something supplied by nature that helps support life? | [
"free resource",
"existing resource",
"simple resource",
"natural resource"
] | D | A natural resource is something supplied by nature that helps support life. When you think of natural resources, you may think of fossil fuels, like the coal in the coal field pictured in Figure below . However, sunlight, wind, soil, and living things are also important natural resources. |
SciQ | SciQ-6412 | the-sun, the-moon, solar-system, orbital-mechanics, natural-satellites
Title: Moons with curlicue paths around our Sun? I naively believed that since our Moon orbits Earth, and since Earth orbits the Sun, the path our Moon might take around the Sun would be this type of epitrochoid curve:
I was surprised and delighted to find that our Moon's orbit around the Sun actually forms a convex curve which is really darn close to Earth's orbital path: Moon's orbit around the Sun. Since the Earth's instantaneous velocity around the Sun is much greater than the Moon's instantaneous velocity around the Earth, we don't get any of the closed "curlicues" I expected to see.
Are there any moons in our solar system with epitrochoid paths around the sun that appear to have closed curlicues? If so, what are they and what do the paths look like? A moon will describe a path like this if its orbital speed relative to its parent planet is greater than the parent planet's orbital speed about the Sun. (Assuming the moon's orbit about the planet and the planet's orbit about the sun are roughly coplanar; I'll ignore Uranus for the remainder of this discussion.) Going through the planets:
Neptune: All moons from Proteus inwards (7 total) orbit Neptune sufficiently fast. However, they're all pretty small; in particular, all are irregularly shaped, since they're all too small to form into spheres under their own gravity.
Uranus: (ignored because the paths of the moons are just too baroque)
Saturn: All moons from Dione inwards (20 total), along with Dione's trojan moons Helene & Polydeuces, orbit Saturn sufficiently fast. This includes a few large & charismatic "pre-Voyager" moons: Mimas, Tethys, Enceladus, and Dione.
Jupiter: All moons from Europa inwards (6 known), including Io, orbit Jupiter sufficiently fast.
The following is multiple choice question (with options) to answer.
What is the shape of the orbits that planets make around the sun? | [
"conical",
"variable",
"elongated",
"elliptical"
] | D | The planets make slightly elliptical orbits around the Sun. |
SciQ | SciQ-6413 | parasitology
Title: Giardia lamblia cases of infections I am wondering if anyone has seen a data of Giardiasis (Giardia Lamblia) cases in different countries on the world? I have found for different diseases and also for 'diarrhoea diseases' in general, but I need especially for Giardia Lamblia.
Any suggestion where I can try to look for this data will be useful.
Thank you very much! If you have or can get access to it, you might try looking in the Incidence and Prevalence database: http://thomsonreuters.com/incidence-and-prevalence-database/
Another possibility is the GIDEON database: http://www.gideononline.com/. It is possible to sign up for a 15-day trial.
For Europe, statistics are available from the WHO CISID at http://data.euro.who.int/cisid/ (select "all infectious diseases", then "Giardiasis").
The WHO does not have any global statistics available on their website, so otherwise you might have to piece together data from individual publications. Some examples:
Thailand, 2005: http://www.ncbi.nlm.nih.gov/pubmed/16438174
Germany, 2006: http://www.ncbi.nlm.nih.gov/pubmed?term=19404678
United States, 2006-2008: http://www.cdc.gov/mmwr/preview/mmwrhtml/ss5906a2.htm
Portugal, 2002-2008: http://www.parasitesandvectors.com/content/5/1/22
Quatar, 2008: http://www.parasitesandvectors.com/content/4/1/211
Tajikistan, 2009: http://www.parasitesandvectors.com/content/4/1/195
Ivory Coast, 2009: http://www.parasitesandvectors.com/content/4/1/96
Tanzania, 2011: http://www.parasitesandvectors.com/content/6/1/3
Ghana, 2006-2009: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3170632/?report=classic
The following is multiple choice question (with options) to answer.
What are chlamydia, gonorrhea, and syphilis an example of? | [
"metabolic disorders",
"viral stis",
"bacterial stis",
"genetic diseases"
] | C | A sexually transmitted infection (STI) is a disease that spreads mainly through sexual contact. STIs are more common in teens and young adults than in older people. Bacterial STIs include chlamydia, gonorrhea, and syphilis. Viral STIs include genital warts, genital herpes, and AIDS. |
SciQ | SciQ-6414 | lab-techniques
In addition to using a cryoprotectant, the rate of cellular dehydration during the freezing process can be managed by using a -1°C/minute cooling rate
Thawing should be rapid at 37°C
ThermoFisher recommends a high cell density as cell death will occur no matter what :
Also, the greater the cell density, the better the recovery is after thawing the cells. For most bacteria, a density of 107 cells/mL will result in adequate recovery if all conditions are properly maintained.
Cell death during storage is inevitable but should be minimized as much as possible
The number of freeze/thaw cycles is critical and thawing even partial should be avoided :
Try not to freeze/thaw your glycerol stock too many times. Placing the glycerol stock on dry ice while streaking onto LB agar will prevent it from thawing completely and will improve the shelf life. from addgene.org
Coming back to the initial question, based on the information above and some of the feedback in this discussion stocks of the typical E. coli DH5-&\alpha& stored at - 80 °C would probably last up to 2 or 3 decades maybe more but depending how you make them and use them it can be much less. To go further, depending on your workflow you may want to consider having working and stock vials to limit the number or freeze thaw cycles or using freeze-dried stocks for longer term storage.
Edit : One thing to keep in mind too is that frozen stocks shelf life is not all about cell viability upon thawing but also about "cell integrity". As mentioned by She and Petti (2015), van Griethuysen et al. have observed the loss of the mecA genes in 2 years old Staphylococcus aureus isolates frozen stocks.
The mecA gene was lost in 36 (14.4%) of 250 methicillin-resistant Staphylococcus aureus isolates after 2 years of storage at −80°C with the Microbank system (Pro-lab Diagnostics, Austin, Tex.). Further analysis of 35 of these isolates confirmed loss of the mecA gene in 32 isolates. This finding has important implications for the management of strain collections.
I personally experience a similar issue with a routinely used strain that lost its adhesive phenotype so we had to use the backup stock.
References :
The following is multiple choice question (with options) to answer.
What organism are resistant to freezing and drying and also are metabolically inactive? | [
"zygosporangia",
"trichina",
"spirogyra",
"giardia"
] | A | |
SciQ | SciQ-6415 | thermodynamics
Title: Does a gas condenses above its dew point? We all know that at temperatures much below the boiling point, evaporation occurs and liquid/vapor equilibrium exists.
So if we have steam at temperature greater than dew point, does it undergoes condensation at that temperature? Let's, for simplicity, consider a closed container with a liquid. In such closed system, evaporation and condensation happen simultaneously.
The rate of evaporation increases with temperature. The rate of condensation, which happens when vapor molecules hit the surface of the liquid, depends on the vapor pressure.
At equilibrium, the rates of evaporation and condensation are the same and the temperature is a dew point, by definition.
If the temperature is raised above that point, the rate of evaporation will exceed the rate of condensation, but, the condensation will still occur. This will continue until the new equilibrium is achieved, with the new temperature becoming a new dew point.
So, for a closed system, condensation does happen at temperatures above the dew point.
In an open environment, when the vapor does not come in contact with liquid, the condensation, generally, should not occur above the dew point.
The following is multiple choice question (with options) to answer.
What is produced during a condensation reaction? | [
"wind",
"rain",
"water",
"fire"
] | C | Condensation reactions are the chemical processes by which large organic compounds are synthesized from their monomeric units. Hydrolysis reactions are the reverse process. During condensation reactions, water is produced from the two molecules being bonded together; an H from one monomer is joined to an -OH from another molecule, producing H 2 O. |
SciQ | SciQ-6416 | newtonian-mechanics, newtonian-gravity, rotational-dynamics, angular-momentum
You are missing the fact that neither of those forces actually go through the center of the earth.
First, the contact force between the earth and the body has both a vertical and a horizontal component. This horizontal component arises from static friction and is often larger than the centripetal acceleration. This is the force, for example, that keeps the object from sliding down a hill or sliding around from a light breeze. It also provides whatever small force is needed for the centripetal motion.
Second, the earth is not uniform. There are variations in density and local features like mountains and so forth. All of these perturb the local gravitational vector so that it does not actually point towards the center of the earth. If you took those deviations and constructed a shape such that the surface is everywhere perpendicular to the local gravitational vector, that shape is called the geoid. That shape is, in some sense, the actual shape of the earth, and on it there would be no static friction. The force for the centripetal motion would come from the sum of the normal force and the local gravitational force, neither of which would necessarily point towards the center.
Now, suppose that we were not on the earth, but rather on a perfectly uniform density planet with the same mass and angular velocity as the earth. Suppose further that the planet is formed of some fluid so that there are no mountains or hills and that there is no wind or moons so there are no waves or tides. Such a planet would have everywhere a gravitational vector that points exactly to the center of the earth, and since it is a fluid the surface is everywhere normal to the local gravitational force so there is no horizontal forces. Now, on such an idealized planet the geoid would be an ellipsoid, and although the gravitational force would be through the geometric center, the normal force would not except at the equator and the poles. The sum of the center-directed gravitational force and the off-center normal force would give the required centripetal force.
The following is multiple choice question (with options) to answer.
What force pulls objects toward the center of the earth? | [
"gravity",
"momentum",
"kinetic energy",
"centrifugal force"
] | A | |
SciQ | SciQ-6417 | particle-physics, nuclear-physics, neutrons
Title: Are neutrons and protons stable inside atomic nuclei? Some people naturally assume that atomic nuclei are made of protons and neutrons. That is, they are basicly clumps of protons and neutrons that each maintain its separate existence, like pieces of gravel maintain their existence if you mold them together in a ball with mud for a binding force.
How come neutrons in a nucleus don't decay?
This is a natural assumption. A hydrogen nucleus can have one proton as its nucleus. Nuclei can absorb neutrons to become other isotopes. It's natural to assume that nuclei are clumps of protons and neutrons.
Sometimes if an atomic nucleus gets broken by application of large amounts of energy, typically applied with a fast-moving subatomic particle, they might release a neutron or a proton. So for example, smash an alpha particle into a beryllium nucleus and a neutron comes out. Doesn't that imply that the neutron was in there all along, waiting to get out?
But that reasoning implies that electrons, positrons, muons etc are also inside the nucleus all the time, waiting to get out.
There's an idea that protons and neutrons inside a nucleus swiftly transfer charges. This is analogous to a theory from organic chemistry, where sometimes single and double bonds switch back and forth, increasing stability. We could have quarks getting exchanged rapidly between protons and neutrons, increasing stability. I can see that as increasing stability for the nucleus, but I just don't see it as making the protons and neutrons more stable. If ten Hollywood couples get repeated divorces and marry each other's exes, you wouldn't say that the original marriages are stable.
In the extreme, the quarks might just wander around in a nuclear soup, and the protons and neutrons have no more identity than a bunch of used computers disassembled with the parts on shelves for resale. Maybe you could collect enough parts to take a working computer out of the store with you, but it probably won't be one of the old computers.
The following is multiple choice question (with options) to answer.
Where are protons and neutrons located? | [
"orbitals",
"central nucleus",
"outside the nucleus",
"secondary nucleus"
] | B | Protons and neutrons are located in a central nucleus, while electrons orbit about the nucleus. |
SciQ | SciQ-6418 | ecology, biodiversity
Title: Species-area relation graph When species richness is plotted vs area, the graph follows the equation : log S = log C + Z log A where Z is the slope of the line. Z values are usually in the range of 0.1 to 0.2 but if very large areas like entire continents are analyzed, the slope is much steeper. (0.6-1.2).
Why is it so ?
(Here S = species richness and A= area under consideration) Z value is a fitted constant and it ranges between 0.1 to 0.3 regardless of the region or taxonomic groups.i.e. the slope is almost similar .Among larger areas like continent,the slope tends to be much steeper.becoz, Larger the area larger will be number of species(species richness),for larger areas the Z values tends to be 0.6 to 1.2.(NOTE:if Z is less,lesser area is enough to capture more species).
The following is multiple choice question (with options) to answer.
What is a measurement of the amount of variation of the species in a given area called? | [
"degradation",
"ecosystem",
"population",
"biodiversity"
] | D | Biodiversity is a measurement of the amount of variation of the species in a given area. More specifically, biodiversity can be defined as the variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur. |
SciQ | SciQ-6419 | inorganic-chemistry, ions
Once you added a proton to the neutral ammonia molecule, you disturbed that original charge balance. There is a shortage of a single electron in the new molecule so formed and this denoted by the plus sign on the ammonium ion.
The following is multiple choice question (with options) to answer.
Deleting or inserting a nitrogen base causes what? | [
"a degenerative mutation",
"a photoinhibition mutation",
"a placentation mutation",
"a frameshift mutation"
] | D | Deleting or inserting a nitrogen base causes a frameshift mutation. All of the codons following the mutation are misread. This may be disastrous. To see why, consider this English-language analogy. Take the sentence “The big dog ate the red cat. ” If the second letter of “big” is deleted, then the sentence becomes: “The bgd oga tet her edc at. ” Deleting a single letter makes the rest of the sentence impossible to read. |
SciQ | SciQ-6420 | cell-signaling, chemical-communication
Title: How many molecules are generally required for cell signallng processes for given cases? I know its really a broad topic but I am interested in just few cases:
Quorum sensing
neurotransmitters for the communication of images/ general information
hormones/pheromones
I actually want to know that does a single or hundreds of molecules are needed to communicate information from one cell to another.
I searched but approx number of molecules, I can't find anywhere. A cell can interact with other cells in zillions of ways. You can send information from one cell to other cells via neurotransmitters, hormones, pheromones, electric signals, magnetic resonance ,leukotrines etc.
In general a single type of molecule is enough to send such information. Like you require only Acetylcholine(Ach) as neurotransmitter to transmit various nerve impulses.
But, even for a single type, you require thousands of molecules. Like 1 molecule of Ach can do almost nothing and would immediately be broken by Acetylcholinesterase. You require 1000s of such molecules.
You can modify the communicating information via different types of transmitters. You can use GABA or glycine to supress any information exchange or use dopamine to enhance it. But again you will need many molecules of GABA or Glycine.
For visual pathway, you can use no. of types of transmitters like glutamate, glycine, gaba, dopamine, acetylcholine, substance P etc.
Neurotransmitters for visual pathway.
Hormones are transmitters that are required in small quantities. But, again you require certain concentration. There is normal blood concentration of various hormones like 80 pg/ml for calcitonin.
Quorum sensing use transmitters like AHLs. Again a certain threshold value is required for them to act.
Again, to produce these transmitters you have to go through a rigorous process of transcription, translation and post-translational modifications.
So, for cell to communicate a rigorous process is used.
The following is multiple choice question (with options) to answer.
What are the chemical messengers used to communicate between cells? | [
"membranes",
"neurons",
"peptides",
"hormones"
] | D | Hormones, chemical messengers used to communicate between cells, are important in regulating digestion. |
SciQ | SciQ-6421 | physical-chemistry, nanoscience
Title: What Makes Diamonds Difficult to Produce? Having seen an answer over on Worldbuilding about very strong/dense wood that suggested artificially creating some enzymes that would manufacture diamond/graphene as the cellular binding materials in the tree, I said to myself, "Hold on, I know this won't work: creating diamonds requires high temperature and/or pressures...doesn't it?"
But I was unable to locate any information as to why this is the case: that is, what physical property of the bonds or arrangement of the carbon atoms dictates the intense pressures needed to cause the formation of the crystal lattice? Or is there really nothing standing in the way of a chemical process (i.e. an enzyme constructing it a few atoms at a time, albeit with large energy expenditures and slow timescales) that would do it other than "we don't know how to make that."
The covenant bond energy between two carbon atoms seems pretty high, I'll admit, at 348 kJ/mol, but it's less than some other bonds, say Carbon and Hydrogen at 419 kJ/mol (source). So it doesn't seem like that's the limiting factor. I do know that there is energy stored in the organization of the lattice itself, but I don't know how much that contributes; Wikipedia only helpfully notes that the energy is "greater in materials like diamond than sugar."
The following is multiple choice question (with options) to answer.
Graphite and diamond both are made from carbon. what makes diamonds so hard? | [
"strong metallic network",
"strong light network",
"strong atomic network",
"weak atomic network"
] | C | Sometimes two different minerals have the same chemical composition. But they are different minerals because they have different crystal structures. Diamonds are beautiful gemstones because they are very pretty and very hard. Graphite is the “lead” in pencils. It's not hard at all! Amazingly, both are made just of carbon. Compare the diamond with the pencil lead in Figure below . Why are they so different? The carbon atoms in graphite bond to form layers. The bonds between each layer are weak. The carbon sheets can just slip past each other. The carbon atoms in diamonds bond together in all three directions. This strong network makes diamonds very hard. |
SciQ | SciQ-6422 | 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.
The paranasal sinuses are hollow, air-filled spaces located within certain bones of the skull. all of the sinuses communicate with the nasal cavity (paranasal = “next to nasal cavity”) and are lined with this? | [
"fluid mucosa",
"nasal mucosa",
"respiration mucosa",
"oral mucosa"
] | B | Paranasal Sinuses The paranasal sinuses are hollow, air-filled spaces located within certain bones of the skull (Figure 7.18). All of the sinuses communicate with the nasal cavity (paranasal = “next to nasal cavity”) and are lined with nasal mucosa. They serve to reduce bone mass and thus lighten the skull, and they also add resonance to the voice. This second feature is most obvious when you have a cold or sinus congestion. These produce swelling of the mucosa and excess mucus production, which can obstruct the narrow passageways between the sinuses and the nasal cavity, causing your voice to sound different to yourself and others. This blockage can also allow the sinuses to fill with fluid, with the resulting pressure producing pain and discomfort. The paranasal sinuses are named for the skull bone that each occupies. The frontal sinus is located just above the eyebrows, within the frontal bone (see Figure 7.17). This irregular space may be divided at the midline into bilateral spaces, or these may be fused into a single sinus space. The frontal sinus is the most anterior of the paranasal sinuses. The largest sinus is the maxillary sinus. These are paired and located within the right and left maxillary bones, where they occupy the area just below the orbits. The maxillary sinuses are most commonly involved during sinus infections. Because their connection to the nasal cavity is located high on their medial wall, they are difficult to drain. The sphenoid sinus is a single, midline sinus. It is located within the body of the sphenoid bone, just anterior and inferior to the sella turcica, thus making it the most posterior of the paranasal sinuses. The lateral aspects of the ethmoid bone contain multiple small spaces separated by very thin bony walls. Each of these spaces is called an ethmoid air cell. These are located on both sides of the ethmoid bone, between the upper nasal cavity and medial orbit, just behind the superior nasal conchae. |
SciQ | SciQ-6423 | acid-base, ph
Title: Why can't the strength of superacids be measured in water? I learned about acid strength, that the strength of an acid increases with it's degree of ionization when solvated. So, in water, a strong acid is one where $\ce{[H_3O^+]}$ is large, which is equal to a low pH: $\mathrm{pH=-log[H_3O^+]}$.
Considering extreme cases, such as superacids, I have found out that other methods are used to measure their acidity (methods I don't really understand). My question is why is it impossible to simply get super high concentrations of $\ce{[H_3O^+]}$ in aqueous solutions of superacids, and use this to determine the acid strength. Also, is pH used as a measure of acidity outside of aqueous solutions?
I have come over the leveling effect, but I don't think I fully understand it. The way I understand it (for the case with water as solvent) is that basically any acid in water will protolyze $\ce{H2O}$ to $\ce{H3O+}$, making this the effective acid. I don't understand why this would affect the measured pH, as it is $\ce{[H_3O^+]}$ you are measuring. Any acid-base reaction is always an equilibrium:
$$\ce{HA^1 + (A^2)- <=> (A^1)- + HA2}\tag{1}$$
and for each pair of acids $\ce{HA^1}$ and $\ce{HA^2}$ you could calculate a $K_\mathrm{a}$ value to determine one acid’s strength with respect to the other. This $K_\mathrm{a}$ value is typically calculated according to equation $(2)$ if $\ce{(A^2)-}$ (which does not have to feature a negative charge; I just wanted to avoid different descriptions for the two acids) is the solvent.
The following is multiple choice question (with options) to answer.
What determines the strength of a base when dissolved in water? | [
"amount of phosphorus ions produced",
"saline content",
"pH level",
"amount of hydroxide ions produced"
] | D | The strength of a base depends on how many hydroxide ions it produces when it dissolves in water. A stronger base produces more hydroxide ions than a weaker base. For example, sodium hydroxide (NaOH), a base in drain cleaner, is a strong base because all of it breaks down into ions when it dissolves in water. Calcium carbonate (CaCO 3 ), a base in antacids, is a weak base because only a small percentage of it breaks down into ions in water. |
SciQ | SciQ-6424 | nuclear-physics, radiation
Title: Is a naturally radioactive elements on its ground state? Ground state is defined as the zero energy state. No energy can be taken from it. Still, radioactive elements can emit radiation. Do we consider them to be in a ground state? A radioactive nucleus is not in its ground state of course. The state may be unstable, or metastable (which implies a slow decay). Of natural elements, only iron-56 nuclei and smaller have lower energy than their fission
products. This means that a LOT of nuclei are metastable (though the half-life might be VERY long) with respect to some kind of fission.
Light nuclei can go to lower energy by fusion, but that requires a second particle to combine with, so it's hard to call them 'unstable'.
Very heavy nuclei, including such items as neutron stars, are theoretically possible,
but I don't know much about their stability.
The following is multiple choice question (with options) to answer.
What is the low level of radiation that occurs naturally in the environment called? | [
"temperature radiation",
"consequence radiation",
"neon radiation",
"background radiation"
] | D | A low level of radiation occurs naturally in the environment. This is called background radiation. It comes from various sources. One source is rocks, which may contain small amounts of radioactive elements such as uranium. Another source is cosmic rays. These are charged particles that arrive on Earth from outer space. Background radiation is generally considered to be safe for living things. |
SciQ | SciQ-6425 | human-biology, cell-biology, immunology, virus
Title: What is the name of the property of viruses can activate a second time, with different symptoms? The Varicella zoster virus causes chickenpox in children and shingles in adults.
It appears after the initial infection, it can go dormant in the nerve, and reactivate itself decades later.
In chickenpox - the symptoms are:
characteristic skin rash that forms small, itchy blisters, which eventually scab over. It usually starts on the chest, back, and face then spreads to the rest of the body
In shingles - the symptoms are:
a painful skin rash with blisters involving a limited area. Typically the rash occurs on either the left or right of the body or face in a single stripe.
My question is: What is the name of the property of viruses can activate a second time, with different symptoms? Viral latency is the best term to use for viruses that can lie dormant.
I have not come across a specific term for latent viruses that recur with different symptoms. This is probably because "different" is very subjective. Many pathogens can cause several different forms of disease depending on factors such as the route of exposure (i.e. where and how the pathogen got to its destination). Obviously the latent infection has a different pathophysiology to chickenpox. Due to its latency in dorsal root ganglia, shingles typically results in a localised rash, but there are less common disseminated forms of shingles that can look very similar to chickenpox.
The following is multiple choice question (with options) to answer.
Varicella zoster virus causes what two illnesses? | [
"chicken pox and shingles",
"flu and shingles",
"german measles and flu",
"syphilis and lyme"
] | A | An enveloped virus. Varicella zoster virus causes chicken pox and shingles. |
SciQ | SciQ-6426 | evolution, mammals
Title: Why haven't land animals evolved beyond urination? It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is it about the chemistry of urine and the waste products eliminated that make urination necessary as opposed to eliminating them through defecation and recovering the water on the way out? It is probably true that toilets and other resting-ish area are always a great place to think about biology, I agree $\ddot \smile$.
Why do we urinate?
In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood.
Trade-off: energy cost vs. water loss
You're correct that the loss of water through urination is a considerable cost for an organism (especially those living in dry environments). But the amount of water used to excrete nitrogenous wastes is negatively correlated with the energy it costs to perform this excretion. In other words, there is a trade-off between water and energy loss during nitrogen excretion. Also, the question of toxicity is important.
Three ways to excrete nitrogenous wastes
Animals basically have three choices to excrete nitrogenous wastes:
Uric acid (excreted by uricotelic organisms)
Solid (crystal) with low water solubility
Low toxicity
Little water is needed
Lots of energy is needed
Ammonia (excreted by aminotelic organisms)
Highly soluble in water
High toxicity
Lots of water is needed to dilute it because of the toxicity
Not much energy is needed
Urea (excreted by ureotelic organisms)
Solid but highly soluble in water
"medium" amount of water is needed
"medium" toxicity
"medium" amount of energy is needed
The following is multiple choice question (with options) to answer.
The urethra transports urine from what organ to the outside of the body for disposal? | [
"brain",
"lungs",
"bladder",
"heart"
] | C | Urethra The urethra transports urine from the bladder to the outside of the body for disposal. The urethra is the only urologic organ that shows any significant anatomic difference between males and females; all other urine transport structures are identical (Figure 25.3). |
SciQ | SciQ-6427 | geology, volcanology, mineralogy, minerals
Title: Where can obsidian be found? Where is obsidian found?
Is it typically found on the surface or underground?
If underground, how far under (meters or feet would be perfect)?
Also, is it found everywhere on Earth, or just in areas where volcanic activity is (or was recently) high? Obsidian is formed when a rhyolitic (or felsic) lava flows cool rapidly. This must mean that it's mostly available on the surface (and I think if you go near volcanos you can find pieces of Obsidian on the ground) because molten rock cools much faster above ground than it does below, allowing the melt to cool with small crystals (as opposed to intrusive rocks which have larger crystals). This means that Obsidian is an extrusive igneous rock.
I am betting that Obsidian is very common around most active volcanos around the world!
The following is multiple choice question (with options) to answer.
Magnetite crystals in lava typically point to what geographic location? | [
"the equator",
"magnetic north pole",
"magnetic south pole",
"geographic north pole"
] | B | Magnetite crystals in the lava point in the direction of the magnetic north pole. The different stripes of magnetic polarity reveal the different ages of the seafloor. |
SciQ | SciQ-6428 | physical-chemistry, everyday-chemistry, thermodynamics
As a comparison to this example, let's check out two liquids that do mix.
3. Water and ethanol
For the water, we have basically the same situation as before -- water molecules forming good bonds to each other. The ethanol, though, has an -OH group that can form bonds to the water in the same way that the water does (though not as well). This means that ethanol that mixes with water (and vice versa) will tend to stay mixed, and given that the liquids are being mixed around just by random motions, means that you'll get one mixing with the other just as a matter of statistics.
The following is multiple choice question (with options) to answer.
Liquids that mix with water in all proportions are usually polar substances or substances that form these? | [
"silicon bonds",
"hydrogen bonds",
"compressed bonds",
"atmospheric bonds"
] | B | Liquids that mix with water in all proportions are usually polar substances or substances that form hydrogen bonds. For such liquids, the dipole-dipole attractions (or hydrogen bonding) of the solute molecules with the solvent molecules are at least as strong as those between molecules in the pure solute or in the pure solvent. Hence, the two kinds of molecules mix easily. Likewise, nonpolar liquids are miscible with each other because there is no appreciable difference in the strengths of solute-solute, solvent-solvent, and solute-solvent intermolecular attractions. The solubility of polar molecules in polar solvents and of nonpolar molecules in nonpolar solvents is, again, an illustration of the chemical axiom “like dissolves like. ” Two liquids that do not mix to an appreciable extent are called immiscible. Layers are formed when we pour immiscible liquids into the same container. Gasoline, oil (Figure 11.15), benzene, carbon tetrachloride, some paints, and many other nonpolar liquids are immiscible with water. The attraction between the molecules of such nonpolar liquids and polar water molecules is ineffectively weak. The only strong attractions in such a mixture are between the water molecules, so they effectively squeeze out the molecules of the nonpolar liquid. The distinction between immiscibility and miscibility is really one of degrees, so that miscible liquids are of infinite mutual solubility, while liquids said to be immiscible are of very low (though not zero) mutual solubility. |
SciQ | SciQ-6429 | quantum-field-theory, field-theory, quantum-chromodynamics, lattice-model, lattice-gauge-theory
Title: Lattice spacing in lattice QCD It is known that the lattice spacing in lattice QCD is not an external parameter and needs to be calculated, also the lattice beta parameter scales the lattice spacing ($a$) and goes as a function of the coupling constant as $$β=\frac{2*N}{g_0^2}$$
Where $N$ is a number of colors.
So the question is, how exactly is the lattice spacing calculated in lattice QCD?
I would also like to know how this lattice spacing is translated into physical units (GeV,fm). The lattice spacing can be obtained in a procedure usually referred to as scale setting for which one requires a physical quantity computed on the lattice. Take as an example the mass of the proton $am_P$ computed at a given value of the bare gauge coupling $g_0^2$ from the corresponding two-point correlation function. Given knowledge of the experimental value of the proton mass $m_P^{phys}$, the value of the lattice spacing can now be obtained via
$$a(g_0^2)=\frac{am_P(g_0^2)}{m_P^{phys}}\,.$$
A result in fm can then be directly derived using $\hbar c=197.3269788(12)$ MeV fm.
This scale setting is of course only valid up to lattice artifacts and depends on the quantity used to set the scale.
In practice people usually do not use the proton mass but rather the $\Omega$ or $\Xi$ masses or the decay constants of the pion and/or kaon. Intermediate scales like $r_0$ or $t_0$ which do not have a direct physical counterpart but can be easily and precisely computed on the lattice are also very common.
The following is multiple choice question (with options) to answer.
Lattice energy cannot be measured directly. what is its calculation based on? | [
"chemical reactions",
"measured energy changes",
"change in temperature",
"microscopic inspection"
] | B | There are a number of different ways to measure the strength of a given crystal lattice. One way would be to measure the amount of energy needed to completely pull apart an ionic substance into isolated ions. This value, known as the lattice energy , cannot be measured directly, but it can be calculated based on measured energy changes for other more feasible processes. The lattice energy of an ionic solid provides us with one way to measure the relative strength of the ionic bonds in that compound. Table below shows the lattice energies for various ionic substances:. |
SciQ | SciQ-6430 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
What process provides over 99% of the energy supply for life on earth? | [
"photosynthesis",
"nutrients",
"Carbon",
"gases"
] | A | Photosynthesis provides over 99% of the energy supply for life on Earth. A much smaller group of autotrophs - mostly bacteria in dark or low-oxygen environments - produce food using the chemical energy stored in inorganic molecules such as hydrogen sulfide, ammonia, or methane. While photosynthesis transforms light energy to chemical energy, this alternate method of making food transfers chemical energy from inorganic to organic molecules. It is therefore called chemosynthesis , and is characteristic of the tubeworms shown in Figure below . Some of the most recently discovered chemosynthetic bacteria inhabit deep ocean hot water vents or “black smokers. ” There, they use the energy in gases from the Earth’s interior to produce food for a variety of unique heterotrophs: giant tube worms, blind shrimp, giant white crabs, and armored snails. Some scientists think that chemosynthesis may support life below the surface of Mars, Jupiter's moon, Europa, and other planets as well. Ecosystems based on chemosynthesis may seem rare and exotic, but they too illustrate the absolute dependence of heterotrophs on autotrophs for food. |
SciQ | SciQ-6431 | palaeontology, herpetology
Title: How big can cold-blooded animals get? It seems impossible to have reptiles the size of dinosaurs, just because they are really big! Did they have different systems of maintaining body temperature or maybe they weren't the exact type of animals that we today call reptiles? Answer is quite simple as from @Alan Boyd link. They are cold blooded and thus, can go out for hunt in cold, they need to stay put till they get some prey.
So, it mainly depend on the temperature of the outside, I found this interesting paper on relation of body sizes and latitude.
Body sizes of poikilotherm vertebrates at different latitudes
Maximum sizes of 12,503 species of poikilotherm vertebrates were
analyzed for latitudinal trends, using published data from 75 faunal
studies. A general trend appears which may be summarized by the rule
"among fish and amphibian faunas the proportion of species with large
adult size tends to increase from the equator towards the poles". The
rule holds for freshwater fish, deepsea fish, anurans, urodeles, and
marine neritic fish arranged roughly in order of decreasing clarity of
the trend). In general the rule applies not only within these groups
of families but also within single families. In reptile groups, the
rule holds weakly among snakes and not at all among lizards or
non-marine turtles. Possible explanations include an association
between small size and greater specialization in the tropics; the
possibility in poikilo-therms of heat conservation or of some other
physiological process related to surface/volume ratio; selection for
larger size in regions subject to winter food shortages; and an
association between large adult size and high reproductive potential
in cold regions. Other suggestions can be advanced, but all are
conjectural and few are subject to test. Global size - latitude trends
should be looked for in other living groups.
Cite: Lindsey, C. C., 1966: Body sizes of poikilotherm vertebrates at
different latitudes. Evolution: 456-465
Now lets compare some of the largest cold blooded Animals:
Reptiles
Amphibians
Fishes (Pisces)
The following is multiple choice question (with options) to answer.
What type of animal are most reptiles in regards to diet? | [
"carnivores",
"omnivores",
"arthropods",
"herbivores"
] | A | Most reptiles are carnivores, and large reptiles are the top predators in their ecosystems. |
SciQ | SciQ-6432 | transition-metals, oxidation-state
The "free electrons" in the reference apparently refer to the possibility that stoichiometric Group V carbides may contain metal(V) and free electrons (e.g. $\ce{Nb^{V}C^{-IV}e^-}$) or a Group 4 carbide might be carbon deficient and thus not have all valence electrons bound to carbon (e.g. $\ce{Ti^{IV}C_{1-x}^{-IV}(e^-)_{4x}}$). The overall story is that at least for methanides, the distinction between "ionic/saline" and "metallic/interstitial" carbides is actually not sharp.
Reference
A. I. Avgustinik; G. V. Drozdetskaya; S. S. Ordan'yan (1967). "Reaction of titanium carbide with water". Powder Metallurgy and Metal Ceramics. 6 (6): 470–473. doi:10.1007/BF00780135. S2CID 134209836
The following is multiple choice question (with options) to answer.
Because of their reactivity, we do not find most representative metals as free elements where? | [
"in water",
"in nature",
"in the atomospher",
"underground"
] | B | [PCl 3][Cl 2] (0.135)(0.135) = = 0.021 0.87 [PCl 5] The equilibrium constant calculated from the equilibrium concentrations is equal to the value of Kc given in the problem (when rounded to the proper number of significant figures). Thus, the calculated equilibrium concentrations check. Kc =. |
SciQ | SciQ-6433 | 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.
Two important concepts, niche and habitat, are associated with what? | [
"water",
"ecosystem",
"natural selection",
"plant"
] | B | Two important concepts associated with the ecosystem are niche and habitat. |
SciQ | SciQ-6434 | medicine
Kiekeboe 21: the Piri-Piri Pills, Page 17, strip 30. Author: Merho. Publisher: J.Hoste NV (currently part of Standaard Uitgeverij). Picture taken by Nate Kerkhofs on 16 september 2014.
It is in Dutch, but the names of the illenesses are clearly readable (since they're Latin anyway).
The doctor asks "what are you here for, madame? a cold, reumathism, headache?" right before this. The woman answers "no, doctor, I'm struggling with ... and also ... not to mention ... and a really annoying .... The doctor then replies "but madame, where did you get all those illnesses?" the woman replies "in my medical encyclopaedia!". Erythema multiforme (minor) can and does occur in a lot of people; while it is usually self-limited, it can recur, especially when the trigger is an unsuspected food.[1] How common is it? It is very common.
Necrobiosis Lipoidica is not uncommon in diabetics, less common but still found in non-diabetics. It can occur at any age, including the eighth decade. It also shows a sex predilection, being 3 times more common in women than in men.[2] How common is it? It is not rare.
Phlegmasia Alba and Cerulea Dolens[3] is serious and associated with deep vein thrombosis, which is an acute event. It is not uncommon, but it's not chronic. (More than 600,000 cases of venous thromboembolism are estimated to occur each year in the United States, all of which can lead to Phlegmasia Alba and Cerulea Dolens. How common is it? Luckily, not very. If the author is referring to garden-variety thrombophlebitis, though, that's a chronic problem, and not uncommon in the elderly. Thrombophlebitis is chronic and common enough.
I'm not going to address Metropathia Haemorrhagica, because, as you have noted, it's found in menstruating women.
The following is multiple choice question (with options) to answer.
When does diseases like alzheimer's become more common? | [
"i-40 age",
"old age",
"teenager",
"toddler"
] | B | Old age begins in the mid-60s and lasts until the end of life. Most people over 65 have retired from work, freeing up their time for hobbies, grandchildren, and other interests. Stamina, strength, reflex time, and the senses all decline during old age, and the number of brain cells decreases as well. The immune system becomes less efficient, increasing the risk of serious illnesses such as cancer and pneumonia. Diseases such as Alzheimer’s disease that cause loss of mental function also become more common. |
SciQ | SciQ-6435 | human-anatomy
[source]
And now, follow along with your own hand!
finger (4 DOF): each finger has 2 interphalangeal joints between the distal, middle and proximal phalanges that allow for flexion/extension (2 DOF); each finger also has a metacarpophalangeal joint between the proximal phalanx and the metacarpal that allows for flexion/extension as well as abduction/adduction (2 DOF)
thumb (5 DOF): an interphalangeal joint between the distal and proximal phalanges allowing flexion/extension (1 DOF); a metacarpophalangeal joint between the proximal phalanx and metacarpal allowing flexion/extension and abduction/adduction (2 DOF); a carpometacarpal joint between the metacarpal and trapezium allowing flexion/extension and abduction/adduction (2 DOF)
wrist (6 DOF): between the carpals and radius allowing flexion/extension, abduction/adduction and supination/pronation (3 DOF); I think when the authors refer to translation of the wrist, they are simply saying that hand can be moved in all planes of 3D space (ie up/down, side to side, forward/backward - 3 DOF)
Since we have 4 fingers, they give 16 DOF. Adding the 5 DOF of the thumb and 6 of the wrist, we get 27. Please nobody question my reasoning. Thank you.
The following is multiple choice question (with options) to answer.
What is a fibrocartilaginous pad that fills the gap between adjacent vertebral bodies? | [
"Back Disk",
"intervertebral disc",
"unidirectional disc",
"subsidence disc"
] | B | Intervertebral Disc An intervertebral disc is a fibrocartilaginous pad that fills the gap between adjacent vertebral bodies (see Figure 7.24). Each disc is anchored to the bodies of its adjacent vertebrae, thus strongly uniting these. The discs also provide padding between vertebrae during weight bearing. Because of this, intervertebral discs are thin in the cervical region and thickest in the lumbar region, which carries the most body weight. In total, the intervertebral discs account for approximately 25 percent of your body height between the top of the pelvis and the base of the skull. Intervertebral discs are also flexible and can change shape to allow for movements of the vertebral column. Each intervertebral disc consists of two parts. The anulus fibrosus is the tough, fibrous outer layer of the disc. It forms a circle (anulus = “ring” or “circle”) and is firmly anchored to the outer margins of the adjacent vertebral bodies. Inside is the nucleus pulposus, consisting of a softer, more gel-like material. It has a high water content that serves to resist compression and thus is important for weight bearing. With increasing age, the water content of the nucleus pulposus gradually declines. This causes the disc to become thinner, decreasing total body height somewhat, and reduces the flexibility and range of motion of the disc, making bending more difficult. The gel-like nature of the nucleus pulposus also allows the intervertebral disc to change shape as one vertebra rocks side to side or forward and back in relation to its neighbors during movements of the vertebral column. Thus, bending forward causes compression of the anterior portion of the disc but expansion of the posterior disc. If the posterior anulus fibrosus is weakened due to injury or increasing age, the pressure exerted on the disc when bending forward and lifting a heavy object can cause the nucleus pulposus to protrude posteriorly through the anulus fibrosus, resulting in a herniated disc (“ruptured” or “slipped” disc) (Figure 7.30). The posterior bulging of the nucleus pulposus can cause compression of a spinal nerve at the point where it exits through the intervertebral foramen, with resulting pain and/or muscle weakness in those body regions supplied by that nerve. The most common sites for disc herniation are the L4/L5 or L5/S1 intervertebral discs, which can cause sciatica, a widespread pain that radiates from the lower back down the thigh and into the leg. Similar injuries of the C5/C6 or C6/C7 intervertebral discs, following forcible hyperflexion of the neck from a collision accident or football injury, can produce pain in the neck, shoulder, and upper limb. |
SciQ | SciQ-6436 | organic-reduction
Title: Hydrogenation of pent-4-en-2-one If one equivalent of $\ce{H2}/\ce{Pt}$ is made to react with one equivalent of pent-4-en-2-one, what will be the product formed? You have not specified the full reaction conditions - temperature and pressure can make a considerable difference - however this quote from Chemistry Libre Texts here (in turn quoting Basic Principles of Organic Chemistry by Roberts & Caserio) gives us a clear indication of the relative ease of hydrogenation of ketones vs double bonds.
Hydrogenation of aldehyde and ketone carbonyl groups is much slower than of carbon-carbon double bonds so more strenuous conditions are required. This is not surprising, because hydrogenation of carbonyl groups is calculated to be less exothermic than that of carbon-carbon double bonds....It follows that it is generally difficult to reduce a carbonyl group in the presence of a carbon-carbon double bond by hydrogenation without also saturating the double bond. Other reducing agents are more selective:
The following is multiple choice question (with options) to answer.
What organic catalysts work by lowering the activation energy needed to start biochemical reactions? | [
"carbohydrates",
"hormones",
"glucose",
"enzymes"
] | D | Enzymes work by lowering the activation energy needed to start biochemical reactions. |
SciQ | SciQ-6437 | human-biology, red-blood-cell
Title: How do people who have lost both of their legs produce red blood cells? As far as I know, just leg bones produce red blood cells. So, how people who lost their both legs produce red blood cells? Red blood cells are produced in the red marrow which...
"is found mainly in the flat bones, such as the pelvis, sternum,
cranium, ribs, vertebrae and scapulae, and in the cancellous
("spongy") material at the epiphyseal ends of long bones such as the
femur and humerus." - Wikipedia
So you are partly right; the femur is associated with red blood cell production, or Erythropoiesis to give it it's technical name, but there are other bones within the human body that also do this job. The process of erythropoiesis is stimulated when the kidneys detect low levels of oxygen in the blood stream and stimulate production of the hormone erythropoietin. Further, the role of the tibia and femur in erythropoiesis also decreases with age whereas...
"the vertebrae, sternum, pelvis and ribs, and cranial bones continue
to produce red blood cells throughout life." - again from the wiki page
So I'd suggest it is unlikely that loss of the legs would have a major impact on the production of red blood cells in adults. I imagine that with the loss of legs comes some reduction in functionality of erythropoiesis but also a lower requirement of red blood cell production (less blood capacity = less blood cells needed = less blood cells need to be produced). I can't find any studies which explore the ability or needs of amputees and non-amputees with regards to red blood cell production.
The following is multiple choice question (with options) to answer.
What structure supports the body, protects internal organs, produces blood cells, and maintains mineral homeostasis? | [
"fossil",
"skin",
"skeleton",
"cuticle"
] | C | The skeleton supports the body, protects internal organs, produces blood cells, and maintains mineral homeostasis. |
SciQ | SciQ-6438 | nitrogen
Step three is when plants and the animals that live of the plants die and breaks down into ammonia and other waste products (this is where many explanations of the nitrogen cycle usually starts). The waste products gets converted into ammonia by bacteria and the ammonia gets converted to nitrite and the entire cycle starts all over again.
Legumes have a symbiotic relationship with some bacteria that can fixate nitrogen (N2) https://aces.nmsu.edu/pubs/_a/A129/
sources:
https://science.howstuffworks.com/life/biology-fields/nitrogen-cycle.htm
https://www.britannica.com/science/denitrifying-bacteria
The rest is from my memory.
The following is multiple choice question (with options) to answer.
When vertebrate animals metabolize ammonia what is the primary byproduct that is produced? | [
"urea",
"carbon monoxide",
"dioxide",
"proteins"
] | A | 41.4 Nitrogenous Wastes Ammonia is the waste produced by metabolism of nitrogen-containing compounds like proteins and nucleic acids. While aquatic animals can easily excrete ammonia into their watery surroundings, terrestrial animals have evolved special mechanisms to eliminate the toxic ammonia from their systems. Urea is the major byproduct of ammonia metabolism in vertebrate animals. Uric acid is the major byproduct of ammonia metabolism in birds, terrestrial arthropods, and reptiles. |
SciQ | SciQ-6439 | acid-base, analytical-chemistry, experimental-chemistry, extraction
Title: Separation of Binary mixture? I will be given a binary mixture containing two unknown compounds(the mixture could be either liquid or solid- I don't know yet). The plan of the experiment is to identify the two compounds. So my primary concern is to separate the binary mixture and purify the individual compounds(then the subsequent classification tests/NMR/IR analysis should be straightforward). I am thinking of doing an acid-base extraction but don't know how to since I don't know any physical properties of the compounds. Any suggestions would be appreciated. N.B.: the advice below mostly applies to organic compounds. If you're dealing with inorganic salts, or solutions thereof, the approach will be very different.
For a solid mixture, I would take an IR first. That should allow you to rule out potentially useless chemical tests by identifying the functional groups present in your mixture without wasting any of the sample. This would also give you some indication whether acid/base extraction is likely to be of any use. After that, it seems logical to test solubility in a wide range of solvents and at different temperatures. If you can find one that dissolves your mixture only partially at low temperature, but completely at high temperature, then you can likely separate the components immediately by recrystallization. Judicious use of a centrifuge can help if the crystals form a fine suspension.
In the case of a liquid mixture, I would again take an IR initially. In some cases, one component of the mixture can be chemically separated, and IR results would again be useful in determining the viability of that approach. Ketones and aldehydes, for example, will react to form semicarbazones that can be recrystallized and then identified by melting point. As far as physical methods of separation, standard are distillation and fractional freezing.
The following is multiple choice question (with options) to answer.
Which process involves solvent separation on a solid medium? | [
"affinity",
"substration",
"resonance",
"chromatography"
] | D | Chromatography involves solvent separation on a solid medium. |
SciQ | SciQ-6440 | cell-biology, proteins, transcription, cell-signaling, intracellular-transport
Time is in minutes, and zeroed at first contact between the two cells. I've put a red dot on the T-cell and a blue one on the APC in the DIC images (left panes); hopefully that proves more informative than annoying. The right panes show GFP fluorescence and thus CD3 localization. As time progresses, CD3 is re-localized from one part of the membrane to another (the synapse). There is supposedly a video of this is in the supplementary information of the article, though I was unable to open it.
The rate and directionality of the movement implies that an active process is occurring, rather than simple diffusion. However, they did not find the actual mechanism for movement and I haven't found any follow-up papers in a brief search (though many subsequent papers implicate the cytoskeleton in this movement). Just to show that movement of transmembrane proteins can, in fact, be actively directed by the cytoskeleton, I refer you to this paper:
Grabham PW, Foley M, Umeojiako A, Goldberg DJ. 2000. Nerve growth factor stimulates coupling of beta1 integrin to distinct transport mechanisms in the filopodia of growth cones. J Cell Sci 113:3003-3012.
They show that membrane-spanning integrins are moved along actin filaments of the cytoskeleton by myosin motor proteins. Expectedly, the abstract does a good job of summarizing the paper:
The cycling of membrane receptors for substrate-bound proteins via their interaction with the actin cytoskeleton at the leading edge of growth cones and other motile cells is important for neurite outgrowth and cell migration. Receptor delivered to the leading edge binds to its ligand, which induces coupling of the receptor to a rearward flowing network of actin filaments. This coupling is thought to facilitate advance... [T]ransport was dependent on an intact actin cytoskeleton and myosin ATPase...
The following is multiple choice question (with options) to answer.
Plasmodesmata and gap junctions are channels between adjacent cells of what respective types? | [
"plant and animal",
"healthy and sick",
"new and old",
"plant and fungus"
] | A | 4.6 Connections between Cells and Cellular Activities Animal cells communicate via their extracellular matrices and are connected to each other via tight junctions, desmosomes, and gap junctions. Plant cells are connected and communicate with each other via plasmodesmata. When protein receptors on the surface of the plasma membrane of an animal cell bind to a substance in the extracellular matrix, a chain of reactions begins that changes activities taking place within the cell. Plasmodesmata are channels between adjacent plant cells, while gap junctions are channels between adjacent animal cells. However, their structures are quite different. A tight junction is a watertight seal between two adjacent cells, while a desmosome acts like a spot weld. |
SciQ | SciQ-6441 | energy, fuel, environmental-chemistry
Title: Effect of coal and natural gas burning on particulate matter pollution I sometimes hear people talking about how we should replace coal burning plants with natural gas ones, to alleviate the case of particulate matter pollution. What exactly is the difference between coal fuel and natural gas that makes the latter seem "cleaner"?
At the same energy outcome, natural gas produces less carbon dioxide than coal. In a way, natural gas is half way between coal and hydrogen.
Coal produces smelly smoke, solid particles, sulfur dioxide and minor or trace heavy metal pollutants.
It is less known to common people, but power plants burning coal are more significant source of radioactive pollution than nuclear plants. This pollution is very diluted, but rather significant in absolute amount. Coal ash, used in past as a filler for some construction materials, has lead in some cases to significantly increased content of radium-226 in building walls. This radium is a product of long term decay of natural uranium. It further decays while producing radioactive gaseous radon-222, which is dangerous in long term inhalation because of lung cancer. As it stays in lungs as polonium-218 and its decay products.
See e.g. Uranium produced from coal ash
... the uranium concentration in the ash pile is about 150-180 parts per million, about 1/4th of the concentration often thought of as commercially viable for ISL[In Situ Leaching] mining. However, coal ash piles have some physical characteristics that might help overcome that disadvantage since they may be easier to drill and it might be easier to protect the local groundwater from contamination. ...
See Radon in building materials by Czech government agency for radiation protection.
The following is multiple choice question (with options) to answer.
Natural gas burns cleaner and produces less carbon dioxide than fuels of what type? | [
"solar energy",
"renewable fuels",
"fossil fuels",
"biofuels"
] | C | Natural gas burns cleaner than other fossil fuels. As a result, it causes less air pollution. It also produces less carbon dioxide than the other fossil fuels. Because it burns cleaner than other fossil fuels, natural gas has a good reputation. Still, natural gas does emit pollutants. |
SciQ | SciQ-6442 | organic-chemistry, elements, carbon-allotropes
Title: What makes carbon special and versatile? My teacher told me that carbon's tetravalency and high catenation ability makes it special and is the reason why there are millions of compounds of carbon.
1) Silicon is tetravalent too but doesn't create as many compounds as carbon.Why?
2) The textbook says that no other element exhibits the property of catenation to the extent of carbon. Why is this so? Does it just happen magically? There are two key factors that account for the ubiquity of carbon compounds.
Bond strengths: Look at the following table of bond strengths and notice how the strength of both carbon-carbon single and double bonds is much greater than the bond strengths found in other molecules.
\begin{array}\hline
Typical~Single ~Bond~ Dissociation ~Energies~ (kcal/mole)\\ \hline
\end{array}
\begin{array}{|c|c|c|}\hline
C-C & 83 \\ \hline
N-N & 38 \\ \hline
O-O & 35 \\ \hline
Si-Si & 52 \\ \hline
P-P & 50 \\ \hline
S-S & 54 \\ \hline
\end{array}
\begin{array}\hline
Typical~Double ~Bond~ Dissociation ~Energies~ (kcal/mole)\\ \hline
\end{array}
\begin{array}{|c|c|c|}\hline
C=C & 146 \\ \hline
N=N & 109 \\ \hline
O=O & 119 \\ \hline
P=P & 84 \\ \hline
\end{array}
link to reference
These numbers tell us that carbon-carbon bonds are significantly more stable than other bonds and that the driving force for their formation will be more exothermic. Therefore, large collections of carbon atoms can be bonded together to produce very stable systems.
The following is multiple choice question (with options) to answer.
What are the simplest types of carbon-based compounds? | [
"hydrocarbons",
"particles",
"Microbes",
"Cells"
] | A | Hydrocarbons are compounds that contain only carbon and hydrogen. They are the simplest type of carbon-based compounds. |
SciQ | SciQ-6443 | human-physiology, digestion, stomach
The stomach accomplishes much of its function by mechanically breaking down the swallowed food particles and mixing them with acid and enzymes into a sort of slurry. To do this, there are three major layers of muscle surround the stomach - from the outside, the longitudinal layer, the circular layer, and the oblique layer. The stomach also has two holes in it - the gastroesophageal opening, coming from the esophagus with the swallowed food/saliva mix, and the pylorus, where the food/acid/enzyme slurry exits into the duodenum, which is the beginning of the small intestine.
Due to the three layers of (rather strong) muscle, the stomach doesn't have a lot of expansion capability once it is filled completely to capacity. Fortunately, this almost never occurs (despite how we may feel after a large meal) because material is always leaving the stomach on its way to enzymatic digestion in the intestines. Additionally, once the stomach is filled to a certain extent, hormones such as leptin are secreted that give you the feeling of being sated, or full, triggering the brain to make you stop eating.
Of course, as we can see with the current epidemic of obesity around the world, the stomach can change its size over time. However, this is a rather slow process (weeks to months to years) of adapting to continuously consuming large meals.
But what would happen if you completely ignored these internal warnings, or were being force-fed, or whatever? Instead of rupturing (the biological equivalent of "exploding"), food would most likely be expelled either into the small intestine or back into the esophagus and back up the way it came down, i.e. causing vomiting.
The following is multiple choice question (with options) to answer.
What process moves food through the esophagus no matter which position the body is in? | [
"mastication",
"homeostasis",
"proteolysis",
"peristalsis"
] | D | Some people think that gravity moves food through the esophagus. If that were true, food would move through the esophagus only when you are sitting or standing upright. In fact, because of peristalsis, food can move through the esophagus no matter what position you are in—even upside down! Just don’t try to swallow food when you are upside down—you could choke!. |
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