source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-6844 | quantum-mechanics, energy, momentum, mass, wavelength
Title: de Broglie wavelength for particles with mass is $p=\frac{h}{\lambda}$ only true for massless particles? because generally $E=\sqrt{p^2c^2+m^2c^4}$, then if we equate it to $h\nu$ we get $$p=\sqrt{\frac{h^2}{\lambda^2}-m^2c^2}\neq\frac{h}{\lambda}$$ Relativistic energy-momentum relation:
$$p_\mu p^\mu = (p^0)^2 - \vec p^2= m_0^2 c^2$$
where
$$p^0 c=E=\hbar \omega \qquad p^i = \hbar k^i$$
subject to $|k|=2\pi/\lambda$ and $\omega = 2\pi\nu$.
Therefore, generally
$$|p| = \sqrt{\frac{h^2 \nu^2}{c^2}-m_0^2 c^2}=\frac{h}{\lambda}$$
Only for a massless particle ($m_0=0$) the energy-momentum relation reduces to
$$|p|=\frac{h \nu}{c}=\frac{h}{\lambda}$$
or
$$\nu =\frac{c}{\lambda}$$
But this does not limit the validity of the more general energy-momentum relation above.
The following is multiple choice question (with options) to answer.
What were the first particles with mass to be directly confirmed to have the wavelength proposed by de broglie? | [
"negatrons",
"electrons",
"ions",
"protons"
] | B | Electrons were the first particles with mass to be directly confirmed to have the wavelength proposed by de Broglie. Subsequently, protons, helium nuclei, neutrons, and many others have been observed to exhibit interference when they interact with objects having sizes similar to their de Broglie wavelength. The de Broglie wavelength for massless particles was well established in the 1920s for photons, and it has since been observed that all massless particles have a de Broglie wavelength λ = h / p. The wave nature of all particles is a universal characteristic of nature. We shall see in following sections that implications of the de Broglie wavelength include the quantization of energy in atoms and molecules, and an alteration of our basic view of nature on the microscopic scale. The next section, for example, shows that there are limits to the precision with which we may make predictions, regardless of how hard we try. There are even limits to the precision with which we may measure an object’s location or energy. Making Connections: A Submicroscopic Diffraction Grating The wave nature of matter allows it to exhibit all the characteristics of other, more familiar, waves. Diffraction gratings, for example, produce diffraction patterns for light that depend on grating spacing and the wavelength of the light. This effect, as with most wave phenomena, is most pronounced when the wave interacts with objects having a size similar to its wavelength. For gratings, this is the spacing between multiple slits. ) When electrons interact with a system having a spacing similar to the electron wavelength, they show the same types of interference patterns as light does for diffraction gratings, as shown at top left in Figure 29.24. Atoms are spaced at regular intervals in a crystal as parallel planes, as shown in the bottom part of Figure 29.24. The spacings between these planes act like the openings in a diffraction grating. At certain incident angles, the paths of electrons scattering from successive planes differ by one wavelength and, thus, interfere constructively. At other angles, the path length differences are not an integral wavelength, and there is partial to total destructive interference. This type of scattering from a large crystal with well-defined lattice planes can produce dramatic interference patterns. It is called Bragg reflection, for the father-and-son team who first explored and analyzed it in some detail. The expanded view also shows the pathlength differences and indicates how these depend on incident angle θ in a manner similar to the diffraction patterns for x rays reflecting from a crystal. |
SciQ | SciQ-6845 | 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 is a simple machine that consists of a rope wrapped around a grooved wheel? | [
"Wheel and axle",
"Inclined plane",
"Lever",
"a pulley"
] | D | A pulley is a simple machine that consists of a rope wrapped around a grooved wheel. Pulleys are generally used to lift a load. |
SciQ | SciQ-6846 | cloning, biotechnology
Title: What happens between making a DNA library and screening by nucleic acid hybridization? I understand how a plasmid library is made and how each clone is put on the nitrocellulose membrane and nucleic acid hybridization is done. What I don't understand is how each clone is "identified" and separately put on the membrane? The library is 'created' during a ligation reaction: plasmid vector + insert (e.g. cDNA). That DNA is used to transform E. coli, and, after plating out the transformation mixture, single bacterial colonies are obtained. Each colony contains, to a first approximation, a single plasmid species (i.e with a single insert). So each colony represents a clone, in the terms that you use.
I don't know if anyone really does things like this any more, but originally each plate would be transferred to nitrocellulose, for probing, and to a fresh plate for archiving. This way, any colony identified as positive after nucleic acid hybridisation could be picked from the archive plate for further characterisation.
This screening can be done on large format Petri dishes to reduce the number of plates needed. I know of one lab which in the 1980s used to screen λ libraries after plating out for plaques on cafeteria trays. That was the heroic era of molecular biology.
The following is multiple choice question (with options) to answer.
What helps screen libraries for a gene of interest using nucleic acid hybridization? | [
"cellular acid probe",
"mitochondrial acid probe",
"nucleic acid probe",
"proteins acid probe"
] | C | |
SciQ | SciQ-6847 | botany, terminology, nomenclature
Regnum Animale: the animals;
Regnum Vegetabile: the plants;
Regnum Lapideum: the minerals (you read it right).
Note that, in this classification, "animals" correspond to what nowadays we call animals and protozoans, and "plants" correspond to what nowadays we call plants, algae, fungi and bacteria.
You have to keep in mind that this book was first published in 1735, well before the evolutionary biology being proposed in the XIX century and established in the XX century. Therefore, it is a book published when fixism was the current paradigm, full of mentions to the scala naturae.
So, the plants (as well as the animals) showed a continuum of species, going to the lower plants (the bacteria) to the higher plants (the flowering ones). It's worth mentioning again that, by that time, bacteria were plants: Phylum Schyzophyta, to be more precise.
Thus, we have "lower plants" and "higher plants", "lower animals" and "higher animals", as well as "lower minerals" and "higher minerals"!
Unfortunately, this terminology is so embedded in the biological sciences that even today, as I mentioned, we struggle to get rid of it.
Just drop "higher plants", whatever it means
As your Wikipedia link says, "higher plants" is a synonym of vascular plants. However, there are a lot of problems here:
First, this is a remnant of the scala naturae and, just because of that, should be avoided. Think of it as a meaningless term, just like "more evolved organism".
Second, there is no clear and indisputable definition of what is a "higher" plant. Some authors used to define the "higher plants" as the Angiosperms only, or the seed plants (Angiosperms + Gymnosperms), or the vascular plants (Angiosperms, Gymnosperms and Pteridophyta).
For instance, in lusophone biology books, it was very common a division in three groups:
lower plants: bacteria and algae;
intermediate plants: bryophytes and pteridophytes;
higher plants: gymnosperms and angiosperms.
The following is multiple choice question (with options) to answer.
What is one way of classifying organisms called? | [
"tuck",
"clade",
"cluster",
"spasm"
] | B | One way of classifying organisms that shows phylogeny is by using the clade. A clade is a group of organisms that includes an ancestor and all of its descendants. Clades are based on cladistics. This is a method of comparing traits in related species to determine ancestor-descendant relationships. Clades are represented by cladograms, like the one in Figure below . This cladogram represents the mammal and reptile clades. The reptile clade includes birds. It shows that birds evolved from reptiles. Linnaeus classified mammals, reptiles, and birds in separate classes. This masks their evolutionary relationships. |
SciQ | SciQ-6848 | immunology, reproduction, development
Title: How do Sertoli cells protect sperms? I was reading Developmental biology by Gilbert and stumbled upon a fact that Sertoli cells provide protection to the developing sperms with no futher explanation.
I googled it and found a few books mentioning that it protects sperms from cell mediated immunity and antisperm antibodies. Yet I found a website called fertilitypedia that said:
Sertoli cells do not only control the process of spermatogenesis, but they are also responsible for creating so called immunologically privileged area in the testicles. It means, that Sertoli cell manage to keep blood separated from seminiferous tubules through the connection between them, called tight junction. Tight junction keeps bloodborne substances from reaching germ cells, so all stages of germ cells are protected from the body immunity. Tight junction also keeps surface antigens found on developing germ cells from eluding into the bloodstream so no autoimmune reaction could happen. Since Sertoli cells form the block between the blood and lumen of seminiferous epithelium, they are also in control of the entry and exit of nutrients, hormones and other chemicals into the tubules of the testis.
I'm unable to verify this explanation from the cited sources as none contain the mentioned information.
So my question, how does it actually protect the sperms? The Wikipedia pages on Blood-testis barrier and Sertoli cells have some information relevant to your question, with some academic references included.
You could also search for reviews on Sertoli cells on Google Scholar - several of the first returned results seem relevant, if you are able to access them.
The following is multiple choice question (with options) to answer.
The earliest stages of spermatogenesis occur closest to the lumen of the what? | [
"interstitial tubules",
"epithelium tubules",
"seminiferous tubules",
"viviparous tubules"
] | C | |
SciQ | SciQ-6849 | electromagnetic-radiation
That being said, all objects emit radiation at lower frequencies, including at the $1Hz$ range. However, when we observe these objects, we tend to look for frequencies that will have enough energy to be easily visible and using well known technology. Currently, we use Radio waves as the lowest range (Yes, I see the tautology there), specifically the mid to high-end radio waves. The reason being manifold; as wavelength goes up, your antenna dish needs to be on the same scale as it or larger. This means for even poor resolution, a $1Hz$ telescope would need to span almost to the Moon (as I mentioned earlier). Also, $1Hz$ is very far from the peak emitted frequency of any object, which means that the power at that frequency would be extremely low. In most cases, it is so low that one could approximate the amount of radiation at $1Hz$ as zero.
In summary, $1Hz$ is a very natural frequency, in fact cosmologists often talk about frequencies much lower; with wavelength on the order of the size of the visible universe. The technology does exists to be able to measure such a wave, but it is (in almost all cases) impractical to do so and thus, there is no standard equipment existing that can do it. All objects emit $1Hz$ radiation, however this is nowhere near the peak frequency of any natural body, so detecting it from a natural object would be pointless and require massive amounts of power.
The following is multiple choice question (with options) to answer.
Which of the electromagnetic waves have the shortest wavelengths and highest frequencies? | [
"gamma",
"beta",
"ultraviolet",
"plasma"
] | A | Of all electromagnetic waves, gamma rays have the shortest wavelengths and highest frequencies. Because of their very high frequencies, gamma rays have more energy than any other electromagnetic waves. |
SciQ | SciQ-6850 | redox, organic-oxidation
Title: Oxidation of Sodium Hydroxide in Ethanol? So I read recently that:
Alcoholic solutions of sodium hydroxide will oxidize in air, turning brown.
First is this true?
And if so what is oxidizing?
I can't think of what sodium hydroxide would oxidize to, and ethanol well wouldn't that oxidize to water and CO2! [Answer based on comments from @KemonoChen, @IvanNeretin and @NilayGhosh. Thanks for your input :D]
In the presence of alkali (or acid, for that matter) aldehyde will
turn against itself, creating all matters of ugly polycondensate
products. See Aldol
condensation and
note that it ends up in another aldehyde, so the process can and will
be repeated
So yes it can happen.
And is is most likely ethanol oxidation to an aldehyde, which has (aldol) condensed into an 'ugly polycondensate'
It may also be Sodium Alkoxide, which is known to turn brown.
The following is multiple choice question (with options) to answer.
The oxidation of an alcohol can produce either an aldehyde or what? | [
"ketone",
"enzyme",
"amine",
"ester"
] | A | The oxidation of an alcohol can produce either an aldehyde or a ketone. Ethanol can be oxidized in the laboratory through a heating process combined with the addition of an oxidizing agent such as the dichromate ion, which catalyzes the reaction in an acidic solution. The reaction produces the aldehyde ethanal (acetaldehyde). |
SciQ | SciQ-6851 | special-relativity, reference-frames, mass, inertial-frames, mass-energy
Our task is to find a conserved quantity analogous to classical momentum. We suppose that the momentum of a particle moving with velocity $\mathbf{w}$ is $$\mathbf{p} = m(w) \mathbf{w}$$ where $m(w)$ is a scalar quantity yet to be determined, analogous to Newtonian mass but which could depend on the speed $w$.
The x momentum in A’s frame is due entirely to particle B. Before the collision B’s speed is
$w = \sqrt{V^2 + u_0^2/\gamma^2}$ and after the collision it is $w' = \sqrt{V^2 + u'^2/\gamma^2}$. Imposing conservation of momentum in the x direction yields $$m(w)V = m(w')V$$ It follows that $w=w'$, so that $$u' = u_0$$ In other words, y motion is reversed in the A frame.
Next we write the statement of the conservation of momentum in the y direction as evaluated in A’s frame. Equating the y momentum before and after the collision gives
$$-m_0 u_0 + m(w) \frac{u_0}{\gamma} = m_0 u_0 - m(w) \frac{u_0}{\gamma}$$
which gives $$m(w) = \gamma m_0$$ In the limit $u_0 \rightarrow 0$, $m(u_0) \rightarrow m(0)$, which we take to be the Newtonian mass, or "rest mass" $m_0$, of the particle. In this limit, $w = V$. Hence $$m(V) = \gamma m_0 = \frac{m_0}{\sqrt{1 - V^2/c^2}}$$
Consequently, momentum is preserved in the collision provided we define the momentum of a particle moving with velocity $\mathbf{v}$ to be $$\mathbf{p} = m \mathbf{v}$$ where
The following is multiple choice question (with options) to answer.
Change in momentum in an object is equivalent to what other measurement? | [
"resistance",
"velocity",
"impulse",
"gravity"
] | C | The change of momentum of an object is equal to the impulse. |
SciQ | SciQ-6852 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
Where does most water evaporate from? | [
"oceans",
"rivers",
"seas",
"lakes"
] | A | Evaporation changes liquid water to water vapor. Energy from the Sun causes water to evaporate. Most evaporation is from the oceans because they cover so much area. The water vapor rises into the atmosphere. |
SciQ | SciQ-6853 | spectroscopy, electrons, ionization-energy, electromagnetic-radiation
In order to excite a valence electron, the longest wavelength or lowest energy radiation is usually in the visible region, not longer than ~700 nm. I'm not sure if there is a lower limit to this energy, or what the observed lowest energy electronic transition is, but certainly in this region, there is some overlap with the energy required to excite molecular vibrations. For some nice cases you can perform vibrational-electronic spectroscopy (usually called "vibronic" spectroscopy), where you resolve a number of vibrational transitions (peaks) as fine splitting or fine structure for a single electronic transition:
$\hspace{20ex}$
However, we do not say that "infrared radiation can excite electrons", though there is a range of frequencies where the types of excitation couple together. See also rotational-vibrational (rovibrational) spectroscopy; a nice example is hydrogen chloride in the gas phase.
The reason coordination complexes are often colored is because there are valence electronic excitations that correspond to the absorption of electromagnetic radiation in the visible region. The reason many molecules or complexes are white is because their lowest energy electronic transition is in the ultraviolet region. This is more general than losing degeneracy, and holds true for any macroscopic or microscopic system. It is not different from the color we see for conjugated systems. If the lowest energy available transition of a system is in the visible region, the system will appear colored. If it absorbs red-orange light, the opposite side of a color wheel will show you that it should appear green-blue. What you see as the system's color is the remaining color after subtracting the absorbed color. Yes, the kinds of orbitals involved are different (d-d transitions or metal-to-ligand charge transfer versus $\pi\rightarrow\pi^{*}$), but the transition energy matching is the most important thing.
For the "limit of ionizing radiation", ionization refers not to the excitation of an electron, but its removal:
$$
\ce{X + energy -> X+ + e-}
$$
The following is multiple choice question (with options) to answer.
Which waves have the longest wavelengths but the least energy in the atmosphere? | [
"light waves",
"channel waves",
"microwaves",
"radio waves"
] | D | Some people are allergic to certain foods. Nuts and shellfish are common causes of food allergies. Other common causes of allergies include:. |
SciQ | SciQ-6854 | human-biology, neuroscience, physiology, anatomy
Title: Why does sympathetic activity constrict pulmonary vessels? I don't know understand why sympathetic stimulation constricts pulmonary vessels?
I thought that the sympathetic nervous system activated the body for physical activity. Physical activity would need more oxygen supply. Doesn't constriction of pulmonary vessels reduce the gas exchange? Short answer
The sympathetic nervous system mediates the fight, flight and fright response. It constricts the arteries and arterioles to increase blood pressure, in turn pushing the blood to the muscles and other organs vital for physical activity.
Background
The sympathetic nervous system functions triggers the fight, fright, flight (FFF) response (Fig. 1). It provides the body with a burst of energy so that it can respond to danger (source: Harvard Medical School).
The FFF response is initiated in the hypothalamus by activating the sympathetic nervous system through the adrenal glands. These glands release epinephrine (adrenaline) into the bloodstream. Epi increases heart rate and blood pressure to push blood to the muscles, heart, and other vital organs. The person also starts to breathe more rapidly and the small airways in the lungs open up. This way, the lungs can take in as much oxygen as possible with each breath. Extra oxygen is sent to the brain, increasing alertness (source: Harvard Medical School).
In blood vessels, as you say, sympathetic activation constricts arteries and arterioles (resistance vessels), which increases vascular resistance and decreases distal blood flow. When this occurs throughout the body, the increased vascular resistance causes arterial pressure to increase (Klabunde, 2012). This enhances the distribution of oxygen already present in the blood. I don't think the pulmonary circulation responds differently than that in the rest of the body. The stress response is meant to support the evasion of acute dangers. But indeed, chronic exposure to adrenaline may eventually lead to impaired oxygen exchange in the lungs (Krishnamoorthy et al., 2012).
Fig. 1. Fight, flight, fright response. source: Freelap USA
References
- Klabunde, Cardiovascular Physiology Concepts, 2nd ed. (2012). Lippincott Williams & Wilkins
- Krishnamoorthy et al., Anesthesiology (2012); 117(10): 745-54
The following is multiple choice question (with options) to answer.
The effect of gravity on circulation means that it is harder to get blood up from the legs as the body takes on this? | [
"frontal orientation",
"horizontal orientation",
"vertical orientation",
"dorsal orientation"
] | C | Chapter 15 1 The heart rate increases to send more blood to the muscles, and the liver releases stored glucose to fuel the muscles. 3 The effect of gravity on circulation means that it is harder to get blood up from the legs as the body takes on a vertical orientation. 5 The release of urine in extreme fear. The sympathetic system normally constricts sphincters such as that of the urethra. 7 D 9 C 11 A 13 D 15 A 17 A 19 B 21 B 23 C 25 D 27 Whereas energy is needed for running away from the threat, blood needs to be sent to the skeletal muscles for oxygen supply. The additional fuel, in the form of carbohydrates, probably wouldn’t improve the ability to escape the threat as much as the diversion of oxygen-rich blood would hinder it. 29 The nerves that carry sensory information from the diaphragm enter the spinal cord in the cervical region where somatic sensory fibers from the shoulder and neck would enter. The brain superimposes this experience onto the sensory homunculus where the somatic nerves are connected. 31 Pupillary dilation and sweating, two functions lost in Horner’s syndrome, are caused by the sympathetic system. A tumor in the thoracic cavity may interrupt the output of the thoracic ganglia that project to the head and face. 33 Blood vessels, and therefore blood pressure, are primarily influenced by only the sympathetic system. There is no parasympathetic influence on blood pressure, so nicotine activation of autonomic ganglia will preferentially increase blood pressure. Also, cardiac muscle tissue is only modulated by autonomic inputs, so the conflicting information from both sympathetic and parasympathetic postganglionic fibers will cause arrhythmias. Both hypertension and arrhythmias are cardiac risk factors. |
SciQ | SciQ-6855 | human-biology, cell-biology
Title: What kinds of cells does human saliva contain? I have heard that our saliva contains cells. What cell types can be found in human saliva? It contains white blood cells (leukocytes) and cells from the inner lining of the mouth (buccal epithelial cells). The DNA obtained from these cells is the basis of DNA profiling based on saliva samples.
Source: Salimetrics
The following is multiple choice question (with options) to answer.
Red blood cells, white blood cells and what other cell is found in blood? | [
"plasma cells",
"antibodies",
"hemoglobin",
"platelets"
] | D | Blood consists of liquid plasma, which contains dissolved substances, and three types of cells: red blood cells, white blood cells, and platelets. The main function of blood is transport. Blood also fights infections, repairs tissues, controls pH, and helps regulate body temperature. |
SciQ | SciQ-6856 | spacetime-dimensions
Title: Could we see a lower dimension within our universe? My question refers to the fact, that, say if our universe were to be sitting on a 4 (spatial) dimensional plane, that we cannot see, then within our universe could there be a point mass in which 1 or 2 (spatial) dimensions could exist. We may not be able to see them, this could be a result of our world only consisting of 3 Dimensions. Although the computer screen, for example, is 2Dimensional, it sits on a 3 Dimensional object. Could a 2Dimensional object or world, exist in our 3D plane without having a 3D object that it is displayed upon, I have illustrated it below to build a clearer picture...
I hope this makes sense! Based on the string theory tag in your question, you're probably asking for something like a brane world. In such a scenario, standard model interactions, which are mediated by open strings, and are thus bound to the branes. According to some research (e.g.), it is possible to ensure general relativity also behaves normally on the brane despite the higher dimensionality of spacetime.
The following is multiple choice question (with options) to answer.
How many dimensions can humans see in? | [
"three",
"five",
"one",
"two"
] | A | Humans can see in three dimensions and color. |
SciQ | SciQ-6857 | organic-chemistry, food-chemistry, fats
Title: Saturated vs unsaturated fats - Structure in relation to room temperature state? I'm sure most of us have heard that saturated fats are solid at room temperature, and unsaturated fats are liquid at room temperature. I'm wondering how this relates to their chemical structure -- saturated fats contain only single bonds between carbons, yet to qualify as an unsaturated fat a C=C double bond must exist.
Since a double bond is stronger than a single bond, and the length of the C=C double bond is shorter than that of the single bond, why is it that the fat containing a double bond is a liquid and saturated fats are solids at room temperature? Seems like the double bond would inhibit movement and the resulting substance would be less like olive oil and more like butter. In the solid state, the individual triacylglycerol molecules are interacting with each other primarily through Van der Waals interaction. These weak bonds between molecules are broken at the solid-liquid transition. The amount of energy needed to disrupt these interactions (which determines the melting point of the fat or oil) is determined by the energy associated with all of these bonds added together. In a saturated fat, the acyl chains are able to align perfectly right along their length, maximizing intermolecular interactions. This effect is reflected in the fact that the melting temperature of a pure triacylglycerol increases as the chain length increases.
You can see this effect clearly in the melting temperatures of individual fatty acids. (C18:0 means an 18 carbon molecule with zero double bonds in the acyl chain):
C18:0 (stearic acid) 70°C
C16:0 (palmitic acid) 63°C
C14:0 (myristic acid) 58°C
So the addition of a single -CH2- group in the acyl chain increases melting temperature by a few degrees.
When a cis double bond is introduced into the acyl chain this creates a kink in the structure. Because of this, the acyl chains cannot align completely along their length - they don't pack together as well. Because of this, the sum of the energy associated with intermolecular Van der Waals interactions is reduced. Again this is seen clearly in the melting temperatures of fatty acids:
stearic acid C18:0 70°C
oleic acid C18:1 16°C
The following is multiple choice question (with options) to answer.
What do you call the unhealthy synthetic lipids created when unsaturated fatty acids are artificially manufactured to have straight chains? | [
"polyunsaturated fats",
"omega-3 fatty acids",
"safflower acids",
"trans fatty acids"
] | D | Unsaturated fatty acids occur naturally in the bent shapes shown in Figure above . However, unsaturated fatty acids can be artificially manufactured to have straight chains like saturated fatty acids. Called trans fatty acids , these synthetic lipids were commonly added to foods until it was found that they increased the risk for certain health problems. Many food manufacturers no longer use trans fatty acids for this reason. |
SciQ | SciQ-6858 | paleoclimatology
Has trees, i.e., long-lived woody plants that are capable of growing at least ten meters tall and that grow both upward by extending new branches and outward by widening of the trunk. Amongst other things, this rules out times before ~380 million years ago, which was when the first trees formed.
Has sufficient trees so as to constitute a forest, which I'll define as a largish area where trees grow sufficiently dense so as to form a more or less closed canopy. This distinguishes forests from areas with only a few trees such as savannas and krummholz.
Has very harsh winters, with at least one month where the average temperature is well below freezing, and temperatures of -40° C are not rare. This distinguishes boreal forests from cold oceanic forests such as the Magellanic subpolar forests in southern Chile and Argentina.
Has mild summers, with only a few months where the average temperature exceeds 10° C. This distinguishes boreal forests from hemiboreal and temperate forests. Note that some scientists do not make this distinction, classifying Köppen climate zone Dfb as boreal.
Is extensive. This distinguishes large boreal forests from high altitude subalpine forests that would locally pass the above tests. Subalpine forests can occur at any latitude, including Australia's Snow Mountains, New Zealand's Southern Alps, and parts of the Andes. This is not a clear-cut boundary. As a climate cools, subalpine forests may spread to the valleys between mountains and then spread out beyond the mountains. At some point, such montane forests becomes boreal forests.
The following is multiple choice question (with options) to answer.
In what type of climate might one find deciduous trees? | [
"humid continental",
"Dry Continental",
"moist continental",
"thick continental"
] | A | Deciduous trees are common in humid continental climates. Conifer forests grow in the subarctic. |
SciQ | SciQ-6859 | 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.
Cellular respiration involves forming atp from what type of sugar? | [
"fructose",
"sucrose",
"glutamate",
"glucose"
] | D | Cellular respiration occurs in the cells of all living things. It takes place in the cells of both autotrophs and heterotrophs. All of them burn glucose to form ATP. |
SciQ | SciQ-6860 | quantum-mechanics, waves, wavefunction
Title: Energy carried by matter waves Does the square of amplitude of matter wave is proportional to the energy carried by the wave $mc^2$? Yes ... and no.
Suppose you have a single particle in a wave like state i.e. delocalised and with a well defined momentum. This particle has some wavefunction $\psi$ and the amplitude squared is then $|\psi|^2$. But the particle has to be normalised so:
$$ \int |\psi|^2 dV = 1 $$
That means the amplitude of the wave does not depend on the kinetic energy of the particle, but only on the normalisation condition.
But ...
When we think of a wave like a light wave this is a coherent state of many particles and in that case the integral of the state will give us the number of particles $n$:
$$ \int |\Psi|^2 dV = n $$
And of course the energy is proportional to the number of particles present, so in this sense the amplitude squared is proportional to the total energy.
The following is multiple choice question (with options) to answer.
The magnitude of the wave function at a particular point in space is proportional to what property of the wave at that point? | [
"voltage",
"Sounding",
"frequency",
"amplitude"
] | D | The magnitude of the wave function at a particular point in space is proportional to the amplitude of the wave at that point. Many wave functions are complex functions, which is a mathematical term indicating that they contain. |
SciQ | SciQ-6861 | spacetime, time
Observation of change is important to defining a concept of time. If there are no changes, no time can be defined. But it is also true that if space were not changing, no contours, we would not have a concept of space either. A total three dimensional uniformity would not register.
In special relativity and general relativity time is defined as a fourth coordinate on par with the three space directions, with an extension to imaginary numbers for the mathematical transformations involved. The successful description of nature, particularly by special relativity, confirms the use of time as a coordinate on par with the space coordinates.
It is the arrow of time that distinguishes it in behavior from the other coordinates as far as the theoretical description of nature goes.
Your gedanken experiment of only two particles in a universe can only be a mathematical exercise, the time it has will be the time in the mathematical equations describing your creation and the forces involved. As was observed in the comments static means no time dependence and the problem should be better defined. If you have one hydrogen atom in the universe, that is static, until one goes to the nuclear dimensions, then a mathematical time is need to describe the system.
The following is multiple choice question (with options) to answer.
Representing a leap in scientific understanding, einstein described what as a dent in the fabric of space and time? | [
"motion",
"gravity",
"light",
"energy"
] | B | The above example shows how science generally advances. New evidence is usually used to improve earlier ideas rather than entirely replace them. In this way, scientists gradually refine their ideas and increase our understanding of the world. On the other hand, sometimes science advances in big leaps. This has happened when a scientist came up with a completely new way of looking at things. For example, Albert Einstein came up with a new view of gravity. He said it was really just a dent in the fabric of space and time. |
SciQ | SciQ-6862 | species-identification, botany, ecology
Title: Algae or Lichen identification. Coastal BC, Canada I have tried all books and internet resources I know of, but I still have no idea what this might be — a lichen or something else.
At first glimpse, I thought it was something man-made and unnatural, but then I looked closer and saw how it appears to be attached and growing. It grows on exposed rocks well above the high tide. The photo is taken in late March, on northern Vancouver Island. It's loosely attached to the rock.
It was somewhat abundant around the general area (within of a few km), but I haven't seen it elsewhere - although I'm not from BC so there might be a lot of this around.
The water droplet in the lower right corner give a rough sense of scale.
Edit:
Adding another photo in which I just noticed a streak of white, which I included in original resolution. I want to propose you expand your search to a broader taxonomic scope. Specifically, I think you might be looking at a species of "red" green algae (family: Trentepohliaceae).
From Nelson et al. (2011):
All Trentepohliaceae have filamentous growth forms and often contain large amounts of carotenoid pigments (ß-carotene and hematochrome), causing the algae to appear yellow orange in color (Thompson and Wujek 1997, Lo´pez-Bautista et al. 2002).
The Trentepohliaceae contains five genera: (Trentepohlia, Printzina, Phycopeltis, Cephaleuros and Stomatochroon) and 70+ species worldwide.
For example, the following algae (picture from England) looks fairly similar to your specimen:
Trentepohlia aurea
Source: David Fenwick
If your specimen is a species in this family of algae, it is most likely in the Trentepohlia genus (or possibly Printzina genus).
Trentepohlia is a genus of filamentous chlorophyte green algae in the family Trentepohliaceae.
Typically orange or yellow in color.
Live on tree trunks and wet rocks or symbiotically in lichens.
Here's a picture of a free-living Trentepohlia species from coastal Oregon, USA:
Source: Richard C. Hoyer (2015)
The following is multiple choice question (with options) to answer.
Green algae and land plants are closely what? | [
"related",
"unrelated",
"different",
"foreign"
] | A | |
SciQ | SciQ-6863 | genetics, dna, chromosome, biotechnology, allele
Title: Do we come to know which allele is dominant by seeing family genration tree only? I know that a Gene has Alleles (variation) and one is Dominant over Other i.e the Other Recessive.
Then I got a Thought that How can we tell whether an Allele is Dominant or Recessive...... and I came across this Site while Googling, and It says we can tell this by Observing Patterns in the Family Generation Tree.
So, my question is that can we only describe an Allele by observing pattern? Is there any other Method or by looking at the Molecular level and tell?
Please extend this "How can we tell whether an Allele is Dominant" to a Special Case where a Gene has 3 Alleles.....can we have 2 Dominant Allele? Addressing Your First Question
We can tell whether an allele is dominant or recessive based on patterns in family trees, that is true, and it is very helpful! However, that is not the only way, since by looking at the molecular function of the alleles, the dominant and recessive relationship between alleles can be assessed without needing to look at family trees!
I think a deeper understanding of what it means to be dominant versus recessive would be helpful, because usually biology isn't just that simple! In most scenarios where there is a distinct recessive and dominant trait, it is because the dominant trait causes some specific activity/functioning protein while the recessive trait does not. Let's look at an example of this:
Let's choose eye color:1
There are multiple genes that affect eye color but let's just look at one: the one that codes for the brown pigment (melanin) to be produced in the iris [specifically the HERC2 gene]. As you probably already know, brown eyes are dominant and blue eyes are recessive.
The following is multiple choice question (with options) to answer.
How many alleles control a characteristic? | [
"3",
"8",
"4",
"2"
] | D | A characteristic may be controlled by one gene with two alleles, but the two alleles may have a different relationship than the simple dominant-recessive relationship that you have read about so far. For example, the two alleles may have a codominant or incompletely dominant relationship. The former is illustrated by the flower in Figure below , and the latter in Figure below . |
SciQ | SciQ-6864 | biochemistry
Title: Food which does not produce urea My professor of bioengineering said that all foods produce urea. Do foods exist which does not produce urea?
Thank you very much. Food doesn't produce urea, your body produces urea from the nitrogen content of the food you eat (mostly comes from proteins). So you can eat e.g honey, which contains minimal, if any, amount of nitrogen.
The following is multiple choice question (with options) to answer.
All living things are able to produce what? | [
"tissue",
"offspring",
"proteins",
"toxins"
] | B | |
SciQ | SciQ-6865 | plate-tectonics, mountains, orogeny
Just doing some quick googling, it sounds like Arizona also has both volcanic feature and eroded remnants of volcanic features. These kinds of mountains/hills are formed via a different method again, and their heights are controlled by their own method of formation. Volcanoes can vary a lot in height. They can be very small, like the volcanoes in south-east Australia where I live, or very large, like the volcanoes in the Andes mountain range, or they can be large, but broad and flat, like Hawai'i.
Erosion can carve out softer rock and leave behind more resistant stuff, and this is how some smaller hills/mountains are formed (like Uluru in central Australia). I found this online which might lead you in some interesting directions: Geologic History of Arizona By Jan C. Rasmussen
The following is multiple choice question (with options) to answer.
What is the smallest volcanic landform that is formed from accumulation of many small fragments of ejected material? | [
"cinder cones",
"log cones",
"edifice cones",
"concave cones"
] | A | Cinder cones are the smallest volcanic landform. They are formed from accumulation of many small fragments of ejected material. |
SciQ | SciQ-6866 | ocean, waves, ocean-currents, tides
(i) Wave generation by wind—the effective wind is that relative to the surface current, and the wave age (cp/U*) and effective surface roughness may be important, e.g., Janssen (1989). Here cp is the wave phase speed and U* is the friction velocity of the wind. The effective fetch also changes in the presence of a current.
(ii) Wave propagation—the effects of depth refraction are easy to spot, turning the mean wave direction towards shore-normal. Current refraction has a more subtle effect, dependent on the spatial variation of currents, whether decreasing or increasing towards the coast. Generally shoaling depths will increase the tidal amplitude towards the coast until friction reverses this trend. The waves will tend to turn towards the direction of the current axis.
(iii) Doppler shift—the effect of a steady current on intrinsic (relative) wave frequency. Waves of the same apparent (absolute) period will have a longer intrinsic period in a favourable (following) current and a shorter intrinsic period in an opposing current.
(iv) Steepening of waves on an opposing current (related to (iii)), due to shorter wavelength and increased wave height from wave action conservation.
(v) Modulation of absolute frequency by unsteady currents and modulation of intrinsic frequency by propagation over spatial gradients of current. If the current is steady the absolute frequency should be constant, if the current is homogeneous the intrinsic frequency should be constant. If both intrinsic and absolute period show a tidal modulation, the currents must be effectively inhomogeneous and unsteady.
(vi) Wave–current bottom stress. Various empirical theories for wave–current interaction in the bottom boundary layer suggest that the friction coefficient experienced by waves in a current regime will be larger than in no current. This also applies to the effective current friction factor in the presence of waves.
(vii) Effect of vertical current shear on wave breaking. Wind-driven surge currents would be relevant to this, the tidal currents have no surface shear.
The following is multiple choice question (with options) to answer.
What are surface currents mainly caused by? | [
"winds",
"rains",
"waves",
"lightning"
] | A | Surface currents are like streams flowing through the surface of the ocean. They are caused mainly by winds. Earth’s rotation influences their direction. This is called the Coriolis effect. Surface currents may affect the climate of nearby coasts. |
SciQ | SciQ-6867 | bond, atoms, molecules, valence-bond-theory
So the short answer to your first question is: "Molecular orbitals hold atoms together in covalent bonds, and those are a result of electrostatic interactions and the quantum nature of electrons."
Yes, ionic compounds are large collections of ions, and you can't really define "molecules" for them - instead we talk about "formula units" which are the lowest possible whole-number ratio of elements that represent the compound. Groups of covalently bonded atoms are also held together by electrostatic interactions, but since the covalent bonds are so much stronger, a molecular compound can exist "on its own" as a single molecule. Collectively, the forces that hold collections of molecules together are called van der Waals forces if they don't involve ions. In any atom or molecule, there is never a completely uniform charge density on the surface. For some molecules, this is extreme (water is a good example) and we say it is very polar, or that it has a large dipole moment. This is just another way of saying that one part has a negative charge and the other has a positive charge. In water it looks like this (from wikipedia):
In this picture, red means "more electrons" and blue means "less electrons." Water can form hydrogen bonds, which are very strong electrostatic interactions. Some atoms and molecules have an almost uniform charge density on the surface. We call these "non-polar" molecules - noble gases are good examples. However, even noble gases have what is called an induced dipole due to statistically correlated fluctuations in electron density when the atoms are near each other. As a result, even noble gases can be cooled to the point where they become liquid - the very, very weak electrostatic interactions will hold them together at low temperature, when they are not moving very fast. These forces are called London Dispersion Forces - after the guy who first described them. London dispersion forces are important, because they are found in all molecules - polar or not. In fact, this is what makes most plastics solid. Polyethylene, for example, is made of very long chains of essentially non-polar molecules (from wikipedia):
The following is multiple choice question (with options) to answer.
What kind of solids are generally classified by the forces that hold their particles together and include ionic, metallic, covalent network, and molecular types? | [
"flat solids",
"distinct solids",
"crystalline solids",
"helium solids"
] | C | Crystalline solids are generally classified according the nature of the forces that hold its particles together. These forces are primarily responsible for the physical properties exhibited by the bulk solids. The following sections provide descriptions of the major types of crystalline solids: ionic, metallic, covalent network, and molecular. |
SciQ | SciQ-6868 | astronomy, experimental-technique, distance
Title: How do astronomers measure the distance to a star or other celestial object? How do scientists measure the distance between objects in space? For example, Alpha Centauri is 4.3 light years away. There are a variety of methods used to measure distance, each one building on the one before and forming a cosmic distance ladder.
The first, which is actually only usable inside the solar system, is basic Radar and LIDAR. LIDAR is really only used to measure distance to the moon. This is done by flashing a bright laser through a big telescope (such as the 3.5 m on Apache Point in New Mexico (USA), see the Apollo Project) and then measuring the faint return pulse with that telescope from the various corner reflectors placed there by the Apollo moon missions.
This allows us to measure the distance to the Moon very accurately (down to centimeters I believe). Radar has been used at least out to Saturn by using the 305 m Arecibo
radio dish as both a transmitter and receiver to bounce radio waves off of Saturn's moons. Round trip radio time is on the order of almost 3 hours.
If you want to get distances to things beyond our solar system, the first rung on the distance ladder is, as Wedge described in his answer, triangulation, or as it is called in astronomy, parallax. To measure distance in this manner, you take two images of a star field, one on each side of the Earth's orbit so you effectively have a baseline of 300 million kilometers. The closer stars will shift relative to the more distant background stars and by measuring the size of the shift, you can determine the distance to the stars. This method only works for the closest stars for which you can measure the shift. However, given today's technology, that is actually quite a few stars. The current best parallax catalog is the Tycho-2 catalog made from data observed by the ESA Hipparcos satellite in the late 1980s and early 1990s.
Parallax is the only direct distance measurement we have on astronomical scales. (There is another method, the moving cluster method, but it has very limited applicability.) Beyond that everything else is based on data calibrated using stars for which we can determine parallax. And they all rely on some application of the distance-luminosity relationship
The following is multiple choice question (with options) to answer.
What can often be used to measure distance? | [
"maps",
"models",
"histograms",
"graphs"
] | A | Maps can often be used to measure distance. The map in the Figure below shows the route from Jordan’s house to his school. You can use the scale at the bottom of the map to measure the distance between these two points. |
SciQ | SciQ-6869 | asteroids, comets, extinction
This is somewhat doable, but quickly get complex (different populations, orbits are not actually evenly distributed, etc.) A better approach may simply be to look at the past impacts causing extinctions! Depending on how you count, there has been one known mass extinction due to impacts since the Cambrian 538.8 mya, so the rate might be on the order of $2\cdot 10^{-9}$ per year. But that likely leaves out a fair number of minor extinctions. If we assume all Big 5 were due to impacts the rate becomes $9\cdot 10^{-9}$ per year.
Incidentally, to get these values in the above formula for the assumed values, $N$ should be in the range 0.2 to 1.
Obviously this can be improved: we can use statistical modelling to get error bars, we can use the known size distribution of asteroids (a power law) to estimate the fraction of Earth-crossers and long-periodic comets that could be bad and their inflow rate, and so on. But that misses the Drake equation approach of trying to find a quick-and-dirty model that shows the key variables we care about and might want to estimate.
The following is multiple choice question (with options) to answer.
Which single most factor is responsible for the extinction of hundreds of species of birds? | [
"animal actions",
"habitat",
"human actions",
"diet"
] | C | Hundreds of species of birds have gone extinct as a result of human actions. A well-known example is the passenger pigeon. It was once the most common bird in North America, but over-hunting and habitat destruction led to its extinction in the 1800s. Habitat destruction and use of the pesticide DDT explain the recent extinction of the dusky seaside sparrow. This native Florida bird was declared extinct in 1990. |
SciQ | SciQ-6870 | biochemistry
Another important difference with respect to resulting polymers formed from these bonds - polysaccharides, in contrast to proteins and nucleic acids, form branched as well as linear polymers
α-Amylose is a linear polymer of several thousand glucose residues linked by α(1 >4) bonds. Note that although α-amylose is an isomer of cellulose, it has very different structural properties. This is because cellulose’s β-glycosidic linkages cause each successive glucose residue to flip 180° with respect to the preceding residue, so that the polymer assumes an easily packed, fully extended conformation.
Peptide bond
The resulting linkage formed when α-amino acids polymerize, through the elimination of a water molecule is known as a peptide bond (sometimes called an amide bond):
Peptide bond (shown in red)
Glycosidic bonds between monosaccharide units are the basis for the formation of oligosaccharides and polysaccharides.
The glycosidic bond is therefore the carbohydrate analog of the peptide bond in proteins. (The bond in a nucleoside linking its ribose residue to its base is also a glycosidic bond)
The following is multiple choice question (with options) to answer.
The differing glycosidic linkages in starch and cellulose give the two molecules what kind of distinct shapes? | [
"diamond",
"one-dimensional",
"three-dimensional",
"square"
] | C | |
SciQ | SciQ-6871 | botany, reproduction
Title: Are the seeds in a single capsicum fruit genetically identical? Hopefully not a too-basic question for the venue. I'm a chile pepper growing hobbyist and have spent some time searching around and reading up on pepper (angiosperm) reproduction, but I'm not getting a clear picture of the details.
It seems like flowers have multiple ovules and it seems like one pollen-grain landing on the stigma leads to fertilization of a single ovule. And it seems like that process produces a single seed.
But that fertilization also prompts fruit growth and flower death and capsicum fruits have many seeds, never just one (that I've ever seen).
So, does each seed have a potentially different father? Or are the multiple seeds generated through a reproductive/cloning process that I'm not seeing written about? Or something else? No, the seeds are not genetically identical. Each seed come from the fertilization of an ovum with a sperm from a separate pollen grain. Since each pollen grain can come from a different plant, the seeds will generally differ from one another.
Additionally, even ova from a single plant will not usually be genetically identical to one another. This is because the process that creates the ova (meiosis) shuffles the genes of the parent plant on then places only half into the ovum. The same kind of shuffling goes on in the creation of pollen grains.
In the chili pepper genus (Capsicum), plants are predominantly self-pollinating. This means the majority of the pollen for the seeds in a fruit will come from the very same plant. This generally reduces the amount of variation seen in the offspring compared to complete cross-plant pollination. Some cross-pollination can nevertheless occur if there are other varieties in the neighborhood. The fruit will not show the effects of the new genetic combinations present in its seed, but only a plant grown from the seed will make the differences evident.
The following is multiple choice question (with options) to answer.
What is the angiosperm seed surrounded by? | [
"egg",
"uterus",
"cone",
"ovary"
] | D | The two major divisions of seed plants are the gymnosperms (seeds in cones) and angiosperms (seeds in ovaries of flowers). Figure below shows how the seeds of gymnosperms and angiosperms differ. Do you see the main difference between the two seeds? The angiosperm seed is surrounded by an ovary. |
SciQ | SciQ-6872 | proteins, food, digestive-system, amino-acids, digestion
Title: How are proteins reused in the body? Part of what we eat are proteins,
and our body is in part build of proteins.
Are the proteins of the body build based on proteins in food at all?
Are proteins in food directly reused in the body,
or are proteins first disassembled?
How far are they disassembled, randomly in various pieces, or systematically to keep what can optimally be used to build new proteins, while nothing is wasted for energy?
(The question Can proteins/peptides pass through the intestine? and it's answers are related, and provide some context and relevant parts, but is not a duplicate.) Short answer: Indeed the proteins in our body are based on amino acids from external food sources. BUT, proteins up-taken from food are ALWAYS disassembled first into amino acids, through specialized enzymes, proteases, (for instance Pepsin in the stomach's gastric juices and Tripsin in the pancreatic juices), during digestion, in the alimentary canal, (gut). This enables the body's liver to build the proteins most needed by the organism itself, through the processes of transamination, that allows conversion betwixt amino acids, and deamination, that removes N2 from the amino acid, (let's say the "amino" part is removed, and then expelled as urea), to excrete amino acids in excess. In addition this breaking down of external proteins is necessary, since they can act as labels for pathogens, and external organisms in general, and thus would soon be destroyed by the immune system if reused straight away.
The following is multiple choice question (with options) to answer.
Which process helps bacteria in the gut break down the remains of the digested food? | [
"fermentation",
"synthesis",
"oxidation",
"decomposition"
] | A | Behind every fart is an army of gut bacteria undergoing some crazy biochemistry. These bacteria break down the remains of digested food through fermentation, creating gas in the process. Learn what these bacteria have in common with beer brewing at http://youtu. be/R1kxajH629A?list=PLzMhsCgGKd1hoofiKuifwy6qRXZs7NG6a . |
SciQ | SciQ-6873 | zoology, microbiology, pathology
Title: Prevention of disease spreading in animal kingdom It's my first question on here, so I'm not sure If my question fits the theme. Please refer me to the appropriate one, If I have made a mistake.
So a question that I wanted to ask has to do with whether or not animals potentially try to avoid spreading diseases. So I was thinking... In an event that a really deadly disease emerges in a population, it would be really dangerous for animals that live in social groups, of any size really, not to have any instinctual behaviours that try and prevent the disease to spread. Animals that live in big heads, like wildebeests would just probably leave the diseased individuals behind, apes and monkey could potentially cast out individuals from the group, etc. Ants have separate sections in their tunnels that serve as graveyards, I presume for this exact purpose.
A lot of parasitic organisms have adaptations that specifically target animals with social behaviour, so why wouldn't animals adapt against that?
Something that also came to my mind is that this could possibly evolve not as a social behaviour of a group, but sometimes that individuals in a group would do, for example self isolation. However, I do not find this likely, I possibly requires higher cognitive understanding of disease spread.
Am I way of base here? If not, could you please provide some interesting examples you are familiar with.
The following is multiple choice question (with options) to answer.
Unlike wild animals, what type of species are genetically uniform, making them more vulnerable to die-out from disease? | [
"urbane species",
"domestic species",
"mammals",
"free-range species"
] | B | Wild plants and animals maintain a valuable pool of genetic variation . This is important because domestic species are genetically uniform. This puts them at great risk of dying out due to disease. |
SciQ | SciQ-6874 | evolution, herpetology, dinosaurs
Title: Evolution of dinosaurs What did dinosaurs evolve from? Was it the reptiles that evolved from amphibians? I have been researching this but am very confused with who their direct predecessor was. Amphibians evolved from fish...reptiles from amphibians...dinosaurs from reptiles (?)...and birds from dinosaurs. That is my understanding, but it could be wrong. How are dinosaurs related to reptiles? And if they did evolve from reptiles, which kind of reptiles (such as lizards, crocodiles, or turtles for example)? Source of information
See the post The best free and most up to date phylogenetic tree on the internet? for info about how to find such information.
Generally speaking, you might be interested in an intro to phylogenetics such as the one provided in this answer for example.
Where are dinosaurs in the tree of life?
Dinosaurs fall within the Reptiliomorpha clade. Please note that Reptiliomorpha does not quite correspond to what we today call reptiles. Please see the post If dinosaurs could have feathers, would they still be reptiles?
Reptiliomorpha is the sister clade to Amphibia (from here) which contain all living amphibians.
If you look within the Amniota, you will find all of the following
Here, you see that turtles and mammals are an off-shoot of Diapsida. So dinosaurs are not mammals and there are not closely related to turtles. Now if you click on Diapsida you will find ...
the Archosauromorpha which contains all crocodiles, birds and dinosaurs. You can keep going to find Therapoda which contains many dinosaurs and birds. You can keep going like this for yourself and discover the entire tree of life!
Reacting to your sentences
What did dinosaurs evolve from?
When asking this question, please do not forget that no species evolved from an extant species. If this is unclear to you, you should have a look at this post.
Was it the reptiles that evolved from amphibians?
Well... the term reptile is a mess because it does not represent a monophyletic group (see this post). If you do not understand the term monophyletic, then you should have a look at this answer.
Amphibians evolved from fish...
The following is multiple choice question (with options) to answer.
The diapsids diverged into two groups, the archosauromorpha (“ancient lizard form”) and the lepidosauromorpha (“scaly lizard form”) during what time period? | [
"cenozoic",
"mesozoic",
"paleozoic",
"holocene"
] | B | The diapsids diverged into two groups, the Archosauromorpha (“ancient lizard form”) and the Lepidosauromorpha (“scaly lizard form”) during the Mesozoic period (Figure 29.22). The lepidosaurs include modern lizards, snakes, and tuataras. The archosaurs include modern crocodiles and alligators, and the extinct pterosaurs (“winged lizard”) and dinosaurs (“terrible lizard”). Clade Dinosauria includes birds, which evolved from a branch of dinosaurs. |
SciQ | SciQ-6875 | everyday-chemistry, conductivity, electricity
Title: Can dust conduct electricity? Just out of curiosity, can dust conduct electricity? The source of dust varies, is there any form of dust that can conduct electricity? The answer to this question hinges on two key questions:
What kind of dust are we dealing with?
How is the dust arranged (i.e. what is your experimental setup)?
Which Dust?
Firstly, I'm going to assume you meant domestic dust (since there are more kinds of dust than you'd imagine).
I quote Wikipedia:
Dust in homes, offices, and other human environments contains small amounts of plant pollen, human and animal hairs, textile fibers, paper fibers, minerals from outdoor soil, human skin cells, burnt meteorite particles, and many other materials which may be found in the local environment.
Arrangement
The arrangement of the dust particles is key. Are we considering an aerosol, or are we carefully laying a line of dust on the table and connecting it with two electrodes?
Aerosol - We can safely assume that the conductance of air has a far higher impact on the measurement than the conductance of the particles in the aerosol (the dust). So here, dust does not conduct electricity. Note: I ignore the "conducting" via static electricity processes here, but they may play a role. I do not consider that "classical" conductance.
Line of Dust - Organic material is usually insulating, as is our skin (if it wasn't for the moisture that is needed for, you know, living), paper, textiles, hair and so on. So the main constituents of domestic dust does not conduct electricity. So also here, we will not observe conductance.
There is one exception to the above, where conductance is a possibility: Metal dust. This is kind of cheating, but consider the waste of some metalworking process, in which metal dust (or powder) is generated. This dust, being composed of metals and metal oxides, would likely conduct electricity (when laying it out in a line, still not as an aerosol).
The following is multiple choice question (with options) to answer.
A few elements, called what, can conduct electricity, but not as well as metals? | [
"gases",
"halogens",
"synthetics",
"metalloids"
] | D | A few elements, called metalloids, can conduct electricity, but not as well as metals. Examples include silicon and germanium in group 14. Both become better conductors at higher temperatures. These elements are called semiconductors. |
SciQ | SciQ-6876 | exoplanet
It's probably possible to have volcanic eruptions even though dozens or maybe even hundreds of miles of exotic ice because the heat has to go somewhere, eventually, assing it's likely to build up over time, so either by circulation of eruption, the heat has push through at some point. This even happens on so called "dead" planets like Mars or even the Moon. Mars still has the occasional volcanic eruption, just not very often.
But water worlds certainly can have plate tectonics. There's nothing in the water that would prevent it from happening. Plate Tectonics is, as I understand it, primarily a factor of the size of the planet. Gas planets - different story, but planets with a hard surface, Earth sized, a tiny bit smaller to a fair bit but not much bigger are good candidates for plate tectonics (I think). There's some debate on how large, I think, still going on. But I remember reading that ocean/water worlds might even be more likely to have plate tectonics. Plate tectonics is definitely something we'd look for if we ever get a close enough look at other planets in different solar-systems (exoplanets).
Just my thoughts on this. Not meant to be complete or definitive.
The following is multiple choice question (with options) to answer.
Which type of eruptions created the entire ocean floor? | [
"fault eruptions",
"fissure eruptions",
"formation eruptions",
"lava effusion"
] | B | The most obvious landforms created by lava are volcanoes. These are mostly cinder cones, composite volcanoes, and shield volcanoes. Eruptions also take place through other types of vents, commonly from fissures ( Figure below ). The eruptions that created the entire ocean floor are essentially fissure eruptions. |
SciQ | SciQ-6877 | neuroscience, neurophysiology, sensation, hearing, human-ear
Title: Why/how does exposure to noise cause cochlear hair-cell loss? I am trying to understand why listening to loud music - e.g. concerts or earphones at high volume damages hearing.
According to the National Institute on Deafness the cause is physical.
Most NIHL is caused by the damage and eventual death of these hair
cells. Unlike bird and amphibian hair cells, human hair cells don’t
grow back. They are gone for good.
But I don't understand why/how would noise - which should basically lead to higher amplitude waves in the basilar membrane, induce damage and death of these hair cells? There are a number of pathophysiological mechanisms that are thought to underlie noise-induced hearing loss:
Mechanical damage to the delicate cells and supporting structures of the organ of Corti;
Reduced blood flow to the inner ear;
Intense metabolic activity, which increases mitochondrial free radical formation.
Reactive oxygen species (ROS) are highly reactive. They are essential for mitochondrial function to generate energy. However, too many of them damage cellular lipids, proteins, and DNA, and upregulate apoptotic pathways. The observed impaired blood flow to the cochlea can enhance the toxic effects of ROS. Mechanical damage to the delicate hairs and membranes of the hair cells reduces their ability to converge acoustical energy into potential differences.
References
- Le Prell et al., Hear Res (2007); 226(1-2): 22–43
- Kurabvi et al., Hear Res (2017); 349: 129-37
The following is multiple choice question (with options) to answer.
What is damaged in the inner ear by loud sounds that cause hearing loss? | [
"ear drum",
"hair cells",
"hammer and anvil",
"tympanic membrane"
] | B | Loud sounds can cause hearing loss by damaging hair cells in the inner ear. The louder the sounds are, the less exposure is needed to cause hearing loss. |
SciQ | SciQ-6878 | universe, cosmology
Title: Why aren't other kinds of energies considered in the mass-energy of the universe? Mass-Energy of the Universe:
5% ordinary matter,
27% dark matter,
68% dark energy
What about other energies such as thermal energy, potential energy, kinetic energy, chemical energy, and radiant energy? Various missions such as WMAP and the Planck Satellite have measured the mass-energy content of the universe. You tend to see images like the one below produced by these scientific ventures.
The following is multiple choice question (with options) to answer.
The energy in sunlight is also known as what kind of energy? | [
"geothermal energy",
"kinetic energy",
"solar energy",
"potential energy"
] | C | The energy in sunlight, or solar energy, can be used to heat homes. It can also be used to produce electricity in solar cells. However, solar energy may not be practical in areas that are often cloudy. |
SciQ | SciQ-6879 | energy, physical-chemistry, freezing
The rate at which heat is added to convert the pure cube ice to water is
$$\dot Q_{pure}=h_{c}A(33^{o} C - 32^{o} C)$$
Where $h_c$ is the overall heat transfer coefficient of the ice/water mixture, assumed to be the same for the pure and impure ice/water phase.
Under the assumption that $h_c$ is the same for the pure and impure cube, the heat transfer rate during the phase transition for the pure cube will be less than the impure cube because of the smaller temperature difference of 1 C for the pure ice vs. 3 C for the impure ice.
Given the above, if the assumptions are correct, I would conclude
The following is multiple choice question (with options) to answer.
In what form is the heat absorbed when you heat ice and it reaches a temperature of 0 c? | [
"potential energy",
"radiation energy",
"mechanical energy",
"geothermal energy"
] | A | The heating curve shown is for water but other substances have similarly shaped heating curves. Suppose you begin with solid water (ice) at -30°C and add heat at a constant rate. The heat you add in the beginning will be absorbed as kinetic energy and the temperature of the solid will increase. When you reach a temperature of 0°C (the melting point for water), the heat you add is no longer absorbed as kinetic energy. Instead, the added heat is absorbed as potential energy and the particles separate from each other. During the flat part of the curve labeled “melting”, heat is being added constantly but the temperature does not increase. At the left edge of this flat line, the water is solid; by the time enough heat has been added to get to the right edge, the water is liquid, but maintains the same temperature. Once all the water is in the liquid form, the added heat will once again be absorbed as kinetic energy and the temperature will increase again. During the time labeled “water being heated as a liquid”, all the added heat is absorbed as kinetic energy. |
SciQ | SciQ-6880 | organic-chemistry, intermolecular-forces, enzymes
Scheme 4A from the preprint linked above illustrates well the specifics of the chemistry. (I refrain from reproducing it here due to uncertainty regarding its copyright/license status.)
As well, Figure 2 from the Mechanism Description section of the Wikipedia page on thymidylate synthase shows very nicely the enzyme interactions with the normal deoxyuridylate substrate (click image for larger version):
$\hspace{20pt}$
Image by CJerc (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0 )], via Wikimedia Commons
$^\dagger$ Mishanina et al. Bioorganic Chemistry 43: 37 (2012). doi:10.1016/j.bioorg.2011.11.005
The following is multiple choice question (with options) to answer.
The sugar of one nucleotide binds to what group of the next nucleotide? | [
"the alkaline",
"the phosphate",
"the chloride",
"the protein"
] | B | The sugar of one nucleotide binds to the phosphate group of the next nucleotide. Alternating sugars and phosphate groups form the backbone of a nucleotide chain, as shown in Figure below . The bases, which are bound to the sugars, protrude from the backbone of the chain. In DNA, pairs of bases-one from each of two nucleotides-form the middle section of the molecule. |
SciQ | SciQ-6881 | eyes, vision, human-eye
Ideas so far
Does the eye try focusing either a little nearer or further and then if that doesn't help to make the object clearer then the eye focuses in the opposite direction?
Or is there some light-sensitive apparatus that is always a focused a little nearer or further than the rest of the eye, and so for instance if the cells which are focused further out are giving a clearer picture than the other cells then the eye knows to focus further out?
Or is the blurriness of a object closer than the focal point a distinguishably different sort of blurriness than an object beyond than the focal point?
Or is there some other mechanism altogether? Interesting question! Determining the focus of a visual image is carried out in the visual association area of the brain. Ultimately, this process results in focusing of the retinal image by adjustment of the shape of the lens in the eye. Lens shaping to focus the image is called accommodation
The neuronal circuitry involved in accommodation includes the following structures:
The input to the accommodation response is provided by the retina, optic nerve, thalamus, and visual cortex. The visual cortex projects to the association cortex.
The (simplified) output scheme is the following: The association cortex projects to the supraoculomotor nuclei, which in turn generates motor control signals that initiate the accommodation response. The signal is then sent bilaterally to the oculomotor complex, and hence input from one eye is enough to focus both eyes.
The motor output regulates the ciliary muscles that control the shape of the crystalline lens. Negative accommodation adjusts the eye for long distances by relaxation of the ciliary muscles. Positive accommodation adjustment of the eye for short distances by contraction of the ciliary muscles Medical Dictionary.
As to the second part of your question: how out-of-focus images are functionally recognized:
There are at least three mechanisms responsible for accommodation:
The following is multiple choice question (with options) to answer.
How does the image focused by the eye travel to the brain? | [
"the modulated nerve",
"the optic nerve",
"the secondary nerve",
"the sensory nerve"
] | B | The image focused by the eye travels through the optic nerve to the brain as electrical signals. The brain interprets the signals and “tells” us what we are seeing. |
SciQ | SciQ-6882 | molecular-genetics, human-genome
Title: Criteria for the numbering of human chromosomes What were the criteria devised for the numbering convention employed in human chromosomes? When was it fixed?
Correct me if I am wrong; it appears that chromosome pairs 1 to 22 were originally ordered in terms of perceived structural size, which ended up fitting neatly with the quantity of base pairs (but not with the quantity of genes).
The sex chromosomes in turn were arbitrarily assigned as "pair 23".
Is this sound?
Thanks in advance. Why do you think it was "fixed?" Here's a nice review of the history of human cytogenetics, which included not only the original image from 1956 but points out a report which comments on the standardization of chromosome number. The autosomes were indeed numbered by length, and the sex chromosomes are traditionally put at the end as they are "numbered" 23 but clearly function quite differently. Gene content was decades away from being known at the time, and honestly isn't even known now. It's also just as arbitrary; simple size is easy enough and makes for rather nice pictures.
The following is multiple choice question (with options) to answer.
If a human only has 45 chromosomes it is most likely due to a mistake during what? | [
"plexus",
"meiosis",
"mitosis",
"testis"
] | B | So far we have focused on traits due to one gene or several genes. But what about many genes? 100s or 1000s of genes? What would happen if an entire chromosome were missing or duplicated? What if a human had only 45 chromosomes? Or 47? This real possibility is usually due to mistakes during meiosis; the chromosomes do not fully separate from each other during sperm or egg formation. Specifically, nondisjunction is the failure of replicated chromosomes to separate during anaphase II. If a zygote forms from a gamete lacking a chromosome, a viable embryo cannot be produced. Most human abnormal chromosome numbers result in the death of the developing embryo, often before a woman even realizes she is pregnant. Occasionally, a zygote with an extra chromosome can become a viable embryo and develop. |
SciQ | SciQ-6883 | 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.
The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by this? | [
"skin",
"mucus",
"connective tissue",
"bone"
] | C | The Peritoneum The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by connective tissue. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelopes the abdominal organs (Figure 23.4). The peritoneal cavity is the space bounded by the visceral and parietal peritoneal surfaces. A few milliliters of watery fluid act as a lubricant to minimize friction between the serosal surfaces of the peritoneum. |
SciQ | SciQ-6884 | astronomy, everyday-life, popular-science, climate-science
Title: Why is the summer, in the temperate latitudes, in average, hotter that the spring? It is common knowledge that the transition from the Spring to the Summer season occurs in the Summer Solstice when the "Sun reaches its highest excursion relative to the celestial equator on the celestial sphere" (as stated in Wikipedia).
It is also stated in Wikipedia' Summer page:
"Days continue to lengthen from equinox to solstice and summer days progressively shorten after the solstice, so meteorological summer encompasses the build-up to the longest day and a diminishing thereafter, with summer having many more hours of daylight than spring."
My question is: why is the summer, in the temperate latitudes, in average, hotter that the spring? A major part of the reason for this is due to the temperature of the ground. While the length of days in the Summer are effectively a mirror of those in Spring, you must take into consideration more than that.
When Spring commences in temperate climates, it is (usually) immediately preceded by winter. Due to the Winter, the ground and/or surrounding bodies of water are very cold. This has the effect of cooling the air for the first part of Spring while the ground/water begins to thaw/warm up. Furthermore, it takes much longer to warm or cool a body of water than a mass of air; even longer to warm or cool the ground and water. Therefore, as Spring progresses and the days become longer (also meaning the Sun is higher above the horizon, thus providing more heating power), the sunlight must first overcome the cooling effects of the ground and water bodies. Near the end of Spring - when the days are sufficiently long and the Sun is much higher above the horizon - you should notice the weather becoming hotter. This is because the ground and water has had time to warm up, which means it is not constantly cooling the air and making it feel colder.
When you then transition to Summer, the ground is already sufficiently warm but the days are still long and the Sun is still high in the sky. This means the Sun can heat the ground, water, and air even more and without any cooling effects. This allows the Summer temperature to be easily higher than that of the Spring temperatures. If Summer were immediately preceded by winter, you might notice the weather getting warmer much more quickly, but the average temperature would be very close to that of the Spring.
The following is multiple choice question (with options) to answer.
What season causes people to look forward to spring? | [
"winter",
"fall",
"autumn",
"summer"
] | A | In the winter, many people find the snow and ice beautiful. They enjoy getting out to ski or ice-skate. Others don’t find that time of year to be so much fun. When the snow melts, the roads get very sloppy and messy. Those people look forward to spring when all the ice and snow are gone and the weather is warmer. |
SciQ | SciQ-6885 | homework, cell-membrane, human-physiology, lungs
Title: How many cell membranes are oxygen and carbon dioxide diffuse through in the lungs? In the lungs, oxygen and carbon dioxide pass through cell membranes by diffusion.
Which row is correct?
The correct answer is D, but I think it should be B. I can only think about three layers as maximum which are; epithelium of alveolus, endothelium of capillaries and the membrane of red blood cell. I don't know what are remainings.
Any help would be much appreciated! Oxigen goes from the alveolar's lumen to the cytoplasm of the erythrocyte, and that's 5 membranes:
the "top" of the alveolar epithelial cell
the "bottom" of such cell
the "top" of the endothelial cell (capillary)
the "bottom" of such cell
the erythrocyte membrane
You got all the cells right, but your only problem was this: oxygen diffuses through the cell membrane entering the cell, moves through the cytoplasm, and diffuses through the membrane again exiting the cell. So, for each cell, you have to count 2 membranes. For the last one, the erythrocyte, you have only 1 membrane (because it is $\ce{O2}$ final destination).
For the $\ce{CO2}$ the situation is a little bit more tricky. We have the same 4 membranes (2x epithelial cell and 2x capillary), but $\ce{CO2}$ can come from 2 locations:
from the erythrocyte, where it is formed from $\ce{H2CO3}$ (by the reaction $\ce{H2CO3 -> H2O + CO2}$) or released from the N-terminal group of proteins, like haemoglobin (where it has previously bound)
from the plasma (around 9% of the $\ce{CO2}$).
In the first case we have 5 membranes, and in the second case just 4.
So, the correct answer is D.
The following is multiple choice question (with options) to answer.
What are the narrowest blood vessels, where oxygen is transferred into body cells? | [
"capillaries",
"viens",
"muscles",
"arteries"
] | A | Red blood cells are flat, round, and very small. Their small size allows easy maneuverability through the capillaries, the narrowest blood vessels, where oxygen is transferred into body cells. |
SciQ | SciQ-6886 | experimental-physics, nuclear-physics, radioactivity, statistics, half-life
$$t_{\rm average} = \frac{6.45\times 10^9\times 365.2422\times 86400}{2.53\times 10^{24}}{\rm seconds} = 8.05\times 10^{-8} {\rm seconds}. $$
So one gets about 12.4 million decays during one second. (Thanks for the factor of 1000 fix.) These decays may be observed on an individual basis. Just to be sure, $T$ was always a lifetime in the text above. The half-life is simply $\ln(2) T$, about 69 percent of the lifetime, because of some simple maths (switching from the base $e$ to the base $2$ and vice versa).
If we observe $\Delta N$ decays, the typical relative statistical error of the number of decays is proportional to $1/(\Delta N)^{1/2}$. So if you want the accuracy "1 part in 1 thousand", you need to observe at least 1 million decays, and so on.
The following is multiple choice question (with options) to answer.
What is quantified by measuring the number of decay processes per unit time? | [
"fossil age",
"radioactivity",
"microwave power",
"temperature"
] | B | Radioactivity is quantified by measuring the number of decay processes per unit time. For example, we can measure radioactivity in terms of counts per minute (cpm), where each "count" is a single decay process, such as the emission of an α-particle. A sample of one particular isotope may have an activity of 5,000 cpm, while an equal amount of another isotope might result in a radiation level of only 250 cpm. For a given nucleus, the amount of radioactivity gives a rough indication of the amount of the radioisotope present – the higher the activity, the more of the radioactive isotope in the sample. |
SciQ | SciQ-6887 | forces, drag
// PHASE 1 - GRAVITY FOR THIS OBJECT
position = 0, 0, 0
mass = 1
gravity = 9.80665
fGrav = mass * gravity
The following is multiple choice question (with options) to answer.
What is a measure of the force of gravity pulling on an object of a given mass? | [
"solidity",
"effect",
"scale",
"weight"
] | D | Newton’s second law of motion explains the weight of objects. Weight is a measure of the force of gravity pulling on an object of a given mass. It’s the force (F) in the acceleration equation that was introduced above:. |
SciQ | SciQ-6888 | atoms, terminology
Title: What is a neutral atom? I was told that an atom's atomic number is defined as follows:
The number of electrons or protons present in a neutral atom is called atomic number. It is represented by Z.
What does neutral mean here? Why isn't it just "..present in an atom..."? Electrons and protons are charged particles. The electrons have negative charge, while protons have positive charge. A neutral atom is an atom where the charges of the electrons and the protons balance. Luckily, one electron has the same charge (with opposite sign) as a proton.
Example: Carbon has 6 protons. The neutral Carbon atom has 6 electrons. The atomic number is 6 since there are 6 protons.
The following is multiple choice question (with options) to answer.
What is the atomic number? | [
"Number of electrons",
"number of protons",
"Number of neutrons",
"Speed of electrons"
] | B | In the modern periodic table, elements are organized by atomic number. The atomic number is the number of protons in an atom of an element. This number is unique for each element, so it seems like an obvious way to organize the elements. (Mendeleev used atomic mass instead of atomic number because protons had not yet been discovered when he made his table. ) In the modern table, atomic number increases from left to right across each period. It also increases from top to bottom within each group. How is this like Mendeleev’s table?. |
SciQ | SciQ-6889 | elements, radioactivity
Title: Why radioactive elements emit alpha beta and gamma rays I am confused about this that why radioactive elements emits alpha beta and gamma rays WHILE other elements can't do so. The stability of nuclei is really a sophisticated topic in theoretical quantum mechanics. But there is a simple way to think about what is happening that doesn't get too intense with the quantum mechanical theory.
Nuclei are made from two particles: protons and neutrons. But protons are positively charged and repel each other. The electromagnetic force is very strong and therefore this force is very large. So the first mystery is why all nuclei don't just fly apart.
The reason they don't is that there are two very short-range but very strong forces that bind the nucleus together: the strong and weak nuclear forces. Without getting into mind-bending topics in theoretical physics we can understand something about their net effect like this.
The interaction of the electromagnetic force and the two nuclear forces has some structure (it's quantum stuff, just accept it). Some combinations of protons and neutrons are more stable than others. Each combination has an energy level and some combinations have lower energy than others. Nuclei with even numbers of protons and neutrons are more stable than odd-odd combinations and nuclei with wildly unbalanced neutron to proton ratios are less stable. Neutrons act a little like a glue, helping protons stick together (this is an oversimplification as too many neutrons is also a source of instability: this is a consequence of a complicated interplay of several forces). But bigger nuclei are less stable and need a higher ratio of neutrons. And some large nuclei are just too large for the forces to keep them together so beyond a certain point all nuclei are unstable.
Some nuclei can be transformed into a more stable (lower energy) nucleus by various forms of radioactive decay. Nuclei with too many neutrons can emit a beta particle (this decay mode converts a neutron into a proton); elements with too many protons can emit a positron (converting a proton into a neutron). Bigger nuclei can become more stable by kicking out an alpha particle (which makes the nucleus significantly smaller, moving it towards the stable zone). Gamma radiation is associated with some of these modes: the high energy photons "mop up" the excess energy (I'm simplifying a lot).
The following is multiple choice question (with options) to answer.
Some isotopes are stable indefinitely, while others are radioactive and do what through a characteristic form of emission? | [
"replicate",
"expand",
"bond",
"decay"
] | D | Whether or not a given isotope is radioactive is a characteristic of that particular isotope. Some isotopes are stable indefinitely, while others are radioactive and decay through a characteristic form of emission. As time passes, less and less of the radioactive isotope will be present, and the level of radioactivity decreases. An interesting and useful aspect of radioactive decay is half-life, which is the amount of time it takes for one-half of a radioactive isotope to decay. The half-life of a specific radioactive isotope is constant; it is unaffected by conditions and is independent of the initial amount of that isotope. Consider the following example. Suppose we have 100.0 g of tritium (a radioactive isotope of hydrogen). It has a half-life of 12.3 y. After 12.3 y, half of the sample will have decayed from hydrogen-3 to helium-3 by emitting a beta particle, so that only 50.0 g of the original tritium remains. After another 12.3 y— making a total of 24.6 y—another half of the remaining tritium will have decayed, leaving 25.0 g of tritium. After another 12.3 y—now a total of 36.9 y—another half of the remaining tritium will have decayed, leaving 12.5 g. This sequence of events is illustrated in Figure 15.1 "Radioactive Decay". Figure 15.1 Radioactive Decay. |
SciQ | SciQ-6890 | 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.
Cellular respiration uses oxygen to harvest what from organic molecules? | [
"chlorophyll",
"light",
"energy",
"water"
] | C | the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules. |
SciQ | SciQ-6891 | 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.
A red blood cell will swell and burst when placed in a? | [
"hypotonic solution",
"dissolved solution",
"exothermic solution",
"acidic solution"
] | A | A cell that does not have a rigid cell wall, such as a red blood cell, will swell and lyse (burst) when placed in a hypotonic solution. Cells with a cell wall will swell when placed in a hypotonic solution, but once the cell is turgid (firm), the tough cell wall prevents any more water from entering the cell. When placed in a hypertonic solution, a cell without a cell wall will lose water to the environment, shrivel, and probably die. In a hypertonic solution, a cell with a cell wall will lose water too. The plasma membrane pulls away from the cell wall as it shrivels, a process called plasmolysis . Animal cells tend to do best in an isotonic environment, plant cells tend to do best in a hypotonic environment. This is demonstrated in Figure below . |
SciQ | SciQ-6892 | geology, volcanology, geochemistry, petrology, magmatism
I'm not exactly sure what do you mean by 'mature' but I will address the timing of alkali magmatic activity. Here is a very simplified depiction of what happens:
At first (A), a young plume will still be deep. The melts that it forms are low degree and deep. Then, when the plume 'matures' (B), it causes shallow melting producing voluminous tholeiitic basalts. The margins of the plumes still produce low degrees alkali melts. When the plume wanes (or just migrates somewhere else), you get only alkali melts again (sorry, I was too lazy to draw C in the figure, but it should look not too different than A). This is similar to what's happening at the moment in Hawaii. The newest (still underwater) volcano, Loihi, erupts alkali magmas. This corresponds to stage A in the figure. This is also what the oldest rock on Hawaii (the island) are made of: alkali rocks. Most of the rocks by volume on Hawaii (again, the island) are tholeiitic basalts erupted some hundred thousands year ago, corresponding to stage B in the figure. Recent (geologically) eruptions are yet again alkaline, similar to stage C.
For some extra reading about alkali rocks and related subjects, see these other questions and answers:
What are the high field strength and large ion lithophile (HFS or HFSE & LIL or LILE) elements?
What are rare earths and why do they cluster near alkaline magmatism?
Are there significant amounts of rare earth elements on Iceland?
The following is multiple choice question (with options) to answer.
Which type of lava lavas are less viscous and erupt effusively? | [
"Intermediate lava",
"mafic",
"Ultramafic lava",
"Felsic lava"
] | B | Felsic lavas are more viscous and erupt explosively or do not erupt. Mafic lavas are less viscous and erupt effusively. |
SciQ | SciQ-6893 | biochemistry, cell-biology, proteins
Title: Why is protein turnover necessary or important for cells to function? Cells constantly create new proteins in order to maintain their normal function, this is called protein turnover.
Why is that? Do the old molecules wear out as time passes, so that they need a replacement? Biology is an intricate orchestration of chemical reactions and their products. Generally, this fete is accomplished by enzymatic facilitation of certain reactions that would otherwise occur too slowly.
However, "unwanted" reactions occur spontaneously all the time, too. One important mechanism for these reactions is the presence of free radicals causing oxidative stress: reactive molecules are present in cells as a consequence of the energy necessary for metabolism, and these can react with proteins and other cellular components and change their structure. Modified proteins may fold incorrectly and lose their function (or gain harmful function). There is very little that can be done to prevent these reactions from occurring except to clean up afterwards.
Half-lives vary by protein, but for most proteins are measured in the scale of hours (Chen et al, 2016) to a couple days (Boisvert et al, 2012). By constantly degrading and replacing proteins, cells ensure that their proteins are functional and fresh. You might consider this as analogous to performing regular maintenance on a machine like an automobile, using replacement parts as the originals become worn.
Both protein degradation (e.g., via the ubiquitin-proteasome system) and synthesis are highly regulated.
Boisvert, F. M., Ahmad, Y., Gierliński, M., Charrière, F., Lamont, D., Scott, M., ... & Lamond, A. I. (2012). A quantitative spatial proteomics analysis of proteome turnover in human cells. Molecular & Cellular Proteomics, 11(3).
Chen, W., Smeekens, J. M., & Wu, R. (2016). Systematic study of the dynamics and half-lives of newly synthesized proteins in human cells. Chemical science, 7(2), 1393-1400.
The following is multiple choice question (with options) to answer.
What are often formed biologically during the breakdown of proteins in animal cells, having the smell of death and decay?. | [
"ketones",
"amines",
"acids",
"enzymes"
] | B | Amines generally have rather pungent or noxious odors. Ammonia can be considered the simplest amine and has a very distinctive odor. Methylamine has an unpleasant odor associated with dead fish. Amines are often formed biologically during the breakdown of proteins in animal cells, and so many have the smell of death and decay. Putrescine and cadaverine are two such amines and are aptly named for their foul odors. The toxins which many animals use as a form of defense are frequently amines. Amines are used industrially as dyes and in many drugs. |
SciQ | SciQ-6894 | newtonian-mechanics, forces, newtonian-gravity, centripetal-force, free-body-diagram
Again, the same big difference in effect.
Regarding the centripetal force, it is still the same force. Gravity provides a centripetal force which is what keeps Earth in orbit.
Note
It's worth pointing out that the mass that acts as the charge for gravity, known as gravitational mass is not, a priori, the same mass that appears in Newtons's law, known as inertial mass. On the other hand it is a fact of nature that they have the same value, and as such we may use a single symbol $m$, instead of two, $m_i$ and $m_g$. This is an underlying, unspoken assumption in the derivation above. This is known as the weak equivalence principle.
The following is multiple choice question (with options) to answer.
What produces the centripetal force to keep the earth orbiting the sun? | [
"heat",
"weight",
"gravity",
"motion"
] | C | Centripetal force is, simply, the force that causes centripetal acceleration. Objects that move in uniform circular motion all have an acceleration toward the center of the circle and therefore, they must also suffer a force toward the center of the circle. That force is the centripetal force. For orbiting satellites, such as the moon orbiting the earth or the earth orbiting the sun, the centripetal force is produced by gravity. When an Olympic hammer thrower whirls a massive ball on a chain, the centripetal force is created by the athlete and transmitted by the chain. |
SciQ | SciQ-6895 | periodic-trends, periodic-table
Title: How long the block starting with element 121 will be? I remember from my chemistry classes that (after the initial irregularities) a new block of elements starts every two periods. After the initial s-block and p-block following it shortly, we have d-block starting at period IV, and f-block starting at period VI.
Now that Element 118 has been discovered, we're about to open period VIII and we're two elements short of a new block.
What block will it be? How many groups, what name etc? As you noted, this is a very appropriate question in light of the IUPAC announcement that we have just finished filling Period 7!
The names of the subshells s, p, d, and f are named after the old spectroscopic terms sharp, principal, diffuse, and fundamental. We ran out of fancy names after that, so the subsequent subshells are named in alphabetical order - g, h, and so on - which means that after the 8s block is filled, we would theoretically have a 5g block.
The orbitals in the g subshell would be labelled with the quantum number $l = 4$, so $m_l$ would take integer values between $-4$ and $4$ (inclusive) giving a total of nine g-orbitals. Each g-orbital could hold two electrons with opposite spins, so the g-block would have $18$ electrons.
However, it is worth noting that the electronic configurations may or may not obey the aufbau principle fully. Whether the 5g orbitals will actually be filled or not will certainly not be easy to determine, considering how short the half-lives of those elements are likely to be.
Wikipedia has an article which talks about it.
The following is multiple choice question (with options) to answer.
Group 13 of the periodic table is also called what? | [
"iron group",
"nitrogen group",
"the boron group",
"manganese group"
] | C | Group 13 of the periodic table is also called the boron group because boron (B) is the first element at the top of the group (see Figure below ). Boron is also the only metalloid in this group. The other four elements in the group—aluminum (Al), gallium (Ga), indium (In), and thallium (Tl)—are all metals. Group 13 elements have three valence electrons and are fairly reactive. All of them are solids at room temperature. |
SciQ | SciQ-6896 | homework, plant-physiology, plant-anatomy
and 'Vascular Plants = Winning! - Crash Course Biology #37'
https://youtu.be/h9oDTMXM7M8?t=373
[5] Osmosis (water compensating solutes) "In Da Club - Membranes & Transport: Crash Course Biology #5"
https://youtu.be/dPKvHrD1eS4?list=PL3EED4C1D684D3ADF&t=148
Ian (and dad <= all errors and approximations are his :) ).
The following is multiple choice question (with options) to answer.
What type of tissue transports water and minerals in a vascular plant? | [
"capillaries",
"xylem",
"collagen",
"chlorophyll"
] | B | 25.4 Seedless Vascular Plants Vascular systems consist of xylem tissue, which transports water and minerals, and phloem tissue, which transports sugars and proteins. With the development of the vascular system, there appeared leaves to act as large photosynthetic organs, and roots to access water from the ground. Small uncomplicated leaves are microphylls. Large leaves with vein patterns are megaphylls. Modified leaves that bear sporangia are sporophylls. Some sporophylls are arranged in cone structures called strobili. |
SciQ | SciQ-6897 | human-biology, food
Title: Can humans eat grass? Can a human eat grass and digest it?
Could it be possible to use it as food just like other plants such as wheat or beans? To elaborate on A random zoologist's answer, the problem is that the human digestive system does not contain any cellulase enzymes. Cellulases are a class of enzymes that break down cellulose, the chief structural component of plants. You might be able to obtain a small amount of nutrition from grass or other cellulose-rich materials, but as the plant cell walls are made of cellulose, most of the plant material will be indigestible.
The following is multiple choice question (with options) to answer.
What produces enzymes that digest carbohydrates in plant cell walls? | [
"bacteria",
"algae",
"pollen",
"protists"
] | A | Break down some substances in food that cannot be digested, such as fiber and some starches and sugars. Bacteria produce enzymes that digest carbohydrates in plant cell walls. Most of the nutritional value of plant material would be wasted without these bacteria. These help us digest plant foods like spinach. |
SciQ | SciQ-6898 | thermodynamics, phase-transition, states-of-matter
So in theory, you can have 100% ice that is at melting temperature. If you apply exactly the energy required for that amount of ice to transition to water, then you would have 100% water that is at the exact same temperature. If instead you only applied 50% of the energy required to melt that quantity of ice, then you would have a mixture of 50% ice and 50% water, still at the same temperature. (Of course in reality the temperature will not be perfectly even; you're much more likely to have ice at a range of temperatures from just below up to the melting point and water at a range of temperatures from the melting point to a bit above)
So there's a clear boundary in that each given "bit" of H2O is either water or ice, there's no state that is "in between ice and water" that is passed through on the way to melting the ice. The halfway point to melting a block of ice does not have all of the ice with "partially weakened bonds", or anything like that. But the transition of a large chunk of ice into water is a gradual process, not something that happens at a clear instant - more of the ice gradually undergoes the (sharp) transition to water as more energy is gradually added.
The following is multiple choice question (with options) to answer.
At what temperature does solid water melt to a liquid? | [
"below 0 degrees c",
"at temperatures above 0 degrees c",
"above 32 degrees c",
"below 32 degrees c"
] | B | The process in which rocks or other solids change to liquids is called melting. Melting occurs when particles of a solid absorb enough energy to partly overcome the force of attraction holding them together. This allows them to move out of their fixed positions and slip over one another. Melting, like other changes of state, is a physical change in matter, so it doesn’t change the chemical makeup or chemical properties of matter. |
SciQ | SciQ-6899 | 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.
How many more legs do spiders have compared to insects? | [
"six",
"four",
"one",
"two"
] | D | Although spiders and insects are both arthropods, a spider is not an insect. One key difference is that insects have six legs, while spiders have eight legs. |
SciQ | SciQ-6900 | geothermal-heat
Title: What Keeps the Earth Cooking? If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat?
If radioactive decay supplies only about half the Earth’s heat, what are the remaining sources of heat?
Mostly it is residual heat energy from when the Earth was very young. The biggest source came from the kinetic energy of all the bodies, big and small, that collided to form the Earth being converted to heat. The differentiation of the Earth added even more heat energy to the Earth.
In addition to radioactive decay, the on-going freezing of the outer core material onto to the inner core adds a bit more heat to the system, but neither one compensates for heat transported through the mantle and crust and then out into space. Note that this heating from below is but a tiny portion of the overall energy budget for the Earth's surface.
Even the Earth's surface was very hot shortly after the formation and differentiation of the Earth. While the surface cooled quickly (geologically speaking), the interior has not. The key reason is that 2,890 km of rock makes for a fairly thick blanket.
The following is multiple choice question (with options) to answer.
Almost all energy at earth's surface comes from where? | [
"another sun",
"the sun",
"oceans",
"wind"
] | B | Almost all energy at Earth's surface comes from the Sun. The Sun’s energy heats the planet and the air around it. This causes the atmosphere to move and create weather. Sunlight also powers photosynthesis and life on Earth. |
SciQ | SciQ-6901 | molecular-biology, dna, molecular-genetics
Additionally, there's regulation of protein biosynthesis at the ribosome, which often complexes with other molecules in complicated ways to ensure an additional layer of tuning of how much protein is produced, and how quickly.
There are many, many other known levels of regulation. There also remain many unknown mechanisms of regulation, which scientists are busy with uncovering and understanding as we speak.
EDIT: What dictates which protein to synthesize at a given time? The history and present identity of a cell. By identity, I mean its state regarding regulation of its own gene expression, as well as other things.
The following is multiple choice question (with options) to answer.
What is the first step in protein synthesis? | [
"mutation",
"reproduction",
"differentiation",
"transcription"
] | D | Transcription is the first step in protein synthesis. It takes place in the nucleus. During transcription, a strand of DNA is copied to make a strand of mRNA. How does this happen? It occurs by the following steps, as shown in Figure below . |
SciQ | SciQ-6902 | transcription, translation
Ralston, A. (2008) Operons and prokaryotic gene regulation. Nature Education
From Genes to Genomes: Concepts and Applications of DNA Technology
Molecular cell biology
Analysis of Genes and Genomes
The following is multiple choice question (with options) to answer.
What branch of biology focuses on heredity? | [
"semiotics",
"Epidemiology",
"genetics",
"ontology"
] | C | Genetics is the branch of biology that focuses on heredity. The basics of heredity are similar for all organisms that reproduce sexually: the offspring receive one set of genetic material from one parent and the other set from the other parent. But are there aspects of genetics that are specific for humans? Let’s find out. |
SciQ | SciQ-6903 | star-formation, nebulae
What's the explanation? A pointer to a good article for the knowledgeable lay person would be helpful too. Your option #3 is correct; the shape has little to do with the relative motion of the gas and stars.
Giant molecular clouds
The pillars are part of the giant molecular cloud (GMC) which is giving birth to news stars. Stars are formed when some regions inside the cloud meet the Jeans criterion, i.e. are sufficiently dense and cold that gravity overcomes pressure. Because the density of such clouds is largest in the center (see e.g. Chen et al. 2021), stars will tend to form first in the center.
Stars are formed with a distribution of masses. The most massive ones — the so-called O and B stars — emit copious amounts of ultraviolet photons, which heat and ionize the surrounding medium. A hot, ionized bubble inside the otherwise cold, neutral, and dusty cloud called a Strömgren sphere then forms.
The dark pillars are remainders of the neutral gas, whereas the bluish region is the ionized region, containing newborn stars.
The size of the ionized region
In this answer about the Carina Nebula, I calculated the typical size of a Strömgren sphere, which we can write approximately as
$$
R_\mathrm{S} \simeq 10\,\mathrm{lightyears} \times\color{red}{\left(\frac{Q(\mathrm{H}^0)}{10^{50}\,\mathrm{s}^{-1}}\right)^{1/3}}
\color{blue}{\left(\frac{n_\mathrm{H}}{300\,\mathrm{cm}^{-3}}\right)^{-2/3}}
\color{green}{\left(\frac{T}{10^4\,\mathrm{K}}\right)^{0.23}},
$$
The following is multiple choice question (with options) to answer.
Stars are born in clouds, and they form and grow dense due to what force? | [
"Big Bang theory",
"gravity",
"coreolis effect",
"kinetic energy"
] | B | Stars are born in clouds like the one in the picture. Gravity pulls material together. When it is extremely dense, it begins nuclear fusion. That is, it becomes a star. We can see places where stars are being born right now. Of course, it takes light a long time to travel to us. So what we see right now may have happened many millions or even billions of years ago. |
SciQ | SciQ-6904 | 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.
What has atoms with unstable nuclei? | [
"radionuclide",
"radioisotope",
"hydrocarbon",
"microwaves"
] | B | A radioisotope has atoms with unstable nuclei. Unstable nuclei naturally decay, or break down. They lose energy and particles and become more stable. As nuclei decay, they gain or lose protons, so the atoms become different elements. This is illustrated in the Figure below . The original, unstable nucleus is called the parent nucleus. After it loses a particle (in this case a type of particle called an alpha particle), it forms a daughter nucleus, with a different number of protons. |
SciQ | SciQ-6905 | 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 the tissue beneath a mollusks' shell called? | [
"mucous",
"mantle",
"cartilage",
"skin"
] | B | Mollusks have ventral nerve cords. The tissue beneath the shell is called the mantle. The mantle cavity contains hemolymph. Figure 15.33 Which of the following statements about common features of chordates is true? a. The dorsal hollow nerve cord is part of the chordate central nervous system. In vertebrate fishes, the pharyngeal slits become the gills. Humans are not chordates because humans do not have a tail. Vertebrates do not have a notochord at any point in their development; instead, they have a vertebral column. |
SciQ | SciQ-6906 | organic-chemistry
Title: Why does enantiopure sec-butyl alcohol retain its optical activity over aqueous base but forms a racemic mixture over dilute sulphuric acid? Why does enantiopure sec-butyl alcohol retain its optical activity over aqueous base but forms a racemic mixture over dilute sulphuric acid ?
My reasoning is that, sec-butyl alcohol get dehydrated into a alkene because of sulphuric acid and then get hydrolysed to form alcohol again. Thus a equilibrium is formed between alkene and alcohol and between $R-$ and $S-$ sec butyl alcohol.
Dehydration cannot occur with a base, so the alcohol remains optically active.
I feel that conversion of alcohol to alkene and then back to alcohol seems ridiculous and impossible. What do you think, is this reasoning correct or just plain non-sense ?
To be specific, I have some doubt whether alkene will convert back to alcohol or not in dil sulphuric acidic ? Although sulphuric acid is a notable dehydrating agent, it is concentrated rather than dilute sulphuric acid that would be typically used for such a purpose.
Here, it is due to the improvement of $\ce{H2O}$ as a leaving group compared to $\ce{OH-}$, due to the lack of any charge as a leaving group.
Under acidic conditions, the sec-butyl alcohol will be protonated in a small amount creating a much better leaving group. The protonation also makes the alcoholic carbon centre more electrophilic and vulnerable to $S_N2$ attack by other water molecules in solution, leading to inversion of the chiral centre.
This in not possible under neutral conditions as the unprotonated alcohol would have $\ce{OH-}$ as a much poorer leaving group, preventing elimination or substitution reactions.
Under acidic conditions, with neutral water as a nucleophile $S_N2$ substition will be the preferred path.
The following is multiple choice question (with options) to answer.
What is formed from an alcohol that loses water? | [
"alcohols",
"Bonds",
"alkenes",
"amines"
] | C | Alcohols can lose water to form alkenes. |
SciQ | SciQ-6907 | 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.
What is the division of the body into multiple parts called? | [
"compression",
"organ-level organization",
"segmentation",
"transverse"
] | C | Segmentation evolved next. This is a division of the body into multiple segments. Both the earthworm and ant pictured in Figure below have segmented bodies. This trait increases flexibility. It permits a wider range of motion. All annelids and arthropods are segmented. Arthropods also evolved jointed appendages. For example, they evolved jointed legs for walking and “feelers” (antennae) for sensing. |
SciQ | SciQ-6908 | genetics, reproduction, pregnancy
Title: Oocyte cryopreservation: genes from three parents? Recently, I've heard of something called Oocyte cryopreservation, where a (fertilized, I think) egg from a woman is extracted, frozen and later thawed and reinserted into the woman to delay pregnancy.
Now, this is just an idea, I don't know if this is actually possible, but can this frozen egg be implanted into a different woman, who isn't the original owner of the egg? If yes, whose genes would the child inherit? Would it get genes from all three parents, or just from the original owner of the sperm and egg? In short: yes it is possible to donate an oocyte to another woman. This is typically done in assisted reproduction and combined with in vitro fertilization. The child would only inherit the genes from the donor oocyte and the sperm, as the genetic material is enclosed in the oocyte and sperm. There is no genetic contribution of the recipient.
You can find more information on the corresponding wikipedia page:
Egg donation
The following is multiple choice question (with options) to answer.
What reproductive method has two parents involved? | [
"mitosis",
"pollination",
"budding",
"sexually"
] | D | Most reptiles reproduce sexually, meaning there are two parents involved. In some families of lizards and one snake family, however, asexual reproduction is possible. This is when only one parent is involved in creating new life. For example, the gecko females can make tiny clones of themselves without the aid of a male. |
SciQ | SciQ-6909 | purification, alkali-metals
This could perhaps be increased if you left the metal for a while in the ammonia or if the pressure or temperature is increased.
Our setup works by cooling down the vessel to - 80°C so the ammonia will liquify. And then immediately pour it off to save time. So there isn't much time for the metals to dissolve and the pressure is then often at around 350 - 400 mbars.
But as I said this is just from my experience, a specially designed setup may work in your case.
The following is multiple choice question (with options) to answer.
In many cases, the alkali metal amide salt (mnh2) is not very soluble in liquid ammonia and does what? | [
"evaporates",
"precipitates",
"isolates",
"settles"
] | B | where the (am) designation refers to an ammonia solution, analogous to (aq) used to indicate aqueous solutions. Without a catalyst, the reaction in Equation 21.20 tends to be rather slow. In many cases, the alkali metal amide salt (MNH2) is not very soluble in liquid ammonia and precipitates, but when dissolved, very concentrated solutions of the alkali metal are produced. One mole of Cs metal, for example, will dissolve in as little as 53 mL (40 g) of liquid ammonia. The pure metal is easily recovered when the ammonia evaporates. Solutions of alkali metals in liquid ammonia are intensely colored and good conductors of electricity due to the presence of solvated electrons (e−, NH3), which are not attached to single atoms. A solvated electron is loosely associated with a cavity in the ammonia solvent that is stabilized by hydrogen bonds. Alkali metal–liquid ammonia solutions of about 3 M or less are deep blue (Figure 21.11 "Alkali Metal–Liquid Ammonia Solutions") and conduct electricity about 10 times better than an aqueous NaCl solution because of the high mobility of the solvated electrons. As the concentration of the metal increases above 3 M, the color changes to metallic bronze or gold, and the conductivity increases to a value comparable with that of the pure liquid metals. |
SciQ | SciQ-6910 | nuclear-physics, radioactivity
Title: Carbon-14 formation in atmosphere Wikipedia says Carbon-14 is formed in the atmosphere by the reaction:
1n + 14N → 14C + 1p
This looks like neutron capture. However, I would expect neutron capture to result in 15N. However, "proton emission" seems to be a rare phenomenon:
15N → 14C + 1p
So, my first question is, does the reaction happen in two stages, or is the proton ejected "immediately"?
Secondly, is this overall type of reaction 1n + → + 1p common? Are there any other examples of such reactions, other than with 14N? It is a prompt (immediate) reaction, and is more usually written something like N14(n,p)C14 to indicate that. It is far from the only such reaction.
EDIT - To quantify my statement that there are many similar reactions, I went to the Evaluated Nuclear Data Files site hosted at Brookhaven (ENDF), entered 'n,p' for the reaction, 'sig' for the desired quantity (sig = sigma = cross-section in barns for the reaction). This returned 308 separate data sets, from He3(n,p)H3 to Bi209(n,p)Pb209. So, indeed, the existence of the N14(n,p)C14 reaction is no great surprise.
The following is multiple choice question (with options) to answer.
An example of beta decay is the emission of an electron by a carbon-14 what? | [
"nucleus",
"protons",
"molecules",
"ion"
] | A | Transmutation also occurs when a nucleus undergoes decay. An example of beta decay is the emission of an electron by a carbon-14 nucleus. |
SciQ | SciQ-6911 | quantum-mechanics, electromagnetism, electrons, molecules
When talking about a molecule the concept of a single atom is not valid with respect to electron distribution.
You need to distinguish between the (notional) position of the atom defined by the mass of the atom, made up almost entirely of a quite localized nucleus and the atom as a nucleus with electrons around it, where the electron cloud cannot be as well localized.
Thus you can identify an atom in a molecule in the sense of a well defined nuclear center with an associated nucleus and position, but it is not at all as simple to define the distribution of the electrons associated with each atom. As electrons cannot be distinguished it makes no sense to talk about an electrically neutral atom in a molecule. Only the overall neutrality of the molecule is meaningful.
does the repulsion inside the molecule between the individual atoms come from part PEP and part EM repulsion or just PEP?
When constructing a wafefunction for electrons in an atom or molecule you would use a form that allows for the PEP to be "embedded" in the structure of wavefunction. See for example this Wikipedia page on the Slater determinant.
So we don't explicitly have a force as a result of the PEP, but in order to satisfy the mathematical requirements PEP imposes on the wavefunction, the effect of PEP on energy levels falls out of solving the equations with these "emebedded" structures.
Typically we cannot analytically calculate wavefunctions like these and rely on numerical methods instead. Calculating the effect of PEP is therefore not practical. To do so would require calculating using an entirely different wavefunction structure which does not incorporate PEP principles, but you could not meaningfully relate the two sets of results. I not sure you could even say that the PEP is always repulsive in effect in a molecule.
So the results depends on the effects of electrical attraction (between electrons of nuclei), electrical repulsion (between electrons) and the effects of the PEP via the mathematical requirements for the structure of the wavefunction.
The following is multiple choice question (with options) to answer.
Which theory describes the distribution of electrons in molecules in much the same way that the distribution of electrons in atoms is described using atomic orbitals? | [
"molecular distribution theory",
"atomic distribution theory",
"atomic orbital theory",
"molecular orbital theory"
] | D | Molecular orbital theory describes the distribution of electrons in molecules in much the same way that the distribution of electrons in atoms is described using atomic orbitals. Using quantum mechanics, the behavior of an electron in a molecule is still described by a wave function, Ψ, analogous to the behavior in an atom. Just like electrons around isolated atoms, electrons around atoms in molecules are limited to discrete (quantized) energies. The region of space in which a valence electron in a molecule is likely to be found is called a molecular orbital (Ψ2). Like an atomic orbital, a molecular orbital is full when it contains two electrons with opposite spin. We will consider the molecular orbitals in molecules composed of two identical atoms (H2 or Cl2, for example). Such molecules are called homonuclear diatomic molecules. In these diatomic molecules, several types of molecular orbitals occur. The mathematical process of combining atomic orbitals to generate molecular orbitals is called the linear combination of atomic orbitals (LCAO). The wave function describes the wavelike properties of an electron. Molecular orbitals are combinations of atomic orbital wave functions. Combining waves can lead to constructive interference, in which peaks line up with peaks, or destructive interference, in which peaks line up with troughs. |
SciQ | SciQ-6912 | endocrinology, pathology, experimental, diabetes-mellitus
Title: Growth Hormone and diabetes Growth hormone and insulin like growth factors are diabetogenic, so I assume that people with high growth hormone (say due to pituitary tumor) may be at high risk for diabetes. Has any correlation been established between these two? I know that diabetes is a multifactorial disorder and so only a correlation may be established. Yes:
That GH has an effect on glycaemic control is most evident from the abnormal glucose tolerance seen in acromegalics...
acromegaly is defined as abnormal growth of the hands, feet, and face, caused by overproduction of growth hormone by the pituitary gland.
Such an effect has been known for decades, which makes sense given how interrelated the axes are. Although I think the best evidence is the fact that the side effects of growth hormone therapy says that Some patients have developed diabetes mellitus...
The following is multiple choice question (with options) to answer.
Oversecretion of insulin can cause what? | [
"inflammation",
"hypoxia",
"hyperglycemia",
"hypoglycemia"
] | D | This animation (http://openstaxcollege. org/l/insulin) describe the role of insulin and the pancreas in diabetes. Impaired insulin function can lead to a condition called diabetes mellitus, the main symptoms of which are illustrated in Figure 37.10. This can be caused by low levels of insulin production by the beta cells of the pancreas, or by reduced sensitivity of tissue cells to insulin. This prevents glucose from being absorbed by cells, causing high levels of blood glucose, or hyperglycemia (high sugar). High blood glucose levels make it difficult for the kidneys to recover all the glucose from nascent urine, resulting in glucose being lost in urine. High glucose levels also result in less water being reabsorbed by the kidneys, causing high amounts of urine to be produced; this may result in dehydration. Over time, high blood glucose levels can cause nerve damage to the eyes and peripheral body tissues, as well as damage to the kidneys and cardiovascular system. Oversecretion of insulin can cause hypoglycemia, low blood glucose levels. This causes insufficient glucose availability to cells, often leading to muscle weakness, and can sometimes cause unconsciousness or death if left untreated. |
SciQ | SciQ-6913 | homework, ecology, population-biology, conservation-biology
Title: Difference between biological control and introducing species for conservation? I have a biology assignment and we have to explain various methods and strategies for conservation, two of which are:
Biological control
Introduced Species
What is the difference between these? I was under the impression that they are essentially the same thing – biological control being the introduction of species to predate pests (eg. the abysmal failure of the cane toad).
Any clarification would be great. After talking to my teacher, he said that biological control is the introduction of species to control another species, however species may be introduced for other reasons (the "Introduced Species" method), such as to "assist an ecosystem cope, flourish or re-establish itself."
The example he gave was the introduction of South African veldt grass to Western Australia in order to stabilise sand dunes, so that they can later be built upon further (eg. plants which may not perform well in sandy, unstable soil can then be planted).
Hopefully this helps anyone else with the same problem.
The following is multiple choice question (with options) to answer.
The first few species to colonize a disturbed area are called what? | [
"producer species",
"pioneer species",
"colonization species",
"original species"
] | B | The first few species to colonize a disturbed area are called pioneer species. In primary succession, pioneer species must be organisms that can live on bare rock. They usually include bacteria and lichens (see Figure below ). Along with wind and water, the pioneer species help weather the rock and form soil. Once soil begins to form, plants can move in. The first plants are usually grasses and other small plants that can grow in thin, poor soil. As more plants grow and die, organic matter is added to the soil. This improves the soil and helps it hold water. The improved soil allows shrubs and trees to move into the area. |
SciQ | SciQ-6914 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
What are the two loops of blood flow in the cardiovascular system? | [
"aerobic and anaerobic",
"anabolic and metabolic",
"pulmonary and systemic",
"systolic and diastolic"
] | C | The cardiovascular system circulates blood through two different loops. Pulmonary circulation is a loop that carries blood between the heart and lungs. Systemic circulation is a loop that carries blood between the heart and the rest of the body. |
SciQ | SciQ-6915 | molecular-biology, molecular-genetics, gene-expression, cytogenetics
Edit - response to comments:
Plug, I et al. (2006) Bleeding in carriers of hemophilia. Blood 108: 52-56
Abstract:
A wide range of factor VIII and IX levels is observed in heterozygous carriers of hemophilia as well as in noncarriers. In female carriers, extreme lyonization may lead to low clotting factor levels. We studied the effect of heterozygous hemophilia carriership on the occurrence of bleeding symptoms. A postal survey was performed among most of the women who were tested for carriership of hemophilia in the Netherlands before 2001. The questionnaire included items on personal characteristics, characteristics of hemophilia in the affected family members, and carrier testing and history of bleeding problems such as bleeding after tooth extraction, bleeding after tonsillectomy, and other operations. Information on clotting factor levels was obtained from the hospital charts. Logistic regression was used to assess the relation of carrier status and clotting factor levels with the occurrence of hemorrhagic events. In 2004, 766 questionnaires were sent, and 546 women responded (80%). Of these, 274 were carriers of hemophilia A or B. The median clotting factor level of carriers was 0.60 IU/mL (range, 0.05-2.19 IU/mL) compared with 1.02 IU/mL (range, 0.45-3.28 IU/mL) in noncarriers. Clotting factor levels from 0.60 to 0.05 IU/mL were increasingly associated with prolonged bleeding from small wounds and prolonged bleeding after tooth extraction, tonsillectomy, and operations. Carriers of hemophilia bleed more than other women, especially after medical interventions. Our findings suggest that not only clotting factor levels at the extreme of the distribution, resembling mild hemophilia, but also mildly reduced clotting factor levels between 0.41 and 0.60 IU/mL are associated with bleeding.
Bimler, D & Kirkland, J (2009) Colour-space distortion in women who are heterozygous for colour deficiency. Vision Research 49: 536-543
from the Introduction:
The following is multiple choice question (with options) to answer.
What is the name of a group of hereditary diseases that affect the body's ability to control blood clotting? | [
"anemia",
"hemophilia",
"arithmya",
"hypertension"
] | B | Hemophilia is the name of a group of hereditary diseases that affect the body's ability to control blood clotting. Hemophilia is caused by a lack of clotting factors in the blood. Clotting factors are normally released by platelets. Since people with hemophilia cannot produce clots, any cut can put a person at risk of bleeding to death. The risk of internal bleeding is also increased in hemophilia, especially into muscles and joints. This disease affected the royal families of Europe. |
SciQ | SciQ-6916 | zoology, terminology, nomenclature, invertebrates, etymology
Urochorda
Cephalochorda
Craniata
which is more or less the accepted division today, with Urochorda being called Urochordata now.
In this essay, Lankester says:
The evidence of degeneration is admitted as conclusive in the case of the parasitic Crustacea and Cirrhipedes. It is equally incontestable in that very large and varied group of non-parasitic organisms, the Tunicata (Urochordate Vertebrata).2
(in the above 'Vertebrata' is what we call 'Chordata'). He adds this footnote:
2The whole argument as to the Tunicates of course rests on the view- supported by many arguments, that the larval urochord, which many of
them possess, is not a larval organ acquired by larval adaptation, but is hereditary and transmitted from adult ancestors.
The term 'urochord' seems to be established and used without comment there, and probably is taken as simple neo-Latin for 'tail chord', although that may be somewhat loose, perhaps meaning the notochord is present but does not extend into the head. A 1913 Webster's Dictionary defines urochord as:
(Zool.) The central axis or cord in the tail of larval ascidians and of certain adult tunicates.
In 1882, Lankester futher discussed the anatomy of the tunicates in the context of the division of the chordata in a paper called "The Vertebration of the Tail of Appendiculariæ". This paper includes an illustration of a larval tunicate with the "notochord (urochord)" indicated.
The following is multiple choice question (with options) to answer.
Protists which use their tails to eat are called what? | [
"flagellators",
"swimmers",
"cycle - feeders",
"filter-feeders"
] | D | Some animal-like protists use their "tails" to eat. These protists are called filter-feeders . They acquire nutrients by constantly whipping their tails, called flagellum , back and forth. The whipping of the flagellum creates a current that brings food into the protist. |
SciQ | SciQ-6917 | microbiology, bacteriology
The American Type Culture Collection recommends Medium 416 for growth of Lactobacillus group organisms. This medium is comprised of lactobacillus MRS medium from BD and contains:
The following is multiple choice question (with options) to answer.
What term is used to describe foods containing active cultures of beneficial bacteria? | [
"probiotic",
"carotenoids",
"sembiotic",
"antibiotics"
] | A | Yogurt is a good source of calcium. Yogurt also contains active cultures of "good" bacteria. Foods that contain these beneficial bacteria are sometimes called "probiotic. ". |
SciQ | SciQ-6918 | newtonian-mechanics, forces, rotational-dynamics, torque
Title: Falling off a chair, how best to save yourself If I consider a man sitting on an office chair that reclines backwards iff you lean backwards.
What could be done to prevent hin from falling?
a) raising his legs till they are parallel to ground.
b) bring the feet closer to himself(as close as possible) and press them down on the ground.
Please don't suggest any other way. I want to compare these two. Ie, which is better.
Argument in favor of a)
The center of mass moves away from the rear end of the chair towards the forward end of the chair so torque of weight will restore the chair. (This works if you are in an armchair, and are rocking to and fro).
However, intuition says contrary to this. I feel scared of falling If I do this.
Argument in favour of b)
Intuition favours this. Normally when we talk about balancing our body, what "feels right" is better for the safety. So, I can not say what is right. Please explain what your views are in this case. Again, the purpose of this question is not to ask what should be done, only what is better to do out of these two choices. This sounds to me like an experimental question (but be careful not to hurt yourself!).
Note that since you want the chair to rotate forwards towards the ground, you'll want to consider the direction of the angular momentum your motion introduces. If you kick your legs out rapidly, not only does the weight of your feet tilt the chair forward, but the angular momentum of your legs moving upwards in front of the chair will tend to be balanced by an upward motion of the back of the chair. However, if you're tilted too far backwards before you kick out your legs, you'll get a second and opposite angular momentum kick once your knees are straight, which might send you over backwards.
This is why the best approach is to stick out your legs and pinwheel your arms.
The following is multiple choice question (with options) to answer.
What helps control the muscles and maintain balance? | [
"muscular system",
"circulatory system",
"lymphatic system",
"nervous system"
] | D | Staying balanced when riding a scooter requires control over the body’s muscles. The nervous system controls the muscles and maintains balance. |
SciQ | SciQ-6919 | work, units, dimensional-analysis, si-units
Title: What is the unit for work done? My textbook's equation for work done is:
work done = force * distance
So this means that the unit should be Nm. However, when I researched on Google, a lot of people were saying that the unit is J. J (joule) is a derived unit for energy (or work done) named after the physicist James Joule. Since $W = F.d$, we have 1 J=1 Nm. We can also express in terms of basic SI units, yielding us
1 J = 1 kg m$^2$s$^{-2}$.
The following is multiple choice question (with options) to answer.
What unit of power is equal to 1 joule of energy per second? | [
"byte",
"volt",
"watt",
"hertz"
] | C | The rate at which a device changes electric current to another form of energy is called electric power . The SI unit for power—including electric power—is the watt. A watt equals 1 joule of energy per second. High wattages are often expressed in kilowatts, where 1 kilowatt equals 1000 watts. The power of an electric device, such as a hair dryer, can be calculated if you know the voltage of the circuit and how much current the device receives. The following equation is used:. |
SciQ | SciQ-6920 | neuroscience, brain
Title: What is in the space between neurons in a brain? When neuron animations are displayed, there are frequently seen neurons, axons arranged in a lattice with a lot of empty space between. I'm interested if there is indeed empty space in the brain, or if it is filled with some sort of fluid? I've checked an article on cerebrospinal fluid but am not sure that it is present all throughout the brain.
The reason I'm asking is that I'm thinking of neurotransmitters- they are released in synapses, but I'm not sure how they stay there - are they suspended in some liquid as well? Not so empty, actually.
The human brain has a mass of ~1.5kg, and volume ~1200cc (a little bigger for men, a little smaller for women). So is heavier than water by a good margin.
While it has Cerebrospinal fluid, that only occupies the subarachnoid space (the space below the skull and above the cortex, contained between two layers: pia matter and arachnoid membrane) and the ventricular system (several spaces inside the brain, remnants of the embryological development of the brain).
Neuron density may vary widely, depending mainly on the particular characteristics of neuron cell types and their interconnections. But besides neurons, there's a lot of infrastructure inside the brain. For example:
Astroglia: They are a type of glial cells which participate in the formation of the blood-brain barrier (supporting the endothelial cells), nourishing of neurons, maintenance of ion and neurotransmitter concentrations, among others. They also keep in place most of the tissue.
Microglia: Small cells with immune (phagocitic) functions inside the brain.
Radial glia: A more specialized precursor cell, that also participates in neuronal migration in the brain.
Oligodendrocites: Cells responsible for the insulation (myelination) of axons.
Neuroepithelial cells: The stem cells in the brain.
The following is multiple choice question (with options) to answer.
What is just below the cerebrum and coordinates body movements? | [
"cerebellum",
"hypothalamus",
"spinal cord",
"bloodstream"
] | A | The cerebellum is just below the cerebrum. It coordinates body movements. Many nerve pathways link the cerebellum with motor neurons throughout the body. |
SciQ | SciQ-6921 | physiology, hematology
Title: What is the function of clot retraction? I am thinking how clot retraction and fibrinolysis work together.
I think that clot retraction is a process that gets clot towards fibrinolysis process.
Fibrinolysis process then lyses the clot.
However, I am not sure if it is so simple.
Some seems to be discussing about how to differentiate start of fibrinolysis from clot retraction morphologically.
So they probably seem to be at this stage similar processes visually, but not functionally.
What is the function of clot retraction? The platelets in the clot contain contractile proteins. They bring the edges of the wound together, which also reduces the chance of further bleeding. The contraction process also supports the wound healing process as it brings the ends of the wound together.
For more information see this article: "Mechanics and contraction dynamics of single platelets and implications for clot stiffening"
The following is multiple choice question (with options) to answer.
What part of blood releases clotting factors? | [
"erythrocytes",
"platelets",
"hemoglobin",
"white blood cells"
] | B | Platelets ( Figure below ) are very small, but they are very important in blood clotting. Platelets are not cells. They are sticky little pieces of larger cells. Platelets bud off large cells that stay in the bone marrow. When a blood vessel gets cut, platelets stick to the injured areas. They release chemicals called clotting factors, which cause proteins to form over the wound. This web of proteins catches red blood cells and forms a clot. This clot stops more blood from leaving the body through the cut blood vessel. The clot also stops bacteria from entering the body. Platelets survive in the blood for ten days before they are removed by the liver and spleen. |
SciQ | SciQ-6922 | metals
Title: Why does carbon alloy with iron specifically? Everyone knows what an alloy is: it's a metal made by melting two (or more) other metals together.
Unless of course you're talking about steel. That's a metal made by mixing carbon (very much not a metal) into molten iron. But you never hear about carbon alloys with any other metal, and that's kind of strange. If a few percentage points of carbon can turn iron into the miracle metal that is the foundation of the Industrial Age, just imagine what it could do to aluminum or titanium, for example. (Or even bronze, for that matter, which is superior to iron in many ways, from a materials science perspective.)
But you only ever hear about carbon alloying with iron to form steel. So what's so special about iron? It's true they are not common, but there are other alloys that use carbon. Nickel is probably one of the more common metals that form alloys with carbon that have desirable properties. For example, Nickel 200, Nickel 201, and Nickel 205 all contain carbon. (See: http://www.asminternational.org/documents/10192/1852239/ACFA9D7.pdf/d490dee6-620e-4e38-b64d-53dd02c5fc81). Chromium and Tungsten also form alloys with carbon called Stellite Alloys: See http://en.wikipedia.org/wiki/Stellite (although some, but not all, stellite alloys contain iron too).
The following is multiple choice question (with options) to answer.
Adding carbon to iron makes what type of metal? | [
"steel",
"titanium",
"plastic",
"ions"
] | A | Metals such as iron are useful for many purposes because of their unique properties. For example, they can conduct electricity and bend without breaking. However, pure metals may be less useful than mixtures of metals with other elements. For example, adding a little carbon to iron makes it much stronger. This mixture is called steel. Steel is so strong that it can hold up huge bridges, like the one pictured above. Steel is also used to make skyscrapers, cargo ships, cars, and trains. Steel is an example of an alloy. |
SciQ | SciQ-6923 | biochemistry, dna, rna
Title: Can a dNTP be built into a RNA strand? DNA consists of deoxyribonucleotides, RNA consists of ribonucleotides. They differ mainly (apart from the uracil / thymine difference) in the sugar part, the deoxyribose and the ribose. Those two molecules differ in the hydroxy group in the ribose which is only a single proton in the deoxyribose. This part of the sugar molecule is not directly involved in binding reactions, nevertheless it causes the whole difference in RNA and DNA.
I wonder: could a dNTP be used in an RNA strand (or vice versa)? Is it chemically possible that we have a RNA molecule that contains a dNTP next to its NTPs? This is rather easy to do if you synthesize oligonucleotides chemically and not enzymatically. This is typically done using phosphoramidite chemistry, and it allows for the synthesis of chimeric RNA/DNA oligos. You can even incorporate modified nucleosides like 2'-O-Me or LNA.
This is typically done if you want to change the properties of an oligo, e.g. if you want to make it resistant to degradation by enzymes.
The following is multiple choice question (with options) to answer.
Which structure includes sugar-phosphate "backbones", composed of alternating phosphate groups and deoxyribose sugars, and nitrogenous bases? | [
"molecule double helix",
"dna double helix",
"mulecular triplex",
"dna triple helix"
] | B | The DNA double helix. The two sides are the sugar-phosphate backbones, composed of alternating phosphate groups and deoxyribose sugars. The nitrogenous bases face the center of the double helix. As the base-pairing rules tell us, A always pairs with T, and G always pairs with C. |
SciQ | SciQ-6924 | redox, electrons
The loss of hydrogen is oxidation in cases of homolytic breaking the bond with hydrogen when the electron goes away with the proton. Heterolytic losing hydrogen ion(=hydrated proton), when the electron stays, is not oxidation, but acid dissociation.
The former case leads to change in oxidation number/state, the latter does not.
E.g. $\ce{CH4 + O2 -> C + 2H2O}$ is oxidation, as carbon is oxidized from the oxidation state -IV to 0.
Exchanging an acidic hydrogen and a ion of an electropositive metal between some acid and salt (i.e. the metal keeps its oxidation state) in cases like above:
$$\ce{MX_n + n HA -> n HX + MA_n}$$
does not change oxidation states of elements in involved compounds.
Therefore conversion $$\ce{MnS + 2HCl -> MnCl2 + H2S}$$
is not a redox reaction, as Mn keeps the oxidation state +II, sulphur -II hydrogen +I and chlorine -I.
The following is multiple choice question (with options) to answer.
In a hydrogen replacement reaction, the hydrogen in the acid is replaced by what? | [
"an active metal",
"water",
"gas",
"oxygen"
] | A | In a hydrogen replacement reaction, the hydrogen in the acid is replaced by an active metal. |
SciQ | SciQ-6925 | cell-division
Title: Are free-nuclear division and endomitosis the same? As far as I understood it, both are cases of karyokinesis, not followed by cytokinesis. No. If you google the terms you'll get a lot of sites with definitions. For example:
Nuclear division
Definition
noun
The process by which a nucleus divides, resulting in the segregation of the genome to opposite poles of a dividing cell.
source: http://www.biology-online.org/dictionary/Nuclear_division
Edit:
or
free nuclear division mitotic division of nuclei without accompanying cytokinesis, i.e. nuclei divide in a common cytoplasm, the cells walls only forming around each later
source: http://ecflora.cavehill.uwi.edu/bio_courses/bl14apl/Gloss.htm
versus
endomitosis
mitosis taking place without dissolution of the nuclear membrane, and not followed by cytoplasmic division, resulting in doubling of the number of chromosomes within the nucleus.
source: http://medical-dictionary.thefreedictionary.com/endomitosis
or a bit more revealing:
Duplicated chromosomes produced by endomitosis exist as discrete units
in a single polyploid nucleus or may be packaged into separate nuclei,
depending on the phase at which mitosis is aborted
source: http://en.wikipedia.org/wiki/Endoreduplication
So as you see by definition nuclear division is part of a bigger process (cell division), and accoriding to the first source karyokinesis is a synonim for nuclear division (karyo = nucleus kinesis = moving, both come form greek language).
Edit:
If you check the definition above, you can see that free-nuclear division is a mitosis without cytokinesis, thus chromosome separation still occurs.
In endomitosis the can end up with a polyploid nucleus, in contrast to the other two aforementioned mechanism where no polyploidy occurs.
The following is multiple choice question (with options) to answer.
Mitosis and meiosis are both forms of division of the nucleus in these? | [
"converts cells",
"reproduction cells",
"endogenous cells",
"eukaryotic cells"
] | D | Comparing Meiosis and Mitosis Mitosis and meiosis are both forms of division of the nucleus in eukaryotic cells. They share some similarities, but also exhibit distinct differences that lead to very different outcomes (Figure 11.7). Mitosis is a single nuclear division that results in two nuclei that are usually partitioned into two new cells. The nuclei resulting from a mitotic division are genetically identical to the original nucleus. They have the same number of sets of chromosomes, one set in the case of haploid cells and two sets in the case of diploid cells. In most plants and all animal species, it is typically diploid cells that undergo mitosis to form new diploid cells. In contrast, meiosis consists of two nuclear divisions resulting in four nuclei that are usually partitioned into four new cells. The nuclei resulting from meiosis are not genetically identical and they contain one chromosome set only. This is half the number of chromosome sets in the original cell, which is diploid. |
SciQ | SciQ-6926 | experimental-chemistry, analytical-chemistry
Title: Is there any way to quantitatively find when a reaction has completed? So I'm designing an experiment for measuring how the reaction time of copper and ferric chloride is dependent on temperature; here's the reaction:
$$
\ce{FeCl3 + Cu -> FeCl2 + CuCl}
$$
The problem I have right now is how to quantitatively measure when the reaction has ended. I know you can visually see when a small copper rod has completely dissolved, but I wanted there to be a quantitative aspect to it rather than qualitative.
I've thought of using a pH probe to see if the PH changes after the reaction takes places and stays static, which I could leverage as an endpoint of the reaction, but the pH probes my school are damaged, I think, since the reading keeps jumping around by about 3 or 4.
If you have measured reaction time in general before, I'd love to hear how you did it. Option 1: Spectrometry
Easiest method, in most cases accurate enough. If you know that there are no side-reactions, this is a safe bet. Simply measure some characteristic wavelength for one reactant (preferably $\ce{Fe^{3+}}$) and one product (I would go for the $\ce{Cu^{+}}$ there) and then make measurements of your reaction mixture on the fly.
Option 2: Titration
Not that recommendable if you need any reliable results, but if you are low on budget and/or want a didactic effect. Take a little sample from a big flask and do a $\ce{Fe^{2+/3+}}$-redox-titration.
Option 3: Electrolysis
Don't know how to implement that, but basically you would take the sample and measure the amount of electricity needed to convert all $\ce{Fe^{2+}}$ in that sample back to $\ce{Fe^{3+}}$. Probably more accurate than spectrometry as the measurements of currents can be done quite precisely
You could also do some weird stuff like quantitative chlorine-NMR, but I can not think of any benefit that you would have with that.
The following is multiple choice question (with options) to answer.
What is the last step in a scientific investigation? | [
"retesting findings",
"documenting findings",
"verifying findings",
"communicating findings"
] | D | The last step in a scientific investigation is communicating what you have learned with others. This is a very important step because it allows others to test your hypothesis. If other researchers get the same results as yours, they add support to the hypothesis. However, if they get different results, they may disprove the hypothesis. When scientists share their results, they should describe their methods and point out any possible problems with the investigation. Results can be communicated in various ways. A scientist usually contributes material through publication in a peer-reviewed scientific journal. Peer-review ensures the material is of an acceptable quality for the scientific community. Scientists also write review articles, book chapters, and even whole books. They also regularly participate in scientific meetings, presenting their material in front of large audiences of their peers. |
SciQ | SciQ-6927 | nuclear-physics
On the theoretical side, there is also
general agreement that this asymmetry originates from
the influence of shell effects in the nascent fragments[52, 53].
However, this seems to be subject to interpretation, and in fact the "decision" about the mode of fission is probably made long before scission, close to the top of the barrier. See, e.g., Zhang. At this relatively early stage, talking about shell structure of the fragments is at best an approximation or a heuristic.
There can also be cases where there is both a symmetric path and an asymmetric path, as in Ichikawa's calculation for ${}^{236}U$:
The following is multiple choice question (with options) to answer.
Where is multiple fission more often observed? | [
"among multi-celled organisms",
"among protists",
"among animals",
"among vertebrates"
] | B | Binary fission in various single-celled organisms (left). Cell division is a relatively simple process in many single-celled organisms. Eventually the parent cell will pinch apart to form two identical daughter cells. In multiple fission (right), a multinucleated cell can divide to form more than one daughter cell. Multiple fission is more often observed among protists. |
SciQ | SciQ-6928 | evolution, neuroscience
This paper's abstract says all I was saying about the development of neurons and synapses relying on pre-existing molecules and structures:
https://pubmed.ncbi.nlm.nih.gov/2830635/
"Evolution of Neurotransmitter Receptor Systems"
What I'm looking for to find how close science is to answering your question (or if it already has) is papers looking at the phylogenetic relationships of different neurotransmitters and related molecules. That might say a lot about which ones have been used as neurotransmitters the longest. I haven't found this yet but I'll try more tomorrow when I'm not on mobile.
ETA: will re-edit this comment later, but this paper answers your question I believe, or as well as any could at present at least:
https://cichlid.biosci.utexas.edu/sites/default/files/evoneuro/files/liebeskind_et_al_2017.pdf?m=1511200627
"Evolution of Animal Neural Systems"
This paper, which is available in full and is a review paper from 2017, looks at the evolution of every aspect of animal neural systems (i.e. nervous systems mediated by neurons, a concept the paper also defines because the line is apparently blurry). One interesting aspect of it is that while you point to Cnidarians as the most "primitive" nervous systems, the paper points out the latest evidence suggests Ctenophores are the earliest branch off the animal tree, meaning nervous systems either evolved convergently, or sponges lost their nervous systems secondarily, in which case Cnidarians would lose this special status.
The paper has a section about neurotransmitters, which says the following:
The following is multiple choice question (with options) to answer.
What type of invertebrates where the earliest animals? | [
"annelids",
"cnidaria",
"aquatic invertebrates",
"arachnids"
] | C | The oldest animal fossils are about 630 million years old. The earliest animals were aquatic invertebrates. The first vertebrates evolved around 550 million years ago. By 500 million years ago, most modern phyla of animals had evolved. |
SciQ | SciQ-6929 | forces, momentum, elasticity
Title: Why does rubber ball bounce back while iron ball doesn't? Suppose there are two balls, one of rubber and the other metallic. There are of the same mass and are thrown on a wall with the same velocity. Why does a rubber ball bounce back while a metallic ball simply falls down after striking with the wall? I know it has got to do something with the change in linear momentum and its elasticity but what? If you use a plate glass window instead of a wall you'll find that the rubber and iron balls bounce by a similar amount (though be careful throwing iron balls at windows :-).
It's a basic principle in physics that energy cannot be lost. The rubber ball starts off with kinetic energy, hits the wall, and rebounds moving with about the same kinetic energy. So no energy is lost. If the iron ball doesn't bounce it must mean that the energy it originally had has been transferred to the wall.
Rubber balls are soft, so they decelerate relatively slowly and they deform and spread out as they hit the wall. This means that the pressure they exert on the wall while they are bouncing is relatively low. By contrast an iron ball is very hard so it stops very suddenly and all the force it exerts on the wall is concentrated on a small area. That means the pressure is high enough to damage the wall. It might cause a visible dent, or it might just cause cracks within the wall that you can't see. In both cases energy is used in damaging the wall, and this energy comes from the motion of the ball. That means little energy is left for the iron ball to bounce back.
I started by saying the iron ball would bounce off plate glass. This is because plate glass is very rigid and provided you don't shatter it the glass is not damaged by the iron ball. Since no energy is absorbed by the glass, the iron ball bounces back just as the rubber ball does.
The following is multiple choice question (with options) to answer.
Unlike wood and glass, steel is an example of a material that responds to what force? | [
"kinetic",
"thermal",
"electromagnetic",
"magnetic"
] | D | Magnetism is the ability of a material to be attracted by a magnet and to act as a magnet. No doubt you’ve handled refrigerator magnets like the ones in Figure below . You probably know first-hand that they stick to a metal refrigerator but not to surfaces such as wooden doors and glass windows. Wood and glass aren’t attracted to a magnet, whereas the steel refrigerator is. Obviously, only certain materials respond to magnetic force. |
SciQ | SciQ-6930 | nuclear-physics
Moderator temperature affects that above thermal peak of neutrons, and the location of the peak affects reactivity
The fuel has absorption peaks between the fast and thermal energies, and the fuel temperature affects the efficiency of these peaks through a more complicated effect
I should note that our reactors will come to equilibrium given enough time (provided we build them stable). So if you change reactivity, then ultimately that will result in a change in the fission reaction rate. But practically, the operators control the reaction rate with engineered methods (control rods), and that is set by regulatory concerns.
So if you change the moderator temperature, you will change the reaction rate. As I've described, this is due to mechanisms that vaguely fit the intuition you had. Changing temperature literally changes the temperature of the neutrons. This matters for the reaction because neutrons are absorbed by the fuel at lower energies much faster than at higher energies.
Things are a little bit more wonky than this, because a higher reaction rate produces more heat, which heats up the reactor more - creating a feedback loop. But we can still control the temperature of the moderator/coolant that we pump into the reactor.
The role of fuel temperature is much more complicated. This is the resonance absorption peak Doppler broadening effect. Basically, there are lots of very very narrow absorption peaks in the epithermal range (in the graph). As the fuel heats up, these "smear" out into larger energy ranges. With the peaks less sharp, there are fewer "windows" though the neutrons can sneak through the downscattering gauntlet.
The doppler effect is actually the dominant effect for the reactor control. It's honestly the main thing that we rely on for keeping the reactors stable, since it's clearly a negative feedback, and it acts very quickly (since most the the fission heat is deposited directly in the fuel).
So let me conclude by saying that #1 has a lot of mechanistic qualities that resemble the intuition you had about temperature (in the conventional sense) affecting reaction rate. On the other hand, #2 is more important for operating reactors, and it's qualitatively quite differently from the fusion temperature and reaction rate interdependence.
The following is multiple choice question (with options) to answer.
Carefully controlling the speed of a fission reaction produces what kind of energy? | [
"chemical",
"atomic",
"thermal",
"nuclear"
] | D | Nuclear energy is produced by carefully controlling the speed of a fission reaction. |
SciQ | SciQ-6931 | electric-circuits, electricity
Title: How do electrons travel between wires? I know that electrons can travel in metals when an electric field is applied and there is a potential difference created. This is due to the delocalized electrons which are free to move and have a small drift-velocity, and all of this is fine inside the metallic body; however, when we make a circuit, we join the ends of two wires through which electrons can move.
Now these ends of the wires are not metallically bonded, they are just 'physically' touching each other, so how do delocalized electrons from one wire transfer into another wire? I mean it's not like the delocalized electrons have a path to go from one wire to another, right? Do they 'jump' such small distances or do they follow some other mechanism? Do wires touching each other act like they are metallically bonded?
I have tried conducting some preliminary research on this question; however, I could not find much regarding my question. Let us take a simple example , a battery with two wires soldered so there is no surface between the pole and the wires. If we bring the two wires near each other , at a small distance a spark will happen ,a short, due to the migration of positive and negative charges over the distance between the two wires.
Contacts have been devised so as to be able to close the distance without sparking.The metallic surface of the contact,
allowing the charge transfer without sparking.
After this there are studies on what is called "contact resistance", from the abstract
A factor complicating the control of electric circuits is the contact resistance set up between two mating surfaces of metal which at times have to be separated in order to break continuity of supply. The two main methods of decreasing contact resistance-excluding the use of special contact tips-are to increase the contact area and to increase the contact pressure.
You ask:
Do they 'jump' such small distances
Well , it is quantum dimensions at the level of contact, one could call it jump,
Do wires touching each other act like they are metallically bonded?
Not really, as there is resistance to overcome.
From the abstract:
The following is multiple choice question (with options) to answer.
When two electric contacts come together it completes a what? | [
"breaker",
"atom",
"cricuit",
"charge"
] | C | Figure below shows a diagram of a simple doorbell. Like most doorbells, it has a button located by the front door. Pressing the button causes two electric contacts to come together and complete an electric circuit. In other words, the button is a switch. The circuit is also connected to a voltage source, an electromagnet, and the clapper of a bell. When current flows through the circuit, the electromagnet turns on, and its magnetic field attracts the clapper. This causes the clapper to hit the bell, making it ring. Because the clapper is part of the circuit, when it moves to strike the bell, it breaks the circuit. Without current flowing through the circuit, the electromagnet turns off. The clapper returns to its original position, which closes the circuit again and turns the electromagnet back on. The electromagnet again attracts the clapper, which hits the bell once more. This sequence of events keeps repeating as long as the button by the front door is being pressed. |
SciQ | SciQ-6932 | bond
Title: Types of bonds in a molecule For example in dinitrogen pentoxide, $\ce{N2O5}$, covalent as well as coordinate bonds (type of covalent bonds) are present, but it appears that it contains only covalent bond.
What is a proper method to find out which type of bonds are present in a molecule? Electrovalent bonds are easiest to identify. If a compound is made up of a metal and non-metal/non-metallic radical (like carbonate), then, 99.99% times, it contains electovalent bond. If a compound is made up of 2 or more non-metals/non-metallic radicals, then it contains covalent bond. Coordinate covalent bonds appear mostly with compounds containing Hydrogen element. To identify the coordinate covalent bonds, you can draw the branched structural formula of the compound and see if the shared pair of electrons are coming from the same molecule.
The following is multiple choice question (with options) to answer.
Pure nonpolar covalent bonds exist only between what? | [
"two altered atoms",
"two identical atoms",
"three altered atoms",
"two producing atoms"
] | B | Pure nonpolar covalent bonds exist only between two identical atoms. The H-H bond would be 100% covalent, because there is no difference in electronegativity between the two atoms. |
SciQ | SciQ-6933 | experimental-physics, nuclear-physics, radioactivity, statistics, half-life
$$t_{\rm average} = \frac{6.45\times 10^9\times 365.2422\times 86400}{2.53\times 10^{24}}{\rm seconds} = 8.05\times 10^{-8} {\rm seconds}. $$
So one gets about 12.4 million decays during one second. (Thanks for the factor of 1000 fix.) These decays may be observed on an individual basis. Just to be sure, $T$ was always a lifetime in the text above. The half-life is simply $\ln(2) T$, about 69 percent of the lifetime, because of some simple maths (switching from the base $e$ to the base $2$ and vice versa).
If we observe $\Delta N$ decays, the typical relative statistical error of the number of decays is proportional to $1/(\Delta N)^{1/2}$. So if you want the accuracy "1 part in 1 thousand", you need to observe at least 1 million decays, and so on.
The following is multiple choice question (with options) to answer.
The decay rate is measured in a unit called the what? | [
"radioactive decay",
"decay rate",
"half-life",
"exponential decay"
] | C | The decay of an unstable isotope to a stable element occurs at a constant rate. This rate is different for each isotope pair. The decay rate is measured in a unit called the half-life. The half-life is the time it takes for half of a given amount of an isotope to decay. For example, the half-life of carbon-14 is 5730 years. Imagine that you start out with 100 grams of carbon-14. In 5730 years, half of it decays. This leaves 50 grams of carbon-14. Over the next 5730 years, half of the remaining amount will decay. Now there are 25 grams of carbon-14. How many grams will there be in another 5730 years? Figure below graphs the rate of decay of carbon-14. |
SciQ | SciQ-6934 | cholesterol
Some LDL cholesterol circulating through the bloodstream tends to deposit in the walls of arteries. This process starts as early as childhood or adolescence.
White blood cells swallow and try to digest the LDL, possibly in to digest the LDL, possibly in an attempt to protect the blood vessels.
In the process, the white blood cells convert the LDL to a toxic (oxidized) form.
More white blood cells and other cells migrate to the area, creating steady low steady low-grade inflammation in the artery wall.
Over time, more LDL cholesterol and cells collect in the area. The ongoing process creates a bump in the artery wall called a plaque. The plaque is made of cholesterol, cells, and debris.
The process tends to continue, growing the plaque and slowly blocking the artery.
There is a good overview of the general physiology here in Robbins The Pathologic Basis of Disease. Chapter 5, Genetic Disorders, reviews the physiology, and the relevance to disease, in the section on Familial Hypercholesterolemia. The review is relevant to hypercholesterolemia in general.
The following is multiple choice question (with options) to answer.
What is a condition in which a material called plaque builds up inside arteries? | [
"fibrosis",
"scoliosis",
"atherosclerosis",
"arthritis"
] | C | Atherosclerosis is a condition in which a material called plaque builds up inside arteries. Plaque consists of cell debris, cholesterol, and other substances. As plaque builds up in an artery, the artery narrows, as shown in Figure below . This reduces blood flow through the artery. |
SciQ | SciQ-6935 | electromagnetic-radiation, terminology
But cosmic rays are particles, not electromagnetic rays, right? That seems like a huge error! Could they be referring to gamma ray bursts? "Cosmic rays" can be any energetic quanta (including photons) that impinge on the atmosphere, coming from deep space—as opposed to, say, the sun. When they are observed at the surface of the Earth, we distinguish the original quanta that traveled across interstellar space as "primary cosmic rays," versus "secondary cosmic rays" that are produced through the collision of the primaries with the atmosphere. So a primary cosmic ray can produce a cascade of secondary cosmic rays descending toward the surface—an "air shower."
The most energetic primary cosmic rays are hadronic, some mixture of protons and highly stable nuclei like $^{4}$He and $^{56}$Fe. The spectrum of cosmic ray protons extends up about $10^{20}$ eV; beyond this energy scale (the GZK cutoff), the protons interact too strongly with the cosmic microwave background to travel over the Mpc distances between the active galactic nuclei where they originate and telescopes on Earth. However, there is also a high-energy photon component to among primary cosmic rays, and those are the most energetic (or shortest wavelength) photons that have ever been observed, with energies up to about $10^{14}$ eV. These are what charts like that of the electromagnetic spectrum mean by "cosmic rays."
The following is multiple choice question (with options) to answer.
Quarks in the middle energy family are found in cosmic rays and are produced in what? | [
"particle accelerators",
"cosmic accelerators",
"particle processors",
"particle splicers"
] | A | Everyday objects are made up of quarks from the lowest energy family, namely up and down quarks. Quarks in the middle energy family are found in cosmic rays and are produced in particle accelerators. Particles in the high energy family are believed to have existed briefly during the earliest moments of the Big Bang and are created only in high energy collisions. |
SciQ | SciQ-6936 | general-relativity, astrophysics, dark-matter, dark-energy, galaxy-rotation-curve
The reason photons make a much lower contribution to the Solar System than to the universe as a whole is because mass is much more concentrated in the Solar System than in the universe as a whole.
The following is multiple choice question (with options) to answer.
What celestial body in the solar system makes up most of its total mass? | [
"earth",
"sun",
"Andromeda",
"Jupiter"
] | B | The Sun makes up almost all of the mass of the solar system. |
SciQ | SciQ-6937 | human-biology, human-anatomy
Finally, how can this be interpreted from an evolutionary point of view?
Evolutionary interpretation of height differences in human males and females
Differences in height (but also other traits) between sexes of a species are refered to as sexual dimorphisms. Sexual dimorphism (at least in primates) in height is strongly related to differences in mating behaviour and a sign of aggression and/or dominance-based mating patterns (Wynn and Coolidge (2011, p.82), sorry for that poor referenc link). The counterpart to this is pair-bonding, or in human terms marriage: a primate example is our pretty close relative, the Gibbon, that is (at least socially) monogamous and as expected does not have a height-related sexual dimorphism. Great apes including humans do have this polymorphism even though pair-bonding in humans is widely spread. Therefore, it was not surprising to find a reduction in height dimorphism from Australopithecus over Homo erectus to Homo sapiens (Wynn and Coolidge, 2011, p. 83, see also this, especially the last paragraph of this chapter).
Update on the main source
One of the papers I mainly used for this answer - to illustrate selection on height - was a preprint. It is now published in Science: Field et al. (2016).
The following is multiple choice question (with options) to answer.
Free ear lobes, widow's peak and a dimpled chin are examples of what kind of traits in humans? | [
"mendelian",
"adaptations",
"genetic disorders",
"spontaneous mutations"
] | A | In many instances, the relationship between genes and inheritance is more complex than that which Mendel found. Nevertheless, geneticists have since found that Mendel’s findings can be applied to many organisms. For example, there are clear patterns of Mendelian inheritance in humans. These include the inheritance of normal characteristics and characteristics that occur less often. Easily observable Mendelian traits in humans include free ear lobes (in most people the ear lobes hang free (dominant), whereas the attached earlobe is recessive), hitchhiker's thumb (a straight thumb is dominant, while a bent thumb is recessive), widow's peak (a hairline with a distinct point in the middle of the forehead is dominant, while a straight hairline is recessive), dimpled chin (a cleft in the chin is dominant, whereas the absence of a cleft is recessive), and mid-digital hair (hair on any middle segments of the fingers is dominant). Of course, many severe human phenotypes are inherited in a Mendelian fashion including Phenylketonuria (PKU), cystic fibrosis, Huntington's disease, hypercholesterolemia, and sickle-cell anemia. These are termed genetic disorders and will be discussed in additional concepts. |
SciQ | SciQ-6938 | thermodynamics, visible-light
Title: Is heat always associated with Light? I have found that light always produces heat. The only cases I think heat is absent with light is Fluorescence and Phosphorescence (maybe because they emit low energy but maybe the heat is still present?). So my question is: Is heat energy always present when light is emitted, specially for bright light(more energy)?
If some example or any links can be provided, then it will be very helpful. Thermal radiation is emitted by any surface having a temperature higher than absolute zero. So the short answer to your question is yes. Light (electromagnetic radiation) of any frequency will heat surfaces that absorb it. In case of Fluorescence, the emitted light has a longer wavelength (lower frequency), and therefore lower energy, so that's why you feel the heat is absent.
The following is multiple choice question (with options) to answer.
Producing light without heat is called what? | [
"bioluminescence",
"thermoluminescence",
"osmosis",
"luminescence"
] | D | The sun and other stars produce light because they are so hot. They glow with light due to their extremely high temperatures. This way of producing light is called incandescence . Some objects produce light without becoming very hot. They generate light through chemical reactions or other processes. Producing light without heat is called luminescence . Objects that produce light by luminescence are said to be luminous. Luminescence, in turn, can occur in different ways:. |
SciQ | SciQ-6939 | statistical-mechanics, atmospheric-science, density
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake waters, forming a gas cloud that can suffocate wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can be a trigger for such phenomenon. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes.
Picture 1: one of a number of cattle killed by a limnic eruption at Lake Nyos, Cameroon.
We can occasionally prevent the buildup of carbon dioxide by degassing the body of water.
Picture 2: a siphon used by French scientists to de-gas Lake Nyos. The carbon dioxide emerges from its deposits and bubbles into the water, floating to the top.
The following is multiple choice question (with options) to answer.
What natural part of the water cycle can cause damage and death? | [
"expiration",
"clouds",
"floods",
"evaporation"
] | C | Floods are a natural part of the water cycle, but they can cause a lot of damage. Farms and homes may be lost, and people may die. In 1939, millions of people died in a flood in China. Although freshwater is needed to grow crops and just to live, too much freshwater in the same place at once can be deadly. |
SciQ | SciQ-6940 | reproduction
Excerpts from the references that lead to the short answer above:
In the developing female fetus, oogonia become primary oocytes that begin the first division of meiosis. However, this division is not completed and the primary oocytes remain “frozen” in the prophase stage of the first meiotic division.
At birth, oogonia are no longer present. Each primary oocyte is surrounded by a single layer of squamous epithelial cells called follicular cells. The primary oocyte together with its follicular cells is called a primordial follicle. There are about two million primordial follicles with their primary oocytes in the ovaries at birth suspended in the first division of meiosis.
As the female grows, primary oocytes begin to die and disappear with their follicular cells. This process continues until puberty when there are only about 400,000 primordial follicles left in the ovaries. The primary oocytes continue the process of oogenesis after puberty begins.[Source]
The total number of primary oocytes at birth is estimated to vary from 700,000 to2 million. During childhood most oocytes become atretic; only approximately400,000 are present by the beginning of puberty, and fewer than 500 will be ovulated.[Source]
Primary oocytes reach their maximum development at ~20[6] weeks of gestational age, when approximately seven million primary oocytes have been created; however, at birth, this number has already been reduced to approximately 1-2 million.Recently, however, two publications have challenged the belief that a finite number of oocytes are set around the time of birth.[Source]
In the human embryo, the thousand or so oogonia divide rapidly from the second to the seventh month of gestation to form roughly 7 million germ cells.[Source]
REFERENCES:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008772
The following is multiple choice question (with options) to answer.
How many large eggs are generated during oogenesis? | [
"4",
"3",
"2",
"one"
] | D | |
SciQ | SciQ-6941 | 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.
Gaseous nitrogen is converted into forms that can be used by plants during a process called what? | [
"oxygen fixation",
"plant fixation",
"dioxide fixation",
"nitrogen fixation"
] | D | Gaseous nitrogen is converted into forms that can be used by plants during the process of nitrogen fixation. |
SciQ | SciQ-6942 | bacteriology, food, hematology, toxicology, parasitology
Title: Blood consumption Is consumption of blood more "dangerous" compared to meat?
There was a news-article about unnatural chemicals found in the blood of mothers. This reminded me about a question I have pondered upon from time to time. Now, I am not a vampire, but curious as to the nature of blood vs meat in animals. More specifically unhealthy components.
There are various examples of viruses being in danger of spreading by consumption of raw blood like ebola, H5N1 etc. (But then also meat etc.)
Perhaps easier if I throw out some questions to show what I am asking:
Are there more of such in blood then meat?
Are there other things that can be worse in blood even after preparing? Like cooking, conservation etc.
Are parasites etc. more frequently found in blood?
Are there organisms that are highly resilient to heat treatment found in blood?
Are there more heavy metals in blood then meat? (Which I assume cooking does not give much of a difference.)
Other toxins?
Some references:
http://www.eufic.org/article/en/food-safety-quality/animal-health/expid/review-animal-diseases/
http://www.fao.org/avianflu/en/qanda.html
Is consumption of blood more "dangerous" compared to meat?
Actually yes, a simple high dose of blood is enough to kill. The cause is, though it is most important thing to live when flowing the vessel, it's highly toxic when consumed. There are high chances of getting haemochromatosis or Iron overload.
Source and More on this:
http://www.livescience.com/15899-drinking-blood-safe.html
Composition of Blood
(source: snmjournals.org)
The following is multiple choice question (with options) to answer.
What is an example of a disease that affects the blood? | [
"tuberculosis",
"scoliosis",
"anemia",
"rickets"
] | C | Many diseases affect the blood or its components. They include anemia, leukemia, hemophilia, and sickle-cell disease. |
SciQ | SciQ-6943 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Name the term used to described prokaryotes that require oxygen. | [
"aerobic",
"anaerobic",
"mouth breathers",
"hydrophylic"
] | A | Prokaryotes that need oxygen are described as aerobic. They use oxygen for cellular respiration. Examples include the prokaryotes that live on your skin. |
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