source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-2644 | glaciology, energy-balance
Title: How can sublimation of glacial ice cause positive mass balance?
I am trying to understand how the sublimation process can cause a positive mass balance in general, intuitively as highlighted in the text taken from W. S. B. Paterson,The Physics of Glaciers: 3rd Edition(Pergamon, New York, 1994).
Thank you. Strictly speaking sublimation is the phase change from solid to gas without an intermediate liquid phase. So the way the term sublimation has been used in the text is partly wrong. Ice and snow on a glacier can sublimate so that mass is lost directly to the atmosphere as water vapour.
Water vapour in the atmosphere an also be deposited on the glacier as a solid in a reverse process called deposition or desublimation. This is where the text example contains an error in terminology.
The term in the equation conerning phase changes from solid to gas or gas to solid is of course correct and it may be either positive or negative depending on which phase change direction dominates. As is stated losses from solid to gas is likely larger in most if not all cases.
The following is multiple choice question (with options) to answer.
Condensation, melting, deposition, sublimation, vaporization, and freezing are all considered changes in what? | [
"altitude",
"speed",
"density",
"state"
] | D | Changes of state are physical changes in matter. They are reversible changes that do not involve changes in matter’s chemical makeup or chemical properties. Common changes of state include melting, freezing, sublimation, deposition, condensation, and vaporization. These changes are shown in Figure below . Each is described in detail below. |
SciQ | SciQ-2645 | optics, refraction, lenses, vision
Title: Refractive screen for myopia Is it possible to create a screen for a computer monitor to allow a Myopic person to see the screen without glasses? Myopia shortens the maximum focus length of an eye, i.e., the converging action of a myopic eye is too strong and, as a result, the image of a distant object is formed in front of the retina - not on the retina.
Nearsighted vision is corrected by placing a corrective concave lens in front of the eye - its diverging action compensating the excessive converging action of the eye. We can also say that, by its diverging action, the concave lens brings distant objects closer to the eye - to some short distance from which a myopic eye can focus them properly.
The stronger the myopia, the stronger the required concave lens action, the shorter that "clear vision" distance.
For this paradigm to work, the corrective lens has to be located closer to the eye than the clear vision distance and a distant object, which requires correction, has to be located further from the eye than the clear vision distance.
Obviously, under these conditions, the monitor and its corrective lens would have to be separated in space, which means that the corrective lens cannot be built into the screen.
Of course, we could have a giant magnifying glass built into the screen, like it was done in early TV's with tiny screens. This would magnify the image and make it easier to make out the details, but the image would still be out of focus.
The following is multiple choice question (with options) to answer.
Myopia and hyperopia are defects that can be corrected with devices? | [
"fins",
"lenses",
"casts",
"crutches"
] | B | Myopia and hyperopia can be corrected with lenses. |
SciQ | SciQ-2646 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
What do you call the part of the skeletal system that connects bones? | [
"tissue",
"fibers",
"joints",
"muscles"
] | C | Running. A means of terrestrial locomotion allowing humans and other animals to move rapidly on foot. The knees, which connect one part of the leg to the other, have to allow the legs to move. The knee is a joint, the part of the skeletal system that connects bones. |
SciQ | SciQ-2647 | cell-biology, proteins, cell-membrane, membrane-transport
Title: Why can't H3O+ ions pass through aquaporins? Aquaporins are proteins that facilitate the movement of water (and related molecules) through cell membranes. (Also, these transport proteins are very specific about what they transport.) Interestingly, aquaporins can facilitate the passage of glycerol but not H3O+ ions. This is difficult to comprehend as the structure of glycerol is quite dissimilar to H2O while H3O+ is quite similar to H2O.
What is the reason behind this? This question has been directly addressed by the paper The Mechanism of Proton Exclusion in the Aquaporin-1 Water Channel. I think it's a pretty good one too! I paste the abstract below:
Aquaporins are efficient, yet strictly selective water channels.
Remarkably, proton permeation is fully blocked, in contrast to most
other water-filled pores which are known to conduct protons well.
Blocking of protons by aquaporins is essential to maintain the
electrochemical gradient across cellular and subcellular membranes. We
studied the mechanism of proton exclusion in aquaporin-1 by multiple
non-equilibrium molecular dynamics simulations that also allow proton
transfer reactions. From the simulations, an effective free energy
profile for the proton motion along the channel was determined with a
maximum-likelihood approach. The results indicate that the main
barrier is not, as had previously been speculated, caused by the
interruption of the hydrogen-bonded water chain, but rather by an
electrostatic field centered around the fingerprint Asn-Pro-Ala (NPA)
motif. Hydrogen bond interruption only forms a secondary barrier
located at the ar/R constriction region. The calculated main barrier
height of 25-30 kJ mol(-1) matches the barrier height for the passage
of protons across pure lipid bilayers and, therefore, suffices to
prevent major leakage of protons through aquaporins. Conventional
molecular dynamics simulations additionally showed that negatively
charged hydroxide ions are prevented from being trapped within the NPA
region by two adjacent electrostatic barriers of opposite polarity.
The following is multiple choice question (with options) to answer.
What type of molecules sit within a membrane and contain an aqueous channel that spans the membrane’s hydrophobic region? | [
"osmotic fluid",
"mole",
"channel",
"microorganisms"
] | C | you could prove that movements are occurring even in the absence of a gradient. In a similar manner, there are analogous carrier systems that move hydrophobic molecules through water. Channel molecules sit within a membrane and contain an aqueous channel that spans the membrane’s hydrophobic region. Hydrophilic molecules of particular sizes and shapes can pass through this aqueous channel and their movement involves a significantly lower activation energy than would be associated with moving through the lipid part of the membrane in the absence of the channel. Channels are generally highly selective in terms of which particles will pass through them. For example, there are channels in which 10,000 potassium ions will pass through for every one sodium ion. Often the properties of these channels can be regulated; they can exist in two or more distinct structural states. For example, in one state the channel can be open and allow particles to pass through or it can be closed, that is the channel can be turned on and off. Channels cannot, however, determine in which direction an ion will move - that is determined by the ion gradient across the membrane. The transition between open and closed states can be regulated through a number of processes, including the reversible binding of small molecules to the protein and various other molecular changes (which we will consider when we talk about proteins). Another method of channel control depends on the fact that channel proteins are i) embedded within a membrane and ii) contain charged groups. As we will see cells can (and generally do) generate ion gradients, that, is a separation of charged species across their membranes. For example if the concentration of K+ ions is higher on one side of the membrane, there will be an ion gradient where the natural tendency is for the ions to move to the region of lower K+ concentration.222 The ion gradient in turn can produce an electrical field across the plasma membrane. As these fields change, they can produce (induce) changes in channel structure, which can switch the channel from open to closed and vice versa. Organisms typically have many genes that encode specific channel proteins which are involved in a range of processes from muscle contraction to thinking. As in the case of carriers, channels do not determine the direction of molecular motion. The net flux of molecular movement is determined by the gradients of molecules across the membrane, with the thermodynamic driver being entropic factors. That said, the actual movement of the molecules through the channel is driven by thermal motion. Questions to answer & to ponder: • What does it mean to move up a concentration gradient? • Are there molecules that can move up their concentration gradients spontaneously? • Where does the energy involved in moving molecules come from? Is there a force driving the movement of molecules "down" their concentration gradient? • If there is no net flux of A, even if there is a concentration gradient between two points, what can we conclude? • Draw a picture of valinomycin’s position and movements within a typical membrane. What drives the movement of valinomycin in the membrane and what factors lead to a net flux in K+ movement? • What happens to the movement of molecules through channels and transporters if we reverse the concentration gradients across the membrane? 222. |
SciQ | SciQ-2648 | physical-chemistry, thermodynamics, gas-laws, equation-of-state
I am confused by this argument-- what exactly is the definition of 'volume' here? They seem to be saying that it is the empty space around the gas molecules, but it seems to me that volume should be defined as the space 'taken up' by the gas. Why should the space taken up by the particles themselves be subtracted? This isn't done for solids or liquids as far as I know.
These thoughts have also made me realize that I'm not quite sure what it means for a gas to 'take up' space. Does anyone have a rigorous definition of gas volume?
EDIT: The exchange with Chris in comments has raised further questions. It now seems to me that the $V-nb$ correction actually accounts for repulsions rather than attractions. I think I was incorrect in thinking that the $V-nb$ correction dominated at intermediate volumes and $a(n/V)^2$ at low volumes. If $V-nb$ is for repulsions, then it should dominate at low volumes, but I can't tell from the equation which correction will actually be dominant. Also I am now wondering whether it even makes sense to connect one correction with repulsions and one with attractions.
EDIT: Follow-up questions for F'x:
- I thought that 'density' meant mass/volume. Is the use of it to represent the inverse of molar volume (as you have used it) common?
- Where is the phase-transition in the red van der Waals curve?
- I am still a little unclear on gas volume. Are the 'volume available to the gas' and 'volume of the gas' the same? You say it's the same as the shape of the container, but aren't we subtracting the volume of the actual gas particles from that? The $V$ term represents the volume of the gas, correct? And $V-nb$ represents the 'volume available to the gas'. The van der Waals equation can't be derived from first principles. It is an ad-hoc formula. There is a "derivation" in statistical mechanics from a partition function that is engineered to give the right answer. It also cannot be derived from first principles.
The following is multiple choice question (with options) to answer.
What state of matter has a definite volume, but takes the shape of the container? | [
"gas",
"solid",
"liquid",
"plasma"
] | C | Liquids have a definite volume, but take the shape of the container. |
SciQ | SciQ-2649 | homework-and-exercises
Title: Is geothermal energy ultimately derived from solar energy? The following question is taken from 10th class science NCERT book chapter 14th.
Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Sun’s energy?
(a) geothermal energy (b) wind energy
(c) nuclear energy (d) bio-mass.
The answer is given as (c) nuclear energy.
I understand that the wind moves because of the uneven heating of the earth by the sun. And biomass uses solar energy for photosynthesis.
How is geothermal energy ultimately derived from the sun? It is not a correct statement:
Geothermal energy comes from the heat within the earth. The word "geothermal" comes from the Greek words geo, meaning earth," and therme, meaning "heat." People around the world use geothermal energy to produce electricity, to heat buildings and greenhouses, and for other purposes.
The earth's core lies almost 4,000 miles beneath the earth's surface. The double-layered core is made up of very hot molten iron surrounding a solid iron center. Estimates of the temperature of the core range from 5,000 to 11,000 degrees Fahrenheit (F). Heat is continuously produced within the earth by the slow decay of radioactive particles that is natural in all rock
italics mine.
Geothermal energy comes from the original energy of the matter solidifying into the sun-planetary system, ultimately from the Big Bang, and from continuous nuclear decays and reactions .
The following is multiple choice question (with options) to answer.
Where does the earth gets its energy from? | [
"heat",
"sun",
"decomposers",
"precipitation"
] | B | Earth gets its energy from the Sun. The Sun gives off photons of energy that travel in waves. All the wavelengths of the Sun’s energy make up the electromagnetic (EM) spectrum. |
SciQ | SciQ-2650 | bond, ions, electrons, metal
Title: possibility of metallic ammonium In chemistry class, we discussed how metallic bonding occurs when metals lose electrons and become cations while the lose electrons become delocalized electrons and bind the metal cations. These electrons are then free to flow around the metal cations. But could the metal be replaced with an ammonium cation instead? (Or any other polyatomic cation, but we only learn ammonium and I'm not aware of any others minus hydronium which doesn't exist out of a solution.) Would the electrons still be free? How would you make it? And how could you prevent the following from occurring?
$$\ce{2NH4+ + 2e- -> 2NH3 + H2}$$ A nomenclature note: conventionally, in chemistry "a metal" is an element (such as a transition metal or alkali metal). If what you're talking about is a substance that behaves as a metal, that's typically referred to as metallic, like metallic glasses.
Therefore, I would rephrase your question as "Can metallic ammonium exist?" - in fact, this has been a question for quite awhile. From what I've read, there's a theoretical basis that it should be possible at given temperatures and pressures, but it hasn't been experimentally observed. The papers I was reading were from the 50s-70s, so I'll keep looking for more recent information.
Solvated electrons are slightly related, in that there is a "free" electron, and this was in fact originally documented in liquid ammonia.
The following is multiple choice question (with options) to answer.
In chemical reactions, what substances can act like metals or nonmetals, depending on their number of electrons? | [
"diacritics",
"metalloids",
"minerals",
"synthetics"
] | B | How metalloids behave in chemical interactions with other elements depends mainly on the number of electrons in the outer energy level of their atoms. Metalloids may act either like metals or nonmetals in chemical reactions. |
SciQ | SciQ-2651 | 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.
In the lungs, air is diverted into smaller and smaller passages called what? | [
"bronchi",
"ion channels",
"alveoli",
"ectoderm"
] | A | In the lungs, air is diverted into smaller and smaller passages, or bronchi. Air enters the lungs through the two primary (main) bronchi (singular: bronchus). Each bronchus divides into secondary bronchi, then into tertiary bronchi, which in turn divide, creating smaller and smaller diameter bronchioles as they split and spread through the lung. Like the trachea, the bronchi are made of cartilage and smooth muscle. At the bronchioles, the cartilage is replaced with elastic fibers. Bronchi are innervated by nerves of both the parasympathetic and sympathetic nervous systems that control muscle contraction (parasympathetic) or relaxation (sympathetic) in the bronchi and bronchioles, depending on the nervous system’s cues. In humans, bronchioles with a diameter smaller than 0.5 mm are the respiratory bronchioles. They lack cartilage and therefore rely on inhaled air to support their shape. As the passageways decrease in diameter, the relative amount of smooth muscle increases. The terminal bronchioles subdivide into microscopic branches called respiratory bronchioles. The respiratory bronchioles subdivide into several alveolar ducts. Numerous alveoli and alveolar sacs surround the alveolar ducts. The alveolar sacs resemble bunches of grapes tethered to the end of the bronchioles (Figure 39.10). In the acinar region, the alveolar ducts. |
SciQ | SciQ-2652 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
How did a vascular let plants grow? | [
"they could reproduce",
"they could conduct photosynthesis",
"they could bear fruit",
"they could grow taller"
] | D | The evolution of vascular tissue revolutionized the plant kingdom. Vascular tissue greatly improved the ability of plants to absorb and transfer water. This allowed plants to grow larger and taller. They could also liver in drier habitats and survive periods of drought. Early vascular plants probably resembled the fern in Figure below . |
SciQ | SciQ-2653 | aqueous-solution, solubility, phase
Whereas the IUPAC Gold Book defines a chemical reaction as:
A process that results in the interconversion of chemical species.
One aspect of solvation vs. reaction that may seem confusing is the solubility of ionic species. Even though $\ce{NaCl}$ becomes $\ce{Na+}$ and $\ce{Cl-}$ in an aqueous solution, this does not constitute a chemical reaction as defined above, and we say that $\ce{NaCl}$ is soluble in water. The same is true of your example of $\ce{H2SO4}$; even though it dissociates in water, it is not converted to a new chemical compound. One way to think of this is if you remove the solvent, the solute should typically resume to it's original form. From our previous example, if we evaporate the water from our aqueous solution of $\ce{Na+}$ and $\ce{Cl-}$, we just get the solid $\ce{NaCl}$ back.
Your examples of solubility in hydrochloric acid are a bit complex because that is a two-component system of water and $\ce{HCl}$. All of the compounds you discuss are water soluble and it doesn't matter if the $\ce{HCl}$ is there or not. One slight exception in your examples is ethylamine. Ethylamine itself is miscible with water, but many higher molecular weight amines are not water soluble, but are soluble in hydrochloric acid. In this case, the $\ce{H+}$ from $\ce{HCl}$ protonates the amine, making the hydrochloride salt. This is still an example of solubility however, as once you remove the solvent, you are left with the original compound, in this case the amine.
The following is multiple choice question (with options) to answer.
When a soluble compound dissolves, its constituent atoms, molecules, or ions disperse throughout what? | [
"gel",
"solvent",
"liquid",
"pigment"
] | B | When a soluble compound dissolves, its constituent atoms, molecules, or ions disperse throughout the solvent. In contrast, the constituents of an insoluble compound remain associated with one another in the solid. A soluble compound is a strong electrolyte if it dissociates completely into ions, a weak electrolyte if it dissociates only slightly into ions, and a nonelectrolyte if it dissolves to produce only neutral molecules. |
SciQ | SciQ-2654 | immunology, vaccination
Title: True or False: Vaccines are designed to protect against invaders that are encountered rarely, not all the time I read the following statement in this article:
Vaccines are designed to protect against invaders that are encountered
rarely - not all the time
Is it true? If yes, why? Not true. Vaccines were initially made for the highly contagious diseases that used to cause epidemics (which obviously means they were not rare).
The efficacy of a vaccine depends on multiple factors which includes adaptability of the pathogen.
The all-the-time encountered pathogen that the article is talking about is HIV; the reason for why no effective vaccine exists for it is because it has high mutation rate.
The following is multiple choice question (with options) to answer.
Many viral diseases can be prevented by giving people what? | [
"pesticides",
"vaccines",
"Lactose",
"cancers"
] | B | Many viral diseases can be prevented by giving people vaccines (see Figure below ). A vaccine is a substance that contains pathogens such as viruses. The pathogens have been changed in some way so they no longer cause disease. However, they can still provoke a response from the host’s immune system. This results in immunity, or the ability to resist the pathogen. Vaccines have been produced for the viruses that cause measles, chicken pox, mumps, polio, and several other diseases. |
SciQ | SciQ-2655 | human-anatomy
Title: Difference between Appendix and the Cecum? What's the difference between an appendix and a cecum, and what are their functions? In herbivores the Cecum is an area that stores plant matter and helps digest it via symbiotic bacteria. Carnivores have smaller Cecums because meat is easier to digest than plant matter. In humans the Cecum is also an anatomical landmark that delineates the change from small intestine (a digesting organ) to the large intestine (mostly a capacity/storage organ).
The Appendix is a small, previously thought "superfluous" fleshy worm-shaped organ at the junction between the small and large intestines. Recent research posits that the appendix is sort of a harbor for a person's gut flora that can re-populate the intestines should the existing bacteria die or get removed (diarrhea being the most common cause). It can also become infected, inflamed, and require surgery to remove (Appendicitis).
The following is multiple choice question (with options) to answer.
What purpose does the appendix serve in humans today? | [
"none",
"filters blood",
"digests food",
"work"
] | A | Structures like the human tail bone are called vestigial structures . Evolution has reduced their size because the structures are no longer used. The human appendix is another example of a vestigial structure. It is a tiny remnant of a once-larger organ. In a distant ancestor, it was needed to digest food. It serves no purpose in humans today. Why do you think structures that are no longer used shrink in size? Why might a full-sized, unused structure reduce an organism’s fitness?. |
SciQ | SciQ-2656 | neuroscience, physiology, neurophysiology, senses, olfaction
Title: Why does olfactory sensation need lateral inhibition? Why does olfactory sensation need lateral inhibition? If it's not helping in spatial discrimination then why is it needed? Don't we just smell the odour which is more concentrated?
My attempt: It is said that lateral inhibition is an important part of olfaction as it aids in odour discrimination by decreasing firing in response to background odours and differentiating the responses of olfactory nerve inputs in the mitral cell layer. But we also know that sensory perception is based on the pattern of receptors activated by the stimulus. So following questions arise:
Why don't background odours laterally inhibit the target odour? Isn't there more chance of inhibition of target odour being inhibited since its concentration is less? Here is the paper which directly answers your question.
Urban NN. Lateral inhibition in the olfactory bulb and in olfaction. Physiology & behavior. 2002 Dec 31;77(4):607-12.
A few salient points:
It is true that the spatial gradient of sensory attributes is not as clear in the olfactory bulb-neuronal topography as it is at other places with lateral inhibition, but lateral inhibition still seems to serve a similar purpose in all these cases, namely sharpening the perceived stimuli. It is not settled how is this "edge enhancement" brought about in a nontopographical system ( "...Specific inhibitory connections between groups of cells with similar receptive fields may allow for functional lateral inhibition in such nontopographic systems, but no evidence for such specificity has been provided in the olfactory system...").
Unlike say for example in the Retina, where lateral inhibition creates the on/off centres, the lateral inhibition in olfactory bulbs is more widespread. That is, the area inhibited is relatively more expansive. This fact, coupled with the highly localised excitation caused by odours, suggests that "....lateral inhibition will be most effective at suppressing signals with low spatial frequency, in other words, signals that involve activation of broad regions of the olfactory bulb...". This is what I assume was meant by your source while referring to background odours.
The following is multiple choice question (with options) to answer.
What is the bulb called in the frontal lobe that processes smells? | [
"olfactory bulb",
"sensory bulb",
"peripheral bulb",
"auditory bulb"
] | A | The frontal lobe is located at the front of the brain, over the eyes. This lobe contains the olfactory bulb, which processes smells. The frontal lobe also contains the motor cortex, which is important for planning and implementing movement. Areas within the motor cortex map to different muscle groups, and there is some organization to this map, as shown in Figure 35.22. For example, the neurons that control movement of the fingers are next to the neurons that control movement of the hand. Neurons in the frontal lobe also control cognitive functions like maintaining attention, speech, and decisionmaking. Studies of humans who have damaged their frontal lobes show that parts of this area are involved in personality, socialization, and assessing risk. |
SciQ | SciQ-2657 | newtonian-mechanics, newtonian-gravity, history
Newton's genius was also in realizing that this force is not limited to describing the dynamics of celestial bodies but also applies to the dynamics of objects falling to the Earth on ground. He could verify this by confirming that the acceleration of freely falling objects near the ground was in agreement with the prediction from his universal law of gravitation.
The following is multiple choice question (with options) to answer.
According to early accounts, newton was inspired to make the connection between falling bodies and astronomical motions when he saw an apple fall from a tree and realized that if the gravitational force could extend above the ground to a tree, it might also reach this? | [
"stars",
"horizon",
"sun",
"moon"
] | C | Figure 6.20 According to early accounts, Newton was inspired to make the connection between falling bodies and astronomical motions when he saw an apple fall from a tree and realized that if the gravitational force could extend above the ground to a tree, it might also reach the Sun. The inspiration of Newton’s apple is a part of worldwide folklore and may even be based in fact. Great importance is attached to it because Newton’s universal law of gravitation and his laws of motion answered very old questions about nature and gave tremendous support to the notion of underlying simplicity and unity in nature. Scientists still expect underlying simplicity to emerge from their ongoing inquiries into nature. |
SciQ | SciQ-2658 | gravity, astrophysics
Title: Does mass determine gravity or is it a predetermined quantity If Earth were to gain large enough mass, would it have enough gravitational force to hold the extra mass, or is there a predetermined magnitude of gravitational force for earth due to its location in space-time?
If not, would that mean that gravity depends on the intermolecular forces holding the mass together in space, which as a result only allow strongly bonded materials to have larger gravitational force? The gravitational force is always attractive (and never repulsive) so the extra mass cannot be expelled by gravity. From a classical newtonian point of view the magnitude of the gravitational force between two masses is given by the following equation:
$$ \mathbf{F} = -G \frac{m_1m_2}{\left|\mathbf{r_{12}}\right|^2}\mathbf{\hat{r}_{12}}$$
So you can see that there is no predetermined magnitude of the gravitational force. The magnitude depends only on the mass of the objects (i.e. the Earth) itself.
For the second part of your question it is important to realise that the force that binds atoms into molecules is not the gravitational force but the electromagnetic force. The former would be to small to bind atoms togheter and can be safely neglected in all situations that don't involve large masses (like the earth).
The intermolecular forces do however have an effect on the density of the materials and thus on the size of an object having a certain mass. However as you can see from the equation, the density doesn't play a role in the size of the gravitational force and only the mass $m$ is important. This means that if you would be able to increase the density of the materials that make up this planet and squeeze it into the size of a tennis ball you would still experience the same gravitational force.
The fact that stars have an upper limit on their masses could cause some confusion. However this stems from the fact that the heavier stars also shine brighter and that any increase in mass would only cause that mass to be blown away by the radiation pressure. This has nothing to do with gravitational force.
The following is multiple choice question (with options) to answer.
Gravitational force on a large scale dominates interactions between large objects because it is always what? | [
"vulnerable",
"attractive",
"ugly",
"suitable"
] | B | As the example implies, gravitational force is completely negligible on a small scale, where the interactions of individual charged particles are important. On a large scale, such as between the Earth and a person, the reverse is true. Most objects are nearly electrically neutral, and so attractive and repulsive Coulomb forces nearly cancel. Gravitational force on a large scale dominates interactions between large objects because it is always attractive, while Coulomb forces tend to cancel. |
SciQ | SciQ-2659 | evolution, mitochondria, eukaryotic-cells
Title: Why do mitochondria have a phospholipid bilayer? So, a thought came up and I couldn't find all that much info online, so I thought I'd ask some professionals here!
The endosymbiont theory states that: mitochondria came to be ingested by bigger prokaryotic cells about 1.8 bYa, and by chance of luck came to a mutualistic relationship.
Now, mitochondria are said to have been archaea, right? But the mitochondria in our cells have phospholipid bilayers, with ester bonds in them, like all eukaryotes, but when you look at archaea, you see that they have monolayers because of their ether bonds, with rings and all sorts of branching, which is what gives them that extremophile-acclaimed resistance.
Question is if the endosymbiont theory is so widely accepted and mitochondria are meant to be archeae, why do they not present a monolayer with ether bonds?
Thanks for your time! I think the question is based on a false premise:
Poster: Now, mitochondria are said to have been archaea, right?
Me: Wrong, I’m afraid.
The closest bacterial relation of mitochondria is Rickettsia, an alpha-Proteobacterium (see Lang et al. for a review). Rickettsia is a eubacterium, not an archaebacterium.
The confusion is probably due to misreading one of the two alternative theories of the origin of mitochondria. This is the theory that the host for the original mitochondrion was an archaebacterium (rather than a primitive nucleated eukaryote). In both theories this host aquired a eubacterium related to Rickettsia, which gave rise to the mitochondrion.
The following is multiple choice question (with options) to answer.
What two microorganisms have different membrane lipids? | [
"archaea and bacteria",
"microsporidia and bacteria",
"mesozoic and bacteria",
"algae and bacteria"
] | A | |
SciQ | SciQ-2660 | zoology, species-identification, entomology
Title: Identification of a segmented black insect in France
Found in the Lot department of southern France. I think this is some sort of soldier fly larva (family Stratiomyidae). That would explain lack of legs. There are thousands of species world wide, with both aquatic and terrestrial larvae, so it might be possible to narrow it down a bit more.
Image from bugguide.net for comparison:
Thanks to @bli for reminding me of dipteran larvae!
The following is multiple choice question (with options) to answer.
Sharing a phylum with insects, spiders, daddy-long-legs, scorpions, and ticks belong to what class? | [
"annelids",
"arachnids",
"mammals",
"reptiles"
] | B | Arachnids include spiders, daddy-long-legs, scorpions, and ticks. |
SciQ | SciQ-2661 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
What describes the amount of solute in a solution? | [
"solubility",
"tonicity",
"viscosity",
"frequency"
] | B | Tonicity Tonicity describes the amount of solute in a solution. The measure of the tonicity of a solution, or the total amount of solutes dissolved in a specific amount of solution, is called its osmolarity. Three terms—hypotonic, isotonic, and hypertonic—are used to relate the osmolarity of a cell to the osmolarity of the extracellular fluid that contains the cells. In a hypotonic solution, such as tap water, the extracellular fluid has a lower concentration of solutes than the fluid inside the cell, and water enters the cell. (In living systems, the point of reference is always the cytoplasm, so the prefix hypo- means that the extracellular fluid has a lower concentration of solutes, or a lower osmolarity, than the cell cytoplasm. ) It also means that the extracellular fluid has a higher concentration of water than does the cell. In this situation, water will follow its concentration gradient and enter the cell. This may cause an animal cell to burst, or lyse. In a hypertonic solution (the prefix hyper- refers to the extracellular fluid having a higher concentration of solutes than the cell’s cytoplasm), the fluid contains less water than the cell does, such as seawater. Because the cell has a lower. |
SciQ | SciQ-2662 | 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 layer above the mesophere called? | [
"stratosphere",
"troposphere",
"thermosphere",
"exosphere"
] | A | The mesosphere is the layer above the stratosphere. It rises to about 85 kilometers (53 miles) above the surface. Temperature decreases with altitude in this layer. |
SciQ | SciQ-2663 | units, si-units, metrology
Title: How units were defined? I was wondering how we humans can be sure that one meter is one meter and that one second is one second. Nowadays, except for the Kilogram, all other units are well defined using highly accurate techniques (frequency of atoms vibrations or stuff like that). But at the end all units are kind of related to each other and the definition of each unit is based on a combination of other units. There must be some viable sources that have constant measurable values that we used to define the basic units. What is those sources?
To explain more let's start with the meter. From wikipedia, the definition is: The metre is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. So here it is clear that the definition of a meter relies on the accuracy of how we define a second.
Now let's look at the second:
the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.
How is this period calculated? The sensor has probably some equations that imply transformations using other units like Kg etc...
Where does this loop stops?
EDIT:
I think I was a little bit mistaken. Not all units are directly related and there is 3 totally independent units which are : Time (second), Temperature (kelvin) and Mass (kilogram). Time and Temperature are well defined but Kilogram is still unclear. Every existing unit can be transformed into a combination of those three. It means that all units based on Kilogram are not absolute. In short, up until now, the $kg$ was arbitrary, but now people are trying to define it based on universal constants
There is a ongoing process to try and link all the units to universal constants.
This has been done already for the second (using Cesium) and the meter (using the speed of light in a vacuum)
However, the kilogram is a little less straightforward. An interesting read is SI units revision proposal.
It proposes to link the kg to the Plank constant $h$, but also to link Kelvin $K$ to the Stefan-Boltzman constant $k$ and more of these constructions.
The following is multiple choice question (with options) to answer.
The fundamental unit of time, the second, is based on what type of clock? | [
"atomic clock",
"gravity clock",
"eternal clock",
"quantum clock"
] | A | Figure 1.18 An atomic clock such as this one uses the vibrations of cesium atoms to keep time to a precision of better than a microsecond per year. The fundamental unit of time, the second, is based on such clocks. This image is looking down from the top of an atomic fountain nearly 30 feet tall! (credit: Steve Jurvetson/Flickr). |
SciQ | SciQ-2664 | organic-chemistry, bond
Title: Bond length comparison between two carbon atoms Why is the bond length of double and triple bonds between two carbon atoms shorter than the single bond length between two carbon atoms? In the case of a carbon-carbon single bond, 2 electrons are shared in the bond connecting the two carbon atoms. With a carbon-carbon double bond, 4 electrons are shared between the two carbon atoms and 6 electrons are shared in a triple bond. Having additional electrons between the two atoms 1) improves the bonding overlap (makes the bond stronger) between the two carbon atoms and 2) better screens the two carbon nuclei form each other.
Both of these factors, better bonding overlap and better nuclear screening, will allow the two carbon atoms to approach closer together. Consequently, the more electrons (or the more bonds) between two carbon atoms, the shorter the distance between them.
The following is multiple choice question (with options) to answer.
In a carbon triple bond, how many pairs of electrons are shared? | [
"one",
"four",
"two",
"three"
] | D | Carbon can form single, double, or even triple bonds with other carbon atoms. In a single bond, two carbon atoms share one pair of electrons. In a double bond, they share two pairs of electrons, and in a triple bond they share three pairs of electrons. Examples of compounds with these types of bonds are represented by the structural formulas in the Figure below . |
SciQ | SciQ-2665 | botany, plant-physiology, plant-anatomy
Title: Sporophyte and gametophyte
My textbook says that in both groups of seedless plants (vascular plants, non-vascular plants) the gametophyte is a free-living plant, independent of the sporophyte.
I don't understand this statement and am now wondering if the sporophyte and gametophyte are stages in a plant's lifecycle, or are they individual parts of the plant, or are the sporophyte and the gametophyte different plants altogether? Secondly, does this differ depending on the organism?
Different plants or different structures that make up the same organism? The sporophtye is the diploid stage in the life cycle. In comparison, with humans, you and I would be sporophytes.
The Gametophyte is the haploid stage in the life cycle. In comparison, with humans, spermatozoids and ovules are gametophytes.
The following is multiple choice question (with options) to answer.
What is the reproductive part of the plant? | [
"the flower",
"the core",
"the stem",
"the leaf"
] | A | |
SciQ | SciQ-2666 | atomic-physics
Title: What gives covalent bond its strength? I came across the following passage from Structure and Properties chapter of Morrison-Boyd Organic Chemistry:
What gives the covalent bond its strength? It is the increase in electrostatic attraction. In the isolated atoms, each electron is attracted by-and attracts-one positive nucleus;in the molecule, each electron is attracted by two positive nuclei.
However, I don't think it refers to the force holding each atom together. It rather, merely describes the increase in the electrostatic force of attraction between the electrons and the nuclei. I believe that bond strength is a measure of the difficulty in pulling apart the component atoms, not the electrons from the positive nuclei.
What exactly is the pattern or picture of the forces on the nuclei and the electrons, due to one another, that holds the component atoms together? (I am aware that the decrease in overall energy or increase in stability is definitely not a reason to account for the strength of covalent bond, but rather a consequence of the action of such forces.) It probably helps to define what a covalent bond really is. Covalent bonds occur when one or more Atomic Orbitals (AO) of the participating atoms constructively interact and form a (bonding) Molecular Orbital (MO). The figure below schematises the formation of a $\sigma_{ss}$ MO when two hydrogen atoms combine to form a dihydrogen molecule:
The following is multiple choice question (with options) to answer.
The attraction of an atom for the electrons of a covalent bond is its what? | [
"brightness",
"electronegativity",
"weight",
"hardness"
] | B | |
SciQ | SciQ-2667 | botany
Title: Do plants absorb toxins from the soil? Consider a plant like Aloe Vera that grows up in a toxic environment where the concentration of pesticides, and materials like lead, mercury, cadmium, arsenic etc is very high(e.g. Marshland dumping yard ). Would that mean that the extract from these plants would contain all these toxic elements. Not "all of them". But yes, plants suck up water from the soil, with everything dissolved in this water - nutrients, heavy metals, poisons. And also they breathe air, and absorb stuff via this route.
There probably are some toxins which will not enter the plant, because their molecules are too large and/or fragile. For example, should a plant root come in contact with snake venom, I cannot imagine that any venom will end up stored in the plant leaves.
Plants also have their own metabolism, so they will change/deactivate some toxins. I've seen claims that some plants "purify" formaldehyde, although I don't trust the sources enough to be sure of that.
But the smaller the poison molecule, and the less similar to stuff which is usually digested in nature, the more likely that it will enter the plant and stick around instead of being broken down. The heavy metals you mentioned are prime candidates. If they are present in the groundwater - or also lead from air pollution, before we banned leaded gasoline - they end up in plants, including food plants. And mushrooms are even more at risk.
Growing food near waste dumps is a known problem in farming, and sometimes makes the news, for example here:
http://bigstory.ap.org/article/mafia-toxic-waste-dumping-poisons-italy-farmlands
The following is multiple choice question (with options) to answer.
What substance do the leaves of plants take in from the environment? | [
"hydrogen",
"oxygen",
"carbon dioxide",
"acid rain"
] | C | |
SciQ | SciQ-2668 | Long answer: It sounds like the two coins in your example do not affect each other in any way. In other words, it sounds like the number of heads on one is independent of how many heads happen for the other. For any two random variables, whether independent or not, we do indeed have that $E[X+Y]=E[X]+E[Y]$. Furthermore, when the variables are independent, we also have that $E[XY]=E[X]E[Y]$. This allows us to reason as follows. \begin{align} Var[X+Y] &= E[((X+Y)-E(X+Y))^2]\\ &=E[(X-E[X]+Y-E[Y])^2]\\ &=E[(X-E[X])^2] +2E[(X-E[X])(Y-E[Y])] + E[(Y-E[Y])^2]\\ &=Var[X] + Var[Y] + 2 E[XY -XE[Y] -YE[X] + E[X]E[Y]]\\ &= Var[X] + Var[Y] + 2(E[XY] -E[X]E[Y] - E[X]E[Y] + E[X]E[Y])\\ &= Var[X] + Var[Y] + 2(E[X]E[Y] -E[X]E[Y] - E[X]E[Y] + E[X]E[Y])\\ &= Var[X] + Var[Y] +2 \cdot 0\\ &= Var[X] + Var[Y] \end{align} So the variance of the sum of independent random variables is the sum of their variance.
The following is multiple choice question (with options) to answer.
Controlled variables are kept what to prevent them from influencing the effects of the independent variable on the dependent variable? | [
"mechanical",
"fleeting",
"temporary",
"constant"
] | D | Scientific experiments involve controls , or subjects that are not tested during the investigation. In this way, a scientist limits the factors, or variables that can cause the results of an investigation to differ. A variable is a factor that can change over the course of an experiment. Independent variables are factors whose values are controlled by the experimenter to determine their relationship with an observed phenomenon. Dependent variables are the observed phenomenon, and change in response to the independent variable. Controlled variables are also important to identify in experiments. They are the variables that are kept constant to prevent them from influencing the effect of the independent variable on the dependent variable. |
SciQ | SciQ-2669 | paleontology
Title: How to start studying dinosaurs and pre-historic mammals/sea creatures I'm kind new to this hole thing of dinosaurs that I'm really interested in, are there any good books/websites/webpages to study the biology of pre-historic creatures? Dinosaurs, mammals, fishes, anything that is not alive anymore. Also, any good books about the history of how these species evolved and the history behind them would be appreciated. Here's what it takes to really study this: you need to go through the whole bachelor program for geoscientists, that includes fundamental geodynamics like plate tectonics, magmatism, volcanism, volcanic and metamorphic rocks and generally the cycles that make up earth's internal dynamics.
Then there is the huge field of external factors, like sediment geology (that's really complicated stuff), weathering and transport and how soils come to being, diagenesis and the structures sediments can form and their classifications. Role of the ocean (that's where it starts, before all) and the atmosphere, of course.
When through that, usually 4 semesters or so, you can start to specialize. For paleontolgy you need knowledge of earth history, of course, it's subdivision, and the conditions at certain times as far as they are known. Once that's done, then comes real paleontology: Animals (invertebrates and vertebrates), plants, and their development, biological evolution (that's frequently underrated, I find), taphonomy, ... For a sturdy base count another 2-4 semesters.
You may see that even a bunch of websites, maybe all of them together, cannot replace actual study. I am not aware of any site that even gives a reasonable overview of the field. Geoscience, and thus paleontology, touch many fields of natural science.
That said, when asked "How to learn about animal paleontology ?" I allways mention Micheal Benton, Vertebrate Paleontology. It needs a basic understanding of geoscience, evolution and skeleton anatomy. Functional morphology, phylogeny and an overview over sediment geology and earth history also won't harm, but you could give it a try. Some things are explained in between.
The following is multiple choice question (with options) to answer.
What branch of biology uses fossils to study life’s history? | [
"gerontology",
"paleontology",
"morphology",
"entomology"
] | B | Paleontology, another branch of biology, uses fossils to study life’s history (Figure 1.20). Zoology and botany are the study of animals and plants, respectively. Biologists can also specialize as biotechnologists, ecologists, or physiologists, to name just a few areas. This is just a small sample of the many fields that biologists can pursue. Biology is the culmination of the achievements of the natural sciences from their inception to today. Excitingly, it is the cradle of emerging sciences, such as the biology of brain activity, genetic engineering of custom organisms, and the biology of evolution that uses the laboratory tools of molecular biology to retrace the earliest stages of life on earth. A scan of news headlines—whether reporting on immunizations, a newly discovered species, sports doping, or a genetically-modified food—demonstrates the way biology is active in and important to our everyday world. |
SciQ | SciQ-2670 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
What occurs after gametes fuse and form a diploid zygote? | [
"transcription",
"electrolysis",
"reproduction",
"meiosis"
] | D | |
SciQ | SciQ-2671 | genetics, homework, human-genetics
Title: What are sex linked traits? Which of the two definitions of sex-linked trait is correct?
Traits controlled by genes present on the non-homologous region of sex chromosomes are called sex-linked traits.
Bodily traits controlled by genes present on the non-homologous regions of sex chromosomes are called sex-linked traits. Here by bodily traits I mean traits that are not involved with sex of an organism.
I read the first definition in the book Competition Science Visionand also from Instant notes genetics (page 163).
The following is an excerpt from the latter
Sex linkage is not displayed by genes which map to a small segment of X chromosome, the pseudoautosomal region, the part of X chromosome that pairs with Y chromosome in meiosis.
The second definition is made up but sounds potentially intuitive to me. The first definition is correct.
A sex-linked trait is a trait affected by a locus on a sex chromosome.
If you google sex-linked trait, you will find this same definition (not the exact same words) over and over again.
The definition of sex-linked trait is NOT restricted to traits that are not unrelated to primary or secondary sexual organs. Any phenotypic trait can be sex-linked as long as the causal locus is on a sexual chromosome.
The following is multiple choice question (with options) to answer.
What is a trait whose allele is found on a sex chromosome called? | [
"dimorphism - linked trait",
"genomic trait",
"gender trait",
"sex-linked trait"
] | D | A sex-linked trait is a trait whose allele is found on a sex chromosome. The human X chromosome is significantly larger than the Y chromosome; there are many more genes located on the X chromosome than there are on the Y chromosome. As a result there are many more X-linked traits than there are Y-linked traits. Most sex-linked traits are recessive. Because males carry only one X chromosome, if they inherit a recessive sex-linked gene they will show a sex-linked condition; there is no dominant allele to offset the recessive allele. |
SciQ | SciQ-2672 | energy, electron-affinity
Title: Why energy is released when an electron is added to a neutral atom? Question :
Why energy is released when an electron is added to a neutral atom?
I read somewhere
“When electrons are added to an atom, the increased negative charge puts stress on the electrons already there, causing energy to be released.”
I didn't understand What is stress and how energy is released due to stress? If the electron statistical distribution around the atomic kernel had been perfectly spherically symmetric, and if the electron occurance distribution had not mutually overlapped, than by the Gauss law of electrostatics, the net force between a neutral atom and an electron would have been zero.
But as neither of above conditions is true, a kernel charge is not fully screened off by electrons, acting as having a residual, "effective charge", what allows releasing energy by bounding an extra electron. See Slater rules.
An extra electron puts among other electrons some extra stress=mutual repulsion, what somewhat decreases this released energy.
As effective kernel charge and electron mutual repulsion ( classical and Pauli ones ) are 2 major factors affecting energies of electron orbitals in multi-electron atoms.
When the former factor is stronger, energy is released by an extra electron bounding, like for fluorine. And vice versa, like for helium.
The following is multiple choice question (with options) to answer.
What is required when electrons are removed from an atom, and released from the process when an electron is added? | [
"proton",
"fuel",
"nuclear",
"energy"
] | D | When electrons are removed from an atom, that process requires energy to pull the electron away from the nucleus. Addition of an electron releases energy from the process. |
SciQ | SciQ-2673 | newtonian-mechanics, angular-momentum, reference-frames, earth, moon
Title: Does Earth rotate around its geometrical axis OR the center of mass of Earth-Moon system? I just came to know about barycentre. What exactly is this? The Earth's spin is about its geometrical axis - that's the definition of that axis. This passes through the center of mass (barycenter) of the Earth itself.
Zooming out a bit, the Earth and the Moon both mutually orbit their mutual center of mass (barycenter), which lies inside the Earth but a bit off from its center. This is unrelated, at first brush to the rotation of either body about its own center of mass.
The following is multiple choice question (with options) to answer.
What do you call the angle of the earth's axis of rotation? | [
"axial tilt",
"horizontal tilt",
"vertical tilt",
"dynamic tilt"
] | A | Earth goes through regular changes in its position relative to the Sun. Its orbit changes slightly. Earth also wobbles on its axis of rotation. The planet also changes its axial tilt , the angle of its axis of rotation. These changes can affect Earth’s temperature. |
SciQ | SciQ-2674 | nomenclature
Title: IUPAC naming of purines and pyrimidines From Wikipedia, the IUPAC name for guanine is 2-amino-1,9-dihydro-6H-purin-6-one besides 2-amino-6-hydroxypurine and 2-aminohypoxanthine.
I have some difficulty understanding the 6H part in its name since there's a keto group at the 6th position unlike in cytosine (4-aminopyrimidin-2(1H)-one) where the 1H clearly refers to the hydrogen at the 1st position
What does 6H exactly mean? The original parent structure purine ($\ce{C5H4N4}$) has the maximum number of noncumulative double bonds for this kind of structure. Compared to an ideal unsaturated compound, however, purine has one extra hydrogen somewhere. The position of this extra hydrogen must be indicated. A few different isomers are possible; for example, the original parent structure could be 9H-purine.
In the given compound, a double bond of the original purine is missing. Thus, the parent structure is a bit more saturated with the equivalent of two additional hydrogen atoms ($\ce{C5H6N4}$). Such saturation is described using ‘hydro’ prefixes. The locants of the original indicated hydrogen and the two additional hydrogens are 1, 6, and 9. The indicated hydrogen gets the lowest locant, so the name of the unsubstituted parent structure is 6,9-dihydro-1H-purine.
In the substituted purin-6-one, however, the numbering is different because a double bond was removed to make room for the ketone. According to Rule P-58.2.3, the indicated hydrogen is placed at the position that will accommodate this principal characteristic group. Therefore, the name becomes 1,9-dihydro-6H-purin-6-one.
The following is multiple choice question (with options) to answer.
What kind of structure do purines have? | [
"helical stucture",
"double ring structure",
"single ring structure",
"triple ring structure"
] | B | Figure 3.31 A nucleotide is made up of three components: a nitrogenous base, a pentose sugar, and one or more phosphate groups. Carbon residues in the pentose are numbered 1′ through 5′ (the prime distinguishes these residues from those in the base, which are numbered without using a prime notation). The base is attached to the 1′ position of the ribose, and the phosphate is attached to the 5′ position. When a polynucleotide is formed, the 5′ phosphate of the incoming nucleotide attaches to the 3′ hydroxyl group at the end of the growing chain. Two types of pentose are found in nucleotides, deoxyribose (found in DNA) and ribose (found in RNA). Deoxyribose is similar in structure to ribose, but it has an H instead of an OH at the 2′ position. Bases can be divided into two categories: purines and pyrimidines. Purines have a double ring structure, and pyrimidines have a single ring. |
SciQ | SciQ-2675 | 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.
Photoautotrophs use what energy source to self-manufacture their own food? | [
"chlorophyll",
"air",
"light",
"water"
] | C | every organism uses to power its metabolism. In brief, the energy of sunlight is captured and used to energize electrons, which are then stored in the covalent bonds of sugar molecules. How long lasting and stable are those covalent bonds? The energy extracted today by the burning of coal and petroleum products represents sunlight energy captured and stored by photosynthesis almost 200 million years ago. Plants, algae, and a group of bacteria called cyanobacteria are the only organisms capable of performing photosynthesis (Figure 8.2). Because they use light to manufacture their own food, they are called photoautotrophs (literally, “self-feeders using light”). Other organisms, such as animals, fungi, and most other bacteria, are termed heterotrophs (“other feeders”), because they must rely on the sugars produced by photosynthetic organisms for their energy needs. A third very interesting group of bacteria synthesize sugars, not by using sunlight’s energy, but by extracting energy from inorganic chemical compounds; hence, they are referred to as chemoautotrophs. |
SciQ | SciQ-2676 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
What is the process of getting oxygen into the body & releasing carbon dioxide called? | [
"precipitation",
"photosynthesis",
"perspiration",
"respiration"
] | D | The process of getting oxygen into the body and releasing carbon dioxide is called respiration. |
SciQ | SciQ-2677 | species-identification, botany, ecology, trees
Title: Identifying a shrub with unusual "many shoots" growth behavior While recently hiking in the southern mountains of New Hampshire, we came across a plant, and some of them were exhibiting what we interpreted to be a disease, or least unusual growth. On some of the nodes, there were a large number of extra stalks:
On each plant, the number and locations of these things varied, and not all of them had it. And we first assumed it was some ivy, or parasite, or separate plant, but it seemed pretty clear to us that it was coming right from the same branch.
We soon saw there were dead versions of this plant, and all of them had this "extra shoot" variation:
So we reasoned that no matter what this thing was -- natural variation or some kind of disease -- it was killing the plants.
Google image search was no help. It possibly identified the plant as a "viburnum", but was unable to help with the growth.
Anyone know what plant this is, or what this growth behavior is the result of? Possibly an example of a "Witch's Broom."
Witch's Broom is a deformity in plants (typically woody species) which typically causes dense patches of stems/shoots to grow from a single point on the plant. The name comes from the broom-like appearance of the stems.1
Witch's broom may be caused by many different types of organisms, including fungi, oomycetes, insects, mistletoe, dwarf mistletoes, mites, nematodes, phytoplasmas, or viruses.2
Sources:
1. Wikipedia
2. Book of the British Countryside. Pub. London : Drive Publications, (1973). p. 519
Image1. Gardeningknowhow.com
Image2. Iowa state University
The following is multiple choice question (with options) to answer.
What are plants that grow where people don't want them to and can take up space and use resources which hinders growth of more desirable plants? | [
"weeds",
"shrubs",
"grasses",
"native plants"
] | A | We obviously can’t live without plants, but sometimes they cause us problems. Many plants are weeds. Weeds are plants that grow where people don’t want them, such as gardens and lawns. They take up space and use resources, hindering the growth of more desirable plants. People often introduce plants to new habitats where they lack natural predators and parasites. The introduced plants may spread rapidly and drive out native plants. Many plants produce pollen, which can cause allergies. Plants may also produce toxins that harm human health (see Figure below ). |
SciQ | SciQ-2678 | phase, hydrogen, pressure
Title: At what pressure will hydrogen start to liquefy at room temperature? I want to increase a fixed-size object's internal gas pressure by generating hydrogen in it, but I could not find the proper phase diagram for it. So I am wondering how high pressures I can get. $\ce{H2}$ cannot be liquified at room temperature, whatever the pressure. Generally speaking, all gases can only be liquified when the temperature is under its critical value.
The following is multiple choice question (with options) to answer.
Unlike ammonia, oxygen cannot be liquefied at room temperature because its what is below room temperature? | [
"leading temperature",
"critical temperature",
"particular temperature",
"relaxed temperature"
] | B | Check Your Learning Ammonia can be liquefied by compression at room temperature; oxygen cannot be liquefied under these conditions. Why do the two gases exhibit different behavior? Answer: The critical temperature of ammonia is 405.5 K, which is higher than room temperature. The critical temperature of oxygen is below room temperature; thus oxygen cannot be liquefied at room temperature. |
SciQ | SciQ-2679 | ros, rostopic, ros-indigo, joint-state
I know this is documented somewhere more officially - I'll try to get a link.
As gvdhoorn mentioned, I made a mistake here, either the gripper joints are there, or the other joints are there.
This is expected behavior. See this Wiki for the reference.
The following is multiple choice question (with options) to answer.
What occurs at joints? | [
"respiration",
"digestion",
"nothing",
"body movements"
] | D | Movements of the body occur at joints. Describe how muscles are arranged around the joints of the body. |
SciQ | SciQ-2680 | botany, plant-physiology, ecology, virology, host-pathogen-interaction
Note about symbiosis - comes in reaction to @Gerhard's comment
Different authors use the word symbiosis differently. From wikipedia:
The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).4 After 130+ years of debate,5 current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (i.e. symbiosis = all species interactions), with the restrictive definition no longer used (i.e. symbiosis = mutualism)
The following is multiple choice question (with options) to answer.
What is the term for a symbiotic relationship in which the parasite benefits while the host is harmed? | [
"pathology",
"infection",
"parasitism",
"reciprocity"
] | C | Parasitism is a symbiotic relationship in which one species (the parasite ) benefits while the other species (the host ) is harmed. Many species of animals are parasites, at least during some stage of their life. Most species are also hosts to one or more parasites. |
SciQ | SciQ-2681 | electromagnetism, charge, mass, radioactivity
Title: Why does beta particles deviate more than alpha particles? So two figures are given in my book,
One is Deflection of radioactive radiations in magnetic field
and the other is deflection of radiations in an electric field
The following is multiple choice question (with options) to answer.
Alpha particles, beta particles, and gamma particles are major types of what? | [
"sound waves",
"microscopy",
"visible light",
"radioactivity"
] | D | The major types of radioactivity include alpha particles, beta particles, and gamma rays. |
SciQ | SciQ-2682 | growth-media
Title: Is it essential to add cholesterol to agar or liquid culture for C. elegans? In preparing agar plates with NGM, and also liquid cultures for growing c elegans, how essential is the addition of cholesterol and heavy metals? I have prepared both. I can't notice any obvious difference and I hate having to add all these supplements.
I'm using yeast extract and peptone as the primary components of the base.
Isn't this just supposed to be a moist semi-soft substrate for them to crawl around, their nutrients come from the bacteria they eat. C. elegans needs cholesterol, but can't make it. Since bacteria don't make cholesterol either, the food bacteria aren't a source. As explained in the linked paper, lack of cholesterol affects normal development.
The following is multiple choice question (with options) to answer.
What do obligate aerobes need to live? | [
"acid",
"blood",
"oxygen",
"dioxide"
] | C | Organisms that are obligate aerobes need oxygen to live. That is, they use oxygen as a terminal electron acceptor while making ATP (see the “Cellular Respiration” concept). Humans are obligate aerobes, and so are Mycobacterium tuberculosis bacteria. M. tuberculosis causes tuberculosis (TB). Obligate aerobes are found only in places with molecular oxygen. |
SciQ | SciQ-2683 | mass, measurements
Title: How precise can current technologies measure the mass of an object? Masses of various objects are listed on this wikipedia page: Orders of magnitude (mass). For example, mass of an HIV-1 virus is on the order of 1 femtogram.
Are these data actually measured (which I really doubt), or calculated?
What is the most precise measurement technique we have to measure the mass of an object? The most precise measurement of the mass of an electron was reported by Sturm et al in Nature 506, 467–470 (27 February 2014), quoting a relative precision of $3\times 10^{-11}$, meaning they determined the mass to better than $3\times 10^{-41}~\rm{kg}$.
If that is not the best, at least it gives you an upper bound...
Note that if you could weigh such a small mass directly with scales on earth, the force would be equivalent to the gravitational pull of a mosquito (mass 2.5 mg) on a grain of sand (0.7 mg) at a distance of about 6 million kilometers - about 17 times the distance to the moon...
Astonishing.
Acknowledgement: CuriousOne's comment got me thinking about the measurement of the mass of the electron, and led me to the above analysis.
The following is multiple choice question (with options) to answer.
What is the standard measurement for mass? | [
"volume",
"grams",
"BMI",
"calories"
] | B | You’ve probably been using a ruler to measure length since you were in elementary school. But you may have made most of the measurements in English units of length, such as inches and feet. In science, length is most often measured in SI units, such as millimeters and centimeters. Many rulers have both types of units, one on each edge. The ruler pictured below has only SI units. It is shown here bigger than it really is so it’s easier to see the small lines, which measure millimeters. The large lines and numbers stand for centimeters. Count the number of small lines from the left end of the ruler (0.0). You should count 10 lines because there are 10 millimeters in a centimeter. |
SciQ | SciQ-2684 | species-identification, botany
Weakley (2015) "Flora of the Southern and Mid-Atlantic States"
1 Leaflets 3, toothed, lobed, or entire; shrub or vine.
2 Fruits pubescent or papillose; leaflets entire, coarsely toothed, undulate, or round-lobed; lower surfaces of leaflets either velvety puberulent, sometimes becoming glabrate in age (T. pubescens) or glabrous (glabrescent or rarely pilose beneath) but with prominent tufts of tannish hairs present in the vein axils (T. radicans var. radicans).
3 Leaves sparsely pubescent (rarely pilose beneath), the apex and the lobes (if present) generally acute to acuminate; drupes papillose, scabrous or puberulent; plant a high-climbing vine or stoloniferous shrub; [of mesic, swampy, or dry habitats].......... T. radicans var. radicans
3 Leaves velvety puberulent (sometimes becoming glabrate in age), the apex and the lobes (if present) generally obtuse to broadly acute; drupes pubescent (becoming glabrate); plant a stoloniferous shrub; [of dry habitats, especially sandhills] ............. T. pubescens
2 Fruits glabrous (or very sparsely pubescent); leaflets coarsely toothed or notched (rarely entire); lower surfaces of leaflets glabrous to pubescent, but without tufts of tannish hairs in the vein axils.
The following is multiple choice question (with options) to answer.
What do you call the state in which a plant slows down cellular activities and may shed its leaves? | [
"recession",
"dormancy",
"germination",
"hibernation"
] | B | In biomes with cold climates, plants may adapt by becoming dormant during the coldest part of the year. Dormancy is a state in which a plant slows down cellular activities and may shed its leaves. Animals also adapt to cold temperatures. One way is with insulation in the form of fur and fat. This is how the polar bears in Figure below stay warm. |
SciQ | SciQ-2685 | The left-hand side of the equation as given is the rate of change of population, divided by the population; that is, it is the relative rate of increase. In exponential growth, this would equal a constant: $$\displaystyle\frac{1}{P}\frac{dP}{dt} = B$$. B here would be the growth rate; calling it the (initial) birth rate (births per year per animal, say) makes sense. (It’s the $$R_0$$ mentioned above.) The model has been modified in the simplest possible way, by reducing the growth rate linearly as the population grows. So K is actually the rate at which the “birth rate” is diminished as population increases.
Doctor Anthony answered this one, this time using the actual population as the variable, rather than a proportion:
We start with the following equation:
dp/dt = p(b - kp)
Rearranging the equation so that p is on the left and t is on the right, we get:
dp
-------- = dt
p(b - kp)
The same method of solution applies as above, but the partial fractions are a little more complicated:
Use partial fractions for the left hand side:
1 A B
--------- = --- + ------
p(b - kp) p b - kp
1 = A(b - kp) + Bp
Then:
p = 0 gives 1 = Ab and so A = 1/b
p = b/k gives 1 = Bb/k and so B = k/b
The left hand side can then be written:
1 k
[--- + ---------] dp = dt
bp b(b - kp)
Integrating $$\displaystyle\int\left(\frac{1}{bp} + \frac{k}{b(b-kp)}\right)dp = dt$$, we get
(1/b)[ln(p) - ln(b - kp)] = t + constant
ln[p/(b - kp)] = bt + constant
p/(b - kp) = Ae^(bt) where A is a constant
The following is multiple choice question (with options) to answer.
Is the rate of population growth increasing or decreasing? | [
"increasing",
"preventing",
"Vanishing.",
"suggesting"
] | A | As the human population continues to grow, different factors limit population in different parts of the world. Space, clean air, clean water, and food to feed everyone are limiting in some locations. Worldwide though, human ingenuity has not placed a limit on the population. Not only does the population increase, the rate of population growth increases. |
SciQ | SciQ-2686 | human-biology, digestive-system, immune-system, microbiome
All of these immune cells also respond to diffused chemical signals called cytokines. These molecules are secreted by some cells and are received by receptors on the host cells. Sometimes the secretion is by another immune cell, sometimes it is from a non-immune system host cell, and sometimes these molecules can be secreted by the bacteria, fungi, or worms themselves.
Depending on the chemical signals that are secreted, and how the cells are interacting at the time of the message, and which cells are receiving the message, will determine the response to the message. It is contextual. Think of the phrase "You're killing me." If someone says it, while laughing, to a good friend who is telling jokes, it means one thing. If it is screamed as someone is being choked by an attacker, it means something very different.
To summarize, the immune cells are surveilling the environment and trying to pick up what is friend and what is foe and they try to respond accordingly.
Over time and coevolution, our microbiomes have developed ways of communicating with our immune system to let it know that these microbes do not mean any harm. They are able to "train" the immune cells using chemical signaling to temper the immune systems response to them (15), and this is how they are able to coexist within our body and with an immune system that is constantly on seek an destroy missions. Also because of the mucus, our microbiome usually isn't in direct contact with our cells, so it is a different kind of interaction than if an infecting pathogen were to breech the barriers and gain access to sterile areas where no bacteria or fungi should be found, and as a result, the immune system reacts differently.
The following is multiple choice question (with options) to answer.
What does the human protein cytokine help fight? | [
"toxins",
"mutations",
"infections",
"parasites"
] | C | Bacteria are modified to produce the human protein cytokine. This is a protein that helps fight infections. |
SciQ | SciQ-2687 | newtonian-gravity, angular-momentum, orbital-motion, conservation-laws, celestial-mechanics
Title: What is the ultimate "goal" of two particles in a gravitational field?
What is the ultimate "goal" of two particles in a gravitational field?
Will the particles eventually occupy the same point at the same time if nothing stops them?
What stops them from achieving the ultimate "goal"? The ultimate goal of anything in the universe (anything which is around conservative forces) would be to reach a position of lower potential.
So in the case of two particles in a gravitational field, they'd try to have a configuration where they would have the lowest gravitational potential between them, and hence they would move towards each other. (If we assume potential at infinity to be zero!)
The ultimate goal would be for their center of mass to occupy the same place, but that of course is stopped by their repulsion. ( the force which stops two bodies from passing through each other.) This is their least Potential Energy configuration.
The following is multiple choice question (with options) to answer.
What is the goal of science? | [
"gain scholarships",
"improve life expectancy",
"increase knowledge",
"improve knowledge"
] | C | The Hubble space telescope shows that technology and science are closely related. Technology uses science to solve problems, and science uses technology to make new discoveries. However, technology and science have different goals. The goal of science is to answer questions and increase knowledge. The goal of technology is to find solutions to practical problems. Although they have different goals, science and technology work hand in hand, and each helps the other advance. Scientific knowledge is used to create new technologies such as the space telescope. New technologies often allow scientists to explore nature in new ways. |
SciQ | SciQ-2688 | energy, ideal-gas
Title: Few Questions regarding Translational Kinetic energy of a ideal gas molecule The translational kinetic energy of an ideal gas molecule is 3/2KT. In our physics class, the teacher brought up a question about where the has molecule will stop. he equated 3/2KT to ½MV2 . In the question temperature was constant.
If this gas molecule is moving up from the surface of the earth with 3/2KT kinetic energy why will it stop after reaching a height "h"? if temperature is constant then Kinetic energy is also constant. The molecule should never stop imo. But the teacher just uses the change in KE = change in PE and gets height. Your teacher is making a critical error in trying to teach you about the relation between temperature and kinetic energy this way. First of all, temperature is generally not well-defined for small systems like one particle, as it is a statistical quantity derived from the properties of large ensembles.
But putting that aside and accepting the translational kinetic energy of an ideal gas particle as $\frac{1}{2}kT$, this question is still ludicrous. The temperature could not possibly be constant, as the kinetic energy of the particle coming to rest is not constant. The reason the kinetic energy changes in the gravitational field is due to the work done by gravity on the massive particle when bringing it to rest. In the case that gravity were to actually bring the particle fully to rest, you could argue that the particle effectively has reached a temperature of absolute zero. Now, there are more nuanced and technical problems with this picture, but that is missing the point here. It is also possible that you mistook the teacher to be saying the temperature was fixed when it really wasn’t, as there is no way for the temperature so-defined can remain unchanged when the kinetic energy is clearly being lost.
The following is multiple choice question (with options) to answer.
What is the temperature where molecular motion stops? | [
"absolute zero",
"Absolute Freezing",
"mean zero",
"Final Zero"
] | A | Absolute zero is the temperature where molecular motion stops and is the lowest possible temperature. |
SciQ | SciQ-2689 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
Early blastomeres can form what if isolated? | [
"lesions",
"cancer",
"a complete embryo",
"tumors"
] | C | |
SciQ | SciQ-2690 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
What component of an organism, made up of many cells, in turn makes up an organ? | [
"molecules",
"muscles",
"epidermis",
"tissues"
] | D | |
SciQ | SciQ-2691 | inorganic-chemistry, reaction-mechanism, ions
$\ce {M^+.Cry (g) + M^- (g) -> M^+.Cry M^- (s)}$.
For $\ce {M = Na}$, the $\ce {\Delta H}$ and $\ce {\Delta G}$ for the above process are $\ce {-323 kJ/mol}$ and $\ce {-258 kJ/mol}$ respectively $\ce {^3}$.
Preparation of the alkalide
$\ce {Na^-}$, $\ce {K^-}$, $\ce {Rb^-}$, and $\ce {Cs^-}$ anions are stable both in suitable solvents and in crystalline solids$\ce {^3}$. The latter can be prepared either by cooling a saturated solution $\ce {^4}$ or by rapid solvent evaporation.
The principal difficulty in preparation of crystalline salts containing alkalide ions by the method of cooling a saturated solution is the low solubility of these alkali metals in the amine and ether solutions $\ce {^3}$. Without a sufficiently large concentration of the metal dissolved in solution, precipitation of the solid upon cooling would be insignificant. This difficulty was resolved by the use of crown-ether and cryptand complexes, such as those of [18]crown-6 and [2.2.2] cryptand] $\ce {^3}$. The complexating agent complexes with $\ce {M^+}$ , shifting the equilibrium (1) far to the right, significantly increasing the concentrations of the dissolved metal ions.
(1) $\ce { 2M (s) -> M^+ (sol) + M^- (sol)}$
(2) $\ce { M^+ (sol) + Cry (sol) -> M^+.Cry}$
The following is multiple choice question (with options) to answer.
What form do alkali metals take at room temperature? | [
"liquid",
"compound",
"gas",
"solid"
] | D | Alkali metals are all solids at room temperature. |
SciQ | SciQ-2692 | agriculture
Title: What does "permanent field" mean in agriculture? I am reading a book that in a paragraph talks about the agricultural methods used in prehistoric Finland.
The further north and east, the more extensive the amount of
burn-beat cultivation, which was a far from primitive form of
agriculture. The yield was many times higher (twenty- to thirty-fold)
than on permanent fields (five- to ten-fold), and there were multiple
varieties of the technique
A history of Finland by Henrik Meinander.
One of them is burn-beating. Like I understand, in burn-beating people cut down the trees in the forests and burn the topsoil. This way they can use that soil for 3 to 6 years for cultivation.
The other method is permanent field. I have searched the internet and the result I got was "permanent crops", like here. In which case people planted trees once in a field and harvested them multiple times.
But in another research about prehistoric Finland it was saying:
The site of Orijärvi shows that permanent field cultivation, with
hulled barley as the main crop was conducted from approximately cal AD 600 onwards.
The following is multiple choice question (with options) to answer.
What is the cutting and burning trees to clear land for farming called? | [
"cut-and-smoke farming",
"drop-and-blaze agriculture",
"slash-and-burn agriculture",
"reduce-and-ignite agriculture"
] | C | Cutting and burning trees to clear land for farming is called slash-and-burn agriculture. How does this affect the atmosphere?. |
SciQ | SciQ-2693 | particle-physics, mass, neutrinos, sun
Title: Solar Neutrino Problem I am not sure if this has been asked recently, but has there been any headway into solving the solar neutrino problem? I recently completed the Particle Physics for non-Physicists by Professor Stephen Pollack. It is from 2006 and I was wondering if the issue had been solved yet.
In it he stated that 66% of the expected neutrinos were being detected. He postulated that the neutrinos could possibly oscillate between types. However wouldn't a tau neutrino and muon neutrino be detected as well?
However wouldn't a tau neutrino and muon neutrino be detected as well?
Yes, and an experiment that led to a Nobel prize was done
. All of the solar neutrino detectors prior to SNO had been sensitive primarily or exclusively to electron neutrinos and yielded little to no information on muon neutrinos and tau neutrinos.
In 1984, Herb Chen of the University of California at Irvine first pointed out the advantages of using heavy water as a detector for solar neutrinos.Unlike previous detectors, using heavy water would make the detector sensitive to two reactions, one reaction sensitive to all neutrino flavours, the other reaction sensitive to only electron neutrino. Thus, such detector can measure neutrino oscillations directly.
....
On 18 June 2001, the first scientific results of SNO were published, bringing the first clear evidence that neutrinos oscillate (i.e. that they can transmute into one another), as they travel in the sun. This oscillation in turn implies that neutrinos have non-zero masses. The total flux of all neutrino flavours measured by SNO agrees well with the theoretical prediction. Further measurements carried out by SNO have since confirmed and improved the precision of the original result.
Italics mine.
The following is multiple choice question (with options) to answer.
What is the name of the scientist who named neutrinos? | [
"Einstein",
"Gibbs",
"enrico fermi",
"Schrodinger"
] | C | The neutrino is a particle emitted in beta decay that was unanticipated and is of fundamental importance. The neutrino was not even proposed in theory until more than 20 years after beta decay was known to involve electron emissions. Neutrinos are so difficult to detect that the first direct evidence of them was not obtained until 1953. Neutrinos are nearly massless, have no charge, and do not interact with nucleons via the strong nuclear force. Traveling approximately at the speed of light, they have little time to affect any nucleus they encounter. This is, owing to the fact that they have no charge (and they are not EM waves), they do not interact through the EM force. They do interact via the relatively weak and very short range weak nuclear force. Consequently, neutrinos escape almost any detector and penetrate almost any shielding. However, neutrinos do carry energy, angular momentum (they are fermions with half-integral spin), and linear momentum away from a beta decay. When accurate measurements of beta decay were made, it became apparent that energy, angular momentum, and linear momentum were not accounted for by the daughter nucleus and electron alone. Either a previously unsuspected particle was carrying them away, or three conservation laws were being violated. Wolfgang Pauli made a formal proposal for the existence of neutrinos in 1930. The Italian-born American physicist Enrico Fermi (1901–1954) gave neutrinos their name, meaning little neutral ones, when he developed a sophisticated theory of beta decay (see Figure 31.18). Part of Fermi’s theory was the identification of the weak nuclear force as being distinct from the strong nuclear force and in fact responsible for beta decay. |
SciQ | SciQ-2694 | geophysics, plate-tectonics, arctic, ocean-ridge
Title: Why is there a bend in the Lomonosov Ridge? Why is there a bend in the Lomonosov Ridge?
This is a supplementary question to that asked by Sabre Tooth in What is the tectonic explanation for parallel ridges in the Arctic ocean Firstly, just including the map of the ridges, in particular the Lomonosov Ridge and the characteristic bend visible near the North Pole:
Image Source
Based on magnetic anomaly observations, Cochran et al. (2006) theorise that the bend visible in the Lomonosov Ridge formed over a 3-6 million year period where there may have been a non-transform offset connecting a seafloor spreading region in the west Eurasian Basin with the continued continental rifting to the east, that continued propogating eastward resulting in the area of oblique spreading.
According to the Cochran et al. article, the tectonic spreading occurred around 53-56 million years ago, which according to models from Shephard et al. (2013) was associated with the opening of the Eurasia Basin.
Note: Cochran et al. refer to the eastern side as that on the Siberian side of the 'bend' and consequently, the western side being in the direction of North America.
Specifically, Cochran et al. conclude that
The prominent bend in the Lomonosov Ridge near the Pole corresponds to an approximately 50 km offset in Marvin Spur. The offset of the marginal ridge is consistent with the presence of a short extensional segment located between two long transforms.
References
Cochran et al. 2006, Morphology and structure of the Lomonosov Ridge, Arctic Ocean, Geochemistry, Geophysics, Geosystems
Shephard et al. 2013, The tectonic evolution of the Arctic since Pangea breakup:
Integrating constraints from surface geology and geophysics
with mantle structure Earth-Science Reviews
The following is multiple choice question (with options) to answer.
What creates a new seafloor at the mid-ocean ridge? | [
"earthquake",
"magma",
"hurricane",
"glaciers"
] | B | Magma at the mid-ocean ridge creates new seafloor. |
SciQ | SciQ-2695 | organic-chemistry, nomenclature
Is this labeling system limited to $sp^3$-hybridized carbon atoms? I do not see anything in the definitions that exclude $sp^2$- or $sp$-hybridized carbon atoms. Nor have I seen or read anything that explicitly excludes these atoms. However, the images in textbooks and around the web all show and discuss only $sp^3$-hybridized carbon atoms in this context. Are the following valid?
The central atom in propene $\ce{CH3 -}{\bf\color{red}{\ce{C}}}\ce{H=CH2}$ is a $2^\circ$ carbon atom because it is bonded to two other carbon atoms.
The carbon atoms in acetylene $\ce{HC#CH}$ are $1^\circ$ carbon atoms because they each are bonded to one other carbon atom.
The ipso carbon in toluene $\ce{C6H5CH3}$ (the carbon atom where the $\ce{CH3}$ is attached) is a $3^\circ$ carbon atom because it is bonded to three other carbon atoms. To best of my knowledge, the classification primary to quaternary is used for discussing reactivity of hydrocarbons, i.e. alkanes. There the number of substituents matters, as it governs carbocation stability, steric hindrance, etc...
In all other cases, the electronic structure of the molecule rules the reactivity. As you mentioned alkenes, alkynes or aromates, there it makes no sense to discuss such subtle effect as number of neighbouring carbons, when you have $\pi$-system at hand.
The IUPAC Gold Book entry for alkyl groups supports this distinction:
The groups $\ce{RCH2}$, $\ce{R2CH}\ (\ce{R} ≠ \ce{H})$, and $\ce{R3C}\ (\ce{R} ≠ \ce{H})$ are primary, secondary and tertiary alkyl groups, respectively.
The following is multiple choice question (with options) to answer.
What are hydrocarbons that contain only single bonds between carbon atoms called? | [
"carcinogenic hydrocarbons",
"unsaturated hydrocarbons",
"saturated hydrocarbons",
"caloric hydrocarbons"
] | C | Saturated hydrocarbons are hydrocarbons that contain only single bonds between carbon atoms. They are the simplest class of hydrocarbons. They are called saturated because each carbon atom is bonded to as many hydrogen atoms as possible. In other words, the carbon atoms are saturated with hydrogen. You can see an example of a saturated hydrocarbon in the Figure below . In this compound, named ethane, each carbon atom is bonded to three hydrogen atoms. In the structural formula, each dash (-) represents a single covalent bond, in which two atoms share one pair of valence electrons. |
SciQ | SciQ-2696 | soil-science
Title: How does humanure make soil "fluffier"? This BBC article says biosolids make soil "fluffier", among other benefits. How?
Adding humanure also changes soil structure, making it more resilient, preventing erosion and balancing out moisture, says Moss. It makes dirt fluffier, so water passes through easier. Conversely, in drought conditions, this also helps it retain water. The less compact soils are also softer, enabling seedlings to take faster and grow stronger roots, producing better yields. What are Biosolids and how do they work?
a biosolid is a product of the sewage treatment processes and is a semi-solid sludge of organic matter, nutrient-rich organic compounds. Here I list several reasons as to why biosolids would make the soil 'fluffier' and and better
As I said earlier biosolids are typically made out of organic matter, organic matter is carbon-based and biosolids are usually biological material (decomposed feces, urine and et cetera).
If you are not familiar with the normal decomposition processs it is a biological material (banana, apple, feces and et cetera) that is decomposed by microbes, molds, fungi and etc
biosolids are biological and/or organic material so what I just stated above applies to biosolids as well
Think of what you flush down a toilet or what goes down a sewer drain, are those things carbon based and biological? (human feces is an organic-compound and it goes in the sewers)
So now we know that biosolids are like other organic-compounds, how does this maker the soil fluffier. When something undergoes decomposition it turns into fresh brand-new soil, and quite obviously this new soil would be much more higher-quality and better than over-used old soil.
Here it states that organic material in a landfill produce gases due to decomposition so it makes sense that the same process would happen underground where microbial decomposition can release gases in the soil thus making the soil fluffier
So I can conclude that biosolids do, in fact help soil and make it fluffier and better.
The following is multiple choice question (with options) to answer.
The presence of what makes soil hold together more tightly and enables it to hold more water? | [
"glass",
"salt",
"sand",
"clay"
] | D | Soils with lots of very small spaces are water-holding soils. When clay is present in a soil, the soil holds together more tightly. Clay-rich soil can hold more water. |
SciQ | SciQ-2697 | 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 kind of anatomical structure consists of several types of tissues that together carry out particular functions? | [
"frame",
"system",
"valve",
"organ"
] | D | |
SciQ | SciQ-2698 | biochemistry, photosynthesis
The general question of the production of oxalate is discussed in the following review: Annu. Rev. Plant Biol. 2005. 56:41–71, from which it appears that this is not the case. The actual pathway of production appears to be subject to some disagreement, with most reports tending to the view that ascorbic acid is the precursor but others suggesting that the glycolate pathway operates in certain species.
I do not think this is too surprising if one considers that PEP carboxylase and oxalate formation each occur in (quite different) specialized cells. (And this is a general consideration regarding C4 plant metabolism: it has evolved in a specialized structures for a specific purpose, and is regulated according to the diurnal requirements of the plant.)
The following is multiple choice question (with options) to answer.
How many pathways do plants have for carbon fixation? | [
"five",
"eleven",
"two",
"three"
] | D | Plants have evolved three pathways for carbon fixation. |
SciQ | SciQ-2699 | electromagnetism, electric-circuits, electricity, electric-current
Title: What exactly is AC Amperes In the case of AC, electrons don't go anywhere. So what exactly are amperes in the case of AC current? It is supposed to be the measure of AC current, But obviously, I would argue that since electrons don't really go anywhere in an AC circuit, current as such cannot be measured.
So how do instruments measure amperes in an AC current? I understand that we could measure AC power within a circuit as the force with which the electrons vibrate within a circuit. So, lower the vibration, lower the wattage. All good. It appears that the amperes within an ac circuit are measured simply on the firm belief that voltage input is fixed - which is 110 V or whatever it is expected to be in that region.
So, let's say that I produce an AC current by pedaling a turbine with my legs. Then, how exactly do we measure AC voltage and current? According to me AC power could be measured, but not AC voltage or current. They would simply cancel out, or no? It is easier to measure the intensity and direction of a continuous current by the deflection of a magnet needle like the Oersted experiment.
In the case of AC, we know that something similar is happening in the wire, because of the joule effect and other energy productions. But if we place a compass nearby, the needle doesn't move.
But if we make a coil of wire over a iron core, it works as an electromagnet, that attracts iron with a magnitude that depends on the current. And the attraction is not affected by the change of polarity because what is being attracted is not a permanent magnet, but just an iron object.
That device can be placed inside a clamp meter, where the magnetic field of the wire being measured induces an emf (and a current) on this electromagnet. An iron needle is deflected proportional to induced current, that is proportional to the magnetic field, that is proportional to the wire AC current.
The following is multiple choice question (with options) to answer.
What is used to measure electric current? | [
"chronometer",
"galvanometer",
"anemometer",
"atomizer"
] | B | |
SciQ | SciQ-2700 | pregnancy, children
Title: What leads to the different types of navels? Obviously, there are "innies" and "outies" in the human belly button world. Both are the result of a knot tied in the umbilical cord just after birth.
But why do some belly buttons become outies while others become innies? Is it related to how the doctor ties the knot, or is it related to how the knot heals? After childbirth, the umbilical cord is either tied (similar to a tourniquet - the cord itself is not tied into a knot) or clamped to cut off the blood supply. It is then cut distal to the clamp/tie, separating the child from the rest of the cord and the attached placenta. The remaining cells die and dessicate, and the stump eventually falls off, forming the umbilicus or belly button. The default result, barring any issues, is an "innie". However, an "outie" may form if the child was born with a tiny umbilical hernia, or there was a small unnoticed infection at the base of the umbilical cord. Either of these could lead to the formation granulation tissue, described colloquially as an "outie". People can also have combination navels, with the indentation of an "innie" but a small amount of protruding granulation tissue inside.
The following is multiple choice question (with options) to answer.
What connects the fetus to the placenta? | [
"fallopian tube",
"umbilical cord",
"microbial cord",
"eustachian tube"
] | B | The fetus is connected to the placenta through the umbilical cord. |
SciQ | SciQ-2701 | metabolism, nutrition, digestive-system
Title: Do I have to chew for digestion to kick in? Liquid nutrient-rich products (such as Soylent) are consumed without chewing. But if I have to chew to initiate digestion, are those nutrients really "processed"? If you had to chew to digest, then beverages like sugary sodas would never be digested or provide calories or nutrients, as you (generally) don't chew when you drink them. No, chewing is not required for digestion or nutrient absorption. Chewing is important when eating solid foods, as the chewing action breaks down and begins to solublize the food, and stimulates the production of saliva, which contains enzymes that begin to break down the food prior to digestion in the stomach and intestines.
The following is multiple choice question (with options) to answer.
When your body digests food, it breaks down the molecules of nutrients and releases what? | [
"calories",
"energy",
"waste materials",
"gas"
] | B | Carbohydrates, proteins, and lipids contain energy. When your body digests food, it breaks down the molecules of these nutrients. This releases the energy so your body can use it. |
SciQ | SciQ-2702 | sedimentology
Title: What is the earliest sedimentation we know of? Did large-scale sedimentation occur in any great amount during or soon after the Hadean/Archean period? Or did it only start later, because of the intense geological activity? The oldest known metasedimentary rocks are about 3.8 billion years old, formed in the Eoarchaean era.
'Metasedimentary' just means they have been metamorphosed, so they started out as sediments. They are found in the Isua Greenstone Belt of southwestern Greenland. You can read about their discovery in Moorbath (2009). Quoting from there:
Published zircon dates strongly suggest that the depositional age of at least part of the [Isua supracrustal belt] could be closer to 3.8 Gyr than to 3.7 Gyr.
According to the International Commission on Stratigraphy (Cohen et al. 2013), this puts them firmly in the Eoarchaean era.
References
Cohen, K, et al. (2013). The ICS International Chronostratigraphic Chart. Episodes Journal of International Geoscience 36 (3). Link to PDF.
Moorbath, S (2009). The discovery of the Earth's oldest rocks. Notes and Records 63 (4). DOI: 10.1098/rsnr.2009.0004
The following is multiple choice question (with options) to answer.
The first period of the paleozoic era was called what? | [
"carboniferous",
"cambrian",
"permian",
"ordovician"
] | B | The first period of the Paleozoic Era was the Cambrian. By the beginning of the Paleozoic, organisms evolved shells. Shells could hold their soft tissues together. Shells could protect them from predators and from drying out. Some organisms evolved external skeletons. These are called exoskeletons . Organisms with hard parts also make good fossils. Fossils from the Cambrian are much more abundant than fossils from the Precambrian. |
SciQ | SciQ-2703 | organic-chemistry, reaction-mechanism, wittig-reactions, stereoselectivity
References
Vedejs, E.; Marth, C.F. Mechanism of the Wittig reaction: the role of substituents at phosphorus. J. Am. Chem. Soc. 1988, 110 (12), 3948–3958. DOI: 10.1021/ja00220a037.
Vedejs, E.; Fleck, T. J. Kinetic (not equilibrium) factors are dominant in Wittig reactions of conjugated ylides. J. Am. Chem. Soc. 1989, 111 (15), 5861–5871. DOI: 10.1021/ja00197a055.
Aggarwal, V. K.; Fulton, J. R.; Sheldon, C. G.; de Vicente, J. Generation of Phosphoranes Derived from Phosphites. A New Class of Phosphorus Ylides Leading to High E Selectivity with Semi-stabilizing Groups in Wittig Olefinations. J. Am. Chem. Soc. 2003, 125 (20), 6034–6035. DOI: 10.1021/ja029573x.
Robiette, R.; Richardson, J.; Aggarwal, V. K.; Harvey, J. N. On the Origin of High E Selectivity in the Wittig Reaction of Stabilized Ylides: Importance of Dipole−Dipole Interactions. J. Am. Chem. Soc. 2005, 127 (39), 13468–13469. DOI: 10.1021/ja0539589.
Robiette, R.; Richardson, J.; Aggarwal, V. K.; Harvey, J. N. Reactivity and Selectivity in the Wittig Reaction: A Computational Study. J. Am. Chem. Soc. 2006, 128 (7), 2394–2409. DOI: 10.1021/ja056650q.
The following is multiple choice question (with options) to answer.
What is a molecule with two fatty acids and a modified phosphate group attached to a glycerol backbone? | [
"phospholipid",
"amino acid",
"polymer",
"carbohydrate"
] | A | Figure 3.19 A phospholipid is a molecule with two fatty acids and a modified phosphate group attached to a glycerol backbone. The phosphate may be modified by the addition of charged or polar chemical groups. Two chemical groups that may modify the phosphate, choline and serine, are shown here. Both choline and serine attach to the phosphate group at the position labeled R via the hydroxyl group indicated in green. |
SciQ | SciQ-2704 | cardiology, embryology, pain, central-nervous-system
Title: At what stage is the nervous system developed enough to interpret neuronal signals as 'pain'? According to this article in Live Science, one of the reasons the fetus can't feel pain until 19 weeks is because the nervous system isn't fully developed.
But according to this article, the heart starts beating at day 16.
And according to this article, the nervous system controls the rate beating of the heart.
Then my question is, **how can it be assured that the nervous system isn't developed until 19 weeks, when the nervous system controls the heart beating rate since day 16? First, there is some confusion on your part about heart cells and pain perception. Heart cells generate an action potential intrinsically; they do not need the central nervous system to beat (your second article explains this; read the part about the importance of calcium.) So yes, long before a fetus can feel pain, the heart is beating, because there must be circulation of nutrients throughout the embryo.
Secondly, the vagus nerve and sympathetic nerves can affect heart rate (the former by slowing it down when firing). These nerves start to reach their endpoints late in week 4 of development. So 19 days is not correct.
Cardiac sympathetic system
Although the primitive human heart starts to beat at 21 to 22 d, heart development continues to day 50, and it is near the end of this period, during the fifth week, that thoracic neural crest cells migrate from the neural tube through the somites and form aggregations (ganglia) near the dorsal aorta. [emphasis mine]
To experience pain, however, requires maturation of certain parts of the brain, most importantly, part of the thalamus and the cerebral cortex:
Current theories of pain consider an intact cortical system to be both necessary and sufficient for pain experience. In support are functional imaging studies showing that activation within a network of cortical regions correlate with reported pain experience. Furthermore, cortical activation can generate the experience of pain even in the absence of actual noxious stimulation. These observations suggest thalamic projections into the cortical plate are the minimal necessary anatomy for pain experience. These projections are complete at 23 weeks' gestation. [emphasis mine]
The following is multiple choice question (with options) to answer.
Some women experience cramping and pain before and during what monthly cycle? | [
"deformation",
"menstruation",
"inflammation",
"reproduction"
] | B | Some women experience cramping and pain before and during menstruation. |
SciQ | SciQ-2705 | inorganic-chemistry, physical-chemistry, electrochemistry, electrons, electronic-configuration
one proton's positive charge attracts one electron.
The "neutral" in a neutral atom means electrically neutral.
How can a neutral atom attract electrons when it's supposed to have zero charge ? The answer lies in electronegativity. When a proton attracts an electron, the electron doesn't magically suck out the charge of the proton. The proton's charge is still distributed in all directions. The reason why 1 proton on average can attract only 1 electron is because electrons push each other out.
Now let's first take H - it has 1 proton which attracts 1 electron. If another electron jumps in, only 1 electron stays in the end. Then He - it has 2 protons, so it attracts electrons even more. So even though electrons are fighting for the place, the nucleus charge is enough to hold them.
It gets interesting with Li. It should have 3 electrons, right? But 1st shell can take only 2 electrons, so the 3d electron must go to the 2nd shell which is further away. In such case the inner shell of electrons has a much greater effect on the outer electron, this is called electron screening, not to mention that the further you are from nucleus - the weaker the attraction. So even though Li has more protons than He, it's too weak to hold electrons on the 2nd shell, so some other atom will take the electron away and Li will be ionized and become Li$^+$ with only 2 electrons.
How strongly an atom wants new electrons is called electronegativity. It increases to the right of the periodic table because nucleus gets larger and larger and can hold on more and more electrons. In the last columns atoms want electrons so much that they can mug other atoms with weaker electronegativity.
But then the row of the table finishes and new row starts. At this point previous shell is completely filled and a new shell starts, and the electron screening kicks in again.
You can see these trends here. Electronegativity is the reason why Na & Cl can't form a molecule (covalent bond) - Cl (strong electronegativity) simply takes Na's (weak electronegativity) electron and both become ions: Cl$^-$ and Na$^+$. In the end they form an ionic bond instead.
The following is multiple choice question (with options) to answer.
What is the attraction of oppositely charged ions caused by electron transfer called? | [
"covalent bond",
"velocity bond",
"ionic bond",
"solvent bond"
] | C | The attraction of oppositely charged ions caused by electron transfer is called an ionic bond. |
SciQ | SciQ-2706 | particle-physics, astrophysics, fusion
Title: How can fusion within the sun be possible if there is no such thing as helium-2 (2 protons, no neutrons) As stated in the question where does the sun(or other star) get the necessary neutron in order to produce the Helium atom? and how does this process occur (explain how the neutron incorporates). The sun gets its energy from the pp-chain. The first step is the two protons forming the diproton (Helium-2):
$$
\,^1_1H+\,^1_1H\to\,^2_2He+\gamma
$$
where the $\gamma$ is the photon (of energy about half an MeV). This quickly $\beta^+$-decays into a deuterium by converting a proton into a neutron:
$$
\,^2_2He\to\,^2_1D+e^++\nu_e
$$
where $e^+$ is the positron and $\nu_e$ the electron neutrino.
The following is multiple choice question (with options) to answer.
What process converts the sun's hydrogen nuclei into helium? | [
"nuclear fusion",
"combustion",
"nuclear fission",
"solar fission"
] | A | Figure 32.19 Nuclear fusion in the Sun converts hydrogen nuclei into helium; fusion occurs primarily at the boundary of the helium core, where temperature is highest and sufficient hydrogen remains. Energy released diffuses slowly to the surface, with the exception of neutrinos, which escape immediately. Energy production remains stable because of negative feedback effects. |
SciQ | SciQ-2707 | thermodynamics, phase-transition, metals, liquid-state
A correct microscopic picture of the melting transition
The different behavior of many observables characterizes crystalline solids and liquids. However, we should not forget that amorphous solids exist, blurring many possible characterizations of the transition based on the concept of spatial order or, on average static quantities. Dynamical properties remain a much clearer indication of the passage from a solid to a liquid phase. In particular, the apparently simple concept that liquid flow and solid don't is a good starting concept to build intuition on the melting process.
Here, I'll try to underline a few (correct) ideas one can connect to the fact that liquids flow.
The following is multiple choice question (with options) to answer.
Both solids and liquids hold a definite what? | [
"volume",
"mass",
"size",
"shape"
] | A | You encounter solids and liquids in many forms in your everyday life. Solids, unlike liquids, hold a definite shape. Both solids and liquids hold a definite volume. However, on a molecular level, these two states of matter are quite different. In this lesson we will introduce some of the properties of liquids and solids that affect your interactions with the substances all around you. |
SciQ | SciQ-2708 | electromagnetic-radiation, polarization
Title: How the polarization of electromagnetic wave is determined? What help us determine the polarization of electromagnetic wave . Does perpendicular electric and magnetic field determine it or does the direction of propagation ? The polarization of an electromagnetic wave follows the direction of the electric field. For example, if the electric component is oscillating along the x-axis and the magnetic field is oscillating in the y-axis, the polarization will be along the x-axis.
The following is multiple choice question (with options) to answer.
Because the fields that make up an electromagnetic wave are at right angles to each other and to the direction that the wave travels, an electromagnetic wave is considered what? | [
"stimulation wave",
"insverse wave",
"transverse wave",
"transverse wave"
] | C | As you can see in Figure above , the electric and magnetic fields that make up an electromagnetic wave occur are at right angles to each other. Both fields are also at right angles to the direction that the wave travels. Therefore, an electromagnetic wave is a transverse wave. |
SciQ | SciQ-2709 | quantum-mechanics, measurement-problem
If the usage of the language "exciting the outermost 2s electron to the 3s state" is correct, what physical measurement can I use to tell that this excitation has happened? Maybe somehow I could measure the energies of each of the electrons before and after the excitations and then I'd find that two energy values out of the 3 are the same before and after the laser pulse, but one energy I get has increased by the photon energy. But this method doesn't seem to help much, first because in an entangled system the individual particles are in mixed states and their energy measurement yield a statistical mixture of values (so at best all I could say is that the mean of one of the distributions has increased), and second, because I cannot label the electrons and associate the energy-value distributions to them (because they are indistinguishable) so again I can't say that there was an outermost electron in a certain state and now it is in another state. All I can say that the energy measurements on individual electrons previously yielded a distribution of values which was the sum of three probability distributions with certain means (e.g. $\overline{E}_1=\overline{E}_2<\overline{E}_3$) and deviations and now it's the sum of some other 3 distributions from which one maybe has a higher mean than before. [E.g. $\overline{E}'_1=\overline{E}'_2<\overline{E}'_3(>\overline{E}_3)$] But nothing says that the distribution with the higher mean comes from the electron which gave the highest mean before.
The following is multiple choice question (with options) to answer.
Which measure indicates the number of electrons in a given sublevel? | [
"superscripts",
"mole",
"subscripts",
"coefficients"
] | A | There are no forces of attraction or repulsion between gas particles . Attractive forces are responsible for particles of a real gas condensing together to form a liquid. It is assumed that the particles of an ideal gas have no such attractive forces. The motion of each particle is completely independent of the motion of all other particles. |
SciQ | SciQ-2710 | electric-fields
If $q>0$ the force $\textbf{F}$ is parallel to the electric field $\textbf{E}$.
If $q<0$ the force $\textbf{F}$ is anti-parallel to the electric field $\textbf{E}$.
Therefore, as Philip wrote, there is no logical contradiction involved: The force and the electric field don't have to point in the same direction.
An other example where this is the case is the magnetic force on a moving charge (the so called Lorentz force). Here the magnetic fields is perpendicular to the force.
The following is multiple choice question (with options) to answer.
Because force and electric field are what, they have direction as well as their value? | [
"sensors",
"neurons",
"mass",
"vectors"
] | D | Force and electric field are vectors and thus have direction as well as their value. |
SciQ | SciQ-2711 | 1 of 4 #1) What is the magnitude of vector A? Here vector a is shown to be 2.5 times a unit vector. So if you have a vector given by the coordinates (3, 4), its magnitude is 5, and its angle is 53 degrees. The magnitude of a vector is the length of the vector. Vectors in 2D Vectors Example: Express each of the following vectors as a column vector and find its magnitude. They are labeled with a "", for example:. #2) What is the direction of vector A relative to the negative y-axis? then the magnitude of velocity is 20Km/hr. speed is scalar as it has no direction. A Unit Vector has a magnitude of 1: The symbol is usually a lowercase letter with a "hat", such as: (Pronounced "a-hat") Scaling.
The following is multiple choice question (with options) to answer.
Acceleration is a vector, and thus has a both a magnitude and what else? | [
"wavelength",
"direction",
"pressure",
"temperature"
] | B | Acceleration is a vector, and thus has a both a magnitude and direction. Acceleration can be caused by either a change in the magnitude or the direction of the velocity. Instantaneous acceleration a is the acceleration at a specific instant in time. Deceleration is an acceleration with a direction opposite to that of the velocity. |
SciQ | SciQ-2712 | evolution, cell-biology
What do you mean by multicellularity?
The evolution of multicellularity can be discussed in the context where sister cells form an organism together or when unrelated cells (among the same species or even cells from different species) come together to form an organism. Also, the multicellularity can be discussed at a different level depending on how we want to define multicellularity. Is a stack of cells reproducing individually, working for their own benefit a multicellular? Do we need a division of labor? Do we need a division between germline (reproductive caste) and soma line (non-reproductive case)?
How many times did multicellularity evolve independently?
Some people consider that there are multicellular bacteria (biofilms) but we will avoid discussions that are based on limit-case definitions. Let's talk about eukaryotes. Most Eukaryotes are unicellular and multicellularity evolved many times independently in eukaryotes. To my knowledge, complex multicellularity however evolved only (only?) 6 times independently in eukaryotes.
The following is multiple choice question (with options) to answer.
What is it called when individual organisms work together with one another? | [
"competition",
"continuation",
"cooperation",
"dualism"
] | C | Bees and other social animals must cooperate to live together successfully. Cooperation means working together with others. Members of the group may cooperate by dividing up tasks, defending each other, and sharing food. The ants in Figure below are sharing food. One ant is transferring food directly from its mouth to the mouth of another colony member. |
SciQ | SciQ-2713 | europa
So, with the combined information from these sources, I would stand by a figure of somewhere between 15-28 km. The reason I don't go any higher is because I don't see an error bound or range of values in the paper's abstract - it just says "approximately 28 km thick" - and the full paper is unfortunately behind a paywall. As the paper's abstract says, there are local heating phenomena that could occur and cause the crust to vary in different places, which could explain why the figure isn't that precise. The reason I don't go any lower, on the other hand, is because that NASA FAQ didn't specify any exact values for their mention of "few kilometers thick", and didn't provide much explanation as to why those said scientists supported that idea.
The following is multiple choice question (with options) to answer.
How thick is the earth's continental crust, on average? | [
"15 kilometers",
"25 kilometers",
"35 kilometers",
"60 kilometers"
] | C | Continental crust is much thicker than oceanic crust. It is 35 kilometers (22 miles) thick on average, but it varies a lot. Continental crust is made up of many different rocks. All three major rock types — igneous, metamorphic, and sedimentary — are found in the crust. On average, continental crust is much less dense (2.7 g/cm3) than oceanic crust. Since it is less dense, it rises higher above the mantle than oceanic crust. |
SciQ | SciQ-2714 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
Which organ has a thick mucus lining that protects the underlying tissue from the action of the digestive juices? | [
"colon",
"stomach",
"spleen",
"liver"
] | B | functionality of pepsin. Second, the stomach has a thick mucus lining that protects the underlying tissue from the action of the digestive juices. When this mucus lining is ruptured, ulcers can form in the stomach. Ulcers are open wounds in or on an organ caused by bacteria (Helicobacter pylori) when the mucus lining is ruptured and fails to reform. Small Intestine Chyme moves from the stomach to the small intestine. The small intestine is the organ where the digestion of protein, fats, and carbohydrates is completed. The small intestine is a long tube-like organ with a highly folded surface containing fingerlike projections called the villi. The apical surface of each villus has many microscopic projections called microvilli. These structures, illustrated in Figure 34.12, are lined with epithelial cells on the luminal side and allow for the nutrients to be absorbed from the digested food and absorbed into the blood stream on the other side. The villi and microvilli, with their many folds, increase the surface area of the intestine and increase absorption efficiency of the nutrients. Absorbed nutrients in the blood are carried into the hepatic portal vein, which leads to the liver. There, the liver regulates the distribution of nutrients to the rest of the body and removes toxic substances, including drugs, alcohol, and some pathogens. |
SciQ | SciQ-2715 | agriculture
Title: What does "permanent field" mean in agriculture? I am reading a book that in a paragraph talks about the agricultural methods used in prehistoric Finland.
The further north and east, the more extensive the amount of
burn-beat cultivation, which was a far from primitive form of
agriculture. The yield was many times higher (twenty- to thirty-fold)
than on permanent fields (five- to ten-fold), and there were multiple
varieties of the technique
A history of Finland by Henrik Meinander.
One of them is burn-beating. Like I understand, in burn-beating people cut down the trees in the forests and burn the topsoil. This way they can use that soil for 3 to 6 years for cultivation.
The other method is permanent field. I have searched the internet and the result I got was "permanent crops", like here. In which case people planted trees once in a field and harvested them multiple times.
But in another research about prehistoric Finland it was saying:
The site of Orijärvi shows that permanent field cultivation, with
hulled barley as the main crop was conducted from approximately cal AD 600 onwards.
The following is multiple choice question (with options) to answer.
What historical event taught people that soil could be lost by plowing and growing crops and encouraged new methods to prevent erosion? | [
"the dust bowl",
"the flow bowl",
"the debris bowl",
"the land bowl"
] | A | The Dust Bowl taught people that soil could be lost by plowing and growing crops. This led to the development of new ways of farming that help protect the soil. Some of the methods are described in Figure below . |
SciQ | SciQ-2716 | the-moon, moon-phases
A 95-percent illuminated moon appears half as bright as a full moon
Believe it or not, the moon is half as bright as a full moon about 2.4
days before and after a full moon. Even though about 95 percent of
the moon is illuminated at this time, and to most casual observers it
might still look like a "full" moon, its brightness is roughly 0.7
magnitudes less than at full phase, making it appear one-half as
bright.
Perhaps the extra few degrees of fullness really does make a noticeable difference. I'd assumed it wouldn't make a big difference but this article suggests it does.
The following is multiple choice question (with options) to answer.
In what phase is the moon brightly illuminated? | [
"full moon",
"blue moon",
"crescent",
"new moon"
] | A | The Earth, Moon and Sun are linked together in space. Monthly or daily cycles continually remind us of these links. Every month, you can see the Moon change. This is due to where it is relative to the Sun and Earth. In one phase, the Moon is brightly illuminated - a full moon. In the opposite phase it is completely dark - a new moon. In between, it is partially lit up. When the Moon is in just the right position, it causes an eclipse. The daily tides are another reminder of the Moon and Sun. They are caused by the pull of the Moon and the Sun on the Earth. Tides were discussed in the Oceans chapter. |
SciQ | SciQ-2717 | newtonian-mechanics, rotational-dynamics, vectors, torque
In response to your comment:
The components of a vector aren't vectors because they don't have a direction. A vector lives in a vector space which has basis vectors, in Cartesian coordinates, for example, the basis vectors are $$\hat{\mathbf{x}}=\begin{pmatrix}1 \\ 0 \\ 0 \end{pmatrix}, \hat{\mathbf{y}}=\begin{pmatrix}0 \\ 1 \\ 0 \end{pmatrix}, \hat{\mathbf{z}}=\begin{pmatrix}0 \\ 0 \\ 1 \end{pmatrix}$$
A vector in this space is a linear combination of basis vectors, which means that any vector $\mathbf{v}$ can be written as $\mathbf{v} = a_x\hat{\mathbf{x}} + a_y \hat{\mathbf{y}} + a_z\hat{\mathbf{z}}$ where the $a$'s are what I'm calling the "components" of the vector. So the components aren't vectors, they are just numbers that you can multiply with vectors. However if you have a component together with its basis vector (as described in my main answer above), you do get a vector because (number $\times$ vector) is a vector.
The following is multiple choice question (with options) to answer.
What do vectors possess that scalars do not? | [
"height and polarity",
"direction and texture",
"magnitude and direction",
"magnitude and weight"
] | C | In physics, a quantity, such as mass, length, or speed that is completely specified by its magnitude and has no direction is called a scalar . A vector , on the other hand, is a quantity possessing both magnitude and direction. A vector quantity is typically represented by an arrow-tipped line segment. The length of the line, drawn to scale, represents the magnitude of the quantity. The direction of the arrow indicates the direction of the vector. Not only can vectors be represented graphically, but they can also be added graphically. |
SciQ | SciQ-2718 | biochemistry, food
Title: Who creates first nitrogen compounds in the food supply chain As I understand the food supply chain, organic compounds have to be created from a unlimited source (air, water...).
For instance, I figure that plants transform CO2 from air to organic carbon compounds, mainly carbohydrates, which are then the main source for most other life forms.
But I never heard about a plant turning atmospheric N2 to nitrogen compounds.
Where nitrogen compounds come from, and from which source ? There are nitrogen fixing bacteria who turn N2 into NH3. Some are free-living in soil, others live symbiotically with plants.
https://en.wikipedia.org/wiki/Nitrogen_fixation
The following is multiple choice question (with options) to answer.
What are the food making factories of plants? | [
"fruits",
"stems",
"leaves",
"roots"
] | C | |
SciQ | SciQ-2719 | evolution, speciation
Lastly, I consider whether primary and secondary sympatric speciation represent a mechanistic dichotomy, I suggest that primary and secondary contact can leave a similar genomic signature, when speciation is driven by tightly clustered or large effect loci. Arguably, the advent of affordable population genomic studies should place less focus on whether study systems result from primary or secondary contact and instead focus on the mechanistic aspects of the genomic architecture and making progress in identifying the conditions and processes under which natural and sexual selection can drive speciation, without extrinsic barriers to gene flow. TLDR
Sympatric speciation and allopatric speciation with later migration into the same habitat were historically diffucult to distinguish without looking at palaeo-biological data. The paper argues that while palaeo-genetics has made this easier, it is still difficult to distinguish pure sympatric speciation (which it calls primary) and sympatric speciation with a geneflow from an geographically separated (allopatrically speciated?) subpopulation (which it terms "secondary sympatric speciation" or "speciation with secondary gene flow", "...with secondary contact" etc.).
Speciation
Speciation is the divergence of one species (with one gene pool) into two different species (with different gene pools). It is obvious that this will happen if subpolulations are geographically separated and continue to adapt to their local conditions (allopatric speciation).
However, Mayr suggested (back in the 1940s) that there is another type of speciation that happens while the speciating populations share a habitat, and, consequently, while gene flow between these subpopulations is maintained until the speciation process is complete. This requires strong selection pressure towards two different ecological niches each with their associated adaptations.
Empirical examples have been discussed and called into question again. One cool and frequently discussed example is that of the apple maggot in North America that has developed from the hawthorn maggot after the introduction of apples in North America.
Debate
The following is multiple choice question (with options) to answer.
What does a pollinator pick from its body and carry directly to another plant of the same species? | [
"spore",
"pollen",
"egg",
"pathogen"
] | B | Wind-blown pollen might land anywhere and be wasted. Another adaptation solved this problem. Plants evolved traits that attract specific animal pollinators . Like the bee in Figure below , a pollinator picks up pollen on its body and carries it directly to another plant of the same species. This greatly increases the chance that fertilization will occur. |
SciQ | SciQ-2720 | 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.
Melting ice cubes and freezing water are examples of change of what? | [
"volume",
"role",
"role",
"state"
] | D | A: The paper is being cut into smaller pieces, which is changing its size and shape. The ice cubes are turning into a puddle of liquid water because they are melting. This is a change of state. The tablet is disappearing in the glass of water because it is dissolving into particles that are too small to see. The lighthouse is becoming coated with ice as ocean spray freezes on its surface. This is another change of state. |
SciQ | SciQ-2721 | botany, terminology, nomenclature
Regnum Animale: the animals;
Regnum Vegetabile: the plants;
Regnum Lapideum: the minerals (you read it right).
Note that, in this classification, "animals" correspond to what nowadays we call animals and protozoans, and "plants" correspond to what nowadays we call plants, algae, fungi and bacteria.
You have to keep in mind that this book was first published in 1735, well before the evolutionary biology being proposed in the XIX century and established in the XX century. Therefore, it is a book published when fixism was the current paradigm, full of mentions to the scala naturae.
So, the plants (as well as the animals) showed a continuum of species, going to the lower plants (the bacteria) to the higher plants (the flowering ones). It's worth mentioning again that, by that time, bacteria were plants: Phylum Schyzophyta, to be more precise.
Thus, we have "lower plants" and "higher plants", "lower animals" and "higher animals", as well as "lower minerals" and "higher minerals"!
Unfortunately, this terminology is so embedded in the biological sciences that even today, as I mentioned, we struggle to get rid of it.
Just drop "higher plants", whatever it means
As your Wikipedia link says, "higher plants" is a synonym of vascular plants. However, there are a lot of problems here:
First, this is a remnant of the scala naturae and, just because of that, should be avoided. Think of it as a meaningless term, just like "more evolved organism".
Second, there is no clear and indisputable definition of what is a "higher" plant. Some authors used to define the "higher plants" as the Angiosperms only, or the seed plants (Angiosperms + Gymnosperms), or the vascular plants (Angiosperms, Gymnosperms and Pteridophyta).
For instance, in lusophone biology books, it was very common a division in three groups:
lower plants: bacteria and algae;
intermediate plants: bryophytes and pteridophytes;
higher plants: gymnosperms and angiosperms.
The following is multiple choice question (with options) to answer.
What is the term for heterotrophs that eat only or mainly animals? | [
"parasites",
"carnivores",
"omnivores",
"predators"
] | B | All reptiles are heterotrophs, and the majority eats other animals. Heterotrophs that eat only or mainly animals are called carnivores. Large carnivorous reptiles such as crocodilians are the top predators in their ecosystems. They prey on large birds, fish, deer, turtles, and sometimes farm livestock. Their powerful jaws are strong enough to crush bones and turtle shells. Smaller carnivorous reptiles—including tuataras, snakes, and many lizards—are lower-level predators. They prey on small animals such as insects, frogs, birds, and mice. |
SciQ | SciQ-2722 | forces, classical-mechanics, energy
Title: What's the work done in an object to change its direction? Say, for example an object is moving 2m/s right and some force makes it travel 2m/s left. What would be the work done on this object? It starts and ends with the same kinetic energy, but clearly something had to be done to it to make it start moving left. Let's assume the force acting to the left is constant.
For it to change the velocity from 2 m/s to the right to 2 m/s to the left the force must first decelerate the object to 0 m/s. That means the force did negative work on the object because the direction of the force is opposite to the movement of the object while it slows down. Net negative work decreases the kinetic energy of the object.
But since the force remains, it now accelerates the object from 0 m/s to 2 m/s to the left. Now the force is doing positive work since its direction is the same as the motion of the object. Net positive work increases the kinetic energy of the object.
The amount of negative work done by the force to decelerate the object to 0 m/s equals the amount of positive work done by the force to accelerate the object to 2 m/s, for a net work of zero. Per the work energy theorem the net work done on an object equals its change in kinetic energy. Since the net work is zero, the change in kinetic energy is zero.
Hope this helps.
The following is multiple choice question (with options) to answer.
How much work is done when a force is applied in a different direction than the direction of movement? | [
"half",
"minimum",
"full",
"none"
] | D | Laura Guerin. Work is not done when a force is applied in a different direction than the direction of movement . CC BY-NC 3.0. |
SciQ | SciQ-2723 | thermodynamics, temperature, physical-chemistry, metrology
Title: How do you know mercury changes monotonically with temperature if mercury itself is used to make the thermometer? In the book I am reading recently "Concept of physics" volume 2 by professor H.C. Verma it says that (I am just summarizing the main points chronologically)
Energy is transferred from hot bodies to cold bodies when they are placed in contact.
The energy that transfer from one body to other without any mechanical work involved is called heat.
(then the book states zeroth law of thermodynamics)
All bodies in thermal equilibrium assigned equal temperature(I am assuming this definition of temperature).A hotter body is assigned higher temperature than a colder body.
Then the book says
Our next task is to define a scale temperature so that we can give numerical value to the temperature of a body. To do this we can choose a substance and look for its measurable quantity which monotonically changes with temperature.
The temperature can then be defined as a chosen function of this property.
The following is multiple choice question (with options) to answer.
The mercury or alcohol in a common glass what changes its volume as the temperature changes? | [
"barometer",
"thermometer",
"calculator",
"compass"
] | B | Conversion of Temperature Units We use the word temperature to refer to the hotness or coldness of a substance. One way we measure a change in temperature is to use the fact that most substances expand when their temperature increases and contract when their temperature decreases. The mercury or alcohol in a common glass thermometer changes its volume as the temperature changes. Because the volume of the liquid changes more than the volume of the glass, we can see the liquid expand when it gets warmer and contract when it gets cooler. To mark a scale on a thermometer, we need a set of reference values: Two of the most commonly used are the freezing and boiling temperatures of water at a specified atmospheric pressure. On the Celsius scale, 0 °C is defined as the freezing temperature of water and 100 °C as the boiling temperature of water. The space between the two temperatures is divided into 100 equal intervals, which we call degrees. On the Fahrenheit scale, the freezing point of water is defined as 32 °F and the boiling temperature as 212 °F. The space between these two points on a Fahrenheit thermometer is divided into 180 equal parts (degrees). Defining the Celsius and Fahrenheit temperature scales as described in the previous paragraph results in a slightly more complex relationship between temperature values on these two scales than for different units of measure for other properties. Most measurement units for a given property are directly proportional to one another (y = mx). Using familiar length units as one example: ⎞ ⎛ length in feet = ⎝ 1 ft ⎠ × length in inches 12 in. |
SciQ | SciQ-2724 | everyday-chemistry
Title: Can insect repellents kill insects? One day, there was a fly in my house. I really hate insects flying around me, but I don't want to catch it with my hands, so I sprayed some insect repellent directly onto the fly to try to get rid of it.
This is the insect repellent that I used.
Sticker reads:
"Wirkstoff basierend auf Zitronen-eucaluptusöl"
"Active ingredient based on lemon-eucalyptus oil"
When the insect repellent hits the fly, it slowed down and stopped flying, but it's still moving slowly on the window, so I applied the insect repellent again.
Eventually, the fly completely stopped moving, so I assume it's dead. Does the insect repellent actually killed the fly, or just stunned it? This Wikipedia article on "Insect repellent" pretty much answers your question.
An insect repellent isn't necessarily the same as an insecticide.
The repellent, well, "repels" insects; i.e- it discourages them from approaching you (or whatever you sprayed the repellent on) for as long as the chemical(s) linger. These (particularly those based on essential oils) aren't much of a health hazard to other animals.
An insecticide is actually designed to kill insects ("No sh!t Sherlock") rather than simply keeping them at bay. The term "insecticide" refers to substances that kill insects/arthropods at very low concentrations ( "very low" is subjective... I don't think there's an authoritative, precise definition for "insecticides" anyway).
FYI, any substance (including common stuff like air and water), supplied in excess (again, "excess" is also highly subjective) can kill. Ever heard of "Too much of anything can kill"?
The opposite effect is something called "Hormesis"; where just the right amount of anything (including radiation and toxins) can have a positive effect on you.
The following is multiple choice question (with options) to answer.
What are commonly used to control insect pests, but can have harmful effects on the environment? | [
"fertilizers",
"Herbicides",
"toxins",
"insecticides"
] | D | Insecticides are commonly used to control insect pests, but they can have harmful effects on the environment. |
SciQ | SciQ-2725 | inorganic-chemistry, alloy
Title: If alloys are homogeneous mixtures, why can't we separate their components? An alloy is a material composed of two or more metals or a metal and a nonmetal. And, they are usually formed by heating the elements to their melting points, and then cooling them, so that the components mix. Now, why doesn't this works backwards i.e. if we heat the alloy again to melting point of their constituents, and they should separate? Once the alloy has been formed the atoms from the different metals will have shared there electrons with each other and come to an equilibrium. In this state the metal atoms have formed a complex structure which has a different reactivity or properties than each individual metal did in its original form .
The following is multiple choice question (with options) to answer.
The components of what keep their own identity when they combine and can usually be easily separated? | [
"solution",
"mixture",
"alloy",
"compound"
] | B | The components of a mixture keep their own identity when they combine. Therefore, they usually can be easily separated again. Their different physical properties are used to separate them. For example, oil is less dense than water, so a mixture of oil and water can be separated by letting it stand until the oil floats to the top. Other ways of separating mixtures are shown in Figure below and in the videos below. |
SciQ | SciQ-2726 | wasps
Title: Can wasps see under moonlight? It appears that the best time to attack a wasp nest is in the middle of the night. Their venom might terrorize us (my five-day old sting remains swollen and is starting to have red bumps in an area the size of a tennis ball), but at least our eyesight is superior. If we attack while they are asleep, or at least resting, we have our best chance of escaping unscathed—or so the online pundits claim.
The nest in question is at the edge between the wall and the roof protrusion. Because it is 8 feet off the ground rather than on the ground, it would appear to be a paper wasp nest. But because it is covered with paper and the individual cells are occluded, with the entrance at the bottom the only visible path leading inside, it may well be a yellow jacket nest.
Maybe it's futile to attack the nest in September. One might as well let them be. The nest will anyway be deserted in October when the temperature starts to freeze overnight. But it's never too early to prepare for next Spring.
I could choose a night when there is absolutely no light—not even moonlight—but then I myself would need to use a flashlight, providing them with the means of pursuing me. Or I could choose a full-moon, or near full-moon, night, and then I can see and they can, perhaps, not see.
Can wasps see under moonlight? No.... probably not... wasp cannot see at night... their scotopic vision{dim light vision} is not well develop so before sunset they return back to thier nest... so at night.. probably you can get them all together... rather then hunting for each indivisually...for reference https://sciencing.com/how-to-identify-wasps-bees-13406632.html hope it helps..
The following is multiple choice question (with options) to answer.
What type of light can mosquitoes see? | [
"spicule",
"trichina",
"infared",
"neon"
] | C | A: Some animals can see light in the infrared or ultraviolet range of wavelengths. For example, mosquitoes can see infrared light, which is emitted by warm objects. By seeing infrared light, mosquitoes can tell where the warmest, blood-rich areas of the body are located. |
SciQ | SciQ-2727 | Moreover, if you want to know about the logic in general terms this article could be useful.
Logic, originally meaning "the word" or "what is spoken", but coming to mean "thought" or "reason", is a subject concerned with the most general laws of truth, and is now generally held to consist of the systematic study of the form of valid inference. A valid inference is one where there is a specific relation of logical support between the assumptions of the inference and its conclusion.
• Hmm, I'm not sure if this is very helpful here. Would you say that David's post makes yours 'superseded'? If not, why? Try to expand on that. – Discrete lizard Mar 25 '18 at 14:03
• @OmG : Can you recommend a list of materials to learn from ? – Sheldon Kripke Mar 31 '18 at 3:54
The following is multiple choice question (with options) to answer.
What subject is a way of learning about the natural world that is based on evidence and logic? | [
"evolution",
"geology",
"geography",
"science"
] | D | Science is a way of learning about the natural world that is based on evidence and logic. |
SciQ | SciQ-2728 | photosynthesis, chloroplasts
Title: Chloroplasts in an animal cell What would happen if we inject a chloroplast organelle into an animal cell?
Will the animal cell destroy it? Or is it possible that the chloroplast will somehow survive, and even replicate? Could there be photosynthesis in such a cell, or will some of the necessary mechanisms be missing? To answer your bigger question:
Yes, most of this is possible - under some conditions -, and animals and animal cells can acquire chloroplasts, and use them.
E.g.: see Elysia chlorotica whose cells actively take up chloroplasts and use them, and keep them alive (though not replicating). - Though some genes of algae are also contained in the Elysia chlorotica genome - which may be considered as partial replication.
Also there are salamanders that have replicating algae within them (since embryogenesis) - even algae (with chloroplasts) within animal cells - though here the algae might be rather understood as symbionts or "cell types", and the animal cells don't have the chloroplasts by themselves.
The following is multiple choice question (with options) to answer.
Chloroplasts are present only in cells of eukaryotes capable of what process? | [
"sexual reproduction",
"digestion",
"hydrolysis",
"photosynthesis"
] | D | |
SciQ | SciQ-2729 | nuclear-engineering, gamma-rays, medical-physics
Title: X-ray shielding X-ray shielding, why is lead used to shield us when taking X-ray images?
As far as I remember (but can't find it on wikipedia ... ), the deflection on (high energy) photons increases the more heavier the nuclei are. (Don't remember and don't find if it's really the mass or rather the proton number.)
In either case, there are heavier, more dense materials with higher proton numbers.
The material is not consumed nor altered by exposure to X-rays. So why don't we use gold or depleted uranium (just to name some alternatives)?
(Not sure about tags, if anyone knows better, please feel free to suggest/add some others.)
Edit: as the answers and comments here helped me to clear my mind to change the question, but the new question is sufficiently different, I've asked a follow-up here: Formula for scattering and energy change of photons on (naked) nuclei I pulled out my notes from a shielding class and found that the absorption cross section per atom follows a rule: $$\sigma_a\sim\frac{Z^p}{E^3},$$
where $z$ is the atomic number of the absorber atom, $E$ is the energy of the photon, and $p$ is an energy dependent value between 3 and 5. For most x-rays, $p\simeq 4$.
While the cross-section per atom does indeed get larger for increasing $Z$, the density of the material is important, too. The density peaks at osmium ($Z=76$), then drops off, then climbs again in the actinides, but never reaches densities near osmium and iridium ($Z=77$).
When considering the effectiveness of an shield/absorber, one must consider the combined effects of cross-section per atom and density. The result of this is a quantity known as the linear attenuation coefficient, $\mu$, which is typically quoted in $\mathrm{cm}^{-1}$. This is used to calculated the intensity of radiation after travelling through a thickness, $x$ of a material: $$I(x)=I_0 e^{-\mu x}.$$
The following is multiple choice question (with options) to answer.
Shielding should be used when receiving x-rays to limit exposure to what potentially harmful form of energy? | [
"radiation",
"evaporation",
"pollution",
"convection"
] | A | To physically limit radiation doses, we use shielding, increase the distance from a source, and limit the time of exposure. Figure 32.10 illustrates how these are used to protect both the patient and the dental technician when an x-ray is taken. Shielding absorbs radiation and can be provided by any material, including sufficient air. The greater the distance from the source, the more the radiation spreads out. The less time a person is exposed to a given source, the smaller is the dose received by the person. Doses from most medical diagnostics have decreased in recent years due to faster films that require less exposure time. |
SciQ | SciQ-2730 | ornithology
Title: How do birds learn their tunes in isolation from their own species? I wonder what a bird would sing if it didn't have its parents around (or any other birds for that matter) to learn its chirping sounds from.
I'm interested in how a bird would sing...
in complete isolation from creatures communicating through sound;
in isolation from its own species, but with other birds;
in isolation from all birds (other animals and creatures are there for it)
For example,
Would a bird even feel the need to speak up if there wasn't any other vocalizing creature around?
Would a bird learn other species' signals? Would it only learn from one species, the one which it would think of a fitting mate?
Would a bird try to mimic a non-flying creature's signals?
These are similar questions, but if you think they should be separated, let me know in the comments. Birds have to learn their song patterns.
They are able to chirp, but the songs with "meaning" are learned from their parents or whatever they learned to be their "parent".
Here is a paper that related bird song learning to human learning (of speech, for example).
Birds brought up by parents from another species learned to sing their songs.
There are many birds that learn to imitate other animals or sounds, so in isolation from all birds they will probably do this.
I can't recall where, but I read a paper once, where little finches brought up by humans developed a song resembling the "Hello there, now there's food", their caretaker always greeted them with. (Not the speech, but the overall sound pattern.) They might not understand the signals, but they try to communicate nevertheless. Some birds use sound from other species to mock others, scare them off or lure them into thinking they might be more powerful than they are.
Birds brought up in total isolation do sing, but not the typical songs you know from their species. Deaf birds who can't hear themselves, though, do not (always) sing.
The following is multiple choice question (with options) to answer.
What is the way animals act either alone or with other animals called? | [
"animal point",
"animal behavior",
"animal way",
"animal lifestyle"
] | B | Barking, purring, and playing are just some of the ways in which dogs and cats behave. These are examples of animal behaviors. Animal behavior is any way that animals act, either alone or with other animals. |
SciQ | SciQ-2731 | eyes, vision, light, uv
Title: Are there specific conditions that allow humans to see ultraviolet wavelengths It is fairly common knowledge that the lens in its normal state absorbs ultraviolet (UV) radiation. An interesting notion has come up from time to time in my reading that suggests there are a small number of conditions that result in humans being able to 'see' ultraviolet.
What conditions may cause this? Also, those affected, would they 'see' it has a different shade of violet? You will be interested in Aphakia, which is the lack of an eye lens usually through surgery but sometimes from birth. These individuals supposedly see UV as a whitish-blue or whitish-violet:
This appears to be because the three types of colour receptor (red, green and blue) have similar sensitivity to ultraviolet, so it comes out as a mixture of all three - basically white, but slightly blue because the blue sensors are somewhat better at picking up UV.1
The following is multiple choice question (with options) to answer.
What three primary colors of light can be distinguished by the human eye? | [
"blue, red, orange",
"red, green, yellow",
"red, green, blue",
"yellow, green, blue"
] | C | The human eye can distinguish only red, green, and blue light. These three colors are the primary colors of light. All other colors of light can be created by combining the primary colors. Secondary colors of light—cyan, yellow, and magenta—form when two primary colors combine equally. |
SciQ | SciQ-2732 | endocrinology
Excitement or stress response, including fast heart rate and breathing and anxiety: short term response: adrenaline; long-term response: cortisol
Appetite: ghrelin, leptin, adiponectin, cholecystokinin, insulin, glucagon-like peptide, gastrointestinal peptide...
Sexual drive: sex hormones, mainly testosterone and estradiol
Sleepiness: melatonin, cortisol
Depression: cortisol, sex hormones (mainly in women)
The point of this answer is to show that some of your feelings can be simply affected by hormones, which are note some ultimate forces, and that being aware of that can help you to control them to some extent.
The following is multiple choice question (with options) to answer.
Which body system releases hormones that act on target cells to regulate development, growth, energy metabolism, reproduction, and many behaviors? | [
"endocrine system",
"exocrine system",
"lymphatic",
"pituitary"
] | A | 37.5 | Endocrine Glands By the end of this section, you will be able to: • Describe the role of different glands in the endocrine system • Explain how the different glands work together to maintain homeostasis Both the endocrine and nervous systems use chemical signals to communicate and regulate the body's physiology. The endocrine system releases hormones that act on target cells to regulate development, growth, energy metabolism, reproduction, and many behaviors. The nervous system releases neurotransmitters or neurohormones that regulate neurons, muscle cells, and endocrine cells. Because the neurons can regulate the release of hormones, the nervous and endocrine systems work in a coordinated manner to regulate the body's physiology. |
SciQ | SciQ-2733 | proteins, translation, mrna, ribosome
Title: What is the advantage of the way eukaryotes initiate translation? The eukaryote and prokaryote mechanism for translation is slightly different. Is there any advantage of the eukaryote translation mechanism ?
Edit : I specifically want to know why eukaryotic ribosome first attaches to tRNA and then to mRNA but prokaryotic ribosome can do this in either order. Is there any advantage of the former ? As far as I understand it (and I'll preface this by saying that initiation is not my strongest point), but prokaryotes utilize the beautiful AGGAGG Shine-Dalgarno sequence. Usually around 8bp upstream of the start codon, it is this sequence that the prokaryotic ribosome seeks out to initiate translation. It does this through a complementary region in the 3' sequence of the ribosomal RNA. Upon complementary binding, the ribosome and mRNA are correctly bound. Convenient!
In eukaryotes, however, there is no consensus SD sequence, so a different mechanism must be used; the complex of 40S and Methionine tRNA serves this purpose. The two together scan the mRNA, looking for an AUG start codon which the tRNA is complementary to. This eventually brings the full ribosome (40S + 60S) together to start translation.
The following is multiple choice question (with options) to answer.
What is the main difference between eukaryotic and prokaryotic cells? | [
"prokaryotic cells have a nucleus",
"eukaryotic cells have a nucleus",
"eukaryotic cells have a flagella",
"eukaryotic cells have a cell wall"
] | B | There are two basic types of cells, prokaryotic cells and eukaryotic cells . The main difference between eukaryotic and prokaryotic cells is that eukaryotic cells have a nucleus . The nucleus is where cells store their DNA , which is the genetic material. The nucleus is surrounded by a membrane. Prokaryotic cells do not have a nucleus. Instead, their DNA floats around inside the cell. Organisms with prokaryotic cells are called prokaryotes . All prokaryotes are single-celled (unicellular) organisms. Bacteria and Archaea are the only prokaryotes. Organisms with eukaryotic cells are called eukaryotes . Animals, plants, fungi, and protists are eukaryotes. All multicellular organisms are eukaryotes. Eukaryotes may also be single-celled. |
SciQ | SciQ-2734 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
What forms when cells start to grow out of control? | [
"fat",
"tumor",
"inflammation",
"moles"
] | B | Cancer of the testes is most common in males aged 15 to 35. It occurs when cells in the testes grow out of control and form a tumor. If found early, cancer of the testes usually can be cured with surgery. |
SciQ | SciQ-2735 | 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.
Organs, vessels, and lymph make up what system? | [
"circulatory",
"digestive",
"nervous",
"lymphatic"
] | D | The lymphatic system consists of organs, vessels, and lymph. |
SciQ | SciQ-2736 | biochemistry
This explanation provides a somewhat agreement of Le Chatlier’s principle. (i.e. where a dynamic equilibrium is affected by changing conditions, the position of equilibrium moves to counteract the change)
Consider this simple hypothesis:
J = vf – vr
Since a metabolic pathway is a series of enzyme-catalysed reactions,
it is easiest to describe the flux of metabolites through the pathway
by considering its reaction steps individually. The flux of
metabolites, J, through each reaction step is the rate of the forward
reaction, vf, less that of the reverse reaction, vr:
At equilibrium, by definition, there is no flux (J=0), although vf and
vr may be quite large. At the other extreme, in reactions that are far
from equilibrium, vf>> vr, so that the flux is essentially equal to
the rate of the forward reaction, J~vf.
The flux throughout a steady-state pathway is constant and is set (generated) by the pathway’s rate determining step (or steps).
Consequently, control of flux through a metabolic pathway requires:
that the flux through this flux-generating step vary in response to the organism’s metabolic requirements and
that this change in flux be communicated throughout the pathway to maintain a steady state
The following is multiple choice question (with options) to answer.
Like the marketplace, the metabolic economy is regulated by what basic principle? | [
"industrial and demand",
"price and demand",
"supply and demand",
"jobs and demand"
] | C | |
SciQ | SciQ-2737 | botany, methods
I think it really depends on the type of plant whether its stems will root or not and how long the stem will retain its rooting potential after being cut.
If possible, you can try the following. Put the cut stem in a small plastic pot (they are very cheap) with soil and see if it roots (leaves will begin growing). If it does, transfer it into a larger pot later once it has grown. Wait for it to grow big enough to spread its roots thoughout the pot, then shift it into a big pot.
I believe if a plant roots, then all stems of that plant will root. Plus, congratulations on your first plant.
The following is multiple choice question (with options) to answer.
As roots grow longer they will always do what? | [
"get larger",
"grow downward",
"change direction",
"get thicker"
] | B | Roots have primary and secondary meristems for growth in length and width. As roots grow longer, they always grow down into the ground. Even if you turn a plant upside down, its roots will try to grow downward. How do roots “know” which way to grow? How can they tell down from up? Specialized cells in root caps are able to detect gravity. The cells direct meristem in the tips of roots to grow downward toward the center of Earth. This is generally adaptive for land plants. Can you explain why?. |
SciQ | SciQ-2738 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
Which virus causes cold sores? | [
"microbes virus",
"herpes virus",
"flu virus",
"stilts virus"
] | B | Cold sores are caused by a herpes virus. |
SciQ | SciQ-2739 | chromosome, gene
Title: Interpretation of picture of human chromosomes
Does this picture show sister chromatids or homologous chromosomes? If they are homologous then what is YY? If they are sister chromatids then do homologous chromosomes ever appear like this (with the centromere)? Do sister chromatids exist only in prophase-I to anaphase-I of meiosis? Since I have used more than 1 image in my answer; with numbers starting from 1; I'll call your provided figure as figure-0
What is shown in following picture?
Though the image showing many things; in overall it is an image of a set of chromosomes; seemingly almost certainly from human. The chromosomes has been stained with a banding method (though I'm not sure about which banding method used).
Are they sister chromatids?
Could not be answered in few words. The image contains sister chromatids. But the entire image in OP (fig-0) could not be described as "image of sister chromatids".
All the chromosomes in this image are in metaphase. so each chromosome is made up of 1-pair of chromatids which are sister-chromatids to each-other.
Fig 1. This total image showing 1 chromosome (on or before metaphase) showing 2 chromatids (written as A and B). A and B are sister chromatids because their DNA-content resulted from same mother-DNA molecule when replication happened at S-phase of cell-cycle; so their DNA content is basically same.
or homologous chromosome?
No. They are Not homologous. However Chromosome X and Y do have some homologous portion (Pseudo-autosomal regions). Question-figure (Fig-0) neither shows a complete set (46 chromosomes) from 1 diploid cell; nor shows its half (the haploid set) (that is causing your confusion about X and Y; let me proceed...) . Fig-0 shows each-type of human chromosome in 1 piece.
If they are homologous then what is YY?
YY karyotype does not normally exist in human.
Karyotype of human male:
2 x (22 autosome) + 1 X-chromosome + 1 Y-chromosome.
The following is multiple choice question (with options) to answer.
Duplicated chromosomes are composed of two sister what? | [
"eukaryotes",
"karyotypes",
"nucleotides",
"chromatids"
] | D | Duplicated chromosomes are composed of two sister chromatids. Chromosomes are compacted using a variety of mechanisms during certain stages of the cell cycle. Several classes of protein are involved in the organization and packing of the chromosomal DNA into a highly condensed structure. The condensing complex compacts chromosomes, and the resulting condensed structure is necessary for chromosomal segregation during mitosis. |
SciQ | SciQ-2740 | special-relativity, energy, mass, energy-conservation, mass-energy
Title: Where does all the mass created from energy go? So mass can be created from energy when small protons speed up, 430 times bigger to be exact. I don't know if this is a stupid question, but I'm in middle school so cut me some slack. Where does all that mass go? Is it converted to thermal energy? Say we covered the earth with solar panels, that would produce a lot of energy, also producing a lot of mass. I don't know if that's the right wording, I don't want to sound like I don't know energy can't be created or destroyed but if anyone could answer these questions for me that'd be great. The notion of "mass" is probably less deeply meaningful as you might think. Science has come a long way since the days when mass was thought to have such deep significance. Nowadays, energy is the primary concept, because there is a law of conservation of energy, and energy is linearly additive: that means that the sum of energies for two separate systems equals the total energy for the system as a whole. These two properties - conservation and linear additivity make energy a useful notion in physics.
Mass has neither of these properties. It is not conserved, and it is not additive. The rest mass of a system two photons moving in opposite directions is nonzero, whereas the rest mass of each is nought.
In particular, since mass is not conserved, it doesn't have to "go anywhere", unlike energy. It can simply disappear or appear, as in the photon example. So nowadays mass is less useful as a concept in physics.
The following is multiple choice question (with options) to answer.
What is the name of anything that has mass and takes up space? | [
"depth",
"matter",
"carbon",
"solid"
] | B | |
SciQ | SciQ-2741 | geophysics, earth-rotation, earth-system, solar-terrestrial-physics, time
For any given day, the calculation of the distance to the Sun is complicated, but websites like this one, provide a real time value you can use in the above formula [that site also provides the speed right away!].
These values are basically the same from one year to another. However, they do slowly change as the eccentricity of Earth's orbit gradually varies over a ~400,000 years cycle as described by the Milankovitch cycles.
Now, for Earth's speed of rotation about its own axis the value is pretty much the same each day; variations are of day length are on the order of a fraction of a millisecond. Part of that variation is periodic and more or less predictable and another part is from other less predictable factors. But for all practical purposes the length of the day is constant through the year. The following figure shows those tiny variations in day length since the early 1960's:
The following is multiple choice question (with options) to answer.
The units of time, day and year are based on what? | [
"gravitational waves",
"motions of earth",
"moon phases",
"motions of the sun"
] | B | |
SciQ | SciQ-2742 | forces, pressure, continuum-mechanics, stress-strain
Title: Why is a force distributed over an area? Why couldn't the stress be directly equal to the force? So, my question might seem silly. I know in real life when we apply a force with our hand and push on lets say a cylinder , we know the force will be distributed over the cross section of the area, so if we had a wider area, we need more force, and if we had smaller area, then we need less force to push the cylinder a certain distance.
So its intuitive. The stress will be the force divided by the given area.
But why? like what happens at the micro-scale, and what makes the force be divided?
Thanks. Actually as @trula said the external force you apply acts only at the contact point but since all atoms are connected to each other via "interatomic forces" , your external force gets distributed all along the surface and so we need to define force per unit area viz. Stress.
The spring model of atomic structure is quite self explanatory about the interatomic force distribution.
The following is multiple choice question (with options) to answer.
What is the term for an amount of force pushing against a given area? | [
"resistance",
"mass",
"force",
"pressure"
] | D | Gas particles are constantly moving and bumping into things, and this creates force. The amount of force pushing against a given area is called pressure. |
SciQ | SciQ-2743 | physical-chemistry, quantum-chemistry
Title: Most probable point for finding an electron in the 1s orbital of a Hydrogen atom My professor says that the most probable point for finding an electron
in a 1s orbital of a hydrogen atom is at its origin.
He explains this by citing the fact that the square of the wave function which gives the probability density is maximum at the origin.
At the same time, we all agree that the Bohr radius is the distance at which probability of finding the electron is maximum for 1s orbital.
I can understand the reasoning he gave about the origin being the highest probable point for finding an electron, but then why are the graphs of the radial distribution function so? I provide here a few supplementary comments; the major part of your question has been answered by DSVA.
The following is multiple choice question (with options) to answer.
What is the region called where an electron is most likely to be found? | [
"the shell",
"the ellipse",
"the nucleus",
"the orbital"
] | D | Negative electrons are attracted to the positive nucleus. This force of attraction keeps electrons constantly moving around the nucleus. The region where an electron is most likely to be found is called an orbital. |
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