source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-4544 | physical-chemistry, molecules, conductivity
Title: What attributes cause a substance to be nonconductive or conductive I understand what causes elements to be conductive or nonconductive. But what causes a substance say rubber to be nonconductive at a molecular level? Conductivity requires mobile electrons. Metals tend to have loosely held valence electrons so metals are generally conductive. Metals have loosely held valence electrons for two reasons: metals tend not to be very electronegative (able to stabilize electron density) and metals tend to be somewhat big atoms by nature of many metals having a d-group of electrons. D electrons are further from the nucleus on a time average basis than s electrons or p electrons.
However, conductors do not have to be metals. Consider graphite. Graphite is $\ce{sp^2}$ hybridized. Graphite is made solely of carbon atoms - and carbon isn't a metal! The mobile pi electrons in graphite due to resonance allows graphite to be a good conductor.
I should also note that conductivity does not always imply mobile electrons; solutions can be conductive too and this is due to mobile electrolytes (ions). For example, you will find that deionized water is completely unconductive. However, regular tap water is generally conductive due to the presence of ions (e.g. chloride ions from chlorination). Gatorade is also very conductive because it is especially formulated to contain a lot of electrolytes.
The following is multiple choice question (with options) to answer.
What is responsible for many properties of covalent compounds, which have relatively low boiling points, cannot conduct electricity, and may not dissolve in water? | [
"atomic weight",
"covalent bonds",
"ionic charge",
"accretion bonds"
] | B | Covalent bonds are responsible for many of the properties of covalent compounds. Covalent compounds have relatively low boiling points, cannot conduct electricity, and may not dissolve in water. |
SciQ | SciQ-4545 | human-biology, biophysics, skin, light, uv
Title: Can UV radiation be safe for the skin? It is well known that UV radiation can damage the DNA and generally harm our skin.
We also know that UV radiation helps on the production of melanin and Vitamin D.
From what I could find, the DNA absorption spectrum goes to almost zero for wavelengths higher than 300 nm. This seems to suggest that we would be safe to use UV radiation between 300 and 340 nm in our skin (as long as the power or exposure is not too high/long to make burns), for therapeutic purposes such as the stimulation of Vitamin D production.
Is this assumption correct? Are there any evidences that we could use this UV wavelength range safely? You're talking about long-wave UV, or UV-A radiation. In the 80s, experts claimed that this was a safe wavelength. Protection against UV-A was not part of sunscreen in the early days. Consequently, UV-A was (and still is) used in tanning beds due to its perceived safety over UV-B. However, a lot of research has been done since.
UV-A is well understood now to also be unsafe in unreasonable amounts. Currently, UV-A protection is a typical feature of sunscreen and tanning beds are still not a healthy alternative to moderate, healthy doses of sun. Here is a recent review covering some of the aspects comparing different UV range effects on skin. I really suggest you put a search engine to good use here; it makes little sense for us to expound on the literature when it is so clear and easily available.
In summary,
UVA certainly contributes to the development of skin cancer.
UVA penetrates deeper into the skin than UV-B (which is largely responsible for 'burning' of the topmost layer of skin, without directly affecting the deeper layers). For this reason, UV-B is associated primarily with burning and UV-A is primarily associated with aging and aging diseases like cancer.
It is important to note that 95% of UV light in every day life is UV-A, because it does not vary seasonally and can penetrate clouds and windows. Therefore, in spite of the fact that short wavelengths carry more energy per photon, the ratios of UV-A and UV-B exposure are far from equal.
These are only a few of the explanations as to why we observe an incidence of aging and skin damage and disease upon UV-A exposure.
The following is multiple choice question (with options) to answer.
Tanning salons claim to use a “safe” form of what light, with a longer wavelength than that in sunlight? | [
"microwave",
"X rays",
"uv (ultraviolet)",
"infrared"
] | C | 29.3 Photon Energies and the Electromagnetic Spectrum 11. Why are UV, x rays, and γ rays called ionizing radiation? 12. How can treating food with ionizing radiation help keep it from spoiling? UV is not very penetrating. What else could be used? 13. Some television tubes are CRTs. They use an approximately 30-kV accelerating potential to send electrons to the screen, where the electrons stimulate phosphors to emit the light that forms the pictures we watch. Would you expect x rays also to be created? 14. Tanning salons use “safe” UV with a longer wavelength than some of the UV in sunlight. This “safe” UV has enough photon energy to trigger the tanning mechanism. Is it likely to be able to cause cell damage and induce cancer with prolonged exposure? 15. Your pupils dilate when visible light intensity is reduced. Does wearing sunglasses that lack UV blockers increase or decrease the UV hazard to your eyes? Explain. One could feel heat transfer in the form of infrared radiation from a large nuclear bomb detonated in the atmosphere 75 km from you. However, none of the profusely emitted x rays or γ rays reaches you. Explain. Can a single microwave photon cause cell damage? Explain. In an x-ray tube, the maximum photon energy is given by. |
SciQ | SciQ-4546 | virology, pathology, breathing
Fabian, P., McDevitt, J. J., DeHaan, W. H., Fung, R. O., Cowling, B. J., Chan, K. H., ... & Milton, D. K. (2008). Influenza virus in human exhaled breath: an observational study. PloS one, 3(7), e2691.
Granados, A., Peci, A., McGeer, A., & Gubbay, J. B. (2017). Influenza and rhinovirus viral load and disease severity in upper respiratory tract infections. Journal of Clinical Virology, 86, 14-19.
Milton, D. K., Fabian, M. P., Cowling, B. J., Grantham, M. L., & McDevitt, J. J. (2013). Influenza virus aerosols in human exhaled breath: particle size, culturability, and effect of surgical masks. PLoS pathogens, 9(3), e1003205.
The following is multiple choice question (with options) to answer.
Respiratory therapists or respiratory practitioners evaluate and treat patients diseases affecting what part of the body? | [
"heart, lungs, stomach",
"brain, stomach, heart",
"byproduct , heart , and blood vessels",
"lung, heart, and blood vessels"
] | D | Respiratory Therapist Respiratory therapists or respiratory practitioners evaluate and treat patients with lung and cardiovascular diseases. They work as part of a medical team to develop treatment plans for patients. Respiratory therapists may treat premature babies with underdeveloped lungs, patients with chronic conditions such as asthma, or older patients suffering from lung disease such as emphysema and chronic obstructive pulmonary disease (COPD). They may operate advanced equipment such as compressed gas delivery systems, ventilators, blood gas analyzers, and resuscitators. Specialized programs to become a respiratory therapist generally lead to a bachelor’s degree with a respiratory therapist specialty. Because of a growing aging population, career opportunities as a respiratory therapist are expected to remain strong. |
SciQ | SciQ-4547 | plant-anatomy
Title: Are bryophyte sporangia multicellular? My research on the matter can be summarized in a sentence: "It [sporangium] can be composed of a single cell or can be multicellular" (Source: https://en.wikipedia.org/wiki/Sporangium). Yet there shouldn't be a reply placed between "They are" and "They aren't" test options, speaking of "Are bryophyte sporangia multicellular?". A link to the source where I could ascertain whether the bryophyte sporangia is multicellular (if I could ascertain) is highly appreciated. In Embryophyta (land plants), including bryophytes, the sporangium is usually a multicellular structure.
Perhaps you meant to ask about the number of spore mother cells (SMCs) in each sporangium? That varies across groups. In bryophytes, each sporangium has many SMCs, and accordingly produces a large number of spores. (Contrast this with angiosperms, where a megasporangium [called an ovule] has only one megaspore mother cell.)
References and further reading:
https://courses.lumenlearning.com/boundless-biology/chapter/bryophytes/
https://www.britannica.com/science/plant-development
Image attribution:
By LadyofHats. (Public domain;
https://commons.wikimedia.org/wiki/File:Hornwort_structures.jpg)
The following is multiple choice question (with options) to answer.
Within each sporangium, hundreds of what kind of spores develop and are dispersed through the air? | [
"haploid",
"polyploid",
"infertile",
"diploid"
] | A | |
SciQ | SciQ-4548 | photosynthesis
Title: Photosystem I and the ETC In the light reactions of photosynthesis, Photosystem I receives electrons from the ETC after Photosystem II sends them to the ETC. Then, when Photosystem I receives light, the electron becomes excited and passes the electron back to the ETC. This leads me to my question: In the following question, are both $B$ and $E$ correct?
Which of the following are directly associated with photosystem I?
$A)$ harvesting of light energy by ATP
$B)$ receiving electrons from the thylakoid membrane electron transport chain
$C)$ generation of molecular oxygen
$D)$ extraction of hydrogen electrons from the splitting of water
$E)$ passing electrons to the thylakoid membrane electron transport chain It appears the author of the question is trying to use "thylakoid electron transport chain" in an overly specific way. The chain from which PS I receives electrons has far more components and is different from the shorter chain to which PS I passes its electrons. But according to my copy of Biology, Campbell & Reece 7th edition, both are called "electron transport chains" and both reside in, or on, the thylakoid membrane. Perhaps the "directly" in the question refers to the fact that PS I's electron is first captured by a "primary receptor" before being passed to ferredixon, the first member of the chain to which PS I passes electrons. But, again according to Campbell, this primary acceptor is considered part of the photosystem.
I used to teach this stuff. I'd toss out the question.
The following is multiple choice question (with options) to answer.
What delivers power to the chemical factory chloroplasts? | [
"chlorophyll",
"water",
"oxygen",
"the sun"
] | D | |
SciQ | SciQ-4549 | plant-anatomy
Title: Are bryophyte sporangia multicellular? My research on the matter can be summarized in a sentence: "It [sporangium] can be composed of a single cell or can be multicellular" (Source: https://en.wikipedia.org/wiki/Sporangium). Yet there shouldn't be a reply placed between "They are" and "They aren't" test options, speaking of "Are bryophyte sporangia multicellular?". A link to the source where I could ascertain whether the bryophyte sporangia is multicellular (if I could ascertain) is highly appreciated. In Embryophyta (land plants), including bryophytes, the sporangium is usually a multicellular structure.
Perhaps you meant to ask about the number of spore mother cells (SMCs) in each sporangium? That varies across groups. In bryophytes, each sporangium has many SMCs, and accordingly produces a large number of spores. (Contrast this with angiosperms, where a megasporangium [called an ovule] has only one megaspore mother cell.)
References and further reading:
https://courses.lumenlearning.com/boundless-biology/chapter/bryophytes/
https://www.britannica.com/science/plant-development
Image attribution:
By LadyofHats. (Public domain;
https://commons.wikimedia.org/wiki/File:Hornwort_structures.jpg)
The following is multiple choice question (with options) to answer.
Which type of bryophytes are named for their horn-like sporophytes? | [
"tapeworms",
"hornworts",
"flatworms",
"arthropods"
] | B | Liverworts, hornworts, and mosses are modern bryophytes. Liverworts are named for the liver-shaped leaves of some species. Hornworts are named for their horn-like sporophytes. |
SciQ | SciQ-4550 | zoology, entomology
Title: How do insects know what is edible? What is the current scientific consensus on how insects innately know what is food and not food? If they are introduced to new food sources do they experiment with eating the new food? Could you teach a preying mantis to eat beef? Insect feeding behaviour is generally triggered by one or more conditions which may include colour, shape, chemical traces or temperature.
Insects generally locate food based on some combination of olfactory, thermal and visual queues (colour and shape). If their minimum criteria are met to specified tolerance, they will attempt to feed on whatever is nearby using their usual feeding method.
When these conditions appear on the 'wrong' target, it attracts insects and triggers feeding attempts. Insects can be triggered to feed on atypical food sources if the relevant aspects of their environment match those of their normal feeding environments. For example, here is a report from a professor of entomology recollecting his observations of being bitten by pea aphids while handling plants, which he assumes is because of the scent on his hands.
We can exploit this in various ways for research. One is for artificial blood-feeding of insects: most systems, like the Hemotek membrane feeding system, warm blood to the body temperature of the host. They do not normally resemble a target host in any other way. Some blood-feeding insects have very specific requirements for temperature (for example they will only feed on blood if it is heated to the body temperature of birds; the same blood heated to mammalian body temperature will be ignored) but we do not need to make the target look or smell like the natural host. Other species may need olfactory cues, which can be provided by researchers rubbing the membranes on their forearms before placing them on the feeding system, or by breathing on cages as you add the food.
A second way we exploit this is for insect traps. Although not all traps work this way, some work by mimicking the host and attracting insects that are looking for a meal. This can be via olfactory/chemical mimicry (for example carbon dioxide baited traps - try Googling "CO2-baited traps") or visual. Different degrees of visual 'deception' may be needed; for instance to attract tsetse flies, colour is important but shape is not:
The following is multiple choice question (with options) to answer.
What do you call a carnivore that eats mainly insects? | [
"pescatorian",
"omnivores",
"predator",
"insectivores"
] | D | Mammals may be herbivores, carnivores, or omnivores. Some carnivore mammals eat mainly insects and are called insectivores. Some omnivore mammals eat mainly fruits and are called frugivores. |
SciQ | SciQ-4551 | organic-chemistry, bond, lewis-structure
Title: How do I draw a Lewis diagram after drawing the orbital diagram The question says "Oxygen can form compounds with every period 3 element except argon. Determine which would be ionic or covalent compounds, and draw Lewis diagrams to represent each one." I started with oxygen and fluorine and I'm having a hard time. I don't know if there should be lone pairs, double bonds, or even lone electrons.Here's my attempt at it: First of all, oxygen follows "the octet rule", which states that certain elements are stable when they have 8 electrons around them. Now this rule is by no means absolute, does not work with d orbitals onward, and should only be used in very elementary chemistry, unless you actually know its cause. In the case of that picture, you are missing 2 non-bonding electrons on the oxygen.
Remember that a covalent bond means that electrons are being shared by the 2 atoms. In the case of O and F, the pauling electronegativities are quite similar, so the electrons are actually "shared".
However, when you try to put oxygen together with group 1 or group 2 elements, you will find very different electronegativity values. What this means is that oxygen has much more affinity to electrons than Na or Mg. The rule I was taught at school was that a difference of 2 or more in electronegativity between the elements results in ionic compounds, meaning the oxygen "steals" the electrons, becoming a negative anion, whereas Na for example becomes a positive one.
The last guideline you should take into account, is that an atom tends to lose or gain electrons because it "likes" to have its most outer shell full. So when you look at the principal quantum number ($n$) of the most outer shell, you should create compounds where it is full. In the case of oxygen, that quantum number is $2$, which can have 8 electrons, hence the octet rule. For Na, you have 1 electron in $n=3$, so if the atom looses that electron, it will become more stable, therefore we have $\ce{Na+}$.
The following is multiple choice question (with options) to answer.
Oxygen has the second highest electronegativity of any element; consequently, it prefers to share or accept electrons from other elements. only with fluorine does oxygen form compounds in this? | [
"negative Oxidation States",
"liquid oxidation states",
"positive oxidation states",
"chemical oxidation states"
] | C | Oxygen has the second highest electronegativity of any element; consequently, it prefers to share or accept electrons from other elements. Only with fluorine does oxygen form compounds in positive oxidation states. |
SciQ | SciQ-4552 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
What component of cells is present in plant and bacterial cells but not animal cells? | [
"nucleus",
"mitochondria",
"plasma",
"cell wall"
] | D | Animal Cell. The shape of an animal cell is not constrained by a rigid cell wall. A bacterial cell is shown above for comparison. |
SciQ | SciQ-4553 | 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.
Energy cannot be created or destroyed - it can only change what? | [
"shape",
"form",
"kind",
"fluid"
] | B | All living things need energy. They need it to power the processes of life. For example, it takes energy to grow. It also takes energy to produce offspring. In fact, it takes energy just to stay alive. Remember that energy can’t be created or destroyed. It can only change form. Energy changes form as it moves through ecosystems. |
SciQ | SciQ-4554 | mycology
Title: How do fairy rings propagate? It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores? When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas the newly formed mycelium (underground) will develop the familiar mushrooms above ground and this will result in a fairy ring.
The following is multiple choice question (with options) to answer.
Most fungi can reproduce in which 2 ways? | [
"sexually and autonomously",
"binary fission and fusion",
"sexually and binary fusion",
"asexually and sexually"
] | D | The majority of fungi can reproduce both asexually and sexually. This allows them to adjust to conditions in the environment. They can spread quickly through asexual reproduction when conditions are stable. They can increase their genetic variation through sexual reproduction when conditions are changing and variation may help them survive. |
SciQ | SciQ-4555 | bond, electrons, lewis-structure, valence-bond-theory
Title: Why do unbonded electrons exist in pairs? Basically the term which we use to refer them is lone pair. In Lewis structure why we represent those unbonded electron in pairs. Like here (structure of SO2)
Here if we assume both the unbonded electrons to be existing in pairs then it's geometry will be different from what we would observe in case when both electrons exists freely (without pair).
So why we basically consider those electrons to be existing in pair? Is it any kind of observation or any theory or both?
Why unbonded electrons exits in pair
Unbonded, non-bonded or lone pair electrons are terms used to describe electrons that surround an atom, but don't play a direct role in bond formation. Importantly, these electrons do not always exist as lone pairs where the electrons reside in a common orbital. Sometimes they exist as single non-bonding electrons residing in separate orbitals.
Let's compare the non-bonding electrons in water to those in molecular oxygen. Here is an illustration of the molecular orbital arrangement for water. As we fill the orbitals with electrons according to the Aufbau Principle we arrive at the point where we have two electrons remaining and the next available molecular orbital is the $\ce{1b_1}$ orbital. According to Hund's Rule, we must place these two electrons into this orbital with their spins paired. The result is that we have two non-bonding electrons paired up in the same orbital - a lone pair of electrons.
The following is multiple choice question (with options) to answer.
What is a pair of valence electrons in a bonded atom that does not participate in bonding called? | [
"opposite pair",
"isolated pair",
"lone pair",
"hostile pair"
] | C | A pair of valence electrons in a bonded atom that does not participate in bonding is called a lone pair. Lone pair electrons contribute to molecular shape. |
SciQ | SciQ-4556 | redox, oxidation-state
Title: Terminology of redox reactions: which species are the oxidizing and reducing agents? I've got a question regarding 'notation' for redox reactions. Suppose you are asked to identify the oxidizing and reducing agents for a simple reaction like this one:
$$\ce{Cl2(aq)}+\ce{2KI(aq)} \longrightarrow \ce{2KCl(aq)}+\ce{I2(aq)}$$
Now are you supposed to say $\ce{Cl}$ is the oxidizing agent or $\ce{Cl2}$? Also, is $\ce{KI}$ the reducing agent or $\ce{I}$ or $\ce{I^-}$?
By the way, if you were instead asked to identify which species got oxidized, would you again say that $\ce{KI}$ is oxidized or $\ce{I}$ or $\ce{I^-}$? Ignoring spectator ions,
$\ce{Cl2 +2 I- ->2Cl- +I2}$
So, $\ce{Cl2}$ is the oxidant and $\ce{I-}$ is the reductant.
The following is multiple choice question (with options) to answer.
When a metal is oxidized and a nonmetal is reduced in a redox reaction, what is the resulting compound called? | [
"magnetic compound",
"ionic compound",
"alloy",
"soluble compound"
] | B | There are many other examples of redox reactions in which two neutral elements combine to make a compound. These often take the form of a metal being oxidized and a nonmetal being reduced, resulting in an ionic compound. Two nonmetallic elements can also undergo a redox reaction of this type, in which the less electronegative element is oxidized and the more electronegative element is reduced. |
SciQ | SciQ-4557 | microbiology, bacteriology, bacteriophage
Cvirkaite-Krupovic V, Krupovic M, Daugelavicius R, Bamford DH. Calcium ion-dependent entry of the membrane-containing bacteriophage PM2 into its Pseudoalteromonas host. Virology. 2010 Sep 15;405(1):120-8.
McKenna R, Bowman BR, Ilag LL, Rossmann MG, Fane BA. Atomic structure of the degraded procapsid particle of the bacteriophage G4: induced structural changes in the presence of calcium ions and functional implications. J Mol Biol. 1996 Mar 8;256(4):736-50.
Plevka P, Kazaks A, Voronkova T, Kotelovica S, Dishlers A, Liljas L, Tars K. The structure of bacteriophage phiCb5 reveals a role of the RNA genome and metal ions in particle stability and assembly. J Mol Biol. 2009 Aug 21;391(3):635-47.
The following is multiple choice question (with options) to answer.
A biofilm is a colony of prokaryotes that is stuck to what? | [
"the bottom",
"skin",
"surface",
"the middle"
] | C | Some prokaryotes form structures consisting of many individual cells, like the cells in Figure below . This is called a biofilm. A biofilm is a colony of prokaryotes that is stuck to a surface. The surface might be a rock or a host's tissues. The sticky plaque that collects on your teeth between brushings is a biofilm. It consists of millions of prokaryotic cells. |
SciQ | SciQ-4558 | reproduction, digestion, sexual-reproduction
Hazardous components of pollen:
Trace amounts of hepatotoxic pyrrolizidine alkaloids were found in pollen of Echium vulgare, E. plantagineum, Senecio jacobaea, S. ovatus, and Eupatorium cannabinum (Boppre et al., 2008). In Middle and Northern Europe these pollens are not among the main pollen grains gathered by bees, however in Southern Europe the two Echium plants are more diffused and are gathered by bees in larger amounts (Campos et al., 1994; Serra Bonvehi, 1997). [Source 1] (Page 5)
Therefore, it should undergo tests to approve it's purity as allergies can be caused.
References:
1 : Future of bee pollen(Research gate)
2 : Pollen composition and standardisation of analytical methods(Research gate)
3 : Hollow pollen shells to enhance drug delivery(NCBI)
4 : Bee pollen: chemical composition and therapeutic application(NCBI)
5 : Biological activities of commercial bee pollens: antimicrobial, antimutagenic, antioxidant and anti-inflammatory(NCBI)
6 : Biological and therapeutic properties of bee pollen: a review(NCBI)
The following is multiple choice question (with options) to answer.
What is the part of the flower that produces pollen? | [
"cones",
"stamen",
"leaves",
"stigma"
] | B | stamens The part of the flower that produces pollen. |
SciQ | SciQ-4559 | acid-base, aqueous-solution, solutions
Title: Are all solutions of weak acid/bases buffers? I am having a difficult time understanding what makes a buffer a buffer.
Buffers in my textbook are defined as a solution of a weak acid or base and their conjugate acid/base. So if I were to just dissolve acetic acid (a weak acid) in water why would this not be defined as a buffer. Acetic acid incompletely dissociates into an acetate ion (the conjugate base) and a Hydrogen ion. Why is it that for a base to be made the acetic acid would have to be mixed with something like Sodium acetate if acetic acid incompletely dissociates into a conjugate base in the first place? Could someone please help me understand why this is the case? The term "buffer" implies a purpose of resisting changes in pH when small amounts of acid or base are added. The buffer will be most effective when the pH equals the pKa of the acid. This is when there are equal amounts of acid and conjugate base. For each pH unit the system deviates from pH=pKa, the buffer is about a factor 10 less effective.
If you just dissolve acetic acid in water, yes it is true that there will be a small fraction that ionizes to yield the conjugate base, acetate. However, the pH will be far from the pKa of acetic acid, and the system will not be very effective as a buffer.
In summary, "buffer" is not a very precise term, but it implies that there are significant amounts of both the acid and the conjugate base.
The following is multiple choice question (with options) to answer.
What neutralizes the acidity of chyme and acts as a buffer? | [
"bile",
"the bicarbonate",
"the chloride",
"the small intestine"
] | B | |
SciQ | SciQ-4560 | seismology, earthquakes, plate-tectonics
Title: Fault representation In most illustrations and diagrams of the types of faults, there is always something similar. I noticed that there is a side of the hanging wall and foot wall which is slanted.
We're supposed to make a models for each type of fault; however, the material to be used will be difficult to cut diagonally. I'd like to know if it is necessary to have one side slanted? Or if having it vertical fine.
Please mention sources too. Thank you. Faults are results of stress. The direction of the stress controls what kind of fault that is formed. The most fundamental reason for a fault to occur is horizontal compression or extension, even if it's often more complicated in reality.
Your two examples are dip-slip faults, with a vertical displacement as a result of horizontal stress.
In your first example, the normal fault. The total distance (from left to right) is increased. There has been an extension of the crust. If the fault plane would have been vertical, no distance would have been gained.
In the second example, the reverse fault, the distance is decreased. It's been a horizontal compression of the crust. The dip of a reverse fault is usually rather steep. If the dip is lower, you'll rather form a ramp. Typical for thrust faults.
Vertical fault planes are associated with strike-slip faults or ring faults above collapsing calderas or sinkholes. It's also common, but not for textbook examples of dip-slip faults.
So, unless you are showing a strike-slip fault, you have to find a way to cut diagonally. Do measure the horizontal displacement!
Addition about making fault models:
We made a layer cake for a college some time ago and (of course) wanted to have a fault in it. The simplest way was to make a reverse fault, erode the uppermost layer of the hanging wall block and assume that the lowest exposed layer was of the same lithology (chocolate sandstone reservoir rock). However, it took some geoenginering to make it look good and we decided to make an impact crater next time.
The following is multiple choice question (with options) to answer.
What type of stress causes horizontal motions in strike-slip faults? | [
"blunt",
"hot",
"cold",
"shear"
] | D | |
SciQ | SciQ-4561 | biochemistry, molecules, polymers, chemical-biology
A monomer is the simplest building block of a macromolecule with the properties of that macromolecule. They can be strung together to produce a macromolecule (usually by dehydration synthesis).
I would have no problem with these definitions if not for my teacher mentioning once that some monomers can also be macromolecules by themselves. Because some monomers of certain macromolecules- such as the monosaccharide glucose vs. the disaccharide sucrose or the polysaccharide amylose - can act on their own as an essential and functional carbohydrate, they are macromolecules by themselves.
Is this true? For example, could glucose be a macromolecule by itself?
Thanks. I can't think of an example where a biological monomer would be a macromolecule.
Definitions of macromolecule vary, usually by molecular weight or number of monomers (repeat units).
Personally, I'd go with ~1000 Dalton for a minimum, but the original definition of 1000 atoms is a good start too.
In any case, no biological monomer, including glucose will function the same as a macromolecule.
Consider starch - a macromolecule of sugars. It doesn't dissolve as quickly as simple sugar and has different physical properties.
Update
To clarify my comments.. Macromolecules or polymers are made up of monomers the way words are made up of letters. So no, a glucose molecule isn't really the same as a macromolecule, just like "R" is not a word.
Yes, macromolecules can be used to make larger assemblies like microtubules, filaments, etc., much the same way that words can form sentences and paragraphs.
In the polymer literature there's even the concept of a "macromonomer" referring to a monomer that is already large in size.
In my opinion though, the basic constituents (monomers) are still amino acids, nucleic acids, sugars, etc. These are not macromolecules.
The following is multiple choice question (with options) to answer.
The structure of the boeing 787 has been described as essentially one giant macromolecule, where everything is fastened through cross-linked chemical bonds reinforced with this? | [
"carbon fiber",
"non-covalent interaction",
"metal-metal bonds",
"nitrogen fiber"
] | A | carbon fiber–epoxy and boron fiber–epoxy composites. Compared with metals, these materials are 25%– 50% lighter and thus reduce operating costs. Similarly, the space shuttle payload bay doors and panels are made of a carbon fiber–epoxy composite. The structure of the Boeing 787 has been described as essentially one giant macromolecule, where everything is fastened through cross-linked chemical bonds reinforced with carbon fiber. Metal-matrix composites consist of metals or metal alloys reinforced with fibers. They offer significant advantages for high-temperature applications but pose major manufacturing challenges. For example, obtaining a uniform distribution and alignment of the reinforcing fibers can be difficult, and because organic polymers cannot survive the high temperatures of molten metals, only fibers composed of boron, carbon, or ceramic (such as silicon carbide) can be used. Aluminum alloys reinforced with boron fibers are used in the aerospace industry, where their strength and lightweight properties make up for their relatively high cost. The skins of hypersonic aircraft and structural units in the space shuttle are made of metal-matrix composites. Ceramic-matrix composites contain ceramic fibers in a ceramic matrix material. A typical example is alumina reinforced with silicon carbide fibers. Combining the two very high-melting-point materials results in a composite that has excellent thermal stability, great strength, and corrosion resistance, while the SiC fibers reduce brittleness and cracking. Consequently, these materials are used in very hightemperature applications, such as the leading edge of wings of hypersonic airplanes and jet engine parts. They are also used in the protective ceramic tiles on the space shuttle, which contain short fibers of pure SiO2 mixed with fibers of an aluminum–boron–silicate ceramic. These tiles are excellent thermal insulators and extremely light (their density is only about 0.2 g/cm3). Although their surface reaches a temperature of about 1250°C during reentry into Earth’s atmosphere, the temperature of the underlying aluminum alloy skin stays below 200°C. |
SciQ | SciQ-4562 | nuclear-physics, kinetic-theory
Title: Usefulness of high molecular speeds in nuclear fusion reactions How do molecules having speeds many times greater than mean speed help in making nuclear fusion reactions in a laboratory? Nuclear fusion is a process in which two or more nuclei are combined to form a different atomic nucleus.
It takes a lot of energy to force nuclei to fuse, even with the lightest elements, like hydrogen in the Sun.
Now the release of energy and the fusion iself goes down between two forces:
strong force (residual strong force, that is the nuclear force), that keeps the neutrons and protons together
EM repulsion, that keeps protons away
When you accelerate nuclei to high enough speeds, they can overcome this EM repulsion, so they can be brought close enough, where the nuclear force is strong enough to hold them together.
At large distances, two naked nuclei repel one another because of the repulsive electrostatic force between their positively charged protons. If two nuclei can be brought close enough together, however, the electrostatic repulsion can be overcome by the quantum effect in which nuclei can tunnel through coulomb forces.
When a nucleon such as a proton or neutron is added to a nucleus, the nuclear force attracts it to all the other nucleons of the nucleus (if the atom is small enough), but primarily to its immediate neighbours due to the short range of the force.
https://en.wikipedia.org/wiki/Nuclear_fusion
The following is multiple choice question (with options) to answer.
What is the term for the process in which two atomic nuclei fuse together to make a single nucleus? | [
"binding",
"absorption",
"fusion",
"fission"
] | C | Fusion is the process in which two atomic nuclei fuse together to make a single nucleus. Energy is released in the form of nuclear particles, neutrons, and gamma-rays. |
SciQ | SciQ-4563 | human-biology, eggs
In order to form a zygote (fertilized egg) to develop properly into a fetus it has to be an environment to meet it needs. In a female uterus all these needs are met but replicating them might be difficult. An artificial womb would have to be able to provide nutrients, oxygen, and channels for the development process of a fetus as well as system to expel (birth) the fetus once its development is complete. So can today's technology and science do all this? In theory yes, if resources and time where dedicated (and red tape cut) it would be possible to develop a fertilized egg in an artificial environment within the foreseeable future. There have been multiple experiment where artificial wombs were implanted with fertilized eggs and began to grow but were stopped due to legality.
I encourage you to read the following Wikipedia and motherboard articles regarding artificial wombs and ectogenesis.
https://en.wikipedia.org/wiki/Artificial_uterus
http://motherboard.vice.com/read/artificial-wombs-are-coming-and-the-controversys-already-here
*Note there is a lot of biology I did not mention regarding zygote to fetus development which is the biggest question/obstacle that ectogenesis might face
The following is multiple choice question (with options) to answer.
In human beings, when a female becomes pregnant, what is fertilized and then embedded in the uterus? | [
"egg",
"sperm",
"dna",
"follicle"
] | A | If the egg is fertilized, the egg makes its way through the fallopian tube into the uterus, where it imbeds into the thick lining. When this occurs, the monthly cycle stops. The monthly cycle does not resume until the pregnancy is over. |
SciQ | SciQ-4564 | meteorology, climate-change, gas, pollution
If you are interested in Greenhouse Gases (e.g. methane, carbon dioxide, CFCs, nitrous oxide), the EPA has a separate site for those emissions since they are not part of the same regulatory framework http://www.epa.gov/climatechange/ghgemissions/ . Greenhouse gases typically do not cause adverse health effects for plants or animals on land. However, they have long-term radiative effects (e.g. the greenhouse effect) because they stay in the atmosphere for many years and trap infrared light. These long-term radiative effects are what can change climate and consequently land cover. Furthermore, most of the excess carbon is absorbed by the ocean, which creates carbonic acid. Increased acidity of the ocean causes severe problems for marine ecosystems.
The EPA states that in 2012 the CO2 equivalent GHG emissions for the USA by sector was:
The following is multiple choice question (with options) to answer.
What has increased the greenhouse effect? | [
"temperature changes",
"ozone depletion",
"climate change",
"human actions"
] | D | Greenhouse gases in the atmosphere absorb heat. This is called the greenhouse effect and it makes the planet warmer. Human actions have increased the greenhouse effect. |
SciQ | SciQ-4565 | dna, chromosome
Title: Are human chromosomes connected or separate molecules? Do the 46 human chromosomes form a single unbroken DNA helix? Or is it rather that a human's genome consists of 46 disconnected helices?
If it is the former, does the common numbering scheme for the chromosomes have any correlation to their actual ordering in the one large strand?
If is the latter, is there a convention on how the chromosomes are ordered in genomic datasets? Also, is there a clear understanding of how sister chromosomes "find" each other in Meiosis I?
Generally, during periods when Mitosis/Meiosis are not occurring, what's a good physical picture for how the chromosomes are physically arranged (e.g. a bowl of 46 spaghetti noodles, or maybe the sister chromosomes always stay close together, etc)
thanks! Each chromosome is a pair of distinct, separate DNA molecules. A chromosome of an eukaryotic cell nucleus is a (long) helix of two linear molecules and so has two ends, which are called telomeres. DNA naturally forms a double helix with its complementary DNA molecule, and the double helix can further curl in what are called supercoils.
In humans, the chromosomes occur in 23 pairs (totaling 46). Except for the sex chromosome pair, each member of the pair is identical in appearance in a karyotype (picture) and each such pair has a number assigned from 1 to 22; the numbering generally follows the size of the chromosome, with chromosome 1 being the longest. In mammals, the sex chromosomes in a male are quite different in size and are labelled X and Y; a female has two identical X chromosomes.
The following is multiple choice question (with options) to answer.
How many pairs of chromosomes are there? | [
"23",
"16",
"24",
"25"
] | A | During anaphase I the spindle fibers shorten, and the homologous chromosome pairs are separated from each other. This occurs as the chiasmata are severed, pulling homologous chromosomes apart. One chromosome from each pair moves toward one pole, with the other moving toward the other pole, resulting in a cell with 23 chromosomes at one pole and the other 23 at the other pole. Each chromosome still contains a pair of sister chromatids; the sister chromatids remain attached at the centromere. |
SciQ | SciQ-4566 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
What structure passes oxygen and nutrients to a growing fetus in mammals? | [
"uterus",
"vas deferens",
"spinal cord",
"placenta"
] | D | The majority of mammals are placental mammals. These are mammals in which the developing baby is fed through the mother's placenta. Female placental mammals develop a placenta after fertilization. A placenta is a spongy structure that passes oxygen, nutrients, and other useful substances from the mother to the fetus. It also passes carbon dioxide and other wastes from the fetus to the mother. The placenta allows the fetus to grow for a long time within the mother. |
SciQ | SciQ-4567 | general-relativity, gravity, visible-light, electromagnetic-radiation, photons
Title: Is the Light REALLY bent? I've learned that always, the light go straight. The as Einstein's gravitation therory, the light can be bent in bented space-I mean, curved space.
Actullay, I think that if we in the space which interrupted by gravity, we can SEE a straight light. (The direction can be choosed by observer)
So, what is right?? Well this matter is probably mostly quibbling about fine definitions, but light follows so-called lightlike geodesics in spacetime, so as a matter of principle I would say that it follows "straight lines". A geodesic is simply the notion of a straight line generalized to the case where the geometry in question does not fulfill Euclid's parallel postulate. You can't do any better that this to generalize the notion of a straight line in Euclidean geometry.
Now, this generalization does not have all the properties of a Euclidean straight line - we've lost the parallel postulate, after all. In particular, the geometric distortion means that it can "look" bent from the point of view of a distant observer (in the sense that its projection onto a distant, inertial astronomer's field of view is a curved line). And it is no good defining "straight" to be something that projects onto a straight line on this astronomer's field of view, because that definition would be observer dependent. You can't conserve any more of the notion of straightness in non-Euclidean geometry than what is encapsulated in the definition of the notion of geodesic.
A minor pedantic point: the principle that light travels in straight lines only holds if the wavelength / frequency is much smaller than the length scale over which spacetime deviates significantly from flatness. Otherwise, diffraction effects become significant.
The following is multiple choice question (with options) to answer.
Light from a distant galaxy can travel different paths to the earth because it is bent around an intermediary galaxy by what? | [
"radiation",
"strength",
"variation",
"gravity"
] | D | Figure 34.12 (a) Light from a distant galaxy can travel different paths to the Earth because it is bent around an intermediary galaxy by gravity. This produces several images of the more distant galaxy. (b) The images around the central galaxy are produced by gravitational lensing. Each image has the same spectrum and a larger red shift than the intermediary. (credit: NASA, ESA, and STScI). |
SciQ | SciQ-4568 | species-identification, mycology
Title: What is these mushrooms in my indoor pot? I am living in Japan and in summer, it's very hot and humid even inside my room.
Today, I've found two mushrooms in the pot of a plant.
What is this species? It's very surprising than within one day they grew like this. They do look a lot like a common mushroom called "shaggy mane" mushroom (Coprinus comatus). This may not be a correct identification though, so do not eat them. They are widespread around the world, but usually grow outside.
Yes it is amazing how rapidly the fruiting body of many fungi can grow. I am providing an interesting Wikipedia link with more information. You can also search to find other images using Google images online.
https://en.wikipedia.org/wiki/Coprinus_comatus
The following is multiple choice question (with options) to answer.
What is the fruiting body that occurs after two hyphae mate and form a mycelium with sporangia? | [
"mushroom",
"mold",
"fungus",
"yeast"
] | A | |
SciQ | SciQ-4569 | literature-request
For as long as I can remember (okay, since 2002) the standard source of this type has been the Web of Science. It covers all sciences (and engineering, social science) so you have to restrict your search with sensible combinations of keywords, categories, and journal names, but it's the closest thing to a neutral database that we have.
I don't find Google Scholar to be a good substitute. It doesn't have a very good signal to noise, you'll often get multiple hits to entries of the same article in different databases, but direct links to the actual journal article can appear quite low down on the list. I know this has been a problem for EGU/Copernicus journal articles, which appear much lower down than social network (e.g., ResearchGate) links.
The problem with both of those tools though is the sheer volume of articles. So much is published these days that it's simply not possible for anyone to exhaust the search. My lab often recruits post-docs into Earth science positions from other disciplines (e.g., maths, physics) and knowing where to start or finish with the literature can be intimidating for them. What they need is for some experienced researchers in the field to filter the literature for them, which is why I normally recommend reading recent review articles as a way of gauging the knowledge boundaries.
There are journals dedicated to review articles, e.g.,
Earth Science Reviews
Review of Geophysics
Nature Reviews Earth & Environment
Encyclopedia of Geosciences
and doubtlessly there are more than I've forgotten. Some publishers also curate collections of important articles from across their journals, e.g.,
Nature Collections
AGU Grand Challenges
Read the references you find in those and maybe go one level deeper and then you'll have done your due diligence. I still stumble across seams of papers I've missed in fields that I've worked in for years and it's never been a problem; no one expects you to be exhaustive in your search.
The following is multiple choice question (with options) to answer.
What branch of science aims to understand all about our planet and its environments? | [
"immunology",
"biology",
"petrology",
"earth science"
] | D | If someone asks you, “What is science?” you might say that it’s a bunch of facts and explanations. But that’s only part of the story. Science is a knowledge base. But science is also a way of learning about the world. Earth science is about our planet and its environments. Earth scientists study Earth’s surface and interior. They study why volcanoes erupt and why some places are mountainous and some are entirely flat. Some Earth scientists are interested in the weather. Others want to know about the oceans. There are even Earth scientists who apply what they know about Earth to learning about space. Some Earth scientists do a lot of their work in the field, as seen above. |
SciQ | SciQ-4570 | human-biology, evolution
Humans are off the charts in the amount of resources we invest in our children - our lives are 1/4 to 1/3 over before we sometimes leave our parents household (in some societies of course they never leave the house, but step into an extended family). This may be one of the reasons we are so successful as a species - we live in practically every place we possibly could and have no danger of competition from any other living thing excepting ourselves.
The grandmother effect is essentially the idea that if women, who are more attached to the offspring in more cases than fathers, continue to live and help support the grandchildren and make them more successful, then this will allow post menopausal women to have a longer lifespan (which they do).
The evolutionary biologist Sara Hrdy, emeritus UC Davis, has written quite a bit about the nuances of the evolution of the role of motherhood - reading some of her articles or books might give you a deeper sense of how profoundly filial love has shaped human beings.
--- more answer this stuff may or may not be worth reading depending on how broadly you want to understand this question...
Its important to say that many of the expansions of human average human lifespan have not been genetic. Its commonly cited that sewer systems, clean water, antibiotics and plentiful food are the three most important factors in human lifespan - and before modern developed world nations, the average lifespan of human beings was somewhere in the 30s. And there are significant lifespan differences in regions where these factors and others (education of women, access to prenatal and early care etc) are available.
Studies continue to be published that examine environmental and lifestyle factors compared to genetics and it seems that environment and lifestyle can make an astounding difference.
But genetics undoubtedly has a role to play here too. There are probably some individual humans and animals which have evolved to live longer. This has been found to be genetically related in some humans by demographics and family lines.
The following is multiple choice question (with options) to answer.
Prokaryotes are successful because of the ________ of reproduction in favorable environments | [
"order",
"speed",
"volume",
"cycle"
] | B | |
SciQ | SciQ-4571 | zoology, species-identification, marine-biology, invertebrates
Title: Species identification - greenish blue ocean worm (nudibranch?) in Perhentian Islands, Malaysia We found this on a beach at the Perhentian Islands, Malaysia in March, 2016 and cannot identify it. It's some sort of worm-type creature with many legs and bluish back about 15cm long. The legs undulated along the body as it swam.
back:
belly side: It's hard to identify from the photos provided, but I think it is Chloeia flava (a species of polycaete worm, within the phylum Annelida), also known in English as the "Golden Fireworm".
The size is roughly similar to what you describe (they are typically about 7-10 cm long). The individual you observed looks like it lives in sandy bottom environments (not a typical environment for a nudibranch), and this worm does also. It is commonly found all across the warmer Indo-Pacific as well, and looks like the individual observed in your photo.
If it is not this species, I think it is another species of the same family, Amphinomidae.
The following is multiple choice question (with options) to answer.
Where do benthos live in oceans? | [
"On the ocean surface",
"In deep water",
"on the ocean floor",
"In coral reefs"
] | C | Three main groups of ocean life are plankton, nekton, and benthos. Plankton float in the water. Nekton swim through the water. Benthos live on the ocean floor. |
SciQ | SciQ-4572 | muscles
Title: What is meant by a muscle fiber being glycerinated? I was popped this questions today, "what is a glycerinated muscle fiber, and what is required for its contraction," and had little idea. I'm assuming the question is "what's required for its contraction as compared to normal muscle tissue?"
There's a limited amount of information out there about this. It appears that it is a type of in vitro system requiring special preparation of typical muscle tissue. I was wondering if anyone here had a little more information. Is this something that's just used in teaching lab exercises? From: http://www.acad.carleton.edu/curricular/BIOL/classes/bio126/Documents/Lab_5.pdf
Glycerination disrupts the membranes of the muscle cells, ruptures mitochondria, and leaches out soluble constituents such as ATP and inorganic ions. However, glycerinated muscle retains the organized structural array of myosin thick filaments and actin thin filaments, actin-associated proteins like troponin and tropomyosin which regulate contraction, and the functional capacity for contraction.
I would expect that because the sample has lost ATP and inorganic ions, you would need to supply ATP (the source of energy), $Mg^{2+}$ (which is necessary for ATP hydrolysis) and $Ca^{2+}$ (to induce the contraction).
The following is multiple choice question (with options) to answer.
Hundreds of organelles called myofibrils, made up of two types of protein filaments, are contained in each fiber of what? | [
"cartilage",
"muscle",
"bone",
"hair"
] | B | Each muscle fiber contains hundreds of organelles called myofibrils . Each myofibril is made up of two types of protein filaments: actin filaments, which are thinner, and myosin filaments, which are thicker. Actin filaments are anchored to structures called Z lines (see Figure below ). The region between two Z lines is called a sarcomere . Within a sarcomere, myosin filaments overlap the actin filaments. The myosin filaments have tiny structures called cross bridges that can attach to actin filaments. |
SciQ | SciQ-4573 | star, size
Title: How do we know what the biggest star is? Kurzgesagt claims that the largest (observable) star in the universe would be Stephenson 2-18 which is in line with Wikipedia:
It is among the largest known stars, if not the largest, and one of the most luminous red supergiants, with an estimated radius around 2,150 times that of the Sun, which corresponds to a volume nearly 10 billion times bigger than the Sun.
Furthermore, Wikipedia says
The open cluster Stephenson 2 was discovered by American astronomer Charles Bruce Stephenson in 1990 in the data obtained by a deep infrared survey.
I stumbled upon that statement for two reasons:
The survey was made in 2010, so if we again would make a survey with newer, higher resolution data (which I assume we might have in the mean time), would we find other objects even bigger?
How are we sure that St2-18 was indeed the largest object within the given survey? Technically speaking, one would have to calculate at least the distance or lumnosity for each object of the survey?
In a nutshell: How sure are we (in percent) that St2-18 is right now, in 2020, still the largest observed star?
Related
The following is multiple choice question (with options) to answer.
What is the largest known virus? | [
"polyomavirus",
"influenza virus",
"pneumonia virus",
"mimivirus"
] | D | The largest known virus, called mimivirus, is so large that scientists first mistook it for a bacterium. It was first discovered in amoeba, in 1992, and was identified as a virus in 2003. Scientists believe that mimivirus may cause certain types of pneumonia in humans. The core contains DNA, with the majority of the DNA in genes, and only 10% DNA of unknown function ("junk" DNA). |
SciQ | SciQ-4574 | physical-chemistry, thermodynamics, polymers
Title: Is temperature of crystallisation same as melting point temperature for polymers? Melting point tends to be a temperature range. Is it true that the temperature of crystallisation is the highest temperature at which the polymer melts and thus there is some distinction between temperature of crystallisation, Tc and temperature at melting point, Tm?
Is temperature of crystallization same as melting point temperature for polymers?
In a word: NO.
If you undrestand what the glass transition, crystallization and melting temperatures are it will make sense why they are not the same. This paper does an excellent job at explaining the three concepts but I will summarize.
The glass transition temperature is the temperature where polymer chains become sufficiently mobile that the material transforms from being brittle to being soft and plastic (neither exo- nor endothermic, but does the heat capacity does increase). The crystallization temperature is the temperature where the molecules are mobile enough to rearrange into ordered arrangements (crystallize not decrystallize; this is an exothermic process; see plot below). The melting temperature is where the polymer chains can freely move and ordered arrangements are disrupted (this annihilates any prior crystallization; an endothermic process).
Source: Plastic Technology Laboratories
The following is multiple choice question (with options) to answer.
The temperature at which something melts is refered to as what? | [
"precipitation point",
"boiling point",
"melting point",
"evaporation point"
] | C | Both of these people are participating in a board sport, but the man on the left is snowboarding in Norway while the woman on the right is sandboarding in Dubai. Snow and sand are both kinds of matter, but they have different properties. What are some ways snow and sand differ? One difference is the temperature at which they melt. Snow melts at 0°C, whereas sand melts at about 1600°C! The temperature at which something melts is its melting point. Melting point is just one of many physical properties of matter. |
SciQ | SciQ-4575 | acoustics, metals, phonons, solid-mechanics
Title: Is it possible to reduce the sound, when two metal objects collide (perhaps with some coating) without reducing the rigidity of the surface? I have a system, where there are ball bearings on the pistons that clamp the metal plate with special dents for ball bearings. The system should be precise, because it is used for microscopy. It also should be as noiseless as possible. It also should be fast, so the impact at high velocity is inevitable.
I've thought of introducing some resin coating, but it will reduce the rigidity. Are there any solutions for this problem? Is there any strong relationship between sound and rigidity? I believe that there may be some rigid materials that somehow don't favor phonons. Unfortunately, anything that reduces noise without slowing the system down is going to do it by sacrificing rigidity.
If it is within your engineering parameters, you might introduce a damper on the pistons that engages within a millimeter or so of the ultimate extension of the piston. By slowing the piston down before impact, you can reduce the noise, without compromising the rigidity of the surface. It would have to be just before impact, slowing over a very short distance, in order to keep your system from being too slow. (I'm thinking of something akin to the dampers that are used on kitchen drawers, that slow the drawer down just before the drawer slams shut.)
The following is multiple choice question (with options) to answer.
Solid bedrock vibrates less and therefore does less of what to bedrock? | [
"block",
"butress",
"damage",
"dampen"
] | C | Ground type. Solid bedrock vibrates less than soft sediments, so there is less damage on bedrock. Sometimes sediments become saturated with water. They then undergo liquefaction and become like quicksand ( Figure below ). Soil on a hillside may become a landslide. |
SciQ | SciQ-4576 | computability, turing-machines, physics
Title: Can normal physics laws be simulated in Digital physics? Physics is defined as the study of an object {matter or energy} with its interaction with other objects:
Physics is the study of matter, energy, and the interaction between them.
On the other hand, Digital physics is based on computations and information.
Digital physics is a collection of theoretical perspectives based on the premise that the universe is, at heart, describable by information, and is therefore computable.
The following is multiple choice question (with options) to answer.
What branch of science is defined as the study of matter? | [
"astrophysics",
"biology",
"chemistry",
"geology"
] | C | 1.8 End-of-Chapter Material Chapter Summary To ensure that you understand the material in this chapter, you should review the meanings of the bold terms in the following summary and ask yourself how they relate to the topics in the chapter. Chemistry is the study of matter, which is anything that has mass and takes up space. Chemistry is one branch of science, which is the study of the natural universe. Like all branches of science, chemistry relies on the scientific method, which is a process of Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-4577 | 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.
What are animals that live with tiny zooxanthellae that also photosynthesize? | [
"worms",
"coral",
"bacteria",
"fungi"
] | B | What's at the bottom of the food chain? A bit of the food energy comes from above, where plankton photosynthesize. Most comes from the coral. Coral are animals that live with tiny zooxanthellae that also photosynthesize. Of course, you know what's at the top of this food chain!. |
SciQ | SciQ-4578 | pathophysiology, kidney
Title: To diagnose osteomyelitis of vertebral column in chronic kidney failure Assume you suspect amyloidosis because of the history of the patient: problem with vertebral column and "purulent" (serous, fibrous, or hemorrhagic) inflammation when patient very young.
Now, the patient has a chronic renal failure.
Is there any other method to diagnose the fracture of some bone than röntgen?
Assume you do not know where the fracture is exactly. Osteomyelitis can be diagnosed with the following imaging techniques [1]:
first of all: radiography to view the anatomy of the bone
the sonography can be used to diagnose fluid collections, periosteal involvement. It is also the most useful procedure for kidney assessment [2].
CT is also useful to detect early osseous erosion, but is less sensitive when it comes to bone infection
MRI is the most sensitive and specific for osteomyelitis
Nuclear imaging can be used to identify multifocal osseous involvement.
References:
Carlos Pineda et al., Radiographic Imaging in Osteomyelitis: The Role of Plain Radiography, Computed Tomography, Ultrasonography, Magnetic Resonance Imaging, and Scintigraphy
American College of Radiology, Renal failure
The following is multiple choice question (with options) to answer.
What usually causes fractures on a bone? | [
"excessive bending stress",
"compressive stress",
"shear stress",
"extra weight"
] | A | Even though they are very strong, bones can fracture , or break. Fractures can happen at different places on a bone. They are usually caused by excess bending stress on the bone. Bending stress is what causes a pencil to break if you bend it too far. |
SciQ | SciQ-4579 | electromagnetism, magnetic-fields
Title: Can someone please explain the concept 'B' regarding magnetic fields? I can't seem to understand the concept 'B'.
I have done a great deal of research regarding magnetism and magnetic fields but I seem to have just complicated the matter further.
What I understand so far is that magnetic fields are produced by moving charges & that the magnetic field is a vector field. I understand that a compass can give us the direction of a magnetic field at any point.
Now my problem arises. I know that B is called the magnetic field and, from the Lorentz force law, B is the force applied to a moving unit charge in the unit Tesla. However, isn't B also regarded as the magnetic flux density (the amount of flux per unit area)? If this is so, then how can B represent both the magnetic field and the magnetic flux density? Is the magnitude of the magnetic field and magnetic flux density the same thing?
Sorry for the length of this, thanks in advance. "If this is so, then how can B represent both the magnetic field and the magnetic flux density? Is the magnitude of the magnetic field and magnetic flux density the same thing?"
Yes!
These days the Lorentz force is usually used to define what we mean by the $\vec{B}$ vector: if a charged particle with velocity $\vec{v}$ experiences a force given by$$\vec{F}=q\vec{v}\times \vec{B},$$then $\vec{B}$ is the local magnetic field strength (officially, the magnetic flux density).
We define the flux passing through an area, S, as the surface integral of $\vec{B}$ across that area. Thus $$\Phi=\int_{S}\vec{B}\cdot \mathrm d\vec{S}.$$
The following is multiple choice question (with options) to answer.
What is the magnetic field traditionally referred to as? | [
"m-field",
"charged field",
"bfield",
"spicule"
] | C | 22.3 Magnetic Fields and Magnetic Field Lines Einstein is said to have been fascinated by a compass as a child, perhaps musing on how the needle felt a force without direct physical contact. His ability to think deeply and clearly about action at a distance, particularly for gravitational, electric, and magnetic forces, later enabled him to create his revolutionary theory of relativity. Since magnetic forces act at a distance, we define a magnetic field to represent magnetic forces. The pictorial representation of magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. As shown in Figure 22.15, the direction of magnetic field lines is defined to be the direction in which the north end of a compass needle points. The magnetic field is traditionally called the Bfield. |
SciQ | SciQ-4580 | ecology
Title: Do invasive species cause long-term damage to ecosystems they invade? Growing up in the U.S., I was warned at various times of the dire consequences of a variety of introduced pests (usually insects).
Japanese beetles, gypsy moths, and most recently the brown marmorated stink bug are all introduced pests that, at various times, were described as serious threats to our ecology.
These threats aren't confined to arthropods, either. The giant African land snail is causing a stir in Florida (indeed, Florida seems to suffer from an excessive variety of introduced species.
"Lack of native predators" is frequently cited as the primary reason many invasive species are considered such a risk to the ecology.
I understand that these introduced species can place tremendous pressure on native species that fill similar ecological niches, and may even push these species out of the region due to competition for food and habitat. However, do the overall ecologies that these species are introduced to adjust over long periods of time?
The numbers of Japanese beetles and gypsy moths don't seem anywhere as high as when I was a child. Has the ecosystem adjusted, or has the overpopulation self-corrected as the species ran low on food through over-consumption? Or are the populations still just as problematic now as they were 30 years ago, and I just am not seeing the bigger picture?
What is the long-term impact that we've seen from invasive, introduced species? Is there a significant difference on the long-term impact between introduced flora, arthropods, or mammals? The answer really depends on how you think of invasive. One extreme answer is to say that all things are relative, and that the concepts of local and invasive are all relative. This matters to a certain extent because ecologists draw a fuzzy line between invasive and naturalized. You could start with some basic species that we all think of as either good, local, or neutral. Take the earthworm. Most people think of it as a common native species, but the earthworm is actually an invasive species that has radically changed much of North America that came over with the Europeans. Similarly, brown trout are also invasive, coming to the US in the 1800's.
The following is multiple choice question (with options) to answer.
What can ultimately result when species are introduced to a new place and prey on other species? | [
"over population",
"elimination",
"extinction",
"depletion"
] | C | Humans have caused many extinctions by introducing species to new places. For example, many of New Zealand’s birds have adapted to nesting on the ground. This was possible because there were no land mammals in New Zealand. Then Europeans arrived and brought cats, foxes, and other predators with them. Several of New Zealand’s ground nesting birds, such as this flightless kiwi, are now extinct or threatened because of these predators. |
SciQ | SciQ-4581 | 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.
In humans, what is the first organ to form and become functional? | [
"heart",
"brain",
"liver",
"pancreas"
] | A | 19.5 Development of the Heart The heart is the first organ to form and become functional, emphasizing the importance of transport of material to and from the developing infant. It originates about day 18 or 19 from the mesoderm and begins beating and pumping blood about day 21 or 22. It forms from the cardiogenic region near the head and is visible as a prominent heart bulge on the surface of the embryo. Originally, it consists of a pair of strands called cardiogenic cords that quickly form a hollow lumen and are referred to as endocardial tubes. These then fuse into a single heart tube and differentiate into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus, starting about day 22. The primitive heart begins to form an S shape within the pericardium between days 23 and 28. The internal septa begin to form about day 28, separating the heart into the atria and ventricles, although the foramen ovale persists until shortly after birth. Between weeks five and eight, the atrioventricular valves form. The semilunar valves form between weeks five and nine. |
SciQ | SciQ-4582 | meteorology, tornado
into
... because F6 or stronger tornadoes are not expected to occur on the
earth, they will be called Inconceivable tornadoes should they ever
occur. [1981 paper]
Very importantly, the Fujita scales are damage scales, simply because it's very difficult to directly measure the speeds of a tornado. As such we base tornado ratings by analyzing the degree which it damaged objects; SPC's Fujita scale page lists the 28 damage indicators currently available as of 2017. The highest wind speed matched with any of them, found when significant structural deformation is done to a high-rise building (over 20 stories tall), would only indicate an upper bound of 290 mph.
That does not indicate that wind speeds aren't higher than that, only that we have no structures that can withstand any higher wind speeds. Thus there would not be any potential for an F6 rating unless building methods are substantially changed to withstand stronger speeds, those buildings became prevalent enough that engineering testing were done and were able to verify its strength, and then such an extreme tornado ever hit them. Not something we're going to see anytime soon it appears.
So back to the question of whether tornadoes have winds stronger than those listed for an (E)F5? Measurement of the wind speed appears our only real hope of noting such. In-situ instruments such as anemometers generally fail well before winds reach such speeds, and typical radars cannot offer the resolution to diagnose such speeds. Only mobile Doppler radars offer much hope. There are numerous issues with utilizing such measurements, such as the fact they scan significantly above the ground layer, their sampling areas\timescales that make analyzing suction vortices difficult, and they contain uncertainties due to Nyquist frequencies, variations in reflective objects, and statistical distributions.
Such tornadoes are very rare to encounter. But in the past couple decades we have indeed managed to attain a handful of close-proximity estimated measurements of strong tornadoes. But I am not aware of any peak estimated wind speed reaching beyond the (E)F5 range. Here are the most notable ones I'm aware of:
The following is multiple choice question (with options) to answer.
What is used to classify tornadoes? | [
"damage, snowfall",
"wind speed, damage",
"seismograph",
"humidity, rain"
] | B | The winds of a tornado can reach very high speeds. The faster the winds blow, the greater the damage they cause. Wind speed and damage are used to classify tornadoes. Table below shows how. |
SciQ | SciQ-4583 | electricity, electric-circuits, electrical-resistance, instrument
Title: Why do we prefer using materials of high resistivity in laboratory instruments? I know that :$$R=\rho\frac{l}{A}$$ where $R$ is the resistance of the wire, $\rho$ is its specific resistance (resistivity), $l$ is its length, and $A$ is the area of cross-section of the wire.
Why do we prefer using materials of high resistivity (like manganin, constantan etc.) in laboratory instruments like potentiometer or Metre Bridge?
I searched everywhere online, but all I always get is the definition of resistivity, which I already know. Manganin, like constantin, are alloys invented in the late 1800s to solve a specific problem: resistance varies with temperature, and every resistor passing a current is subject to Joule heating. So if you are building precise electrical metering equipment their is a design advantage to using materials that show a stable resistance with temperature variations.
The follow-on to your question could be: how are precision resistors made? One way is to simply cut strips of high resistance metals to measure; modern surface mount devices use a ceramic core with a metal coating that is laser-trimmed. Carbon film resistors are similar in design, but typically less precise. Or you can grind up the resistance metal and mix it with clay - this gives a resistor that can dissipate heat, and is suitable for high voltage/current applications.
These and more are described here: http://www.learnabout-electronics.org/Resistors/resistors_08.php
The following is multiple choice question (with options) to answer.
What do you call materials that have high resistance to electric current? | [
"semiconductors",
"electric insulators",
"destructive insulators",
"conductors"
] | B | Materials that have high resistance to electric current are called electric insulators . Examples include most nonmetallic solids, such as wood, rubber, and plastic. Their atoms hold onto their electrons tightly, so electric current cannot flow freely through them. Dry air is also an electric insulator. You can learn more about electric insulators—as well as how to test whether a material is an insulator—by doing the activity at this URL:. |
SciQ | SciQ-4584 | fusion, renewable-energy
An energy "breakthrough" would be a loaded development. We already use lots of energy, and if we found it economic to use more we probably would. The last breakthrough shift in our ability to exploit energy resources rocketed the entire planet into a new geological era, the Anthropocene. We called this change the industrial revolution. Some obscure project that ARPA-E funded with $500,000 could cause the next industrial revolution. The implications of such a change would probably be beyond any of our imaginations.
The following is multiple choice question (with options) to answer.
What term is used to describe the development of new technology? | [
"Smart Design",
"variation design",
"technological design",
"evident design"
] | C | The development of new technology is called technological design . It is similar to scientific investigation. Both processes use evidence and logic to solve problems. |
SciQ | SciQ-4585 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
Cell walls, plastids, and a large central vacuole distinguish plant cells from what? | [
"parenchyma cells",
"animal cells",
"eukaryotic cells",
"phloem cells"
] | B | 30.1 | The Plant Body By the end of this section, you will be able to: • Describe the shoot organ system and the root organ system • Distinguish between meristematic tissue and permanent tissue • Identify and describe the three regions where plant growth occurs • Summarize the roles of dermal tissue, vascular tissue, and ground tissue • Compare simple plant tissue with complex plant tissue Like animals, plants contain cells with organelles in which specific metabolic activities take place. Unlike animals, however, plants use energy from sunlight to form sugars during photosynthesis. In addition, plant cells have cell walls, plastids, and a large central vacuole: structures that are not found in animal cells. Each of these cellular structures plays a specific role in plant structure and function. |
SciQ | SciQ-4586 | marine-biology, molluscs
Title: Age of shells on beach As a child I watched tiny fiddler crabs living in conical shells, and many years later I find that people study fossil turritellids. So now I wonder: how old are shells, typically, that you see on beaches? Do they wear out after a year of sand abrasion? 100 years, a million? Is it known? Mollusk shells found on typical east coast (US) beaches can range from days old (the animal that made the shell died recently) to thousands of years old. Some shells in our state, North Carolina, have been dated as 40,000 years old. A high number of "seashells" found on east coast beaches are from mollusks that lived in the marsh on the back side of the island. The presence of these shells on ocean beaches provides evidence of island migration - the island has moved landward over the marsh until what was once the marsh is now the ocean shore. Once buried in the sand, the shell is well preserved until erosion uncovers it. Occasionally, fossilized shells are washed up on beaches after having been dislodged from offshore limestone deposits - these shells can be millions of years old.
-Richard -
Carolina Ocean Studies
The following is multiple choice question (with options) to answer.
Snails, scallops, and squids are what type of invertebrate? | [
"algae",
"crustacean",
"arthropod",
"mollusk"
] | D | Mollusks are invertebrates such as snails, scallops, and squids. They have a hard outer shell. There is a layer of tissue called the mantle between the shell and the body. Most mollusks have tentacles for feeding and sensing, and many have a muscular foot. Mollusks also have a coelom, a complete digestive system, and specialized organs for excretion. The majority of mollusks live in the ocean. Different classes of mollusks have different ways of obtaining food. |
SciQ | SciQ-4587 | speciation, artificial-selection
Title: Is there any artificial species (in particular, an artificial species of animal)? Dogs were artificially selected from wolves, but a dog and a wolf can produce fertile offspring, and thus are of the same species. I had heard that the aurochs and cattle were different species, but I could not find this information anywhere. I had heard also that some artificially selected flies are considered to be a new species.
Is there any human-made species (especially a species of animal) which is not able to produce fertile offspring witch any other species, in particular with the one from which it evolved?
EDIT: (A similar question in different words.) Is there any human-made animal lineage which was conceived by artificial selection and which is broadly accepted as not being a race or subspecies, but a species on its own. Artificial selection leading to new species - Domestication
As you talk about dogs in your intro, let's consider them.
You will fail to breed a great dane and chihuahua for obvious mechanical reasons. You will also fail to breed a chihuahua with a wolf. So, yes artificial selection have lead to reproductive isolation.
Artificial selection leading to new species - lab experiment
Artificial selection have also lead to reproductive isolation in non-domesticated species. See for example the post Have we ever observed two drosophila lineages that evolved reproductive isolation in labs?
Concept of species
As a side note... Above, I consider the so-called 'biological species concept'. For a discussion on the definition of species, please have a look at this post.
The following is multiple choice question (with options) to answer.
Humans create different breeds of organisms using what kind of selection? | [
"biased selection",
"speciation",
"artificial selection",
"natural selection"
] | C | Artificial Selection: Humans used artificial selection to create these different breeds. Both dog breeds are descended from the same wolves, and their genes are almost identical. |
SciQ | SciQ-4588 | evolution, genetics, ecology, population-genetics, database
Then there is the problem of metadata. I might be able to find sequencing data from the gut microbiome of a human treated with antibiotics quite easily. If I am looking for a specific antibiotic given over a minimal time of seven days to a different healthy humans, preferably including at least one breastfed child and it's mother (which was the one taking the antibiotics, not the child), then it's getting complicated. Here it is generally way easier to scan PubMed for some relevant publications on the matter and find out if they used published datasets or published their own.
The following is multiple choice question (with options) to answer.
The word antibiotic comes from the greek anti, meaning “against,” and bios, meaning this? | [
"virus",
"bacteria",
"life",
"germ"
] | C | The Antibiotic Crisis The word antibiotic comes from the Greek anti, meaning “against,” and bios, meaning “life. ” An antibiotic is an organismproduced chemical that is hostile to the growth of other organisms. Today’s news and media often address concerns about an antibiotic crisis. Are antibiotics that were used to treat bacterial infections easily treatable in the past becoming obsolete? Are there new “superbugs”—bacteria that have evolved to become more resistant to our arsenal of antibiotics? Is this the beginning of the end of antibiotics? All of these questions challenge the healthcare community. One of the main reasons for resistant bacteria is the overuse and incorrect use of antibiotics, such as not completing a full course of prescribed antibiotics. The incorrect use of an antibiotic results in the natural selection of resistant forms of bacteria. The antibiotic kills most of the infecting bacteria, and therefore only the resistant forms remain. These resistant forms reproduce, resulting in an increase in the proportion of resistant forms over non-resistant ones. Another problem is the excessive use of antibiotics in livestock. The routine use of antibiotics in animal feed promotes bacterial resistance as well. In the United States, 70 percent of the antibiotics produced are fed to animals. The antibiotics are not used to prevent disease, but to enhance production of their products. |
SciQ | SciQ-4589 | geology, earth-history, paleontology, stratigraphy, mass-extinction
Why did this idea develop only in the 1980s? It was known since the 19th century that extinctions had occurred. Even the stratigraphic time is divided into units constrained by different fauna found in the fossil records. What was it that made the change from a "gradualist" perspective of things to the "catastrophic" point of view? The idea of mass extinction is not that recent actually: Cuvier (1798), Buckland (1823) and d'Orbigny (1851) for instance were already talking about global catastrophes in earth history, linked to extinctions. But during the same period, Brocchi (1814) and Lyell (1832) proposed that extinctions of species occurred individually and were a gradual process (either only linked to an intrinsic taxa longevity for Brocchi, or variations in the environment for Lyell). Darwin, following Lyell, also thought that extinctions were gradual and not catastrophic. He also noted the fact that hiatuses in the fossil record or artificial concentration in some strata could show apparent extinction event.
The issue with mass extinction is that to demonstrate their existence you need to be able to demonstrate extinction synchronicity and quantify the amount of species going extinct (to show that it is more than just background noise).
Demonstrating the synchronicity of one mass extinction is what Alvarez et al. 1980 managed to do thanks to the Iridium layer at the K/Pg boundary. More generally, the possibility of correlating extinctions precisely is something that evolved in par with the evolution of stratigraphic tools, and the 1970-1980s is the period during which high-resolution stratigraphic methods arose (chronostratigraphy, magnetostratigraphy, stable isotope stratigraphy for instance).
Quantifying mass extinction is what Jack Sepkoski did with his compendium of marine invertebrates (see Sepkoski 1978, 1979; Raup & Sepkoski 1982, etc.). Today, the PbDb (PaleoBiology DataBase) is the project which focusses on that specific issue (see for instance Alroy et al. 2001). It still remains today the main hurdle in studying mass extinctions.
Alroy, J. et al., 2001. Effects of sampling standardization on estimates of Phanerozoic marine diversification. PNAS, 98(11): 6261-6266.
The following is multiple choice question (with options) to answer.
What are sudden and dramatic losses of biodiversity called? | [
"mass extinction",
"life extinction",
"explosive extinction",
"normal extinction"
] | A | Figure 21.13 Extinction intensity as reflected in the fossil record has fluctuated throughout Earth’s history. Sudden and dramatic losses of biodiversity, called mass extinctions, have occurred five times. |
SciQ | SciQ-4590 | ions, crystal-structure, ionic-compounds, solid-state-chemistry
Title: How does NaCl maintain its crystalline structure? My understanding is that $\mathrm{NaCl}$ is an ionic compound, in which $\mathrm{Cl}$ becomes (effectively) $\mathrm{Cl^-}$ and $\mathrm{Na}$ becomes $\mathrm{Na^+}$. So I understand why I would get a "sea" of particles that would stick together.
But why does the above mean that it will have a face centered cubic structure with the ions held in place so rigidly? Crystals have inspired a great many chemists because they are fascinating for a good reason. Not only are they aesthetically pleasing, but they serve as an excellent subject to tour a variety of theoretical subjects important for understanding high-level chemistry.
Crystalline materials are made up of periodic structures. We’re only going to primarily focus on binary compounds where there is not a high degree of covalency. There are several ways to think about this problem, but let’s start with the melting of a crystal.
We say that at some definite temperature a highly ordered crystal will melt into a liquid. Those of us familiar with the language of equilibrium thermodynamics might recognize that the change in free energy for this phase change can be written, at constant temperature, as,
$$ G_\text{liquid} - G_\text{crystal} = H_\text{liquid} - H_\text{crystal} - T ( S_\text{liquid} - S_\text{crystal} ) $$
$$ \Delta G = \Delta H - T \Delta S $$
If we suppose that this process is spontaneous then we would say that the change in Gibbs’ free energy is negative, i.e. $\Delta G < 0$. This is true if and only if,
$$\Delta H < T \Delta S$$
The following is multiple choice question (with options) to answer.
The ions in ionic compounds are arranged in rigid three-dimensional patterns called what? | [
"crystal lattices",
"pattern lattices",
"lattice groups",
"core lattices"
] | A | The ions in ionic compounds are arranged in rigid three-dimensional patterns called crystal lattices. The crystal lattice that is formed is a characteristic property of a given compound. |
SciQ | SciQ-4591 | homework-and-exercises, kinematics, time, distance, displacement
Distance is a little different, but it is easy to understand. You can think of it as what the odometer in your car gives to you. It just tells you how far you have traveled without reference to some starting point. Going back to the example of going around a circle one time, your displacement was $0$, but the distance you traveled is equal to the circumference of the circle. Distance is a scalar value. You can determine it by integrating the speed over time:
$$D(t)=\int_0^t|\mathbf v(\tau)|\text d\tau$$
Note that this integral is the same thing as the curve length of the path the particle moves along (i.e. the distance you have traveled).
These explanations should help you in your own problem.
The following is multiple choice question (with options) to answer.
Where was the distinction between total distance traveled and displacement first noted? | [
"one-dimensional kinematics",
"string theory",
"Newton's first law",
"uncertainty principle"
] | A | Discussion Quite a trip (if it survives)! Note that this distance is the total distance traveled by the fly. Displacement is actually zero for complete revolutions because they bring the fly back to its original position. The distinction between total distance traveled and displacement was first noted in One-Dimensional Kinematics. |
SciQ | SciQ-4592 | cell-biology
Title: Structure of Cell Are cells spheres or ovals/circles bound by phospholipidbilayer?
If they are spherical how are we able to see the nucleus through the phospholipid bilayer under a microscope? Not exactly. That is a stereotype of cells. Muscle cells are not round nor oval, but rather elongated rods. If you were to look up epithelia cells, you can quickly see that cells are grouped based on their physical characteristics; simple (round/oval & single layer), columnar, and cuboidal to name a few. Cells come in many shapes and sizes. As Hans stated, stains are vital in viewing cellular components. There is a diverse amount of stains used - which all carry a purpose and benefit in a specific application.
The following is multiple choice question (with options) to answer.
What science is the study of the shape and arrangement of cells in tissue? | [
"cellology",
"histology",
"genetics",
"methodology"
] | B | CHAPTER REVIEW 4.1 Types of Tissues The human body contains more than 200 types of cells that can all be classified into four types of tissues: epithelial, connective, muscle, and nervous. Epithelial tissues act as coverings controlling the movement of materials across the surface. Connective tissue integrates the various parts of the body and provides support and protection to organs. Muscle tissue allows the body to move. Nervous tissues propagate information. The study of the shape and arrangement of cells in tissue is called histology. All cells and tissues in the body derive from three germ layers in the embryo: the ectoderm, mesoderm, and endoderm. Different types of tissues form membranes that enclose organs, provide a friction-free interaction between organs, and keep organs together. Synovial membranes are connective tissue membranes that protect and line the joints. Epithelial membranes are formed from epithelial tissue attached to a layer of connective tissue. There are three types of epithelial membranes: mucous, which contain glands; serous, which secrete fluid; and cutaneous which makes up the skin. |
SciQ | SciQ-4593 | genetics, cell-biology, embryology, meiosis, gamete
Title: Fertilization of the human egg- where does our centrosome come from? Is there a centrosome in a human egg cell? Is the reason why the egg cell remains paused before meiosis 2 because there isn't a centrosome, and it only divides when the sperm fertilizes it thus it can have a centrosome? If this is so, then how did oogenesis happen? ? To answer the first part of your question. The sperm actually introduces two centrosomes. The centrosome then nucleates the new microtubule assembly to form the sperm aster — a step essential for successful fertilization. You can visit these sites Simerly, et al as well as Paweltz, et al
The following is multiple choice question (with options) to answer.
What forms when a sperm fertilizes and egg? | [
"cytoplasm",
"crystals",
"proton",
"zygote"
] | D | |
SciQ | SciQ-4594 | organic-chemistry, inorganic-chemistry, physical-chemistry
Title: What are the main axis of research in Chemistry? I would like to know what are the main problems currently studied in Chemistry.
For some reason, it seems that there is far less vulgarisation in chemistry than the other fields, and it's hard to find an overview of the field accessible to a layman (compared to math or physics for instance).
I only found this wikipedia page, but I have no idea how relevant it is. Even though I voted to close this question as not constructive, these are among the most important unsolved problems in chemistry:
The following is multiple choice question (with options) to answer.
The field of organic chemistry studies the structure and reactivity of compounds containing what element? | [
"carbon",
"oxygen",
"hydrogen",
"nitrogen"
] | A | Since then, the distinction between organic and inorganic compounds and reactions has blurred. Currently, the field of organic chemistry studies the structure and reactivity of nearly all carbon-containing compounds. Over twenty million organic compounds are known, ranging from very simple molecules to complex proteins. |
SciQ | SciQ-4595 | 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.
Where does growth in length occur, above the root cap? | [
"primary meristem",
"vascular cambrium",
"primary tuber",
"apical meristem"
] | A | As shown in Figure below , the tip of a root is called the root cap . It consists of specialized cells that help regulate primary growth of the root at the tip. Above the root cap is primary meristem, where growth in length occurs. |
SciQ | SciQ-4596 | mycology
Title: How do fairy rings propagate? It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores? When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas the newly formed mycelium (underground) will develop the familiar mushrooms above ground and this will result in a fairy ring.
The following is multiple choice question (with options) to answer.
Asci are used by mycelia for what kind of reproduction? | [
"cloning",
"sexual",
"mitosis",
"asexual reproduction"
] | B | hyphae divided by perforated septa, allowing streaming of cytoplasm from one cell to the other. Conidia and asci, which are used respectively for asexual and sexual reproductions, are usually separated from the vegetative hyphae by blocked (non-perforated) septa. Asexual reproduction is frequent and involves the production of conidiophores that release haploid conidiospores (Figure 24.13). Sexual reproduction starts with the development of special hyphae from either one of two types of mating strains (Figure 24.13). The “male” strain produces an antheridium and the “female” strain develops an ascogonium. At fertilization, the antheridium and the ascogonium combine in plasmogamy without nuclear fusion. Special ascogenous hyphae arise, in which pairs of nuclei migrate: one from the “male” strain and one from the “female” strain. In each ascus, two or more haploid ascospores fuse their nuclei in karyogamy. During sexual reproduction, thousands of asci fill a fruiting body called the ascocarp. The diploid nucleus gives rise to haploid nuclei by meiosis. The ascospores are then released, germinate, and form hyphae that are disseminated in the environment and start new mycelia (Figure 24.14). |
SciQ | SciQ-4597 | nutrition, hematology, metabolism
Title: How does a glucose molecule enter the cell from blood vessel? The transporters in the plasma membrane of the cells promote the entry of glucose molecules from the extracellular matrix to the cytosol of the cell. Could someone explain how does the nutrient molecule enter the extracellular space from the blood vessel?
For instance, in the context of the pancreas, the walls of the blood vessel is fenestrated. The literature also provides evidence for the presence of connexon in the endothelium of the capillaries.
My doubt is, the nutrient molecule that diffuses from the blood vessel reaches the cytosol of the cell through
Diffusing through connexon ?(or)
Does it reach the interstitial matrix(the fluid surrounding the cells) and then uptaken by the transporters present in the plasma membrane of the cell? I think I understand your question, Natasha. In short, your own answer #2 is correct.
There are 3 spaces, and 2 pathways for glucose to pass from one to the next:
intracapillary plasma
extracellular fluid
the cytosol.
Ways glucose gets into the cell:
(2->3) To get from the ECF to the cytosol , glucose always needs a transport protein. These are the GLUTs. In two cases, the small intestine and kidney, these are part of a secondary active transport system based on the Na/K-ATPase. In the pancreas, it's GLUT2.
(1->2) To get from the capillary plasma to the ECF requires filtration, the process of applying hydrostatic pressure to the plasma and literally squeezing it like a sponge. The boundary of the "blood sponge" is the basement membrane. The membrane holds in the proteins, and lets anything dissolved in the watery serum (like glucose) through.
The Filtration Constant Kf is proportional to the percentage of the BM that is exposed in a given capillary, which varies by the type and other factors like histamine release.
The following is multiple choice question (with options) to answer.
What is the term used to describe the liquid that moves through the vessels and includes plasma and the cells and sell fragments called platelets? | [
"blood",
"pus",
"bacteria",
"water"
] | A | 40.2 | Components of the Blood By the end of this section, you will be able to: • List the basic components of the blood • Compare red and white blood cells • Describe blood plasma and serum Hemoglobin is responsible for distributing oxygen, and to a lesser extent, carbon dioxide, throughout the circulatory systems of humans, vertebrates, and many invertebrates. The blood is more than the proteins, though. Blood is actually a term used to describe the liquid that moves through the vessels and includes plasma (the liquid portion, which contains water, proteins, salts, lipids, and glucose) and the cells (red and white cells) and cell fragments called platelets. Blood plasma is actually the dominant component of blood and contains the water, proteins, electrolytes, lipids, and glucose. The cells are responsible for carrying the gases (red cells) and immune the response (white). The platelets are responsible for blood clotting. Interstitial fluid that surrounds cells is separate from the blood, but in hemolymph, they are combined. In humans, cellular components make up approximately 45 percent of the blood and the liquid plasma 55 percent. Blood is 20 percent of a person’s extracellular fluid and eight percent of weight. |
SciQ | SciQ-4598 | [13]:
nutrients = pd.DataFrame(
index=[
"Vitamin A",
"Vitamin B1",
"Vitamin C",
"Calcium",
"Iron",
"Phosphorus",
"Potassium",
"Total fat",
"Carbohydrates",
"Proteins",
]
)
nutrients["DRI"] = [800, 1.1, 80, 800, 14, 700, 2000, 70, 260, 50]
nutrients["Chicken Breast"] = [0, 0.1, 0, 4, 0.40, 210, 370, 0.8, 0, 23.3]
nutrients["Milk"] = [37, 0.04, 1, 119, 0.1, 93, 150, 3.6, 4.9, 3.3]
nutrients["Pasta"] = [0, 0, 0, 22, 1.4, 189, 192, 1.4, 79.1, 10.9]
nutrients["Beans"] = [3, 0.4, 3, 135, 8, 450, 1445, 2, 47.5, 23.6]
nutrients["Oranges"] = [71, 0.06, 50, 49, 0.2, 22, 200, 0.2, 7.8, 0.7]
nutrients
[13]:
DRI Chicken Breast Milk Pasta Beans Oranges
Vitamin A 800.0 0.0 37.00 0.0 3.0 71.00
Vitamin B1 1.1 0.1 0.04 0.0 0.4 0.06
Vitamin C 80.0 0.0 1.00 0.0 3.0 50.00
Calcium 800.0 4.0 119.00 22.0 135.0 49.00
Iron 14.0 0.4 0.10 1.4 8.0 0.20
Phosphorus 700.0 210.0 93.00 189.0 450.0 22.00
Potassium 2000.0 370.0 150.00 192.0 1445.0 200.00
Total fat 70.0 0.8 3.60 1.4 2.0 0.20
Carbohydrates 260.0 0.0 4.90 79.1 47.5 7.80
Proteins 50.0 23.3 3.30 10.9 23.6 0.70
The following is multiple choice question (with options) to answer.
The density of bone is, in part, related to the amount of what mineral in one’s diet? | [
"potassium",
"barium",
"calcium",
"nitrogen"
] | C | The densities of many components and products of the body have a bearing on our health. Bones. Bone density is important because bone tissue of lower-than-normal density is mechanically weaker and susceptible to breaking. The density of bone is, in part, related to the amount of calcium in one’s diet; people who have a diet deficient in calcium, which is an important component of bones, tend to have weaker bones. Dietary supplements or adding dairy products to the diet seems to help strengthen bones. As a group, women experience a decrease in bone density as they age. It has been estimated that fully half of women over age 50 suffer from excessive bone loss, a condition known as osteoporosis. Exact bone densities vary within the body, but for a healthy 30-year-old female, it is about 0.95–1.05 g/cm3. Osteoporosis is diagnosed if the bone density is below 0.6–0.7 g/cm3. Urine. The density of urine can be affected by a variety of medical conditions. Sufferers of diabetes insipidus produce an abnormally large volume of urine with a relatively low density. In another form of diabetes, called diabetes mellitus, there is excess glucose dissolved in the urine, so that the density of urine is abnormally high. The density of urine may also be abnormally high because of excess protein in the urine, which can be caused by congestive heart failure or certain renal (kidney) problems. Thus, a urine density test can provide clues to various kinds of health problems. The density of urine is commonly expressed as a specific gravity, which is a unitless quantity defined as. |
SciQ | SciQ-4599 | mole
Title: How to calculate the mass of a single atom? If we know the molar mass of a certain element and Avogadro's constant, how can we calculate the mass of a single atom? Do we need to multiply the molar mass with Avogadro's constant? For most atoms it's around Ryan's answer.
E.g. Carbon-12:
$$\frac{\ce{12 g}~\ce{C}}{\pu{1 mol}~\ce{C}} \times
\frac{\pu{1 mol}~\ce{C}}{\pu{6.022E23 atoms}} =
\pu{1.993E-23 g//atom} = \pu{1.993E-27 kg//atom}.$$
That was the molar mass $M$ multiplied by $1/N_\mathrm{A}$, where $N_\mathrm{A}$ is Avagadro's constant.
Thus $M/N_\mathrm{A}$ gives you a calculation for mass of an atom for the specific element.
The following is multiple choice question (with options) to answer.
What is the sum of the masses of the atoms in a molecule? | [
"atomic energy",
"compound mass",
"mass effect",
"molecular mass"
] | D | Note: Atomic mass is given to three decimal places, if known. Now that we understand that atoms have mass, it is easy to extend the concept to the mass of molecules. The molecular mass is the sum of the masses of the atoms in a molecule. This may seem like a trivial extension of the concept, but it is important to count the number of each type of atom in the molecular formula. Also, although each atom in a molecule is a particular isotope, we use the weighted average, or atomic mass, for each atom in the molecule. For example, if we were to determine the molecular mass of dinitrogen trioxide, N2O3, we would need to add the atomic mass of nitrogen two times with the atomic mass of oxygen three times:. |
SciQ | SciQ-4600 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
Chloroplasts, leucoplasts and chromoplasts are found in what type of cells? | [
"animal cells",
"nitrogen cells",
"plant cells",
"man-made cells"
] | C | A third difference between plant and animal cells is that plants have several kinds of organelles called plastids . And there are several different kinds of plastids in plant cells. For example, Chloroplasts are needed for photosynthesis, leucoplasts can store starch or oil, and brightly colored chromoplasts give some flowers and fruits their yellow, orange, or red color. It is the presence of chloroplasts and the ability to photosynthesize, that is one of the defining features of a plant. No animal or fungi can photosynthesize, and only some protists are able to. The photosynthetic protists are the plant-like protists, represented mainly by the unicellular algae. |
SciQ | SciQ-4601 | geology, oceanography, geochemistry, mineralogy
Title: Will the sea get saltier forever? The sea wasn't always salty. It's been getting saltier over millions of years as minerals dissolve.
Is there a natural limit to this process, or the will the sea keep getting saltier forever?
Is there a natural process which removes salt from the sea at a significant rate?
How long would it take for the sea to get too salty to support life as we know it? No there are natural processes that remove salt as well.
as sea level changes water gets trapped in basins and evaporates leaving the salt behind, this is where many of the salt formation on earth came from. whenever sea levels fall the salinity of the ocean drops. Tectonically isolated basin can remove salt in the same way. The process can even happen repeatedly in the same basin as sea level changes.
There are biological processes that remove it as well the formation of shells and limestone remove some of the ocean salts.
Can it increase yes, but it can also decrease, over earths history there have been saltier and less salty periods.
The following is multiple choice question (with options) to answer.
Salt in seawater causes it to have greater what, which is also affected by temperature and pressure? | [
"mass",
"density",
"volume",
"area"
] | B | Seawater has lots of salts in it. This increases its density (mass per volume) over fresh water. Temperature and pressure also affect density. |
SciQ | SciQ-4602 | antarctica, continent, history
Large areas of Antarctica is ice-free, eg. this valley in Vestfold Hills, East Antarctica. The area was first explored in the mid to late 1900's but sightings of outcrop would assure explorers that they actually saw the continent they were expecting and not floating ice.
Geologists could also early correlate the rare findings from Antarctica with surrounding continents and started to reconstruct the Gondwana assembly, a work that is still ongoing and due to the lack of outcrops in Antarctica is to a large extent based on geophysical data. Still, geologists and geophysicists are looking for similarities in Africa, India and Australia to understand the nature of the Antarctic geology under the ice cover.
With aviation, it was finally possible to map the hinterland of the continent, and great discoveries were made as late as 1946–47 during Operation Highjump and during the Soviet's expeditions in the 50's.
(Don't miss this short footage of the discovery of Bunger Hills:
Youtube)
As far as I know, it was not until the International Geophysical Year (IPY) 1957-58 an international effort deploy scientists and collect data firmly defined the physical shape of the continent, that we are still refining today. International collaboration appears to be the key to successful research in Antarctica.
Seismic data is indeed very important to understand the Antarctic lithosphere, but the resolution is low due to the low seismicity and especially the limited number of deployed seismometers. This is, however, improving during recent years and a number of new studies are using seismic tomography and receiver functions to measure the continental shape of Antarctica. See e.g. An et al (2015a) and An et al (2015b). Seismic data is also used to understand the ice sheets and to derive the heat flux that causes basal melting.
Also very important is satellite potential field data. Gravity data e.g. GOCE from ESA is and important constraints, but the resolution is low.
Magnetic data especially from airplanes but also satellites as the flight lines are still sparse is used to map and understand geological terranes covered by ice. The ICECAP project is collecting high-resolution data from flights to improve our understanding of the ice sheets, glaciers and also the bedrock under.
The following is multiple choice question (with options) to answer.
What is the name of a long and low hill of sediments which have been deposited by a glacier? | [
"a crag",
"a mountain",
"a floodplain",
"a drumlin"
] | D | A drumlin is a long, low hill of sediments deposited by a glacier. Drumlins often occur in groups called drumlin fields. The narrow end of each drumlin points in the direction the glacier was moving when it dropped the sediments. |
SciQ | SciQ-4603 | thermodynamics
If too low, reaction is limited kinetically, only small fraction would react, in spite of the equilibrium position.
If too high, reactants react fast, but just small fraction due low equilibrium constant value. And there is higher energy cost.
From evaluation of the reaction kinetics and thermodynamics, technological and cost aspects, the optimal pressure and temperature is determined.
The following is multiple choice question (with options) to answer.
The temperature of the products is typically lower than the temperature of the reactants in what type of reaction? | [
"autotrophic",
"exothermic",
"endothermic",
"parabolic"
] | C | In endothermic reactions, the temperature of the products is typically lower than the temperature of the reactants. The drop in temperature may be great enough to cause liquids to freeze. That’s what happens in the endothermic reaction at this URL: http://www. bbc. co. uk/schools/gcsebitesize/science/add_aqa_pre_2011/chemreac/energychangesrev1. shtml . |
SciQ | SciQ-4604 | human-biology, cancer
Title: Why do most breast cancers occur in women? According to Korde et al. (2010):
Male breast cancer accounts for less than 1% of all cancers in men and less than 1% of breast cancers.
This raises the question: Why do most breast cancers occur in women?
Two plausible explanations I can think of:
A male is less likely to get breast cancer for anatomical reasons (such as a smaller quantity of breast tissue, or breast tissue that is less susceptible to cancer),
Women have higher significantly levels of estrogen, which is linked to mutations that cause breast cancer (see Cavalieria et al. (2006)).
Although, I have no evidence to suggest that either of these is predominant factor. Yes, this is mostly about estrogen. Most breast cancers rely on endogenous estrogen to sustain proliferation.
Some general reading: Cancer Medicine, Chapter 18
More in-depth reading: Endogenous Hormones as a Major Factor in Human Cancer
Requested summary of mentioned readings:
First of all, there is an established link between breast cancer cell proliferation and concentration of estrogens and progesterone, which is logical, because normal breast cells divide in response to those hormones (e.g. puberty, pregnancy, even luteal phase of the menstrual cycle). Secondly, the incidence of breast cancer in women correlates with major changes in their hormonal profile - girls and elderly women (i.e. women with lower levels of sex hormones) don't get breast cancer.
Many factors, that influence the risk of developing breast cancer are in fact tightly connected to the hormones' levels. For example - early age of menarche (or, more importantly, first ovulation, because physical activity at young age disturbs ovulation AND is protective against breast cancer) and Hormone Replacement Therapy raise the risk, early age of first full-term pregnancy or any form of artificial menopause (such as preventive oophorectomy for women with mutations in BRCA1 or 2) reduce the risk.
The first table from the book chapter lists known risk and preventive factors. The review article explains the same ideas, but connects them to other types of cancer (e.g. ovarian cancer) and suggests mechanisms, which might be the cause of those risk changes.
The following is multiple choice question (with options) to answer.
What is the most common type of cancer in adult females? | [
"skin",
"bone",
"breast",
"lung"
] | C | The most common type of cancer in adult females is cancer of the breast. About one third of all cancers in women are breast cancers. |
SciQ | SciQ-4605 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
Green plants known as producers provide basic food supply for what besides themselves? | [
"water",
"air",
"animals",
"minerals"
] | C | |
SciQ | SciQ-4606 | cell-biology, molecular-biology
Title: Intracellular lipid transport I know that lipids are carried around the body in the blood either as micelles or by lipid-binding proteins which allow them to be solved.
Lipids can't always be integrated in a membrane though, the phospholipids used in membranes have to be synthesised somewhere from a precursor which will also by hydrophobic.
Consequently, at some point there will have to be transport of lipids within the cell where the lipids will need to be in solution. How is this facilitated? Like in the blood, intracellular lipid trafficking is facilitated by vesicular transport and lipid carriers like fatty acid binding proteins. In addition, intracellular membranes are densely packed and they can exchange lipids by collision and transient hemifusion. If you have access to Cell, a good review is from Prinz W. 2010 Lipid Trafficking sans vesicles, Where, Why, How?
The following is multiple choice question (with options) to answer.
The lipids that are connected to the glucose pathways are cholesterol and triglycerides. cholesterol is a lipid that contributes to cell membrane flexibility and is a precursor of this? | [
"Somatostatin",
"steroid hormones",
"ammonia hormones",
"Thrombopoietin"
] | B | Connections of Lipid and Glucose Metabolisms The lipids that are connected to the glucose pathways are cholesterol and triglycerides. Cholesterol is a lipid that contributes to cell membrane flexibility and is a precursor of steroid hormones. The synthesis of cholesterol starts with acetyl groups and proceeds in only one direction. The process cannot be reversed. Triglycerides are a form of long-term energy storage in animals. Triglycerides are made of glycerol and three fatty acids. Animals can make most of the fatty acids they need. Triglycerides can be both made and broken down through parts of the glucose catabolism pathways. Glycerol can be phosphorylated to glycerol-3-phosphate, which continues through glycolysis. Fatty acids are catabolized in a process called beta-oxidation that takes place in the matrix of the mitochondria and converts their fatty acid chains into two carbon units of acetyl groups. The acetyl groups are picked up by CoA to form acetyl CoA that proceeds into the citric acid cycle. |
SciQ | SciQ-4607 | electrochemistry, oxidation-state
Title: Determine if the following change is an oxidation, a reduction, or neither
The following reaction is not a complete reaction. Determine if the change is an oxidation, a reduction, or neither:
$$\ce{CrO4^{-2} -> Cr2O7^{-2}}$$
I know that the answer to this problem is neither, but I don't have any idea as to how that answer is reached. Could anyone give me a hint? I am familiar with oxidation, reduction, and oxidation numbers. Find the oxidation numbers of the substances in each compound.
You should find the oxidation number of Cr in each compound to be +6, and the oxidation number of O to be -2. Since there is no change in the oxidation numbers, this reaction is neither an oxidation or reduction.
The following is multiple choice question (with options) to answer.
What chemical reaction is the opposite of oxidation? | [
"reduction",
"mutation",
"evaporation",
"condensation"
] | A | The chemical reaction that is the opposite of oxidation is called reduction. Following from the notion that oxidation was originally thought to mean only the addition of oxygen, reduction was thought to be only the removal of oxygen from a substance. Many naturally occurring metal ores are present as oxides. The pure metals can be extracted by reduction. Iron is obtained from iron(III) oxide by reacting with carbon at high temperatures. |
SciQ | SciQ-4608 | protein-structure
Title: What is a "monomeric polypeptide"? In the sentence: "Bacteriophage (viral) polymerases are typically monomeric polypeptides".
I know that polypeptides are chains of amino acids monomers. But what is a "monomeric polypeptide" and what other kinds of polypeptides are there? Monomer in this context means the protein has only one polypeptide chain. In some proteins, after the individual chains have folded into their 3D or tertiary structure, they associate (generally non-covalently) into a higher order or quaternary structure. A protein with a quaternary structure containing two copies of the same chain would be called a homo-dimer. One with one copy of each of two different chains is a hetero-dimer.
Haemoglobin is a well-known example of a protein with quaternary structure — it has two copies of the alpha- and two of the beta- chain. Further elementary treatment can be found in Berg et al. and explanation of the nomenclature in this Wikipedia page.
Monomeric polypeptide is somewhat misleading in the sentence quoted. Monomeric protein would have probably been better as you wouldn't be likely to say ‘dimeric polypeptide’, given that polypeptide implies a single chain.
The following is multiple choice question (with options) to answer.
What structure is a larger assembly of several polypeptide chains that are now referred to as subunits of the protein? | [
"quaternary structure",
"digital structure",
"pyramid structure",
"geological structure"
] | A | Quaternary structure is a larger assembly of several polypeptide chains, now referred to as subunits of the protein. The quaternary structure is stabilized by the same interactions as the tertiary structure. Complexes of two or more polypeptides are called multimers. Specifically, a dimer contains two subunits, a trimer contains three subunits, and a tetramer contains four subunits. |
SciQ | SciQ-4609 | # Ratio of areas determined by a square inscribed in the corner of a right triangle
I’m having trouble working out how to algebraically get to the answer of this question. (See original image below.)
A square is drawn in the corner of a right-angled triangle with side lengths $a$, $b$, and [hypotenuse] $c$, as shown.
Which expression gives the ratio of the unshaded area [inside the triangle, but outside the square] to the shaded area [of the square] in all cases?
• (A) $1:1$
• (B) $c:(a+b)$
• (C) $a b: c^2$
• (D) $( a + b )^2 : 2 c^2$
• (E) $c^2 : 2 a b$
Apparently the answer is $c^2 : 2 a b$ (choice E), but how?
(Please ignore the pen marks! They are incorrect assumptions a friend made on the diagram.)
• Do you see any similar triangles in the figure, and can you see how to use them to determine the length of the side of the square? – Blue Aug 5 '18 at 4:01
• Hi, yeah all three triangles in the diagram are similar, but I don't know how to use them to determine the length of the side of the square. I ended up splitting a and b and calling them a1/a2 and b1/b2, but that made it confusing. – Zelda_01 Aug 5 '18 at 4:03
• Suppose the side of the square is $s$. What are the sides of the two smaller triangles? – Blue Aug 5 '18 at 4:05
• (a-s) and (b-s)? Or am I missing something easier? – Zelda_01 Aug 5 '18 at 4:06
• Good! Specifically, $a-s$ and $b-s$ are two of the legs. (I meant "legs", not "sides".) The two other legs are ... what? And what proportion links all four of these values? – Blue Aug 5 '18 at 4:08
The following is multiple choice question (with options) to answer.
The punnett square shows the possible what, and their most likely ratios? | [
"chromosomes",
"genotypes",
"phenotypes",
"receptors"
] | B | If the parents had four offspring, their most likely genotypes would be one BB, two Bb, and one bb. But the genotype ratios of their actual offspring may differ. That's because which gametes happen to unite is a matter of chance, like a coin toss. The Punnett square just shows the possible genotypes and their most likely ratios. |
SciQ | SciQ-4610 | 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.
Angiosperms produce their gametes in separate organs, which are usually housed in these? | [
"flowers",
"leaves",
"stems",
"seeds"
] | A | Flowers and Fruits as an Evolutionary Adaptation Angiosperms produce their gametes in separate organs, which are usually housed in a flower. Both fertilization and embryo development take place inside an anatomical structure that provides a stable system of sexual reproduction largely sheltered from environmental fluctuations. Flowering plants are the most diverse phylum on Earth after insects; flowers come in a bewildering array of sizes, shapes, colors, smells, and arrangements. Most flowers have a mutualistic pollinator, with the distinctive features of flowers reflecting the nature of the pollination agent. The relationship between pollinator and flower characteristics is one of the great examples of coevolution. Following fertilization of the egg, the ovule grows into a seed. The surrounding tissues of the ovary thicken, developing into a fruit that will protect the seed and often ensure its dispersal over a wide geographic range. Not all fruits develop from an ovary; such structures are “false fruits. ” Like flowers, fruit can vary tremendously in appearance, size, smell, and taste. Tomatoes, walnut shells and avocados are all examples of fruit. As with pollen and seeds, fruits also act as agents of dispersal. Some may be carried away by the wind. Many attract animals that will eat the fruit and pass the seeds through their digestive systems, then deposit the seeds in another location. Cockleburs are covered with stiff, hooked spines that can hook into fur (or clothing) and hitch a ride on an animal for long distances. The cockleburs that clung to the velvet trousers of an enterprising Swiss hiker, George de Mestral, inspired his invention of the loop and hook fastener he named Velcro. |
SciQ | SciQ-4611 | electromagnetism, charge
Title: Can a third kind of charge exist? Is it possible that apart from positive and negative charges, there is a third kind of charge that we have somehow, not discovered yet?
If not, is there some proof of the existence of only two types of charges? If we did discover some other phenomenon for which the description "charge" was appropriate, we would not call it an electrical charge. For example the gluons which bind an atomic nucleus together carry a triple-state charge which is called "colour charge" after the three primary colours of vision. The theory of electromagnetism is a complete and consistent description of certain natural phenomena. Anything coming outside that set of phenomena would come outside the theory of electromagnetism and we would not call it electrical charge.
The following is multiple choice question (with options) to answer.
What are the two types of charges? | [
"energy and mass",
"ions and neutrons",
"positive and negative",
"volume and acceleration"
] | C | Conservation of charge is the fourth of the five conservation laws in physics. There are two charges, positive and negative, and the conservation of electric charge indicates that the total charge in the universe remains the same. In any closed system charge can be transferred from one body to another or can move within the system but the total electric charge remains constant. |
SciQ | SciQ-4612 | genetics, snp, human-genome, data, variant
As noted, SNP is a single nucleotide polumorphism, whereas notation AA, Aa, aa, etc. may refer to many other types of mutation: e.g., these could be whole genes, differing on many locations. Another common type of mutation is insertions/deletions, where one gene may lack whole segments (rather than contain different nucleotides).
SNPs are used in particular contexts, where the change of genome is insignificant: e.g., when treating highly conserving human genome or when treating a variable genome on a short time scale, where only few changes happen. In this case we take the most frequent/initial genome as the reference and describe deviations from it as SNPs ("snips"). This is not always, possible - e.g., when multiple alleles are present (a single nucleotide can be in four states, A, C, G, T and all of these may have to be accounted for, e.g., when analyzing the evolution of viruses).
Depending on the problem, one may want to discuss population genetics of an organism in terms of genotypes or in terms of allels - even when a single organism carries multiple allele (e.g., two copies in a diploid organism). AA, Aa, aa are genotypes, whereas A, a are alleles. SNP is a change in allele rather than in a genotype. (But I do admit that biological language is often unprecise.)
The following is multiple choice question (with options) to answer.
What is the name for a change in a single nucleotide in dna? | [
"spontaneous mutation",
"cell regeneration",
"point mutation",
"adaptation"
] | C | A point mutation is a change in a single nucleotide in DNA. This type of mutation is usually less serious than a chromosomal alteration. An example of a point mutation is a mutation that changes the codon UUU to the codon UCU. Point mutations can be silent, missense, or nonsense mutations, as shown in Table below . The effects of point mutations depend on how they change the genetic code. You can watch an animation about nonsense mutations at this link: http://www. biostudio. com/d_%20Nonsense%20Suppression%20I%20Nonsense%20Mutation. htm . |
SciQ | SciQ-4613 | equilibrium
Title: Why doesn't the ocean gradually turn into hydrogen and oxygen gas? Maybe I'm wrong about this, but I thought I remembered from high school chemistry that all reactions are in equilibrium. Some equilibria are extremely far to the right or left, so they appear to react 100% or not at all, but even in those reactions there is a tiny amount on the unfavored side.
If that's not true, then the answer to this question will be short. But if it is true, then I have a question about the following reaction, and bodies of water like lakes and oceans.
$$
\ce{2H2O (liquid) <=> 2H2 (g) + O2 (g)}
$$
If I remember right, the energy change ($\Delta{H}$ or $\Delta{G}$) in that reaction strongly favors the left side, so water molecules are not breaking apart into gas in large numbers. However, it's a gas on the right side, so I imagine that if a water molecule at the surface of the ocean breaks into gas, those products will escape, and the $\ce{H2}$ and $\ce{O2}$ gas molecules are no longer in physical contact and have no chance to react again.
That makes me think that gradually the ocean would turn into hydrogen and oxygen gas, even if the left side of that equation were favored. That doesn't seem to be happening, so what am I missing? I don't normally think there is hydrogen gas floating around in the air, but perhaps there actually is enough that some of it is colliding with $\ce{O2}$ at the ocean surface and balancing the equilibrium.
Maybe I'm wrong about this, but I thought I remembered from high school chemistry that all reactions are in equilibrium. Some equilibria are extremely far to the right or left, so they appear to react 100% or not at all, but even in those reactions there is a tiny amount on the unfavored side.
The following is multiple choice question (with options) to answer.
Ocean acidification results from the ocean absorbing what gas from the atmosphere? | [
"carbon dioxide",
"nitrogen",
"hydrogen",
"oxygen"
] | A | The ocean is becoming increasingly polluted with trash. Ocean acidification is also occurring because ocean water dissolves some of the excess carbon dioxide in the atmosphere. The more acidic water harms aquatic organisms. |
SciQ | SciQ-4614 | 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 are organisms that feed on available plants called? | [
"grazers",
"antigens",
"florophores",
"plantfeeders"
] | A | Grazers, such as sea urchins, are organisms that feed on available plants. Sea urchins are omnivorous, eating both plant and animals. The sea urchin mainly feeds on algae on the coral and rocks, along with decomposing matter such as dead fish, mussels, sponges, and barnacles. |
SciQ | SciQ-4615 | hygiene, food-chemistry
Dishes and utensils are only susceptible to bacterial growth if there's traces of food on them. Washing is meant to remove traces of food and oil so bacteria can't multiple on them. The conditions must be right for bacteria to multiple. If traces of food were to be completely dry and hardened on a dish and someone ate off it, the likelihood of any bacteria present on it is close to nil. They need moisture to grow. If dishes had no oily food on them, washing and rinsing with very warm water would be sufficient. I've seen people from other cultures wash dishes with traces of food that are soluble in water. They come out perfectly clean. (As an aside, using a tea towel can often spread bacteria when they're not used properly.) Towels top kitchen contamination hazards list
Bacteria can't multiple in oil. For example, ordinary cooking oil doesn't need to be refrigerated although it can go rancid. A cast iron frying pan is properly meant for frying foods only. No watery sauces should be cooked in them. Even "scraping it clean" shouldn't be done with a sharp metal object as it can remove some of the polymerized hardened oil layer.
I have several cast iron pans that I don't wash. I wipe them out after each use, then I add a little oil nd roughly a teaspoon of salt. With a paper towel, I rub at any bits of stuck on food. If done within a few hours of being used, it effectively removes any food traces, leaving a smooth surface. I usually rinse off the salt in warm water, dry it and then apply a very thin film of oil. I've been cooking in cast iron pans for decades and have never gotten sick or had mild food poisoning (what many people call a 'stomach flu').
Cast iron pans with a layer of proper seasoning and treated like this will definitely not cause sickness. It can't support bacterial growth and as @jeanquilt mentions, the pan gets very hot - enough to blister your skin if you touch them with a bare hand.
The following is multiple choice question (with options) to answer.
What is the limiting factor for bacteria in a dish? | [
"speed",
"space",
"material",
"density"
] | B | The blades of simple leaves are not divided. This provides the maximum surface area for collecting sunlight. |
SciQ | SciQ-4616 | microbiology, bacteriology, ecology, environment, freshwater-biology
Here's a graph showing the relative amounts of various taxa found in their samples:
How Many Bacteria?
DeLeon-Rodriguez et al's (2013) results revealed an average bacterial concentration of somewhere between $5.1 × 10^3 cells / m^3$ to $1.5 × 10^5 cells / m^3$ of cloud (depending on method of counting).
Quickly doing some math (1 m$^3$ = 1000000 mL), their results suggest that, on average across a cubic meter of cloud, there is <1 bacteria / mL of moisture.
According to research by Joly et al (2014) that specifically examined ice nuclei (or "IN"):
there were 0 to ~220 biological IN/mL of cloud water (i.e. 0-22 per m$^3$ of cloudy air based on cloud liquid water content estimates) and these represented 65% to 100% of the total IN.
Comparatively, river water (and drinking water) can contain a lot more bacteria (i.e., 80,000 bacteria / mL) and other microorganisms.
However, this disparity is not always so great, especially if we focus at comparing counts of only one or a few species (and not total bacterial counts).
Based on research of a tropical reservoir by Kaushik et al (2014):
Levels of E. coli were found to be in the range of 0 CFU/100 mL – 75 CFU/100 mL for the rainwater, and were 10–94 CFU/100 mL for the reservoir water.
Note: CFU = colony forming units. (estimation of microbial numbers by CFU will, in most cases, undercount the number of living cells. [wikipedia]).
Citations
The following is multiple choice question (with options) to answer.
Where are some of the greatest concentrations of species found? | [
"in the arctic",
"in the tropics",
"in mould colonies",
"at high altitudes"
] | B | |
SciQ | SciQ-4617 | physiology, herpetology, poison, amphibians
+
0.002 mg/L will fatally damage the sensitive skin on tadpoles, frogs, salamanders and other amphibians.
another source:
Free chlorine (Cl2) is a greenish gas that is well known for its
highly toxic properties as can be attested to by the thousands of
soldiers that died and were severely injured from chlorine exposure
during World War I. In water, chlorine is the most toxic substance
that we will discuss. Ironically for the amphibian keeper, it is this
toxic nature of chlorine and its ability to denature proteins, which
makes its encounter inevitable. Chlorine is generally used as an
antibacterial agent in municipal water supplies and may be present in
concentrations of over 9 mg/1 in some tap water (measured in Houston,
Texas as an example, although levels were generally lower). The
concentration of chlorine in municipal water supplies can vary greatly
from day to day, or even hour to hour, depending on conditions at the
water treatment facilities. Concentrations as low as 0.0034 mg/1 have
been noted to reduce reproduction in fathead minnows with 72 hour
LC100 (lethal concentration for 100% kill) at 0.15 mg/1 (Arthur and
Eaton,1971). LC50 (96 hour) for the shiners (Notemigonus chrysoleucas)
was as low as 0.19 mg/1 (Esvelt et al., 1971). The concentrations
found in municipal water supplies are many times greater than the
minimum lethal concentrations for many aquatic life forms.
Thus, the well being of the frog in the water of the swimming pool depends on the time the frog spends in the water. Eventually, with extended exposure the chlorine concentration will exceed the one compatible will life and the frog will die. This time is multifactorial variable, thus cannot be assessed easily - the weight and the skin surface area and skin permeability will affect the frog survival in a great degree.
The following is multiple choice question (with options) to answer.
What do tadpoles clear out of waterways? | [
"disease",
"algae",
"oxygen",
"pollution"
] | B | Amphibians play important roles in many ecosystems, especially as middle players in many food chains and food webs. In addition to consuming many worms and insects and other arthropods, and even some small reptiles and mammals and fish, they are prey for turtles and snakes, as well as some fish and birds. Tadpoles keep waterways clean by feeding on algae. |
SciQ | SciQ-4618 | seismology, earthquakes, plate-tectonics
Title: Fault representation In most illustrations and diagrams of the types of faults, there is always something similar. I noticed that there is a side of the hanging wall and foot wall which is slanted.
We're supposed to make a models for each type of fault; however, the material to be used will be difficult to cut diagonally. I'd like to know if it is necessary to have one side slanted? Or if having it vertical fine.
Please mention sources too. Thank you. Faults are results of stress. The direction of the stress controls what kind of fault that is formed. The most fundamental reason for a fault to occur is horizontal compression or extension, even if it's often more complicated in reality.
Your two examples are dip-slip faults, with a vertical displacement as a result of horizontal stress.
In your first example, the normal fault. The total distance (from left to right) is increased. There has been an extension of the crust. If the fault plane would have been vertical, no distance would have been gained.
In the second example, the reverse fault, the distance is decreased. It's been a horizontal compression of the crust. The dip of a reverse fault is usually rather steep. If the dip is lower, you'll rather form a ramp. Typical for thrust faults.
Vertical fault planes are associated with strike-slip faults or ring faults above collapsing calderas or sinkholes. It's also common, but not for textbook examples of dip-slip faults.
So, unless you are showing a strike-slip fault, you have to find a way to cut diagonally. Do measure the horizontal displacement!
Addition about making fault models:
We made a layer cake for a college some time ago and (of course) wanted to have a fault in it. The simplest way was to make a reverse fault, erode the uppermost layer of the hanging wall block and assume that the lowest exposed layer was of the same lithology (chocolate sandstone reservoir rock). However, it took some geoenginering to make it look good and we decided to make an impact crater next time.
The following is multiple choice question (with options) to answer.
What theory says stresses build on both sides of a fault? | [
"seismic load theory",
"Geiger theory",
"Big Bang theory",
"elastic rebound theory"
] | D | Elastic rebound theory. Stresses build on both sides of a fault. The rocks deform plastically as seen in Time 2. When the stresses become too great, the rocks return to their original shape. To do this, the rocks move, as seen in Time 3. This movement releases energy, creating an earthquake. |
SciQ | SciQ-4619 | human-genetics
Title: In our 23 chromosome pairs, do the 2 members of the pair have distinct or virtually identical sequences? I understand that we have 46 DNA molecules in the nucleus of our cells, arranged in 23 pairs: 22 autosomal and 1 sex chromosome pairs.
I have read in different sources that the pairs contain nearly identical members, excluding any mutations. I have also read that the pairs contain 1 member we inherited from our mothers and 1 we inherited from our fathers, which are different due to inheritance.
This seems contradictory, given that genealogical companies match up on the differences on these chromosomes.
My understanding was that meiosis creates sperm and egg cells that each carry 23 chromosomes - they are haploids. During the first steps of meiosis that creates the reproductive cells we have a combining of the parent's chromosome pair from their parents to create 4 daughter cells, each independently viable, where the recombination of the chromosome pair has occurred at somewhat predictable spots (for you perhaps :-) ) and that these spots can be related to genes. It is this step that give us our genetic variation between siblings for example. A new person's DNA is partially formed from any one of these highly varied daughter cell possibilities.
Fertilization combines the reproductive cells to produce the 46 chromosome zygote with is again diploid.
I think this understanding supports the second interpretation that our chromosome pairs are not 2 nearly identical DNA molecules but are distinct.
Have I got this right? Is there a missing process or a misunderstanding in my interpretation? Homologous chromosomes (those that are paired up), excluding the sex pair are almost identical in size, shape and genes (members as you called them) present in them.
Genes determine traits and each homologous chromosome controls the same traits. The level of identity of a gene inside a population varies between genes. There are very conserved ones that do not change even between humans and yeast and others that vary alot event inside a species. This changes can be small in sequence length, a simple base (letter) swap or one deletion, and have a huge effect on the traits. This is how chimps and humans are very different but share 98.6% of their genome and humans are very similar and share 99.9% of their genome.
In summary, on the bigger scale homologous chromosomes are very similar (size, shape, traits inside), on the smaller scale homologous chromosomes have small changes that affect greatly.
The following is multiple choice question (with options) to answer.
How many pairs of autosomes are there? | [
"five",
"four",
"three",
"Seven"
] | C | |
SciQ | SciQ-4620 | organic-chemistry
Title: What are the minimal chemical requirements for a food which we all can eat? I've been puzzled by the following though experiment for the past few days:
I want to make my own food from scratch, but I do not know where to start from.
I want to be 100% sure that what I eat will never contains something that can damage my body. For example: If you buy something from the local market you can not be 100% sure that it's safe to eat. (99.9 % maybe... but that's not 100%)
I want to ask you to tell me, how can I make a food that I can eat, or should I say - live on it, for the rest of my life, that's 100% safe, I can control every aspect of it's creation and has many combinations of taste because I love diversity.
Thank you for your time : )
Edit:
Because I realized my question is very broad and indeed is a little... too much scientific I want to close it. But before I do so, here's what I had in mind:
I wanted to take some chemical elements, put them in a jar, run some electricity, heat, whatever through it, filter it, do some additional processing and eat it.
I wanted to know if the stomach can take it, because I was going to eat food that's not hard to digest. Considering the three basic biomolecules used by the body are carbohydrates, lipids, and proteins, you would need to consume these three molecules only. Now we can choose three substances.
Glucose, one of the most basic carbohydrates, is needed for ATP production, so that would be a food choice there.
Any oil or butter will provide lipids.
Protein comes from a variety of sources. Meat is typically though of as the best, but nuts are a pretty good source too.
Since nuts satisfy proteins and lipids, I'd say honey roasted peanuts are the most basic food you could live off of, if you replace pure glucose for the honey.
The following is multiple choice question (with options) to answer.
What are the only living organisms that can make their own food? | [
"plants",
"bacteria",
"protozoa",
"animals"
] | A | |
SciQ | SciQ-4621 | neuroscience, neuroanatomy
Likewise, the spinal chord is structured into sensory and motor regions. In summary, the spinal chord consists of: 1) cell bodies (motor, sensory, inter; grey in the picture), 2) ascending axons (blue), 3) descending axons (red). Similar to nerves, axons going up or down the spinal chord are bundled into "tracts". Sensory axons are never bundled with motor axons, making it possible to create a map of the spinal chord in cross-section.
The tracts' names might be a bit confusing at first, but on second look are actually pretty self-explanatory. They usually contain where the axons come from and where they are going in order to synapse with other neurons. E.g. the spinocerebellar tract is formed of axons coming from the spine and going to the cerebellum. Given that the cerebellum is near the brain and the spine is further down, this is obviously an ascending tract - and ascending tracts are always sensory (because sensory information never needs to be carried downwards due to the brain being at the top).
Where it gets blurry
The sensory/motor separation isn't always as clear as I've described above. In fact, nerves (bundles of axons anywhere in the body outside of the CNS) will usually contain both sensory and motor pipelines. In particular, the cranial nerves (12 of the most important nerves) all include sensory and motor components for the respective part of the body that they manage. E.g. the facial nerve contains both the sensory connections for parts of the tongue and the motor connections that control facial muscles.
Another more complex example is pain sensation, where interneurons in the spinal chord can feed back onto sensory neurons and inhibit their signals, or axons can inhibit those packed in the same nerve bundle simply due to electrical effects.
The following is multiple choice question (with options) to answer.
The brain and spinal cord are part of what system, which serves as a control center? | [
"primary nervous system",
"large nervous system",
"central nervous system",
"active nervous system"
] | C | The central nervous includes the brain and spinal cord. The brain is the control center of the nervous system. It controls virtually all mental and physical processes. The spinal cord is a long, thin bundle of nervous tissue that passes messages from the body to the brain and from the brain to the body. |
SciQ | SciQ-4622 | waves, atmospheric-science, turbulence
The clouds form if the rising air reaches the lifted condensation level before the updrafts are stopped by an inversion or stable layer. The air is (relatively) clear above the downdrafts. If the convection rolls were perfectly circular, the cloud row spacing would be twice the height of the inversion/stable layer.
Mathematically, there are many wavelength solutions to convection, but the wavelength that dominates is the fastest growing one. In the Boussinesq approximation, which is reasonably valid here, this turns out to have a wavelength of $2\sqrt{2}\sim 3$ times the height of the convecting layer, i.e. slightly flattened. (See, for example, Eq. 21 of Kuettner (1971) "Cloud bands in the earth's atmosphere: Observations and Theory".)
For typical cumulus cloud heights of $\sim 2$ km, we expect typical spacings of about $6$ km.
Wave, lee, or mountain clouds are lines of clouds downwind of an obstacle (such as a mountain range). The lines are parallel to the wind direction. These are buoyancy waves where wind pushes denser air over an obstacle (e.g. a mountain range) and it ends up above less dense air on the other side. This dense air starts to fall but it overshoots into even higher density air at lower altitude, which forces it back up, and the air ends up bouncing up and down until the oscillations die out. If the vertical temperature profile of the air then is known, it is possible to estimate the vertical buoyancy angular frequency
$$N=\sqrt{\frac{g}{\theta}\frac{d\theta}{dz}}$$
The following is multiple choice question (with options) to answer.
What are the highest clouds in the atmosphere? | [
"alto clouds",
"silicic clouds",
"nebulous clouds",
"noctilucent clouds"
] | D | Noctilucent clouds are the highest clouds in the atmosphere. |
SciQ | SciQ-4623 | genetics
Additional response added as requested:
I see what you are getting at - why do children seem like such individual and unique things sometimes?
In sexual reproduction, the offspring are the product of the shuffling of the parent's genomes through meiosis, where the pairs of chromosomes we have are combined to make a single chromosome that will be half of the children genome.
This process can result in completely novel combinations of genes while conveying many likenesses from the parent. I would guesstimate that this is the major cause of the uniqueness of offspring/children.
Also in mammals there are some cell lines which splice families of genes which will cause offspring to be potentially quite different from either parent. Immune genes for instance are created from scratch from a bunch of genes that the parents give. Making each offspring unique but also the product of the parent's genetic repertoire. This can be significant as it affects health and also to some extent attraction - studies have shown that people who smell attractive to us are immunologically distinct from us.
@David mentions epigenetic variation, which is a more recent significant development. During our life, the germline (sperm/egg) DNA may be chemically labelled depending upon environmental conditions we experience. A famous example is experiencing famine conditions, which caused the children to be born on the small side amongst other effects. More recent studies have shown that this is a widespread mechanism to control cells in our body during our lifetime as well as communicate to our offspring how life is. It is expected that this labeling does not affect us forever - the epigenetic labels change over the course of a generation quite often (we believe).
The following is multiple choice question (with options) to answer.
What type of reproduction results in genetically unique offspring? | [
"internal reproduction",
"sexual reproduction",
"asexual reproduction",
"mitosis"
] | B | Sexual reproduction results in offspring that are genetically unique. They differ from both parents and also from each other. This occurs for a number of reasons. |
SciQ | SciQ-4624 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
What is a disorder of glucose metabolism in which insulin production by the pancreas is impaired? | [
"populations mellitus",
"diabetes mellitus",
"cluster mellitus",
"sugar mellitus"
] | B | Diabetes mellitus is a disorder of glucose metabolism in which insulin production by the pancreas is impaired. Since insulin helps glucose enter the cells, a decrease of this hormone means that glucose cannot be used in its normal fashion. When this happens, the body begins to break down fats, producing a decrease in blood pH. Chemical systems in the body can balance this pH shift for a while, but excessive acid production can create serious problems if not corrected by administering insulin to restore normal glucose use. |
SciQ | SciQ-4625 | quantum-mechanics, nuclear-physics, atomic-physics, atoms
Title: Could I turn into a nuclear bomb? Just out of curiousity, could the nuclei of our atoms split via quantum tunnelling, thereby leading to nuclear reactions and ultimately turning us into atomic bombs? I know that this is near-impossible, but wondering if it was technically possible. The thing is, we're made of mostly stable matter of low atomic number. In a nuclear bomb, unstable nuclei split, releasing a number of energetic neutrons which strike other unstable nuclei, and the reactions chain uncontrollably. Splitting a small nucleus actually costs energy, so even if a carbon atom in your body did split, it would only split into smaller, still low-energy atoms, which would interact normally with other atoms in your body. A couple extra lithium or helium atoms isn't going to do anything drastic.
The following is multiple choice question (with options) to answer.
Splitting of the nucleus of a radioactive atom into two smaller nuclei yields what type of reaction, which releases a great deal of energy from a small amount of matter? | [
"nuclear fission",
"nuclear fusion",
"solar fission",
"nucleation"
] | A | Nuclear fission is the splitting of the nucleus of a radioactive atom into two smaller nuclei. This type of reaction releases a great deal of energy from a very small amount of matter. Fission of a tiny pellet of radioactive uranium-235, like the one pictured in the Figure below , releases as much energy as burning 1,000 kilograms of coal!. |
SciQ | SciQ-4626 | general-relativity, accelerator-physics
More realistically though, we accelerate particles so we can study the physics during collisions of two particles. When we collide electrons and positrons for instance, nearly 100% of the energy carried by the particle is deposited into the reaction if they collide head on, its this fact that lets us see the creation of new and exotic particles following the collision (And why LEP began seeing Z bosons as soon as they crossed the 180GeV threshold). When we move to the LHC for example, we are colliding two protons- which, roughly speaking are sacks of consisting of 3 quarks. And the momentum (and therefore the energy) of the proton is more or less evenly distributed among the three quarks. So the energy available to us in the collision is actually about 6 times less than an eqiuivalent electron-positron collider. Imagine doing this with a baseball, which is composed of trillions of trillions of particles. The energy that each particle carries is a tiny fraction of the total energy of the baseball, therefore every single collision event only has a tiny fraction of the total energy of the system, and in the end we get no useful reaction out of a collision that could not have just as easily been accomplished by putting two televisions face to face.
The following is multiple choice question (with options) to answer.
Colliding-beam accelerators create matter from what? | [
"minerals",
"magnetism",
"sound",
"energy"
] | D | Conceptual Questions 33.3 Accelerators Create Matter from Energy 1. The total energy in the beam of an accelerator is far greater than the energy of the individual beam particles. Why isn’t this total energy available to create a single extremely massive particle? 2. Synchrotron radiation takes energy from an accelerator beam and is related to acceleration. Why would you expect the problem to be more severe for electron accelerators than proton accelerators? 3. What two major limitations prevent us from building high-energy accelerators that are physically small? 4. What are the advantages of colliding-beam accelerators? What are the disadvantages?. |
SciQ | SciQ-4627 | newtonian-mechanics, buoyancy, thought-experiment
Likewise if a person stands on a scale and pulls up really hard on a handle connected to the scale, the scale still measures exactly the person's mass times $g$. The force that the person pulls up is countered by additional force in his feet, which is also directed into the scale.
So now what about the situation after cutting the string? Like I said we need to think about the water accelerating down, not just the ball moving up. To make the geometry more trivial my ball is a square, but rest assured the answer in the end does not depend on the shape of the ball.
The following is multiple choice question (with options) to answer.
What is the term for the measure of the force of gravity pulling down on an object? | [
"weight",
"mass",
"density",
"pressure"
] | A | Weight is a measure of the force of gravity pulling down on an object. It depends on the object’s mass, which is how much matter the object contains. It also depends on the downward acceleration of the object due to gravity, which is the same all over Earth. Weight can be represented by the equation:. |
SciQ | SciQ-4628 | human-biology, senescence
Title: Could inhibition of progerin formation slow the rate at which a body ages? According to wikipedia, progerin is activated in senescent cells. The protein itself is known to be the cause of a rare affliction 'progeria' - a disease marked by accelerated aging of the body. This disease is not accompanied by neurodegeneration.
Is progerin the key factor in the aging process?
If yes, could inhibition of progerin formation control the rate at which a body ages? Progeria (and related) syndromes are essentially a collection of 'accelerated aging' phenotypes caused by single mutations; Progerin is a shortened version of the protein Lamin A, and is therefore not found in individuals without a loss-of-function mutation in the LMNA gene (the wiki page you reference). As far as we are aware these genes do not 'cause' aging in individuals without the mutations.
LMNA is a normal component of the nuclear lamina (a structure inherent to the nucleus). This review discusses the various diseases associated with mutations in this gene, some of which present 'accelerated aging' phenotypes. However, as far as I know, there is limited evidence to suggest that LMNA, or indeed any Lamina associated protein, is involved in 'normal aging'. A recent GWAS meta-analysis found a variant in LMNA that is associated with longevity in humans, however the association is relatively weak (OR=1.18, P=7(x10)-4), so even if this is a true association, it seems that (as usual in aging research) there are many other factors to consider, and it is not a single gene that is doing the aging.
So to stress the point: progerin has no function in 'normal' human aging - it is a defective protein caused by a germline (or novel) mutation in the LMNA gene. Accelerated aging is the symptom of this genetic disorder, and is not completely analogous to normal aging (as you point out, there is no cognitive decline that is associated with normal human aging).
The following is multiple choice question (with options) to answer.
Aging is associated with the death of what? | [
"cells",
"muscles",
"genes",
"proteins"
] | A | Aging is associated with the death of cells. Give two reasons why cells die. |
SciQ | SciQ-4629 | evolution, taxonomy
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but do not breed freely with members of another species in the wild.
That last part takes care of the ligers and tiglons. But what if we consider plants? Under the definition I just gave, most grasses (around 11,000 species) would have to be considered as one species. In the wild, most grasses will freely pollinate related species and produce hybrid seed, which germinates. You might then think we could just modify the definition to specify that the offspring must be fertile (i.e. able to reproduce with one another)...
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but do not breed freely with members of another species in the wild to produce fertile progeny.
Unfortunately, the situation is still more complicated (we've barely started!). Often wild hybridisation events between plants lead to healthy, fertile offspring. In fact common wheat (Triticum aestivum) is a natural hybrid between three related species of grass. The offspring are able to breed freely with one another.
Perhaps we could account for this by taking into account whether the populations usually interbreed, and whether they form distinct populations...
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of populations or meta-populations of related individuals that resemble one another, are able to breed among themselves, but do tend not to breed freely with members of another species in the wild to produce fertile progeny.
The following is multiple choice question (with options) to answer.
Animals that live in groups with other members of their species are called what? | [
"social animals",
"grouping animals",
"available animals",
"aggressive animals"
] | A | Without communication, animals would not be able to live together in groups. Animals that live in groups with other members of their species are called social animals. Social animals include many species of insects, birds, and mammals. Specific examples are ants, bees, crows, wolves, and human beings. |
SciQ | SciQ-4630 | ecology, biogeography
Edit in response to comments
Comment about biome scale
The reason behind the scale comment is that typically we observe succession for a given habitat. Part of this stems from the origin of the succession ideas, where Frederic Clements posited that climate was the major driving factor of successional trajectories (Clements 1916). This would actually fit well with the biome view of succession, however in order for this model to explain all the variation we see in the world (eg. why a tree grows in location X but not location Y 4 metres away), you devolve into splitting the world into infinitesimally small micro-climates. Henry Gleason proposed a more individualistic model, which suggested that climate was just one influence, and that each plant species responds to a myriad of different environmental cues (Gleason 1927). The sum of these responses results in the community at a given location. This seems to fit better with our current understanding of succession but is not without problems. In a Gleasonian model, any variation can be expected to result in a different community. Since it would be strange for the pampas region to be homogeneous over 1.2 million km2, there are likely distinct communities within the biome, each developing as a result of factors like soil moisture, soil chemistry, climate, wind exposure, and herbivore use. One can still talk about succession at a biome scale, but at that scale we would be thinking about what factors lead the pampas region to become a grassland, rather than what factors lead grass X, tree Y and forb Z to coexist next to each other.
Factors maintaining grassland type ecosystems are fairly uniform globally. You need some sort of event that will kill woody vegetation but not kill grasses and forbs. Fire and grazing are natural examples (Briggs et al. 2002), but mowing would also maintain grassland (Fidelis et al. 2012). Earthquakes are unlikely to maintain grassland as trees and shrubs are likely to survive earthquakes.
Comment about global pampas
The following is multiple choice question (with options) to answer.
What are typically named for their major physical or climatic factors in addition to their predominant vegetation? | [
"aqueous biomes",
"terrestrial biomes",
"communities",
"habitats"
] | B | |
SciQ | SciQ-4631 | species-identification
Title: Identification of a lifeform There's a video I found on Facebook and I'm unable to figure out what the creature featured happens to be.
Adding images that have been taken from the video itself, apologies in advance since they're not high qualify images.
Can anybody shed any light on what it is?
The video was shot near Ratan Babu Ghat which is situated along the bank of Hooghly river, Kolkata, West Bengal, India. Here to be precise. This is a polyclad flatworm.
Here is a video of notoplana vitrea moving similarly to the one in the video that you linked:
https://www.asturnatura.com/especie/notoplana-vitrea.html
Here is a gallery of polyclad flatworms observed in India:
https://inaturalist.ca/observations?place_id=6681&subview=grid&taxon_id=52318
A number of the images in this gallery look similar to the one in your video, but very few of them are identified beyond this order taxon of polyclad flatworm.
The following is multiple choice question (with options) to answer.
What type of vents are giant tube worms found at? | [
"oxygen",
"hydrothermal",
"Heated",
"temperature"
] | B | Giant tube worms are found at hydrothermal vents. They get food from the chemosynthetic bacteria that live within them. The bacteria provide food; the worms provide shelter. |
SciQ | SciQ-4632 | newtonian-mechanics, forces, work, displacement
Title: If application of force does not result in spatial movement, has work been done? I'm trying to help my kids why their elementary-school physics. Their lesson today says that "work" is done only when a change in position is accomplished by the applied force. I have absolutely no background or training in physics whatsoever.
So my question is if two people were to stand facing each other with a book (or another object) between them, and they both applied equal force to opposite sides of the book (each person attempting to push the book toward the other person) would that be "work" in the physics sense?
Since each person is accomplishing a change in the book's movement (stopping it from moving) would that not be considered work?
I guess my question involves two forces instead of one. Maybe that makes a difference? No. No work would be done in this case, at least not at the macroscopic level. Work is the product of force and displacement in the direction of the force and in this case there is no displacement.
I disagree with you that each person is "accomplishing a change in the book's movement". The book wasn't moving initially, or at the end, or at any time in between. The situation is exactly the same as if two people had been trying to push the book through a solid wall.
Be careful when using the human body in questions where you are asking how much work has been done. If you actually try what you propose you will find that you will get tired. Your muscles are losing chemical potential energy but you are not doing work on the book. At the microscopic level your muscle fibers are contracting and slipping and contracting again so at that level work is being done.
I find it more instructive to think of replacing the people in examples like these with some sort of simple mechanical device. You could lean something up against the book, use a clamp or set up some other simple mechanical system which would continue to apply a force but would require no ongoing energy input, which makes it clearer that no work is being done.
The following is multiple choice question (with options) to answer.
What results when a force does work? | [
"momentum",
"movement",
"pressure",
"side effect"
] | B | work: A force is said to do work when it acts on a body so that there is a displacement of the point of application, however small, in the direction of the force. Thus a force does work when it results in movement. The work done by a constant force of magnitude on a point that moves a distance in the direction of the force is the product, . |
SciQ | SciQ-4633 | thermodynamics, pressure, atmospheric-science, density, air
Title: Why does air pressure decrease with altitude? I am looking to find the reason: why air pressure decreases with altitude? Has it to do with the fact that gravitational force is less at higher altitude due to the greater distance between the masses? Does earth’s spin cause a centrifugal force? Are the molecules at higher altitude pushing onto the molecules of air at lower altitudes thus increasing their pressure? Is the earths air pressure higher at the poles than at the equator? The air pressure at a given point is the weight of the column of air directly above that point, as explained here. As altitude increases, this column becomes smaller, so it has less weight. Thus, points at higher altitude have lower pressure.
While gravitational force does decrease with altitude, for everyday purposes (staying near the surface of the Earth), the difference is not very large. Likewise, the centrifugal force also does not have significant impact.
The following is multiple choice question (with options) to answer.
At the earth’s surface, the air pressure exerted on you is a result of the weight of what above you? | [
"air",
"magnetic force",
"humidity",
"water"
] | A | 11.4 Variation of Pressure with Depth in a Fluid If your ears have ever popped on a plane flight or ached during a deep dive in a swimming pool, you have experienced the effect of depth on pressure in a fluid. At the Earth’s surface, the air pressure exerted on you is a result of the weight of air above you. This pressure is reduced as you climb up in altitude and the weight of air above you decreases. Under water, the pressure exerted on you increases with increasing depth. In this case, the pressure being exerted upon you is a result of both the weight of water above you and that of the atmosphere above you. You may notice an air pressure change on an elevator ride that transports you many stories, but you need only dive a meter or so below the surface of a pool to feel a pressure increase. The difference is that water is much denser than air, about 775 times as dense. Consider the container in Figure 11.10. Its bottom supports the weight of the fluid in it. Let us calculate the pressure exerted on the bottom by the weight of the fluid. That pressure is the weight of the fluid mg divided by the area A supporting it (the area of the bottom of the container):. |
SciQ | SciQ-4634 | organic-chemistry, acid-base, biochemistry, enzymes, medicinal-chemistry
Title: Betaine HCl stomach pH It seems betaine HCl is often recommended for those suffering from "low stomach acid" -- which, as I understand, is having too high stomach pH for proper digestion (especially for proteolysis via pepsin). However, I have a few questions then -- though I'm not sure if my reasoning is correct here:
Understandably, one wouldn't want to drink pure or highly concentrated HCl by itself to increase stomach acid! But then, what role does the betaine play?
I'm guessing betaine HCl probably does not dissolve in water to give the same pH as just straight (or concentrated) hydrochloric acid -- since then it would seem just as dangerous as drinking plain HCl!
In that case, if it doesn't decrease the pH as much, making it safe for oral consumption, what value does it bring for "lowering stomach pH" anyway? I mean, one could just drink a little vinegar or citric acid for the same effect?
Or, perhaps, is betaine-HCl just a means of some "delayed release" of HCl to lower stomach pH without hurting the mouth and esophagus during its initial consumption? Betaine may just be a useful amphoteric here, given it's quarternary ammonium and carboxylic acid groups (although not just any amphoteric, such as water, may suffice here!)
Alternatively, could the value of betaine HCl simply be in providing a source of $\ce{Cl-}$ anions, possibly for increased pepsin activity? (I'm not sure if pepsin requires merely low pH or specifically also needs $\ce{Cl-}$ anions as well) Betaine-HCl seems to be often formulated with additional pepsin enzyme(s) as well... Looks like I was right to be skeptical, according to WebMD:
The following is multiple choice question (with options) to answer.
What is a common condition caused by stomach acid? | [
"arthritis",
"heartburn",
"headache",
"sunburn"
] | B | Have you ever experienced heartburn? Heartburn is actually a condition caused by stomach acid, rather something in your heart. The stomach produces HCl, which is a necessary component of digestion. However, excessive amounts of stomach acid can cause a great deal of discomfort. Various factors can cause the overproduction of acid, mostly related to the types (and amounts) of food and beverages that are being consumed. Caffeine and other oils in coffee (even decaf) will increase HCl production in the stomach. Smoking cigarettes and drinking alcohol also increase the formation of stomach acid. |
SciQ | SciQ-4635 | ecology, database, biodiversity, species-distribution
Title: Database of Geographic Range of Species Is there a database of organisms which would contain their queriable geographic location?
I would need to perform a rather simple query, such as Animals of <Location>, where Location is some well defined geographic area such as Czech Republic or Europe.
So far I have found multiple lists on Wikipedia and other webpages, however they seem to be quite incomplete as their intersect is quite small. Moreover, I have found EOL (Encyclopedia of Life) collections but they appear to struggle the same way. This is to a large extent a question of how reliable the data in the database needs to be. Reliability (and spatial scale) will differ between datasets and between species groups within datasets, and it is difficult to give a general recommendation. I doubt that you will find a single database with good coverage over all taxonomic groups, even if it is in the form of country checklists. For the most reliable information, curated country checklists for specific taxonomic groups will probably be best, but these have to be searched for individually for each taxonomic group of interest.
As a starting point, you might want to look at the occurence data that can be found in gbif.org (The Global Biodiversity Facility). The data found there is certainly not complete, and it will be misleading for many species. However, for the current distribution of relatively well-known groups of species it will give you a good idea of their distribution. This has to be evaluated on a case-by-case basis though. You can access the data in gbif using external tools, for instance using R through rgbif (there is also tools for python or other languages). At the blog recology.info you can find a tutorial on how to get a species list for a particular country using rgbif (more specifically the function density_spplist).
The following is multiple choice question (with options) to answer.
Where do the majority of species live? | [
"ocean",
"land",
"air",
"trees"
] | A | Mollusks live in most terrestrial, freshwater, and marine habitats. However, the majority of species live in the ocean. They can be found in both shallow and deep water and from tropical to polar latitudes. They have a variety of ways of getting food. Some are free-living heterotrophs. Others are internal parasites. Mollusks are also eaten by many other organisms, including humans. |
SciQ | SciQ-4636 | geology, oceanography, geochemistry, mineralogy
Title: Will the sea get saltier forever? The sea wasn't always salty. It's been getting saltier over millions of years as minerals dissolve.
Is there a natural limit to this process, or the will the sea keep getting saltier forever?
Is there a natural process which removes salt from the sea at a significant rate?
How long would it take for the sea to get too salty to support life as we know it? No there are natural processes that remove salt as well.
as sea level changes water gets trapped in basins and evaporates leaving the salt behind, this is where many of the salt formation on earth came from. whenever sea levels fall the salinity of the ocean drops. Tectonically isolated basin can remove salt in the same way. The process can even happen repeatedly in the same basin as sea level changes.
There are biological processes that remove it as well the formation of shells and limestone remove some of the ocean salts.
Can it increase yes, but it can also decrease, over earths history there have been saltier and less salty periods.
The following is multiple choice question (with options) to answer.
What process brings nutrients from the ocean's floor to its surface? | [
"Tides",
"upwelling",
"coastal swell",
"Down welling"
] | B | Upwelling brings nutrients to the surface from the ocean floor. Nutrients are important resources for ocean life. However, they aren’t the only resources on the ocean floor. |
SciQ | SciQ-4637 | waves, terminology, distance, displacement
Title: Inconsistency in definition of antinodes Definition of antinode according to google: the position of maximum displacement in a standing wave system
And displacement is a vector, so therefore, the crests would be the maximum while the troughs are the minimums.
From this, we can draw the conclusion that crests are antinodes while troughs can't be, as they're negative values.
However, the following graph shows otherwise:
Something seems to be wrong here. If both crests and troughs are antinodes, then shouldn't the definition for antinodes be 'the position of maximum DISTANCE', where minimums and maximums have the same magnitudes? There is nothing wrong with the definition in terms of displacement because half a period later the graph looks like this.
So perhaps it would be better to have it as
the position where maximum displacement occurs in a standing wave
system
You could also use the terms "maximum amplitude" or "maximum magnitude of the displacement".
The following is multiple choice question (with options) to answer.
Crests and troughs are the high and low points of a what? | [
"darker wave",
"heat wave",
"rupture wave",
"transverse wave"
] | D | Crests and troughs are the high and low points of a transverse wave. |
SciQ | SciQ-4638 | food, decomposition
Title: Worm compost cannot have cooked food I live in the Netherlands and it is getting fashionable to compost with worms. After investigating a few websites I noticed that most websites suggested that I cannot feed the worms leftovers from citrus fruits. This seems logical. I then started noticing that people advise against feeding the worms cooked food.
I'm no biologist but I cannot imagine a reason why cooked food is bad for the worms. Could anybody explain why this might be in layman’s terms? There are a few reasons for not feeding cooked foods to worms (Eisenia spp.) in a smaller household size worm farm. It's not because the food is cooked but what it often contains.
The earthworm used in vermiculture is usually Eisenia fetida (red wigglers) though other Eisenia species are sometimes used. All Eisenia are epigeic species meaning they live in the junction of decomposing organic matter (such as leaf litter, aging manure, rotted fallen trees) and their natural food is decaying plant matter and bacteria that are also digesting the organic matter. They don't make use of small dead animals (meat and fat).
In large scale commercial vermiculture operations, leftover and past-due-date foods from restaurants, institutions, nursing homes and schools are used along with plant matter and carboard and paper. I'm not sure how they balance cooked foods but possibly much less is used than plant matter.
The fact food is cooked isn't the problem but what's in it and/or what happens to it when added to the bin. If you have leftover vegetables and fruit that's been cooked with no added salt, it's perfectly acceptable. A certain amount of sweetened cooked fruit is also fine as the worms will eat that too. But ready-made foods usually have preservatives, salt, fats and spices added. Either worms won't eat it, leading to odour caused by mouldy rotten food, or it can make them unthrifty and even killing off your worms if it's fed them repeatedly.
The following is multiple choice question (with options) to answer.
What is the term for materials that have been left behind by organisms that once lived? | [
"skulls",
"bones",
"fossils",
"detritis"
] | C | Sediments are small fragments of rocks and minerals. Pebbles, sand, silt, and clay are examples of sediments. Sedimentary rocks may include fossils. Fossils are materials left behind by once-living organisms. Fossils can be pieces of the organism, like bones. They can also be traces of the organism, like footprints. |
SciQ | SciQ-4639 | zoology
Title: Are penguins plantigrade or digigrade? I'm trying to rig a 3D model of a penguin, but I don't know where to put the bones near the ankle because I can't tell if they're digigrade or plantigrade. Nearly all birds are digigrade, but penguins spend a lot of time walking and don't generally grasp or run with their talons. Plantigrade.
The penguins are highly specialized for their flightless aquatic
existence. The feet are located much farther back than those of other
birds, with the result that the bird carries itself mostly upright;
its walk can thus be described as plantigrade (i.e., on the soles).
The sole comprises the whole foot instead of just the toes, as in
other birds. The most notable characteristic of the group is the
transformation of the forelimb into a paddle. This is accompanied by a
body morphology particularly adapted to movement in a liquid medium.
The thoracic (rib) cage is well developed, and the sternum bears a
pronounced keel for the attachment of the pectoral muscles, which move
the flippers. The flipper has the same skeletal base as the wing of
flying birds but with its elements shortened and flattened, producing
a relatively rigid limb covered with very short feathers—an ideal
organ for rapid propulsion. The body plumage likewise consists of very
short feathers, which minimize friction and turbulence. The density of
the plumage and the layer of air that it retains provide almost
complete insulation of the body.
https://www.britannica.com/animal/penguin#ref3467
The following is multiple choice question (with options) to answer.
A penguin must do what before molting? | [
"use muscle mass",
"hibernate",
"mate",
"increase muscle mass"
] | D | |
SciQ | SciQ-4640 | marine-biology, vestigial
Title: Modern Whales with Vestigial legs Myth? Is it a myth that modern whales have been found with hind legs sticking out of their sides and full formed tibias, fibias, and toe bones? I keep finding assertions, but no citations. For example, the wikipedia page has no citation for it.
http://en.wikipedia.org/wiki/Whales#Appendages The link you give doesn't mention limbs sticking out of the body wall, but only vestigial hind limb elements. Many whales do retain pelves and femora, as this page at the Bergen Museum shows. Given the variation in limb development across vertebrates, it would not be surprising to find more distal elements (but I would be very surprised if they extended past the body wall).
The following is multiple choice question (with options) to answer.
The pelvic girdle, consisting of a hip bone, serves to attach a lower limb to this? | [
"cytoskeleton",
"exoskeleton",
"appendicular skeleton",
"axial skeleton"
] | D | 8.3 The Pelvic Girdle and Pelvis The pelvic girdle, consisting of a hip bone, serves to attach a lower limb to the axial skeleton. The hip bone articulates posteriorly at the sacroiliac joint with the sacrum, which is part of the axial skeleton. The right and left hip bones converge anteriorly and articulate with each other at the pubic symphysis. The combination of the hip bone, the sacrum, and the coccyx forms the pelvis. The pelvis has a pronounced anterior tilt. The primary function of the pelvis is to support the upper body and transfer body weight to the lower limbs. It also serves as the site of attachment for multiple muscles. The hip bone consists of three regions: the ilium, ischium, and pubis. The ilium forms the large, fan-like region of the hip bone. The superior margin of this area is the iliac crest. Located at either end of the iliac crest are the anterior superior and posterior superior iliac spines. Inferior to these are the anterior inferior and posterior inferior iliac spines. The auricular surface of the ilium articulates with the sacrum to form the sacroiliac joint. The medial surface of the upper ilium forms the iliac fossa, with the arcuate line marking the inferior limit of this area. The posterior margin of the ilium has the large greater sciatic notch. |
SciQ | SciQ-4641 | surface-tension
Title: What is the surface tension of liquids in space? I mean does surface tension exists in space on liquids?
Let's take an example if I have to write something using ballpen in space and space does not have gravity. Does it works because of the surface tension? Surface tension does exist "in space", which I take you to mean "without gravity". Surface tension in liquids is simply the attractive interactions between the molecules of a liquid. That exists whether there is gravity or not. I think most pens will not work well without being in the proper orientation in gravity, though. If you try using a normal ballpoint pen and write on a paper on the ceiling, you'll probably find that it won't work because gravity is pushing the ink in the wrong direction.
The following is multiple choice question (with options) to answer.
Why does water have a high surface tension? | [
"helium bonding",
"high freezing point",
"hydrogen bonding",
"oxygenation"
] | C | |
SciQ | SciQ-4642 | botany, homework, terminology, plant-anatomy, tissue
Interfascicular cambium differentiates from parenchyma or collenchyma cells located between the vascular bundles (mainly in stem)
The following is multiple choice question (with options) to answer.
What are the two types of vascular tissues found in vascular plants? | [
"xylem and phloem",
"cytoplasm and chloroplasm",
"xylem and chloroplasm",
"ectoderm and phloem"
] | A | Xylem and phloem are the two types of vascular tissues in vascular plants. |
SciQ | SciQ-4643 | neuroscience, neurophysiology, vision, human-eye, color
Title: What color does the other cone in Tetrachromacy correspond to? Human with normal vision possesses 3 cones, which correspond to blue (S), green (M) and red (L). What about tetrachromacy, where people have 4 cones in their retinae? What is the fourth cone exactly, and what color does that other cone correspond to? According to Deeb (2005), there are two relatively common types of causes for tetrachromacy in humans:
The common Ser180Ala polymorphism, which results in two spectrally different red pigments in the retina. This mutation also plays an important role in variation in normal color vision. This polymorphism most likely resulted from gene conversion by the green‐pigment gene.
Another common variation are several red/green pigment chimeras with different spectral properties. The red and green‐pigment genes are arranged in a head‐to‐tail tandem array on the X‐chromosome with one red‐pigment gene followed by one or more green‐pigment genes. The high homology between these genes has predisposed the locus to relatively common recombination events that give rise to red/green hybrids and deletions of green‐pigment genes. Such events constitute the most common cause of red‐green color vision defects. Only the first two pigment genes of the red/green array are expressed in the retina and therefore contribute to the color vision phenotype. The severity of red‐green color vision defects is inversely proportional to the difference between the wavelengths of maximal absorption of the photopigments encoded by the first two genes of the array. Women who are heterozygous for red and green pigment genes that encode three spectrally distinct photopigments have the potential for enhanced color vision.
Reference
Smeeb, Clin Gen (2005); 67:(5): 369-3
Further reading
- Color vision across species
The following is multiple choice question (with options) to answer.
What are the two types of photoreceptors in the retina? | [
"circles and cones",
"holes and cones",
"rods and cones",
"images and cones"
] | C | Which of the following statements about the human eye is false? a. Rods detect color, while cones detect only shades of gray. When light enters the retina, it passes the ganglion cells and bipolar cells before reaching photoreceptors at the rear of the eye. The iris adjusts the amount of light coming into the eye. The cornea is a protective layer on the front of the eye. The main function of the lens is to focus light on the retina and fovea centralis. The lens is dynamic, focusing and refocusing light as the eye rests on near and far objects in the visual field. The lens is operated by muscles that stretch it flat or allow it to thicken, changing the focal length of light coming through it to focus it sharply on the retina. With age comes the loss of the flexibility of the lens, and a form of farsightedness called presbyopia results. Presbyopia occurs because the image focuses behind the retina. Presbyopia is a deficit similar to a different type of farsightedness called hyperopia caused by an eyeball that is too short. For both defects, images in the distance are clear but images nearby are blurry. Myopia (nearsightedness) occurs when an eyeball is elongated and the image focus falls in front of the retina. In this case, images in the distance are blurry but images nearby are clear. There are two types of photoreceptors in the retina: rods and cones, named for their general appearance as illustrated in Figure 36.18. Rods are strongly photosensitive and are located in the outer edges of the retina. They detect dim light and are used primarily for peripheral and nighttime vision. Cones are weakly photosensitive and are located near the center of the retina. They respond to bright light, and their primary role is in daytime, color vision. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.